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> |
| 22 | #include <linux/rwsem.h> |
| 23 | #include <linux/pagemap.h> |
| 24 | #include <linux/rmap.h> |
| 25 | #include <linux/spinlock.h> |
| 26 | #include <linux/jhash.h> |
| 27 | #include <linux/delay.h> |
| 28 | #include <linux/kthread.h> |
| 29 | #include <linux/wait.h> |
| 30 | #include <linux/slab.h> |
| 31 | #include <linux/rbtree.h> |
| 32 | #include <linux/mmu_notifier.h> |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 33 | #include <linux/swap.h> |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 34 | #include <linux/ksm.h> |
| 35 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 36 | #include <asm/tlbflush.h> |
| 37 | |
| 38 | /* |
| 39 | * A few notes about the KSM scanning process, |
| 40 | * to make it easier to understand the data structures below: |
| 41 | * |
| 42 | * In order to reduce excessive scanning, KSM sorts the memory pages by their |
| 43 | * contents into a data structure that holds pointers to the pages' locations. |
| 44 | * |
| 45 | * Since the contents of the pages may change at any moment, KSM cannot just |
| 46 | * insert the pages into a normal sorted tree and expect it to find anything. |
| 47 | * Therefore KSM uses two data structures - the stable and the unstable tree. |
| 48 | * |
| 49 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted |
| 50 | * by their contents. Because each such page is write-protected, searching on |
| 51 | * this tree is fully assured to be working (except when pages are unmapped), |
| 52 | * and therefore this tree is called the stable tree. |
| 53 | * |
| 54 | * In addition to the stable tree, KSM uses a second data structure called the |
| 55 | * unstable tree: this tree holds pointers to pages which have been found to |
| 56 | * be "unchanged for a period of time". The unstable tree sorts these pages |
| 57 | * by their contents, but since they are not write-protected, KSM cannot rely |
| 58 | * upon the unstable tree to work correctly - the unstable tree is liable to |
| 59 | * be corrupted as its contents are modified, and so it is called unstable. |
| 60 | * |
| 61 | * KSM solves this problem by several techniques: |
| 62 | * |
| 63 | * 1) The unstable tree is flushed every time KSM completes scanning all |
| 64 | * memory areas, and then the tree is rebuilt again from the beginning. |
| 65 | * 2) KSM will only insert into the unstable tree, pages whose hash value |
| 66 | * has not changed since the previous scan of all memory areas. |
| 67 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the |
| 68 | * colors of the nodes and not on their contents, assuring that even when |
| 69 | * the tree gets "corrupted" it won't get out of balance, so scanning time |
| 70 | * remains the same (also, searching and inserting nodes in an rbtree uses |
| 71 | * the same algorithm, so we have no overhead when we flush and rebuild). |
| 72 | * 4) KSM never flushes the stable tree, which means that even if it were to |
| 73 | * take 10 attempts to find a page in the unstable tree, once it is found, |
| 74 | * it is secured in the stable tree. (When we scan a new page, we first |
| 75 | * compare it against the stable tree, and then against the unstable tree.) |
| 76 | */ |
| 77 | |
| 78 | /** |
| 79 | * struct mm_slot - ksm information per mm that is being scanned |
| 80 | * @link: link to the mm_slots hash list |
| 81 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head |
| 82 | * @rmap_list: head for this mm_slot's list of rmap_items |
| 83 | * @mm: the mm that this information is valid for |
| 84 | */ |
| 85 | struct mm_slot { |
| 86 | struct hlist_node link; |
| 87 | struct list_head mm_list; |
| 88 | struct list_head rmap_list; |
| 89 | struct mm_struct *mm; |
| 90 | }; |
| 91 | |
| 92 | /** |
| 93 | * struct ksm_scan - cursor for scanning |
| 94 | * @mm_slot: the current mm_slot we are scanning |
| 95 | * @address: the next address inside that to be scanned |
| 96 | * @rmap_item: the current rmap that we are scanning inside the rmap_list |
| 97 | * @seqnr: count of completed full scans (needed when removing unstable node) |
| 98 | * |
| 99 | * There is only the one ksm_scan instance of this cursor structure. |
| 100 | */ |
| 101 | struct ksm_scan { |
| 102 | struct mm_slot *mm_slot; |
| 103 | unsigned long address; |
| 104 | struct rmap_item *rmap_item; |
| 105 | unsigned long seqnr; |
| 106 | }; |
| 107 | |
| 108 | /** |
| 109 | * struct rmap_item - reverse mapping item for virtual addresses |
| 110 | * @link: link into mm_slot's rmap_list (rmap_list is per mm) |
| 111 | * @mm: the memory structure this rmap_item is pointing into |
| 112 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) |
| 113 | * @oldchecksum: previous checksum of the page at that virtual address |
| 114 | * @node: rb_node of this rmap_item in either unstable or stable tree |
| 115 | * @next: next rmap_item hanging off the same node of the stable tree |
| 116 | * @prev: previous rmap_item hanging off the same node of the stable tree |
| 117 | */ |
| 118 | struct rmap_item { |
| 119 | struct list_head link; |
| 120 | struct mm_struct *mm; |
| 121 | unsigned long address; /* + low bits used for flags below */ |
| 122 | union { |
| 123 | unsigned int oldchecksum; /* when unstable */ |
| 124 | struct rmap_item *next; /* when stable */ |
| 125 | }; |
| 126 | union { |
| 127 | struct rb_node node; /* when tree node */ |
| 128 | struct rmap_item *prev; /* in stable list */ |
| 129 | }; |
| 130 | }; |
| 131 | |
| 132 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ |
| 133 | #define NODE_FLAG 0x100 /* is a node of unstable or stable tree */ |
| 134 | #define STABLE_FLAG 0x200 /* is a node or list item of stable tree */ |
| 135 | |
| 136 | /* The stable and unstable tree heads */ |
| 137 | static struct rb_root root_stable_tree = RB_ROOT; |
| 138 | static struct rb_root root_unstable_tree = RB_ROOT; |
| 139 | |
| 140 | #define MM_SLOTS_HASH_HEADS 1024 |
| 141 | static struct hlist_head *mm_slots_hash; |
| 142 | |
| 143 | static struct mm_slot ksm_mm_head = { |
| 144 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), |
| 145 | }; |
| 146 | static struct ksm_scan ksm_scan = { |
| 147 | .mm_slot = &ksm_mm_head, |
| 148 | }; |
| 149 | |
| 150 | static struct kmem_cache *rmap_item_cache; |
| 151 | static struct kmem_cache *mm_slot_cache; |
| 152 | |
| 153 | /* The number of nodes in the stable tree */ |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 154 | static unsigned long ksm_pages_shared; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 155 | |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 156 | /* The number of page slots additionally sharing those nodes */ |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 157 | static unsigned long ksm_pages_sharing; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 158 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 159 | /* The number of nodes in the unstable tree */ |
| 160 | static unsigned long ksm_pages_unshared; |
| 161 | |
| 162 | /* The number of rmap_items in use: to calculate pages_volatile */ |
| 163 | static unsigned long ksm_rmap_items; |
| 164 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 165 | /* Limit on the number of unswappable pages used */ |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 166 | static unsigned long ksm_max_kernel_pages; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 167 | |
| 168 | /* Number of pages ksmd should scan in one batch */ |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 169 | static unsigned int ksm_thread_pages_to_scan = 100; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 170 | |
| 171 | /* Milliseconds ksmd should sleep between batches */ |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 172 | static unsigned int ksm_thread_sleep_millisecs = 20; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 173 | |
| 174 | #define KSM_RUN_STOP 0 |
| 175 | #define KSM_RUN_MERGE 1 |
| 176 | #define KSM_RUN_UNMERGE 2 |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 177 | static unsigned int ksm_run = KSM_RUN_STOP; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 178 | |
| 179 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); |
| 180 | static DEFINE_MUTEX(ksm_thread_mutex); |
| 181 | static DEFINE_SPINLOCK(ksm_mmlist_lock); |
| 182 | |
| 183 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ |
| 184 | sizeof(struct __struct), __alignof__(struct __struct),\ |
| 185 | (__flags), NULL) |
| 186 | |
| 187 | static int __init ksm_slab_init(void) |
| 188 | { |
| 189 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); |
| 190 | if (!rmap_item_cache) |
| 191 | goto out; |
| 192 | |
| 193 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
| 194 | if (!mm_slot_cache) |
| 195 | goto out_free; |
| 196 | |
| 197 | return 0; |
| 198 | |
| 199 | out_free: |
| 200 | kmem_cache_destroy(rmap_item_cache); |
| 201 | out: |
| 202 | return -ENOMEM; |
| 203 | } |
| 204 | |
| 205 | static void __init ksm_slab_free(void) |
| 206 | { |
| 207 | kmem_cache_destroy(mm_slot_cache); |
| 208 | kmem_cache_destroy(rmap_item_cache); |
| 209 | mm_slot_cache = NULL; |
| 210 | } |
| 211 | |
| 212 | static inline struct rmap_item *alloc_rmap_item(void) |
| 213 | { |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 214 | struct rmap_item *rmap_item; |
| 215 | |
