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> | |
4e5f01c2 | 31 | #include <linux/memcontrol.h> |
31dbd01f | 32 | #include <linux/rbtree.h> |
62b61f61 | 33 | #include <linux/memory.h> |
31dbd01f | 34 | #include <linux/mmu_notifier.h> |
2c6854fd | 35 | #include <linux/swap.h> |
f8af4da3 | 36 | #include <linux/ksm.h> |
d9f8984c | 37 | #include <linux/hash.h> |
878aee7d | 38 | #include <linux/freezer.h> |
72788c38 | 39 | #include <linux/oom.h> |
f8af4da3 | 40 | |
31dbd01f | 41 | #include <asm/tlbflush.h> |
73848b46 | 42 | #include "internal.h" |
31dbd01f IE |
43 | |
44 | /* | |
45 | * A few notes about the KSM scanning process, | |
46 | * to make it easier to understand the data structures below: | |
47 | * | |
48 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
49 | * contents into a data structure that holds pointers to the pages' locations. | |
50 | * | |
51 | * Since the contents of the pages may change at any moment, KSM cannot just | |
52 | * insert the pages into a normal sorted tree and expect it to find anything. | |
53 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
54 | * | |
55 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
56 | * by their contents. Because each such page is write-protected, searching on | |
57 | * this tree is fully assured to be working (except when pages are unmapped), | |
58 | * and therefore this tree is called the stable tree. | |
59 | * | |
60 | * In addition to the stable tree, KSM uses a second data structure called the | |
61 | * unstable tree: this tree holds pointers to pages which have been found to | |
62 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
63 | * by their contents, but since they are not write-protected, KSM cannot rely | |
64 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
65 | * be corrupted as its contents are modified, and so it is called unstable. | |
66 | * | |
67 | * KSM solves this problem by several techniques: | |
68 | * | |
69 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
70 | * memory areas, and then the tree is rebuilt again from the beginning. | |
71 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
72 | * has not changed since the previous scan of all memory areas. | |
73 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
74 | * colors of the nodes and not on their contents, assuring that even when | |
75 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
76 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
77 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
78 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
79 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
80 | * it is secured in the stable tree. (When we scan a new page, we first | |
81 | * compare it against the stable tree, and then against the unstable tree.) | |
82 | */ | |
83 | ||
84 | /** | |
85 | * struct mm_slot - ksm information per mm that is being scanned | |
86 | * @link: link to the mm_slots hash list | |
87 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 88 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
89 | * @mm: the mm that this information is valid for |
90 | */ | |
91 | struct mm_slot { | |
92 | struct hlist_node link; | |
93 | struct list_head mm_list; | |
6514d511 | 94 | struct rmap_item *rmap_list; |
31dbd01f IE |
95 | struct mm_struct *mm; |
96 | }; | |
97 | ||
98 | /** | |
99 | * struct ksm_scan - cursor for scanning | |
100 | * @mm_slot: the current mm_slot we are scanning | |
101 | * @address: the next address inside that to be scanned | |
6514d511 | 102 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
103 | * @seqnr: count of completed full scans (needed when removing unstable node) |
104 | * | |
105 | * There is only the one ksm_scan instance of this cursor structure. | |
106 | */ | |
107 | struct ksm_scan { | |
108 | struct mm_slot *mm_slot; | |
109 | unsigned long address; | |
6514d511 | 110 | struct rmap_item **rmap_list; |
31dbd01f IE |
111 | unsigned long seqnr; |
112 | }; | |
113 | ||
7b6ba2c7 HD |
114 | /** |
115 | * struct stable_node - node of the stable rbtree | |
116 | * @node: rb node of this ksm page in the stable tree | |
117 | * @hlist: hlist head of rmap_items using this ksm page | |
62b61f61 | 118 | * @kpfn: page frame number of this ksm page |
7b6ba2c7 HD |
119 | */ |
120 | struct stable_node { | |
121 | struct rb_node node; | |
122 | struct hlist_head hlist; | |
62b61f61 | 123 | unsigned long kpfn; |
7b6ba2c7 HD |
124 | }; |
125 | ||
31dbd01f IE |
126 | /** |
127 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 | 128 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
db114b83 | 129 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
31dbd01f IE |
130 | * @mm: the memory structure this rmap_item is pointing into |
131 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
132 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
133 | * @node: rb node of this rmap_item in the unstable tree |
134 | * @head: pointer to stable_node heading this list in the stable tree | |
135 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
136 | */ |
137 | struct rmap_item { | |
6514d511 | 138 | struct rmap_item *rmap_list; |
db114b83 | 139 | struct anon_vma *anon_vma; /* when stable */ |
31dbd01f IE |
140 | struct mm_struct *mm; |
141 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 142 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 143 | union { |
7b6ba2c7 HD |
144 | struct rb_node node; /* when node of unstable tree */ |
145 | struct { /* when listed from stable tree */ | |
146 | struct stable_node *head; | |
147 | struct hlist_node hlist; | |
148 | }; | |
31dbd01f IE |
149 | }; |
150 | }; | |
151 | ||
152 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
153 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
154 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
155 | |
156 | /* The stable and unstable tree heads */ | |
157 | static struct rb_root root_stable_tree = RB_ROOT; | |
158 | static struct rb_root root_unstable_tree = RB_ROOT; | |
159 | ||
d9f8984c LJ |
160 | #define MM_SLOTS_HASH_SHIFT 10 |
161 | #define MM_SLOTS_HASH_HEADS (1 << MM_SLOTS_HASH_SHIFT) | |
162 | static struct hlist_head mm_slots_hash[MM_SLOTS_HASH_HEADS]; | |
31dbd01f IE |
163 | |
164 | static struct mm_slot ksm_mm_head = { | |
165 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
166 | }; | |
167 | static struct ksm_scan ksm_scan = { | |
168 | .mm_slot = &ksm_mm_head, | |
169 | }; | |
170 | ||
171 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 172 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
173 | static struct kmem_cache *mm_slot_cache; |
174 | ||
175 | /* The number of nodes in the stable tree */ | |
b4028260 | 176 | static unsigned long ksm_pages_shared; |
31dbd01f | 177 | |
e178dfde | 178 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 179 | static unsigned long ksm_pages_sharing; |
31dbd01f | 180 | |
473b0ce4 HD |
181 | /* The number of nodes in the unstable tree */ |
182 | static unsigned long ksm_pages_unshared; | |
183 | ||
184 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
185 | static unsigned long ksm_rmap_items; | |
186 | ||
31dbd01f | 187 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 188 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
189 | |
190 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 191 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
192 | |
193 | #define KSM_RUN_STOP 0 | |
194 | #define KSM_RUN_MERGE 1 | |
195 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 196 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
197 | |
198 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
199 | static DEFINE_MUTEX(ksm_thread_mutex); | |
200 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
201 | ||
202 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
203 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
204 | (__flags), NULL) | |
205 | ||
206 | static int __init ksm_slab_init(void) | |
207 | { | |
208 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
209 | if (!rmap_item_cache) | |
210 | goto out; | |
211 | ||
7b6ba2c7 HD |
212 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
213 | if (!stable_node_cache) | |
214 | goto out_free1; | |
215 | ||
31dbd01f IE |
216 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
217 | if (!mm_slot_cache) | |
7b6ba2c7 | 218 | goto out_free2; |
31dbd01f IE |
219 | |
220 | return 0; | |
221 | ||
7b6ba2c7 HD |
222 | out_free2: |
223 | kmem_cache_destroy(stable_node_cache); | |
224 | out_free1: | |
31dbd01f IE |
225 | kmem_cache_destroy(rmap_item_cache); |
226 | out: | |
227 | return -ENOMEM; | |
228 | } | |
229 | ||
230 | static void __init ksm_slab_free(void) | |
231 | { | |
232 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 233 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
234 | kmem_cache_destroy(rmap_item_cache); |
235 | mm_slot_cache = NULL; | |
236 | } | |
237 | ||
