Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2 | * Memory merging support. |
| 3 | * |
| 4 | * This code enables dynamic sharing of identical pages found in different |
| 5 | * memory areas, even if they are not shared by fork() |
| 6 | * |
Izik Eidus | 36b2528 | 2009-09-21 17:02:06 -0700 | [diff] [blame] | 7 | * Copyright (C) 2008-2009 Red Hat, Inc. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 8 | * Authors: |
| 9 | * Izik Eidus |
| 10 | * Andrea Arcangeli |
| 11 | * Chris Wright |
Izik Eidus | 36b2528 | 2009-09-21 17:02:06 -0700 | [diff] [blame] | 12 | * Hugh Dickins |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 13 | * |
| 14 | * This work is licensed under the terms of the GNU GPL, version 2. |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 15 | */ |
| 16 | |
| 17 | #include <linux/errno.h> |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 18 | #include <linux/mm.h> |
| 19 | #include <linux/fs.h> |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 20 | #include <linux/mman.h> |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 21 | #include <linux/sched.h> |
Ingo Molnar | 6e84f31 | 2017-02-08 18:51:29 +0100 | [diff] [blame] | 22 | #include <linux/sched/mm.h> |
Ingo Molnar | f7ccbae | 2017-02-08 18:51:30 +0100 | [diff] [blame] | 23 | #include <linux/sched/coredump.h> |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 24 | #include <linux/rwsem.h> |
| 25 | #include <linux/pagemap.h> |
| 26 | #include <linux/rmap.h> |
| 27 | #include <linux/spinlock.h> |
| 28 | #include <linux/jhash.h> |
| 29 | #include <linux/delay.h> |
| 30 | #include <linux/kthread.h> |
| 31 | #include <linux/wait.h> |
| 32 | #include <linux/slab.h> |
| 33 | #include <linux/rbtree.h> |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 34 | #include <linux/memory.h> |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 35 | #include <linux/mmu_notifier.h> |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 36 | #include <linux/swap.h> |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 37 | #include <linux/ksm.h> |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 38 | #include <linux/hashtable.h> |
Andrea Arcangeli | 878aee7 | 2011-01-13 15:47:10 -0800 | [diff] [blame] | 39 | #include <linux/freezer.h> |
David Rientjes | 72788c3 | 2011-05-24 17:11:40 -0700 | [diff] [blame] | 40 | #include <linux/oom.h> |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 41 | #include <linux/numa.h> |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 42 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 43 | #include <asm/tlbflush.h> |
Hugh Dickins | 73848b4 | 2009-12-14 17:59:22 -0800 | [diff] [blame] | 44 | #include "internal.h" |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 45 | |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 46 | #ifdef CONFIG_NUMA |
| 47 | #define NUMA(x) (x) |
| 48 | #define DO_NUMA(x) do { (x); } while (0) |
| 49 | #else |
| 50 | #define NUMA(x) (0) |
| 51 | #define DO_NUMA(x) do { } while (0) |
| 52 | #endif |
| 53 | |
Mike Rapoport | 5a2ca3e | 2018-04-24 09:40:22 +0300 | [diff] [blame] | 54 | /** |
| 55 | * DOC: Overview |
| 56 | * |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 57 | * A few notes about the KSM scanning process, |
| 58 | * to make it easier to understand the data structures below: |
| 59 | * |
| 60 | * In order to reduce excessive scanning, KSM sorts the memory pages by their |
| 61 | * contents into a data structure that holds pointers to the pages' locations. |
| 62 | * |
| 63 | * Since the contents of the pages may change at any moment, KSM cannot just |
| 64 | * insert the pages into a normal sorted tree and expect it to find anything. |
| 65 | * Therefore KSM uses two data structures - the stable and the unstable tree. |
| 66 | * |
| 67 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted |
| 68 | * by their contents. Because each such page is write-protected, searching on |
| 69 | * this tree is fully assured to be working (except when pages are unmapped), |
| 70 | * and therefore this tree is called the stable tree. |
| 71 | * |
Mike Rapoport | 5a2ca3e | 2018-04-24 09:40:22 +0300 | [diff] [blame] | 72 | * The stable tree node includes information required for reverse |
| 73 | * mapping from a KSM page to virtual addresses that map this page. |
| 74 | * |
| 75 | * In order to avoid large latencies of the rmap walks on KSM pages, |
| 76 | * KSM maintains two types of nodes in the stable tree: |
| 77 | * |
| 78 | * * the regular nodes that keep the reverse mapping structures in a |
| 79 | * linked list |
| 80 | * * the "chains" that link nodes ("dups") that represent the same |
| 81 | * write protected memory content, but each "dup" corresponds to a |
| 82 | * different KSM page copy of that content |
| 83 | * |
| 84 | * Internally, the regular nodes, "dups" and "chains" are represented |
| 85 | * using the same :c:type:`struct stable_node` structure. |
| 86 | * |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 87 | * In addition to the stable tree, KSM uses a second data structure called the |
| 88 | * unstable tree: this tree holds pointers to pages which have been found to |
| 89 | * be "unchanged for a period of time". The unstable tree sorts these pages |
| 90 | * by their contents, but since they are not write-protected, KSM cannot rely |
| 91 | * upon the unstable tree to work correctly - the unstable tree is liable to |
| 92 | * be corrupted as its contents are modified, and so it is called unstable. |
| 93 | * |
| 94 | * KSM solves this problem by several techniques: |
| 95 | * |
| 96 | * 1) The unstable tree is flushed every time KSM completes scanning all |
| 97 | * memory areas, and then the tree is rebuilt again from the beginning. |
| 98 | * 2) KSM will only insert into the unstable tree, pages whose hash value |
| 99 | * has not changed since the previous scan of all memory areas. |
| 100 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the |
| 101 | * colors of the nodes and not on their contents, assuring that even when |
| 102 | * the tree gets "corrupted" it won't get out of balance, so scanning time |
| 103 | * remains the same (also, searching and inserting nodes in an rbtree uses |
| 104 | * the same algorithm, so we have no overhead when we flush and rebuild). |
| 105 | * 4) KSM never flushes the stable tree, which means that even if it were to |
| 106 | * take 10 attempts to find a page in the unstable tree, once it is found, |
| 107 | * it is secured in the stable tree. (When we scan a new page, we first |
| 108 | * compare it against the stable tree, and then against the unstable tree.) |
Hugh Dickins | 8fdb3db | 2013-02-22 16:36:03 -0800 | [diff] [blame] | 109 | * |
| 110 | * If the merge_across_nodes tunable is unset, then KSM maintains multiple |
| 111 | * stable trees and multiple unstable trees: one of each for each NUMA node. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 112 | */ |
| 113 | |
| 114 | /** |
| 115 | * struct mm_slot - ksm information per mm that is being scanned |
| 116 | * @link: link to the mm_slots hash list |
| 117 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 118 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 119 | * @mm: the mm that this information is valid for |
| 120 | */ |
| 121 | struct mm_slot { |
| 122 | struct hlist_node link; |
| 123 | struct list_head mm_list; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 124 | struct rmap_item *rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 125 | struct mm_struct *mm; |
| 126 | }; |
| 127 | |
| 128 | /** |
| 129 | * struct ksm_scan - cursor for scanning |
| 130 | * @mm_slot: the current mm_slot we are scanning |
| 131 | * @address: the next address inside that to be scanned |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 132 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 133 | * @seqnr: count of completed full scans (needed when removing unstable node) |
| 134 | * |
| 135 | * There is only the one ksm_scan instance of this cursor structure. |
| 136 | */ |
| 137 | struct ksm_scan { |
| 138 | struct mm_slot *mm_slot; |
| 139 | unsigned long address; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 140 | struct rmap_item **rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 141 | unsigned long seqnr; |
| 142 | }; |
| 143 | |
| 144 | /** |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 145 | * struct stable_node - node of the stable rbtree |
| 146 | * @node: rb node of this ksm page in the stable tree |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 147 | * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 148 | * @hlist_dup: linked into the stable_node->hlist with a stable_node chain |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 149 | * @list: linked into migrate_nodes, pending placement in the proper node tree |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 150 | * @hlist: hlist head of rmap_items using this ksm page |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 151 | * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 152 | * @chain_prune_time: time of the last full garbage collection |
| 153 | * @rmap_hlist_len: number of rmap_item entries in hlist or STABLE_NODE_CHAIN |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 154 | * @nid: NUMA node id of stable tree in which linked (may not match kpfn) |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 155 | */ |
| 156 | struct stable_node { |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 157 | union { |
| 158 | struct rb_node node; /* when node of stable tree */ |
| 159 | struct { /* when listed for migration */ |
| 160 | struct list_head *head; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 161 | struct { |
| 162 | struct hlist_node hlist_dup; |
| 163 | struct list_head list; |
| 164 | }; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 165 | }; |
| 166 | }; |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 167 | struct hlist_head hlist; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 168 | union { |
| 169 | unsigned long kpfn; |
| 170 | unsigned long chain_prune_time; |
| 171 | }; |
| 172 | /* |
| 173 | * STABLE_NODE_CHAIN can be any negative number in |
| 174 | * rmap_hlist_len negative range, but better not -1 to be able |
| 175 | * to reliably detect underflows. |
| 176 | */ |
| 177 | #define STABLE_NODE_CHAIN -1024 |
| 178 | int rmap_hlist_len; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 179 | #ifdef CONFIG_NUMA |
| 180 | int nid; |
| 181 | #endif |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 182 | }; |
| 183 | |
| 184 | /** |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 185 | * struct rmap_item - reverse mapping item for virtual addresses |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 186 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
Hugh Dickins | db114b8 | 2009-12-14 17:59:25 -0800 | [diff] [blame] | 187 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
Hugh Dickins | bc56620 | 2013-02-22 16:36:06 -0800 | [diff] [blame] | 188 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 189 | * @mm: the memory structure this rmap_item is pointing into |
| 190 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) |
| 191 | * @oldchecksum: previous checksum of the page at that virtual address |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 192 | * @node: rb node of this rmap_item in the unstable tree |
| 193 | * @head: pointer to stable_node heading this list in the stable tree |
| 194 | * @hlist: link into hlist of rmap_items hanging off that stable_node |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 195 | */ |
| 196 | struct rmap_item { |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 197 | struct rmap_item *rmap_list; |
Hugh Dickins | bc56620 | 2013-02-22 16:36:06 -0800 | [diff] [blame] | 198 | union { |
| 199 | struct anon_vma *anon_vma; /* when stable */ |
| 200 | #ifdef CONFIG_NUMA |
| 201 | int nid; /* when node of unstable tree */ |
| 202 | #endif |
| 203 | }; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 204 | struct mm_struct *mm; |
| 205 | unsigned long address; /* + low bits used for flags below */ |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 206 | unsigned int oldchecksum; /* when unstable */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 207 | union { |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 208 | struct rb_node node; /* when node of unstable tree */ |
| 209 | struct { /* when listed from stable tree */ |
| 210 | struct stable_node *head; |
| 211 | struct hlist_node hlist; |
| 212 | }; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 213 | }; |
| 214 | }; |
| 215 | |
| 216 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 217 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
| 218 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ |
Jia He | 1105a2f | 2018-06-14 15:26:14 -0700 | [diff] [blame] | 219 | #define KSM_FLAG_MASK (SEQNR_MASK|UNSTABLE_FLAG|STABLE_FLAG) |
| 220 | /* to mask all the flags */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 221 | |
| 222 | /* The stable and unstable tree heads */ |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 223 | static struct rb_root one_stable_tree[1] = { RB_ROOT }; |
| 224 | static struct rb_root one_unstable_tree[1] = { RB_ROOT }; |
| 225 | static struct rb_root *root_stable_tree = one_stable_tree; |
| 226 | static struct rb_root *root_unstable_tree = one_unstable_tree; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 227 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 228 | /* Recently migrated nodes of stable tree, pending proper placement */ |
| 229 | static LIST_HEAD(migrate_nodes); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 230 | #define STABLE_NODE_DUP_HEAD ((struct list_head *)&migrate_nodes.prev) |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 231 | |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 232 | #define MM_SLOTS_HASH_BITS 10 |
| 233 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 234 | |
| 235 | static struct mm_slot ksm_mm_head = { |
| 236 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), |
| 237 | }; |
| 238 | static struct ksm_scan ksm_scan = { |
| 239 | .mm_slot = &ksm_mm_head, |
| 240 | }; |
| 241 | |
| 242 | static struct kmem_cache *rmap_item_cache; |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 243 | static struct kmem_cache *stable_node_cache; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 244 | static struct kmem_cache *mm_slot_cache; |
| 245 | |
| 246 | /* The number of nodes in the stable tree */ |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 247 | static unsigned long ksm_pages_shared; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 248 | |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 249 | /* The number of page slots additionally sharing those nodes */ |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 250 | static unsigned long ksm_pages_sharing; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 251 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 252 | /* The number of nodes in the unstable tree */ |
| 253 | static unsigned long ksm_pages_unshared; |
| 254 | |
| 255 | /* The number of rmap_items in use: to calculate pages_volatile */ |
| 256 | static unsigned long ksm_rmap_items; |
| 257 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 258 | /* The number of stable_node chains */ |
| 259 | static unsigned long ksm_stable_node_chains; |
| 260 | |
| 261 | /* The number of stable_node dups linked to the stable_node chains */ |
| 262 | static unsigned long ksm_stable_node_dups; |
| 263 | |
| 264 | /* Delay in pruning stale stable_node_dups in the stable_node_chains */ |
| 265 | static int ksm_stable_node_chains_prune_millisecs = 2000; |
| 266 | |
| 267 | /* Maximum number of page slots sharing a stable node */ |
| 268 | static int ksm_max_page_sharing = 256; |
| 269 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 270 | /* Number of pages ksmd should scan in one batch */ |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 271 | static unsigned int ksm_thread_pages_to_scan = 100; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 272 | |
| 273 | /* Milliseconds ksmd should sleep between batches */ |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 274 | static unsigned int ksm_thread_sleep_millisecs = 20; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 275 | |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 276 | /* Checksum of an empty (zeroed) page */ |
| 277 | static unsigned int zero_checksum __read_mostly; |
| 278 | |
| 279 | /* Whether to merge empty (zeroed) pages with actual zero pages */ |
| 280 | static bool ksm_use_zero_pages __read_mostly; |
| 281 | |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 282 | #ifdef CONFIG_NUMA |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 283 | /* Zeroed when merging across nodes is not allowed */ |
| 284 | static unsigned int ksm_merge_across_nodes = 1; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 285 | static int ksm_nr_node_ids = 1; |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 286 | #else |
| 287 | #define ksm_merge_across_nodes 1U |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 288 | #define ksm_nr_node_ids 1 |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 289 | #endif |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 290 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 291 | #define KSM_RUN_STOP 0 |
| 292 | #define KSM_RUN_MERGE 1 |
| 293 | #define KSM_RUN_UNMERGE 2 |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 294 | #define KSM_RUN_OFFLINE 4 |
| 295 | static unsigned long ksm_run = KSM_RUN_STOP; |
| 296 | static void wait_while_offlining(void); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 297 | |
| 298 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); |
| 299 | static DEFINE_MUTEX(ksm_thread_mutex); |
| 300 | static DEFINE_SPINLOCK(ksm_mmlist_lock); |
| 301 | |
| 302 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ |
| 303 | sizeof(struct __struct), __alignof__(struct __struct),\ |
| 304 | (__flags), NULL) |
| 305 | |
| 306 | static int __init ksm_slab_init(void) |
| 307 | { |
| 308 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); |
| 309 | if (!rmap_item_cache) |
| 310 | goto out; |
| 311 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 312 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
| 313 | if (!stable_node_cache) |
| 314 | goto out_free1; |
| 315 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 316 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
| 317 | if (!mm_slot_cache) |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 318 | goto out_free2; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 319 | |
| 320 | return 0; |
| 321 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 322 | out_free2: |
| 323 | kmem_cache_destroy(stable_node_cache); |
| 324 | out_free1: |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 325 | kmem_cache_destroy(rmap_item_cache); |
| 326 | out: |
| 327 | return -ENOMEM; |
| 328 | } |
| 329 | |
| 330 | static void __init ksm_slab_free(void) |
| 331 | { |
| 332 | kmem_cache_destroy(mm_slot_cache); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 333 | kmem_cache_destroy(stable_node_cache); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 334 | kmem_cache_destroy(rmap_item_cache); |
| 335 | mm_slot_cache = NULL; |
| 336 | } |
| 337 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 338 | static __always_inline bool is_stable_node_chain(struct stable_node *chain) |
| 339 | { |
| 340 | return chain->rmap_hlist_len == STABLE_NODE_CHAIN; |
| 341 | } |
| 342 | |
| 343 | static __always_inline bool is_stable_node_dup(struct stable_node *dup) |
| 344 | { |
| 345 | return dup->head == STABLE_NODE_DUP_HEAD; |
| 346 | } |
| 347 | |
| 348 | static inline void stable_node_chain_add_dup(struct stable_node *dup, |
| 349 | struct stable_node *chain) |
| 350 | { |
| 351 | VM_BUG_ON(is_stable_node_dup(dup)); |
| 352 | dup->head = STABLE_NODE_DUP_HEAD; |
| 353 | VM_BUG_ON(!is_stable_node_chain(chain)); |
| 354 | hlist_add_head(&dup->hlist_dup, &chain->hlist); |
| 355 | ksm_stable_node_dups++; |
| 356 | } |
| 357 | |
| 358 | static inline void __stable_node_dup_del(struct stable_node *dup) |
| 359 | { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 360 | VM_BUG_ON(!is_stable_node_dup(dup)); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 361 | hlist_del(&dup->hlist_dup); |
| 362 | ksm_stable_node_dups--; |
| 363 | } |
| 364 | |
| 365 | static inline void stable_node_dup_del(struct stable_node *dup) |
| 366 | { |
| 367 | VM_BUG_ON(is_stable_node_chain(dup)); |
| 368 | if (is_stable_node_dup(dup)) |
| 369 | __stable_node_dup_del(dup); |
| 370 | else |
| 371 | rb_erase(&dup->node, root_stable_tree + NUMA(dup->nid)); |
| 372 | #ifdef CONFIG_DEBUG_VM |
| 373 | dup->head = NULL; |
| 374 | #endif |
| 375 | } |
| 376 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 377 | static inline struct rmap_item *alloc_rmap_item(void) |
