Commit | Line | Data |
---|---|---|
f8af4da3 | 1 | /* |
31dbd01f IE |
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 | * | |
36b2528d | 7 | * Copyright (C) 2008-2009 Red Hat, Inc. |
31dbd01f IE |
8 | * Authors: |
9 | * Izik Eidus | |
10 | * Andrea Arcangeli | |
11 | * Chris Wright | |
36b2528d | 12 | * Hugh Dickins |
31dbd01f IE |
13 | * |
14 | * This work is licensed under the terms of the GNU GPL, version 2. | |
f8af4da3 HD |
15 | */ |
16 | ||
17 | #include <linux/errno.h> | |
31dbd01f IE |
18 | #include <linux/mm.h> |
19 | #include <linux/fs.h> | |
f8af4da3 | 20 | #include <linux/mman.h> |
31dbd01f IE |
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> | |
2c6854fd | 33 | #include <linux/swap.h> |
f8af4da3 HD |
34 | #include <linux/ksm.h> |
35 | ||
31dbd01f IE |
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 | |
6514d511 | 82 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
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; | |
6514d511 | 88 | struct rmap_item *rmap_list; |
31dbd01f IE |
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 | |
6514d511 | 96 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
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; | |
6514d511 | 104 | struct rmap_item **rmap_list; |
31dbd01f IE |
105 | unsigned long seqnr; |
106 | }; | |
107 | ||
7b6ba2c7 HD |
108 | /** |
109 | * struct stable_node - node of the stable rbtree | |
08beca44 | 110 | * @page: pointer to struct page of the ksm page |
7b6ba2c7 HD |
111 | * @node: rb node of this ksm page in the stable tree |
112 | * @hlist: hlist head of rmap_items using this ksm page | |
113 | */ | |
114 | struct stable_node { | |
08beca44 | 115 | struct page *page; |
7b6ba2c7 HD |
116 | struct rb_node node; |
117 | struct hlist_head hlist; | |
118 | }; | |
119 | ||
31dbd01f IE |
120 | /** |
121 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 HD |
122 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
123 | * @filler: unused space we're making available in this patch | |
31dbd01f IE |
124 | * @mm: the memory structure this rmap_item is pointing into |
125 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
126 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
127 | * @node: rb node of this rmap_item in the unstable tree |
128 | * @head: pointer to stable_node heading this list in the stable tree | |
129 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
130 | */ |
131 | struct rmap_item { | |
6514d511 HD |
132 | struct rmap_item *rmap_list; |
133 | unsigned long filler; | |
31dbd01f IE |
134 | struct mm_struct *mm; |
135 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 136 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 137 | union { |
7b6ba2c7 HD |
138 | struct rb_node node; /* when node of unstable tree */ |
139 | struct { /* when listed from stable tree */ | |
140 | struct stable_node *head; | |
141 | struct hlist_node hlist; | |
142 | }; | |
31dbd01f IE |
143 | }; |
144 | }; | |
145 | ||
146 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
147 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
148 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
149 | |
150 | /* The stable and unstable tree heads */ | |
151 | static struct rb_root root_stable_tree = RB_ROOT; | |
152 | static struct rb_root root_unstable_tree = RB_ROOT; | |
153 | ||
154 | #define MM_SLOTS_HASH_HEADS 1024 | |
155 | static struct hlist_head *mm_slots_hash; | |
156 | ||
157 | static struct mm_slot ksm_mm_head = { | |
158 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
159 | }; | |
160 | static struct ksm_scan ksm_scan = { | |
161 | .mm_slot = &ksm_mm_head, | |
162 | }; | |
163 | ||
164 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 165 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
166 | static struct kmem_cache *mm_slot_cache; |
167 | ||
168 | /* The number of nodes in the stable tree */ | |
b4028260 | 169 | static unsigned long ksm_pages_shared; |
31dbd01f | 170 | |
e178dfde | 171 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 172 | static unsigned long ksm_pages_sharing; |
31dbd01f | 173 | |
473b0ce4 HD |
174 | /* The number of nodes in the unstable tree */ |
175 | static unsigned long ksm_pages_unshared; | |
176 | ||
177 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
178 | static unsigned long ksm_rmap_items; | |
179 | ||
31dbd01f | 180 | /* Limit on the number of unswappable pages used */ |
2c6854fd | 181 | static unsigned long ksm_max_kernel_pages; |
31dbd01f IE |
182 | |
183 | /* Number of pages ksmd should scan in one batch */ | |
2c6854fd | 184 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
185 | |
186 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 187 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
188 | |
189 | #define KSM_RUN_STOP 0 | |
190 | #define KSM_RUN_MERGE 1 | |
191 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 192 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
193 | |
194 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
195 | static DEFINE_MUTEX(ksm_thread_mutex); | |
196 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
197 | ||
198 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
199 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
200 | (__flags), NULL) | |
201 | ||
202 | static int __init ksm_slab_init(void) | |
203 | { | |
204 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
205 | if (!rmap_item_cache) | |
206 | goto out; | |
207 | ||
7b6ba2c7 HD |
208 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
209 | if (!stable_node_cache) | |
210 | goto out_free1; | |
211 | ||
31dbd01f IE |
212 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
213 | if (!mm_slot_cache) | |
7b6ba2c7 | 214 | goto out_free2; |
31dbd01f IE |
215 | |
216 | return 0; | |
217 | ||
7b6ba2c7 HD |
218 | out_free2: |
219 | kmem_cache_destroy(stable_node_cache); | |
220 | out_free1: | |
31dbd01f IE |
221 | kmem_cache_destroy(rmap_item_cache); |
222 | out: | |
223 | return -ENOMEM; | |
224 | } | |
225 | ||
226 | static void __init ksm_slab_free(void) | |
227 | { | |
228 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 229 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
230 | kmem_cache_destroy(rmap_item_cache); |
231 | mm_slot_cache = NULL; | |
232 | } | |
233 | ||
234 | static inline struct rmap_item *alloc_rmap_item(void) | |
235 | { | |
473b0ce4 HD |
236 | struct rmap_item *rmap_item; |
237 | ||
238 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
239 | if (rmap_item) | |
240 | ksm_rmap_items++; | |
241 | return rmap_item; | |
31dbd01f IE |
242 | } |
243 | ||
244 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
245 | { | |
473b0ce4 | 246 | ksm_rmap_items--; |
