blob: 133ea2ca8384e69a97099096cb479d84d43ba2c7 [file] [log] [blame]
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001/*
Izik Eidus31dbd012009-09-21 17:02:03 -07002 * 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 Eidus36b25282009-09-21 17:02:06 -07007 * Copyright (C) 2008-2009 Red Hat, Inc.
Izik Eidus31dbd012009-09-21 17:02:03 -07008 * Authors:
9 * Izik Eidus
10 * Andrea Arcangeli
11 * Chris Wright
Izik Eidus36b25282009-09-21 17:02:06 -070012 * Hugh Dickins
Izik Eidus31dbd012009-09-21 17:02:03 -070013 *
14 * This work is licensed under the terms of the GNU GPL, version 2.
Hugh Dickinsf8af4da2009-09-21 17:01:57 -070015 */
16
17#include <linux/errno.h>
Izik Eidus31dbd012009-09-21 17:02:03 -070018#include <linux/mm.h>
19#include <linux/fs.h>
Hugh Dickinsf8af4da2009-09-21 17:01:57 -070020#include <linux/mman.h>
Izik Eidus31dbd012009-09-21 17:02:03 -070021#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 Eidus2c6854f2009-09-23 15:56:04 -070033#include <linux/swap.h>
Hugh Dickinsf8af4da2009-09-21 17:01:57 -070034#include <linux/ksm.h>
35
Izik Eidus31dbd012009-09-21 17:02:03 -070036#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 */
85struct 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 */
101struct 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 */
118struct 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 */
137static struct rb_root root_stable_tree = RB_ROOT;
138static struct rb_root root_unstable_tree = RB_ROOT;
139
140#define MM_SLOTS_HASH_HEADS 1024
141static struct hlist_head *mm_slots_hash;
142
143static struct mm_slot ksm_mm_head = {
144 .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list),
145};
146static struct ksm_scan ksm_scan = {
147 .mm_slot = &ksm_mm_head,
148};
149
150static struct kmem_cache *rmap_item_cache;
151static struct kmem_cache *mm_slot_cache;
152
153/* The number of nodes in the stable tree */
Hugh Dickinsb4028262009-09-21 17:02:09 -0700154static unsigned long ksm_pages_shared;
Izik Eidus31dbd012009-09-21 17:02:03 -0700155
Hugh Dickinse178dfd2009-09-21 17:02:10 -0700156/* The number of page slots additionally sharing those nodes */
Hugh Dickinsb4028262009-09-21 17:02:09 -0700157static unsigned long ksm_pages_sharing;
Izik Eidus31dbd012009-09-21 17:02:03 -0700158
Hugh Dickins473b0ce2009-09-21 17:02:11 -0700159/* The number of nodes in the unstable tree */
160static unsigned long ksm_pages_unshared;
161
162/* The number of rmap_items in use: to calculate pages_volatile */
163static unsigned long ksm_rmap_items;
164
Izik Eidus31dbd012009-09-21 17:02:03 -0700165/* Limit on the number of unswappable pages used */
Izik Eidus2c6854f2009-09-23 15:56:04 -0700166static unsigned long ksm_max_kernel_pages;
Izik Eidus31dbd012009-09-21 17:02:03 -0700167
168/* Number of pages ksmd should scan in one batch */
Izik Eidus2c6854f2009-09-23 15:56:04 -0700169static unsigned int ksm_thread_pages_to_scan = 100;
Izik Eidus31dbd012009-09-21 17:02:03 -0700170
171/* Milliseconds ksmd should sleep between batches */
Hugh Dickins2ffd8672009-09-21 17:02:23 -0700172static unsigned int ksm_thread_sleep_millisecs = 20;
Izik Eidus31dbd012009-09-21 17:02:03 -0700173
174#define KSM_RUN_STOP 0
175#define KSM_RUN_MERGE 1
176#define KSM_RUN_UNMERGE 2
Izik Eidus2c6854f2009-09-23 15:56:04 -0700177static unsigned int ksm_run = KSM_RUN_STOP;
Izik Eidus31dbd012009-09-21 17:02:03 -0700178
179static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait);
180static DEFINE_MUTEX(ksm_thread_mutex);
181static 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
187static 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
199out_free:
200 kmem_cache_destroy(rmap_item_cache);
201out:
202 return -ENOMEM;
203}
204
205static 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
212static inline struct rmap_item *alloc_rmap_item(void)
213{
Hugh Dickins473b0ce2009-09-21 17:02:11 -0700214 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 Eidus31dbd012009-09-21 17:02:03 -0700220}
221
222static inline void free_rmap_item(struct rmap_item *rmap_item)
223{
Hugh Dickins473b0ce2009-09-21 17:02:11 -0700224 ksm_rmap_items--;
Izik Eidus31dbd012009-09-21 17:02:03 -0700225 rmap_item->mm = NULL; /* debug safety */
226 kmem_cache_free(rmap_item_cache, rmap_item);
227}
228
229static 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
236static inline void free_mm_slot(struct mm_slot *mm_slot)
237{
238 kmem_cache_free(mm_slot_cache, mm_slot);
239}
240
241static 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
250static void __init mm_slots_hash_free(void)
251{
252 kfree(mm_slots_hash);
253}
254
255static 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
270static 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
282static inline int in_stable_tree(struct rmap_item *rmap_item)
283{
284 return rmap_item->address & STABLE_FLAG;
285}
286
287/*
Hugh Dickinsa913e182009-09-21 17:02:26 -0700288 * 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 */
295static inline bool ksm_test_exit(struct mm_struct *mm)
296{
297 return atomic_read(&mm->mm_users) == 0;
298}
299
300/*
Izik Eidus31dbd012009-09-21 17:02:03 -0700301 * 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 Dickinsd952b792009-09-21 17:02:16 -0700311static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
Izik Eidus31dbd012009-09-21 17:02:03 -0700312{
313 struct page *page;
Hugh Dickinsd952b792009-09-21 17:02:16 -0700314 int ret = 0;
Izik Eidus31dbd012009-09-21 17:02:03 -0700315
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 Dickinsd952b792009-09-21 17:02:16 -0700327 } 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 Eidus31dbd012009-09-21 17:02:03 -0700357}
358
Hugh Dickins81464e302009-09-21 17:02:15 -0700359static void break_cow(struct mm_struct *mm, unsigned long addr)
Izik Eidus31dbd012009-09-21 17:02:03 -0700360{
361 struct vm_area_struct *vma;
362
Hugh Dickins81464e302009-09-21 17:02:15 -0700363 down_read(&mm->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700364 if (ksm_test_exit(mm))
365 goto out;
Izik Eidus31dbd012009-09-21 17:02:03 -0700366 vma = find_vma(mm, addr);
367 if (!vma || vma->vm_start > addr)
Hugh Dickins81464e302009-09-21 17:02:15 -0700368 goto out;
Izik Eidus31dbd012009-09-21 17:02:03 -0700369 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
Hugh Dickins81464e302009-09-21 17:02:15 -0700370 goto out;
Izik Eidus31dbd012009-09-21 17:02:03 -0700371 break_ksm(vma, addr);
Hugh Dickins81464e302009-09-21 17:02:15 -0700372out:
Izik Eidus31dbd012009-09-21 17:02:03 -0700373 up_read(&mm->mmap_sem);
374}
375
376static struct page *get_mergeable_page(struct rmap_item *rmap_item)
377{
378 struct mm_struct *mm = rmap_item->mm;
379 unsigned long addr = rmap_item->address;
380 struct vm_area_struct *vma;
381 struct page *page;
382
383 down_read(&mm->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700384 if (ksm_test_exit(mm))
385 goto out;
Izik Eidus31dbd012009-09-21 17:02:03 -0700386 vma = find_vma(mm, addr);
387 if (!vma || vma->vm_start > addr)
388 goto out;
389 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
390 goto out;
391
392 page = follow_page(vma, addr, FOLL_GET);
393 if (!page)
394 goto out;
395 if (PageAnon(page)) {
396 flush_anon_page(vma, page, addr);
397 flush_dcache_page(page);
398 } else {
399 put_page(page);
400out: page = NULL;
401 }
402 up_read(&mm->mmap_sem);
403 return page;
404}
405
406/*
407 * get_ksm_page: checks if the page at the virtual address in rmap_item
408 * is still PageKsm, in which case we can trust the content of the page,
409 * and it returns the gotten page; but NULL if the page has been zapped.