| 378 | { |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 379 | struct rmap_item *rmap_item; |
| 380 | |
zhong jiang | 5b398e4 | 2016-09-28 15:22:30 -0700 | [diff] [blame] | 381 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | |
| 382 | __GFP_NORETRY | __GFP_NOWARN); |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 383 | if (rmap_item) |
| 384 | ksm_rmap_items++; |
| 385 | return rmap_item; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 386 | } |
| 387 | |
| 388 | static inline void free_rmap_item(struct rmap_item *rmap_item) |
| 389 | { |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 390 | ksm_rmap_items--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 391 | rmap_item->mm = NULL; /* debug safety */ |
| 392 | kmem_cache_free(rmap_item_cache, rmap_item); |
| 393 | } |
| 394 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 395 | static inline struct stable_node *alloc_stable_node(void) |
| 396 | { |
zhong jiang | 6213055 | 2016-10-07 17:01:19 -0700 | [diff] [blame] | 397 | /* |
| 398 | * The allocation can take too long with GFP_KERNEL when memory is under |
| 399 | * pressure, which may lead to hung task warnings. Adding __GFP_HIGH |
| 400 | * grants access to memory reserves, helping to avoid this problem. |
| 401 | */ |
| 402 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL | __GFP_HIGH); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 403 | } |
| 404 | |
| 405 | static inline void free_stable_node(struct stable_node *stable_node) |
| 406 | { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 407 | VM_BUG_ON(stable_node->rmap_hlist_len && |
| 408 | !is_stable_node_chain(stable_node)); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 409 | kmem_cache_free(stable_node_cache, stable_node); |
| 410 | } |
| 411 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 412 | static inline struct mm_slot *alloc_mm_slot(void) |
| 413 | { |
| 414 | if (!mm_slot_cache) /* initialization failed */ |
| 415 | return NULL; |
| 416 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); |
| 417 | } |
| 418 | |
| 419 | static inline void free_mm_slot(struct mm_slot *mm_slot) |
| 420 | { |
| 421 | kmem_cache_free(mm_slot_cache, mm_slot); |
| 422 | } |
| 423 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 424 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
| 425 | { |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 426 | struct mm_slot *slot; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 427 | |
Sasha Levin | b67bfe0 | 2013-02-27 17:06:00 -0800 | [diff] [blame] | 428 | hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm) |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 429 | if (slot->mm == mm) |
| 430 | return slot; |
| 431 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 432 | return NULL; |
| 433 | } |
| 434 | |
| 435 | static void insert_to_mm_slots_hash(struct mm_struct *mm, |
| 436 | struct mm_slot *mm_slot) |
| 437 | { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 438 | mm_slot->mm = mm; |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 439 | hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 440 | } |
| 441 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 442 | /* |
Hugh Dickins | a913e18 | 2009-09-21 17:02:26 -0700 | [diff] [blame] | 443 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's |
| 444 | * page tables after it has passed through ksm_exit() - which, if necessary, |
| 445 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set |
| 446 | * a special flag: they can just back out as soon as mm_users goes to zero. |
| 447 | * ksm_test_exit() is used throughout to make this test for exit: in some |
| 448 | * places for correctness, in some places just to avoid unnecessary work. |
| 449 | */ |
| 450 | static inline bool ksm_test_exit(struct mm_struct *mm) |
| 451 | { |
| 452 | return atomic_read(&mm->mm_users) == 0; |
| 453 | } |
| 454 | |
| 455 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 456 | * We use break_ksm to break COW on a ksm page: it's a stripped down |
| 457 | * |
Dave Hansen | d4edcf0 | 2016-02-12 13:01:56 -0800 | [diff] [blame] | 458 | * if (get_user_pages(addr, 1, 1, 1, &page, NULL) == 1) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 459 | * put_page(page); |
| 460 | * |
| 461 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, |
| 462 | * in case the application has unmapped and remapped mm,addr meanwhile. |
| 463 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP |
| 464 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. |
Dave Hansen | 1b2ee12 | 2016-02-12 13:02:21 -0800 | [diff] [blame] | 465 | * |
| 466 | * FAULT_FLAG/FOLL_REMOTE are because we do this outside the context |
| 467 | * of the process that owns 'vma'. We also do not want to enforce |
| 468 | * protection keys here anyway. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 469 | */ |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 470 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 471 | { |
| 472 | struct page *page; |
Souptick Joarder | 50a7ca3 | 2018-08-17 15:44:47 -0700 | [diff] [blame] | 473 | vm_fault_t ret = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 474 | |
| 475 | do { |
| 476 | cond_resched(); |
Dave Hansen | 1b2ee12 | 2016-02-12 13:02:21 -0800 | [diff] [blame] | 477 | page = follow_page(vma, addr, |
| 478 | FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); |
Dan Carpenter | 22eccdd | 2010-04-23 13:18:10 -0400 | [diff] [blame] | 479 | if (IS_ERR_OR_NULL(page)) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 480 | break; |
| 481 | if (PageKsm(page)) |
Kirill A. Shutemov | dcddffd | 2016-07-26 15:25:18 -0700 | [diff] [blame] | 482 | ret = handle_mm_fault(vma, addr, |
| 483 | FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 484 | else |
| 485 | ret = VM_FAULT_WRITE; |
| 486 | put_page(page); |
Linus Torvalds | 33692f2 | 2015-01-29 10:51:32 -0800 | [diff] [blame] | 487 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 488 | /* |
| 489 | * We must loop because handle_mm_fault() may back out if there's |
| 490 | * any difficulty e.g. if pte accessed bit gets updated concurrently. |
| 491 | * |
| 492 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that |
| 493 | * COW has been broken, even if the vma does not permit VM_WRITE; |
| 494 | * but note that a concurrent fault might break PageKsm for us. |
| 495 | * |
| 496 | * VM_FAULT_SIGBUS could occur if we race with truncation of the |
| 497 | * backing file, which also invalidates anonymous pages: that's |
| 498 | * okay, that truncation will have unmapped the PageKsm for us. |
| 499 | * |
| 500 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting |
| 501 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the |
| 502 | * current task has TIF_MEMDIE set, and will be OOM killed on return |
| 503 | * to user; and ksmd, having no mm, would never be chosen for that. |
| 504 | * |
| 505 | * But if the mm is in a limited mem_cgroup, then the fault may fail |
| 506 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and |
| 507 | * even ksmd can fail in this way - though it's usually breaking ksm |
| 508 | * just to undo a merge it made a moment before, so unlikely to oom. |
| 509 | * |
| 510 | * That's a pity: we might therefore have more kernel pages allocated |
| 511 | * than we're counting as nodes in the stable tree; but ksm_do_scan |
| 512 | * will retry to break_cow on each pass, so should recover the page |
| 513 | * in due course. The important thing is to not let VM_MERGEABLE |
| 514 | * be cleared while any such pages might remain in the area. |
| 515 | */ |
| 516 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 517 | } |
| 518 | |
Bob Liu | ef69422 | 2012-03-21 16:34:11 -0700 | [diff] [blame] | 519 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
| 520 | unsigned long addr) |
| 521 | { |
| 522 | struct vm_area_struct *vma; |
| 523 | if (ksm_test_exit(mm)) |
| 524 | return NULL; |
| 525 | vma = find_vma(mm, addr); |
| 526 | if (!vma || vma->vm_start > addr) |
| 527 | return NULL; |
| 528 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
| 529 | return NULL; |
| 530 | return vma; |
| 531 | } |
| 532 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 533 | static void break_cow(struct rmap_item *rmap_item) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 534 | { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 535 | struct mm_struct *mm = rmap_item->mm; |
| 536 | unsigned long addr = rmap_item->address; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 537 | struct vm_area_struct *vma; |
| 538 | |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 539 | /* |
| 540 | * It is not an accident that whenever we want to break COW |
| 541 | * to undo, we also need to drop a reference to the anon_vma. |
| 542 | */ |
Peter Zijlstra | 9e60109 | 2011-03-22 16:32:46 -0700 | [diff] [blame] | 543 | put_anon_vma(rmap_item->anon_vma); |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 544 | |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 545 | down_read(&mm->mmap_sem); |
Bob Liu | ef69422 | 2012-03-21 16:34:11 -0700 | [diff] [blame] | 546 | vma = find_mergeable_vma(mm, addr); |
| 547 | if (vma) |
| 548 | break_ksm(vma, addr); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 549 | up_read(&mm->mmap_sem); |
| 550 | } |
| 551 | |
| 552 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) |
| 553 | { |
| 554 | struct mm_struct *mm = rmap_item->mm; |
| 555 | unsigned long addr = rmap_item->address; |
| 556 | struct vm_area_struct *vma; |
| 557 | struct page *page; |
| 558 | |
| 559 | down_read(&mm->mmap_sem); |
Bob Liu | ef69422 | 2012-03-21 16:34:11 -0700 | [diff] [blame] | 560 | vma = find_mergeable_vma(mm, addr); |
| 561 | if (!vma) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 562 | goto out; |
| 563 | |
| 564 | page = follow_page(vma, addr, FOLL_GET); |
Dan Carpenter | 22eccdd | 2010-04-23 13:18:10 -0400 | [diff] [blame] | 565 | if (IS_ERR_OR_NULL(page)) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 566 | goto out; |
Kirill A. Shutemov | f765f54 | 2016-01-15 16:53:03 -0800 | [diff] [blame] | 567 | if (PageAnon(page)) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 568 | flush_anon_page(vma, page, addr); |
| 569 | flush_dcache_page(page); |
| 570 | } else { |
| 571 | put_page(page); |
Andrea Arcangeli | c8f95ed | 2015-11-05 18:49:19 -0800 | [diff] [blame] | 572 | out: |
| 573 | page = NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 574 | } |
| 575 | up_read(&mm->mmap_sem); |
| 576 | return page; |
| 577 | } |
| 578 | |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 579 | /* |
| 580 | * This helper is used for getting right index into array of tree roots. |
| 581 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for |
| 582 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, |
| 583 | * every node has its own stable and unstable tree. |
| 584 | */ |
| 585 | static inline int get_kpfn_nid(unsigned long kpfn) |
| 586 | { |
Hugh Dickins | d8fc16a | 2013-03-08 12:43:34 -0800 | [diff] [blame] | 587 | return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 588 | } |
| 589 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 590 | static struct stable_node *alloc_stable_node_chain(struct stable_node *dup, |
| 591 | struct rb_root *root) |
| 592 | { |
| 593 | struct stable_node *chain = alloc_stable_node(); |
| 594 | VM_BUG_ON(is_stable_node_chain(dup)); |
| 595 | if (likely(chain)) { |
| 596 | INIT_HLIST_HEAD(&chain->hlist); |
| 597 | chain->chain_prune_time = jiffies; |
| 598 | chain->rmap_hlist_len = STABLE_NODE_CHAIN; |
| 599 | #if defined (CONFIG_DEBUG_VM) && defined(CONFIG_NUMA) |
| 600 | chain->nid = -1; /* debug */ |
| 601 | #endif |
| 602 | ksm_stable_node_chains++; |
| 603 | |
| 604 | /* |
| 605 | * Put the stable node chain in the first dimension of |
| 606 | * the stable tree and at the same time remove the old |
| 607 | * stable node. |
| 608 | */ |
| 609 | rb_replace_node(&dup->node, &chain->node, root); |
| 610 | |
| 611 | /* |
| 612 | * Move the old stable node to the second dimension |
| 613 | * queued in the hlist_dup. The invariant is that all |
| 614 | * dup stable_nodes in the chain->hlist point to pages |
| 615 | * that are wrprotected and have the exact same |
| 616 | * content. |
| 617 | */ |
| 618 | stable_node_chain_add_dup(dup, chain); |
| 619 | } |
| 620 | return chain; |
| 621 | } |
| 622 | |
| 623 | static inline void free_stable_node_chain(struct stable_node *chain, |
| 624 | struct rb_root *root) |
| 625 | { |
| 626 | rb_erase(&chain->node, root); |
| 627 | free_stable_node(chain); |
| 628 | ksm_stable_node_chains--; |
| 629 | } |
| 630 | |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 631 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
| 632 | { |
| 633 | struct rmap_item *rmap_item; |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 634 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 635 | /* check it's not STABLE_NODE_CHAIN or negative */ |
| 636 | BUG_ON(stable_node->rmap_hlist_len < 0); |
| 637 | |
Sasha Levin | b67bfe0 | 2013-02-27 17:06:00 -0800 | [diff] [blame] | 638 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 639 | if (rmap_item->hlist.next) |
| 640 | ksm_pages_sharing--; |
| 641 | else |
| 642 | ksm_pages_shared--; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 643 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
| 644 | stable_node->rmap_hlist_len--; |
Peter Zijlstra | 9e60109 | 2011-03-22 16:32:46 -0700 | [diff] [blame] | 645 | put_anon_vma(rmap_item->anon_vma); |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 646 | rmap_item->address &= PAGE_MASK; |
| 647 | cond_resched(); |
| 648 | } |
| 649 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 650 | /* |
| 651 | * We need the second aligned pointer of the migrate_nodes |
| 652 | * list_head to stay clear from the rb_parent_color union |
| 653 | * (aligned and different than any node) and also different |
| 654 | * from &migrate_nodes. This will verify that future list.h changes |
Nick Desaulniers | 815f0dd | 2018-08-22 16:37:24 -0700 | [diff] [blame] | 655 | * don't break STABLE_NODE_DUP_HEAD. Only recent gcc can handle it. |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 656 | */ |
Nick Desaulniers | 815f0dd | 2018-08-22 16:37:24 -0700 | [diff] [blame] | 657 | #if defined(GCC_VERSION) && GCC_VERSION >= 40903 |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 658 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes); |
| 659 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1); |
| 660 | #endif |
| 661 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 662 | if (stable_node->head == &migrate_nodes) |
| 663 | list_del(&stable_node->list); |
| 664 | else |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 665 | stable_node_dup_del(stable_node); |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 666 | free_stable_node(stable_node); |
| 667 | } |
| 668 | |
| 669 | /* |
| 670 | * get_ksm_page: checks if the page indicated by the stable node |
| 671 | * is still its ksm page, despite having held no reference to it. |
| 672 | * In which case we can trust the content of the page, and it |
| 673 | * returns the gotten page; but if the page has now been zapped, |
| 674 | * remove the stale node from the stable tree and return NULL. |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 675 | * But beware, the stable node's page might be being migrated. |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 676 | * |
| 677 | * You would expect the stable_node to hold a reference to the ksm page. |
| 678 | * But if it increments the page's count, swapping out has to wait for |
| 679 | * ksmd to come around again before it can free the page, which may take |
| 680 | * seconds or even minutes: much too unresponsive. So instead we use a |
| 681 | * "keyhole reference": access to the ksm page from the stable node peeps |
| 682 | * out through its keyhole to see if that page still holds the right key, |
| 683 | * pointing back to this stable node. This relies on freeing a PageAnon |
| 684 | * page to reset its page->mapping to NULL, and relies on no other use of |
| 685 | * a page to put something that might look like our key in page->mapping. |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 686 | * is on its way to being freed; but it is an anomaly to bear in mind. |
| 687 | */ |
Hugh Dickins | 8fdb3db | 2013-02-22 16:36:03 -0800 | [diff] [blame] | 688 | static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 689 | { |
| 690 | struct page *page; |
| 691 | void *expected_mapping; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 692 | unsigned long kpfn; |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 693 | |
Minchan Kim | bda807d | 2016-07-26 15:23:05 -0700 | [diff] [blame] | 694 | expected_mapping = (void *)((unsigned long)stable_node | |
| 695 | PAGE_MAPPING_KSM); |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 696 | again: |
Paul E. McKenney | 08df477 | 2017-10-09 11:51:45 -0700 | [diff] [blame] | 697 | kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */ |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 698 | page = pfn_to_page(kpfn); |
Jason Low | 4db0c3c | 2015-04-15 16:14:08 -0700 | [diff] [blame] | 699 | if (READ_ONCE(page->mapping) != expected_mapping) |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 700 | goto stale; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 701 | |
| 702 | /* |
| 703 | * We cannot do anything with the page while its refcount is 0. |
| 704 | * Usually 0 means free, or tail of a higher-order page: in which |
| 705 | * case this node is no longer referenced, and should be freed; |
Jiang Biao | 1c4c3b9 | 2018-08-21 21:53:13 -0700 | [diff] [blame] | 706 | * however, it might mean that the page is under page_ref_freeze(). |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 707 | * The __remove_mapping() case is easy, again the node is now stale; |
| 708 | * but if page is swapcache in migrate_page_move_mapping(), it might |
| 709 | * still be our page, in which case it's essential to keep the node. |
| 710 | */ |
| 711 | while (!get_page_unless_zero(page)) { |
| 712 | /* |
| 713 | * Another check for page->mapping != expected_mapping would |
| 714 | * work here too. We have chosen the !PageSwapCache test to |
| 715 | * optimize the common case, when the page is or is about to |
| 716 | * be freed: PageSwapCache is cleared (under spin_lock_irq) |
Jiang Biao | 1c4c3b9 | 2018-08-21 21:53:13 -0700 | [diff] [blame] | 717 | * in the ref_freeze section of __remove_mapping(); but Anon |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 718 | * page->mapping reset to NULL later, in free_pages_prepare(). |
| 719 | */ |
| 720 | if (!PageSwapCache(page)) |
| 721 | goto stale; |
| 722 | cpu_relax(); |
| 723 | } |
| 724 | |
Jason Low | 4db0c3c | 2015-04-15 16:14:08 -0700 | [diff] [blame] | 725 | if (READ_ONCE(page->mapping) != expected_mapping) { |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 726 | put_page(page); |
| 727 | goto stale; |
| 728 | } |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 729 | |
Hugh Dickins | 8fdb3db | 2013-02-22 16:36:03 -0800 | [diff] [blame] | 730 | if (lock_it) { |
Hugh Dickins | 8aafa6a | 2013-02-22 16:35:06 -0800 | [diff] [blame] | 731 | lock_page(page); |
Jason Low | 4db0c3c | 2015-04-15 16:14:08 -0700 | [diff] [blame] | 732 | if (READ_ONCE(page->mapping) != expected_mapping) { |
Hugh Dickins | 8aafa6a | 2013-02-22 16:35:06 -0800 | [diff] [blame] | 733 | unlock_page(page); |
| 734 | put_page(page); |
| 735 | goto stale; |
| 736 | } |
| 737 | } |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 738 | return page; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 739 | |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 740 | stale: |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 741 | /* |
| 742 | * We come here from above when page->mapping or !PageSwapCache |
| 743 | * suggests that the node is stale; but it might be under migration. |
| 744 | * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), |
| 745 | * before checking whether node->kpfn has been changed. |
| 746 | */ |
| 747 | smp_rmb(); |
Jason Low | 4db0c3c | 2015-04-15 16:14:08 -0700 | [diff] [blame] | 748 | if (READ_ONCE(stable_node->kpfn) != kpfn) |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 749 | goto again; |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 750 | remove_node_from_stable_tree(stable_node); |
| 751 | return NULL; |
| 752 | } |
| 753 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 754 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 755 | * Removing rmap_item from stable or unstable tree. |
| 756 | * This function will clean the information from the stable/unstable tree. |
| 757 | */ |
| 758 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) |
| 759 | { |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 760 | if (rmap_item->address & STABLE_FLAG) { |