31dbd01f IE |
247 | rmap_item->mm = NULL; /* debug safety */ |
248 | kmem_cache_free(rmap_item_cache, rmap_item); | |
249 | } | |
250 | ||
7b6ba2c7 HD |
251 | static inline struct stable_node *alloc_stable_node(void) |
252 | { | |
253 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
254 | } | |
255 | ||
256 | static inline void free_stable_node(struct stable_node *stable_node) | |
257 | { | |
258 | kmem_cache_free(stable_node_cache, stable_node); | |
259 | } | |
260 | ||
31dbd01f IE |
261 | static inline struct mm_slot *alloc_mm_slot(void) |
262 | { | |
263 | if (!mm_slot_cache) /* initialization failed */ | |
264 | return NULL; | |
265 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
266 | } | |
267 | ||
268 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
269 | { | |
270 | kmem_cache_free(mm_slot_cache, mm_slot); | |
271 | } | |
272 | ||
273 | static int __init mm_slots_hash_init(void) | |
274 | { | |
275 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), | |
276 | GFP_KERNEL); | |
277 | if (!mm_slots_hash) | |
278 | return -ENOMEM; | |
279 | return 0; | |
280 | } | |
281 | ||
282 | static void __init mm_slots_hash_free(void) | |
283 | { | |
284 | kfree(mm_slots_hash); | |
285 | } | |
286 | ||
287 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
288 | { | |
289 | struct mm_slot *mm_slot; | |
290 | struct hlist_head *bucket; | |
291 | struct hlist_node *node; | |
292 | ||
293 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
294 | % MM_SLOTS_HASH_HEADS]; | |
295 | hlist_for_each_entry(mm_slot, node, bucket, link) { | |
296 | if (mm == mm_slot->mm) | |
297 | return mm_slot; | |
298 | } | |
299 | return NULL; | |
300 | } | |
301 | ||
302 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
303 | struct mm_slot *mm_slot) | |
304 | { | |
305 | struct hlist_head *bucket; | |
306 | ||
307 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
308 | % MM_SLOTS_HASH_HEADS]; | |
309 | mm_slot->mm = mm; | |
31dbd01f IE |
310 | hlist_add_head(&mm_slot->link, bucket); |
311 | } | |
312 | ||
313 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
314 | { | |
315 | return rmap_item->address & STABLE_FLAG; | |
316 | } | |
317 | ||
a913e182 HD |
318 | /* |
319 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
320 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
321 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
322 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
323 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
324 | * places for correctness, in some places just to avoid unnecessary work. | |
325 | */ | |
326 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
327 | { | |
328 | return atomic_read(&mm->mm_users) == 0; | |
329 | } | |
330 | ||
31dbd01f IE |
331 | /* |
332 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
333 | * | |
334 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
335 | * put_page(page); | |
336 | * | |
337 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
338 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
339 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
340 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
341 | */ | |
d952b791 | 342 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
343 | { |
344 | struct page *page; | |
d952b791 | 345 | int ret = 0; |
31dbd01f IE |
346 | |
347 | do { | |
348 | cond_resched(); | |
349 | page = follow_page(vma, addr, FOLL_GET); | |
350 | if (!page) | |
351 | break; | |
352 | if (PageKsm(page)) | |
353 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
354 | FAULT_FLAG_WRITE); | |
355 | else | |
356 | ret = VM_FAULT_WRITE; | |
357 | put_page(page); | |
d952b791 HD |
358 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
359 | /* | |
360 | * We must loop because handle_mm_fault() may back out if there's | |
361 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
362 | * | |
363 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
364 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
365 | * but note that a concurrent fault might break PageKsm for us. | |
366 | * | |
367 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
368 | * backing file, which also invalidates anonymous pages: that's | |
369 | * okay, that truncation will have unmapped the PageKsm for us. | |
370 | * | |
371 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
372 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
373 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
374 | * to user; and ksmd, having no mm, would never be chosen for that. | |
375 | * | |
376 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
377 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
378 | * even ksmd can fail in this way - though it's usually breaking ksm | |
379 | * just to undo a merge it made a moment before, so unlikely to oom. | |
380 | * | |
381 | * That's a pity: we might therefore have more kernel pages allocated | |
382 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
383 | * will retry to break_cow on each pass, so should recover the page | |
384 | * in due course. The important thing is to not let VM_MERGEABLE | |
385 | * be cleared while any such pages might remain in the area. | |
386 | */ | |
387 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
388 | } |
389 | ||
8dd3557a | 390 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 391 | { |
8dd3557a HD |
392 | struct mm_struct *mm = rmap_item->mm; |
393 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
394 | struct vm_area_struct *vma; |
395 | ||
81464e30 | 396 | down_read(&mm->mmap_sem); |
9ba69294 HD |
397 | if (ksm_test_exit(mm)) |
398 | goto out; | |
31dbd01f IE |
399 | vma = find_vma(mm, addr); |
400 | if (!vma || vma->vm_start > addr) | |
81464e30 | 401 | goto out; |
31dbd01f | 402 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 403 | goto out; |
31dbd01f | 404 | break_ksm(vma, addr); |
81464e30 | 405 | out: |
31dbd01f IE |
406 | up_read(&mm->mmap_sem); |
407 | } | |
408 | ||
409 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
410 | { | |
411 | struct mm_struct *mm = rmap_item->mm; | |
412 | unsigned long addr = rmap_item->address; | |
413 | struct vm_area_struct *vma; | |
414 | struct page *page; | |
415 | ||
416 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
417 | if (ksm_test_exit(mm)) |
418 | goto out; | |
31dbd01f IE |
419 | vma = find_vma(mm, addr); |
420 | if (!vma || vma->vm_start > addr) | |
421 | goto out; | |
422 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
423 | goto out; | |
424 | ||
425 | page = follow_page(vma, addr, FOLL_GET); | |
426 | if (!page) | |
427 | goto out; | |
428 | if (PageAnon(page)) { | |