410 */
411static struct page *get_ksm_page(struct rmap_item *rmap_item)
412{
413 struct page *page;
414
415 page = get_mergeable_page(rmap_item);
416 if (page && !PageKsm(page)) {
417 put_page(page);
418 page = NULL;
419 }
420 return page;
421}
422
423/*
424 * Removing rmap_item from stable or unstable tree.
425 * This function will clean the information from the stable/unstable tree.
426 */
427static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
428{
429 if (in_stable_tree(rmap_item)) {
430 struct rmap_item *next_item = rmap_item->next;
431
432 if (rmap_item->address & NODE_FLAG) {
433 if (next_item) {
434 rb_replace_node(&rmap_item->node,
435 &next_item->node,
436 &root_stable_tree);
437 next_item->address |= NODE_FLAG;
Hugh Dickinse178dfd2009-09-21 17:02:10 -0700438 ksm_pages_sharing--;
Izik Eidus31dbd012009-09-21 17:02:03 -0700439 } else {
440 rb_erase(&rmap_item->node, &root_stable_tree);
Hugh Dickinsb4028262009-09-21 17:02:09 -0700441 ksm_pages_shared--;
Izik Eidus31dbd012009-09-21 17:02:03 -0700442 }
443 } else {
444 struct rmap_item *prev_item = rmap_item->prev;
445
446 BUG_ON(prev_item->next != rmap_item);
447 prev_item->next = next_item;
448 if (next_item) {
449 BUG_ON(next_item->prev != rmap_item);
450 next_item->prev = rmap_item->prev;
451 }
Hugh Dickinse178dfd2009-09-21 17:02:10 -0700452 ksm_pages_sharing--;
Izik Eidus31dbd012009-09-21 17:02:03 -0700453 }
454
455 rmap_item->next = NULL;
Hugh Dickins93d17712009-12-14 17:59:16 -0800456 rmap_item->address &= PAGE_MASK;
Izik Eidus31dbd012009-09-21 17:02:03 -0700457
458 } else if (rmap_item->address & NODE_FLAG) {
459 unsigned char age;
460 /*
Hugh Dickins9ba69292009-09-21 17:02:20 -0700461 * Usually ksmd can and must skip the rb_erase, because
Izik Eidus31dbd012009-09-21 17:02:03 -0700462 * root_unstable_tree was already reset to RB_ROOT.
Hugh Dickins9ba69292009-09-21 17:02:20 -0700463 * But be careful when an mm is exiting: do the rb_erase
464 * if this rmap_item was inserted by this scan, rather
465 * than left over from before.
Izik Eidus31dbd012009-09-21 17:02:03 -0700466 */
467 age = (unsigned char)(ksm_scan.seqnr - rmap_item->address);
Hugh Dickinscd551f92009-09-21 17:02:17 -0700468 BUG_ON(age > 1);
Izik Eidus31dbd012009-09-21 17:02:03 -0700469 if (!age)
470 rb_erase(&rmap_item->node, &root_unstable_tree);
Izik Eidus31dbd012009-09-21 17:02:03 -0700471
Hugh Dickins93d17712009-12-14 17:59:16 -0800472 ksm_pages_unshared--;
473 rmap_item->address &= PAGE_MASK;
474 }
Izik Eidus31dbd012009-09-21 17:02:03 -0700475
476 cond_resched(); /* we're called from many long loops */
477}
478
Izik Eidus31dbd012009-09-21 17:02:03 -0700479static void remove_trailing_rmap_items(struct mm_slot *mm_slot,
480 struct list_head *cur)
481{
482 struct rmap_item *rmap_item;
483
484 while (cur != &mm_slot->rmap_list) {
485 rmap_item = list_entry(cur, struct rmap_item, link);
486 cur = cur->next;
487 remove_rmap_item_from_tree(rmap_item);
488 list_del(&rmap_item->link);
489 free_rmap_item(rmap_item);
490 }
491}
492
493/*
494 * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather
495 * than check every pte of a given vma, the locking doesn't quite work for
496 * that - an rmap_item is assigned to the stable tree after inserting ksm
497 * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing
498 * rmap_items from parent to child at fork time (so as not to waste time
499 * if exit comes before the next scan reaches it).
Hugh Dickins81464e302009-09-21 17:02:15 -0700500 *
501 * Similarly, although we'd like to remove rmap_items (so updating counts
502 * and freeing memory) when unmerging an area, it's easier to leave that
503 * to the next pass of ksmd - consider, for example, how ksmd might be
504 * in cmp_and_merge_page on one of the rmap_items we would be removing.
Izik Eidus31dbd012009-09-21 17:02:03 -0700505 */
Hugh Dickinsd952b792009-09-21 17:02:16 -0700506static int unmerge_ksm_pages(struct vm_area_struct *vma,
507 unsigned long start, unsigned long end)
Izik Eidus31dbd012009-09-21 17:02:03 -0700508{
509 unsigned long addr;
Hugh Dickinsd952b792009-09-21 17:02:16 -0700510 int err = 0;
Izik Eidus31dbd012009-09-21 17:02:03 -0700511
Hugh Dickinsd952b792009-09-21 17:02:16 -0700512 for (addr = start; addr < end && !err; addr += PAGE_SIZE) {
Hugh Dickins9ba69292009-09-21 17:02:20 -0700513 if (ksm_test_exit(vma->vm_mm))
514 break;
Hugh Dickinsd952b792009-09-21 17:02:16 -0700515 if (signal_pending(current))
516 err = -ERESTARTSYS;
517 else
518 err = break_ksm(vma, addr);
519 }
520 return err;
Izik Eidus31dbd012009-09-21 17:02:03 -0700521}
522
Hugh Dickins2ffd8672009-09-21 17:02:23 -0700523#ifdef CONFIG_SYSFS
524/*
525 * Only called through the sysfs control interface:
526 */
Hugh Dickinsd952b792009-09-21 17:02:16 -0700527static int unmerge_and_remove_all_rmap_items(void)
Izik Eidus31dbd012009-09-21 17:02:03 -0700528{
529 struct mm_slot *mm_slot;
530 struct mm_struct *mm;
531 struct vm_area_struct *vma;
Hugh Dickinsd952b792009-09-21 17:02:16 -0700532 int err = 0;
Izik Eidus31dbd012009-09-21 17:02:03 -0700533
Hugh Dickinsd952b792009-09-21 17:02:16 -0700534 spin_lock(&ksm_mmlist_lock);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700535 ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next,
Hugh Dickinsd952b792009-09-21 17:02:16 -0700536 struct mm_slot, mm_list);
537 spin_unlock(&ksm_mmlist_lock);
538
Hugh Dickins9ba69292009-09-21 17:02:20 -0700539 for (mm_slot = ksm_scan.mm_slot;
540 mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) {
Izik Eidus31dbd012009-09-21 17:02:03 -0700541 mm = mm_slot->mm;
542 down_read(&mm->mmap_sem);
543 for (vma = mm->mmap; vma; vma = vma->vm_next) {
Hugh Dickins9ba69292009-09-21 17:02:20 -0700544 if (ksm_test_exit(mm))
545 break;
Izik Eidus31dbd012009-09-21 17:02:03 -0700546 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
547 continue;
Hugh Dickinsd952b792009-09-21 17:02:16 -0700548 err = unmerge_ksm_pages(vma,
549 vma->vm_start, vma->vm_end);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700550 if (err)
551 goto error;
Izik Eidus31dbd012009-09-21 17:02:03 -0700552 }
Hugh Dickins9ba69292009-09-21 17:02:20 -0700553
Hugh Dickins81464e302009-09-21 17:02:15 -0700554 remove_trailing_rmap_items(mm_slot, mm_slot->rmap_list.next);
Hugh Dickinsd952b792009-09-21 17:02:16 -0700555
556 spin_lock(&ksm_mmlist_lock);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700557 ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next,