| 761 | struct stable_node *stable_node; |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 762 | struct page *page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 763 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 764 | stable_node = rmap_item->head; |
Hugh Dickins | 8aafa6a | 2013-02-22 16:35:06 -0800 | [diff] [blame] | 765 | page = get_ksm_page(stable_node, true); |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 766 | if (!page) |
| 767 | goto out; |
| 768 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 769 | hlist_del(&rmap_item->hlist); |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 770 | unlock_page(page); |
| 771 | put_page(page); |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 772 | |
Andrea Arcangeli | 98666f8a | 2015-11-05 18:49:13 -0800 | [diff] [blame] | 773 | if (!hlist_empty(&stable_node->hlist)) |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 774 | ksm_pages_sharing--; |
| 775 | else |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 776 | ksm_pages_shared--; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 777 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
| 778 | stable_node->rmap_hlist_len--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 779 | |
Peter Zijlstra | 9e60109 | 2011-03-22 16:32:46 -0700 | [diff] [blame] | 780 | put_anon_vma(rmap_item->anon_vma); |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 781 | rmap_item->address &= PAGE_MASK; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 782 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 783 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 784 | unsigned char age; |
| 785 | /* |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 786 | * Usually ksmd can and must skip the rb_erase, because |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 787 | * root_unstable_tree was already reset to RB_ROOT. |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 788 | * But be careful when an mm is exiting: do the rb_erase |
| 789 | * if this rmap_item was inserted by this scan, rather |
| 790 | * than left over from before. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 791 | */ |
| 792 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 793 | BUG_ON(age > 1); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 794 | if (!age) |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 795 | rb_erase(&rmap_item->node, |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 796 | root_unstable_tree + NUMA(rmap_item->nid)); |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 797 | ksm_pages_unshared--; |
| 798 | rmap_item->address &= PAGE_MASK; |
| 799 | } |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 800 | out: |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 801 | cond_resched(); /* we're called from many long loops */ |
| 802 | } |
| 803 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 804 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 805 | struct rmap_item **rmap_list) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 806 | { |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 807 | while (*rmap_list) { |
| 808 | struct rmap_item *rmap_item = *rmap_list; |
| 809 | *rmap_list = rmap_item->rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 810 | remove_rmap_item_from_tree(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 811 | free_rmap_item(rmap_item); |
| 812 | } |
| 813 | } |
| 814 | |
| 815 | /* |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 816 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 817 | * than check every pte of a given vma, the locking doesn't quite work for |
| 818 | * that - an rmap_item is assigned to the stable tree after inserting ksm |
| 819 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing |
| 820 | * rmap_items from parent to child at fork time (so as not to waste time |
| 821 | * if exit comes before the next scan reaches it). |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 822 | * |
| 823 | * Similarly, although we'd like to remove rmap_items (so updating counts |
| 824 | * and freeing memory) when unmerging an area, it's easier to leave that |
| 825 | * to the next pass of ksmd - consider, for example, how ksmd might be |
| 826 | * in cmp_and_merge_page on one of the rmap_items we would be removing. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 827 | */ |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 828 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
| 829 | unsigned long start, unsigned long end) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 830 | { |
| 831 | unsigned long addr; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 832 | int err = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 833 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 834 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 835 | if (ksm_test_exit(vma->vm_mm)) |
| 836 | break; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 837 | if (signal_pending(current)) |
| 838 | err = -ERESTARTSYS; |
| 839 | else |
| 840 | err = break_ksm(vma, addr); |
| 841 | } |
| 842 | return err; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 843 | } |
| 844 | |
Mike Rapoport | 8848482 | 2018-06-07 17:07:11 -0700 | [diff] [blame] | 845 | static inline struct stable_node *page_stable_node(struct page *page) |
| 846 | { |
| 847 | return PageKsm(page) ? page_rmapping(page) : NULL; |
| 848 | } |
| 849 | |
| 850 | static inline void set_page_stable_node(struct page *page, |
| 851 | struct stable_node *stable_node) |
| 852 | { |
| 853 | page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); |
| 854 | } |
| 855 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 856 | #ifdef CONFIG_SYSFS |
| 857 | /* |
| 858 | * Only called through the sysfs control interface: |
| 859 | */ |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 860 | static int remove_stable_node(struct stable_node *stable_node) |
| 861 | { |
| 862 | struct page *page; |
| 863 | int err; |
| 864 | |
| 865 | page = get_ksm_page(stable_node, true); |
| 866 | if (!page) { |
| 867 | /* |
| 868 | * get_ksm_page did remove_node_from_stable_tree itself. |
| 869 | */ |
| 870 | return 0; |
| 871 | } |
| 872 | |
Hugh Dickins | 8fdb3db | 2013-02-22 16:36:03 -0800 | [diff] [blame] | 873 | if (WARN_ON_ONCE(page_mapped(page))) { |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 874 | /* |
Hugh Dickins | 8fdb3db | 2013-02-22 16:36:03 -0800 | [diff] [blame] | 875 | * This should not happen: but if it does, just refuse to let |
| 876 | * merge_across_nodes be switched - there is no need to panic. |
| 877 | */ |
| 878 | err = -EBUSY; |
| 879 | } else { |
| 880 | /* |
| 881 | * The stable node did not yet appear stale to get_ksm_page(), |
| 882 | * since that allows for an unmapped ksm page to be recognized |
| 883 | * right up until it is freed; but the node is safe to remove. |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 884 | * This page might be in a pagevec waiting to be freed, |
| 885 | * or it might be PageSwapCache (perhaps under writeback), |
| 886 | * or it might have been removed from swapcache a moment ago. |
| 887 | */ |
| 888 | set_page_stable_node(page, NULL); |
| 889 | remove_node_from_stable_tree(stable_node); |
| 890 | err = 0; |
| 891 | } |
| 892 | |
| 893 | unlock_page(page); |
| 894 | put_page(page); |
| 895 | return err; |
| 896 | } |
| 897 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 898 | static int remove_stable_node_chain(struct stable_node *stable_node, |
| 899 | struct rb_root *root) |
| 900 | { |
| 901 | struct stable_node *dup; |
| 902 | struct hlist_node *hlist_safe; |
| 903 | |
| 904 | if (!is_stable_node_chain(stable_node)) { |
| 905 | VM_BUG_ON(is_stable_node_dup(stable_node)); |
| 906 | if (remove_stable_node(stable_node)) |
| 907 | return true; |
| 908 | else |
| 909 | return false; |
| 910 | } |
| 911 | |
| 912 | hlist_for_each_entry_safe(dup, hlist_safe, |
| 913 | &stable_node->hlist, hlist_dup) { |
| 914 | VM_BUG_ON(!is_stable_node_dup(dup)); |
| 915 | if (remove_stable_node(dup)) |
| 916 | return true; |
| 917 | } |
| 918 | BUG_ON(!hlist_empty(&stable_node->hlist)); |
| 919 | free_stable_node_chain(stable_node, root); |
| 920 | return false; |
| 921 | } |
| 922 | |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 923 | static int remove_all_stable_nodes(void) |
| 924 | { |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 925 | struct stable_node *stable_node, *next; |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 926 | int nid; |
| 927 | int err = 0; |
| 928 | |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 929 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 930 | while (root_stable_tree[nid].rb_node) { |
| 931 | stable_node = rb_entry(root_stable_tree[nid].rb_node, |
| 932 | struct stable_node, node); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 933 | if (remove_stable_node_chain(stable_node, |
| 934 | root_stable_tree + nid)) { |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 935 | err = -EBUSY; |
| 936 | break; /* proceed to next nid */ |
| 937 | } |
| 938 | cond_resched(); |
| 939 | } |
| 940 | } |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 941 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 942 | if (remove_stable_node(stable_node)) |
| 943 | err = -EBUSY; |
| 944 | cond_resched(); |
| 945 | } |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 946 | return err; |
| 947 | } |
| 948 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 949 | static int unmerge_and_remove_all_rmap_items(void) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 950 | { |
| 951 | struct mm_slot *mm_slot; |
| 952 | struct mm_struct *mm; |
| 953 | struct vm_area_struct *vma; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 954 | int err = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 955 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 956 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 957 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 958 | struct mm_slot, mm_list); |
| 959 | spin_unlock(&ksm_mmlist_lock); |
| 960 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 961 | for (mm_slot = ksm_scan.mm_slot; |
| 962 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 963 | mm = mm_slot->mm; |
| 964 | down_read(&mm->mmap_sem); |
| 965 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 966 | if (ksm_test_exit(mm)) |
| 967 | break; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 968 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
| 969 | continue; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 970 | err = unmerge_ksm_pages(vma, |
| 971 | vma->vm_start, vma->vm_end); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 972 | if (err) |
| 973 | goto error; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 974 | } |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 975 | |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 976 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
Zhou Chengming | 7496fea | 2016-05-12 15:42:21 -0700 | [diff] [blame] | 977 | up_read(&mm->mmap_sem); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 978 | |
| 979 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 980 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 981 | struct mm_slot, mm_list); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 982 | if (ksm_test_exit(mm)) { |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 983 | hash_del(&mm_slot->link); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 984 | list_del(&mm_slot->mm_list); |
| 985 | spin_unlock(&ksm_mmlist_lock); |
| 986 | |
| 987 | free_mm_slot(mm_slot); |
| 988 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 989 | mmdrop(mm); |
Zhou Chengming | 7496fea | 2016-05-12 15:42:21 -0700 | [diff] [blame] | 990 | } else |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 991 | spin_unlock(&ksm_mmlist_lock); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 992 | } |
| 993 | |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 994 | /* Clean up stable nodes, but don't worry if some are still busy */ |
| 995 | remove_all_stable_nodes(); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 996 | ksm_scan.seqnr = 0; |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 997 | return 0; |
| 998 | |
| 999 | error: |
| 1000 | up_read(&mm->mmap_sem); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1001 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1002 | ksm_scan.mm_slot = &ksm_mm_head; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1003 | spin_unlock(&ksm_mmlist_lock); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1004 | return err; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1005 | } |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1006 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1007 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1008 | static u32 calc_checksum(struct page *page) |
| 1009 | { |
| 1010 | u32 checksum; |
Cong Wang | 9b04c5f | 2011-11-25 23:14:39 +0800 | [diff] [blame] | 1011 | void *addr = kmap_atomic(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1012 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); |
Cong Wang | 9b04c5f | 2011-11-25 23:14:39 +0800 | [diff] [blame] | 1013 | kunmap_atomic(addr); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1014 | return checksum; |
| 1015 | } |
| 1016 | |
| 1017 | static int memcmp_pages(struct page *page1, struct page *page2) |
| 1018 | { |
| 1019 | char *addr1, *addr2; |
| 1020 | int ret; |
| 1021 | |
Cong Wang | 9b04c5f | 2011-11-25 23:14:39 +0800 | [diff] [blame] | 1022 | addr1 = kmap_atomic(page1); |
| 1023 | addr2 = kmap_atomic(page2); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1024 | ret = memcmp(addr1, addr2, PAGE_SIZE); |
Cong Wang | 9b04c5f | 2011-11-25 23:14:39 +0800 | [diff] [blame] | 1025 | kunmap_atomic(addr2); |
| 1026 | kunmap_atomic(addr1); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1027 | return ret; |
| 1028 | } |
| 1029 | |
| 1030 | static inline int pages_identical(struct page *page1, struct page *page2) |
| 1031 | { |
| 1032 | return !memcmp_pages(page1, page2); |
| 1033 | } |
| 1034 | |
| 1035 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, |
| 1036 | pte_t *orig_pte) |
| 1037 | { |
| 1038 | struct mm_struct *mm = vma->vm_mm; |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1039 | struct page_vma_mapped_walk pvmw = { |
| 1040 | .page = page, |
| 1041 | .vma = vma, |
| 1042 | }; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1043 | int swapped; |
| 1044 | int err = -EFAULT; |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1045 | unsigned long mmun_start; /* For mmu_notifiers */ |
| 1046 | unsigned long mmun_end; /* For mmu_notifiers */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1047 | |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1048 | pvmw.address = page_address_in_vma(page, vma); |
| 1049 | if (pvmw.address == -EFAULT) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1050 | goto out; |
| 1051 | |
Andrea Arcangeli | 29ad768 | 2011-01-13 15:47:19 -0800 | [diff] [blame] | 1052 | BUG_ON(PageTransCompound(page)); |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1053 | |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1054 | mmun_start = pvmw.address; |
| 1055 | mmun_end = pvmw.address + PAGE_SIZE; |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1056 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); |
| 1057 | |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1058 | if (!page_vma_mapped_walk(&pvmw)) |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1059 | goto out_mn; |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1060 | if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?")) |
| 1061 | goto out_unlock; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1062 | |
Aneesh Kumar K.V | 595cd8f | 2017-02-24 14:59:19 -0800 | [diff] [blame] | 1063 | if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) || |
Minchan Kim | b3a81d0 | 2017-08-10 15:24:15 -0700 | [diff] [blame] | 1064 | (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte)) || |
| 1065 | mm_tlb_flush_pending(mm)) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1066 | pte_t entry; |
| 1067 | |
| 1068 | swapped = PageSwapCache(page); |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1069 | flush_cache_page(vma, pvmw.address, page_to_pfn(page)); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1070 | /* |
Lucas De Marchi | 25985ed | 2011-03-30 22:57:33 -0300 | [diff] [blame] | 1071 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1072 | * take any lock, therefore the check that we are going to make |
| 1073 | * with the pagecount against the mapcount is racey and |
| 1074 | * O_DIRECT can happen right after the check. |
| 1075 | * So we clear the pte and flush the tlb before the check |
| 1076 | * this assure us that no O_DIRECT can happen after the check |
| 1077 | * or in the middle of the check. |
Jérôme Glisse | 0f10851 | 2017-11-15 17:34:07 -0800 | [diff] [blame] | 1078 | * |
| 1079 | * No need to notify as we are downgrading page table to read |
| 1080 | * only not changing it to point to a new page. |
| 1081 | * |
Mike Rapoport | ad56b73 | 2018-03-21 21:22:47 +0200 | [diff] [blame] | 1082 | * See Documentation/vm/mmu_notifier.rst |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1083 | */ |
Jérôme Glisse | 0f10851 | 2017-11-15 17:34:07 -0800 | [diff] [blame] | 1084 | entry = ptep_clear_flush(vma, pvmw.address, pvmw.pte); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1085 | /* |
| 1086 | * Check that no O_DIRECT or similar I/O is in progress on the |
| 1087 | * page |
| 1088 | */ |
Hugh Dickins | 31e855e | 2009-12-14 17:59:17 -0800 | [diff] [blame] | 1089 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1090 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1091 | goto out_unlock; |
| 1092 | } |
Hugh Dickins | 4e31635 | 2010-10-02 17:49:08 -0700 | [diff] [blame] | 1093 | if (pte_dirty(entry)) |
| 1094 | set_page_dirty(page); |
Aneesh Kumar K.V | 595cd8f | 2017-02-24 14:59:19 -0800 | [diff] [blame] | 1095 | |
| 1096 | if (pte_protnone(entry)) |
| 1097 | entry = pte_mkclean(pte_clear_savedwrite(entry)); |
| 1098 | else |
| 1099 | entry = pte_mkclean(pte_wrprotect(entry)); |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1100 | set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1101 | } |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1102 | *orig_pte = *pvmw.pte; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1103 | err = 0; |
| 1104 | |
| 1105 | out_unlock: |
Kirill A. Shutemov | 36eaff3 | 2017-02-24 14:58:04 -0800 | [diff] [blame] | 1106 | page_vma_mapped_walk_done(&pvmw); |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1107 | out_mn: |
| 1108 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1109 | out: |
| 1110 | return err; |
| 1111 | } |
| 1112 | |
| 1113 | /** |
| 1114 | * replace_page - replace page in vma by new ksm page |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1115 | * @vma: vma that holds the pte pointing to page |
| 1116 | * @page: the page we are replacing by kpage |
| 1117 | * @kpage: the ksm page we replace page by |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1118 | * @orig_pte: the original value of the pte |
| 1119 | * |
| 1120 | * Returns 0 on success, -EFAULT on failure. |
| 1121 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1122 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
| 1123 | struct page *kpage, pte_t orig_pte) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1124 | { |
| 1125 | struct mm_struct *mm = vma->vm_mm; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1126 | pmd_t *pmd; |
| 1127 | pte_t *ptep; |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 1128 | pte_t newpte; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1129 | spinlock_t *ptl; |
| 1130 | unsigned long addr; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1131 | int err = -EFAULT; |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1132 | unsigned long mmun_start; /* For mmu_notifiers */ |
| 1133 | unsigned long mmun_end; /* For mmu_notifiers */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1134 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1135 | addr = page_address_in_vma(page, vma); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1136 | if (addr == -EFAULT) |
| 1137 | goto out; |
| 1138 | |
Bob Liu | 6219049 | 2012-12-11 16:00:37 -0800 | [diff] [blame] | 1139 | pmd = mm_find_pmd(mm, addr); |
| 1140 | if (!pmd) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1141 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1142 | |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1143 | mmun_start = addr; |
| 1144 | mmun_end = addr + PAGE_SIZE; |
| 1145 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); |
| 1146 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1147 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
| 1148 | if (!pte_same(*ptep, orig_pte)) { |