238 | static inline struct rmap_item *alloc_rmap_item(void) | |
239 | { | |
473b0ce4 HD |
240 | struct rmap_item *rmap_item; |
241 | ||
242 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
243 | if (rmap_item) | |
244 | ksm_rmap_items++; | |
245 | return rmap_item; | |
31dbd01f IE |
246 | } |
247 | ||
248 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
249 | { | |
473b0ce4 | 250 | ksm_rmap_items--; |
31dbd01f IE |
251 | rmap_item->mm = NULL; /* debug safety */ |
252 | kmem_cache_free(rmap_item_cache, rmap_item); | |
253 | } | |
254 | ||
7b6ba2c7 HD |
255 | static inline struct stable_node *alloc_stable_node(void) |
256 | { | |
257 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
258 | } | |
259 | ||
260 | static inline void free_stable_node(struct stable_node *stable_node) | |
261 | { | |
262 | kmem_cache_free(stable_node_cache, stable_node); | |
263 | } | |
264 | ||
31dbd01f IE |
265 | static inline struct mm_slot *alloc_mm_slot(void) |
266 | { | |
267 | if (!mm_slot_cache) /* initialization failed */ | |
268 | return NULL; | |
269 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
270 | } | |
271 | ||
272 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
273 | { | |
274 | kmem_cache_free(mm_slot_cache, mm_slot); | |
275 | } | |
276 | ||
31dbd01f IE |
277 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
278 | { | |
279 | struct mm_slot *mm_slot; | |
280 | struct hlist_head *bucket; | |
281 | struct hlist_node *node; | |
282 | ||
d9f8984c | 283 | bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)]; |
31dbd01f IE |
284 | hlist_for_each_entry(mm_slot, node, bucket, link) { |
285 | if (mm == mm_slot->mm) | |
286 | return mm_slot; | |
287 | } | |
288 | return NULL; | |
289 | } | |
290 | ||
291 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
292 | struct mm_slot *mm_slot) | |
293 | { | |
294 | struct hlist_head *bucket; | |
295 | ||
d9f8984c | 296 | bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)]; |
31dbd01f | 297 | mm_slot->mm = mm; |
31dbd01f IE |
298 | hlist_add_head(&mm_slot->link, bucket); |
299 | } | |
300 | ||
301 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
302 | { | |
303 | return rmap_item->address & STABLE_FLAG; | |
304 | } | |
305 | ||
a913e182 HD |
306 | /* |
307 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
308 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
309 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
310 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
311 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
312 | * places for correctness, in some places just to avoid unnecessary work. | |
313 | */ | |
314 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
315 | { | |
316 | return atomic_read(&mm->mm_users) == 0; | |
317 | } | |
318 | ||
31dbd01f IE |
319 | /* |
320 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
321 | * | |
322 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
323 | * put_page(page); | |
324 | * | |
325 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
326 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
327 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
328 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
329 | */ | |
d952b791 | 330 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
331 | { |
332 | struct page *page; | |
d952b791 | 333 | int ret = 0; |
31dbd01f IE |
334 | |
335 | do { | |
336 | cond_resched(); | |
337 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 338 | if (IS_ERR_OR_NULL(page)) |
31dbd01f IE |
339 | break; |
340 | if (PageKsm(page)) | |
341 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
342 | FAULT_FLAG_WRITE); | |
343 | else | |
344 | ret = VM_FAULT_WRITE; | |
345 | put_page(page); | |
d952b791 HD |
346 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
347 | /* | |
348 | * We must loop because handle_mm_fault() may back out if there's | |
349 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
350 | * | |
351 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
352 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
353 | * but note that a concurrent fault might break PageKsm for us. | |
354 | * | |
355 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
356 | * backing file, which also invalidates anonymous pages: that's | |
357 | * okay, that truncation will have unmapped the PageKsm for us. | |
358 | * | |
359 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
360 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
361 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
362 | * to user; and ksmd, having no mm, would never be chosen for that. | |
363 | * | |
364 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
365 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
366 | * even ksmd can fail in this way - though it's usually breaking ksm | |
367 | * just to undo a merge it made a moment before, so unlikely to oom. | |
368 | * | |
369 | * That's a pity: we might therefore have more kernel pages allocated | |
370 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
371 | * will retry to break_cow on each pass, so should recover the page | |
372 | * in due course. The important thing is to not let VM_MERGEABLE | |
373 | * be cleared while any such pages might remain in the area. | |
374 | */ | |
375 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
376 | } |
377 | ||
8dd3557a | 378 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 379 | { |
8dd3557a HD |
380 | struct mm_struct *mm = rmap_item->mm; |
381 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
382 | struct vm_area_struct *vma; |
383 | ||
4035c07a HD |
384 | /* |
385 | * It is not an accident that whenever we want to break COW | |
386 | * to undo, we also need to drop a reference to the anon_vma. | |
387 | */ | |
9e60109f | 388 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 389 | |
81464e30 | 390 | down_read(&mm->mmap_sem); |
9ba69294 HD |
391 | if (ksm_test_exit(mm)) |
392 | goto out; | |
31dbd01f IE |
393 | vma = find_vma(mm, addr); |
394 | if (!vma || vma->vm_start > addr) | |
81464e30 | 395 | goto out; |
31dbd01f | 396 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 397 | goto out; |
31dbd01f | 398 | break_ksm(vma, addr); |
81464e30 | 399 | out: |
31dbd01f IE |
400 | up_read(&mm->mmap_sem); |
401 | } | |
402 | ||
29ad768c AA |
403 | static struct page *page_trans_compound_anon(struct page *page) |
404 | { | |
405 | if (PageTransCompound(page)) { | |
22e5c47e | 406 | struct page *head = compound_trans_head(page); |
29ad768c | 407 | /* |
22e5c47e AA |
408 | * head may actually be splitted and freed from under |
409 | * us but it's ok here. | |
29ad768c | 410 | */ |
29ad768c AA |
411 | if (PageAnon(head)) |
412 | return head; | |
413 | } | |
414 | return NULL; | |
415 | } | |
416 | ||
31dbd01f IE |
417 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) |
418 | { | |
419 | struct mm_struct *mm = rmap_item->mm; | |
420 | unsigned long addr = rmap_item->address; | |
421 | struct vm_area_struct *vma; | |
422 | struct page *page; | |
423 | ||
424 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
425 | if (ksm_test_exit(mm)) |
426 | goto out; | |
31dbd01f IE |
427 | vma = find_vma(mm, addr); |
428 | if (!vma || vma->vm_start > addr) | |
429 | goto out; | |
430 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
431 | goto out; | |
432 | ||
433 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 434 | if (IS_ERR_OR_NULL(page)) |
31dbd01f | 435 | goto out; |
29ad768c | 436 | if (PageAnon(page) || page_trans_compound_anon(page)) { |
31dbd01f IE |
437 | flush_anon_page(vma, page, addr); |
438 | flush_dcache_page(page); | |
439 | } else { | |
440 | put_page(page); | |
441 | out: page = NULL; | |
442 | } | |
443 | up_read(&mm->mmap_sem); | |
444 | return page; | |
445 | } | |
446 | ||
4035c07a HD |
447 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
448 | { | |
449 | struct rmap_item *rmap_item; | |
450 | struct hlist_node *hlist; | |
451 | ||
452 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { | |
453 | if (rmap_item->hlist.next) | |
454 | ksm_pages_sharing--; | |
455 | else | |
456 | ksm_pages_shared--; | |
9e60109f | 457 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
458 | rmap_item->address &= PAGE_MASK; |
459 | cond_resched(); | |
460 | } | |
461 | ||
462 | rb_erase(&stable_node->node, &root_stable_tree); | |
463 | free_stable_node(stable_node); | |
464 | } | |
465 | ||
466 | /* | |
467 | * get_ksm_page: checks if the page indicated by the stable node | |
468 | * is still its ksm page, despite having held no reference to it. | |
469 | * In which case we can trust the content of the page, and it | |
470 | * returns the gotten page; but if the page has now been zapped, | |
471 | * remove the stale node from the stable tree and return NULL. | |
472 | * | |
473 | * You would expect the stable_node to hold a reference to the ksm page. | |
474 | * But if it increments the page's count, swapping out has to wait for | |