Hugh Dickinsd952b792009-09-21 17:02:16 -0700558 struct mm_slot, mm_list);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700559 if (ksm_test_exit(mm)) {
560 hlist_del(&mm_slot->link);
561 list_del(&mm_slot->mm_list);
562 spin_unlock(&ksm_mmlist_lock);
563
564 free_mm_slot(mm_slot);
565 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
566 up_read(&mm->mmap_sem);
567 mmdrop(mm);
568 } else {
569 spin_unlock(&ksm_mmlist_lock);
570 up_read(&mm->mmap_sem);
571 }
Izik Eidus31dbd012009-09-21 17:02:03 -0700572 }
573
Hugh Dickinsd952b792009-09-21 17:02:16 -0700574 ksm_scan.seqnr = 0;
Hugh Dickins9ba69292009-09-21 17:02:20 -0700575 return 0;
576
577error:
578 up_read(&mm->mmap_sem);
Izik Eidus31dbd012009-09-21 17:02:03 -0700579 spin_lock(&ksm_mmlist_lock);
Hugh Dickinsd952b792009-09-21 17:02:16 -0700580 ksm_scan.mm_slot = &ksm_mm_head;
Izik Eidus31dbd012009-09-21 17:02:03 -0700581 spin_unlock(&ksm_mmlist_lock);
Hugh Dickinsd952b792009-09-21 17:02:16 -0700582 return err;
Izik Eidus31dbd012009-09-21 17:02:03 -0700583}
Hugh Dickins2ffd8672009-09-21 17:02:23 -0700584#endif /* CONFIG_SYSFS */
Izik Eidus31dbd012009-09-21 17:02:03 -0700585
Izik Eidus31dbd012009-09-21 17:02:03 -0700586static u32 calc_checksum(struct page *page)
587{
588 u32 checksum;
589 void *addr = kmap_atomic(page, KM_USER0);
590 checksum = jhash2(addr, PAGE_SIZE / 4, 17);
591 kunmap_atomic(addr, KM_USER0);
592 return checksum;
593}
594
595static int memcmp_pages(struct page *page1, struct page *page2)
596{
597 char *addr1, *addr2;
598 int ret;
599
600 addr1 = kmap_atomic(page1, KM_USER0);
601 addr2 = kmap_atomic(page2, KM_USER1);
602 ret = memcmp(addr1, addr2, PAGE_SIZE);
603 kunmap_atomic(addr2, KM_USER1);
604 kunmap_atomic(addr1, KM_USER0);
605 return ret;
606}
607
608static inline int pages_identical(struct page *page1, struct page *page2)
609{
610 return !memcmp_pages(page1, page2);
611}
612
613static int write_protect_page(struct vm_area_struct *vma, struct page *page,
614 pte_t *orig_pte)
615{
616 struct mm_struct *mm = vma->vm_mm;
617 unsigned long addr;
618 pte_t *ptep;
619 spinlock_t *ptl;
620 int swapped;
621 int err = -EFAULT;
622
623 addr = page_address_in_vma(page, vma);
624 if (addr == -EFAULT)
625 goto out;
626
627 ptep = page_check_address(page, mm, addr, &ptl, 0);
628 if (!ptep)
629 goto out;
630
631 if (pte_write(*ptep)) {
632 pte_t entry;
633
634 swapped = PageSwapCache(page);
635 flush_cache_page(vma, addr, page_to_pfn(page));
636 /*
637 * Ok this is tricky, when get_user_pages_fast() run it doesnt
638 * take any lock, therefore the check that we are going to make
639 * with the pagecount against the mapcount is racey and
640 * O_DIRECT can happen right after the check.
641 * So we clear the pte and flush the tlb before the check
642 * this assure us that no O_DIRECT can happen after the check
643 * or in the middle of the check.
644 */
645 entry = ptep_clear_flush(vma, addr, ptep);
646 /*
647 * Check that no O_DIRECT or similar I/O is in progress on the
648 * page
649 */
650 if ((page_mapcount(page) + 2 + swapped) != page_count(page)) {
651 set_pte_at_notify(mm, addr, ptep, entry);
652 goto out_unlock;
653 }
654 entry = pte_wrprotect(entry);
655 set_pte_at_notify(mm, addr, ptep, entry);
656 }
657 *orig_pte = *ptep;
658 err = 0;
659
660out_unlock:
661 pte_unmap_unlock(ptep, ptl);
662out:
663 return err;
664}
665
666/**
667 * replace_page - replace page in vma by new ksm page
668 * @vma: vma that holds the pte pointing to oldpage
669 * @oldpage: the page we are replacing by newpage
670 * @newpage: the ksm page we replace oldpage by
671 * @orig_pte: the original value of the pte
672 *
673 * Returns 0 on success, -EFAULT on failure.
674 */
675static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
676 struct page *newpage, pte_t orig_pte)
677{
678 struct mm_struct *mm = vma->vm_mm;
679 pgd_t *pgd;
680 pud_t *pud;
681 pmd_t *pmd;
682 pte_t *ptep;
683 spinlock_t *ptl;
684 unsigned long addr;
685 pgprot_t prot;
686 int err = -EFAULT;
687
688 prot = vm_get_page_prot(vma->vm_flags & ~VM_WRITE);
689
690 addr = page_address_in_vma(oldpage, vma);
691 if (addr == -EFAULT)
692 goto out;
693
694 pgd = pgd_offset(mm, addr);
695 if (!pgd_present(*pgd))
696 goto out;
697
698 pud = pud_offset(pgd, addr);
699 if (!pud_present(*pud))
700 goto out;
701
702 pmd = pmd_offset(pud, addr);
703 if (!pmd_present(*pmd))
704 goto out;
705
706 ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
707 if (!pte_same(*ptep, orig_pte)) {
708 pte_unmap_unlock(ptep, ptl);
709 goto out;
710 }
711
712 get_page(newpage);
713 page_add_ksm_rmap(newpage);
714
715 flush_cache_page(vma, addr, pte_pfn(*ptep));
716 ptep_clear_flush(vma, addr, ptep);
717 set_pte_at_notify(mm, addr, ptep, mk_pte(newpage, prot));
718
719 page_remove_rmap(oldpage);
720 put_page(oldpage);
721
722 pte_unmap_unlock(ptep, ptl);
723 err = 0;
724out:
725 return err;
726}
727
728/*
729 * try_to_merge_one_page - take two pages and merge them into one
730 * @vma: the vma that hold the pte pointing into oldpage
731 * @oldpage: the page that we want to replace with newpage
732 * @newpage: the page that we want to map instead of oldpage
733 *
734 * Note:
735 * oldpage should be a PageAnon page, while newpage should be a PageKsm page,
736 * or a newly allocated kernel page which page_add_ksm_rmap will make PageKsm.
737 *
738 * This function returns 0 if the pages were merged, -EFAULT otherwise.
739 */
740static int try_to_merge_one_page(struct vm_area_struct *vma,
741 struct page *oldpage,
742 struct page *newpage)
743{
744 pte_t orig_pte = __pte(0);
745 int err = -EFAULT;
746
747 if (!(vma->vm_flags & VM_MERGEABLE))
748 goto out;
749
750 if (!PageAnon(oldpage))
751 goto out;
752
753 get_page(newpage);
754 get_page(oldpage);
755
756 /*
757 * We need the page lock to read a stable PageSwapCache in
758 * write_protect_page(). We use trylock_page() instead of
759 * lock_page() because we don't want to wait here - we
760 * prefer to continue scanning and merging different pages,
761 * then come back to this page when it is unlocked.
762 */
763 if (!trylock_page(oldpage))
764 goto out_putpage;
765 /*
766 * If this anonymous page is mapped only here, its pte may need
767 * to be write-protected. If it's mapped elsewhere, all of its
768 * ptes are necessarily already write-protected. But in either
769 * case, we need to lock and check page_count is not raised.