| 216 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); |
| 217 | if (rmap_item) |
| 218 | ksm_rmap_items++; |
| 219 | return rmap_item; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 220 | } |
| 221 | |
| 222 | static inline void free_rmap_item(struct rmap_item *rmap_item) |
| 223 | { |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 224 | ksm_rmap_items--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 225 | rmap_item->mm = NULL; /* debug safety */ |
| 226 | kmem_cache_free(rmap_item_cache, rmap_item); |
| 227 | } |
| 228 | |
| 229 | static inline struct mm_slot *alloc_mm_slot(void) |
| 230 | { |
| 231 | if (!mm_slot_cache) /* initialization failed */ |
| 232 | return NULL; |
| 233 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); |
| 234 | } |
| 235 | |
| 236 | static inline void free_mm_slot(struct mm_slot *mm_slot) |
| 237 | { |
| 238 | kmem_cache_free(mm_slot_cache, mm_slot); |
| 239 | } |
| 240 | |
| 241 | static int __init mm_slots_hash_init(void) |
| 242 | { |
| 243 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), |
| 244 | GFP_KERNEL); |
| 245 | if (!mm_slots_hash) |
| 246 | return -ENOMEM; |
| 247 | return 0; |
| 248 | } |
| 249 | |
| 250 | static void __init mm_slots_hash_free(void) |
| 251 | { |
| 252 | kfree(mm_slots_hash); |
| 253 | } |
| 254 | |
| 255 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
| 256 | { |
| 257 | struct mm_slot *mm_slot; |
| 258 | struct hlist_head *bucket; |
| 259 | struct hlist_node *node; |
| 260 | |
| 261 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) |
| 262 | % MM_SLOTS_HASH_HEADS]; |
| 263 | hlist_for_each_entry(mm_slot, node, bucket, link) { |
| 264 | if (mm == mm_slot->mm) |
| 265 | return mm_slot; |
| 266 | } |
| 267 | return NULL; |
| 268 | } |
| 269 | |
| 270 | static void insert_to_mm_slots_hash(struct mm_struct *mm, |
| 271 | struct mm_slot *mm_slot) |
| 272 | { |
| 273 | struct hlist_head *bucket; |
| 274 | |
| 275 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) |
| 276 | % MM_SLOTS_HASH_HEADS]; |
| 277 | mm_slot->mm = mm; |
| 278 | INIT_LIST_HEAD(&mm_slot->rmap_list); |
| 279 | hlist_add_head(&mm_slot->link, bucket); |
| 280 | } |
| 281 | |
| 282 | static inline int in_stable_tree(struct rmap_item *rmap_item) |
| 283 | { |
| 284 | return rmap_item->address & STABLE_FLAG; |
| 285 | } |
| 286 | |
| 287 | /* |
Hugh Dickins | a913e18 | 2009-09-21 17:02:26 -0700 | [diff] [blame] | 288 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's |
| 289 | * page tables after it has passed through ksm_exit() - which, if necessary, |
| 290 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set |
| 291 | * a special flag: they can just back out as soon as mm_users goes to zero. |
| 292 | * ksm_test_exit() is used throughout to make this test for exit: in some |
| 293 | * places for correctness, in some places just to avoid unnecessary work. |
| 294 | */ |
| 295 | static inline bool ksm_test_exit(struct mm_struct *mm) |
| 296 | { |
| 297 | return atomic_read(&mm->mm_users) == 0; |
| 298 | } |
| 299 | |
| 300 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 301 | * We use break_ksm to break COW on a ksm page: it's a stripped down |
| 302 | * |
| 303 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) |
| 304 | * put_page(page); |
| 305 | * |
| 306 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, |
| 307 | * in case the application has unmapped and remapped mm,addr meanwhile. |
| 308 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP |
| 309 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. |
| 310 | */ |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 311 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 312 | { |
| 313 | struct page *page; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 314 | int ret = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 315 | |
| 316 | do { |
| 317 | cond_resched(); |
| 318 | page = follow_page(vma, addr, FOLL_GET); |
| 319 | if (!page) |
| 320 | break; |
| 321 | if (PageKsm(page)) |
| 322 | ret = handle_mm_fault(vma->vm_mm, vma, addr, |
| 323 | FAULT_FLAG_WRITE); |
| 324 | else |
| 325 | ret = VM_FAULT_WRITE; |
| 326 | put_page(page); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 327 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
| 328 | /* |
| 329 | * We must loop because handle_mm_fault() may back out if there's |
| 330 | * any difficulty e.g. if pte accessed bit gets updated concurrently. |
| 331 | * |
| 332 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that |
| 333 | * COW has been broken, even if the vma does not permit VM_WRITE; |
| 334 | * but note that a concurrent fault might break PageKsm for us. |
| 335 | * |
| 336 | * VM_FAULT_SIGBUS could occur if we race with truncation of the |
| 337 | * backing file, which also invalidates anonymous pages: that's |
| 338 | * okay, that truncation will have unmapped the PageKsm for us. |
| 339 | * |
| 340 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting |
| 341 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the |
| 342 | * current task has TIF_MEMDIE set, and will be OOM killed on return |
| 343 | * to user; and ksmd, having no mm, would never be chosen for that. |
| 344 | * |
| 345 | * But if the mm is in a limited mem_cgroup, then the fault may fail |
| 346 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and |
| 347 | * even ksmd can fail in this way - though it's usually breaking ksm |
| 348 | * just to undo a merge it made a moment before, so unlikely to oom. |
| 349 | * |
| 350 | * That's a pity: we might therefore have more kernel pages allocated |
| 351 | * than we're counting as nodes in the stable tree; but ksm_do_scan |
| 352 | * will retry to break_cow on each pass, so should recover the page |
| 353 | * in due course. The important thing is to not let VM_MERGEABLE |
| 354 | * be cleared while any such pages might remain in the area. |
| 355 | */ |
| 356 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 357 | } |
| 358 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 359 | static void break_cow(struct rmap_item *rmap_item) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 360 | { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 361 | struct mm_struct *mm = rmap_item->mm; |
| 362 | unsigned long addr = rmap_item->address; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 363 | struct vm_area_struct *vma; |
| 364 | |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 365 | down_read(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 366 | if (ksm_test_exit(mm)) |
| 367 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 368 | vma = find_vma(mm, addr); |
| 369 | if (!vma || vma->vm_start > addr) |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 370 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 371 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 372 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 373 | break_ksm(vma, addr); |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 374 | out: |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 375 | up_read(&mm->mmap_sem); |
| 376 | } |
| 377 | |
| 378 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) |
| 379 | { |
| 380 | struct mm_struct *mm = rmap_item->mm; |
| 381 | unsigned long addr = rmap_item->address; |
| 382 | struct vm_area_struct *vma; |
| 383 | struct page *page; |
| 384 | |
| 385 | down_read(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 386 | if (ksm_test_exit(mm)) |
| 387 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 388 | vma = find_vma(mm, addr); |
| 389 | if (!vma || vma->vm_start > addr) |
| 390 | goto out; |
| 391 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
| 392 | goto out; |
| 393 | |
| 394 | page = follow_page(vma, addr, FOLL_GET); |
| 395 | if (!page) |
| 396 | goto out; |
| 397 | if (PageAnon(page)) { |
| 398 | flush_anon_page(vma, page, addr); |
| 399 | flush_dcache_page(page); |
| 400 | } else { |
| 401 | put_page(page); |
| 402 | out: page = NULL; |
| 403 | } |
| 404 | up_read(&mm->mmap_sem); |
| 405 | return page; |
| 406 | } |
| 407 | |
| 408 | /* |
| 409 | * get_ksm_page: checks if the page at the virtual address in rmap_item |
| 410 | * is still PageKsm, in which case we can trust the content of the page, |
| 411 | * and it returns the gotten page; but NULL if the page has been zapped. |
| 412 | */ |
| 413 | static struct page *get_ksm_page(struct rmap_item *rmap_item) |
| 414 | { |
| 415 | struct page *page; |
| 416 | |
| 417 | page = get_mergeable_page(rmap_item); |
| 418 | if (page && !PageKsm(page)) { |
| 419 | put_page(page); |
| 420 | page = NULL; |
| 421 | } |
| 422 | return page; |
| 423 | } |
| 424 | |
| 425 | /* |
| 426 | * Removing rmap_item from stable or unstable tree. |
| 427 | * This function will clean the information from the stable/unstable tree. |
| 428 | */ |
| 429 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) |
| 430 | { |
| 431 | if (in_stable_tree(rmap_item)) { |
| 432 | struct rmap_item *next_item = rmap_item->next; |
| 433 | |
| 434 | if (rmap_item->address & NODE_FLAG) { |
| 435 | if (next_item) { |
| 436 | rb_replace_node(&rmap_item->node, |
| 437 | &next_item->node, |
| 438 | &root_stable_tree); |
| 439 | next_item->address |= NODE_FLAG; |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 440 | ksm_pages_sharing--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 441 | } else { |