| 1149 | pte_unmap_unlock(ptep, ptl); |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1150 | goto out_mn; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1151 | } |
| 1152 | |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 1153 | /* |
| 1154 | * No need to check ksm_use_zero_pages here: we can only have a |
| 1155 | * zero_page here if ksm_use_zero_pages was enabled alreaady. |
| 1156 | */ |
| 1157 | if (!is_zero_pfn(page_to_pfn(kpage))) { |
| 1158 | get_page(kpage); |
| 1159 | page_add_anon_rmap(kpage, vma, addr, false); |
| 1160 | newpte = mk_pte(kpage, vma->vm_page_prot); |
| 1161 | } else { |
| 1162 | newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), |
| 1163 | vma->vm_page_prot)); |
Claudio Imbrenda | a38c015 | 2018-04-10 16:29:41 -0700 | [diff] [blame] | 1164 | /* |
| 1165 | * We're replacing an anonymous page with a zero page, which is |
| 1166 | * not anonymous. We need to do proper accounting otherwise we |
| 1167 | * will get wrong values in /proc, and a BUG message in dmesg |
| 1168 | * when tearing down the mm. |
| 1169 | */ |
| 1170 | dec_mm_counter(mm, MM_ANONPAGES); |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 1171 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1172 | |
| 1173 | flush_cache_page(vma, addr, pte_pfn(*ptep)); |
Jérôme Glisse | 0f10851 | 2017-11-15 17:34:07 -0800 | [diff] [blame] | 1174 | /* |
| 1175 | * No need to notify as we are replacing a read only page with another |
| 1176 | * read only page with the same content. |
| 1177 | * |
Mike Rapoport | ad56b73 | 2018-03-21 21:22:47 +0200 | [diff] [blame] | 1178 | * See Documentation/vm/mmu_notifier.rst |
Jérôme Glisse | 0f10851 | 2017-11-15 17:34:07 -0800 | [diff] [blame] | 1179 | */ |
| 1180 | ptep_clear_flush(vma, addr, ptep); |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 1181 | set_pte_at_notify(mm, addr, ptep, newpte); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1182 | |
Kirill A. Shutemov | d281ee6 | 2016-01-15 16:52:16 -0800 | [diff] [blame] | 1183 | page_remove_rmap(page, false); |
Hugh Dickins | ae52a2a | 2011-01-13 15:46:28 -0800 | [diff] [blame] | 1184 | if (!page_mapped(page)) |
| 1185 | try_to_free_swap(page); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1186 | put_page(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1187 | |
| 1188 | pte_unmap_unlock(ptep, ptl); |
| 1189 | err = 0; |
Haggai Eran | 6bdb913 | 2012-10-08 16:33:35 -0700 | [diff] [blame] | 1190 | out_mn: |
| 1191 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1192 | out: |
| 1193 | return err; |
| 1194 | } |
| 1195 | |
| 1196 | /* |
| 1197 | * try_to_merge_one_page - take two pages and merge them into one |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1198 | * @vma: the vma that holds the pte pointing to page |
| 1199 | * @page: the PageAnon page that we want to replace with kpage |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1200 | * @kpage: the PageKsm page that we want to map instead of page, |
| 1201 | * or NULL the first time when we want to use page as kpage. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1202 | * |
| 1203 | * This function returns 0 if the pages were merged, -EFAULT otherwise. |
| 1204 | */ |
| 1205 | static int try_to_merge_one_page(struct vm_area_struct *vma, |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1206 | struct page *page, struct page *kpage) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1207 | { |
| 1208 | pte_t orig_pte = __pte(0); |
| 1209 | int err = -EFAULT; |
| 1210 | |
Hugh Dickins | db114b8 | 2009-12-14 17:59:25 -0800 | [diff] [blame] | 1211 | if (page == kpage) /* ksm page forked */ |
| 1212 | return 0; |
| 1213 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1214 | if (!PageAnon(page)) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1215 | goto out; |
| 1216 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1217 | /* |
| 1218 | * We need the page lock to read a stable PageSwapCache in |
| 1219 | * write_protect_page(). We use trylock_page() instead of |
| 1220 | * lock_page() because we don't want to wait here - we |
| 1221 | * prefer to continue scanning and merging different pages, |
| 1222 | * then come back to this page when it is unlocked. |
| 1223 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1224 | if (!trylock_page(page)) |
Hugh Dickins | 31e855e | 2009-12-14 17:59:17 -0800 | [diff] [blame] | 1225 | goto out; |
Kirill A. Shutemov | f765f54 | 2016-01-15 16:53:03 -0800 | [diff] [blame] | 1226 | |
| 1227 | if (PageTransCompound(page)) { |
Andrea Arcangeli | a7306c3 | 2017-06-02 14:46:11 -0700 | [diff] [blame] | 1228 | if (split_huge_page(page)) |
Kirill A. Shutemov | f765f54 | 2016-01-15 16:53:03 -0800 | [diff] [blame] | 1229 | goto out_unlock; |
| 1230 | } |
| 1231 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1232 | /* |
| 1233 | * If this anonymous page is mapped only here, its pte may need |
| 1234 | * to be write-protected. If it's mapped elsewhere, all of its |
| 1235 | * ptes are necessarily already write-protected. But in either |
| 1236 | * case, we need to lock and check page_count is not raised. |
| 1237 | */ |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1238 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
| 1239 | if (!kpage) { |
| 1240 | /* |
| 1241 | * While we hold page lock, upgrade page from |
| 1242 | * PageAnon+anon_vma to PageKsm+NULL stable_node: |
| 1243 | * stable_tree_insert() will update stable_node. |
| 1244 | */ |
| 1245 | set_page_stable_node(page, NULL); |
| 1246 | mark_page_accessed(page); |
Minchan Kim | 337ed7e | 2016-01-15 16:55:15 -0800 | [diff] [blame] | 1247 | /* |
| 1248 | * Page reclaim just frees a clean page with no dirty |
| 1249 | * ptes: make sure that the ksm page would be swapped. |
| 1250 | */ |
| 1251 | if (!PageDirty(page)) |
| 1252 | SetPageDirty(page); |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1253 | err = 0; |
| 1254 | } else if (pages_identical(page, kpage)) |
| 1255 | err = replace_page(vma, page, kpage, orig_pte); |
| 1256 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1257 | |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1258 | if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { |
Hugh Dickins | 73848b4 | 2009-12-14 17:59:22 -0800 | [diff] [blame] | 1259 | munlock_vma_page(page); |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 1260 | if (!PageMlocked(kpage)) { |
| 1261 | unlock_page(page); |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 1262 | lock_page(kpage); |
| 1263 | mlock_vma_page(kpage); |
| 1264 | page = kpage; /* for final unlock */ |
| 1265 | } |
| 1266 | } |
Hugh Dickins | 73848b4 | 2009-12-14 17:59:22 -0800 | [diff] [blame] | 1267 | |
Kirill A. Shutemov | f765f54 | 2016-01-15 16:53:03 -0800 | [diff] [blame] | 1268 | out_unlock: |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1269 | unlock_page(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1270 | out: |
| 1271 | return err; |
| 1272 | } |
| 1273 | |
| 1274 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1275 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, |
| 1276 | * but no new kernel page is allocated: kpage must already be a ksm page. |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1277 | * |
| 1278 | * This function returns 0 if the pages were merged, -EFAULT otherwise. |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1279 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1280 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
| 1281 | struct page *page, struct page *kpage) |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1282 | { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1283 | struct mm_struct *mm = rmap_item->mm; |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1284 | struct vm_area_struct *vma; |
| 1285 | int err = -EFAULT; |
| 1286 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1287 | down_read(&mm->mmap_sem); |
Andrea Arcangeli | 85c6e8d | 2015-11-05 18:49:16 -0800 | [diff] [blame] | 1288 | vma = find_mergeable_vma(mm, rmap_item->address); |
| 1289 | if (!vma) |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1290 | goto out; |
| 1291 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1292 | err = try_to_merge_one_page(vma, page, kpage); |
Hugh Dickins | db114b8 | 2009-12-14 17:59:25 -0800 | [diff] [blame] | 1293 | if (err) |
| 1294 | goto out; |
| 1295 | |
Hugh Dickins | bc56620 | 2013-02-22 16:36:06 -0800 | [diff] [blame] | 1296 | /* Unstable nid is in union with stable anon_vma: remove first */ |
| 1297 | remove_rmap_item_from_tree(rmap_item); |
| 1298 | |
Hugh Dickins | db114b8 | 2009-12-14 17:59:25 -0800 | [diff] [blame] | 1299 | /* Must get reference to anon_vma while still holding mmap_sem */ |
Peter Zijlstra | 9e60109 | 2011-03-22 16:32:46 -0700 | [diff] [blame] | 1300 | rmap_item->anon_vma = vma->anon_vma; |
| 1301 | get_anon_vma(vma->anon_vma); |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1302 | out: |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1303 | up_read(&mm->mmap_sem); |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1304 | return err; |
| 1305 | } |
| 1306 | |
| 1307 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1308 | * try_to_merge_two_pages - take two identical pages and prepare them |
| 1309 | * to be merged into one page. |
| 1310 | * |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1311 | * This function returns the kpage if we successfully merged two identical |
| 1312 | * pages into one ksm page, NULL otherwise. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1313 | * |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1314 | * Note that this function upgrades page to ksm page: if one of the pages |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1315 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
| 1316 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1317 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
| 1318 | struct page *page, |
| 1319 | struct rmap_item *tree_rmap_item, |
| 1320 | struct page *tree_page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1321 | { |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1322 | int err; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1323 | |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1324 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1325 | if (!err) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1326 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1327 | tree_page, page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1328 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1329 | * If that fails, we have a ksm page with only one pte |
| 1330 | * pointing to it: so break it. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1331 | */ |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 1332 | if (err) |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1333 | break_cow(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1334 | } |
Hugh Dickins | 80e14822 | 2009-12-14 17:59:29 -0800 | [diff] [blame] | 1335 | return err ? NULL : page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1336 | } |
| 1337 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1338 | static __always_inline |
| 1339 | bool __is_page_sharing_candidate(struct stable_node *stable_node, int offset) |
| 1340 | { |
| 1341 | VM_BUG_ON(stable_node->rmap_hlist_len < 0); |
| 1342 | /* |
| 1343 | * Check that at least one mapping still exists, otherwise |
| 1344 | * there's no much point to merge and share with this |
| 1345 | * stable_node, as the underlying tree_page of the other |
| 1346 | * sharer is going to be freed soon. |
| 1347 | */ |
| 1348 | return stable_node->rmap_hlist_len && |
| 1349 | stable_node->rmap_hlist_len + offset < ksm_max_page_sharing; |
| 1350 | } |
| 1351 | |
| 1352 | static __always_inline |
| 1353 | bool is_page_sharing_candidate(struct stable_node *stable_node) |
| 1354 | { |
| 1355 | return __is_page_sharing_candidate(stable_node, 0); |
| 1356 | } |
| 1357 | |
Colin Ian King | c01f0b5 | 2018-04-05 16:22:01 -0700 | [diff] [blame] | 1358 | static struct page *stable_node_dup(struct stable_node **_stable_node_dup, |
| 1359 | struct stable_node **_stable_node, |
| 1360 | struct rb_root *root, |
| 1361 | bool prune_stale_stable_nodes) |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1362 | { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1363 | struct stable_node *dup, *found = NULL, *stable_node = *_stable_node; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1364 | struct hlist_node *hlist_safe; |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1365 | struct page *_tree_page, *tree_page = NULL; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1366 | int nr = 0; |
| 1367 | int found_rmap_hlist_len; |
| 1368 | |
| 1369 | if (!prune_stale_stable_nodes || |
| 1370 | time_before(jiffies, stable_node->chain_prune_time + |
| 1371 | msecs_to_jiffies( |
| 1372 | ksm_stable_node_chains_prune_millisecs))) |
| 1373 | prune_stale_stable_nodes = false; |
| 1374 | else |
| 1375 | stable_node->chain_prune_time = jiffies; |
| 1376 | |
| 1377 | hlist_for_each_entry_safe(dup, hlist_safe, |
| 1378 | &stable_node->hlist, hlist_dup) { |
| 1379 | cond_resched(); |
| 1380 | /* |
| 1381 | * We must walk all stable_node_dup to prune the stale |
| 1382 | * stable nodes during lookup. |
| 1383 | * |
| 1384 | * get_ksm_page can drop the nodes from the |
| 1385 | * stable_node->hlist if they point to freed pages |
| 1386 | * (that's why we do a _safe walk). The "dup" |
| 1387 | * stable_node parameter itself will be freed from |
| 1388 | * under us if it returns NULL. |
| 1389 | */ |
| 1390 | _tree_page = get_ksm_page(dup, false); |
| 1391 | if (!_tree_page) |
| 1392 | continue; |
| 1393 | nr += 1; |
| 1394 | if (is_page_sharing_candidate(dup)) { |
| 1395 | if (!found || |
| 1396 | dup->rmap_hlist_len > found_rmap_hlist_len) { |
| 1397 | if (found) |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1398 | put_page(tree_page); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1399 | found = dup; |
| 1400 | found_rmap_hlist_len = found->rmap_hlist_len; |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1401 | tree_page = _tree_page; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1402 | |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1403 | /* skip put_page for found dup */ |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1404 | if (!prune_stale_stable_nodes) |
| 1405 | break; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1406 | continue; |
| 1407 | } |
| 1408 | } |
| 1409 | put_page(_tree_page); |
| 1410 | } |
| 1411 | |
Andrea Arcangeli | 80b18df | 2017-07-06 15:37:08 -0700 | [diff] [blame] | 1412 | if (found) { |
| 1413 | /* |
| 1414 | * nr is counting all dups in the chain only if |
| 1415 | * prune_stale_stable_nodes is true, otherwise we may |
| 1416 | * break the loop at nr == 1 even if there are |
| 1417 | * multiple entries. |
| 1418 | */ |
| 1419 | if (prune_stale_stable_nodes && nr == 1) { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1420 | /* |
| 1421 | * If there's not just one entry it would |
| 1422 | * corrupt memory, better BUG_ON. In KSM |
| 1423 | * context with no lock held it's not even |
| 1424 | * fatal. |
| 1425 | */ |
| 1426 | BUG_ON(stable_node->hlist.first->next); |
| 1427 | |
| 1428 | /* |
| 1429 | * There's just one entry and it is below the |
| 1430 | * deduplication limit so drop the chain. |
| 1431 | */ |
| 1432 | rb_replace_node(&stable_node->node, &found->node, |
| 1433 | root); |
| 1434 | free_stable_node(stable_node); |
| 1435 | ksm_stable_node_chains--; |
| 1436 | ksm_stable_node_dups--; |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1437 | /* |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1438 | * NOTE: the caller depends on the stable_node |
| 1439 | * to be equal to stable_node_dup if the chain |
| 1440 | * was collapsed. |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1441 | */ |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1442 | *_stable_node = found; |
| 1443 | /* |
| 1444 | * Just for robustneess as stable_node is |
| 1445 | * otherwise left as a stable pointer, the |
| 1446 | * compiler shall optimize it away at build |
| 1447 | * time. |
| 1448 | */ |
| 1449 | stable_node = NULL; |
Andrea Arcangeli | 80b18df | 2017-07-06 15:37:08 -0700 | [diff] [blame] | 1450 | } else if (stable_node->hlist.first != &found->hlist_dup && |
| 1451 | __is_page_sharing_candidate(found, 1)) { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1452 | /* |
Andrea Arcangeli | 80b18df | 2017-07-06 15:37:08 -0700 | [diff] [blame] | 1453 | * If the found stable_node dup can accept one |
| 1454 | * more future merge (in addition to the one |
| 1455 | * that is underway) and is not at the head of |
| 1456 | * the chain, put it there so next search will |
| 1457 | * be quicker in the !prune_stale_stable_nodes |
| 1458 | * case. |
| 1459 | * |
| 1460 | * NOTE: it would be inaccurate to use nr > 1 |
| 1461 | * instead of checking the hlist.first pointer |
| 1462 | * directly, because in the |
| 1463 | * prune_stale_stable_nodes case "nr" isn't |
| 1464 | * the position of the found dup in the chain, |
| 1465 | * but the total number of dups in the chain. |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1466 | */ |
| 1467 | hlist_del(&found->hlist_dup); |
| 1468 | hlist_add_head(&found->hlist_dup, |
| 1469 | &stable_node->hlist); |
| 1470 | } |
| 1471 | } |
| 1472 | |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1473 | *_stable_node_dup = found; |
| 1474 | return tree_page; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1475 | } |
| 1476 | |
| 1477 | static struct stable_node *stable_node_dup_any(struct stable_node *stable_node, |
| 1478 | struct rb_root *root) |
| 1479 | { |
| 1480 | if (!is_stable_node_chain(stable_node)) |
| 1481 | return stable_node; |
| 1482 | if (hlist_empty(&stable_node->hlist)) { |
| 1483 | free_stable_node_chain(stable_node, root); |
| 1484 | return NULL; |
| 1485 | } |
| 1486 | return hlist_entry(stable_node->hlist.first, |
| 1487 | typeof(*stable_node), hlist_dup); |
| 1488 | } |
| 1489 | |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1490 | /* |
| 1491 | * Like for get_ksm_page, this function can free the *_stable_node and |
| 1492 | * *_stable_node_dup if the returned tree_page is NULL. |
| 1493 | * |
| 1494 | * It can also free and overwrite *_stable_node with the found |
| 1495 | * stable_node_dup if the chain is collapsed (in which case |
| 1496 | * *_stable_node will be equal to *_stable_node_dup like if the chain |
| 1497 | * never existed). It's up to the caller to verify tree_page is not |
| 1498 | * NULL before dereferencing *_stable_node or *_stable_node_dup. |
| 1499 | * |
| 1500 | * *_stable_node_dup is really a second output parameter of this |
| 1501 | * function and will be overwritten in all cases, the caller doesn't |
| 1502 | * need to initialize it. |
| 1503 | */ |
| 1504 | static struct page *__stable_node_chain(struct stable_node **_stable_node_dup, |
| 1505 | struct stable_node **_stable_node, |
| 1506 | struct rb_root *root, |
| 1507 | bool prune_stale_stable_nodes) |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1508 | { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1509 | struct stable_node *stable_node = *_stable_node; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1510 | if (!is_stable_node_chain(stable_node)) { |
| 1511 | if (is_page_sharing_candidate(stable_node)) { |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1512 | *_stable_node_dup = stable_node; |
| 1513 | return get_ksm_page(stable_node, false); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1514 | } |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1515 | /* |
| 1516 | * _stable_node_dup set to NULL means the stable_node |
| 1517 | * reached the ksm_max_page_sharing limit. |
| 1518 | */ |
| 1519 | *_stable_node_dup = NULL; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1520 | return NULL; |
| 1521 | } |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1522 | return stable_node_dup(_stable_node_dup, _stable_node, root, |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1523 | prune_stale_stable_nodes); |
| 1524 | } |
| 1525 | |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1526 | static __always_inline struct page *chain_prune(struct stable_node **s_n_d, |
| 1527 | struct stable_node **s_n, |
| 1528 | struct rb_root *root) |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1529 | { |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1530 | return __stable_node_chain(s_n_d, s_n, root, true); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1531 | } |
| 1532 | |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1533 | static __always_inline struct page *chain(struct stable_node **s_n_d, |
| 1534 | struct stable_node *s_n, |
| 1535 | struct rb_root *root) |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1536 | { |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1537 | struct stable_node *old_stable_node = s_n; |
| 1538 | struct page *tree_page; |