770 */
771 if (write_protect_page(vma, oldpage, &orig_pte)) {
772 unlock_page(oldpage);
773 goto out_putpage;
774 }
775 unlock_page(oldpage);
776
777 if (pages_identical(oldpage, newpage))
778 err = replace_page(vma, oldpage, newpage, orig_pte);
779
780out_putpage:
781 put_page(oldpage);
782 put_page(newpage);
783out:
784 return err;
785}
786
787/*
Hugh Dickins81464e302009-09-21 17:02:15 -0700788 * try_to_merge_with_ksm_page - like try_to_merge_two_pages,
789 * but no new kernel page is allocated: kpage must already be a ksm page.
790 */
791static int try_to_merge_with_ksm_page(struct mm_struct *mm1,
792 unsigned long addr1,
793 struct page *page1,
794 struct page *kpage)
795{
796 struct vm_area_struct *vma;
797 int err = -EFAULT;
798
799 down_read(&mm1->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700800 if (ksm_test_exit(mm1))
801 goto out;
802
Hugh Dickins81464e302009-09-21 17:02:15 -0700803 vma = find_vma(mm1, addr1);
804 if (!vma || vma->vm_start > addr1)
805 goto out;
806
807 err = try_to_merge_one_page(vma, page1, kpage);
808out:
809 up_read(&mm1->mmap_sem);
810 return err;
811}
812
813/*
Izik Eidus31dbd012009-09-21 17:02:03 -0700814 * try_to_merge_two_pages - take two identical pages and prepare them
815 * to be merged into one page.
816 *
817 * This function returns 0 if we successfully mapped two identical pages
818 * into one page, -EFAULT otherwise.
819 *
820 * Note that this function allocates a new kernel page: if one of the pages
821 * is already a ksm page, try_to_merge_with_ksm_page should be used.
822 */
823static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
824 struct page *page1, struct mm_struct *mm2,
825 unsigned long addr2, struct page *page2)
826{
827 struct vm_area_struct *vma;
828 struct page *kpage;
829 int err = -EFAULT;
830
831 /*
832 * The number of nodes in the stable tree
833 * is the number of kernel pages that we hold.
834 */
835 if (ksm_max_kernel_pages &&
Hugh Dickinsb4028262009-09-21 17:02:09 -0700836 ksm_max_kernel_pages <= ksm_pages_shared)
Izik Eidus31dbd012009-09-21 17:02:03 -0700837 return err;
838
839 kpage = alloc_page(GFP_HIGHUSER);
840 if (!kpage)
841 return err;
842
843 down_read(&mm1->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -0700844 if (ksm_test_exit(mm1)) {
845 up_read(&mm1->mmap_sem);
846 goto out;
847 }
Izik Eidus31dbd012009-09-21 17:02:03 -0700848 vma = find_vma(mm1, addr1);
849 if (!vma || vma->vm_start > addr1) {
Izik Eidus31dbd012009-09-21 17:02:03 -0700850 up_read(&mm1->mmap_sem);
Hugh Dickins81464e302009-09-21 17:02:15 -0700851 goto out;
Izik Eidus31dbd012009-09-21 17:02:03 -0700852 }
853
854 copy_user_highpage(kpage, page1, addr1, vma);
855 err = try_to_merge_one_page(vma, page1, kpage);
856 up_read(&mm1->mmap_sem);
857
858 if (!err) {
Hugh Dickins81464e302009-09-21 17:02:15 -0700859 err = try_to_merge_with_ksm_page(mm2, addr2, page2, kpage);
Izik Eidus31dbd012009-09-21 17:02:03 -0700860 /*
Hugh Dickins81464e302009-09-21 17:02:15 -0700861 * If that fails, we have a ksm page with only one pte
862 * pointing to it: so break it.
Izik Eidus31dbd012009-09-21 17:02:03 -0700863 */
864 if (err)
865 break_cow(mm1, addr1);
Izik Eidus31dbd012009-09-21 17:02:03 -0700866 }
Hugh Dickins81464e302009-09-21 17:02:15 -0700867out:
Izik Eidus31dbd012009-09-21 17:02:03 -0700868 put_page(kpage);
869 return err;
870}
871
872/*
Izik Eidus31dbd012009-09-21 17:02:03 -0700873 * stable_tree_search - search page inside the stable tree
874 * @page: the page that we are searching identical pages to.
875 * @page2: pointer into identical page that we are holding inside the stable
876 * tree that we have found.
877 * @rmap_item: the reverse mapping item
878 *
879 * This function checks if there is a page inside the stable tree
880 * with identical content to the page that we are scanning right now.
881 *
882 * This function return rmap_item pointer to the identical item if found,
883 * NULL otherwise.
884 */
885static struct rmap_item *stable_tree_search(struct page *page,
886 struct page **page2,
887 struct rmap_item *rmap_item)
888{
889 struct rb_node *node = root_stable_tree.rb_node;
890
891 while (node) {
892 struct rmap_item *tree_rmap_item, *next_rmap_item;
893 int ret;
894
895 tree_rmap_item = rb_entry(node, struct rmap_item, node);
896 while (tree_rmap_item) {
897 BUG_ON(!in_stable_tree(tree_rmap_item));
898 cond_resched();
899 page2[0] = get_ksm_page(tree_rmap_item);
900 if (page2[0])
901 break;
902 next_rmap_item = tree_rmap_item->next;
903 remove_rmap_item_from_tree(tree_rmap_item);
904 tree_rmap_item = next_rmap_item;
905 }
906 if (!tree_rmap_item)
907 return NULL;
908
909 ret = memcmp_pages(page, page2[0]);
910
911 if (ret < 0) {
912 put_page(page2[0]);
913 node = node->rb_left;
914 } else if (ret > 0) {
915 put_page(page2[0]);
916 node = node->rb_right;
917 } else {
918 return tree_rmap_item;
919 }
920 }
921
922 return NULL;
923}
924
925/*
926 * stable_tree_insert - insert rmap_item pointing to new ksm page
927 * into the stable tree.
928 *
929 * @page: the page that we are searching identical page to inside the stable
930 * tree.
931 * @rmap_item: pointer to the reverse mapping item.
932 *
933 * This function returns rmap_item if success, NULL otherwise.
934 */
935static struct rmap_item *stable_tree_insert(struct page *page,
936 struct rmap_item *rmap_item)
937{
938 struct rb_node **new = &root_stable_tree.rb_node;
939 struct rb_node *parent = NULL;
940
941 while (*new) {
942 struct rmap_item *tree_rmap_item, *next_rmap_item;
943 struct page *tree_page;
944 int ret;
945
946 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
947 while (tree_rmap_item) {
948 BUG_ON(!in_stable_tree(tree_rmap_item));
949 cond_resched();
950 tree_page = get_ksm_page(tree_rmap_item);
951 if (tree_page)
952 break;
953 next_rmap_item = tree_rmap_item->next;
954 remove_rmap_item_from_tree(tree_rmap_item);
955 tree_rmap_item = next_rmap_item;
956 }
957 if (!tree_rmap_item)
958 return NULL;
959
960 ret = memcmp_pages(page, tree_page);
961 put_page(tree_page);
962
963 parent = *new;
964 if (ret < 0)
965 new = &parent->rb_left;
966 else if (ret > 0)
967 new = &parent->rb_right;
968 else {
969 /*
970 * It is not a bug that stable_tree_search() didn't
971 * find this node: because at that time our page was
972 * not yet write-protected, so may have changed since.
973 */
974 return NULL;
975 }
976 }
977
Izik Eidus31dbd012009-09-21 17:02:03 -0700978 rmap_item->address |= NODE_FLAG | STABLE_FLAG;
979 rmap_item->next = NULL;
980 rb_link_node(&rmap_item->node, parent, new);
981 rb_insert_color(&rmap_item->node, &root_stable_tree);
982
Hugh Dickinse178dfd2009-09-21 17:02:10 -0700983 ksm_pages_shared++;
Izik Eidus31dbd012009-09-21 17:02:03 -0700984 return rmap_item;
985}
986
987/*
988 * unstable_tree_search_insert - search and insert items into the unstable tree.