| 442 | rb_erase(&rmap_item->node, &root_stable_tree); |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 443 | ksm_pages_shared--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 444 | } |
| 445 | } else { |
| 446 | struct rmap_item *prev_item = rmap_item->prev; |
| 447 | |
| 448 | BUG_ON(prev_item->next != rmap_item); |
| 449 | prev_item->next = next_item; |
| 450 | if (next_item) { |
| 451 | BUG_ON(next_item->prev != rmap_item); |
| 452 | next_item->prev = rmap_item->prev; |
| 453 | } |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 454 | ksm_pages_sharing--; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 455 | } |
| 456 | |
| 457 | rmap_item->next = NULL; |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 458 | rmap_item->address &= PAGE_MASK; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 459 | |
| 460 | } else if (rmap_item->address & NODE_FLAG) { |
| 461 | unsigned char age; |
| 462 | /* |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 463 | * Usually ksmd can and must skip the rb_erase, because |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 464 | * root_unstable_tree was already reset to RB_ROOT. |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 465 | * But be careful when an mm is exiting: do the rb_erase |
| 466 | * if this rmap_item was inserted by this scan, rather |
| 467 | * than left over from before. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 468 | */ |
| 469 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 470 | BUG_ON(age > 1); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 471 | if (!age) |
| 472 | rb_erase(&rmap_item->node, &root_unstable_tree); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 473 | |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 474 | ksm_pages_unshared--; |
| 475 | rmap_item->address &= PAGE_MASK; |
| 476 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 477 | |
| 478 | cond_resched(); /* we're called from many long loops */ |
| 479 | } |
| 480 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 481 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
| 482 | struct list_head *cur) |
| 483 | { |
| 484 | struct rmap_item *rmap_item; |
| 485 | |
| 486 | while (cur != &mm_slot->rmap_list) { |
| 487 | rmap_item = list_entry(cur, struct rmap_item, link); |
| 488 | cur = cur->next; |
| 489 | remove_rmap_item_from_tree(rmap_item); |
| 490 | list_del(&rmap_item->link); |
| 491 | free_rmap_item(rmap_item); |
| 492 | } |
| 493 | } |
| 494 | |
| 495 | /* |
| 496 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather |
| 497 | * than check every pte of a given vma, the locking doesn't quite work for |
| 498 | * that - an rmap_item is assigned to the stable tree after inserting ksm |
| 499 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing |
| 500 | * rmap_items from parent to child at fork time (so as not to waste time |
| 501 | * if exit comes before the next scan reaches it). |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 502 | * |
| 503 | * Similarly, although we'd like to remove rmap_items (so updating counts |
| 504 | * and freeing memory) when unmerging an area, it's easier to leave that |
| 505 | * to the next pass of ksmd - consider, for example, how ksmd might be |
| 506 | * 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] | 507 | */ |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 508 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
| 509 | unsigned long start, unsigned long end) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 510 | { |
| 511 | unsigned long addr; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 512 | int err = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 513 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 514 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 515 | if (ksm_test_exit(vma->vm_mm)) |
| 516 | break; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 517 | if (signal_pending(current)) |
| 518 | err = -ERESTARTSYS; |
| 519 | else |
| 520 | err = break_ksm(vma, addr); |
| 521 | } |
| 522 | return err; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 523 | } |
| 524 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 525 | #ifdef CONFIG_SYSFS |
| 526 | /* |
| 527 | * Only called through the sysfs control interface: |
| 528 | */ |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 529 | static int unmerge_and_remove_all_rmap_items(void) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 530 | { |
| 531 | struct mm_slot *mm_slot; |
| 532 | struct mm_struct *mm; |
| 533 | struct vm_area_struct *vma; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 534 | int err = 0; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 535 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 536 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 537 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 538 | struct mm_slot, mm_list); |
| 539 | spin_unlock(&ksm_mmlist_lock); |
| 540 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 541 | for (mm_slot = ksm_scan.mm_slot; |
| 542 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 543 | mm = mm_slot->mm; |
| 544 | down_read(&mm->mmap_sem); |
| 545 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 546 | if (ksm_test_exit(mm)) |
| 547 | break; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 548 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
| 549 | continue; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 550 | err = unmerge_ksm_pages(vma, |
| 551 | vma->vm_start, vma->vm_end); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 552 | if (err) |
| 553 | goto error; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 554 | } |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 555 | |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 556 | remove_trailing_rmap_items(mm_slot, mm_slot->rmap_list.next); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 557 | |
| 558 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 559 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 560 | struct mm_slot, mm_list); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 561 | if (ksm_test_exit(mm)) { |
| 562 | hlist_del(&mm_slot->link); |
| 563 | list_del(&mm_slot->mm_list); |
| 564 | spin_unlock(&ksm_mmlist_lock); |
| 565 | |
| 566 | free_mm_slot(mm_slot); |
| 567 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
| 568 | up_read(&mm->mmap_sem); |
| 569 | mmdrop(mm); |
| 570 | } else { |
| 571 | spin_unlock(&ksm_mmlist_lock); |
| 572 | up_read(&mm->mmap_sem); |
| 573 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 574 | } |
| 575 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 576 | ksm_scan.seqnr = 0; |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 577 | return 0; |
| 578 | |
| 579 | error: |
| 580 | up_read(&mm->mmap_sem); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 581 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 582 | ksm_scan.mm_slot = &ksm_mm_head; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 583 | spin_unlock(&ksm_mmlist_lock); |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 584 | return err; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 585 | } |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 586 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 587 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 588 | static u32 calc_checksum(struct page *page) |
| 589 | { |
| 590 | u32 checksum; |
| 591 | void *addr = kmap_atomic(page, KM_USER0); |
| 592 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); |
| 593 | kunmap_atomic(addr, KM_USER0); |
| 594 | return checksum; |
| 595 | } |
| 596 | |
| 597 | static int memcmp_pages(struct page *page1, struct page *page2) |
| 598 | { |
| 599 | char *addr1, *addr2; |
| 600 | int ret; |
| 601 | |
| 602 | addr1 = kmap_atomic(page1, KM_USER0); |
| 603 | addr2 = kmap_atomic(page2, KM_USER1); |
| 604 | ret = memcmp(addr1, addr2, PAGE_SIZE); |
| 605 | kunmap_atomic(addr2, KM_USER1); |
| 606 | kunmap_atomic(addr1, KM_USER0); |
| 607 | return ret; |
| 608 | } |
| 609 | |
| 610 | static inline int pages_identical(struct page *page1, struct page *page2) |
| 611 | { |
| 612 | return !memcmp_pages(page1, page2); |
| 613 | } |
| 614 | |
| 615 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, |
| 616 | pte_t *orig_pte) |
| 617 | { |
| 618 | struct mm_struct *mm = vma->vm_mm; |
| 619 | unsigned long addr; |
| 620 | pte_t *ptep; |
| 621 | spinlock_t *ptl; |
| 622 | int swapped; |
| 623 | int err = -EFAULT; |
| 624 | |
| 625 | addr = page_address_in_vma(page, vma); |
| 626 | if (addr == -EFAULT) |
| 627 | goto out; |
| 628 | |
| 629 | ptep = page_check_address(page, mm, addr, &ptl, 0); |
| 630 | if (!ptep) |
| 631 | goto out; |
| 632 | |
| 633 | if (pte_write(*ptep)) { |
| 634 | pte_t entry; |
| 635 | |
| 636 | swapped = PageSwapCache(page); |
| 637 | flush_cache_page(vma, addr, page_to_pfn(page)); |
| 638 | /* |
| 639 | * Ok this is tricky, when get_user_pages_fast() run it doesnt |
| 640 | * take any lock, therefore the check that we are going to make |
| 641 | * with the pagecount against the mapcount is racey and |
| 642 | * O_DIRECT can happen right after the check. |
| 643 | * So we clear the pte and flush the tlb before the check |
| 644 | * this assure us that no O_DIRECT can happen after the check |
| 645 | * or in the middle of the check. |