| 1539 | |
| 1540 | tree_page = __stable_node_chain(s_n_d, &s_n, root, false); |
| 1541 | /* not pruning dups so s_n cannot have changed */ |
| 1542 | VM_BUG_ON(s_n != old_stable_node); |
| 1543 | return tree_page; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1544 | } |
| 1545 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1546 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1547 | * stable_tree_search - search for page inside the stable tree |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1548 | * |
| 1549 | * This function checks if there is a page inside the stable tree |
| 1550 | * with identical content to the page that we are scanning right now. |
| 1551 | * |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1552 | * This function returns the stable tree node of identical content if found, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1553 | * NULL otherwise. |
| 1554 | */ |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 1555 | static struct page *stable_tree_search(struct page *page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1556 | { |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1557 | int nid; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1558 | struct rb_root *root; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1559 | struct rb_node **new; |
| 1560 | struct rb_node *parent; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1561 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1562 | struct stable_node *page_node; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1563 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1564 | page_node = page_stable_node(page); |
| 1565 | if (page_node && page_node->head != &migrate_nodes) { |
| 1566 | /* ksm page forked */ |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 1567 | get_page(page); |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 1568 | return page; |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 1569 | } |
| 1570 | |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1571 | nid = get_kpfn_nid(page_to_pfn(page)); |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1572 | root = root_stable_tree + nid; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1573 | again: |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1574 | new = &root->rb_node; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1575 | parent = NULL; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1576 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1577 | while (*new) { |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 1578 | struct page *tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1579 | int ret; |
| 1580 | |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 1581 | cond_resched(); |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1582 | stable_node = rb_entry(*new, struct stable_node, node); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1583 | stable_node_any = NULL; |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1584 | tree_page = chain_prune(&stable_node_dup, &stable_node, root); |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1585 | /* |
| 1586 | * NOTE: stable_node may have been freed by |
| 1587 | * chain_prune() if the returned stable_node_dup is |
| 1588 | * not NULL. stable_node_dup may have been inserted in |
| 1589 | * the rbtree instead as a regular stable_node (in |
| 1590 | * order to collapse the stable_node chain if a single |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1591 | * stable_node dup was found in it). In such case the |
| 1592 | * stable_node is overwritten by the calleee to point |
| 1593 | * to the stable_node_dup that was collapsed in the |
| 1594 | * stable rbtree and stable_node will be equal to |
| 1595 | * stable_node_dup like if the chain never existed. |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1596 | */ |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1597 | if (!stable_node_dup) { |
| 1598 | /* |
| 1599 | * Either all stable_node dups were full in |
| 1600 | * this stable_node chain, or this chain was |
| 1601 | * empty and should be rb_erased. |
| 1602 | */ |
| 1603 | stable_node_any = stable_node_dup_any(stable_node, |
| 1604 | root); |
| 1605 | if (!stable_node_any) { |
| 1606 | /* rb_erase just run */ |
| 1607 | goto again; |
| 1608 | } |
| 1609 | /* |
| 1610 | * Take any of the stable_node dups page of |
| 1611 | * this stable_node chain to let the tree walk |
| 1612 | * continue. All KSM pages belonging to the |
| 1613 | * stable_node dups in a stable_node chain |
| 1614 | * have the same content and they're |
| 1615 | * wrprotected at all times. Any will work |
| 1616 | * fine to continue the walk. |
| 1617 | */ |
| 1618 | tree_page = get_ksm_page(stable_node_any, false); |
| 1619 | } |
| 1620 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); |
Andrea Arcangeli | f2e5ff8 | 2015-11-05 18:49:10 -0800 | [diff] [blame] | 1621 | if (!tree_page) { |
| 1622 | /* |
| 1623 | * If we walked over a stale stable_node, |
| 1624 | * get_ksm_page() will call rb_erase() and it |
| 1625 | * may rebalance the tree from under us. So |
| 1626 | * restart the search from scratch. Returning |
| 1627 | * NULL would be safe too, but we'd generate |
| 1628 | * false negative insertions just because some |
| 1629 | * stable_node was stale. |
| 1630 | */ |
| 1631 | goto again; |
| 1632 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1633 | |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 1634 | ret = memcmp_pages(page, tree_page); |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1635 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1636 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1637 | parent = *new; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1638 | if (ret < 0) |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1639 | new = &parent->rb_left; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1640 | else if (ret > 0) |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1641 | new = &parent->rb_right; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1642 | else { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1643 | if (page_node) { |
| 1644 | VM_BUG_ON(page_node->head != &migrate_nodes); |
| 1645 | /* |
| 1646 | * Test if the migrated page should be merged |
| 1647 | * into a stable node dup. If the mapcount is |
| 1648 | * 1 we can migrate it with another KSM page |
| 1649 | * without adding it to the chain. |
| 1650 | */ |
| 1651 | if (page_mapcount(page) > 1) |
| 1652 | goto chain_append; |
| 1653 | } |
| 1654 | |
| 1655 | if (!stable_node_dup) { |
| 1656 | /* |
| 1657 | * If the stable_node is a chain and |
| 1658 | * we got a payload match in memcmp |
| 1659 | * but we cannot merge the scanned |
| 1660 | * page in any of the existing |
| 1661 | * stable_node dups because they're |
| 1662 | * all full, we need to wait the |
| 1663 | * scanned page to find itself a match |
| 1664 | * in the unstable tree to create a |
| 1665 | * brand new KSM page to add later to |
| 1666 | * the dups of this stable_node. |
| 1667 | */ |
| 1668 | return NULL; |
| 1669 | } |
| 1670 | |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1671 | /* |
| 1672 | * Lock and unlock the stable_node's page (which |
| 1673 | * might already have been migrated) so that page |
| 1674 | * migration is sure to notice its raised count. |
| 1675 | * It would be more elegant to return stable_node |
| 1676 | * than kpage, but that involves more changes. |
| 1677 | */ |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1678 | tree_page = get_ksm_page(stable_node_dup, true); |
| 1679 | if (unlikely(!tree_page)) |
| 1680 | /* |
| 1681 | * The tree may have been rebalanced, |
| 1682 | * so re-evaluate parent and new. |
| 1683 | */ |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1684 | goto again; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1685 | unlock_page(tree_page); |
| 1686 | |
| 1687 | if (get_kpfn_nid(stable_node_dup->kpfn) != |
| 1688 | NUMA(stable_node_dup->nid)) { |
| 1689 | put_page(tree_page); |
| 1690 | goto replace; |
| 1691 | } |
| 1692 | return tree_page; |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 1693 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1694 | } |
| 1695 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1696 | if (!page_node) |
| 1697 | return NULL; |
| 1698 | |
| 1699 | list_del(&page_node->list); |
| 1700 | DO_NUMA(page_node->nid = nid); |
| 1701 | rb_link_node(&page_node->node, parent, new); |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1702 | rb_insert_color(&page_node->node, root); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1703 | out: |
| 1704 | if (is_page_sharing_candidate(page_node)) { |
| 1705 | get_page(page); |
| 1706 | return page; |
| 1707 | } else |
| 1708 | return NULL; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1709 | |
| 1710 | replace: |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1711 | /* |
| 1712 | * If stable_node was a chain and chain_prune collapsed it, |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1713 | * stable_node has been updated to be the new regular |
| 1714 | * stable_node. A collapse of the chain is indistinguishable |
| 1715 | * from the case there was no chain in the stable |
| 1716 | * rbtree. Otherwise stable_node is the chain and |
| 1717 | * stable_node_dup is the dup to replace. |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1718 | */ |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1719 | if (stable_node_dup == stable_node) { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1720 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
| 1721 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1722 | /* there is no chain */ |
| 1723 | if (page_node) { |
| 1724 | VM_BUG_ON(page_node->head != &migrate_nodes); |
| 1725 | list_del(&page_node->list); |
| 1726 | DO_NUMA(page_node->nid = nid); |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1727 | rb_replace_node(&stable_node_dup->node, |
| 1728 | &page_node->node, |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1729 | root); |
| 1730 | if (is_page_sharing_candidate(page_node)) |
| 1731 | get_page(page); |
| 1732 | else |
| 1733 | page = NULL; |
| 1734 | } else { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1735 | rb_erase(&stable_node_dup->node, root); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1736 | page = NULL; |
| 1737 | } |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1738 | } else { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1739 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
| 1740 | __stable_node_dup_del(stable_node_dup); |
| 1741 | if (page_node) { |
| 1742 | VM_BUG_ON(page_node->head != &migrate_nodes); |
| 1743 | list_del(&page_node->list); |
| 1744 | DO_NUMA(page_node->nid = nid); |
| 1745 | stable_node_chain_add_dup(page_node, stable_node); |
| 1746 | if (is_page_sharing_candidate(page_node)) |
| 1747 | get_page(page); |
| 1748 | else |
| 1749 | page = NULL; |
| 1750 | } else { |
| 1751 | page = NULL; |
| 1752 | } |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1753 | } |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1754 | stable_node_dup->head = &migrate_nodes; |
| 1755 | list_add(&stable_node_dup->list, stable_node_dup->head); |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 1756 | return page; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1757 | |
| 1758 | chain_append: |
| 1759 | /* stable_node_dup could be null if it reached the limit */ |
| 1760 | if (!stable_node_dup) |
| 1761 | stable_node_dup = stable_node_any; |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1762 | /* |
| 1763 | * If stable_node was a chain and chain_prune collapsed it, |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1764 | * stable_node has been updated to be the new regular |
| 1765 | * stable_node. A collapse of the chain is indistinguishable |
| 1766 | * from the case there was no chain in the stable |
| 1767 | * rbtree. Otherwise stable_node is the chain and |
| 1768 | * stable_node_dup is the dup to replace. |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1769 | */ |
Andrea Arcangeli | 0ba1d0f | 2017-07-06 15:37:02 -0700 | [diff] [blame] | 1770 | if (stable_node_dup == stable_node) { |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1771 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
| 1772 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1773 | /* chain is missing so create it */ |
| 1774 | stable_node = alloc_stable_node_chain(stable_node_dup, |
| 1775 | root); |
| 1776 | if (!stable_node) |
| 1777 | return NULL; |
| 1778 | } |
| 1779 | /* |
| 1780 | * Add this stable_node dup that was |
| 1781 | * migrated to the stable_node chain |
| 1782 | * of the current nid for this page |
| 1783 | * content. |
| 1784 | */ |
Andrea Arcangeli | b4fecc6 | 2017-07-06 15:36:59 -0700 | [diff] [blame] | 1785 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
| 1786 | VM_BUG_ON(!is_stable_node_dup(stable_node_dup)); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1787 | VM_BUG_ON(page_node->head != &migrate_nodes); |
| 1788 | list_del(&page_node->list); |
| 1789 | DO_NUMA(page_node->nid = nid); |
| 1790 | stable_node_chain_add_dup(page_node, stable_node); |
| 1791 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1792 | } |
| 1793 | |
| 1794 | /* |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 1795 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1796 | * into the stable tree. |
| 1797 | * |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1798 | * This function returns the stable tree node just allocated on success, |
| 1799 | * NULL otherwise. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1800 | */ |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1801 | static struct stable_node *stable_tree_insert(struct page *kpage) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1802 | { |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1803 | int nid; |
| 1804 | unsigned long kpfn; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1805 | struct rb_root *root; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1806 | struct rb_node **new; |
Andrea Arcangeli | f2e5ff8 | 2015-11-05 18:49:10 -0800 | [diff] [blame] | 1807 | struct rb_node *parent; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1808 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
| 1809 | bool need_chain = false; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1810 | |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1811 | kpfn = page_to_pfn(kpage); |
| 1812 | nid = get_kpfn_nid(kpfn); |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1813 | root = root_stable_tree + nid; |
Andrea Arcangeli | f2e5ff8 | 2015-11-05 18:49:10 -0800 | [diff] [blame] | 1814 | again: |
| 1815 | parent = NULL; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1816 | new = &root->rb_node; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1817 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1818 | while (*new) { |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 1819 | struct page *tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1820 | int ret; |
| 1821 | |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 1822 | cond_resched(); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1823 | stable_node = rb_entry(*new, struct stable_node, node); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1824 | stable_node_any = NULL; |
Andrea Arcangeli | 8dc5ffc | 2017-07-06 15:37:05 -0700 | [diff] [blame] | 1825 | tree_page = chain(&stable_node_dup, stable_node, root); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1826 | if (!stable_node_dup) { |
| 1827 | /* |
| 1828 | * Either all stable_node dups were full in |
| 1829 | * this stable_node chain, or this chain was |
| 1830 | * empty and should be rb_erased. |
| 1831 | */ |
| 1832 | stable_node_any = stable_node_dup_any(stable_node, |
| 1833 | root); |
| 1834 | if (!stable_node_any) { |
| 1835 | /* rb_erase just run */ |
| 1836 | goto again; |
| 1837 | } |
| 1838 | /* |
| 1839 | * Take any of the stable_node dups page of |
| 1840 | * this stable_node chain to let the tree walk |
| 1841 | * continue. All KSM pages belonging to the |
| 1842 | * stable_node dups in a stable_node chain |
| 1843 | * have the same content and they're |
| 1844 | * wrprotected at all times. Any will work |
| 1845 | * fine to continue the walk. |
| 1846 | */ |
| 1847 | tree_page = get_ksm_page(stable_node_any, false); |
| 1848 | } |
| 1849 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); |
Andrea Arcangeli | f2e5ff8 | 2015-11-05 18:49:10 -0800 | [diff] [blame] | 1850 | if (!tree_page) { |
| 1851 | /* |
| 1852 | * If we walked over a stale stable_node, |
| 1853 | * get_ksm_page() will call rb_erase() and it |
| 1854 | * may rebalance the tree from under us. So |
| 1855 | * restart the search from scratch. Returning |
| 1856 | * NULL would be safe too, but we'd generate |
| 1857 | * false negative insertions just because some |
| 1858 | * stable_node was stale. |
| 1859 | */ |
| 1860 | goto again; |
| 1861 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1862 | |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 1863 | ret = memcmp_pages(kpage, tree_page); |
| 1864 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1865 | |
| 1866 | parent = *new; |
| 1867 | if (ret < 0) |
| 1868 | new = &parent->rb_left; |
| 1869 | else if (ret > 0) |
| 1870 | new = &parent->rb_right; |
| 1871 | else { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1872 | need_chain = true; |
| 1873 | break; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1874 | } |
| 1875 | } |
| 1876 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1877 | stable_node_dup = alloc_stable_node(); |
| 1878 | if (!stable_node_dup) |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1879 | return NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1880 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1881 | INIT_HLIST_HEAD(&stable_node_dup->hlist); |
| 1882 | stable_node_dup->kpfn = kpfn; |
| 1883 | set_page_stable_node(kpage, stable_node_dup); |
| 1884 | stable_node_dup->rmap_hlist_len = 0; |
| 1885 | DO_NUMA(stable_node_dup->nid = nid); |
| 1886 | if (!need_chain) { |
| 1887 | rb_link_node(&stable_node_dup->node, parent, new); |
| 1888 | rb_insert_color(&stable_node_dup->node, root); |
| 1889 | } else { |
| 1890 | if (!is_stable_node_chain(stable_node)) { |
| 1891 | struct stable_node *orig = stable_node; |
| 1892 | /* chain is missing so create it */ |
| 1893 | stable_node = alloc_stable_node_chain(orig, root); |
| 1894 | if (!stable_node) { |
| 1895 | free_stable_node(stable_node_dup); |
| 1896 | return NULL; |
| 1897 | } |
| 1898 | } |
| 1899 | stable_node_chain_add_dup(stable_node_dup, stable_node); |
| 1900 | } |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 1901 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1902 | return stable_node_dup; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1903 | } |
| 1904 | |
| 1905 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1906 | * unstable_tree_search_insert - search for identical page, |
| 1907 | * else insert rmap_item into the unstable tree. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1908 | * |
| 1909 | * This function searches for a page in the unstable tree identical to the |
| 1910 | * page currently being scanned; and if no identical page is found in the |
| 1911 | * tree, we insert rmap_item as a new object into the unstable tree. |
| 1912 | * |
| 1913 | * This function returns pointer to rmap_item found to be identical |
| 1914 | * to the currently scanned page, NULL otherwise. |
| 1915 | * |
| 1916 | * This function does both searching and inserting, because they share |
| 1917 | * the same walking algorithm in an rbtree. |
| 1918 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1919 | static |
| 1920 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, |
| 1921 | struct page *page, |
| 1922 | struct page **tree_pagep) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1923 | { |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1924 | struct rb_node **new; |
| 1925 | struct rb_root *root; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1926 | struct rb_node *parent = NULL; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1927 | int nid; |
| 1928 | |
| 1929 | nid = get_kpfn_nid(page_to_pfn(page)); |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 1930 | root = root_unstable_tree + nid; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1931 | new = &root->rb_node; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1932 | |
| 1933 | while (*new) { |
| 1934 | struct rmap_item *tree_rmap_item; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1935 | struct page *tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1936 | int ret; |
| 1937 | |
Hugh Dickins | d178f27 | 2009-11-09 15:58:23 +0000 | [diff] [blame] | 1938 | cond_resched(); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1939 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1940 | tree_page = get_mergeable_page(tree_rmap_item); |