989 *
990 * @page: the page that we are going to search for identical page or to insert
991 * into the unstable tree
992 * @page2: pointer into identical page that was found inside the unstable tree
993 * @rmap_item: the reverse mapping item of page
994 *
995 * This function searches for a page in the unstable tree identical to the
996 * page currently being scanned; and if no identical page is found in the
997 * tree, we insert rmap_item as a new object into the unstable tree.
998 *
999 * This function returns pointer to rmap_item found to be identical
1000 * to the currently scanned page, NULL otherwise.
1001 *
1002 * This function does both searching and inserting, because they share
1003 * the same walking algorithm in an rbtree.
1004 */
1005static struct rmap_item *unstable_tree_search_insert(struct page *page,
1006 struct page **page2,
1007 struct rmap_item *rmap_item)
1008{
1009 struct rb_node **new = &root_unstable_tree.rb_node;
1010 struct rb_node *parent = NULL;
1011
1012 while (*new) {
1013 struct rmap_item *tree_rmap_item;
1014 int ret;
1015
Hugh Dickinsd178f272009-11-09 15:58:23 +00001016 cond_resched();
Izik Eidus31dbd012009-09-21 17:02:03 -07001017 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
1018 page2[0] = get_mergeable_page(tree_rmap_item);
1019 if (!page2[0])
1020 return NULL;
1021
1022 /*
1023 * Don't substitute an unswappable ksm page
1024 * just for one good swappable forked page.
1025 */
1026 if (page == page2[0]) {
1027 put_page(page2[0]);
1028 return NULL;
1029 }
1030
1031 ret = memcmp_pages(page, page2[0]);
1032
1033 parent = *new;
1034 if (ret < 0) {
1035 put_page(page2[0]);
1036 new = &parent->rb_left;
1037 } else if (ret > 0) {
1038 put_page(page2[0]);
1039 new = &parent->rb_right;
1040 } else {
1041 return tree_rmap_item;
1042 }
1043 }
1044
1045 rmap_item->address |= NODE_FLAG;
1046 rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK);
1047 rb_link_node(&rmap_item->node, parent, new);
1048 rb_insert_color(&rmap_item->node, &root_unstable_tree);
1049
Hugh Dickins473b0ce2009-09-21 17:02:11 -07001050 ksm_pages_unshared++;
Izik Eidus31dbd012009-09-21 17:02:03 -07001051 return NULL;
1052}
1053
1054/*
1055 * stable_tree_append - add another rmap_item to the linked list of
1056 * rmap_items hanging off a given node of the stable tree, all sharing
1057 * the same ksm page.
1058 */
1059static void stable_tree_append(struct rmap_item *rmap_item,
1060 struct rmap_item *tree_rmap_item)
1061{
1062 rmap_item->next = tree_rmap_item->next;
1063 rmap_item->prev = tree_rmap_item;
1064
1065 if (tree_rmap_item->next)
1066 tree_rmap_item->next->prev = rmap_item;
1067
1068 tree_rmap_item->next = rmap_item;
1069 rmap_item->address |= STABLE_FLAG;
Hugh Dickinse178dfd2009-09-21 17:02:10 -07001070
1071 ksm_pages_sharing++;
Izik Eidus31dbd012009-09-21 17:02:03 -07001072}
1073
1074/*
Hugh Dickins81464e302009-09-21 17:02:15 -07001075 * cmp_and_merge_page - first see if page can be merged into the stable tree;
1076 * if not, compare checksum to previous and if it's the same, see if page can
1077 * be inserted into the unstable tree, or merged with a page already there and
1078 * both transferred to the stable tree.
Izik Eidus31dbd012009-09-21 17:02:03 -07001079 *
1080 * @page: the page that we are searching identical page to.
1081 * @rmap_item: the reverse mapping into the virtual address of this page
1082 */
1083static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
1084{
1085 struct page *page2[1];
1086 struct rmap_item *tree_rmap_item;
1087 unsigned int checksum;
1088 int err;
1089
Hugh Dickins93d17712009-12-14 17:59:16 -08001090 remove_rmap_item_from_tree(rmap_item);
Izik Eidus31dbd012009-09-21 17:02:03 -07001091
1092 /* We first start with searching the page inside the stable tree */
1093 tree_rmap_item = stable_tree_search(page, page2, rmap_item);
1094 if (tree_rmap_item) {
Hugh Dickinse178dfd2009-09-21 17:02:10 -07001095 if (page == page2[0]) /* forked */
Izik Eidus31dbd012009-09-21 17:02:03 -07001096 err = 0;
Hugh Dickinse178dfd2009-09-21 17:02:10 -07001097 else
Izik Eidus31dbd012009-09-21 17:02:03 -07001098 err = try_to_merge_with_ksm_page(rmap_item->mm,
1099 rmap_item->address,
1100 page, page2[0]);
1101 put_page(page2[0]);
1102
1103 if (!err) {
1104 /*
1105 * The page was successfully merged:
1106 * add its rmap_item to the stable tree.
1107 */
1108 stable_tree_append(rmap_item, tree_rmap_item);
1109 }
1110 return;
1111 }
1112
1113 /*
1114 * A ksm page might have got here by fork, but its other
1115 * references have already been removed from the stable tree.
Hugh Dickinsd952b792009-09-21 17:02:16 -07001116 * Or it might be left over from a break_ksm which failed
1117 * when the mem_cgroup had reached its limit: try again now.
Izik Eidus31dbd012009-09-21 17:02:03 -07001118 */
1119 if (PageKsm(page))
1120 break_cow(rmap_item->mm, rmap_item->address);
1121
1122 /*
1123 * In case the hash value of the page was changed from the last time we
1124 * have calculated it, this page to be changed frequely, therefore we
1125 * don't want to insert it to the unstable tree, and we don't want to
1126 * waste our time to search if there is something identical to it there.
1127 */
1128 checksum = calc_checksum(page);
1129 if (rmap_item->oldchecksum != checksum) {
1130 rmap_item->oldchecksum = checksum;
1131 return;
1132 }
1133
1134 tree_rmap_item = unstable_tree_search_insert(page, page2, rmap_item);
1135 if (tree_rmap_item) {
1136 err = try_to_merge_two_pages(rmap_item->mm,
1137 rmap_item->address, page,
1138 tree_rmap_item->mm,
1139 tree_rmap_item->address, page2[0]);
1140 /*
1141 * As soon as we merge this page, we want to remove the
1142 * rmap_item of the page we have merged with from the unstable
1143 * tree, and insert it instead as new node in the stable tree.
1144 */
1145 if (!err) {
Hugh Dickins93d17712009-12-14 17:59:16 -08001146 remove_rmap_item_from_tree(tree_rmap_item);
Hugh Dickins473b0ce2009-09-21 17:02:11 -07001147
Izik Eidus31dbd012009-09-21 17:02:03 -07001148 /*
1149 * If we fail to insert the page into the stable tree,
1150 * we will have 2 virtual addresses that are pointing
1151 * to a ksm page left outside the stable tree,
1152 * in which case we need to break_cow on both.