429 | flush_anon_page(vma, page, addr); | |
430 | flush_dcache_page(page); | |
431 | } else { | |
432 | put_page(page); | |
433 | out: page = NULL; | |
434 | } | |
435 | up_read(&mm->mmap_sem); | |
436 | return page; | |
437 | } | |
438 | ||
31dbd01f IE |
439 | /* |
440 | * Removing rmap_item from stable or unstable tree. | |
441 | * This function will clean the information from the stable/unstable tree. | |
442 | */ | |
443 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
444 | { | |
7b6ba2c7 HD |
445 | if (rmap_item->address & STABLE_FLAG) { |
446 | struct stable_node *stable_node; | |
31dbd01f | 447 | |
7b6ba2c7 HD |
448 | stable_node = rmap_item->head; |
449 | hlist_del(&rmap_item->hlist); | |
450 | if (stable_node->hlist.first) | |
e178dfde | 451 | ksm_pages_sharing--; |
7b6ba2c7 | 452 | else { |
08beca44 HD |
453 | set_page_stable_node(stable_node->page, NULL); |
454 | put_page(stable_node->page); | |
455 | ||
7b6ba2c7 HD |
456 | rb_erase(&stable_node->node, &root_stable_tree); |
457 | free_stable_node(stable_node); | |
458 | ksm_pages_shared--; | |
31dbd01f IE |
459 | } |
460 | ||
93d17715 | 461 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 462 | |
7b6ba2c7 | 463 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
464 | unsigned char age; |
465 | /* | |
9ba69294 | 466 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 467 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
468 | * But be careful when an mm is exiting: do the rb_erase |
469 | * if this rmap_item was inserted by this scan, rather | |
470 | * than left over from before. | |
31dbd01f IE |
471 | */ |
472 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 473 | BUG_ON(age > 1); |
31dbd01f IE |
474 | if (!age) |
475 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
93d17715 | 476 | |
473b0ce4 | 477 | ksm_pages_unshared--; |
93d17715 | 478 | rmap_item->address &= PAGE_MASK; |
31dbd01f IE |
479 | } |
480 | ||
31dbd01f IE |
481 | cond_resched(); /* we're called from many long loops */ |
482 | } | |
483 | ||
31dbd01f | 484 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 485 | struct rmap_item **rmap_list) |
31dbd01f | 486 | { |
6514d511 HD |
487 | while (*rmap_list) { |
488 | struct rmap_item *rmap_item = *rmap_list; | |
489 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 490 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
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). | |
81464e30 HD |
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. | |
31dbd01f | 507 | */ |
d952b791 HD |
508 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
509 | unsigned long start, unsigned long end) | |
31dbd01f IE |
510 | { |
511 | unsigned long addr; | |
d952b791 | 512 | int err = 0; |
31dbd01f | 513 | |
d952b791 | 514 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
515 | if (ksm_test_exit(vma->vm_mm)) |
516 | break; | |
d952b791 HD |
517 | if (signal_pending(current)) |
518 | err = -ERESTARTSYS; | |
519 | else | |
520 | err = break_ksm(vma, addr); | |
521 | } | |
522 | return err; | |
31dbd01f IE |
523 | } |
524 | ||
2ffd8679 HD |
525 | #ifdef CONFIG_SYSFS |
526 | /* | |
527 | * Only called through the sysfs control interface: | |
528 | */ | |
d952b791 | 529 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
530 | { |
531 | struct mm_slot *mm_slot; | |
532 | struct mm_struct *mm; | |
533 | struct vm_area_struct *vma; | |
d952b791 HD |
534 | int err = 0; |
535 | ||
536 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 537 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
538 | struct mm_slot, mm_list); |
539 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 540 | |
9ba69294 HD |
541 | for (mm_slot = ksm_scan.mm_slot; |
542 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
543 | mm = mm_slot->mm; |
544 | down_read(&mm->mmap_sem); | |
545 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
546 | if (ksm_test_exit(mm)) |
547 | break; | |
31dbd01f IE |
548 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
549 | continue; | |
d952b791 HD |
550 | err = unmerge_ksm_pages(vma, |
551 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
552 | if (err) |
553 | goto error; | |
31dbd01f | 554 | } |
9ba69294 | 555 | |
6514d511 | 556 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
557 | |
558 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 559 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 560 | struct mm_slot, mm_list); |
9ba69294 HD |
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 | } | |
31dbd01f IE |
574 | } |
575 | ||
d952b791 | 576 | ksm_scan.seqnr = 0; |
9ba69294 HD |
577 | return 0; |
578 | ||
579 | error: | |
580 | up_read(&mm->mmap_sem); | |
31dbd01f | 581 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 582 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 583 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 584 | return err; |
31dbd01f | 585 | } |
2ffd8679 | 586 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 587 | |
31dbd01f IE |
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 | */ | |
31e855ea | 652 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
31dbd01f IE |
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 | |
8dd3557a HD |
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 | |
31dbd01f IE |
673 | * @orig_pte: the original value of the pte |
674 | * | |
675 | * Returns 0 on success, -EFAULT on failure. | |
676 | */ | |
8dd3557a HD |
677 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
678 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
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; | |
31dbd01f IE |
687 | int err = -EFAULT; |
688 | ||
8dd3557a | 689 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
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 | ||
8dd3557a HD |
711 | get_page(kpage); |
712 | page_add_ksm_rmap(kpage); | |
31dbd01f IE |
713 | |
714 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
715 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 716 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 717 | |
8dd3557a HD |
718 | page_remove_rmap(page); |
719 | put_page(page); | |
31dbd01f IE |
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 | |
8dd3557a HD |
729 | * @vma: the vma that holds the pte pointing to page |
730 | * @page: the PageAnon page that we want to replace with kpage | |
08beca44 | 731 | * @kpage: the PageKsm page that we want to map instead of page |
31dbd01f IE |
732 | * |
733 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
734 | */ | |
735 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 736 | struct page *page, struct page *kpage) |
31dbd01f IE |
737 | { |
738 | pte_t orig_pte = __pte(0); | |
739 | int err = -EFAULT; | |