| 646 | */ |
| 647 | entry = ptep_clear_flush(vma, addr, ptep); |
| 648 | /* |
| 649 | * Check that no O_DIRECT or similar I/O is in progress on the |
| 650 | * page |
| 651 | */ |
Hugh Dickins | 31e855e | 2009-12-14 17:59:17 -0800 | [diff] [blame] | 652 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 653 | set_pte_at_notify(mm, addr, ptep, entry); |
| 654 | goto out_unlock; |
| 655 | } |
| 656 | entry = pte_wrprotect(entry); |
| 657 | set_pte_at_notify(mm, addr, ptep, entry); |
| 658 | } |
| 659 | *orig_pte = *ptep; |
| 660 | err = 0; |
| 661 | |
| 662 | out_unlock: |
| 663 | pte_unmap_unlock(ptep, ptl); |
| 664 | out: |
| 665 | return err; |
| 666 | } |
| 667 | |
| 668 | /** |
| 669 | * replace_page - replace page in vma by new ksm page |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 670 | * @vma: vma that holds the pte pointing to page |
| 671 | * @page: the page we are replacing by kpage |
| 672 | * @kpage: the ksm page we replace page by |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 673 | * @orig_pte: the original value of the pte |
| 674 | * |
| 675 | * Returns 0 on success, -EFAULT on failure. |
| 676 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 677 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
| 678 | struct page *kpage, pte_t orig_pte) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 679 | { |
| 680 | struct mm_struct *mm = vma->vm_mm; |
| 681 | pgd_t *pgd; |
| 682 | pud_t *pud; |
| 683 | pmd_t *pmd; |
| 684 | pte_t *ptep; |
| 685 | spinlock_t *ptl; |
| 686 | unsigned long addr; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 687 | int err = -EFAULT; |
| 688 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 689 | addr = page_address_in_vma(page, vma); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 690 | if (addr == -EFAULT) |
| 691 | goto out; |
| 692 | |
| 693 | pgd = pgd_offset(mm, addr); |
| 694 | if (!pgd_present(*pgd)) |
| 695 | goto out; |
| 696 | |
| 697 | pud = pud_offset(pgd, addr); |
| 698 | if (!pud_present(*pud)) |
| 699 | goto out; |
| 700 | |
| 701 | pmd = pmd_offset(pud, addr); |
| 702 | if (!pmd_present(*pmd)) |
| 703 | goto out; |
| 704 | |
| 705 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
| 706 | if (!pte_same(*ptep, orig_pte)) { |
| 707 | pte_unmap_unlock(ptep, ptl); |
| 708 | goto out; |
| 709 | } |
| 710 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 711 | get_page(kpage); |
| 712 | page_add_ksm_rmap(kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 713 | |
| 714 | flush_cache_page(vma, addr, pte_pfn(*ptep)); |
| 715 | ptep_clear_flush(vma, addr, ptep); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 716 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 717 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 718 | page_remove_rmap(page); |
| 719 | put_page(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 720 | |
| 721 | pte_unmap_unlock(ptep, ptl); |
| 722 | err = 0; |
| 723 | out: |
| 724 | return err; |
| 725 | } |
| 726 | |
| 727 | /* |
| 728 | * 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^] | 729 | * @vma: the vma that holds the pte pointing to page |
| 730 | * @page: the PageAnon page that we want to replace with kpage |
| 731 | * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap |
| 732 | * will make PageKsm) that we want to map instead of page |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 733 | * |
| 734 | * This function returns 0 if the pages were merged, -EFAULT otherwise. |
| 735 | */ |
| 736 | static int try_to_merge_one_page(struct vm_area_struct *vma, |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 737 | struct page *page, struct page *kpage) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 738 | { |
| 739 | pte_t orig_pte = __pte(0); |
| 740 | int err = -EFAULT; |
| 741 | |
| 742 | if (!(vma->vm_flags & VM_MERGEABLE)) |
| 743 | goto out; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 744 | if (!PageAnon(page)) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 745 | goto out; |
| 746 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 747 | /* |
| 748 | * We need the page lock to read a stable PageSwapCache in |
| 749 | * write_protect_page(). We use trylock_page() instead of |
| 750 | * lock_page() because we don't want to wait here - we |
| 751 | * prefer to continue scanning and merging different pages, |
| 752 | * then come back to this page when it is unlocked. |
| 753 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 754 | if (!trylock_page(page)) |
Hugh Dickins | 31e855e | 2009-12-14 17:59:17 -0800 | [diff] [blame] | 755 | goto out; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 756 | /* |
| 757 | * If this anonymous page is mapped only here, its pte may need |
| 758 | * to be write-protected. If it's mapped elsewhere, all of its |
| 759 | * ptes are necessarily already write-protected. But in either |
| 760 | * case, we need to lock and check page_count is not raised. |
| 761 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 762 | if (write_protect_page(vma, page, &orig_pte) == 0 && |
| 763 | pages_identical(page, kpage)) |
| 764 | err = replace_page(vma, page, kpage, orig_pte); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 765 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 766 | unlock_page(page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 767 | out: |
| 768 | return err; |
| 769 | } |
| 770 | |
| 771 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 772 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, |
| 773 | * 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^] | 774 | * |
| 775 | * This function returns 0 if the pages were merged, -EFAULT otherwise. |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 776 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 777 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
| 778 | struct page *page, struct page *kpage) |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 779 | { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 780 | struct mm_struct *mm = rmap_item->mm; |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 781 | struct vm_area_struct *vma; |
| 782 | int err = -EFAULT; |
| 783 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 784 | down_read(&mm->mmap_sem); |
| 785 | if (ksm_test_exit(mm)) |
| 786 | goto out; |
| 787 | vma = find_vma(mm, rmap_item->address); |
| 788 | if (!vma || vma->vm_start > rmap_item->address) |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 789 | goto out; |
| 790 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 791 | err = try_to_merge_one_page(vma, page, kpage); |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 792 | out: |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 793 | up_read(&mm->mmap_sem); |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 794 | return err; |
| 795 | } |
| 796 | |
| 797 | /* |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 798 | * try_to_merge_two_pages - take two identical pages and prepare them |
| 799 | * to be merged into one page. |
| 800 | * |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 801 | * This function returns the kpage if we successfully merged two identical |
| 802 | * pages into one ksm page, NULL otherwise. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 803 | * |
| 804 | * Note that this function allocates a new kernel page: if one of the pages |
| 805 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
| 806 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 807 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
| 808 | struct page *page, |
| 809 | struct rmap_item *tree_rmap_item, |
| 810 | struct page *tree_page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 811 | { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 812 | struct mm_struct *mm = rmap_item->mm; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 813 | struct vm_area_struct *vma; |
| 814 | struct page *kpage; |
| 815 | int err = -EFAULT; |
| 816 | |
| 817 | /* |
| 818 | * The number of nodes in the stable tree |
| 819 | * is the number of kernel pages that we hold. |
| 820 | */ |
| 821 | if (ksm_max_kernel_pages && |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 822 | ksm_max_kernel_pages <= ksm_pages_shared) |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 823 | return NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 824 | |
| 825 | kpage = alloc_page(GFP_HIGHUSER); |
| 826 | if (!kpage) |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 827 | return NULL; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 828 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 829 | down_read(&mm->mmap_sem); |
| 830 | if (ksm_test_exit(mm)) |
| 831 | goto up; |
| 832 | vma = find_vma(mm, rmap_item->address); |
| 833 | if (!vma || vma->vm_start > rmap_item->address) |
| 834 | goto up; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 835 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 836 | copy_user_highpage(kpage, page, rmap_item->address, vma); |
| 837 | err = try_to_merge_one_page(vma, page, kpage); |
| 838 | up: |
| 839 | up_read(&mm->mmap_sem); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 840 | |
| 841 | if (!err) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 842 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