Andrea Arcangeli | c8f95ed | 2015-11-05 18:49:19 -0800 | [diff] [blame] | 1941 | if (!tree_page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1942 | return NULL; |
| 1943 | |
| 1944 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1945 | * Don't substitute a ksm page for a forked page. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1946 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1947 | if (page == tree_page) { |
| 1948 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1949 | return NULL; |
| 1950 | } |
| 1951 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1952 | ret = memcmp_pages(page, tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1953 | |
| 1954 | parent = *new; |
| 1955 | if (ret < 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1956 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1957 | new = &parent->rb_left; |
| 1958 | } else if (ret > 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1959 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1960 | new = &parent->rb_right; |
Hugh Dickins | b599cbd | 2013-02-22 16:36:05 -0800 | [diff] [blame] | 1961 | } else if (!ksm_merge_across_nodes && |
| 1962 | page_to_nid(tree_page) != nid) { |
| 1963 | /* |
| 1964 | * If tree_page has been migrated to another NUMA node, |
| 1965 | * it will be flushed out and put in the right unstable |
| 1966 | * tree next time: only merge with it when across_nodes. |
| 1967 | */ |
| 1968 | put_page(tree_page); |
| 1969 | return NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1970 | } else { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 1971 | *tree_pagep = tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1972 | return tree_rmap_item; |
| 1973 | } |
| 1974 | } |
| 1975 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 1976 | rmap_item->address |= UNSTABLE_FLAG; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1977 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
Hugh Dickins | e850dcf | 2013-02-22 16:35:03 -0800 | [diff] [blame] | 1978 | DO_NUMA(rmap_item->nid = nid); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1979 | rb_link_node(&rmap_item->node, parent, new); |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 1980 | rb_insert_color(&rmap_item->node, root); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1981 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 1982 | ksm_pages_unshared++; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1983 | return NULL; |
| 1984 | } |
| 1985 | |
| 1986 | /* |
| 1987 | * stable_tree_append - add another rmap_item to the linked list of |
| 1988 | * rmap_items hanging off a given node of the stable tree, all sharing |
| 1989 | * the same ksm page. |
| 1990 | */ |
| 1991 | static void stable_tree_append(struct rmap_item *rmap_item, |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1992 | struct stable_node *stable_node, |
| 1993 | bool max_page_sharing_bypass) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1994 | { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 1995 | /* |
| 1996 | * rmap won't find this mapping if we don't insert the |
| 1997 | * rmap_item in the right stable_node |
| 1998 | * duplicate. page_migration could break later if rmap breaks, |
| 1999 | * so we can as well crash here. We really need to check for |
| 2000 | * rmap_hlist_len == STABLE_NODE_CHAIN, but we can as well check |
| 2001 | * for other negative values as an undeflow if detected here |
| 2002 | * for the first time (and not when decreasing rmap_hlist_len) |
| 2003 | * would be sign of memory corruption in the stable_node. |
| 2004 | */ |
| 2005 | BUG_ON(stable_node->rmap_hlist_len < 0); |
| 2006 | |
| 2007 | stable_node->rmap_hlist_len++; |
| 2008 | if (!max_page_sharing_bypass) |
| 2009 | /* possibly non fatal but unexpected overflow, only warn */ |
| 2010 | WARN_ON_ONCE(stable_node->rmap_hlist_len > |
| 2011 | ksm_max_page_sharing); |
| 2012 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2013 | rmap_item->head = stable_node; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2014 | rmap_item->address |= STABLE_FLAG; |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2015 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 2016 | |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2017 | if (rmap_item->hlist.next) |
| 2018 | ksm_pages_sharing++; |
| 2019 | else |
| 2020 | ksm_pages_shared++; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2021 | } |
| 2022 | |
| 2023 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 2024 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
| 2025 | * if not, compare checksum to previous and if it's the same, see if page can |
| 2026 | * be inserted into the unstable tree, or merged with a page already there and |
| 2027 | * both transferred to the stable tree. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2028 | * |
| 2029 | * @page: the page that we are searching identical page to. |
| 2030 | * @rmap_item: the reverse mapping into the virtual address of this page |
| 2031 | */ |
| 2032 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) |
| 2033 | { |
Kirill Tkhai | 4b22927 | 2017-10-03 16:14:27 -0700 | [diff] [blame] | 2034 | struct mm_struct *mm = rmap_item->mm; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2035 | struct rmap_item *tree_rmap_item; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2036 | struct page *tree_page = NULL; |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2037 | struct stable_node *stable_node; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2038 | struct page *kpage; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2039 | unsigned int checksum; |
| 2040 | int err; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2041 | bool max_page_sharing_bypass = false; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2042 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2043 | stable_node = page_stable_node(page); |
| 2044 | if (stable_node) { |
| 2045 | if (stable_node->head != &migrate_nodes && |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2046 | get_kpfn_nid(READ_ONCE(stable_node->kpfn)) != |
| 2047 | NUMA(stable_node->nid)) { |
| 2048 | stable_node_dup_del(stable_node); |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2049 | stable_node->head = &migrate_nodes; |
| 2050 | list_add(&stable_node->list, stable_node->head); |
| 2051 | } |
| 2052 | if (stable_node->head != &migrate_nodes && |
| 2053 | rmap_item->head == stable_node) |
| 2054 | return; |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2055 | /* |
| 2056 | * If it's a KSM fork, allow it to go over the sharing limit |
| 2057 | * without warnings. |
| 2058 | */ |
| 2059 | if (!is_page_sharing_candidate(stable_node)) |
| 2060 | max_page_sharing_bypass = true; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2061 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2062 | |
| 2063 | /* We first start with searching the page inside the stable tree */ |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2064 | kpage = stable_tree_search(page); |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2065 | if (kpage == page && rmap_item->head == stable_node) { |
| 2066 | put_page(kpage); |
| 2067 | return; |
| 2068 | } |
| 2069 | |
| 2070 | remove_rmap_item_from_tree(rmap_item); |
| 2071 | |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2072 | if (kpage) { |
Hugh Dickins | 08beca4 | 2009-12-14 17:59:21 -0800 | [diff] [blame] | 2073 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2074 | if (!err) { |
| 2075 | /* |
| 2076 | * The page was successfully merged: |
| 2077 | * add its rmap_item to the stable tree. |
| 2078 | */ |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2079 | lock_page(kpage); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2080 | stable_tree_append(rmap_item, page_stable_node(kpage), |
| 2081 | max_page_sharing_bypass); |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2082 | unlock_page(kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2083 | } |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2084 | put_page(kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2085 | return; |
| 2086 | } |
| 2087 | |
| 2088 | /* |
Hugh Dickins | 4035c07a | 2009-12-14 17:59:27 -0800 | [diff] [blame] | 2089 | * If the hash value of the page has changed from the last time |
| 2090 | * we calculated it, this page is changing frequently: therefore we |
| 2091 | * don't want to insert it in the unstable tree, and we don't want |
| 2092 | * to waste our time searching for something identical to it there. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2093 | */ |
| 2094 | checksum = calc_checksum(page); |
| 2095 | if (rmap_item->oldchecksum != checksum) { |
| 2096 | rmap_item->oldchecksum = checksum; |
| 2097 | return; |
| 2098 | } |
| 2099 | |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 2100 | /* |
| 2101 | * Same checksum as an empty page. We attempt to merge it with the |
| 2102 | * appropriate zero page if the user enabled this via sysfs. |
| 2103 | */ |
| 2104 | if (ksm_use_zero_pages && (checksum == zero_checksum)) { |
| 2105 | struct vm_area_struct *vma; |
| 2106 | |
Kirill Tkhai | 4b22927 | 2017-10-03 16:14:27 -0700 | [diff] [blame] | 2107 | down_read(&mm->mmap_sem); |
| 2108 | vma = find_mergeable_vma(mm, rmap_item->address); |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 2109 | err = try_to_merge_one_page(vma, page, |
| 2110 | ZERO_PAGE(rmap_item->address)); |
Kirill Tkhai | 4b22927 | 2017-10-03 16:14:27 -0700 | [diff] [blame] | 2111 | up_read(&mm->mmap_sem); |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 2112 | /* |
| 2113 | * In case of failure, the page was not really empty, so we |
| 2114 | * need to continue. Otherwise we're done. |
| 2115 | */ |
| 2116 | if (!err) |
| 2117 | return; |
| 2118 | } |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2119 | tree_rmap_item = |
| 2120 | unstable_tree_search_insert(rmap_item, page, &tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2121 | if (tree_rmap_item) { |
Claudio Imbrenda | 77da2ba | 2018-04-05 16:25:41 -0700 | [diff] [blame] | 2122 | bool split; |
| 2123 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2124 | kpage = try_to_merge_two_pages(rmap_item, page, |
| 2125 | tree_rmap_item, tree_page); |
Claudio Imbrenda | 77da2ba | 2018-04-05 16:25:41 -0700 | [diff] [blame] | 2126 | /* |
| 2127 | * If both pages we tried to merge belong to the same compound |
| 2128 | * page, then we actually ended up increasing the reference |
| 2129 | * count of the same compound page twice, and split_huge_page |
| 2130 | * failed. |
| 2131 | * Here we set a flag if that happened, and we use it later to |
| 2132 | * try split_huge_page again. Since we call put_page right |
| 2133 | * afterwards, the reference count will be correct and |
| 2134 | * split_huge_page should succeed. |
| 2135 | */ |
| 2136 | split = PageTransCompound(page) |
| 2137 | && compound_head(page) == compound_head(tree_page); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2138 | put_page(tree_page); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2139 | if (kpage) { |
Hugh Dickins | bc56620 | 2013-02-22 16:36:06 -0800 | [diff] [blame] | 2140 | /* |
| 2141 | * The pages were successfully merged: insert new |
| 2142 | * node in the stable tree and add both rmap_items. |
| 2143 | */ |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2144 | lock_page(kpage); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2145 | stable_node = stable_tree_insert(kpage); |
| 2146 | if (stable_node) { |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2147 | stable_tree_append(tree_rmap_item, stable_node, |
| 2148 | false); |
| 2149 | stable_tree_append(rmap_item, stable_node, |
| 2150 | false); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2151 | } |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2152 | unlock_page(kpage); |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2153 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2154 | /* |
| 2155 | * If we fail to insert the page into the stable tree, |
| 2156 | * we will have 2 virtual addresses that are pointing |
| 2157 | * to a ksm page left outside the stable tree, |
| 2158 | * in which case we need to break_cow on both. |
| 2159 | */ |
Hugh Dickins | 7b6ba2c | 2009-12-14 17:59:20 -0800 | [diff] [blame] | 2160 | if (!stable_node) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame] | 2161 | break_cow(tree_rmap_item); |
| 2162 | break_cow(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2163 | } |
Claudio Imbrenda | 77da2ba | 2018-04-05 16:25:41 -0700 | [diff] [blame] | 2164 | } else if (split) { |
| 2165 | /* |
| 2166 | * We are here if we tried to merge two pages and |
| 2167 | * failed because they both belonged to the same |
| 2168 | * compound page. We will split the page now, but no |
| 2169 | * merging will take place. |
| 2170 | * We do not want to add the cost of a full lock; if |
| 2171 | * the page is locked, it is better to skip it and |
| 2172 | * perhaps try again later. |
| 2173 | */ |
| 2174 | if (!trylock_page(page)) |
| 2175 | return; |
| 2176 | split_huge_page(page); |
| 2177 | unlock_page(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2178 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2179 | } |
| 2180 | } |
| 2181 | |
| 2182 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2183 | struct rmap_item **rmap_list, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2184 | unsigned long addr) |
| 2185 | { |
| 2186 | struct rmap_item *rmap_item; |
| 2187 | |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2188 | while (*rmap_list) { |
| 2189 | rmap_item = *rmap_list; |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 2190 | if ((rmap_item->address & PAGE_MASK) == addr) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2191 | return rmap_item; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2192 | if (rmap_item->address > addr) |
| 2193 | break; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2194 | *rmap_list = rmap_item->rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2195 | remove_rmap_item_from_tree(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2196 | free_rmap_item(rmap_item); |
| 2197 | } |
| 2198 | |
| 2199 | rmap_item = alloc_rmap_item(); |
| 2200 | if (rmap_item) { |
| 2201 | /* It has already been zeroed */ |
| 2202 | rmap_item->mm = mm_slot->mm; |
| 2203 | rmap_item->address = addr; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2204 | rmap_item->rmap_list = *rmap_list; |
| 2205 | *rmap_list = rmap_item; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2206 | } |
| 2207 | return rmap_item; |
| 2208 | } |
| 2209 | |
| 2210 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) |
| 2211 | { |
| 2212 | struct mm_struct *mm; |
| 2213 | struct mm_slot *slot; |
| 2214 | struct vm_area_struct *vma; |
| 2215 | struct rmap_item *rmap_item; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2216 | int nid; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2217 | |
| 2218 | if (list_empty(&ksm_mm_head.mm_list)) |
| 2219 | return NULL; |
| 2220 | |
| 2221 | slot = ksm_scan.mm_slot; |
| 2222 | if (slot == &ksm_mm_head) { |
Hugh Dickins | 2919bfd | 2011-01-13 15:47:29 -0800 | [diff] [blame] | 2223 | /* |
| 2224 | * A number of pages can hang around indefinitely on per-cpu |
| 2225 | * pagevecs, raised page count preventing write_protect_page |
| 2226 | * from merging them. Though it doesn't really matter much, |
| 2227 | * it is puzzling to see some stuck in pages_volatile until |
| 2228 | * other activity jostles them out, and they also prevented |
| 2229 | * LTP's KSM test from succeeding deterministically; so drain |
| 2230 | * them here (here rather than on entry to ksm_do_scan(), |
| 2231 | * so we don't IPI too often when pages_to_scan is set low). |
| 2232 | */ |
| 2233 | lru_add_drain_all(); |
| 2234 | |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2235 | /* |
| 2236 | * Whereas stale stable_nodes on the stable_tree itself |
| 2237 | * get pruned in the regular course of stable_tree_search(), |
| 2238 | * those moved out to the migrate_nodes list can accumulate: |
| 2239 | * so prune them once before each full scan. |
| 2240 | */ |
| 2241 | if (!ksm_merge_across_nodes) { |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 2242 | struct stable_node *stable_node, *next; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2243 | struct page *page; |
| 2244 | |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 2245 | list_for_each_entry_safe(stable_node, next, |
| 2246 | &migrate_nodes, list) { |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2247 | page = get_ksm_page(stable_node, false); |
| 2248 | if (page) |
| 2249 | put_page(page); |
| 2250 | cond_resched(); |
| 2251 | } |
| 2252 | } |
| 2253 | |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2254 | for (nid = 0; nid < ksm_nr_node_ids; nid++) |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2255 | root_unstable_tree[nid] = RB_ROOT; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2256 | |
| 2257 | spin_lock(&ksm_mmlist_lock); |
| 2258 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); |
| 2259 | ksm_scan.mm_slot = slot; |
| 2260 | spin_unlock(&ksm_mmlist_lock); |
Hugh Dickins | 2b47261 | 2011-06-15 15:08:58 -0700 | [diff] [blame] | 2261 | /* |
| 2262 | * Although we tested list_empty() above, a racing __ksm_exit |
| 2263 | * of the last mm on the list may have removed it since then. |
| 2264 | */ |
| 2265 | if (slot == &ksm_mm_head) |
| 2266 | return NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2267 | next_mm: |
| 2268 | ksm_scan.address = 0; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2269 | ksm_scan.rmap_list = &slot->rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2270 | } |
| 2271 | |
| 2272 | mm = slot->mm; |
| 2273 | down_read(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2274 | if (ksm_test_exit(mm)) |
| 2275 | vma = NULL; |
| 2276 | else |
| 2277 | vma = find_vma(mm, ksm_scan.address); |
| 2278 | |
| 2279 | for (; vma; vma = vma->vm_next) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2280 | if (!(vma->vm_flags & VM_MERGEABLE)) |
| 2281 | continue; |
| 2282 | if (ksm_scan.address < vma->vm_start) |
| 2283 | ksm_scan.address = vma->vm_start; |
| 2284 | if (!vma->anon_vma) |
| 2285 | ksm_scan.address = vma->vm_end; |
| 2286 | |
| 2287 | while (ksm_scan.address < vma->vm_end) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2288 | if (ksm_test_exit(mm)) |
| 2289 | break; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2290 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
Andrea Arcangeli | 21ae5b0 | 2011-01-13 15:47:00 -0800 | [diff] [blame] | 2291 | if (IS_ERR_OR_NULL(*page)) { |
| 2292 | ksm_scan.address += PAGE_SIZE; |
| 2293 | cond_resched(); |
| 2294 | continue; |
| 2295 | } |
Kirill A. Shutemov | f765f54 | 2016-01-15 16:53:03 -0800 | [diff] [blame] | 2296 | if (PageAnon(*page)) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2297 | flush_anon_page(vma, *page, ksm_scan.address); |
| 2298 | flush_dcache_page(*page); |
| 2299 | rmap_item = get_next_rmap_item(slot, |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2300 | ksm_scan.rmap_list, ksm_scan.address); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2301 | if (rmap_item) { |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2302 | ksm_scan.rmap_list = |
| 2303 | &rmap_item->rmap_list; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2304 | ksm_scan.address += PAGE_SIZE; |
| 2305 | } else |
| 2306 | put_page(*page); |
| 2307 | up_read(&mm->mmap_sem); |
| 2308 | return rmap_item; |
| 2309 | } |
Andrea Arcangeli | 21ae5b0 | 2011-01-13 15:47:00 -0800 | [diff] [blame] | 2310 | put_page(*page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2311 | ksm_scan.address += PAGE_SIZE; |
| 2312 | cond_resched(); |
| 2313 | } |
| 2314 | } |
| 2315 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2316 | if (ksm_test_exit(mm)) { |
| 2317 | ksm_scan.address = 0; |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2318 | ksm_scan.rmap_list = &slot->rmap_list; |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2319 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2320 | /* |
| 2321 | * Nuke all the rmap_items that are above this current rmap: |
| 2322 | * because there were no VM_MERGEABLE vmas with such addresses. |
| 2323 | */ |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2324 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2325 | |
| 2326 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2327 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
| 2328 | struct mm_slot, mm_list); |
| 2329 | if (ksm_scan.address == 0) { |
| 2330 | /* |
| 2331 | * We've completed a full scan of all vmas, holding mmap_sem |
| 2332 | * throughout, and found no VM_MERGEABLE: so do the same as |