740 | ||
741 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
742 | goto out; | |
8dd3557a | 743 | if (!PageAnon(page)) |
31dbd01f IE |
744 | goto out; |
745 | ||
31dbd01f IE |
746 | /* |
747 | * We need the page lock to read a stable PageSwapCache in | |
748 | * write_protect_page(). We use trylock_page() instead of | |
749 | * lock_page() because we don't want to wait here - we | |
750 | * prefer to continue scanning and merging different pages, | |
751 | * then come back to this page when it is unlocked. | |
752 | */ | |
8dd3557a | 753 | if (!trylock_page(page)) |
31e855ea | 754 | goto out; |
31dbd01f IE |
755 | /* |
756 | * If this anonymous page is mapped only here, its pte may need | |
757 | * to be write-protected. If it's mapped elsewhere, all of its | |
758 | * ptes are necessarily already write-protected. But in either | |
759 | * case, we need to lock and check page_count is not raised. | |
760 | */ | |
8dd3557a HD |
761 | if (write_protect_page(vma, page, &orig_pte) == 0 && |
762 | pages_identical(page, kpage)) | |
763 | err = replace_page(vma, page, kpage, orig_pte); | |
31dbd01f | 764 | |
8dd3557a | 765 | unlock_page(page); |
31dbd01f IE |
766 | out: |
767 | return err; | |
768 | } | |
769 | ||
81464e30 HD |
770 | /* |
771 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
772 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
773 | * |
774 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 775 | */ |
8dd3557a HD |
776 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
777 | struct page *page, struct page *kpage) | |
81464e30 | 778 | { |
8dd3557a | 779 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
780 | struct vm_area_struct *vma; |
781 | int err = -EFAULT; | |
782 | ||
08beca44 HD |
783 | if (page == kpage) /* ksm page forked */ |
784 | return 0; | |
785 | ||
8dd3557a HD |
786 | down_read(&mm->mmap_sem); |
787 | if (ksm_test_exit(mm)) | |
9ba69294 | 788 | goto out; |
8dd3557a HD |
789 | vma = find_vma(mm, rmap_item->address); |
790 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
791 | goto out; |
792 | ||
8dd3557a | 793 | err = try_to_merge_one_page(vma, page, kpage); |
81464e30 | 794 | out: |
8dd3557a | 795 | up_read(&mm->mmap_sem); |
81464e30 HD |
796 | return err; |
797 | } | |
798 | ||
31dbd01f IE |
799 | /* |
800 | * try_to_merge_two_pages - take two identical pages and prepare them | |
801 | * to be merged into one page. | |
802 | * | |
8dd3557a HD |
803 | * This function returns the kpage if we successfully merged two identical |
804 | * pages into one ksm page, NULL otherwise. | |
31dbd01f IE |
805 | * |
806 | * Note that this function allocates a new kernel page: if one of the pages | |
807 | * is already a ksm page, try_to_merge_with_ksm_page should be used. | |
808 | */ | |
8dd3557a HD |
809 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
810 | struct page *page, | |
811 | struct rmap_item *tree_rmap_item, | |
812 | struct page *tree_page) | |
31dbd01f | 813 | { |
8dd3557a | 814 | struct mm_struct *mm = rmap_item->mm; |
31dbd01f IE |
815 | struct vm_area_struct *vma; |
816 | struct page *kpage; | |
817 | int err = -EFAULT; | |
818 | ||
819 | /* | |
820 | * The number of nodes in the stable tree | |
821 | * is the number of kernel pages that we hold. | |
822 | */ | |
823 | if (ksm_max_kernel_pages && | |
b4028260 | 824 | ksm_max_kernel_pages <= ksm_pages_shared) |
8dd3557a | 825 | return NULL; |
31dbd01f IE |
826 | |
827 | kpage = alloc_page(GFP_HIGHUSER); | |
828 | if (!kpage) | |
8dd3557a | 829 | return NULL; |
31dbd01f | 830 | |
8dd3557a HD |
831 | down_read(&mm->mmap_sem); |
832 | if (ksm_test_exit(mm)) | |
833 | goto up; | |
834 | vma = find_vma(mm, rmap_item->address); | |
835 | if (!vma || vma->vm_start > rmap_item->address) | |
836 | goto up; | |
837 | ||
838 | copy_user_highpage(kpage, page, rmap_item->address, vma); | |
08beca44 HD |
839 | |
840 | set_page_stable_node(kpage, NULL); /* mark it PageKsm */ | |
841 | ||
8dd3557a HD |
842 | err = try_to_merge_one_page(vma, page, kpage); |
843 | up: | |
844 | up_read(&mm->mmap_sem); | |
31dbd01f IE |
845 | |
846 | if (!err) { | |
8dd3557a HD |
847 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
848 | tree_page, kpage); | |
31dbd01f | 849 | /* |
81464e30 HD |
850 | * If that fails, we have a ksm page with only one pte |
851 | * pointing to it: so break it. | |
31dbd01f IE |
852 | */ |
853 | if (err) | |
8dd3557a | 854 | break_cow(rmap_item); |
31dbd01f | 855 | } |
8dd3557a HD |
856 | if (err) { |
857 | put_page(kpage); | |
858 | kpage = NULL; | |
859 | } | |
860 | return kpage; | |
31dbd01f IE |
861 | } |
862 | ||
31dbd01f | 863 | /* |
8dd3557a | 864 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
865 | * |
866 | * This function checks if there is a page inside the stable tree | |
867 | * with identical content to the page that we are scanning right now. | |
868 | * | |
7b6ba2c7 | 869 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
870 | * NULL otherwise. |
871 | */ | |
08beca44 | 872 | static struct stable_node *stable_tree_search(struct page *page) |
31dbd01f IE |
873 | { |
874 | struct rb_node *node = root_stable_tree.rb_node; | |
7b6ba2c7 | 875 | struct stable_node *stable_node; |
31dbd01f | 876 | |
08beca44 HD |
877 | stable_node = page_stable_node(page); |
878 | if (stable_node) { /* ksm page forked */ | |
879 | get_page(page); | |
880 | return stable_node; | |
881 | } | |
882 | ||
31dbd01f | 883 | while (node) { |
31dbd01f IE |
884 | int ret; |
885 | ||
08beca44 | 886 | cond_resched(); |
7b6ba2c7 | 887 | stable_node = rb_entry(node, struct stable_node, node); |
31dbd01f | 888 | |
08beca44 | 889 | ret = memcmp_pages(page, stable_node->page); |
31dbd01f | 890 | |
08beca44 | 891 | if (ret < 0) |
31dbd01f | 892 | node = node->rb_left; |
08beca44 | 893 | else if (ret > 0) |
31dbd01f | 894 | node = node->rb_right; |
08beca44 HD |
895 | else { |
896 | get_page(stable_node->page); | |
7b6ba2c7 | 897 | return stable_node; |
31dbd01f IE |
898 | } |
899 | } | |
900 | ||
901 | return NULL; | |
902 | } | |
903 | ||
904 | /* | |
905 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
906 | * into the stable tree. | |
907 | * | |
7b6ba2c7 HD |
908 | * This function returns the stable tree node just allocated on success, |
909 | * NULL otherwise. | |
31dbd01f | 910 | */ |
7b6ba2c7 | 911 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f IE |
912 | { |
913 | struct rb_node **new = &root_stable_tree.rb_node; | |
914 | struct rb_node *parent = NULL; | |
7b6ba2c7 | 915 | struct stable_node *stable_node; |
31dbd01f IE |
916 | |
917 | while (*new) { | |
31dbd01f IE |
918 | int ret; |
919 | ||
08beca44 | 920 | cond_resched(); |