| 843 | tree_page, kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 844 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 845 | * If that fails, we have a ksm page with only one pte |
| 846 | * pointing to it: so break it. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 847 | */ |
| 848 | if (err) |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 849 | break_cow(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 850 | } |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 851 | if (err) { |
| 852 | put_page(kpage); |
| 853 | kpage = NULL; |
| 854 | } |
| 855 | return kpage; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 856 | } |
| 857 | |
| 858 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 859 | * stable_tree_search - search for page inside the stable tree |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 860 | * |
| 861 | * This function checks if there is a page inside the stable tree |
| 862 | * with identical content to the page that we are scanning right now. |
| 863 | * |
| 864 | * This function return rmap_item pointer to the identical item if found, |
| 865 | * NULL otherwise. |
| 866 | */ |
| 867 | static struct rmap_item *stable_tree_search(struct page *page, |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 868 | struct page **tree_pagep) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 869 | { |
| 870 | struct rb_node *node = root_stable_tree.rb_node; |
| 871 | |
| 872 | while (node) { |
| 873 | struct rmap_item *tree_rmap_item, *next_rmap_item; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 874 | struct page *tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 875 | int ret; |
| 876 | |
| 877 | tree_rmap_item = rb_entry(node, struct rmap_item, node); |
| 878 | while (tree_rmap_item) { |
| 879 | BUG_ON(!in_stable_tree(tree_rmap_item)); |
| 880 | cond_resched(); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 881 | tree_page = get_ksm_page(tree_rmap_item); |
| 882 | if (tree_page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 883 | break; |
| 884 | next_rmap_item = tree_rmap_item->next; |
| 885 | remove_rmap_item_from_tree(tree_rmap_item); |
| 886 | tree_rmap_item = next_rmap_item; |
| 887 | } |
| 888 | if (!tree_rmap_item) |
| 889 | return NULL; |
| 890 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 891 | ret = memcmp_pages(page, tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 892 | |
| 893 | if (ret < 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 894 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 895 | node = node->rb_left; |
| 896 | } else if (ret > 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 897 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 898 | node = node->rb_right; |
| 899 | } else { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 900 | *tree_pagep = tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 901 | return tree_rmap_item; |
| 902 | } |
| 903 | } |
| 904 | |
| 905 | return NULL; |
| 906 | } |
| 907 | |
| 908 | /* |
| 909 | * stable_tree_insert - insert rmap_item pointing to new ksm page |
| 910 | * into the stable tree. |
| 911 | * |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 912 | * This function returns rmap_item if success, NULL otherwise. |
| 913 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 914 | static struct rmap_item *stable_tree_insert(struct page *kpage, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 915 | struct rmap_item *rmap_item) |
| 916 | { |
| 917 | struct rb_node **new = &root_stable_tree.rb_node; |
| 918 | struct rb_node *parent = NULL; |
| 919 | |
| 920 | while (*new) { |
| 921 | struct rmap_item *tree_rmap_item, *next_rmap_item; |
| 922 | struct page *tree_page; |
| 923 | int ret; |
| 924 | |
| 925 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
| 926 | while (tree_rmap_item) { |
| 927 | BUG_ON(!in_stable_tree(tree_rmap_item)); |
| 928 | cond_resched(); |
| 929 | tree_page = get_ksm_page(tree_rmap_item); |
| 930 | if (tree_page) |
| 931 | break; |
| 932 | next_rmap_item = tree_rmap_item->next; |
| 933 | remove_rmap_item_from_tree(tree_rmap_item); |
| 934 | tree_rmap_item = next_rmap_item; |
| 935 | } |
| 936 | if (!tree_rmap_item) |
| 937 | return NULL; |
| 938 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 939 | ret = memcmp_pages(kpage, tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 940 | put_page(tree_page); |
| 941 | |
| 942 | parent = *new; |
| 943 | if (ret < 0) |
| 944 | new = &parent->rb_left; |
| 945 | else if (ret > 0) |
| 946 | new = &parent->rb_right; |
| 947 | else { |
| 948 | /* |
| 949 | * It is not a bug that stable_tree_search() didn't |
| 950 | * find this node: because at that time our page was |
| 951 | * not yet write-protected, so may have changed since. |
| 952 | */ |
| 953 | return NULL; |
| 954 | } |
| 955 | } |
| 956 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 957 | rmap_item->address |= NODE_FLAG | STABLE_FLAG; |
| 958 | rmap_item->next = NULL; |
| 959 | rb_link_node(&rmap_item->node, parent, new); |
| 960 | rb_insert_color(&rmap_item->node, &root_stable_tree); |
| 961 | |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 962 | ksm_pages_shared++; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 963 | return rmap_item; |
| 964 | } |
| 965 | |
| 966 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 967 | * unstable_tree_search_insert - search for identical page, |
| 968 | * else insert rmap_item into the unstable tree. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 969 | * |
| 970 | * This function searches for a page in the unstable tree identical to the |
| 971 | * page currently being scanned; and if no identical page is found in the |
| 972 | * tree, we insert rmap_item as a new object into the unstable tree. |
| 973 | * |
| 974 | * This function returns pointer to rmap_item found to be identical |
| 975 | * to the currently scanned page, NULL otherwise. |
| 976 | * |
| 977 | * This function does both searching and inserting, because they share |
| 978 | * the same walking algorithm in an rbtree. |
| 979 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 980 | static |
| 981 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, |
| 982 | struct page *page, |
| 983 | struct page **tree_pagep) |
| 984 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 985 | { |
| 986 | struct rb_node **new = &root_unstable_tree.rb_node; |
| 987 | struct rb_node *parent = NULL; |
| 988 | |
| 989 | while (*new) { |
| 990 | struct rmap_item *tree_rmap_item; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 991 | struct page *tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 992 | int ret; |
| 993 | |
Hugh Dickins | d178f27 | 2009-11-09 15:58:23 +0000 | [diff] [blame] | 994 | cond_resched(); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 995 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 996 | tree_page = get_mergeable_page(tree_rmap_item); |
| 997 | if (!tree_page) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 998 | return NULL; |
| 999 | |
| 1000 | /* |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1001 | * Don't substitute a ksm page for a forked page. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1002 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1003 | if (page == tree_page) { |
| 1004 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1005 | return NULL; |
| 1006 | } |
| 1007 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1008 | ret = memcmp_pages(page, tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1009 | |
| 1010 | parent = *new; |
| 1011 | if (ret < 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1012 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1013 | new = &parent->rb_left; |
| 1014 | } else if (ret > 0) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1015 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1016 | new = &parent->rb_right; |
| 1017 | } else { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1018 | *tree_pagep = tree_page; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1019 | return tree_rmap_item; |
| 1020 | } |
| 1021 | } |
| 1022 | |
| 1023 | rmap_item->address |= NODE_FLAG; |
| 1024 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
| 1025 | rb_link_node(&rmap_item->node, parent, new); |
| 1026 | rb_insert_color(&rmap_item->node, &root_unstable_tree); |
| 1027 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 1028 | ksm_pages_unshared++; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1029 | return NULL; |
| 1030 | } |
| 1031 | |
| 1032 | /* |
| 1033 | * stable_tree_append - add another rmap_item to the linked list of |
| 1034 | * rmap_items hanging off a given node of the stable tree, all sharing |
| 1035 | * the same ksm page. |
| 1036 | */ |
| 1037 | static void stable_tree_append(struct rmap_item *rmap_item, |
| 1038 | struct rmap_item *tree_rmap_item) |
| 1039 | { |
| 1040 | rmap_item->next = tree_rmap_item->next; |
| 1041 | rmap_item->prev = tree_rmap_item; |
| 1042 | |
| 1043 | if (tree_rmap_item->next) |
| 1044 | tree_rmap_item->next->prev = rmap_item; |
| 1045 | |
| 1046 | tree_rmap_item->next = rmap_item; |
| 1047 | rmap_item->address |= STABLE_FLAG; |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 1048 | |
| 1049 | ksm_pages_sharing++; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1050 | } |
| 1051 | |
| 1052 | /* |