| 2333 | * __ksm_exit does to remove this mm from all our lists now. |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2334 | * This applies either when cleaning up after __ksm_exit |
| 2335 | * (but beware: we can reach here even before __ksm_exit), |
| 2336 | * or when all VM_MERGEABLE areas have been unmapped (and |
| 2337 | * mmap_sem then protects against race with MADV_MERGEABLE). |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2338 | */ |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 2339 | hash_del(&slot->link); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2340 | list_del(&slot->mm_list); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2341 | spin_unlock(&ksm_mmlist_lock); |
| 2342 | |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2343 | free_mm_slot(slot); |
| 2344 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2345 | up_read(&mm->mmap_sem); |
| 2346 | mmdrop(mm); |
| 2347 | } else { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2348 | up_read(&mm->mmap_sem); |
Zhou Chengming | 7496fea | 2016-05-12 15:42:21 -0700 | [diff] [blame] | 2349 | /* |
| 2350 | * up_read(&mm->mmap_sem) first because after |
| 2351 | * spin_unlock(&ksm_mmlist_lock) run, the "mm" may |
| 2352 | * already have been freed under us by __ksm_exit() |
| 2353 | * because the "mm_slot" is still hashed and |
| 2354 | * ksm_scan.mm_slot doesn't point to it anymore. |
| 2355 | */ |
| 2356 | spin_unlock(&ksm_mmlist_lock); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2357 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2358 | |
| 2359 | /* Repeat until we've completed scanning the whole list */ |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2360 | slot = ksm_scan.mm_slot; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2361 | if (slot != &ksm_mm_head) |
| 2362 | goto next_mm; |
| 2363 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2364 | ksm_scan.seqnr++; |
| 2365 | return NULL; |
| 2366 | } |
| 2367 | |
| 2368 | /** |
| 2369 | * ksm_do_scan - the ksm scanner main worker function. |
Mike Rapoport | b7701a5 | 2018-02-06 15:42:13 -0800 | [diff] [blame] | 2370 | * @scan_npages: number of pages we want to scan before we return. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2371 | */ |
| 2372 | static void ksm_do_scan(unsigned int scan_npages) |
| 2373 | { |
| 2374 | struct rmap_item *rmap_item; |
Dan Carpenter | 22eccdd | 2010-04-23 13:18:10 -0400 | [diff] [blame] | 2375 | struct page *uninitialized_var(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2376 | |
Andrea Arcangeli | 878aee7 | 2011-01-13 15:47:10 -0800 | [diff] [blame] | 2377 | while (scan_npages-- && likely(!freezing(current))) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2378 | cond_resched(); |
| 2379 | rmap_item = scan_get_next_rmap_item(&page); |
| 2380 | if (!rmap_item) |
| 2381 | return; |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2382 | cmp_and_merge_page(page, rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2383 | put_page(page); |
| 2384 | } |
| 2385 | } |
| 2386 | |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2387 | static int ksmd_should_run(void) |
| 2388 | { |
| 2389 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); |
| 2390 | } |
| 2391 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2392 | static int ksm_scan_thread(void *nothing) |
| 2393 | { |
Andrea Arcangeli | 878aee7 | 2011-01-13 15:47:10 -0800 | [diff] [blame] | 2394 | set_freezable(); |
Izik Eidus | 339aa62 | 2009-09-21 17:02:07 -0700 | [diff] [blame] | 2395 | set_user_nice(current, 5); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2396 | |
| 2397 | while (!kthread_should_stop()) { |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2398 | mutex_lock(&ksm_thread_mutex); |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2399 | wait_while_offlining(); |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2400 | if (ksmd_should_run()) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2401 | ksm_do_scan(ksm_thread_pages_to_scan); |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2402 | mutex_unlock(&ksm_thread_mutex); |
| 2403 | |
Andrea Arcangeli | 878aee7 | 2011-01-13 15:47:10 -0800 | [diff] [blame] | 2404 | try_to_freeze(); |
| 2405 | |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2406 | if (ksmd_should_run()) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2407 | schedule_timeout_interruptible( |
| 2408 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); |
| 2409 | } else { |
Andrea Arcangeli | 878aee7 | 2011-01-13 15:47:10 -0800 | [diff] [blame] | 2410 | wait_event_freezable(ksm_thread_wait, |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2411 | ksmd_should_run() || kthread_should_stop()); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2412 | } |
| 2413 | } |
| 2414 | return 0; |
| 2415 | } |
| 2416 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2417 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
| 2418 | unsigned long end, int advice, unsigned long *vm_flags) |
| 2419 | { |
| 2420 | struct mm_struct *mm = vma->vm_mm; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2421 | int err; |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2422 | |
| 2423 | switch (advice) { |
| 2424 | case MADV_MERGEABLE: |
| 2425 | /* |
| 2426 | * Be somewhat over-protective for now! |
| 2427 | */ |
| 2428 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | |
| 2429 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | |
Kirill A. Shutemov | 0661a33 | 2015-02-10 14:10:04 -0800 | [diff] [blame] | 2430 | VM_HUGETLB | VM_MIXEDMAP)) |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2431 | return 0; /* just ignore the advice */ |
| 2432 | |
Dave Jiang | e1fb4a0 | 2018-08-17 15:43:40 -0700 | [diff] [blame] | 2433 | if (vma_is_dax(vma)) |
| 2434 | return 0; |
| 2435 | |
Konstantin Khlebnikov | cc2383e | 2012-10-08 16:28:37 -0700 | [diff] [blame] | 2436 | #ifdef VM_SAO |
| 2437 | if (*vm_flags & VM_SAO) |
| 2438 | return 0; |
| 2439 | #endif |
Khalid Aziz | 74a0496 | 2018-02-23 15:46:41 -0700 | [diff] [blame] | 2440 | #ifdef VM_SPARC_ADI |
| 2441 | if (*vm_flags & VM_SPARC_ADI) |
| 2442 | return 0; |
| 2443 | #endif |
Konstantin Khlebnikov | cc2383e | 2012-10-08 16:28:37 -0700 | [diff] [blame] | 2444 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2445 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
| 2446 | err = __ksm_enter(mm); |
| 2447 | if (err) |
| 2448 | return err; |
| 2449 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2450 | |
| 2451 | *vm_flags |= VM_MERGEABLE; |
| 2452 | break; |
| 2453 | |
| 2454 | case MADV_UNMERGEABLE: |
| 2455 | if (!(*vm_flags & VM_MERGEABLE)) |
| 2456 | return 0; /* just ignore the advice */ |
| 2457 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2458 | if (vma->anon_vma) { |
| 2459 | err = unmerge_ksm_pages(vma, start, end); |
| 2460 | if (err) |
| 2461 | return err; |
| 2462 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2463 | |
| 2464 | *vm_flags &= ~VM_MERGEABLE; |
| 2465 | break; |
| 2466 | } |
| 2467 | |
| 2468 | return 0; |
| 2469 | } |
| 2470 | |
| 2471 | int __ksm_enter(struct mm_struct *mm) |
| 2472 | { |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2473 | struct mm_slot *mm_slot; |
| 2474 | int needs_wakeup; |
| 2475 | |
| 2476 | mm_slot = alloc_mm_slot(); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2477 | if (!mm_slot) |
| 2478 | return -ENOMEM; |
| 2479 | |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2480 | /* Check ksm_run too? Would need tighter locking */ |
| 2481 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); |
| 2482 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2483 | spin_lock(&ksm_mmlist_lock); |
| 2484 | insert_to_mm_slots_hash(mm, mm_slot); |
| 2485 | /* |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2486 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
| 2487 | * insert just behind the scanning cursor, to let the area settle |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2488 | * down a little; when fork is followed by immediate exec, we don't |
| 2489 | * want ksmd to waste time setting up and tearing down an rmap_list. |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2490 | * |
| 2491 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its |
| 2492 | * scanning cursor, otherwise KSM pages in newly forked mms will be |
| 2493 | * missed: then we might as well insert at the end of the list. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2494 | */ |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2495 | if (ksm_run & KSM_RUN_UNMERGE) |
| 2496 | list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); |
| 2497 | else |
| 2498 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2499 | spin_unlock(&ksm_mmlist_lock); |
| 2500 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2501 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
Vegard Nossum | f1f1007 | 2017-02-27 14:30:07 -0800 | [diff] [blame] | 2502 | mmgrab(mm); |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 2503 | |
| 2504 | if (needs_wakeup) |
| 2505 | wake_up_interruptible(&ksm_thread_wait); |
| 2506 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2507 | return 0; |
| 2508 | } |
| 2509 | |
Andrea Arcangeli | 1c2fb7a | 2009-09-21 17:02:22 -0700 | [diff] [blame] | 2510 | void __ksm_exit(struct mm_struct *mm) |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2511 | { |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2512 | struct mm_slot *mm_slot; |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2513 | int easy_to_free = 0; |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2514 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2515 | /* |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2516 | * This process is exiting: if it's straightforward (as is the |
| 2517 | * case when ksmd was never running), free mm_slot immediately. |
| 2518 | * But if it's at the cursor or has rmap_items linked to it, use |
| 2519 | * mmap_sem to synchronize with any break_cows before pagetables |
| 2520 | * are freed, and leave the mm_slot on the list for ksmd to free. |
| 2521 | * Beware: ksm may already have noticed it exiting and freed the slot. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2522 | */ |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2523 | |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2524 | spin_lock(&ksm_mmlist_lock); |
| 2525 | mm_slot = get_mm_slot(mm); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2526 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
Hugh Dickins | 6514d51 | 2009-12-14 17:59:19 -0800 | [diff] [blame] | 2527 | if (!mm_slot->rmap_list) { |
Sasha Levin | 4ca3a69 | 2013-02-22 16:32:28 -0800 | [diff] [blame] | 2528 | hash_del(&mm_slot->link); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2529 | list_del(&mm_slot->mm_list); |
| 2530 | easy_to_free = 1; |
| 2531 | } else { |
| 2532 | list_move(&mm_slot->mm_list, |
| 2533 | &ksm_scan.mm_slot->mm_list); |
| 2534 | } |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2535 | } |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 2536 | spin_unlock(&ksm_mmlist_lock); |
| 2537 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2538 | if (easy_to_free) { |
| 2539 | free_mm_slot(mm_slot); |
| 2540 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
| 2541 | mmdrop(mm); |
| 2542 | } else if (mm_slot) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2543 | down_write(&mm->mmap_sem); |
| 2544 | up_write(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 2545 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 2546 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2547 | |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2548 | struct page *ksm_might_need_to_copy(struct page *page, |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2549 | struct vm_area_struct *vma, unsigned long address) |
| 2550 | { |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2551 | struct anon_vma *anon_vma = page_anon_vma(page); |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2552 | struct page *new_page; |
| 2553 | |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2554 | if (PageKsm(page)) { |
| 2555 | if (page_stable_node(page) && |
| 2556 | !(ksm_run & KSM_RUN_UNMERGE)) |
| 2557 | return page; /* no need to copy it */ |
| 2558 | } else if (!anon_vma) { |
| 2559 | return page; /* no need to copy it */ |
| 2560 | } else if (anon_vma->root == vma->anon_vma->root && |
| 2561 | page->index == linear_page_index(vma, address)) { |
| 2562 | return page; /* still no need to copy it */ |
| 2563 | } |
| 2564 | if (!PageUptodate(page)) |
| 2565 | return page; /* let do_swap_page report the error */ |
| 2566 | |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2567 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
| 2568 | if (new_page) { |
| 2569 | copy_user_highpage(new_page, page, address, vma); |
| 2570 | |
| 2571 | SetPageDirty(new_page); |
| 2572 | __SetPageUptodate(new_page); |
Kirill A. Shutemov | 48c935a | 2016-01-15 16:51:24 -0800 | [diff] [blame] | 2573 | __SetPageLocked(new_page); |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2574 | } |
| 2575 | |
Hugh Dickins | 5ad6468 | 2009-12-14 17:59:24 -0800 | [diff] [blame] | 2576 | return new_page; |
| 2577 | } |
| 2578 | |
Minchan Kim | 1df631a | 2017-05-03 14:54:23 -0700 | [diff] [blame] | 2579 | void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2580 | { |
| 2581 | struct stable_node *stable_node; |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2582 | struct rmap_item *rmap_item; |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2583 | int search_new_forks = 0; |
| 2584 | |
Sasha Levin | 309381fea | 2014-01-23 15:52:54 -0800 | [diff] [blame] | 2585 | VM_BUG_ON_PAGE(!PageKsm(page), page); |
Joonsoo Kim | 9f32624 | 2014-01-21 15:49:53 -0800 | [diff] [blame] | 2586 | |
| 2587 | /* |
| 2588 | * Rely on the page lock to protect against concurrent modifications |
| 2589 | * to that page's node of the stable tree. |
| 2590 | */ |
Sasha Levin | 309381fea | 2014-01-23 15:52:54 -0800 | [diff] [blame] | 2591 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2592 | |
| 2593 | stable_node = page_stable_node(page); |
| 2594 | if (!stable_node) |
Minchan Kim | 1df631a | 2017-05-03 14:54:23 -0700 | [diff] [blame] | 2595 | return; |
Minchan Kim | 5a83f94 | 2013-05-09 16:21:27 +0900 | [diff] [blame] | 2596 | |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2597 | again: |
Sasha Levin | b67bfe0 | 2013-02-27 17:06:00 -0800 | [diff] [blame] | 2598 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2599 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
Rik van Riel | 5beb493 | 2010-03-05 13:42:07 -0800 | [diff] [blame] | 2600 | struct anon_vma_chain *vmac; |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2601 | struct vm_area_struct *vma; |
| 2602 | |
Andrea Arcangeli | ad12695 | 2015-11-05 18:49:07 -0800 | [diff] [blame] | 2603 | cond_resched(); |
Hugh Dickins | b6b19f2 | 2012-12-19 17:44:29 -0800 | [diff] [blame] | 2604 | anon_vma_lock_read(anon_vma); |
Michel Lespinasse | bf181b9 | 2012-10-08 16:31:39 -0700 | [diff] [blame] | 2605 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
| 2606 | 0, ULONG_MAX) { |
Jia He | 1105a2f | 2018-06-14 15:26:14 -0700 | [diff] [blame] | 2607 | unsigned long addr; |
| 2608 | |
Andrea Arcangeli | ad12695 | 2015-11-05 18:49:07 -0800 | [diff] [blame] | 2609 | cond_resched(); |
Rik van Riel | 5beb493 | 2010-03-05 13:42:07 -0800 | [diff] [blame] | 2610 | vma = vmac->vma; |
Jia He | 1105a2f | 2018-06-14 15:26:14 -0700 | [diff] [blame] | 2611 | |
| 2612 | /* Ignore the stable/unstable/sqnr flags */ |
| 2613 | addr = rmap_item->address & ~KSM_FLAG_MASK; |
| 2614 | |
| 2615 | if (addr < vma->vm_start || addr >= vma->vm_end) |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2616 | continue; |
| 2617 | /* |
| 2618 | * Initially we examine only the vma which covers this |
| 2619 | * rmap_item; but later, if there is still work to do, |
| 2620 | * we examine covering vmas in other mms: in case they |
| 2621 | * were forked from the original since ksmd passed. |
| 2622 | */ |
| 2623 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) |
| 2624 | continue; |
| 2625 | |
Joonsoo Kim | 0dd1c7b | 2014-01-21 15:49:49 -0800 | [diff] [blame] | 2626 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| 2627 | continue; |
| 2628 | |
Jia He | 1105a2f | 2018-06-14 15:26:14 -0700 | [diff] [blame] | 2629 | if (!rwc->rmap_one(page, vma, addr, rwc->arg)) { |
Hugh Dickins | b6b19f2 | 2012-12-19 17:44:29 -0800 | [diff] [blame] | 2630 | anon_vma_unlock_read(anon_vma); |
Minchan Kim | 1df631a | 2017-05-03 14:54:23 -0700 | [diff] [blame] | 2631 | return; |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2632 | } |
Joonsoo Kim | 0dd1c7b | 2014-01-21 15:49:49 -0800 | [diff] [blame] | 2633 | if (rwc->done && rwc->done(page)) { |
| 2634 | anon_vma_unlock_read(anon_vma); |
Minchan Kim | 1df631a | 2017-05-03 14:54:23 -0700 | [diff] [blame] | 2635 | return; |
Joonsoo Kim | 0dd1c7b | 2014-01-21 15:49:49 -0800 | [diff] [blame] | 2636 | } |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2637 | } |
Hugh Dickins | b6b19f2 | 2012-12-19 17:44:29 -0800 | [diff] [blame] | 2638 | anon_vma_unlock_read(anon_vma); |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2639 | } |
| 2640 | if (!search_new_forks++) |
| 2641 | goto again; |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2642 | } |
| 2643 | |
Joonsoo Kim | 5262950 | 2014-01-21 15:49:50 -0800 | [diff] [blame] | 2644 | #ifdef CONFIG_MIGRATION |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2645 | void ksm_migrate_page(struct page *newpage, struct page *oldpage) |
| 2646 | { |
| 2647 | struct stable_node *stable_node; |
| 2648 | |
Sasha Levin | 309381fea | 2014-01-23 15:52:54 -0800 | [diff] [blame] | 2649 | VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); |
| 2650 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
| 2651 | VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage); |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2652 | |
| 2653 | stable_node = page_stable_node(newpage); |
| 2654 | if (stable_node) { |
Sasha Levin | 309381fea | 2014-01-23 15:52:54 -0800 | [diff] [blame] | 2655 | VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage); |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2656 | stable_node->kpfn = page_to_pfn(newpage); |
Hugh Dickins | c8d6553 | 2013-02-22 16:35:10 -0800 | [diff] [blame] | 2657 | /* |
| 2658 | * newpage->mapping was set in advance; now we need smp_wmb() |
| 2659 | * to make sure that the new stable_node->kpfn is visible |
| 2660 | * to get_ksm_page() before it can see that oldpage->mapping |
| 2661 | * has gone stale (or that PageSwapCache has been cleared). |
| 2662 | */ |
| 2663 | smp_wmb(); |
| 2664 | set_page_stable_node(oldpage, NULL); |
Hugh Dickins | e9995ef | 2009-12-14 17:59:31 -0800 | [diff] [blame] | 2665 | } |
| 2666 | } |
| 2667 | #endif /* CONFIG_MIGRATION */ |
| 2668 | |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2669 | #ifdef CONFIG_MEMORY_HOTREMOVE |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2670 | static void wait_while_offlining(void) |
| 2671 | { |
| 2672 | while (ksm_run & KSM_RUN_OFFLINE) { |
| 2673 | mutex_unlock(&ksm_thread_mutex); |
| 2674 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), |
NeilBrown | 7431620 | 2014-07-07 15:16:04 +1000 | [diff] [blame] | 2675 | TASK_UNINTERRUPTIBLE); |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2676 | mutex_lock(&ksm_thread_mutex); |
| 2677 | } |
| 2678 | } |
| 2679 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2680 | static bool stable_node_dup_remove_range(struct stable_node *stable_node, |
| 2681 | unsigned long start_pfn, |
| 2682 | unsigned long end_pfn) |
| 2683 | { |
| 2684 | if (stable_node->kpfn >= start_pfn && |
| 2685 | stable_node->kpfn < end_pfn) { |
| 2686 | /* |
| 2687 | * Don't get_ksm_page, page has already gone: |
| 2688 | * which is why we keep kpfn instead of page* |
| 2689 | */ |
| 2690 | remove_node_from_stable_tree(stable_node); |
| 2691 | return true; |
| 2692 | } |
| 2693 | return false; |
| 2694 | } |
| 2695 | |
| 2696 | static bool stable_node_chain_remove_range(struct stable_node *stable_node, |
| 2697 | unsigned long start_pfn, |
| 2698 | unsigned long end_pfn, |
| 2699 | struct rb_root *root) |
| 2700 | { |
| 2701 | struct stable_node *dup; |
| 2702 | struct hlist_node *hlist_safe; |
| 2703 | |
| 2704 | if (!is_stable_node_chain(stable_node)) { |
| 2705 | VM_BUG_ON(is_stable_node_dup(stable_node)); |
| 2706 | return stable_node_dup_remove_range(stable_node, start_pfn, |
| 2707 | end_pfn); |
| 2708 | } |
| 2709 | |
| 2710 | hlist_for_each_entry_safe(dup, hlist_safe, |
| 2711 | &stable_node->hlist, hlist_dup) { |
| 2712 | VM_BUG_ON(!is_stable_node_dup(dup)); |
| 2713 | stable_node_dup_remove_range(dup, start_pfn, end_pfn); |
| 2714 | } |
| 2715 | if (hlist_empty(&stable_node->hlist)) { |
| 2716 | free_stable_node_chain(stable_node, root); |
| 2717 | return true; /* notify caller that tree was rebalanced */ |
| 2718 | } else |