7b6ba2c7 | 921 | stable_node = rb_entry(*new, struct stable_node, node); |
31dbd01f | 922 | |
08beca44 | 923 | ret = memcmp_pages(kpage, stable_node->page); |
31dbd01f IE |
924 | |
925 | parent = *new; | |
926 | if (ret < 0) | |
927 | new = &parent->rb_left; | |
928 | else if (ret > 0) | |
929 | new = &parent->rb_right; | |
930 | else { | |
931 | /* | |
932 | * It is not a bug that stable_tree_search() didn't | |
933 | * find this node: because at that time our page was | |
934 | * not yet write-protected, so may have changed since. | |
935 | */ | |
936 | return NULL; | |
937 | } | |
938 | } | |
939 | ||
7b6ba2c7 HD |
940 | stable_node = alloc_stable_node(); |
941 | if (!stable_node) | |
942 | return NULL; | |
31dbd01f | 943 | |
7b6ba2c7 HD |
944 | rb_link_node(&stable_node->node, parent, new); |
945 | rb_insert_color(&stable_node->node, &root_stable_tree); | |
946 | ||
947 | INIT_HLIST_HEAD(&stable_node->hlist); | |
948 | ||
08beca44 HD |
949 | get_page(kpage); |
950 | stable_node->page = kpage; | |
951 | set_page_stable_node(kpage, stable_node); | |
952 | ||
7b6ba2c7 | 953 | return stable_node; |
31dbd01f IE |
954 | } |
955 | ||
956 | /* | |
8dd3557a HD |
957 | * unstable_tree_search_insert - search for identical page, |
958 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
959 | * |
960 | * This function searches for a page in the unstable tree identical to the | |
961 | * page currently being scanned; and if no identical page is found in the | |
962 | * tree, we insert rmap_item as a new object into the unstable tree. | |
963 | * | |
964 | * This function returns pointer to rmap_item found to be identical | |
965 | * to the currently scanned page, NULL otherwise. | |
966 | * | |
967 | * This function does both searching and inserting, because they share | |
968 | * the same walking algorithm in an rbtree. | |
969 | */ | |
8dd3557a HD |
970 | static |
971 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
972 | struct page *page, | |
973 | struct page **tree_pagep) | |
974 | ||
31dbd01f IE |
975 | { |
976 | struct rb_node **new = &root_unstable_tree.rb_node; | |
977 | struct rb_node *parent = NULL; | |
978 | ||
979 | while (*new) { | |
980 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 981 | struct page *tree_page; |
31dbd01f IE |
982 | int ret; |
983 | ||
d178f27f | 984 | cond_resched(); |
31dbd01f | 985 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a HD |
986 | tree_page = get_mergeable_page(tree_rmap_item); |
987 | if (!tree_page) | |
31dbd01f IE |
988 | return NULL; |
989 | ||
990 | /* | |
8dd3557a | 991 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 992 | */ |
8dd3557a HD |
993 | if (page == tree_page) { |
994 | put_page(tree_page); | |
31dbd01f IE |
995 | return NULL; |
996 | } | |
997 | ||
8dd3557a | 998 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
999 | |
1000 | parent = *new; | |
1001 | if (ret < 0) { | |
8dd3557a | 1002 | put_page(tree_page); |
31dbd01f IE |
1003 | new = &parent->rb_left; |
1004 | } else if (ret > 0) { | |
8dd3557a | 1005 | put_page(tree_page); |
31dbd01f IE |
1006 | new = &parent->rb_right; |
1007 | } else { | |
8dd3557a | 1008 | *tree_pagep = tree_page; |
31dbd01f IE |
1009 | return tree_rmap_item; |
1010 | } | |
1011 | } | |
1012 | ||
7b6ba2c7 | 1013 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f IE |
1014 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
1015 | rb_link_node(&rmap_item->node, parent, new); | |
1016 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1017 | ||
473b0ce4 | 1018 | ksm_pages_unshared++; |
31dbd01f IE |
1019 | return NULL; |
1020 | } | |
1021 | ||
1022 | /* | |
1023 | * stable_tree_append - add another rmap_item to the linked list of | |
1024 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1025 | * the same ksm page. | |
1026 | */ | |
1027 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1028 | struct stable_node *stable_node) |
31dbd01f | 1029 | { |
7b6ba2c7 | 1030 | rmap_item->head = stable_node; |
31dbd01f | 1031 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1032 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1033 | |
7b6ba2c7 HD |
1034 | if (rmap_item->hlist.next) |
1035 | ksm_pages_sharing++; | |
1036 | else | |
1037 | ksm_pages_shared++; | |
31dbd01f IE |
1038 | } |
1039 | ||
1040 | /* | |
81464e30 HD |
1041 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1042 | * if not, compare checksum to previous and if it's the same, see if page can | |
1043 | * be inserted into the unstable tree, or merged with a page already there and | |
1044 | * both transferred to the stable tree. | |
31dbd01f IE |
1045 | * |
1046 | * @page: the page that we are searching identical page to. | |
1047 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1048 | */ | |
1049 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1050 | { | |
31dbd01f | 1051 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1052 | struct page *tree_page = NULL; |
7b6ba2c7 | 1053 | struct stable_node *stable_node; |
8dd3557a | 1054 | struct page *kpage; |
31dbd01f IE |
1055 | unsigned int checksum; |
1056 | int err; | |
1057 | ||
93d17715 | 1058 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1059 | |
1060 | /* We first start with searching the page inside the stable tree */ | |
08beca44 | 1061 | stable_node = stable_tree_search(page); |
7b6ba2c7 | 1062 | if (stable_node) { |
08beca44 HD |
1063 | kpage = stable_node->page; |
1064 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); | |
31dbd01f IE |
1065 | if (!err) { |
1066 | /* | |
1067 | * The page was successfully merged: | |
1068 | * add its rmap_item to the stable tree. | |
1069 | */ | |
7b6ba2c7 | 1070 | stable_tree_append(rmap_item, stable_node); |
31dbd01f | 1071 | } |
8dd3557a | 1072 | put_page(kpage); |
31dbd01f IE |
1073 | return; |
1074 | } | |
1075 | ||
1076 | /* | |
1077 | * A ksm page might have got here by fork, but its other | |
1078 | * references have already been removed from the stable tree. | |
d952b791 HD |
1079 | * Or it might be left over from a break_ksm which failed |
1080 | * when the mem_cgroup had reached its limit: try again now. | |
31dbd01f IE |
1081 | */ |
1082 | if (PageKsm(page)) | |
8dd3557a | 1083 | break_cow(rmap_item); |
31dbd01f IE |
1084 | |
1085 | /* | |
1086 | * In case the hash value of the page was changed from the last time we | |
1087 | * have calculated it, this page to be changed frequely, therefore we | |
1088 | * don't want to insert it to the unstable tree, and we don't want to | |
1089 | * waste our time to search if there is something identical to it there. | |
1090 | */ | |
1091 | checksum = calc_checksum(page); | |
1092 | if (rmap_item->oldchecksum != checksum) { | |