475 | * ksmd to come around again before it can free the page, which may take | |
476 | * seconds or even minutes: much too unresponsive. So instead we use a | |
477 | * "keyhole reference": access to the ksm page from the stable node peeps | |
478 | * out through its keyhole to see if that page still holds the right key, | |
479 | * pointing back to this stable node. This relies on freeing a PageAnon | |
480 | * page to reset its page->mapping to NULL, and relies on no other use of | |
481 | * a page to put something that might look like our key in page->mapping. | |
482 | * | |
483 | * include/linux/pagemap.h page_cache_get_speculative() is a good reference, | |
484 | * but this is different - made simpler by ksm_thread_mutex being held, but | |
485 | * interesting for assuming that no other use of the struct page could ever | |
486 | * put our expected_mapping into page->mapping (or a field of the union which | |
487 | * coincides with page->mapping). The RCU calls are not for KSM at all, but | |
488 | * to keep the page_count protocol described with page_cache_get_speculative. | |
489 | * | |
490 | * Note: it is possible that get_ksm_page() will return NULL one moment, | |
491 | * then page the next, if the page is in between page_freeze_refs() and | |
492 | * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page | |
493 | * is on its way to being freed; but it is an anomaly to bear in mind. | |
494 | */ | |
495 | static struct page *get_ksm_page(struct stable_node *stable_node) | |
496 | { | |
497 | struct page *page; | |
498 | void *expected_mapping; | |
499 | ||
62b61f61 | 500 | page = pfn_to_page(stable_node->kpfn); |
4035c07a HD |
501 | expected_mapping = (void *)stable_node + |
502 | (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); | |
503 | rcu_read_lock(); | |
504 | if (page->mapping != expected_mapping) | |
505 | goto stale; | |
506 | if (!get_page_unless_zero(page)) | |
507 | goto stale; | |
508 | if (page->mapping != expected_mapping) { | |
509 | put_page(page); | |
510 | goto stale; | |
511 | } | |
512 | rcu_read_unlock(); | |
513 | return page; | |
514 | stale: | |
515 | rcu_read_unlock(); | |
516 | remove_node_from_stable_tree(stable_node); | |
517 | return NULL; | |
518 | } | |
519 | ||
31dbd01f IE |
520 | /* |
521 | * Removing rmap_item from stable or unstable tree. | |
522 | * This function will clean the information from the stable/unstable tree. | |
523 | */ | |
524 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
525 | { | |
7b6ba2c7 HD |
526 | if (rmap_item->address & STABLE_FLAG) { |
527 | struct stable_node *stable_node; | |
5ad64688 | 528 | struct page *page; |
31dbd01f | 529 | |
7b6ba2c7 | 530 | stable_node = rmap_item->head; |
4035c07a HD |
531 | page = get_ksm_page(stable_node); |
532 | if (!page) | |
533 | goto out; | |
5ad64688 | 534 | |
4035c07a | 535 | lock_page(page); |
7b6ba2c7 | 536 | hlist_del(&rmap_item->hlist); |
4035c07a HD |
537 | unlock_page(page); |
538 | put_page(page); | |
08beca44 | 539 | |
4035c07a HD |
540 | if (stable_node->hlist.first) |
541 | ksm_pages_sharing--; | |
542 | else | |
7b6ba2c7 | 543 | ksm_pages_shared--; |
31dbd01f | 544 | |
9e60109f | 545 | put_anon_vma(rmap_item->anon_vma); |
93d17715 | 546 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 547 | |
7b6ba2c7 | 548 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
549 | unsigned char age; |
550 | /* | |
9ba69294 | 551 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 552 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
553 | * But be careful when an mm is exiting: do the rb_erase |
554 | * if this rmap_item was inserted by this scan, rather | |
555 | * than left over from before. | |
31dbd01f IE |
556 | */ |
557 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 558 | BUG_ON(age > 1); |
31dbd01f IE |
559 | if (!age) |
560 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
93d17715 | 561 | |
473b0ce4 | 562 | ksm_pages_unshared--; |
93d17715 | 563 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 564 | } |
4035c07a | 565 | out: |
31dbd01f IE |
566 | cond_resched(); /* we're called from many long loops */ |
567 | } | |
568 | ||
31dbd01f | 569 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 570 | struct rmap_item **rmap_list) |
31dbd01f | 571 | { |
6514d511 HD |
572 | while (*rmap_list) { |
573 | struct rmap_item *rmap_item = *rmap_list; | |
574 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 575 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
576 | free_rmap_item(rmap_item); |
577 | } | |
578 | } | |
579 | ||
580 | /* | |
581 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather | |
582 | * than check every pte of a given vma, the locking doesn't quite work for | |
583 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
584 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
585 | * rmap_items from parent to child at fork time (so as not to waste time | |
586 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
587 | * |
588 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
589 | * and freeing memory) when unmerging an area, it's easier to leave that | |
590 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
591 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 592 | */ |
d952b791 HD |
593 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
594 | unsigned long start, unsigned long end) | |
31dbd01f IE |
595 | { |
596 | unsigned long addr; | |
d952b791 | 597 | int err = 0; |
31dbd01f | 598 | |
d952b791 | 599 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
600 | if (ksm_test_exit(vma->vm_mm)) |
601 | break; | |
d952b791 HD |
602 | if (signal_pending(current)) |
603 | err = -ERESTARTSYS; | |
604 | else | |
605 | err = break_ksm(vma, addr); | |
606 | } | |
607 | return err; | |
31dbd01f IE |
608 | } |
609 | ||
2ffd8679 HD |
610 | #ifdef CONFIG_SYSFS |
611 | /* | |
612 | * Only called through the sysfs control interface: | |
613 | */ | |
d952b791 | 614 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
615 | { |
616 | struct mm_slot *mm_slot; | |
617 | struct mm_struct *mm; | |
618 | struct vm_area_struct *vma; | |
d952b791 HD |
619 | int err = 0; |
620 | ||
621 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 622 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
623 | struct mm_slot, mm_list); |
624 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 625 | |
9ba69294 HD |
626 | for (mm_slot = ksm_scan.mm_slot; |
627 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
628 | mm = mm_slot->mm; |
629 | down_read(&mm->mmap_sem); | |
630 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
631 | if (ksm_test_exit(mm)) |
632 | break; | |
31dbd01f IE |
633 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
634 | continue; | |
d952b791 HD |
635 | err = unmerge_ksm_pages(vma, |
636 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
637 | if (err) |
638 | goto error; | |
31dbd01f | 639 | } |
9ba69294 | 640 | |
6514d511 | 641 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
642 | |
643 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 644 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 645 | struct mm_slot, mm_list); |
9ba69294 HD |
646 | if (ksm_test_exit(mm)) { |
647 | hlist_del(&mm_slot->link); | |
648 | list_del(&mm_slot->mm_list); | |
649 | spin_unlock(&ksm_mmlist_lock); | |
650 | ||
651 | free_mm_slot(mm_slot); | |
652 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
653 | up_read(&mm->mmap_sem); | |
654 | mmdrop(mm); | |
655 | } else { | |
656 | spin_unlock(&ksm_mmlist_lock); | |
657 | up_read(&mm->mmap_sem); | |
658 | } | |
31dbd01f IE |
659 | } |
660 | ||
d952b791 | 661 | ksm_scan.seqnr = 0; |
9ba69294 HD |
662 | return 0; |
663 | ||
664 | error: | |
665 | up_read(&mm->mmap_sem); | |
31dbd01f | 666 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 667 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 668 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 669 | return err; |
31dbd01f | 670 | } |
2ffd8679 | 671 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 672 | |
31dbd01f IE |
673 | static u32 calc_checksum(struct page *page) |
674 | { | |
675 | u32 checksum; | |
676 | void *addr = kmap_atomic(page, KM_USER0); | |
677 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); | |
678 | kunmap_atomic(addr, KM_USER0); | |
679 | return checksum; | |
680 | } | |
681 | ||
682 | static int memcmp_pages(struct page *page1, struct page *page2) | |
683 | { | |
684 | char *addr1, *addr2; | |
685 | int ret; | |
686 | ||
687 | addr1 = kmap_atomic(page1, KM_USER0); | |
688 | addr2 = kmap_atomic(page2, KM_USER1); | |
689 | ret = memcmp(addr1, addr2, PAGE_SIZE); | |
690 | kunmap_atomic(addr2, KM_USER1); | |
691 | kunmap_atomic(addr1, KM_USER0); | |
692 | return ret; | |
693 | } | |
694 | ||
695 | static inline int pages_identical(struct page *page1, struct page *page2) | |
696 | { | |
697 | return !memcmp_pages(page1, page2); | |
698 | } | |