1153 */
1154 if (stable_tree_insert(page2[0], tree_rmap_item))
1155 stable_tree_append(rmap_item, tree_rmap_item);
1156 else {
1157 break_cow(tree_rmap_item->mm,
1158 tree_rmap_item->address);
1159 break_cow(rmap_item->mm, rmap_item->address);
Izik Eidus31dbd012009-09-21 17:02:03 -07001160 }
1161 }
1162
1163 put_page(page2[0]);
1164 }
1165}
1166
1167static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot,
1168 struct list_head *cur,
1169 unsigned long addr)
1170{
1171 struct rmap_item *rmap_item;
1172
1173 while (cur != &mm_slot->rmap_list) {
1174 rmap_item = list_entry(cur, struct rmap_item, link);
Hugh Dickins93d17712009-12-14 17:59:16 -08001175 if ((rmap_item->address & PAGE_MASK) == addr)
Izik Eidus31dbd012009-09-21 17:02:03 -07001176 return rmap_item;
Izik Eidus31dbd012009-09-21 17:02:03 -07001177 if (rmap_item->address > addr)
1178 break;
1179 cur = cur->next;
1180 remove_rmap_item_from_tree(rmap_item);
1181 list_del(&rmap_item->link);
1182 free_rmap_item(rmap_item);
1183 }
1184
1185 rmap_item = alloc_rmap_item();
1186 if (rmap_item) {
1187 /* It has already been zeroed */
1188 rmap_item->mm = mm_slot->mm;
1189 rmap_item->address = addr;
1190 list_add_tail(&rmap_item->link, cur);
1191 }
1192 return rmap_item;
1193}
1194
1195static struct rmap_item *scan_get_next_rmap_item(struct page **page)
1196{
1197 struct mm_struct *mm;
1198 struct mm_slot *slot;
1199 struct vm_area_struct *vma;
1200 struct rmap_item *rmap_item;
1201
1202 if (list_empty(&ksm_mm_head.mm_list))
1203 return NULL;
1204
1205 slot = ksm_scan.mm_slot;
1206 if (slot == &ksm_mm_head) {
1207 root_unstable_tree = RB_ROOT;
1208
1209 spin_lock(&ksm_mmlist_lock);
1210 slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list);
1211 ksm_scan.mm_slot = slot;
1212 spin_unlock(&ksm_mmlist_lock);
1213next_mm:
1214 ksm_scan.address = 0;
1215 ksm_scan.rmap_item = list_entry(&slot->rmap_list,
1216 struct rmap_item, link);
1217 }
1218
1219 mm = slot->mm;
1220 down_read(&mm->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001221 if (ksm_test_exit(mm))
1222 vma = NULL;
1223 else
1224 vma = find_vma(mm, ksm_scan.address);
1225
1226 for (; vma; vma = vma->vm_next) {
Izik Eidus31dbd012009-09-21 17:02:03 -07001227 if (!(vma->vm_flags & VM_MERGEABLE))
1228 continue;
1229 if (ksm_scan.address < vma->vm_start)
1230 ksm_scan.address = vma->vm_start;
1231 if (!vma->anon_vma)
1232 ksm_scan.address = vma->vm_end;
1233
1234 while (ksm_scan.address < vma->vm_end) {
Hugh Dickins9ba69292009-09-21 17:02:20 -07001235 if (ksm_test_exit(mm))
1236 break;
Izik Eidus31dbd012009-09-21 17:02:03 -07001237 *page = follow_page(vma, ksm_scan.address, FOLL_GET);
1238 if (*page && PageAnon(*page)) {
1239 flush_anon_page(vma, *page, ksm_scan.address);
1240 flush_dcache_page(*page);
1241 rmap_item = get_next_rmap_item(slot,
1242 ksm_scan.rmap_item->link.next,
1243 ksm_scan.address);
1244 if (rmap_item) {
1245 ksm_scan.rmap_item = rmap_item;
1246 ksm_scan.address += PAGE_SIZE;
1247 } else
1248 put_page(*page);
1249 up_read(&mm->mmap_sem);
1250 return rmap_item;
1251 }
1252 if (*page)
1253 put_page(*page);
1254 ksm_scan.address += PAGE_SIZE;
1255 cond_resched();
1256 }
1257 }
1258
Hugh Dickins9ba69292009-09-21 17:02:20 -07001259 if (ksm_test_exit(mm)) {
1260 ksm_scan.address = 0;
1261 ksm_scan.rmap_item = list_entry(&slot->rmap_list,
1262 struct rmap_item, link);
1263 }
Izik Eidus31dbd012009-09-21 17:02:03 -07001264 /*
1265 * Nuke all the rmap_items that are above this current rmap:
1266 * because there were no VM_MERGEABLE vmas with such addresses.
1267 */
1268 remove_trailing_rmap_items(slot, ksm_scan.rmap_item->link.next);
Izik Eidus31dbd012009-09-21 17:02:03 -07001269
1270 spin_lock(&ksm_mmlist_lock);
Hugh Dickinscd551f92009-09-21 17:02:17 -07001271 ksm_scan.mm_slot = list_entry(slot->mm_list.next,
1272 struct mm_slot, mm_list);
1273 if (ksm_scan.address == 0) {
1274 /*
1275 * We've completed a full scan of all vmas, holding mmap_sem
1276 * throughout, and found no VM_MERGEABLE: so do the same as
1277 * __ksm_exit does to remove this mm from all our lists now.
Hugh Dickins9ba69292009-09-21 17:02:20 -07001278 * This applies either when cleaning up after __ksm_exit
1279 * (but beware: we can reach here even before __ksm_exit),
1280 * or when all VM_MERGEABLE areas have been unmapped (and
1281 * mmap_sem then protects against race with MADV_MERGEABLE).
Hugh Dickinscd551f92009-09-21 17:02:17 -07001282 */
1283 hlist_del(&slot->link);
1284 list_del(&slot->mm_list);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001285 spin_unlock(&ksm_mmlist_lock);
1286
Hugh Dickinscd551f92009-09-21 17:02:17 -07001287 free_mm_slot(slot);
1288 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001289 up_read(&mm->mmap_sem);
1290 mmdrop(mm);
1291 } else {
1292 spin_unlock(&ksm_mmlist_lock);
1293 up_read(&mm->mmap_sem);
Hugh Dickinscd551f92009-09-21 17:02:17 -07001294 }
Izik Eidus31dbd012009-09-21 17:02:03 -07001295
1296 /* Repeat until we've completed scanning the whole list */
Hugh Dickinscd551f92009-09-21 17:02:17 -07001297 slot = ksm_scan.mm_slot;
Izik Eidus31dbd012009-09-21 17:02:03 -07001298 if (slot != &ksm_mm_head)
1299 goto next_mm;
1300
Izik Eidus31dbd012009-09-21 17:02:03 -07001301 ksm_scan.seqnr++;
1302 return NULL;
1303}
1304
1305/**
1306 * ksm_do_scan - the ksm scanner main worker function.
1307 * @scan_npages - number of pages we want to scan before we return.
1308 */
1309static void ksm_do_scan(unsigned int scan_npages)
1310{
1311 struct rmap_item *rmap_item;
1312 struct page *page;
1313
1314 while (scan_npages--) {
1315 cond_resched();
1316 rmap_item = scan_get_next_rmap_item(&page);
1317 if (!rmap_item)
1318 return;
1319 if (!PageKsm(page) || !in_stable_tree(rmap_item))
1320 cmp_and_merge_page(page, rmap_item);
Hugh Dickins26465d32009-09-21 17:02:12 -07001321 else if (page_mapcount(page) == 1) {
1322 /*
1323 * Replace now-unshared ksm page by ordinary page.
1324 */
1325 break_cow(rmap_item->mm, rmap_item->address);
1326 remove_rmap_item_from_tree(rmap_item);
1327 rmap_item->oldchecksum = calc_checksum(page);
1328 }
Izik Eidus31dbd012009-09-21 17:02:03 -07001329 put_page(page);
1330 }
1331}
1332
Hugh Dickins6e158382009-09-21 17:02:14 -07001333static int ksmd_should_run(void)
1334{
1335 return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list);
1336}
1337
Izik Eidus31dbd012009-09-21 17:02:03 -07001338static int ksm_scan_thread(void *nothing)
1339{
Izik Eidus339aa622009-09-21 17:02:07 -07001340 set_user_nice(current, 5);
Izik Eidus31dbd012009-09-21 17:02:03 -07001341
1342 while (!kthread_should_stop()) {
Hugh Dickins6e158382009-09-21 17:02:14 -07001343 mutex_lock(&ksm_thread_mutex);
1344 if (ksmd_should_run())
Izik Eidus31dbd012009-09-21 17:02:03 -07001345 ksm_do_scan(ksm_thread_pages_to_scan);
Hugh Dickins6e158382009-09-21 17:02:14 -07001346 mutex_unlock(&ksm_thread_mutex);
1347
1348 if (ksmd_should_run()) {
Izik Eidus31dbd012009-09-21 17:02:03 -07001349 schedule_timeout_interruptible(
1350 msecs_to_jiffies(ksm_thread_sleep_millisecs));
1351 } else {
1352 wait_event_interruptible(ksm_thread_wait,
Hugh Dickins6e158382009-09-21 17:02:14 -07001353 ksmd_should_run() || kthread_should_stop());
Izik Eidus31dbd012009-09-21 17:02:03 -07001354 }
1355 }
1356 return 0;
1357}
1358
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001359int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
1360 unsigned long end, int advice, unsigned long *vm_flags)
1361{
1362 struct mm_struct *mm = vma->vm_mm;
Hugh Dickinsd952b792009-09-21 17:02:16 -07001363 int err;
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001364
1365 switch (advice) {
1366 case MADV_MERGEABLE:
1367 /*
1368 * Be somewhat over-protective for now!