1093 | rmap_item->oldchecksum = checksum; | |
1094 | return; | |
1095 | } | |
1096 | ||
8dd3557a HD |
1097 | tree_rmap_item = |
1098 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1099 | if (tree_rmap_item) { |
8dd3557a HD |
1100 | kpage = try_to_merge_two_pages(rmap_item, page, |
1101 | tree_rmap_item, tree_page); | |
1102 | put_page(tree_page); | |
31dbd01f IE |
1103 | /* |
1104 | * As soon as we merge this page, we want to remove the | |
1105 | * rmap_item of the page we have merged with from the unstable | |
1106 | * tree, and insert it instead as new node in the stable tree. | |
1107 | */ | |
8dd3557a | 1108 | if (kpage) { |
93d17715 | 1109 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1110 | |
7b6ba2c7 HD |
1111 | stable_node = stable_tree_insert(kpage); |
1112 | if (stable_node) { | |
1113 | stable_tree_append(tree_rmap_item, stable_node); | |
1114 | stable_tree_append(rmap_item, stable_node); | |
1115 | } | |
1116 | put_page(kpage); | |
1117 | ||
31dbd01f IE |
1118 | /* |
1119 | * If we fail to insert the page into the stable tree, | |
1120 | * we will have 2 virtual addresses that are pointing | |
1121 | * to a ksm page left outside the stable tree, | |
1122 | * in which case we need to break_cow on both. | |
1123 | */ | |
7b6ba2c7 | 1124 | if (!stable_node) { |
8dd3557a HD |
1125 | break_cow(tree_rmap_item); |
1126 | break_cow(rmap_item); | |
31dbd01f IE |
1127 | } |
1128 | } | |
31dbd01f IE |
1129 | } |
1130 | } | |
1131 | ||
1132 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1133 | struct rmap_item **rmap_list, |
31dbd01f IE |
1134 | unsigned long addr) |
1135 | { | |
1136 | struct rmap_item *rmap_item; | |
1137 | ||
6514d511 HD |
1138 | while (*rmap_list) { |
1139 | rmap_item = *rmap_list; | |
93d17715 | 1140 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1141 | return rmap_item; |
31dbd01f IE |
1142 | if (rmap_item->address > addr) |
1143 | break; | |
6514d511 | 1144 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1145 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1146 | free_rmap_item(rmap_item); |
1147 | } | |
1148 | ||
1149 | rmap_item = alloc_rmap_item(); | |
1150 | if (rmap_item) { | |
1151 | /* It has already been zeroed */ | |
1152 | rmap_item->mm = mm_slot->mm; | |
1153 | rmap_item->address = addr; | |
6514d511 HD |
1154 | rmap_item->rmap_list = *rmap_list; |
1155 | *rmap_list = rmap_item; | |
31dbd01f IE |
1156 | } |
1157 | return rmap_item; | |
1158 | } | |
1159 | ||
1160 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1161 | { | |
1162 | struct mm_struct *mm; | |
1163 | struct mm_slot *slot; | |
1164 | struct vm_area_struct *vma; | |
1165 | struct rmap_item *rmap_item; | |
1166 | ||
1167 | if (list_empty(&ksm_mm_head.mm_list)) | |
1168 | return NULL; | |
1169 | ||
1170 | slot = ksm_scan.mm_slot; | |
1171 | if (slot == &ksm_mm_head) { | |
1172 | root_unstable_tree = RB_ROOT; | |
1173 | ||
1174 | spin_lock(&ksm_mmlist_lock); | |
1175 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1176 | ksm_scan.mm_slot = slot; | |
1177 | spin_unlock(&ksm_mmlist_lock); | |
1178 | next_mm: | |
1179 | ksm_scan.address = 0; | |
6514d511 | 1180 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1181 | } |
1182 | ||
1183 | mm = slot->mm; | |
1184 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1185 | if (ksm_test_exit(mm)) |
1186 | vma = NULL; | |
1187 | else | |
1188 | vma = find_vma(mm, ksm_scan.address); | |
1189 | ||
1190 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1191 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1192 | continue; | |
1193 | if (ksm_scan.address < vma->vm_start) | |
1194 | ksm_scan.address = vma->vm_start; | |
1195 | if (!vma->anon_vma) | |
1196 | ksm_scan.address = vma->vm_end; | |
1197 | ||
1198 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1199 | if (ksm_test_exit(mm)) |
1200 | break; | |
31dbd01f IE |
1201 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
1202 | if (*page && PageAnon(*page)) { | |
1203 | flush_anon_page(vma, *page, ksm_scan.address); | |
1204 | flush_dcache_page(*page); | |
1205 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1206 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1207 | if (rmap_item) { |
6514d511 HD |
1208 | ksm_scan.rmap_list = |
1209 | &rmap_item->rmap_list; | |
31dbd01f IE |
1210 | ksm_scan.address += PAGE_SIZE; |
1211 | } else | |
1212 | put_page(*page); | |
1213 | up_read(&mm->mmap_sem); | |
1214 | return rmap_item; | |
1215 | } | |
1216 | if (*page) | |
1217 | put_page(*page); | |
1218 | ksm_scan.address += PAGE_SIZE; | |
1219 | cond_resched(); | |
1220 | } | |
1221 | } | |
1222 | ||
9ba69294 HD |
1223 | if (ksm_test_exit(mm)) { |
1224 | ksm_scan.address = 0; | |
6514d511 | 1225 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1226 | } |
31dbd01f IE |
1227 | /* |
1228 | * Nuke all the rmap_items that are above this current rmap: | |
1229 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1230 | */ | |
6514d511 | 1231 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1232 | |
1233 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1234 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1235 | struct mm_slot, mm_list); | |
1236 | if (ksm_scan.address == 0) { | |
1237 | /* | |
1238 | * We've completed a full scan of all vmas, holding mmap_sem | |
1239 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1240 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1241 | * This applies either when cleaning up after __ksm_exit |
1242 | * (but beware: we can reach here even before __ksm_exit), | |
1243 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1244 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1245 | */ |
1246 | hlist_del(&slot->link); | |
1247 | list_del(&slot->mm_list); | |
9ba69294 HD |
1248 | spin_unlock(&ksm_mmlist_lock); |
1249 | ||
cd551f97 HD |
1250 | free_mm_slot(slot); |
1251 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1252 | up_read(&mm->mmap_sem); |
1253 | mmdrop(mm); | |
1254 | } else { | |
1255 | spin_unlock(&ksm_mmlist_lock); | |
1256 | up_read(&mm->mmap_sem); | |
cd551f97 | 1257 | } |
31dbd01f IE |
1258 | |
1259 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1260 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1261 | if (slot != &ksm_mm_head) |
1262 | goto next_mm; | |
1263 | ||
31dbd01f IE |
1264 | ksm_scan.seqnr++; |
1265 | return NULL; | |
1266 | } | |
1267 | ||
1268 | /** | |
1269 | * ksm_do_scan - the ksm scanner main worker function. | |
1270 | * @scan_npages - number of pages we want to scan before we return. | |
1271 | */ | |
1272 | static void ksm_do_scan(unsigned int scan_npages) | |
1273 | { | |
1274 | struct rmap_item *rmap_item; | |
1275 | struct page *page; | |