Hugh Dickins | 81464e30 | 2009-09-21 17:02:15 -0700 | [diff] [blame] | 1053 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
| 1054 | * if not, compare checksum to previous and if it's the same, see if page can |
| 1055 | * be inserted into the unstable tree, or merged with a page already there and |
| 1056 | * both transferred to the stable tree. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1057 | * |
| 1058 | * @page: the page that we are searching identical page to. |
| 1059 | * @rmap_item: the reverse mapping into the virtual address of this page |
| 1060 | */ |
| 1061 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) |
| 1062 | { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1063 | struct rmap_item *tree_rmap_item; |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1064 | struct page *tree_page = NULL; |
| 1065 | struct page *kpage; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1066 | unsigned int checksum; |
| 1067 | int err; |
| 1068 | |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 1069 | remove_rmap_item_from_tree(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1070 | |
| 1071 | /* We first start with searching the page inside the stable tree */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1072 | tree_rmap_item = stable_tree_search(page, &tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1073 | if (tree_rmap_item) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1074 | kpage = tree_page; |
| 1075 | if (page == kpage) /* forked */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1076 | err = 0; |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 1077 | else |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1078 | err = try_to_merge_with_ksm_page(rmap_item, |
| 1079 | page, kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1080 | if (!err) { |
| 1081 | /* |
| 1082 | * The page was successfully merged: |
| 1083 | * add its rmap_item to the stable tree. |
| 1084 | */ |
| 1085 | stable_tree_append(rmap_item, tree_rmap_item); |
| 1086 | } |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1087 | put_page(kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1088 | return; |
| 1089 | } |
| 1090 | |
| 1091 | /* |
| 1092 | * A ksm page might have got here by fork, but its other |
| 1093 | * references have already been removed from the stable tree. |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1094 | * Or it might be left over from a break_ksm which failed |
| 1095 | * when the mem_cgroup had reached its limit: try again now. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1096 | */ |
| 1097 | if (PageKsm(page)) |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1098 | break_cow(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1099 | |
| 1100 | /* |
| 1101 | * In case the hash value of the page was changed from the last time we |
| 1102 | * have calculated it, this page to be changed frequely, therefore we |
| 1103 | * don't want to insert it to the unstable tree, and we don't want to |
| 1104 | * waste our time to search if there is something identical to it there. |
| 1105 | */ |
| 1106 | checksum = calc_checksum(page); |
| 1107 | if (rmap_item->oldchecksum != checksum) { |
| 1108 | rmap_item->oldchecksum = checksum; |
| 1109 | return; |
| 1110 | } |
| 1111 | |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1112 | tree_rmap_item = |
| 1113 | unstable_tree_search_insert(rmap_item, page, &tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1114 | if (tree_rmap_item) { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1115 | kpage = try_to_merge_two_pages(rmap_item, page, |
| 1116 | tree_rmap_item, tree_page); |
| 1117 | put_page(tree_page); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1118 | /* |
| 1119 | * As soon as we merge this page, we want to remove the |
| 1120 | * rmap_item of the page we have merged with from the unstable |
| 1121 | * tree, and insert it instead as new node in the stable tree. |
| 1122 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1123 | if (kpage) { |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 1124 | remove_rmap_item_from_tree(tree_rmap_item); |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 1125 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1126 | /* |
| 1127 | * If we fail to insert the page into the stable tree, |
| 1128 | * we will have 2 virtual addresses that are pointing |
| 1129 | * to a ksm page left outside the stable tree, |
| 1130 | * in which case we need to break_cow on both. |
| 1131 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1132 | if (stable_tree_insert(kpage, tree_rmap_item)) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1133 | stable_tree_append(rmap_item, tree_rmap_item); |
| 1134 | else { |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1135 | break_cow(tree_rmap_item); |
| 1136 | break_cow(rmap_item); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1137 | } |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1138 | put_page(kpage); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1139 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1140 | } |
| 1141 | } |
| 1142 | |
| 1143 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, |
| 1144 | struct list_head *cur, |
| 1145 | unsigned long addr) |
| 1146 | { |
| 1147 | struct rmap_item *rmap_item; |
| 1148 | |
| 1149 | while (cur != &mm_slot->rmap_list) { |
| 1150 | rmap_item = list_entry(cur, struct rmap_item, link); |
Hugh Dickins | 93d1771 | 2009-12-14 17:59:16 -0800 | [diff] [blame] | 1151 | if ((rmap_item->address & PAGE_MASK) == addr) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1152 | return rmap_item; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1153 | if (rmap_item->address > addr) |
| 1154 | break; |
| 1155 | cur = cur->next; |
| 1156 | remove_rmap_item_from_tree(rmap_item); |
| 1157 | list_del(&rmap_item->link); |
| 1158 | free_rmap_item(rmap_item); |
| 1159 | } |
| 1160 | |
| 1161 | rmap_item = alloc_rmap_item(); |
| 1162 | if (rmap_item) { |
| 1163 | /* It has already been zeroed */ |
| 1164 | rmap_item->mm = mm_slot->mm; |
| 1165 | rmap_item->address = addr; |
| 1166 | list_add_tail(&rmap_item->link, cur); |
| 1167 | } |
| 1168 | return rmap_item; |
| 1169 | } |
| 1170 | |
| 1171 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) |
| 1172 | { |
| 1173 | struct mm_struct *mm; |
| 1174 | struct mm_slot *slot; |
| 1175 | struct vm_area_struct *vma; |
| 1176 | struct rmap_item *rmap_item; |
| 1177 | |
| 1178 | if (list_empty(&ksm_mm_head.mm_list)) |
| 1179 | return NULL; |
| 1180 | |
| 1181 | slot = ksm_scan.mm_slot; |
| 1182 | if (slot == &ksm_mm_head) { |
| 1183 | root_unstable_tree = RB_ROOT; |
| 1184 | |
| 1185 | spin_lock(&ksm_mmlist_lock); |
| 1186 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); |
| 1187 | ksm_scan.mm_slot = slot; |
| 1188 | spin_unlock(&ksm_mmlist_lock); |
| 1189 | next_mm: |
| 1190 | ksm_scan.address = 0; |
| 1191 | ksm_scan.rmap_item = list_entry(&slot->rmap_list, |
| 1192 | struct rmap_item, link); |
| 1193 | } |
| 1194 | |
| 1195 | mm = slot->mm; |
| 1196 | down_read(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1197 | if (ksm_test_exit(mm)) |
| 1198 | vma = NULL; |
| 1199 | else |
| 1200 | vma = find_vma(mm, ksm_scan.address); |
| 1201 | |
| 1202 | for (; vma; vma = vma->vm_next) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1203 | if (!(vma->vm_flags & VM_MERGEABLE)) |
| 1204 | continue; |
| 1205 | if (ksm_scan.address < vma->vm_start) |
| 1206 | ksm_scan.address = vma->vm_start; |
| 1207 | if (!vma->anon_vma) |
| 1208 | ksm_scan.address = vma->vm_end; |
| 1209 | |
| 1210 | while (ksm_scan.address < vma->vm_end) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1211 | if (ksm_test_exit(mm)) |
| 1212 | break; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1213 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
| 1214 | if (*page && PageAnon(*page)) { |
| 1215 | flush_anon_page(vma, *page, ksm_scan.address); |
| 1216 | flush_dcache_page(*page); |
| 1217 | rmap_item = get_next_rmap_item(slot, |
| 1218 | ksm_scan.rmap_item->link.next, |
| 1219 | ksm_scan.address); |
| 1220 | if (rmap_item) { |
| 1221 | ksm_scan.rmap_item = rmap_item; |
| 1222 | ksm_scan.address += PAGE_SIZE; |
| 1223 | } else |
| 1224 | put_page(*page); |
| 1225 | up_read(&mm->mmap_sem); |
| 1226 | return rmap_item; |
| 1227 | } |
| 1228 | if (*page) |
| 1229 | put_page(*page); |
| 1230 | ksm_scan.address += PAGE_SIZE; |
| 1231 | cond_resched(); |
| 1232 | } |
| 1233 | } |
| 1234 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1235 | if (ksm_test_exit(mm)) { |
| 1236 | ksm_scan.address = 0; |
| 1237 | ksm_scan.rmap_item = list_entry(&slot->rmap_list, |
| 1238 | struct rmap_item, link); |
| 1239 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1240 | /* |
| 1241 | * Nuke all the rmap_items that are above this current rmap: |
| 1242 | * because there were no VM_MERGEABLE vmas with such addresses. |
| 1243 | */ |
| 1244 | remove_trailing_rmap_items(slot, ksm_scan.rmap_item->link.next); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1245 | |
| 1246 | spin_lock(&ksm_mmlist_lock); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1247 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
| 1248 | struct mm_slot, mm_list); |
| 1249 | if (ksm_scan.address == 0) { |
| 1250 | /* |
| 1251 | * We've completed a full scan of all vmas, holding mmap_sem |