1369 */
1370 if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE |
1371 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1372 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1373 VM_MIXEDMAP | VM_SAO))
1374 return 0; /* just ignore the advice */
1375
Hugh Dickinsd952b792009-09-21 17:02:16 -07001376 if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) {
1377 err = __ksm_enter(mm);
1378 if (err)
1379 return err;
1380 }
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001381
1382 *vm_flags |= VM_MERGEABLE;
1383 break;
1384
1385 case MADV_UNMERGEABLE:
1386 if (!(*vm_flags & VM_MERGEABLE))
1387 return 0; /* just ignore the advice */
1388
Hugh Dickinsd952b792009-09-21 17:02:16 -07001389 if (vma->anon_vma) {
1390 err = unmerge_ksm_pages(vma, start, end);
1391 if (err)
1392 return err;
1393 }
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001394
1395 *vm_flags &= ~VM_MERGEABLE;
1396 break;
1397 }
1398
1399 return 0;
1400}
1401
1402int __ksm_enter(struct mm_struct *mm)
1403{
Hugh Dickins6e158382009-09-21 17:02:14 -07001404 struct mm_slot *mm_slot;
1405 int needs_wakeup;
1406
1407 mm_slot = alloc_mm_slot();
Izik Eidus31dbd012009-09-21 17:02:03 -07001408 if (!mm_slot)
1409 return -ENOMEM;
1410
Hugh Dickins6e158382009-09-21 17:02:14 -07001411 /* Check ksm_run too? Would need tighter locking */
1412 needs_wakeup = list_empty(&ksm_mm_head.mm_list);
1413
Izik Eidus31dbd012009-09-21 17:02:03 -07001414 spin_lock(&ksm_mmlist_lock);
1415 insert_to_mm_slots_hash(mm, mm_slot);
1416 /*
1417 * Insert just behind the scanning cursor, to let the area settle
1418 * down a little; when fork is followed by immediate exec, we don't
1419 * want ksmd to waste time setting up and tearing down an rmap_list.
1420 */
1421 list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list);
1422 spin_unlock(&ksm_mmlist_lock);
1423
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001424 set_bit(MMF_VM_MERGEABLE, &mm->flags);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001425 atomic_inc(&mm->mm_count);
Hugh Dickins6e158382009-09-21 17:02:14 -07001426
1427 if (needs_wakeup)
1428 wake_up_interruptible(&ksm_thread_wait);
1429
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001430 return 0;
1431}
1432
Andrea Arcangeli1c2fb7a2009-09-21 17:02:22 -07001433void __ksm_exit(struct mm_struct *mm)
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001434{
Hugh Dickinscd551f92009-09-21 17:02:17 -07001435 struct mm_slot *mm_slot;
Hugh Dickins9ba69292009-09-21 17:02:20 -07001436 int easy_to_free = 0;
Hugh Dickinscd551f92009-09-21 17:02:17 -07001437
Izik Eidus31dbd012009-09-21 17:02:03 -07001438 /*
Hugh Dickins9ba69292009-09-21 17:02:20 -07001439 * This process is exiting: if it's straightforward (as is the
1440 * case when ksmd was never running), free mm_slot immediately.
1441 * But if it's at the cursor or has rmap_items linked to it, use
1442 * mmap_sem to synchronize with any break_cows before pagetables
1443 * are freed, and leave the mm_slot on the list for ksmd to free.
1444 * Beware: ksm may already have noticed it exiting and freed the slot.
Izik Eidus31dbd012009-09-21 17:02:03 -07001445 */
Hugh Dickins9ba69292009-09-21 17:02:20 -07001446
Hugh Dickinscd551f92009-09-21 17:02:17 -07001447 spin_lock(&ksm_mmlist_lock);
1448 mm_slot = get_mm_slot(mm);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001449 if (mm_slot && ksm_scan.mm_slot != mm_slot) {
1450 if (list_empty(&mm_slot->rmap_list)) {
1451 hlist_del(&mm_slot->link);
1452 list_del(&mm_slot->mm_list);
1453 easy_to_free = 1;
1454 } else {
1455 list_move(&mm_slot->mm_list,
1456 &ksm_scan.mm_slot->mm_list);
1457 }
Hugh Dickinscd551f92009-09-21 17:02:17 -07001458 }
Hugh Dickinscd551f92009-09-21 17:02:17 -07001459 spin_unlock(&ksm_mmlist_lock);
1460
Hugh Dickins9ba69292009-09-21 17:02:20 -07001461 if (easy_to_free) {
1462 free_mm_slot(mm_slot);
1463 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
1464 mmdrop(mm);
1465 } else if (mm_slot) {
Hugh Dickins9ba69292009-09-21 17:02:20 -07001466 down_write(&mm->mmap_sem);
1467 up_write(&mm->mmap_sem);
Hugh Dickins9ba69292009-09-21 17:02:20 -07001468 }
Hugh Dickinsf8af4da2009-09-21 17:01:57 -07001469}
Izik Eidus31dbd012009-09-21 17:02:03 -07001470
Hugh Dickins2ffd8672009-09-21 17:02:23 -07001471#ifdef CONFIG_SYSFS
1472/*
1473 * This all compiles without CONFIG_SYSFS, but is a waste of space.
1474 */
1475
Izik Eidus31dbd012009-09-21 17:02:03 -07001476#define KSM_ATTR_RO(_name) \
1477 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
1478#define KSM_ATTR(_name) \
1479 static struct kobj_attribute _name##_attr = \
1480 __ATTR(_name, 0644, _name##_show, _name##_store)
1481
1482static ssize_t sleep_millisecs_show(struct kobject *kobj,
1483 struct kobj_attribute *attr, char *buf)
1484{
1485 return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs);
1486}
1487
1488static ssize_t sleep_millisecs_store(struct kobject *kobj,
1489 struct kobj_attribute *attr,
1490 const char *buf, size_t count)
1491{
1492 unsigned long msecs;
1493 int err;
1494
1495 err = strict_strtoul(buf, 10, &msecs);
1496 if (err || msecs > UINT_MAX)
1497 return -EINVAL;
1498
1499 ksm_thread_sleep_millisecs = msecs;
1500
1501 return count;
1502}
1503KSM_ATTR(sleep_millisecs);
1504
1505static ssize_t pages_to_scan_show(struct kobject *kobj,
1506 struct kobj_attribute *attr, char *buf)
1507{
1508 return sprintf(buf, "%u\n", ksm_thread_pages_to_scan);
1509}
1510
1511static ssize_t pages_to_scan_store(struct kobject *kobj,
1512 struct kobj_attribute *attr,
1513 const char *buf, size_t count)
1514{
1515 int err;
1516 unsigned long nr_pages;
1517
1518 err = strict_strtoul(buf, 10, &nr_pages);
1519 if (err || nr_pages > UINT_MAX)
1520 return -EINVAL;
1521
1522 ksm_thread_pages_to_scan = nr_pages;
1523
1524 return count;
1525}
1526KSM_ATTR(pages_to_scan);
1527
1528static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr,
1529 char *buf)
1530{
1531 return sprintf(buf, "%u\n", ksm_run);
1532}
1533
1534static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
1535 const char *buf, size_t count)
1536{
1537 int err;
1538 unsigned long flags;
1539
1540 err = strict_strtoul(buf, 10, &flags);
1541 if (err || flags > UINT_MAX)
1542 return -EINVAL;
1543 if (flags > KSM_RUN_UNMERGE)
1544 return -EINVAL;
1545
1546 /*
1547 * KSM_RUN_MERGE sets ksmd running, and 0 stops it running.