699 | ||
700 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
701 | pte_t *orig_pte) | |
702 | { | |
703 | struct mm_struct *mm = vma->vm_mm; | |
704 | unsigned long addr; | |
705 | pte_t *ptep; | |
706 | spinlock_t *ptl; | |
707 | int swapped; | |
708 | int err = -EFAULT; | |
709 | ||
710 | addr = page_address_in_vma(page, vma); | |
711 | if (addr == -EFAULT) | |
712 | goto out; | |
713 | ||
29ad768c | 714 | BUG_ON(PageTransCompound(page)); |
31dbd01f IE |
715 | ptep = page_check_address(page, mm, addr, &ptl, 0); |
716 | if (!ptep) | |
717 | goto out; | |
718 | ||
4e31635c | 719 | if (pte_write(*ptep) || pte_dirty(*ptep)) { |
31dbd01f IE |
720 | pte_t entry; |
721 | ||
722 | swapped = PageSwapCache(page); | |
723 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
724 | /* | |
25985edc | 725 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f IE |
726 | * take any lock, therefore the check that we are going to make |
727 | * with the pagecount against the mapcount is racey and | |
728 | * O_DIRECT can happen right after the check. | |
729 | * So we clear the pte and flush the tlb before the check | |
730 | * this assure us that no O_DIRECT can happen after the check | |
731 | * or in the middle of the check. | |
732 | */ | |
733 | entry = ptep_clear_flush(vma, addr, ptep); | |
734 | /* | |
735 | * Check that no O_DIRECT or similar I/O is in progress on the | |
736 | * page | |
737 | */ | |
31e855ea | 738 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
cb532375 | 739 | set_pte_at(mm, addr, ptep, entry); |
31dbd01f IE |
740 | goto out_unlock; |
741 | } | |
4e31635c HD |
742 | if (pte_dirty(entry)) |
743 | set_page_dirty(page); | |
744 | entry = pte_mkclean(pte_wrprotect(entry)); | |
31dbd01f IE |
745 | set_pte_at_notify(mm, addr, ptep, entry); |
746 | } | |
747 | *orig_pte = *ptep; | |
748 | err = 0; | |
749 | ||
750 | out_unlock: | |
751 | pte_unmap_unlock(ptep, ptl); | |
752 | out: | |
753 | return err; | |
754 | } | |
755 | ||
756 | /** | |
757 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
758 | * @vma: vma that holds the pte pointing to page |
759 | * @page: the page we are replacing by kpage | |
760 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
761 | * @orig_pte: the original value of the pte |
762 | * | |
763 | * Returns 0 on success, -EFAULT on failure. | |
764 | */ | |
8dd3557a HD |
765 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
766 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
767 | { |
768 | struct mm_struct *mm = vma->vm_mm; | |
769 | pgd_t *pgd; | |
770 | pud_t *pud; | |
771 | pmd_t *pmd; | |
772 | pte_t *ptep; | |
773 | spinlock_t *ptl; | |
774 | unsigned long addr; | |
31dbd01f IE |
775 | int err = -EFAULT; |
776 | ||
8dd3557a | 777 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
778 | if (addr == -EFAULT) |
779 | goto out; | |
780 | ||
781 | pgd = pgd_offset(mm, addr); | |
782 | if (!pgd_present(*pgd)) | |
783 | goto out; | |
784 | ||
785 | pud = pud_offset(pgd, addr); | |
786 | if (!pud_present(*pud)) | |
787 | goto out; | |
788 | ||
789 | pmd = pmd_offset(pud, addr); | |
29ad768c | 790 | BUG_ON(pmd_trans_huge(*pmd)); |
31dbd01f IE |
791 | if (!pmd_present(*pmd)) |
792 | goto out; | |
793 | ||
794 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
795 | if (!pte_same(*ptep, orig_pte)) { | |
796 | pte_unmap_unlock(ptep, ptl); | |
797 | goto out; | |
798 | } | |
799 | ||
8dd3557a | 800 | get_page(kpage); |
5ad64688 | 801 | page_add_anon_rmap(kpage, vma, addr); |
31dbd01f IE |
802 | |
803 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
804 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 805 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 806 | |
8dd3557a | 807 | page_remove_rmap(page); |
ae52a2ad HD |
808 | if (!page_mapped(page)) |
809 | try_to_free_swap(page); | |
8dd3557a | 810 | put_page(page); |
31dbd01f IE |
811 | |
812 | pte_unmap_unlock(ptep, ptl); | |
813 | err = 0; | |
814 | out: | |
815 | return err; | |
816 | } | |
817 | ||
29ad768c AA |
818 | static int page_trans_compound_anon_split(struct page *page) |
819 | { | |
820 | int ret = 0; | |
821 | struct page *transhuge_head = page_trans_compound_anon(page); | |
822 | if (transhuge_head) { | |
823 | /* Get the reference on the head to split it. */ | |
824 | if (get_page_unless_zero(transhuge_head)) { | |
825 | /* | |
826 | * Recheck we got the reference while the head | |
827 | * was still anonymous. | |
828 | */ | |
829 | if (PageAnon(transhuge_head)) | |
830 | ret = split_huge_page(transhuge_head); | |
831 | else | |
832 | /* | |
833 | * Retry later if split_huge_page run | |
834 | * from under us. | |
835 | */ | |
836 | ret = 1; | |
837 | put_page(transhuge_head); | |
838 | } else | |
839 | /* Retry later if split_huge_page run from under us. */ | |
840 | ret = 1; | |
841 | } | |
842 | return ret; | |
843 | } | |
844 | ||
31dbd01f IE |
845 | /* |
846 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
847 | * @vma: the vma that holds the pte pointing to page |
848 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
849 | * @kpage: the PageKsm page that we want to map instead of page, |
850 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
851 | * |
852 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
853 | */ | |
854 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 855 | struct page *page, struct page *kpage) |
31dbd01f IE |
856 | { |
857 | pte_t orig_pte = __pte(0); | |
858 | int err = -EFAULT; | |
859 | ||
db114b83 HD |
860 | if (page == kpage) /* ksm page forked */ |
861 | return 0; | |
862 | ||
31dbd01f IE |
863 | if (!(vma->vm_flags & VM_MERGEABLE)) |
864 | goto out; | |
29ad768c AA |
865 | if (PageTransCompound(page) && page_trans_compound_anon_split(page)) |
866 | goto out; | |
867 | BUG_ON(PageTransCompound(page)); | |
8dd3557a | 868 | if (!PageAnon(page)) |
31dbd01f IE |
869 | goto out; |
870 | ||
31dbd01f IE |
871 | /* |
872 | * We need the page lock to read a stable PageSwapCache in | |
873 | * write_protect_page(). We use trylock_page() instead of | |
874 | * lock_page() because we don't want to wait here - we | |
875 | * prefer to continue scanning and merging different pages, | |
876 | * then come back to this page when it is unlocked. | |
877 | */ | |
8dd3557a | 878 | if (!trylock_page(page)) |
31e855ea | 879 | goto out; |
31dbd01f IE |
880 | /* |
881 | * If this anonymous page is mapped only here, its pte may need | |
882 | * to be write-protected. If it's mapped elsewhere, all of its | |
883 | * ptes are necessarily already write-protected. But in either | |
884 | * case, we need to lock and check page_count is not raised. | |
885 | */ | |
80e14822 HD |
886 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
887 | if (!kpage) { | |
888 | /* | |
889 | * While we hold page lock, upgrade page from | |
890 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
891 | * stable_tree_insert() will update stable_node. | |
892 | */ | |
893 | set_page_stable_node(page, NULL); | |
894 | mark_page_accessed(page); | |
895 | err = 0; | |
896 | } else if (pages_identical(page, kpage)) | |
897 | err = replace_page(vma, page, kpage, orig_pte); | |
898 | } | |
31dbd01f | 899 | |
80e14822 | 900 | if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { |
73848b46 | 901 | munlock_vma_page(page); |
5ad64688 HD |
902 | if (!PageMlocked(kpage)) { |
903 | unlock_page(page); | |
5ad64688 HD |
904 | lock_page(kpage); |
905 | mlock_vma_page(kpage); | |
906 | page = kpage; /* for final unlock */ | |
907 | } | |
908 | } | |
73848b46 | 909 | |
8dd3557a | 910 | unlock_page(page); |
31dbd01f IE |
911 | out: |
912 | return err; | |
913 | } | |
914 | ||
81464e30 HD |
915 | /* |
916 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
917 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
918 | * |
919 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 920 | */ |
8dd3557a HD |
921 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
922 | struct page *page, struct page *kpage) | |
81464e30 | 923 | { |
8dd3557a | 924 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
925 | struct vm_area_struct *vma; |
926 | int err = -EFAULT; | |
927 | ||
8dd3557a HD |
928 | down_read(&mm->mmap_sem); |
929 | if (ksm_test_exit(mm)) | |
9ba69294 | 930 | goto out; |
8dd3557a HD |
931 | vma = find_vma(mm, rmap_item->address); |
932 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
933 | goto out; |
934 | ||
8dd3557a | 935 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
936 | if (err) |
937 | goto out; | |
938 | ||
939 | /* Must get reference to anon_vma while still holding mmap_sem */ | |
9e60109f PZ |
940 | rmap_item->anon_vma = vma->anon_vma; |
941 | get_anon_vma(vma->anon_vma); | |
81464e30 | 942 | out: |
8dd3557a | 943 | up_read(&mm->mmap_sem); |
81464e30 HD |
944 | return err; |
945 | } | |
946 | ||
31dbd01f IE |
947 | /* |
948 | * try_to_merge_two_pages - take two identical pages and prepare them | |
949 | * to be merged into one page. | |