| 1252 | * throughout, and found no VM_MERGEABLE: so do the same as |
| 1253 | * __ksm_exit does to remove this mm from all our lists now. |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1254 | * This applies either when cleaning up after __ksm_exit |
| 1255 | * (but beware: we can reach here even before __ksm_exit), |
| 1256 | * or when all VM_MERGEABLE areas have been unmapped (and |
| 1257 | * mmap_sem then protects against race with MADV_MERGEABLE). |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1258 | */ |
| 1259 | hlist_del(&slot->link); |
| 1260 | list_del(&slot->mm_list); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1261 | spin_unlock(&ksm_mmlist_lock); |
| 1262 | |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1263 | free_mm_slot(slot); |
| 1264 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1265 | up_read(&mm->mmap_sem); |
| 1266 | mmdrop(mm); |
| 1267 | } else { |
| 1268 | spin_unlock(&ksm_mmlist_lock); |
| 1269 | up_read(&mm->mmap_sem); |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1270 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1271 | |
| 1272 | /* Repeat until we've completed scanning the whole list */ |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1273 | slot = ksm_scan.mm_slot; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1274 | if (slot != &ksm_mm_head) |
| 1275 | goto next_mm; |
| 1276 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1277 | ksm_scan.seqnr++; |
| 1278 | return NULL; |
| 1279 | } |
| 1280 | |
| 1281 | /** |
| 1282 | * ksm_do_scan - the ksm scanner main worker function. |
| 1283 | * @scan_npages - number of pages we want to scan before we return. |
| 1284 | */ |
| 1285 | static void ksm_do_scan(unsigned int scan_npages) |
| 1286 | { |
| 1287 | struct rmap_item *rmap_item; |
| 1288 | struct page *page; |
| 1289 | |
| 1290 | while (scan_npages--) { |
| 1291 | cond_resched(); |
| 1292 | rmap_item = scan_get_next_rmap_item(&page); |
| 1293 | if (!rmap_item) |
| 1294 | return; |
| 1295 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) |
| 1296 | cmp_and_merge_page(page, rmap_item); |
Hugh Dickins | 26465d3 | 2009-09-21 17:02:12 -0700 | [diff] [blame] | 1297 | else if (page_mapcount(page) == 1) { |
| 1298 | /* |
| 1299 | * Replace now-unshared ksm page by ordinary page. |
| 1300 | */ |
Hugh Dickins | 8dd3557 | 2009-12-14 17:59:18 -0800 | [diff] [blame^] | 1301 | break_cow(rmap_item); |
Hugh Dickins | 26465d3 | 2009-09-21 17:02:12 -0700 | [diff] [blame] | 1302 | remove_rmap_item_from_tree(rmap_item); |
| 1303 | rmap_item->oldchecksum = calc_checksum(page); |
| 1304 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1305 | put_page(page); |
| 1306 | } |
| 1307 | } |
| 1308 | |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1309 | static int ksmd_should_run(void) |
| 1310 | { |
| 1311 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); |
| 1312 | } |
| 1313 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1314 | static int ksm_scan_thread(void *nothing) |
| 1315 | { |
Izik Eidus | 339aa62 | 2009-09-21 17:02:07 -0700 | [diff] [blame] | 1316 | set_user_nice(current, 5); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1317 | |
| 1318 | while (!kthread_should_stop()) { |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1319 | mutex_lock(&ksm_thread_mutex); |
| 1320 | if (ksmd_should_run()) |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1321 | ksm_do_scan(ksm_thread_pages_to_scan); |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1322 | mutex_unlock(&ksm_thread_mutex); |
| 1323 | |
| 1324 | if (ksmd_should_run()) { |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1325 | schedule_timeout_interruptible( |
| 1326 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); |
| 1327 | } else { |
| 1328 | wait_event_interruptible(ksm_thread_wait, |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1329 | ksmd_should_run() || kthread_should_stop()); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1330 | } |
| 1331 | } |
| 1332 | return 0; |
| 1333 | } |
| 1334 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1335 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
| 1336 | unsigned long end, int advice, unsigned long *vm_flags) |
| 1337 | { |
| 1338 | struct mm_struct *mm = vma->vm_mm; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1339 | int err; |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1340 | |
| 1341 | switch (advice) { |
| 1342 | case MADV_MERGEABLE: |
| 1343 | /* |
| 1344 | * Be somewhat over-protective for now! |
| 1345 | */ |
| 1346 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | |
| 1347 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | |
| 1348 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | |
| 1349 | VM_MIXEDMAP | VM_SAO)) |
| 1350 | return 0; /* just ignore the advice */ |
| 1351 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1352 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
| 1353 | err = __ksm_enter(mm); |
| 1354 | if (err) |
| 1355 | return err; |
| 1356 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1357 | |
| 1358 | *vm_flags |= VM_MERGEABLE; |
| 1359 | break; |
| 1360 | |
| 1361 | case MADV_UNMERGEABLE: |
| 1362 | if (!(*vm_flags & VM_MERGEABLE)) |
| 1363 | return 0; /* just ignore the advice */ |
| 1364 | |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1365 | if (vma->anon_vma) { |
| 1366 | err = unmerge_ksm_pages(vma, start, end); |
| 1367 | if (err) |
| 1368 | return err; |
| 1369 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1370 | |
| 1371 | *vm_flags &= ~VM_MERGEABLE; |
| 1372 | break; |
| 1373 | } |
| 1374 | |
| 1375 | return 0; |
| 1376 | } |
| 1377 | |
| 1378 | int __ksm_enter(struct mm_struct *mm) |
| 1379 | { |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1380 | struct mm_slot *mm_slot; |
| 1381 | int needs_wakeup; |
| 1382 | |
| 1383 | mm_slot = alloc_mm_slot(); |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1384 | if (!mm_slot) |
| 1385 | return -ENOMEM; |
| 1386 | |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1387 | /* Check ksm_run too? Would need tighter locking */ |
| 1388 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); |
| 1389 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1390 | spin_lock(&ksm_mmlist_lock); |
| 1391 | insert_to_mm_slots_hash(mm, mm_slot); |
| 1392 | /* |
| 1393 | * Insert just behind the scanning cursor, to let the area settle |
| 1394 | * down a little; when fork is followed by immediate exec, we don't |
| 1395 | * want ksmd to waste time setting up and tearing down an rmap_list. |
| 1396 | */ |
| 1397 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); |
| 1398 | spin_unlock(&ksm_mmlist_lock); |
| 1399 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1400 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1401 | atomic_inc(&mm->mm_count); |
Hugh Dickins | 6e158384 | 2009-09-21 17:02:14 -0700 | [diff] [blame] | 1402 | |
| 1403 | if (needs_wakeup) |
| 1404 | wake_up_interruptible(&ksm_thread_wait); |
| 1405 | |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1406 | return 0; |
| 1407 | } |
| 1408 | |
Andrea Arcangeli | 1c2fb7a | 2009-09-21 17:02:22 -0700 | [diff] [blame] | 1409 | void __ksm_exit(struct mm_struct *mm) |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1410 | { |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1411 | struct mm_slot *mm_slot; |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1412 | int easy_to_free = 0; |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1413 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1414 | /* |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1415 | * This process is exiting: if it's straightforward (as is the |
| 1416 | * case when ksmd was never running), free mm_slot immediately. |
| 1417 | * But if it's at the cursor or has rmap_items linked to it, use |
| 1418 | * mmap_sem to synchronize with any break_cows before pagetables |
| 1419 | * are freed, and leave the mm_slot on the list for ksmd to free. |
| 1420 | * Beware: ksm may already have noticed it exiting and freed the slot. |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1421 | */ |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1422 | |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1423 | spin_lock(&ksm_mmlist_lock); |
| 1424 | mm_slot = get_mm_slot(mm); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1425 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
| 1426 | if (list_empty(&mm_slot->rmap_list)) { |
| 1427 | hlist_del(&mm_slot->link); |
| 1428 | list_del(&mm_slot->mm_list); |
| 1429 | easy_to_free = 1; |
| 1430 | } else { |
| 1431 | list_move(&mm_slot->mm_list, |
| 1432 | &ksm_scan.mm_slot->mm_list); |
| 1433 | } |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1434 | } |
Hugh Dickins | cd551f9 | 2009-09-21 17:02:17 -0700 | [diff] [blame] | 1435 | spin_unlock(&ksm_mmlist_lock); |
| 1436 | |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1437 | if (easy_to_free) { |
| 1438 | free_mm_slot(mm_slot); |
| 1439 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
| 1440 | mmdrop(mm); |
| 1441 | } else if (mm_slot) { |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1442 | down_write(&mm->mmap_sem); |
| 1443 | up_write(&mm->mmap_sem); |
Hugh Dickins | 9ba6929 | 2009-09-21 17:02:20 -0700 | [diff] [blame] | 1444 | } |