1276 | ||
1277 | while (scan_npages--) { | |
1278 | cond_resched(); | |
1279 | rmap_item = scan_get_next_rmap_item(&page); | |
1280 | if (!rmap_item) | |
1281 | return; | |
1282 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1283 | cmp_and_merge_page(page, rmap_item); | |
26465d3e HD |
1284 | else if (page_mapcount(page) == 1) { |
1285 | /* | |
1286 | * Replace now-unshared ksm page by ordinary page. | |
1287 | */ | |
8dd3557a | 1288 | break_cow(rmap_item); |
26465d3e HD |
1289 | remove_rmap_item_from_tree(rmap_item); |
1290 | rmap_item->oldchecksum = calc_checksum(page); | |
1291 | } | |
31dbd01f IE |
1292 | put_page(page); |
1293 | } | |
1294 | } | |
1295 | ||
6e158384 HD |
1296 | static int ksmd_should_run(void) |
1297 | { | |
1298 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1299 | } | |
1300 | ||
31dbd01f IE |
1301 | static int ksm_scan_thread(void *nothing) |
1302 | { | |
339aa624 | 1303 | set_user_nice(current, 5); |
31dbd01f IE |
1304 | |
1305 | while (!kthread_should_stop()) { | |
6e158384 HD |
1306 | mutex_lock(&ksm_thread_mutex); |
1307 | if (ksmd_should_run()) | |
31dbd01f | 1308 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1309 | mutex_unlock(&ksm_thread_mutex); |
1310 | ||
1311 | if (ksmd_should_run()) { | |
31dbd01f IE |
1312 | schedule_timeout_interruptible( |
1313 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1314 | } else { | |
1315 | wait_event_interruptible(ksm_thread_wait, | |
6e158384 | 1316 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1317 | } |
1318 | } | |
1319 | return 0; | |
1320 | } | |
1321 | ||
f8af4da3 HD |
1322 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1323 | unsigned long end, int advice, unsigned long *vm_flags) | |
1324 | { | |
1325 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1326 | int err; |
f8af4da3 HD |
1327 | |
1328 | switch (advice) { | |
1329 | case MADV_MERGEABLE: | |
1330 | /* | |
1331 | * Be somewhat over-protective for now! | |
1332 | */ | |
1333 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1334 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1335 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
1336 | VM_MIXEDMAP | VM_SAO)) | |
1337 | return 0; /* just ignore the advice */ | |
1338 | ||
d952b791 HD |
1339 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1340 | err = __ksm_enter(mm); | |
1341 | if (err) | |
1342 | return err; | |
1343 | } | |
f8af4da3 HD |
1344 | |
1345 | *vm_flags |= VM_MERGEABLE; | |
1346 | break; | |
1347 | ||
1348 | case MADV_UNMERGEABLE: | |
1349 | if (!(*vm_flags & VM_MERGEABLE)) | |
1350 | return 0; /* just ignore the advice */ | |
1351 | ||
d952b791 HD |
1352 | if (vma->anon_vma) { |
1353 | err = unmerge_ksm_pages(vma, start, end); | |
1354 | if (err) | |
1355 | return err; | |
1356 | } | |
f8af4da3 HD |
1357 | |
1358 | *vm_flags &= ~VM_MERGEABLE; | |
1359 | break; | |
1360 | } | |
1361 | ||
1362 | return 0; | |
1363 | } | |
1364 | ||
1365 | int __ksm_enter(struct mm_struct *mm) | |
1366 | { | |
6e158384 HD |
1367 | struct mm_slot *mm_slot; |
1368 | int needs_wakeup; | |
1369 | ||
1370 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1371 | if (!mm_slot) |
1372 | return -ENOMEM; | |
1373 | ||
6e158384 HD |
1374 | /* Check ksm_run too? Would need tighter locking */ |
1375 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1376 | ||
31dbd01f IE |
1377 | spin_lock(&ksm_mmlist_lock); |
1378 | insert_to_mm_slots_hash(mm, mm_slot); | |
1379 | /* | |
1380 | * Insert just behind the scanning cursor, to let the area settle | |
1381 | * down a little; when fork is followed by immediate exec, we don't | |
1382 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1383 | */ | |
1384 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1385 | spin_unlock(&ksm_mmlist_lock); | |
1386 | ||
f8af4da3 | 1387 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1388 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1389 | |
1390 | if (needs_wakeup) | |
1391 | wake_up_interruptible(&ksm_thread_wait); | |
1392 | ||
f8af4da3 HD |
1393 | return 0; |
1394 | } | |
1395 | ||
1c2fb7a4 | 1396 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1397 | { |
cd551f97 | 1398 | struct mm_slot *mm_slot; |
9ba69294 | 1399 | int easy_to_free = 0; |
cd551f97 | 1400 | |
31dbd01f | 1401 | /* |
9ba69294 HD |
1402 | * This process is exiting: if it's straightforward (as is the |
1403 | * case when ksmd was never running), free mm_slot immediately. | |
1404 | * But if it's at the cursor or has rmap_items linked to it, use | |
1405 | * mmap_sem to synchronize with any break_cows before pagetables | |
1406 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1407 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1408 | */ |
9ba69294 | 1409 | |
cd551f97 HD |
1410 | spin_lock(&ksm_mmlist_lock); |
1411 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1412 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1413 | if (!mm_slot->rmap_list) { |
9ba69294 HD |
1414 | hlist_del(&mm_slot->link); |
1415 | list_del(&mm_slot->mm_list); | |
1416 | easy_to_free = 1; | |
1417 | } else { | |
1418 | list_move(&mm_slot->mm_list, | |
1419 | &ksm_scan.mm_slot->mm_list); | |
1420 | } | |
cd551f97 | 1421 | } |
cd551f97 HD |
1422 | spin_unlock(&ksm_mmlist_lock); |
1423 | ||
9ba69294 HD |
1424 | if (easy_to_free) { |
1425 | free_mm_slot(mm_slot); | |
1426 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1427 | mmdrop(mm); | |
1428 | } else if (mm_slot) { | |
9ba69294 HD |
1429 | down_write(&mm->mmap_sem); |
1430 | up_write(&mm->mmap_sem); | |
9ba69294 | 1431 | } |
31dbd01f IE |
1432 | } |
1433 | ||
2ffd8679 HD |
1434 | #ifdef CONFIG_SYSFS |
1435 | /* | |
1436 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1437 | */ | |
1438 | ||
31dbd01f IE |
1439 | #define KSM_ATTR_RO(_name) \ |
1440 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1441 | #define KSM_ATTR(_name) \ | |
1442 | static struct kobj_attribute _name##_attr = \ | |
1443 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1444 | ||
1445 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1446 | struct kobj_attribute *attr, char *buf) | |
1447 | { | |
1448 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1449 | } | |
1450 | ||
1451 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1452 | struct kobj_attribute *attr, | |
1453 | const char *buf, size_t count) | |
1454 | { | |
1455 | unsigned long msecs; | |
1456 | int err; | |
1457 | ||
1458 | err = strict_strtoul(buf, 10, &msecs); | |
1459 | if (err || msecs > UINT_MAX) | |
1460 | return -EINVAL; | |
1461 | ||
1462 | ksm_thread_sleep_millisecs = msecs; | |
1463 | ||
1464 | return count; | |
1465 | } | |
1466 | KSM_ATTR(sleep_millisecs); | |