950 | * | |
8dd3557a HD |
951 | * This function returns the kpage if we successfully merged two identical |
952 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 953 | * |
80e14822 | 954 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
955 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
956 | */ | |
8dd3557a HD |
957 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
958 | struct page *page, | |
959 | struct rmap_item *tree_rmap_item, | |
960 | struct page *tree_page) | |
31dbd01f | 961 | { |
80e14822 | 962 | int err; |
31dbd01f | 963 | |
80e14822 | 964 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 965 | if (!err) { |
8dd3557a | 966 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 967 | tree_page, page); |
31dbd01f | 968 | /* |
81464e30 HD |
969 | * If that fails, we have a ksm page with only one pte |
970 | * pointing to it: so break it. | |
31dbd01f | 971 | */ |
4035c07a | 972 | if (err) |
8dd3557a | 973 | break_cow(rmap_item); |
31dbd01f | 974 | } |
80e14822 | 975 | return err ? NULL : page; |
31dbd01f IE |
976 | } |
977 | ||
31dbd01f | 978 | /* |
8dd3557a | 979 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
980 | * |
981 | * This function checks if there is a page inside the stable tree | |
982 | * with identical content to the page that we are scanning right now. | |
983 | * | |
7b6ba2c7 | 984 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
985 | * NULL otherwise. |
986 | */ | |
62b61f61 | 987 | static struct page *stable_tree_search(struct page *page) |
31dbd01f IE |
988 | { |
989 | struct rb_node *node = root_stable_tree.rb_node; | |
7b6ba2c7 | 990 | struct stable_node *stable_node; |
31dbd01f | 991 | |
08beca44 HD |
992 | stable_node = page_stable_node(page); |
993 | if (stable_node) { /* ksm page forked */ | |
994 | get_page(page); | |
62b61f61 | 995 | return page; |
08beca44 HD |
996 | } |
997 | ||
31dbd01f | 998 | while (node) { |
4035c07a | 999 | struct page *tree_page; |
31dbd01f IE |
1000 | int ret; |
1001 | ||
08beca44 | 1002 | cond_resched(); |
7b6ba2c7 | 1003 | stable_node = rb_entry(node, struct stable_node, node); |
4035c07a HD |
1004 | tree_page = get_ksm_page(stable_node); |
1005 | if (!tree_page) | |
1006 | return NULL; | |
31dbd01f | 1007 | |
4035c07a | 1008 | ret = memcmp_pages(page, tree_page); |
31dbd01f | 1009 | |
4035c07a HD |
1010 | if (ret < 0) { |
1011 | put_page(tree_page); | |
31dbd01f | 1012 | node = node->rb_left; |
4035c07a HD |
1013 | } else if (ret > 0) { |
1014 | put_page(tree_page); | |
31dbd01f | 1015 | node = node->rb_right; |
4035c07a | 1016 | } else |
62b61f61 | 1017 | return tree_page; |
31dbd01f IE |
1018 | } |
1019 | ||
1020 | return NULL; | |
1021 | } | |
1022 | ||
1023 | /* | |
1024 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
1025 | * into the stable tree. | |
1026 | * | |
7b6ba2c7 HD |
1027 | * This function returns the stable tree node just allocated on success, |
1028 | * NULL otherwise. | |
31dbd01f | 1029 | */ |
7b6ba2c7 | 1030 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f IE |
1031 | { |
1032 | struct rb_node **new = &root_stable_tree.rb_node; | |
1033 | struct rb_node *parent = NULL; | |
7b6ba2c7 | 1034 | struct stable_node *stable_node; |
31dbd01f IE |
1035 | |
1036 | while (*new) { | |
4035c07a | 1037 | struct page *tree_page; |
31dbd01f IE |
1038 | int ret; |
1039 | ||
08beca44 | 1040 | cond_resched(); |
7b6ba2c7 | 1041 | stable_node = rb_entry(*new, struct stable_node, node); |
4035c07a HD |
1042 | tree_page = get_ksm_page(stable_node); |
1043 | if (!tree_page) | |
1044 | return NULL; | |
31dbd01f | 1045 | |
4035c07a HD |
1046 | ret = memcmp_pages(kpage, tree_page); |
1047 | put_page(tree_page); | |
31dbd01f IE |
1048 | |
1049 | parent = *new; | |
1050 | if (ret < 0) | |
1051 | new = &parent->rb_left; | |
1052 | else if (ret > 0) | |
1053 | new = &parent->rb_right; | |
1054 | else { | |
1055 | /* | |
1056 | * It is not a bug that stable_tree_search() didn't | |
1057 | * find this node: because at that time our page was | |
1058 | * not yet write-protected, so may have changed since. | |
1059 | */ | |
1060 | return NULL; | |
1061 | } | |
1062 | } | |
1063 | ||
7b6ba2c7 HD |
1064 | stable_node = alloc_stable_node(); |
1065 | if (!stable_node) | |
1066 | return NULL; | |
31dbd01f | 1067 | |
7b6ba2c7 HD |
1068 | rb_link_node(&stable_node->node, parent, new); |
1069 | rb_insert_color(&stable_node->node, &root_stable_tree); | |
1070 | ||
1071 | INIT_HLIST_HEAD(&stable_node->hlist); | |
1072 | ||
62b61f61 | 1073 | stable_node->kpfn = page_to_pfn(kpage); |
08beca44 HD |
1074 | set_page_stable_node(kpage, stable_node); |
1075 | ||
7b6ba2c7 | 1076 | return stable_node; |
31dbd01f IE |
1077 | } |
1078 | ||
1079 | /* | |
8dd3557a HD |
1080 | * unstable_tree_search_insert - search for identical page, |
1081 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1082 | * |
1083 | * This function searches for a page in the unstable tree identical to the | |
1084 | * page currently being scanned; and if no identical page is found in the | |
1085 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1086 | * | |
1087 | * This function returns pointer to rmap_item found to be identical | |
1088 | * to the currently scanned page, NULL otherwise. | |
1089 | * | |
1090 | * This function does both searching and inserting, because they share | |
1091 | * the same walking algorithm in an rbtree. | |
1092 | */ | |
8dd3557a HD |
1093 | static |
1094 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
1095 | struct page *page, | |
1096 | struct page **tree_pagep) | |
1097 | ||
31dbd01f IE |
1098 | { |
1099 | struct rb_node **new = &root_unstable_tree.rb_node; | |
1100 | struct rb_node *parent = NULL; | |
1101 | ||
1102 | while (*new) { | |
1103 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1104 | struct page *tree_page; |
31dbd01f IE |
1105 | int ret; |
1106 | ||
d178f27f | 1107 | cond_resched(); |
31dbd01f | 1108 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a | 1109 | tree_page = get_mergeable_page(tree_rmap_item); |
22eccdd7 | 1110 | if (IS_ERR_OR_NULL(tree_page)) |
31dbd01f IE |
1111 | return NULL; |
1112 | ||
1113 | /* | |
8dd3557a | 1114 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1115 | */ |
8dd3557a HD |
1116 | if (page == tree_page) { |
1117 | put_page(tree_page); | |
31dbd01f IE |
1118 | return NULL; |
1119 | } | |
1120 | ||
8dd3557a | 1121 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1122 | |
1123 | parent = *new; | |
1124 | if (ret < 0) { | |
8dd3557a | 1125 | put_page(tree_page); |
31dbd01f IE |
1126 | new = &parent->rb_left; |
1127 | } else if (ret > 0) { | |
8dd3557a | 1128 | put_page(tree_page); |
31dbd01f IE |
1129 | new = &parent->rb_right; |
1130 | } else { | |
8dd3557a | 1131 | *tree_pagep = tree_page; |
31dbd01f IE |
1132 | return tree_rmap_item; |
1133 | } | |
1134 | } | |
1135 | ||
7b6ba2c7 | 1136 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f IE |
1137 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
1138 | rb_link_node(&rmap_item->node, parent, new); | |
1139 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1140 | ||
473b0ce4 | 1141 | ksm_pages_unshared++; |
31dbd01f IE |
1142 | return NULL; |
1143 | } | |
1144 | ||
1145 | /* | |
1146 | * stable_tree_append - add another rmap_item to the linked list of | |
1147 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1148 | * the same ksm page. | |
1149 | */ | |
1150 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1151 | struct stable_node *stable_node) |
31dbd01f | 1152 | { |
7b6ba2c7 | 1153 | rmap_item->head = stable_node; |
31dbd01f | 1154 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1155 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1156 | |
7b6ba2c7 HD |
1157 | if (rmap_item->hlist.next) |
1158 | ksm_pages_sharing++; | |
1159 | else | |
1160 | ksm_pages_shared++; | |
31dbd01f IE |
1161 | } |
1162 | ||
1163 | /* | |
81464e30 HD |
1164 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1165 | * if not, compare checksum to previous and if it's the same, see if page can | |
1166 | * be inserted into the unstable tree, or merged with a page already there and | |
1167 | * both transferred to the stable tree. | |
31dbd01f IE |
1168 | * |
1169 | * @page: the page that we are searching identical page to. | |
1170 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1171 | */ | |
1172 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1173 | { | |
31dbd01f | 1174 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1175 | struct page *tree_page = NULL; |
7b6ba2c7 | 1176 | struct stable_node *stable_node; |
8dd3557a | 1177 | struct page *kpage; |
31dbd01f IE |
1178 | unsigned int checksum; |
1179 | int err; | |
1180 | ||
93d17715 | 1181 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1182 | |
1183 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 HD |
1184 | kpage = stable_tree_search(page); |
1185 | if (kpage) { | |