| 2719 | return false; |
| 2720 | } |
| 2721 | |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2722 | static void ksm_check_stable_tree(unsigned long start_pfn, |
| 2723 | unsigned long end_pfn) |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2724 | { |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 2725 | struct stable_node *stable_node, *next; |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2726 | struct rb_node *node; |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2727 | int nid; |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2728 | |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2729 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
| 2730 | node = rb_first(root_stable_tree + nid); |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2731 | while (node) { |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2732 | stable_node = rb_entry(node, struct stable_node, node); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2733 | if (stable_node_chain_remove_range(stable_node, |
| 2734 | start_pfn, end_pfn, |
| 2735 | root_stable_tree + |
| 2736 | nid)) |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2737 | node = rb_first(root_stable_tree + nid); |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2738 | else |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2739 | node = rb_next(node); |
| 2740 | cond_resched(); |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2741 | } |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2742 | } |
Geliang Tang | 0364041 | 2016-01-14 15:20:54 -0800 | [diff] [blame] | 2743 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
Hugh Dickins | 4146d2d | 2013-02-22 16:35:11 -0800 | [diff] [blame] | 2744 | if (stable_node->kpfn >= start_pfn && |
| 2745 | stable_node->kpfn < end_pfn) |
| 2746 | remove_node_from_stable_tree(stable_node); |
| 2747 | cond_resched(); |
| 2748 | } |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2749 | } |
| 2750 | |
| 2751 | static int ksm_memory_callback(struct notifier_block *self, |
| 2752 | unsigned long action, void *arg) |
| 2753 | { |
| 2754 | struct memory_notify *mn = arg; |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2755 | |
| 2756 | switch (action) { |
| 2757 | case MEM_GOING_OFFLINE: |
| 2758 | /* |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2759 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
| 2760 | * and remove_all_stable_nodes() while memory is going offline: |
| 2761 | * it is unsafe for them to touch the stable tree at this time. |
| 2762 | * But unmerge_ksm_pages(), rmap lookups and other entry points |
| 2763 | * which do not need the ksm_thread_mutex are all safe. |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2764 | */ |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2765 | mutex_lock(&ksm_thread_mutex); |
| 2766 | ksm_run |= KSM_RUN_OFFLINE; |
| 2767 | mutex_unlock(&ksm_thread_mutex); |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2768 | break; |
| 2769 | |
| 2770 | case MEM_OFFLINE: |
| 2771 | /* |
| 2772 | * Most of the work is done by page migration; but there might |
| 2773 | * be a few stable_nodes left over, still pointing to struct |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2774 | * pages which have been offlined: prune those from the tree, |
| 2775 | * otherwise get_ksm_page() might later try to access a |
| 2776 | * non-existent struct page. |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2777 | */ |
Hugh Dickins | ee0ea59 | 2013-02-22 16:35:05 -0800 | [diff] [blame] | 2778 | ksm_check_stable_tree(mn->start_pfn, |
| 2779 | mn->start_pfn + mn->nr_pages); |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2780 | /* fallthrough */ |
| 2781 | |
| 2782 | case MEM_CANCEL_OFFLINE: |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2783 | mutex_lock(&ksm_thread_mutex); |
| 2784 | ksm_run &= ~KSM_RUN_OFFLINE; |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2785 | mutex_unlock(&ksm_thread_mutex); |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2786 | |
| 2787 | smp_mb(); /* wake_up_bit advises this */ |
| 2788 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2789 | break; |
| 2790 | } |
| 2791 | return NOTIFY_OK; |
| 2792 | } |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2793 | #else |
| 2794 | static void wait_while_offlining(void) |
| 2795 | { |
| 2796 | } |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 2797 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
| 2798 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 2799 | #ifdef CONFIG_SYSFS |
| 2800 | /* |
| 2801 | * This all compiles without CONFIG_SYSFS, but is a waste of space. |
| 2802 | */ |
| 2803 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2804 | #define KSM_ATTR_RO(_name) \ |
| 2805 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) |
| 2806 | #define KSM_ATTR(_name) \ |
| 2807 | static struct kobj_attribute _name##_attr = \ |
| 2808 | __ATTR(_name, 0644, _name##_show, _name##_store) |
| 2809 | |
| 2810 | static ssize_t sleep_millisecs_show(struct kobject *kobj, |
| 2811 | struct kobj_attribute *attr, char *buf) |
| 2812 | { |
| 2813 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); |
| 2814 | } |
| 2815 | |
| 2816 | static ssize_t sleep_millisecs_store(struct kobject *kobj, |
| 2817 | struct kobj_attribute *attr, |
| 2818 | const char *buf, size_t count) |
| 2819 | { |
| 2820 | unsigned long msecs; |
| 2821 | int err; |
| 2822 | |
Jingoo Han | 3dbb95f | 2013-09-11 14:20:25 -0700 | [diff] [blame] | 2823 | err = kstrtoul(buf, 10, &msecs); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2824 | if (err || msecs > UINT_MAX) |
| 2825 | return -EINVAL; |
| 2826 | |
| 2827 | ksm_thread_sleep_millisecs = msecs; |
| 2828 | |
| 2829 | return count; |
| 2830 | } |
| 2831 | KSM_ATTR(sleep_millisecs); |
| 2832 | |
| 2833 | static ssize_t pages_to_scan_show(struct kobject *kobj, |
| 2834 | struct kobj_attribute *attr, char *buf) |
| 2835 | { |
| 2836 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); |
| 2837 | } |
| 2838 | |
| 2839 | static ssize_t pages_to_scan_store(struct kobject *kobj, |
| 2840 | struct kobj_attribute *attr, |
| 2841 | const char *buf, size_t count) |
| 2842 | { |
| 2843 | int err; |
| 2844 | unsigned long nr_pages; |
| 2845 | |
Jingoo Han | 3dbb95f | 2013-09-11 14:20:25 -0700 | [diff] [blame] | 2846 | err = kstrtoul(buf, 10, &nr_pages); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2847 | if (err || nr_pages > UINT_MAX) |
| 2848 | return -EINVAL; |
| 2849 | |
| 2850 | ksm_thread_pages_to_scan = nr_pages; |
| 2851 | |
| 2852 | return count; |
| 2853 | } |
| 2854 | KSM_ATTR(pages_to_scan); |
| 2855 | |
| 2856 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, |
| 2857 | char *buf) |
| 2858 | { |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2859 | return sprintf(buf, "%lu\n", ksm_run); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2860 | } |
| 2861 | |
| 2862 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, |
| 2863 | const char *buf, size_t count) |
| 2864 | { |
| 2865 | int err; |
| 2866 | unsigned long flags; |
| 2867 | |
Jingoo Han | 3dbb95f | 2013-09-11 14:20:25 -0700 | [diff] [blame] | 2868 | err = kstrtoul(buf, 10, &flags); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2869 | if (err || flags > UINT_MAX) |
| 2870 | return -EINVAL; |
| 2871 | if (flags > KSM_RUN_UNMERGE) |
| 2872 | return -EINVAL; |
| 2873 | |
| 2874 | /* |
| 2875 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. |
| 2876 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, |
Hugh Dickins | d0f209f | 2009-12-14 17:59:34 -0800 | [diff] [blame] | 2877 | * breaking COW to free the pages_shared (but leaves mm_slots |
| 2878 | * on the list for when ksmd may be set running again). |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2879 | */ |
| 2880 | |
| 2881 | mutex_lock(&ksm_thread_mutex); |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2882 | wait_while_offlining(); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2883 | if (ksm_run != flags) { |
| 2884 | ksm_run = flags; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2885 | if (flags & KSM_RUN_UNMERGE) { |
David Rientjes | e1e12d2 | 2012-12-11 16:02:56 -0800 | [diff] [blame] | 2886 | set_current_oom_origin(); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2887 | err = unmerge_and_remove_all_rmap_items(); |
David Rientjes | e1e12d2 | 2012-12-11 16:02:56 -0800 | [diff] [blame] | 2888 | clear_current_oom_origin(); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 2889 | if (err) { |
| 2890 | ksm_run = KSM_RUN_STOP; |
| 2891 | count = err; |
| 2892 | } |
| 2893 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 2894 | } |
| 2895 | mutex_unlock(&ksm_thread_mutex); |
| 2896 | |
| 2897 | if (flags & KSM_RUN_MERGE) |
| 2898 | wake_up_interruptible(&ksm_thread_wait); |
| 2899 | |
| 2900 | return count; |
| 2901 | } |
| 2902 | KSM_ATTR(run); |
| 2903 | |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2904 | #ifdef CONFIG_NUMA |
| 2905 | static ssize_t merge_across_nodes_show(struct kobject *kobj, |
| 2906 | struct kobj_attribute *attr, char *buf) |
| 2907 | { |
| 2908 | return sprintf(buf, "%u\n", ksm_merge_across_nodes); |
| 2909 | } |
| 2910 | |
| 2911 | static ssize_t merge_across_nodes_store(struct kobject *kobj, |
| 2912 | struct kobj_attribute *attr, |
| 2913 | const char *buf, size_t count) |
| 2914 | { |
| 2915 | int err; |
| 2916 | unsigned long knob; |
| 2917 | |
| 2918 | err = kstrtoul(buf, 10, &knob); |
| 2919 | if (err) |
| 2920 | return err; |
| 2921 | if (knob > 1) |
| 2922 | return -EINVAL; |
| 2923 | |
| 2924 | mutex_lock(&ksm_thread_mutex); |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 2925 | wait_while_offlining(); |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2926 | if (ksm_merge_across_nodes != knob) { |
Hugh Dickins | cbf86cf | 2013-02-22 16:35:08 -0800 | [diff] [blame] | 2927 | if (ksm_pages_shared || remove_all_stable_nodes()) |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2928 | err = -EBUSY; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2929 | else if (root_stable_tree == one_stable_tree) { |
| 2930 | struct rb_root *buf; |
| 2931 | /* |
| 2932 | * This is the first time that we switch away from the |
| 2933 | * default of merging across nodes: must now allocate |
| 2934 | * a buffer to hold as many roots as may be needed. |
| 2935 | * Allocate stable and unstable together: |
| 2936 | * MAXSMP NODES_SHIFT 10 will use 16kB. |
| 2937 | */ |
Joe Perches | bafe1e1 | 2013-11-12 15:07:10 -0800 | [diff] [blame] | 2938 | buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), |
| 2939 | GFP_KERNEL); |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2940 | /* Let us assume that RB_ROOT is NULL is zero */ |
| 2941 | if (!buf) |
| 2942 | err = -ENOMEM; |
| 2943 | else { |
| 2944 | root_stable_tree = buf; |
| 2945 | root_unstable_tree = buf + nr_node_ids; |
| 2946 | /* Stable tree is empty but not the unstable */ |
| 2947 | root_unstable_tree[0] = one_unstable_tree[0]; |
| 2948 | } |
| 2949 | } |
| 2950 | if (!err) { |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2951 | ksm_merge_across_nodes = knob; |
Hugh Dickins | ef53d16 | 2013-02-22 16:36:12 -0800 | [diff] [blame] | 2952 | ksm_nr_node_ids = knob ? 1 : nr_node_ids; |
| 2953 | } |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 2954 | } |
| 2955 | mutex_unlock(&ksm_thread_mutex); |
| 2956 | |
| 2957 | return err ? err : count; |
| 2958 | } |
| 2959 | KSM_ATTR(merge_across_nodes); |
| 2960 | #endif |
| 2961 | |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 2962 | static ssize_t use_zero_pages_show(struct kobject *kobj, |
| 2963 | struct kobj_attribute *attr, char *buf) |
| 2964 | { |
| 2965 | return sprintf(buf, "%u\n", ksm_use_zero_pages); |
| 2966 | } |
| 2967 | static ssize_t use_zero_pages_store(struct kobject *kobj, |
| 2968 | struct kobj_attribute *attr, |
| 2969 | const char *buf, size_t count) |
| 2970 | { |
| 2971 | int err; |
| 2972 | bool value; |
| 2973 | |
| 2974 | err = kstrtobool(buf, &value); |
| 2975 | if (err) |
| 2976 | return -EINVAL; |
| 2977 | |
| 2978 | ksm_use_zero_pages = value; |
| 2979 | |
| 2980 | return count; |
| 2981 | } |
| 2982 | KSM_ATTR(use_zero_pages); |
| 2983 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 2984 | static ssize_t max_page_sharing_show(struct kobject *kobj, |
| 2985 | struct kobj_attribute *attr, char *buf) |
| 2986 | { |
| 2987 | return sprintf(buf, "%u\n", ksm_max_page_sharing); |
| 2988 | } |
| 2989 | |
| 2990 | static ssize_t max_page_sharing_store(struct kobject *kobj, |
| 2991 | struct kobj_attribute *attr, |
| 2992 | const char *buf, size_t count) |
| 2993 | { |
| 2994 | int err; |
| 2995 | int knob; |
| 2996 | |
| 2997 | err = kstrtoint(buf, 10, &knob); |
| 2998 | if (err) |
| 2999 | return err; |
| 3000 | /* |
| 3001 | * When a KSM page is created it is shared by 2 mappings. This |
| 3002 | * being a signed comparison, it implicitly verifies it's not |
| 3003 | * negative. |
| 3004 | */ |
| 3005 | if (knob < 2) |
| 3006 | return -EINVAL; |
| 3007 | |
| 3008 | if (READ_ONCE(ksm_max_page_sharing) == knob) |
| 3009 | return count; |
| 3010 | |
| 3011 | mutex_lock(&ksm_thread_mutex); |
| 3012 | wait_while_offlining(); |
| 3013 | if (ksm_max_page_sharing != knob) { |
| 3014 | if (ksm_pages_shared || remove_all_stable_nodes()) |
| 3015 | err = -EBUSY; |
| 3016 | else |
| 3017 | ksm_max_page_sharing = knob; |
| 3018 | } |
| 3019 | mutex_unlock(&ksm_thread_mutex); |
| 3020 | |
| 3021 | return err ? err : count; |
| 3022 | } |
| 3023 | KSM_ATTR(max_page_sharing); |
| 3024 | |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 3025 | static ssize_t pages_shared_show(struct kobject *kobj, |
| 3026 | struct kobj_attribute *attr, char *buf) |
| 3027 | { |
| 3028 | return sprintf(buf, "%lu\n", ksm_pages_shared); |
| 3029 | } |
| 3030 | KSM_ATTR_RO(pages_shared); |
| 3031 | |
| 3032 | static ssize_t pages_sharing_show(struct kobject *kobj, |
| 3033 | struct kobj_attribute *attr, char *buf) |
| 3034 | { |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 3035 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 3036 | } |
| 3037 | KSM_ATTR_RO(pages_sharing); |
| 3038 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 3039 | static ssize_t pages_unshared_show(struct kobject *kobj, |
| 3040 | struct kobj_attribute *attr, char *buf) |
| 3041 | { |
| 3042 | return sprintf(buf, "%lu\n", ksm_pages_unshared); |
| 3043 | } |
| 3044 | KSM_ATTR_RO(pages_unshared); |
| 3045 | |
| 3046 | static ssize_t pages_volatile_show(struct kobject *kobj, |
| 3047 | struct kobj_attribute *attr, char *buf) |
| 3048 | { |
| 3049 | long ksm_pages_volatile; |
| 3050 | |
| 3051 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared |
| 3052 | - ksm_pages_sharing - ksm_pages_unshared; |
| 3053 | /* |
| 3054 | * It was not worth any locking to calculate that statistic, |
| 3055 | * but it might therefore sometimes be negative: conceal that. |
| 3056 | */ |
| 3057 | if (ksm_pages_volatile < 0) |
| 3058 | ksm_pages_volatile = 0; |
| 3059 | return sprintf(buf, "%ld\n", ksm_pages_volatile); |
| 3060 | } |
| 3061 | KSM_ATTR_RO(pages_volatile); |
| 3062 | |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 3063 | static ssize_t stable_node_dups_show(struct kobject *kobj, |
| 3064 | struct kobj_attribute *attr, char *buf) |
| 3065 | { |
| 3066 | return sprintf(buf, "%lu\n", ksm_stable_node_dups); |
| 3067 | } |
| 3068 | KSM_ATTR_RO(stable_node_dups); |
| 3069 | |
| 3070 | static ssize_t stable_node_chains_show(struct kobject *kobj, |
| 3071 | struct kobj_attribute *attr, char *buf) |
| 3072 | { |
| 3073 | return sprintf(buf, "%lu\n", ksm_stable_node_chains); |
| 3074 | } |
| 3075 | KSM_ATTR_RO(stable_node_chains); |
| 3076 | |
| 3077 | static ssize_t |
| 3078 | stable_node_chains_prune_millisecs_show(struct kobject *kobj, |
| 3079 | struct kobj_attribute *attr, |
| 3080 | char *buf) |
| 3081 | { |
| 3082 | return sprintf(buf, "%u\n", ksm_stable_node_chains_prune_millisecs); |
| 3083 | } |
| 3084 | |
| 3085 | static ssize_t |
| 3086 | stable_node_chains_prune_millisecs_store(struct kobject *kobj, |
| 3087 | struct kobj_attribute *attr, |
| 3088 | const char *buf, size_t count) |
| 3089 | { |
| 3090 | unsigned long msecs; |
| 3091 | int err; |
| 3092 | |
| 3093 | err = kstrtoul(buf, 10, &msecs); |
| 3094 | if (err || msecs > UINT_MAX) |
| 3095 | return -EINVAL; |
| 3096 | |
| 3097 | ksm_stable_node_chains_prune_millisecs = msecs; |
| 3098 | |
| 3099 | return count; |
| 3100 | } |
| 3101 | KSM_ATTR(stable_node_chains_prune_millisecs); |
| 3102 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 3103 | static ssize_t full_scans_show(struct kobject *kobj, |
| 3104 | struct kobj_attribute *attr, char *buf) |
| 3105 | { |
| 3106 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); |
| 3107 | } |
| 3108 | KSM_ATTR_RO(full_scans); |
| 3109 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3110 | static struct attribute *ksm_attrs[] = { |
| 3111 | &sleep_millisecs_attr.attr, |
| 3112 | &pages_to_scan_attr.attr, |
| 3113 | &run_attr.attr, |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 3114 | &pages_shared_attr.attr, |
| 3115 | &pages_sharing_attr.attr, |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 3116 | &pages_unshared_attr.attr, |
| 3117 | &pages_volatile_attr.attr, |
| 3118 | &full_scans_attr.attr, |
Petr Holasek | 90bd6fd | 2013-02-22 16:35:00 -0800 | [diff] [blame] | 3119 | #ifdef CONFIG_NUMA |
| 3120 | &merge_across_nodes_attr.attr, |
| 3121 | #endif |
Andrea Arcangeli | 2c653d0 | 2017-07-06 15:36:55 -0700 | [diff] [blame] | 3122 | &max_page_sharing_attr.attr, |
| 3123 | &stable_node_chains_attr.attr, |
| 3124 | &stable_node_dups_attr.attr, |
| 3125 | &stable_node_chains_prune_millisecs_attr.attr, |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 3126 | &use_zero_pages_attr.attr, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3127 | NULL, |
| 3128 | }; |
| 3129 | |
Arvind Yadav | f907c26 | 2017-09-06 16:21:53 -0700 | [diff] [blame] | 3130 | static const struct attribute_group ksm_attr_group = { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3131 | .attrs = ksm_attrs, |
| 3132 | .name = "ksm", |
| 3133 | }; |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 3134 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3135 | |
| 3136 | static int __init ksm_init(void) |
| 3137 | { |
| 3138 | struct task_struct *ksm_thread; |
| 3139 | int err; |
| 3140 | |
Claudio Imbrenda | e86c59b | 2017-02-24 14:55:39 -0800 | [diff] [blame] | 3141 | /* The correct value depends on page size and endianness */ |
| 3142 | zero_checksum = calc_checksum(ZERO_PAGE(0)); |
| 3143 | /* Default to false for backwards compatibility */ |
| 3144 | ksm_use_zero_pages = false; |
| 3145 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3146 | err = ksm_slab_init(); |
| 3147 | if (err) |
| 3148 | goto out; |
| 3149 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3150 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
| 3151 | if (IS_ERR(ksm_thread)) { |
Paul McQuade | 25acde3 | 2014-10-09 15:29:09 -0700 | [diff] [blame] | 3152 | pr_err("ksm: creating kthread failed\n"); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3153 | err = PTR_ERR(ksm_thread); |
Lai Jiangshan | d9f8984 | 2010-08-09 17:20:02 -0700 | [diff] [blame] | 3154 | goto out_free; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3155 | } |
| 3156 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 3157 | #ifdef CONFIG_SYSFS |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3158 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
| 3159 | if (err) { |
Paul McQuade | 25acde3 | 2014-10-09 15:29:09 -0700 | [diff] [blame] | 3160 | pr_err("ksm: register sysfs failed\n"); |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 3161 | kthread_stop(ksm_thread); |
Lai Jiangshan | d9f8984 | 2010-08-09 17:20:02 -0700 | [diff] [blame] | 3162 | goto out_free; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3163 | } |
Hugh Dickins | c73602a | 2009-10-07 16:32:22 -0700 | [diff] [blame] | 3164 | #else |
| 3165 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ |
| 3166 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 3167 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3168 | |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 3169 | #ifdef CONFIG_MEMORY_HOTREMOVE |
Hugh Dickins | ef4d43a | 2013-02-22 16:35:16 -0800 | [diff] [blame] | 3170 | /* There is no significance to this priority 100 */ |
Hugh Dickins | 62b61f6 | 2009-12-14 17:59:33 -0800 | [diff] [blame] | 3171 | hotplug_memory_notifier(ksm_memory_callback, 100); |
| 3172 | #endif |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3173 | return 0; |
| 3174 | |
Lai Jiangshan | d9f8984 | 2010-08-09 17:20:02 -0700 | [diff] [blame] | 3175 | out_free: |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 3176 | ksm_slab_free(); |
| 3177 | out: |
| 3178 | return err; |
| 3179 | } |
Paul Gortmaker | a64fb3c | 2014-01-23 15:53:30 -0800 | [diff] [blame] | 3180 | subsys_initcall(ksm_init); |