1548 * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items,
Hugh Dickinsb4028262009-09-21 17:02:09 -07001549 * breaking COW to free the unswappable pages_shared (but leaves
Izik Eidus31dbd012009-09-21 17:02:03 -07001550 * mm_slots on the list for when ksmd may be set running again).
1551 */
1552
1553 mutex_lock(&ksm_thread_mutex);
1554 if (ksm_run != flags) {
1555 ksm_run = flags;
Hugh Dickinsd952b792009-09-21 17:02:16 -07001556 if (flags & KSM_RUN_UNMERGE) {
Hugh Dickins35451be2009-09-21 17:02:27 -07001557 current->flags |= PF_OOM_ORIGIN;
Hugh Dickinsd952b792009-09-21 17:02:16 -07001558 err = unmerge_and_remove_all_rmap_items();
Hugh Dickins35451be2009-09-21 17:02:27 -07001559 current->flags &= ~PF_OOM_ORIGIN;
Hugh Dickinsd952b792009-09-21 17:02:16 -07001560 if (err) {
1561 ksm_run = KSM_RUN_STOP;
1562 count = err;
1563 }
1564 }
Izik Eidus31dbd012009-09-21 17:02:03 -07001565 }
1566 mutex_unlock(&ksm_thread_mutex);
1567
1568 if (flags & KSM_RUN_MERGE)
1569 wake_up_interruptible(&ksm_thread_wait);
1570
1571 return count;
1572}
1573KSM_ATTR(run);
1574
Izik Eidus31dbd012009-09-21 17:02:03 -07001575static ssize_t max_kernel_pages_store(struct kobject *kobj,
1576 struct kobj_attribute *attr,
1577 const char *buf, size_t count)
1578{
1579 int err;
1580 unsigned long nr_pages;
1581
1582 err = strict_strtoul(buf, 10, &nr_pages);
1583 if (err)
1584 return -EINVAL;
1585
1586 ksm_max_kernel_pages = nr_pages;
1587
1588 return count;
1589}
1590
1591static ssize_t max_kernel_pages_show(struct kobject *kobj,
1592 struct kobj_attribute *attr, char *buf)
1593{
1594 return sprintf(buf, "%lu\n", ksm_max_kernel_pages);
1595}
1596KSM_ATTR(max_kernel_pages);
1597
Hugh Dickinsb4028262009-09-21 17:02:09 -07001598static ssize_t pages_shared_show(struct kobject *kobj,
1599 struct kobj_attribute *attr, char *buf)
1600{
1601 return sprintf(buf, "%lu\n", ksm_pages_shared);
1602}
1603KSM_ATTR_RO(pages_shared);
1604
1605static ssize_t pages_sharing_show(struct kobject *kobj,
1606 struct kobj_attribute *attr, char *buf)
1607{
Hugh Dickinse178dfd2009-09-21 17:02:10 -07001608 return sprintf(buf, "%lu\n", ksm_pages_sharing);
Hugh Dickinsb4028262009-09-21 17:02:09 -07001609}
1610KSM_ATTR_RO(pages_sharing);
1611
Hugh Dickins473b0ce2009-09-21 17:02:11 -07001612static ssize_t pages_unshared_show(struct kobject *kobj,
1613 struct kobj_attribute *attr, char *buf)
1614{
1615 return sprintf(buf, "%lu\n", ksm_pages_unshared);
1616}
1617KSM_ATTR_RO(pages_unshared);
1618
1619static ssize_t pages_volatile_show(struct kobject *kobj,
1620 struct kobj_attribute *attr, char *buf)
1621{
1622 long ksm_pages_volatile;
1623
1624 ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared
1625 - ksm_pages_sharing - ksm_pages_unshared;
1626 /*
1627 * It was not worth any locking to calculate that statistic,
1628 * but it might therefore sometimes be negative: conceal that.
1629 */
1630 if (ksm_pages_volatile < 0)
1631 ksm_pages_volatile = 0;
1632 return sprintf(buf, "%ld\n", ksm_pages_volatile);
1633}
1634KSM_ATTR_RO(pages_volatile);
1635
1636static ssize_t full_scans_show(struct kobject *kobj,
1637 struct kobj_attribute *attr, char *buf)
1638{
1639 return sprintf(buf, "%lu\n", ksm_scan.seqnr);
1640}
1641KSM_ATTR_RO(full_scans);
1642
Izik Eidus31dbd012009-09-21 17:02:03 -07001643static struct attribute *ksm_attrs[] = {
1644 &sleep_millisecs_attr.attr,
1645 &pages_to_scan_attr.attr,
1646 &run_attr.attr,
Izik Eidus31dbd012009-09-21 17:02:03 -07001647 &max_kernel_pages_attr.attr,
Hugh Dickinsb4028262009-09-21 17:02:09 -07001648 &pages_shared_attr.attr,
1649 &pages_sharing_attr.attr,
Hugh Dickins473b0ce2009-09-21 17:02:11 -07001650 &pages_unshared_attr.attr,
1651 &pages_volatile_attr.attr,
1652 &full_scans_attr.attr,
Izik Eidus31dbd012009-09-21 17:02:03 -07001653 NULL,
1654};
1655
1656static struct attribute_group ksm_attr_group = {
1657 .attrs = ksm_attrs,
1658 .name = "ksm",
1659};
Hugh Dickins2ffd8672009-09-21 17:02:23 -07001660#endif /* CONFIG_SYSFS */
Izik Eidus31dbd012009-09-21 17:02:03 -07001661
1662static int __init ksm_init(void)
1663{
1664 struct task_struct *ksm_thread;
1665 int err;
1666
Hugh Dickinsc73602a2009-10-07 16:32:22 -07001667 ksm_max_kernel_pages = totalram_pages / 4;
Izik Eidus2c6854f2009-09-23 15:56:04 -07001668
Izik Eidus31dbd012009-09-21 17:02:03 -07001669 err = ksm_slab_init();
1670 if (err)
1671 goto out;
1672
1673 err = mm_slots_hash_init();
1674 if (err)
1675 goto out_free1;
1676
1677 ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd");
1678 if (IS_ERR(ksm_thread)) {
1679 printk(KERN_ERR "ksm: creating kthread failed\n");
1680 err = PTR_ERR(ksm_thread);
1681 goto out_free2;
1682 }
1683
Hugh Dickins2ffd8672009-09-21 17:02:23 -07001684#ifdef CONFIG_SYSFS
Izik Eidus31dbd012009-09-21 17:02:03 -07001685 err = sysfs_create_group(mm_kobj, &ksm_attr_group);
1686 if (err) {
1687 printk(KERN_ERR "ksm: register sysfs failed\n");
Hugh Dickins2ffd8672009-09-21 17:02:23 -07001688 kthread_stop(ksm_thread);
1689 goto out_free2;
Izik Eidus31dbd012009-09-21 17:02:03 -07001690 }
Hugh Dickinsc73602a2009-10-07 16:32:22 -07001691#else
1692 ksm_run = KSM_RUN_MERGE; /* no way for user to start it */
1693
Hugh Dickins2ffd8672009-09-21 17:02:23 -07001694#endif /* CONFIG_SYSFS */
Izik Eidus31dbd012009-09-21 17:02:03 -07001695
1696 return 0;
1697
Izik Eidus31dbd012009-09-21 17:02:03 -07001698out_free2:
1699 mm_slots_hash_free();
1700out_free1:
1701 ksm_slab_free();
1702out:
1703 return err;
1704}
1705module_init(ksm_init)