08beca44 | 1186 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
1187 | if (!err) { |
1188 | /* | |
1189 | * The page was successfully merged: | |
1190 | * add its rmap_item to the stable tree. | |
1191 | */ | |
5ad64688 | 1192 | lock_page(kpage); |
62b61f61 | 1193 | stable_tree_append(rmap_item, page_stable_node(kpage)); |
5ad64688 | 1194 | unlock_page(kpage); |
31dbd01f | 1195 | } |
8dd3557a | 1196 | put_page(kpage); |
31dbd01f IE |
1197 | return; |
1198 | } | |
1199 | ||
1200 | /* | |
4035c07a HD |
1201 | * If the hash value of the page has changed from the last time |
1202 | * we calculated it, this page is changing frequently: therefore we | |
1203 | * don't want to insert it in the unstable tree, and we don't want | |
1204 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
1205 | */ |
1206 | checksum = calc_checksum(page); | |
1207 | if (rmap_item->oldchecksum != checksum) { | |
1208 | rmap_item->oldchecksum = checksum; | |
1209 | return; | |
1210 | } | |
1211 | ||
8dd3557a HD |
1212 | tree_rmap_item = |
1213 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1214 | if (tree_rmap_item) { |
8dd3557a HD |
1215 | kpage = try_to_merge_two_pages(rmap_item, page, |
1216 | tree_rmap_item, tree_page); | |
1217 | put_page(tree_page); | |
31dbd01f IE |
1218 | /* |
1219 | * As soon as we merge this page, we want to remove the | |
1220 | * rmap_item of the page we have merged with from the unstable | |
1221 | * tree, and insert it instead as new node in the stable tree. | |
1222 | */ | |
8dd3557a | 1223 | if (kpage) { |
93d17715 | 1224 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1225 | |
5ad64688 | 1226 | lock_page(kpage); |
7b6ba2c7 HD |
1227 | stable_node = stable_tree_insert(kpage); |
1228 | if (stable_node) { | |
1229 | stable_tree_append(tree_rmap_item, stable_node); | |
1230 | stable_tree_append(rmap_item, stable_node); | |
1231 | } | |
5ad64688 | 1232 | unlock_page(kpage); |
7b6ba2c7 | 1233 | |
31dbd01f IE |
1234 | /* |
1235 | * If we fail to insert the page into the stable tree, | |
1236 | * we will have 2 virtual addresses that are pointing | |
1237 | * to a ksm page left outside the stable tree, | |
1238 | * in which case we need to break_cow on both. | |
1239 | */ | |
7b6ba2c7 | 1240 | if (!stable_node) { |
8dd3557a HD |
1241 | break_cow(tree_rmap_item); |
1242 | break_cow(rmap_item); | |
31dbd01f IE |
1243 | } |
1244 | } | |
31dbd01f IE |
1245 | } |
1246 | } | |
1247 | ||
1248 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1249 | struct rmap_item **rmap_list, |
31dbd01f IE |
1250 | unsigned long addr) |
1251 | { | |
1252 | struct rmap_item *rmap_item; | |
1253 | ||
6514d511 HD |
1254 | while (*rmap_list) { |
1255 | rmap_item = *rmap_list; | |
93d17715 | 1256 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1257 | return rmap_item; |
31dbd01f IE |
1258 | if (rmap_item->address > addr) |
1259 | break; | |
6514d511 | 1260 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1261 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1262 | free_rmap_item(rmap_item); |
1263 | } | |
1264 | ||
1265 | rmap_item = alloc_rmap_item(); | |
1266 | if (rmap_item) { | |
1267 | /* It has already been zeroed */ | |
1268 | rmap_item->mm = mm_slot->mm; | |
1269 | rmap_item->address = addr; | |
6514d511 HD |
1270 | rmap_item->rmap_list = *rmap_list; |
1271 | *rmap_list = rmap_item; | |
31dbd01f IE |
1272 | } |
1273 | return rmap_item; | |
1274 | } | |
1275 | ||
1276 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1277 | { | |
1278 | struct mm_struct *mm; | |
1279 | struct mm_slot *slot; | |
1280 | struct vm_area_struct *vma; | |
1281 | struct rmap_item *rmap_item; | |
1282 | ||
1283 | if (list_empty(&ksm_mm_head.mm_list)) | |
1284 | return NULL; | |
1285 | ||
1286 | slot = ksm_scan.mm_slot; | |
1287 | if (slot == &ksm_mm_head) { | |
2919bfd0 HD |
1288 | /* |
1289 | * A number of pages can hang around indefinitely on per-cpu | |
1290 | * pagevecs, raised page count preventing write_protect_page | |
1291 | * from merging them. Though it doesn't really matter much, | |
1292 | * it is puzzling to see some stuck in pages_volatile until | |
1293 | * other activity jostles them out, and they also prevented | |
1294 | * LTP's KSM test from succeeding deterministically; so drain | |
1295 | * them here (here rather than on entry to ksm_do_scan(), | |
1296 | * so we don't IPI too often when pages_to_scan is set low). | |
1297 | */ | |
1298 | lru_add_drain_all(); | |
1299 | ||
31dbd01f IE |
1300 | root_unstable_tree = RB_ROOT; |
1301 | ||
1302 | spin_lock(&ksm_mmlist_lock); | |
1303 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1304 | ksm_scan.mm_slot = slot; | |
1305 | spin_unlock(&ksm_mmlist_lock); | |
2b472611 HD |
1306 | /* |
1307 | * Although we tested list_empty() above, a racing __ksm_exit | |
1308 | * of the last mm on the list may have removed it since then. | |
1309 | */ | |
1310 | if (slot == &ksm_mm_head) | |
1311 | return NULL; | |
31dbd01f IE |
1312 | next_mm: |
1313 | ksm_scan.address = 0; | |
6514d511 | 1314 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1315 | } |
1316 | ||
1317 | mm = slot->mm; | |
1318 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1319 | if (ksm_test_exit(mm)) |
1320 | vma = NULL; | |
1321 | else | |
1322 | vma = find_vma(mm, ksm_scan.address); | |
1323 | ||
1324 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1325 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1326 | continue; | |
1327 | if (ksm_scan.address < vma->vm_start) | |
1328 | ksm_scan.address = vma->vm_start; | |
1329 | if (!vma->anon_vma) | |
1330 | ksm_scan.address = vma->vm_end; | |
1331 | ||
1332 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1333 | if (ksm_test_exit(mm)) |
1334 | break; | |
31dbd01f | 1335 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
21ae5b01 AA |
1336 | if (IS_ERR_OR_NULL(*page)) { |
1337 | ksm_scan.address += PAGE_SIZE; | |
1338 | cond_resched(); | |
1339 | continue; | |
1340 | } | |
29ad768c AA |
1341 | if (PageAnon(*page) || |
1342 | page_trans_compound_anon(*page)) { | |
31dbd01f IE |
1343 | flush_anon_page(vma, *page, ksm_scan.address); |
1344 | flush_dcache_page(*page); | |
1345 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1346 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1347 | if (rmap_item) { |
6514d511 HD |
1348 | ksm_scan.rmap_list = |
1349 | &rmap_item->rmap_list; | |
31dbd01f IE |
1350 | ksm_scan.address += PAGE_SIZE; |
1351 | } else | |
1352 | put_page(*page); | |
1353 | up_read(&mm->mmap_sem); | |
1354 | return rmap_item; | |
1355 | } | |
21ae5b01 | 1356 | put_page(*page); |
31dbd01f IE |
1357 | ksm_scan.address += PAGE_SIZE; |
1358 | cond_resched(); | |
1359 | } | |
1360 | } | |
1361 | ||
9ba69294 HD |
1362 | if (ksm_test_exit(mm)) { |
1363 | ksm_scan.address = 0; | |
6514d511 | 1364 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1365 | } |
31dbd01f IE |
1366 | /* |
1367 | * Nuke all the rmap_items that are above this current rmap: | |
1368 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1369 | */ | |
6514d511 | 1370 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1371 | |
1372 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1373 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1374 | struct mm_slot, mm_list); | |
1375 | if (ksm_scan.address == 0) { | |
1376 | /* | |
1377 | * We've completed a full scan of all vmas, holding mmap_sem | |
1378 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1379 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1380 | * This applies either when cleaning up after __ksm_exit |
1381 | * (but beware: we can reach here even before __ksm_exit), | |
1382 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1383 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1384 | */ |
1385 | hlist_del(&slot->link); | |
1386 | list_del(&slot->mm_list); | |
9ba69294 HD |
1387 | spin_unlock(&ksm_mmlist_lock); |
1388 | ||
cd551f97 HD |
1389 | free_mm_slot(slot); |
1390 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1391 | up_read(&mm->mmap_sem); |
1392 | mmdrop(mm); | |
1393 | } else { | |
1394 | spin_unlock(&ksm_mmlist_lock); | |
1395 | up_read(&mm->mmap_sem); | |
cd551f97 | 1396 | } |
31dbd01f IE |
1397 | |
1398 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1399 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1400 | if (slot != &ksm_mm_head) |
1401 | goto next_mm; | |
1402 | ||
31dbd01f IE |
1403 | ksm_scan.seqnr++; |
1404 | return NULL; | |
1405 | } | |
1406 | ||
1407 | /** | |
1408 | * ksm_do_scan - the ksm scanner main worker function. | |
1409 | * @scan_npages - number of pages we want to scan before we return. | |
1410 | */ | |
1411 | static void ksm_do_scan(unsigned int scan_npages) | |
1412 | { | |
1413 | struct rmap_item *rmap_item; | |
22eccdd7 | 1414 | struct page *uninitialized_var(page); |
31dbd01f | 1415 | |
878aee7d | 1416 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
1417 | cond_resched(); |
1418 | rmap_item = scan_get_next_rmap_item(&page); | |