1467 | ||
1468 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1469 | struct kobj_attribute *attr, char *buf) | |
1470 | { | |
1471 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1472 | } | |
1473 | ||
1474 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1475 | struct kobj_attribute *attr, | |
1476 | const char *buf, size_t count) | |
1477 | { | |
1478 | int err; | |
1479 | unsigned long nr_pages; | |
1480 | ||
1481 | err = strict_strtoul(buf, 10, &nr_pages); | |
1482 | if (err || nr_pages > UINT_MAX) | |
1483 | return -EINVAL; | |
1484 | ||
1485 | ksm_thread_pages_to_scan = nr_pages; | |
1486 | ||
1487 | return count; | |
1488 | } | |
1489 | KSM_ATTR(pages_to_scan); | |
1490 | ||
1491 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1492 | char *buf) | |
1493 | { | |
1494 | return sprintf(buf, "%u\n", ksm_run); | |
1495 | } | |
1496 | ||
1497 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1498 | const char *buf, size_t count) | |
1499 | { | |
1500 | int err; | |
1501 | unsigned long flags; | |
1502 | ||
1503 | err = strict_strtoul(buf, 10, &flags); | |
1504 | if (err || flags > UINT_MAX) | |
1505 | return -EINVAL; | |
1506 | if (flags > KSM_RUN_UNMERGE) | |
1507 | return -EINVAL; | |
1508 | ||
1509 | /* | |
1510 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1511 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
b4028260 | 1512 | * breaking COW to free the unswappable pages_shared (but leaves |
31dbd01f IE |
1513 | * mm_slots on the list for when ksmd may be set running again). |
1514 | */ | |
1515 | ||
1516 | mutex_lock(&ksm_thread_mutex); | |
1517 | if (ksm_run != flags) { | |
1518 | ksm_run = flags; | |
d952b791 | 1519 | if (flags & KSM_RUN_UNMERGE) { |
35451bee | 1520 | current->flags |= PF_OOM_ORIGIN; |
d952b791 | 1521 | err = unmerge_and_remove_all_rmap_items(); |
35451bee | 1522 | current->flags &= ~PF_OOM_ORIGIN; |
d952b791 HD |
1523 | if (err) { |
1524 | ksm_run = KSM_RUN_STOP; | |
1525 | count = err; | |
1526 | } | |
1527 | } | |
31dbd01f IE |
1528 | } |
1529 | mutex_unlock(&ksm_thread_mutex); | |
1530 | ||
1531 | if (flags & KSM_RUN_MERGE) | |
1532 | wake_up_interruptible(&ksm_thread_wait); | |
1533 | ||
1534 | return count; | |
1535 | } | |
1536 | KSM_ATTR(run); | |
1537 | ||
31dbd01f IE |
1538 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
1539 | struct kobj_attribute *attr, | |
1540 | const char *buf, size_t count) | |
1541 | { | |
1542 | int err; | |
1543 | unsigned long nr_pages; | |
1544 | ||
1545 | err = strict_strtoul(buf, 10, &nr_pages); | |
1546 | if (err) | |
1547 | return -EINVAL; | |
1548 | ||
1549 | ksm_max_kernel_pages = nr_pages; | |
1550 | ||
1551 | return count; | |
1552 | } | |
1553 | ||
1554 | static ssize_t max_kernel_pages_show(struct kobject *kobj, | |
1555 | struct kobj_attribute *attr, char *buf) | |
1556 | { | |
1557 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); | |
1558 | } | |
1559 | KSM_ATTR(max_kernel_pages); | |
1560 | ||
b4028260 HD |
1561 | static ssize_t pages_shared_show(struct kobject *kobj, |
1562 | struct kobj_attribute *attr, char *buf) | |
1563 | { | |
1564 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1565 | } | |
1566 | KSM_ATTR_RO(pages_shared); | |
1567 | ||
1568 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1569 | struct kobj_attribute *attr, char *buf) | |
1570 | { | |
e178dfde | 1571 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1572 | } |
1573 | KSM_ATTR_RO(pages_sharing); | |
1574 | ||
473b0ce4 HD |
1575 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1576 | struct kobj_attribute *attr, char *buf) | |
1577 | { | |
1578 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1579 | } | |
1580 | KSM_ATTR_RO(pages_unshared); | |
1581 | ||
1582 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1583 | struct kobj_attribute *attr, char *buf) | |
1584 | { | |
1585 | long ksm_pages_volatile; | |
1586 | ||
1587 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1588 | - ksm_pages_sharing - ksm_pages_unshared; | |
1589 | /* | |
1590 | * It was not worth any locking to calculate that statistic, | |
1591 | * but it might therefore sometimes be negative: conceal that. | |
1592 | */ | |
1593 | if (ksm_pages_volatile < 0) | |
1594 | ksm_pages_volatile = 0; | |
1595 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1596 | } | |
1597 | KSM_ATTR_RO(pages_volatile); | |
1598 | ||
1599 | static ssize_t full_scans_show(struct kobject *kobj, | |
1600 | struct kobj_attribute *attr, char *buf) | |
1601 | { | |
1602 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1603 | } | |
1604 | KSM_ATTR_RO(full_scans); | |
1605 | ||
31dbd01f IE |
1606 | static struct attribute *ksm_attrs[] = { |
1607 | &sleep_millisecs_attr.attr, | |
1608 | &pages_to_scan_attr.attr, | |
1609 | &run_attr.attr, | |
31dbd01f | 1610 | &max_kernel_pages_attr.attr, |
b4028260 HD |
1611 | &pages_shared_attr.attr, |
1612 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1613 | &pages_unshared_attr.attr, |
1614 | &pages_volatile_attr.attr, | |
1615 | &full_scans_attr.attr, | |
31dbd01f IE |
1616 | NULL, |
1617 | }; | |
1618 | ||
1619 | static struct attribute_group ksm_attr_group = { | |
1620 | .attrs = ksm_attrs, | |
1621 | .name = "ksm", | |
1622 | }; | |
2ffd8679 | 1623 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1624 | |
1625 | static int __init ksm_init(void) | |
1626 | { | |
1627 | struct task_struct *ksm_thread; | |
1628 | int err; | |
1629 | ||
c73602ad | 1630 | ksm_max_kernel_pages = totalram_pages / 4; |
2c6854fd | 1631 | |
31dbd01f IE |
1632 | err = ksm_slab_init(); |
1633 | if (err) | |
1634 | goto out; | |
1635 | ||
1636 | err = mm_slots_hash_init(); | |
1637 | if (err) | |
1638 | goto out_free1; | |
1639 | ||
1640 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); | |
1641 | if (IS_ERR(ksm_thread)) { | |
1642 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
1643 | err = PTR_ERR(ksm_thread); | |
1644 | goto out_free2; | |
1645 | } | |
1646 | ||
2ffd8679 | 1647 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
1648 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
1649 | if (err) { | |
1650 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 HD |
1651 | kthread_stop(ksm_thread); |
1652 | goto out_free2; | |
31dbd01f | 1653 | } |
c73602ad HD |
1654 | #else |
1655 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
1656 | ||
2ffd8679 | 1657 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1658 | |
1659 | return 0; | |
1660 | ||
31dbd01f IE |
1661 | out_free2: |
1662 | mm_slots_hash_free(); | |
1663 | out_free1: | |
1664 | ksm_slab_free(); | |
1665 | out: | |
1666 | return err; | |
f8af4da3 | 1667 | } |
31dbd01f | 1668 | module_init(ksm_init) |