Hugh Dickins | f8af4da | 2009-09-21 17:01:57 -0700 | [diff] [blame] | 1445 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1446 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1447 | #ifdef CONFIG_SYSFS |
| 1448 | /* |
| 1449 | * This all compiles without CONFIG_SYSFS, but is a waste of space. |
| 1450 | */ |
| 1451 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1452 | #define KSM_ATTR_RO(_name) \ |
| 1453 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) |
| 1454 | #define KSM_ATTR(_name) \ |
| 1455 | static struct kobj_attribute _name##_attr = \ |
| 1456 | __ATTR(_name, 0644, _name##_show, _name##_store) |
| 1457 | |
| 1458 | static ssize_t sleep_millisecs_show(struct kobject *kobj, |
| 1459 | struct kobj_attribute *attr, char *buf) |
| 1460 | { |
| 1461 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); |
| 1462 | } |
| 1463 | |
| 1464 | static ssize_t sleep_millisecs_store(struct kobject *kobj, |
| 1465 | struct kobj_attribute *attr, |
| 1466 | const char *buf, size_t count) |
| 1467 | { |
| 1468 | unsigned long msecs; |
| 1469 | int err; |
| 1470 | |
| 1471 | err = strict_strtoul(buf, 10, &msecs); |
| 1472 | if (err || msecs > UINT_MAX) |
| 1473 | return -EINVAL; |
| 1474 | |
| 1475 | ksm_thread_sleep_millisecs = msecs; |
| 1476 | |
| 1477 | return count; |
| 1478 | } |
| 1479 | KSM_ATTR(sleep_millisecs); |
| 1480 | |
| 1481 | static ssize_t pages_to_scan_show(struct kobject *kobj, |
| 1482 | struct kobj_attribute *attr, char *buf) |
| 1483 | { |
| 1484 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); |
| 1485 | } |
| 1486 | |
| 1487 | static ssize_t pages_to_scan_store(struct kobject *kobj, |
| 1488 | struct kobj_attribute *attr, |
| 1489 | const char *buf, size_t count) |
| 1490 | { |
| 1491 | int err; |
| 1492 | unsigned long nr_pages; |
| 1493 | |
| 1494 | err = strict_strtoul(buf, 10, &nr_pages); |
| 1495 | if (err || nr_pages > UINT_MAX) |
| 1496 | return -EINVAL; |
| 1497 | |
| 1498 | ksm_thread_pages_to_scan = nr_pages; |
| 1499 | |
| 1500 | return count; |
| 1501 | } |
| 1502 | KSM_ATTR(pages_to_scan); |
| 1503 | |
| 1504 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, |
| 1505 | char *buf) |
| 1506 | { |
| 1507 | return sprintf(buf, "%u\n", ksm_run); |
| 1508 | } |
| 1509 | |
| 1510 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, |
| 1511 | const char *buf, size_t count) |
| 1512 | { |
| 1513 | int err; |
| 1514 | unsigned long flags; |
| 1515 | |
| 1516 | err = strict_strtoul(buf, 10, &flags); |
| 1517 | if (err || flags > UINT_MAX) |
| 1518 | return -EINVAL; |
| 1519 | if (flags > KSM_RUN_UNMERGE) |
| 1520 | return -EINVAL; |
| 1521 | |
| 1522 | /* |
| 1523 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. |
| 1524 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 1525 | * breaking COW to free the unswappable pages_shared (but leaves |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1526 | * mm_slots on the list for when ksmd may be set running again). |
| 1527 | */ |
| 1528 | |
| 1529 | mutex_lock(&ksm_thread_mutex); |
| 1530 | if (ksm_run != flags) { |
| 1531 | ksm_run = flags; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1532 | if (flags & KSM_RUN_UNMERGE) { |
Hugh Dickins | 35451be | 2009-09-21 17:02:27 -0700 | [diff] [blame] | 1533 | current->flags |= PF_OOM_ORIGIN; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1534 | err = unmerge_and_remove_all_rmap_items(); |
Hugh Dickins | 35451be | 2009-09-21 17:02:27 -0700 | [diff] [blame] | 1535 | current->flags &= ~PF_OOM_ORIGIN; |
Hugh Dickins | d952b79 | 2009-09-21 17:02:16 -0700 | [diff] [blame] | 1536 | if (err) { |
| 1537 | ksm_run = KSM_RUN_STOP; |
| 1538 | count = err; |
| 1539 | } |
| 1540 | } |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1541 | } |
| 1542 | mutex_unlock(&ksm_thread_mutex); |
| 1543 | |
| 1544 | if (flags & KSM_RUN_MERGE) |
| 1545 | wake_up_interruptible(&ksm_thread_wait); |
| 1546 | |
| 1547 | return count; |
| 1548 | } |
| 1549 | KSM_ATTR(run); |
| 1550 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1551 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
| 1552 | struct kobj_attribute *attr, |
| 1553 | const char *buf, size_t count) |
| 1554 | { |
| 1555 | int err; |
| 1556 | unsigned long nr_pages; |
| 1557 | |
| 1558 | err = strict_strtoul(buf, 10, &nr_pages); |
| 1559 | if (err) |
| 1560 | return -EINVAL; |
| 1561 | |
| 1562 | ksm_max_kernel_pages = nr_pages; |
| 1563 | |
| 1564 | return count; |
| 1565 | } |
| 1566 | |
| 1567 | static ssize_t max_kernel_pages_show(struct kobject *kobj, |
| 1568 | struct kobj_attribute *attr, char *buf) |
| 1569 | { |
| 1570 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); |
| 1571 | } |
| 1572 | KSM_ATTR(max_kernel_pages); |
| 1573 | |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 1574 | static ssize_t pages_shared_show(struct kobject *kobj, |
| 1575 | struct kobj_attribute *attr, char *buf) |
| 1576 | { |
| 1577 | return sprintf(buf, "%lu\n", ksm_pages_shared); |
| 1578 | } |
| 1579 | KSM_ATTR_RO(pages_shared); |
| 1580 | |
| 1581 | static ssize_t pages_sharing_show(struct kobject *kobj, |
| 1582 | struct kobj_attribute *attr, char *buf) |
| 1583 | { |
Hugh Dickins | e178dfd | 2009-09-21 17:02:10 -0700 | [diff] [blame] | 1584 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 1585 | } |
| 1586 | KSM_ATTR_RO(pages_sharing); |
| 1587 | |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 1588 | static ssize_t pages_unshared_show(struct kobject *kobj, |
| 1589 | struct kobj_attribute *attr, char *buf) |
| 1590 | { |
| 1591 | return sprintf(buf, "%lu\n", ksm_pages_unshared); |
| 1592 | } |
| 1593 | KSM_ATTR_RO(pages_unshared); |
| 1594 | |
| 1595 | static ssize_t pages_volatile_show(struct kobject *kobj, |
| 1596 | struct kobj_attribute *attr, char *buf) |
| 1597 | { |
| 1598 | long ksm_pages_volatile; |
| 1599 | |
| 1600 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared |
| 1601 | - ksm_pages_sharing - ksm_pages_unshared; |
| 1602 | /* |
| 1603 | * It was not worth any locking to calculate that statistic, |
| 1604 | * but it might therefore sometimes be negative: conceal that. |
| 1605 | */ |
| 1606 | if (ksm_pages_volatile < 0) |
| 1607 | ksm_pages_volatile = 0; |
| 1608 | return sprintf(buf, "%ld\n", ksm_pages_volatile); |
| 1609 | } |
| 1610 | KSM_ATTR_RO(pages_volatile); |
| 1611 | |
| 1612 | static ssize_t full_scans_show(struct kobject *kobj, |
| 1613 | struct kobj_attribute *attr, char *buf) |
| 1614 | { |
| 1615 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); |
| 1616 | } |
| 1617 | KSM_ATTR_RO(full_scans); |
| 1618 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1619 | static struct attribute *ksm_attrs[] = { |
| 1620 | &sleep_millisecs_attr.attr, |
| 1621 | &pages_to_scan_attr.attr, |
| 1622 | &run_attr.attr, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1623 | &max_kernel_pages_attr.attr, |
Hugh Dickins | b402826 | 2009-09-21 17:02:09 -0700 | [diff] [blame] | 1624 | &pages_shared_attr.attr, |
| 1625 | &pages_sharing_attr.attr, |
Hugh Dickins | 473b0ce | 2009-09-21 17:02:11 -0700 | [diff] [blame] | 1626 | &pages_unshared_attr.attr, |
| 1627 | &pages_volatile_attr.attr, |
| 1628 | &full_scans_attr.attr, |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1629 | NULL, |
| 1630 | }; |
| 1631 | |
| 1632 | static struct attribute_group ksm_attr_group = { |
| 1633 | .attrs = ksm_attrs, |
| 1634 | .name = "ksm", |
| 1635 | }; |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1636 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1637 | |
| 1638 | static int __init ksm_init(void) |
| 1639 | { |
| 1640 | struct task_struct *ksm_thread; |
| 1641 | int err; |
| 1642 | |
Hugh Dickins | c73602a | 2009-10-07 16:32:22 -0700 | [diff] [blame] | 1643 | ksm_max_kernel_pages = totalram_pages / 4; |
Izik Eidus | 2c6854f | 2009-09-23 15:56:04 -0700 | [diff] [blame] | 1644 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1645 | err = ksm_slab_init(); |
| 1646 | if (err) |
| 1647 | goto out; |
| 1648 | |
| 1649 | err = mm_slots_hash_init(); |
| 1650 | if (err) |
| 1651 | goto out_free1; |
| 1652 | |
| 1653 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
| 1654 | if (IS_ERR(ksm_thread)) { |
| 1655 | printk(KERN_ERR "ksm: creating kthread failed\n"); |
| 1656 | err = PTR_ERR(ksm_thread); |
| 1657 | goto out_free2; |
| 1658 | } |
| 1659 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1660 | #ifdef CONFIG_SYSFS |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1661 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
| 1662 | if (err) { |
| 1663 | printk(KERN_ERR "ksm: register sysfs failed\n"); |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1664 | kthread_stop(ksm_thread); |
| 1665 | goto out_free2; |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1666 | } |
Hugh Dickins | c73602a | 2009-10-07 16:32:22 -0700 | [diff] [blame] | 1667 | #else |
| 1668 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ |
| 1669 | |
Hugh Dickins | 2ffd867 | 2009-09-21 17:02:23 -0700 | [diff] [blame] | 1670 | #endif /* CONFIG_SYSFS */ |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1671 | |
| 1672 | return 0; |
| 1673 | |
Izik Eidus | 31dbd01 | 2009-09-21 17:02:03 -0700 | [diff] [blame] | 1674 | out_free2: |
| 1675 | mm_slots_hash_free(); |
| 1676 | out_free1: |
| 1677 | ksm_slab_free(); |
| 1678 | out: |
| 1679 | return err; |
| 1680 | } |
| 1681 | module_init(ksm_init) |