1419 | if (!rmap_item) | |
1420 | return; | |
1421 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1422 | cmp_and_merge_page(page, rmap_item); | |
1423 | put_page(page); | |
1424 | } | |
1425 | } | |
1426 | ||
6e158384 HD |
1427 | static int ksmd_should_run(void) |
1428 | { | |
1429 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1430 | } | |
1431 | ||
31dbd01f IE |
1432 | static int ksm_scan_thread(void *nothing) |
1433 | { | |
878aee7d | 1434 | set_freezable(); |
339aa624 | 1435 | set_user_nice(current, 5); |
31dbd01f IE |
1436 | |
1437 | while (!kthread_should_stop()) { | |
6e158384 HD |
1438 | mutex_lock(&ksm_thread_mutex); |
1439 | if (ksmd_should_run()) | |
31dbd01f | 1440 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1441 | mutex_unlock(&ksm_thread_mutex); |
1442 | ||
878aee7d AA |
1443 | try_to_freeze(); |
1444 | ||
6e158384 | 1445 | if (ksmd_should_run()) { |
31dbd01f IE |
1446 | schedule_timeout_interruptible( |
1447 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1448 | } else { | |
878aee7d | 1449 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 1450 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1451 | } |
1452 | } | |
1453 | return 0; | |
1454 | } | |
1455 | ||
f8af4da3 HD |
1456 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1457 | unsigned long end, int advice, unsigned long *vm_flags) | |
1458 | { | |
1459 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1460 | int err; |
f8af4da3 HD |
1461 | |
1462 | switch (advice) { | |
1463 | case MADV_MERGEABLE: | |
1464 | /* | |
1465 | * Be somewhat over-protective for now! | |
1466 | */ | |
1467 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1468 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1469 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
5ad64688 | 1470 | VM_NONLINEAR | VM_MIXEDMAP | VM_SAO)) |
f8af4da3 HD |
1471 | return 0; /* just ignore the advice */ |
1472 | ||
d952b791 HD |
1473 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1474 | err = __ksm_enter(mm); | |
1475 | if (err) | |
1476 | return err; | |
1477 | } | |
f8af4da3 HD |
1478 | |
1479 | *vm_flags |= VM_MERGEABLE; | |
1480 | break; | |
1481 | ||
1482 | case MADV_UNMERGEABLE: | |
1483 | if (!(*vm_flags & VM_MERGEABLE)) | |
1484 | return 0; /* just ignore the advice */ | |
1485 | ||
d952b791 HD |
1486 | if (vma->anon_vma) { |
1487 | err = unmerge_ksm_pages(vma, start, end); | |
1488 | if (err) | |
1489 | return err; | |
1490 | } | |
f8af4da3 HD |
1491 | |
1492 | *vm_flags &= ~VM_MERGEABLE; | |
1493 | break; | |
1494 | } | |
1495 | ||
1496 | return 0; | |
1497 | } | |
1498 | ||
1499 | int __ksm_enter(struct mm_struct *mm) | |
1500 | { | |
6e158384 HD |
1501 | struct mm_slot *mm_slot; |
1502 | int needs_wakeup; | |
1503 | ||
1504 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1505 | if (!mm_slot) |
1506 | return -ENOMEM; | |
1507 | ||
6e158384 HD |
1508 | /* Check ksm_run too? Would need tighter locking */ |
1509 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1510 | ||
31dbd01f IE |
1511 | spin_lock(&ksm_mmlist_lock); |
1512 | insert_to_mm_slots_hash(mm, mm_slot); | |
1513 | /* | |
1514 | * Insert just behind the scanning cursor, to let the area settle | |
1515 | * down a little; when fork is followed by immediate exec, we don't | |
1516 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1517 | */ | |
1518 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1519 | spin_unlock(&ksm_mmlist_lock); | |
1520 | ||
f8af4da3 | 1521 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1522 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1523 | |
1524 | if (needs_wakeup) | |
1525 | wake_up_interruptible(&ksm_thread_wait); | |
1526 | ||
f8af4da3 HD |
1527 | return 0; |
1528 | } | |
1529 | ||
1c2fb7a4 | 1530 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1531 | { |
cd551f97 | 1532 | struct mm_slot *mm_slot; |
9ba69294 | 1533 | int easy_to_free = 0; |
cd551f97 | 1534 | |
31dbd01f | 1535 | /* |
9ba69294 HD |
1536 | * This process is exiting: if it's straightforward (as is the |
1537 | * case when ksmd was never running), free mm_slot immediately. | |
1538 | * But if it's at the cursor or has rmap_items linked to it, use | |
1539 | * mmap_sem to synchronize with any break_cows before pagetables | |
1540 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1541 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1542 | */ |
9ba69294 | 1543 | |
cd551f97 HD |
1544 | spin_lock(&ksm_mmlist_lock); |
1545 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1546 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1547 | if (!mm_slot->rmap_list) { |
9ba69294 HD |
1548 | hlist_del(&mm_slot->link); |
1549 | list_del(&mm_slot->mm_list); | |
1550 | easy_to_free = 1; | |
1551 | } else { | |
1552 | list_move(&mm_slot->mm_list, | |
1553 | &ksm_scan.mm_slot->mm_list); | |
1554 | } | |
cd551f97 | 1555 | } |
cd551f97 HD |
1556 | spin_unlock(&ksm_mmlist_lock); |
1557 | ||
9ba69294 HD |
1558 | if (easy_to_free) { |
1559 | free_mm_slot(mm_slot); | |
1560 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1561 | mmdrop(mm); | |
1562 | } else if (mm_slot) { | |
9ba69294 HD |
1563 | down_write(&mm->mmap_sem); |
1564 | up_write(&mm->mmap_sem); | |
9ba69294 | 1565 | } |
31dbd01f IE |
1566 | } |
1567 | ||
5ad64688 HD |
1568 | struct page *ksm_does_need_to_copy(struct page *page, |
1569 | struct vm_area_struct *vma, unsigned long address) | |
1570 | { | |
1571 | struct page *new_page; | |
1572 | ||
5ad64688 HD |
1573 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
1574 | if (new_page) { | |
4e5f01c2 KH |
1575 | /* |
1576 | * The memcg-specific accounting when moving | |
1577 | * pages around the LRU lists relies on the | |
1578 | * page's owner (memcg) to be valid. Usually, | |
1579 | * pages are assigned to a new owner before | |
1580 | * being put on the LRU list, but since this | |
1581 | * is not the case here, the stale owner from | |
1582 | * a previous allocation cycle must be reset. | |
1583 | */ | |
1584 | mem_cgroup_reset_owner(new_page); | |
5ad64688 HD |
1585 | copy_user_highpage(new_page, page, address, vma); |
1586 | ||
1587 | SetPageDirty(new_page); | |
1588 | __SetPageUptodate(new_page); | |
1589 | SetPageSwapBacked(new_page); | |
1590 | __set_page_locked(new_page); | |
1591 | ||
1592 | if (page_evictable(new_page, vma)) | |
1593 | lru_cache_add_lru(new_page, LRU_ACTIVE_ANON); | |
1594 | else | |
1595 | add_page_to_unevictable_list(new_page); | |
1596 | } | |
1597 | ||
5ad64688 HD |
1598 | return new_page; |
1599 | } | |
1600 | ||
1601 | int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg, | |
1602 | unsigned long *vm_flags) | |
1603 | { | |
1604 | struct stable_node *stable_node; | |
1605 | struct rmap_item *rmap_item; | |
1606 | struct hlist_node *hlist; | |
1607 | unsigned int mapcount = page_mapcount(page); | |
1608 | int referenced = 0; | |
db114b83 | 1609 | int search_new_forks = 0; |
5ad64688 HD |
1610 | |
1611 | VM_BUG_ON(!PageKsm(page)); | |
1612 | VM_BUG_ON(!PageLocked(page)); | |
1613 | ||
1614 | stable_node = page_stable_node(page); | |
1615 | if (!stable_node) | |
1616 | return 0; | |
db114b83 | 1617 | again: |
5ad64688 | 1618 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { |
db114b83 | 1619 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 1620 | struct anon_vma_chain *vmac; |
db114b83 | 1621 | struct vm_area_struct *vma; |
5ad64688 | 1622 | |
cba48b98 | 1623 | anon_vma_lock(anon_vma); |
5beb4930 RR |
1624 | list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { |
1625 | vma = vmac->vma; | |
db114b83 HD |
1626 | if (rmap_item->address < vma->vm_start || |
1627 | rmap_item->address >= vma->vm_end) | |
1628 | continue; | |
1629 | /* | |
1630 | * Initially we examine only the vma which covers this | |
1631 | * rmap_item; but later, if there is still work to do, | |
1632 | * we examine covering vmas in other mms: in case they | |
1633 | * were forked from the original since ksmd passed. | |
1634 | */ | |
1635 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
1636 | continue; | |
1637 | ||
1638 | if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) | |
1639 | continue; | |
5ad64688 | 1640 | |
db114b83 | 1641 | referenced += page_referenced_one(page, vma, |
5ad64688 | 1642 | rmap_item->address, &mapcount, vm_flags); |
db114b83 HD |
1643 | if (!search_new_forks || !mapcount) |
1644 | break; | |
1645 | } | |
cba48b98 | 1646 | anon_vma_unlock(anon_vma); |
5ad64688 HD |
1647 | if (!mapcount) |
1648 | goto out; | |
1649 | } | |
db114b83 HD |
1650 | if (!search_new_forks++) |
1651 | goto again; | |
5ad64688 | 1652 | out: |
5ad64688 HD |
1653 | return referenced; |
1654 | } | |
1655 | ||
1656 | int try_to_unmap_ksm(struct page *page, enum ttu_flags flags) | |
1657 | { | |
1658 | struct stable_node *stable_node; | |
1659 | struct hlist_node *hlist; | |
1660 | struct rmap_item *rmap_item; | |
1661 | int ret = SWAP_AGAIN; | |
db114b83 | 1662 | int search_new_forks = 0; |
5ad64688 HD |
1663 | |
1664 | VM_BUG_ON(!PageKsm(page)); | |
1665 | VM_BUG_ON(!PageLocked(page)); | |
1666 | ||
1667 | stable_node = page_stable_node(page); | |
1668 | if (!stable_node) | |
1669 | return SWAP_FAIL; | |
db114b83 | 1670 | again: |
5ad64688 | 1671 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { |
db114b83 | 1672 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 1673 | struct anon_vma_chain *vmac; |
db114b83 | 1674 | struct vm_area_struct *vma; |
5ad64688 | 1675 | |
cba48b98 | 1676 | anon_vma_lock(anon_vma); |
5beb4930 RR |
1677 | list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { |
1678 | vma = vmac->vma; | |
db114b83 HD |
1679 | if (rmap_item->address < vma->vm_start || |
1680 | rmap_item->address >= vma->vm_end) | |
1681 | continue; | |
1682 | /* | |
1683 | * Initially we examine only the vma which covers this | |
1684 | * rmap_item; but later, if there is still work to do, | |
1685 | * we examine covering vmas in other mms: in case they | |
1686 | * were forked from the original since ksmd passed. | |
1687 | */ | |
1688 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
1689 | continue; | |
1690 | ||
1691 | ret = try_to_unmap_one(page, vma, | |
1692 | rmap_item->address, flags); | |
1693 | if (ret != SWAP_AGAIN || !page_mapped(page)) { | |
cba48b98 | 1694 | anon_vma_unlock(anon_vma); |
db114b83 HD |
1695 | goto out; |
1696 | } | |
1697 | } | |
cba48b98 | 1698 | anon_vma_unlock(anon_vma); |
5ad64688 | 1699 | } |
db114b83 HD |
1700 | if (!search_new_forks++) |
1701 | goto again; | |
5ad64688 | 1702 | out: |
5ad64688 HD |
1703 | return ret; |
1704 | } | |
1705 | ||
e9995ef9 HD |
1706 | #ifdef CONFIG_MIGRATION |
1707 | int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *, | |
1708 | struct vm_area_struct *, unsigned long, void *), void *arg) | |
1709 | { | |
1710 | struct stable_node *stable_node; | |
1711 | struct hlist_node *hlist; | |
1712 | struct rmap_item *rmap_item; | |
1713 | int ret = SWAP_AGAIN; | |
1714 | int search_new_forks = 0; | |
1715 | ||
1716 | VM_BUG_ON(!PageKsm(page)); | |
1717 | VM_BUG_ON(!PageLocked(page)); | |
1718 | ||
1719 | stable_node = page_stable_node(page); | |
1720 | if (!stable_node) | |
1721 | return ret; | |
1722 | again: | |
1723 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { | |
1724 | struct anon_vma *anon_vma = rmap_item->anon_vma; | |
5beb4930 | 1725 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
1726 | struct vm_area_struct *vma; |
1727 | ||
cba48b98 | 1728 | anon_vma_lock(anon_vma); |
5beb4930 RR |
1729 | list_for_each_entry(vmac, &anon_vma->head, same_anon_vma) { |
1730 | vma = vmac->vma; | |
e9995ef9 HD |
1731 | if (rmap_item->address < vma->vm_start || |
1732 | rmap_item->address >= vma->vm_end) | |
1733 | continue; | |
1734 | /* | |
1735 | * Initially we examine only the vma which covers this | |
1736 | * rmap_item; but later, if there is still work to do, | |
1737 | * we examine covering vmas in other mms: in case they | |
1738 | * were forked from the original since ksmd passed. | |
1739 | */ | |
1740 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
1741 | continue; | |
1742 | ||
1743 | ret = rmap_one(page, vma, rmap_item->address, arg); | |
1744 | if (ret != SWAP_AGAIN) { | |
cba48b98 | 1745 | anon_vma_unlock(anon_vma); |
e9995ef9 HD |
1746 | goto out; |
1747 | } | |
1748 | } | |
cba48b98 | 1749 | anon_vma_unlock(anon_vma); |
e9995ef9 HD |
1750 | } |
1751 | if (!search_new_forks++) | |
1752 | goto again; | |
1753 | out: | |
1754 | return ret; | |
1755 | } | |
1756 | ||
1757 | void ksm_migrate_page(struct page *newpage, struct page *oldpage) | |
1758 | { | |
1759 | struct stable_node *stable_node; | |
1760 | ||
1761 | VM_BUG_ON(!PageLocked(oldpage)); | |
1762 | VM_BUG_ON(!PageLocked(newpage)); | |
1763 | VM_BUG_ON(newpage->mapping != oldpage->mapping); | |
1764 | ||
1765 | stable_node = page_stable_node(newpage); | |
1766 | if (stable_node) { | |
62b61f61 HD |
1767 | VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage)); |
1768 | stable_node->kpfn = page_to_pfn(newpage); | |
e9995ef9 HD |
1769 | } |
1770 | } | |
1771 | #endif /* CONFIG_MIGRATION */ | |
1772 | ||
62b61f61 HD |
1773 | #ifdef CONFIG_MEMORY_HOTREMOVE |
1774 | static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, | |
1775 | unsigned long end_pfn) | |
1776 | { | |
1777 | struct rb_node *node; | |
1778 | ||
1779 | for (node = rb_first(&root_stable_tree); node; node = rb_next(node)) { | |
1780 | struct stable_node *stable_node; | |
1781 | ||
1782 | stable_node = rb_entry(node, struct stable_node, node); | |
1783 | if (stable_node->kpfn >= start_pfn && | |
1784 | stable_node->kpfn < end_pfn) | |
1785 | return stable_node; | |
1786 | } | |
1787 | return NULL; | |
1788 | } | |
1789 | ||
1790 | static int ksm_memory_callback(struct notifier_block *self, | |
1791 | unsigned long action, void *arg) | |
1792 | { | |
1793 | struct memory_notify *mn = arg; | |
1794 | struct stable_node *stable_node; | |
1795 | ||
1796 | switch (action) { | |
1797 | case MEM_GOING_OFFLINE: | |
1798 | /* | |
1799 | * Keep it very simple for now: just lock out ksmd and | |
1800 | * MADV_UNMERGEABLE while any memory is going offline. | |
a0b0f58c KM |
1801 | * mutex_lock_nested() is necessary because lockdep was alarmed |
1802 | * that here we take ksm_thread_mutex inside notifier chain | |
1803 | * mutex, and later take notifier chain mutex inside | |
1804 | * ksm_thread_mutex to unlock it. But that's safe because both | |
1805 | * are inside mem_hotplug_mutex. | |
62b61f61 | 1806 | */ |
a0b0f58c | 1807 | mutex_lock_nested(&ksm_thread_mutex, SINGLE_DEPTH_NESTING); |
62b61f61 HD |
1808 | break; |
1809 | ||
1810 | case MEM_OFFLINE: | |
1811 | /* | |
1812 | * Most of the work is done by page migration; but there might | |
1813 | * be a few stable_nodes left over, still pointing to struct | |
1814 | * pages which have been offlined: prune those from the tree. | |
1815 | */ | |
1816 | while ((stable_node = ksm_check_stable_tree(mn->start_pfn, | |
1817 | mn->start_pfn + mn->nr_pages)) != NULL) | |
1818 | remove_node_from_stable_tree(stable_node); | |
1819 | /* fallthrough */ | |
1820 | ||
1821 | case MEM_CANCEL_OFFLINE: | |
1822 | mutex_unlock(&ksm_thread_mutex); | |
1823 | break; | |
1824 | } | |
1825 | return NOTIFY_OK; | |
1826 | } | |
1827 | #endif /* CONFIG_MEMORY_HOTREMOVE */ | |
1828 | ||
2ffd8679 HD |
1829 | #ifdef CONFIG_SYSFS |
1830 | /* | |
1831 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1832 | */ | |
1833 | ||
31dbd01f IE |
1834 | #define KSM_ATTR_RO(_name) \ |
1835 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1836 | #define KSM_ATTR(_name) \ | |
1837 | static struct kobj_attribute _name##_attr = \ | |
1838 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1839 | ||
1840 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1841 | struct kobj_attribute *attr, char *buf) | |
1842 | { | |
1843 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1844 | } | |
1845 | ||
1846 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1847 | struct kobj_attribute *attr, | |
1848 | const char *buf, size_t count) | |
1849 | { | |
1850 | unsigned long msecs; | |
1851 | int err; | |
1852 | ||
1853 | err = strict_strtoul(buf, 10, &msecs); | |
1854 | if (err || msecs > UINT_MAX) | |
1855 | return -EINVAL; | |
1856 | ||
1857 | ksm_thread_sleep_millisecs = msecs; | |
1858 | ||
1859 | return count; | |
1860 | } | |
1861 | KSM_ATTR(sleep_millisecs); | |
1862 | ||
1863 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1864 | struct kobj_attribute *attr, char *buf) | |
1865 | { | |
1866 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1867 | } | |
1868 | ||
1869 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1870 | struct kobj_attribute *attr, | |
1871 | const char *buf, size_t count) | |
1872 | { | |
1873 | int err; | |
1874 | unsigned long nr_pages; | |
1875 | ||
1876 | err = strict_strtoul(buf, 10, &nr_pages); | |
1877 | if (err || nr_pages > UINT_MAX) | |
1878 | return -EINVAL; | |
1879 | ||
1880 | ksm_thread_pages_to_scan = nr_pages; | |
1881 | ||
1882 | return count; | |
1883 | } | |
1884 | KSM_ATTR(pages_to_scan); | |
1885 | ||
1886 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1887 | char *buf) | |
1888 | { | |
1889 | return sprintf(buf, "%u\n", ksm_run); | |
1890 | } | |
1891 | ||
1892 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1893 | const char *buf, size_t count) | |
1894 | { | |
1895 | int err; | |
1896 | unsigned long flags; | |
1897 | ||
1898 | err = strict_strtoul(buf, 10, &flags); | |
1899 | if (err || flags > UINT_MAX) | |
1900 | return -EINVAL; | |
1901 | if (flags > KSM_RUN_UNMERGE) | |
1902 | return -EINVAL; | |
1903 | ||
1904 | /* | |
1905 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1906 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
1907 | * breaking COW to free the pages_shared (but leaves mm_slots |
1908 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
1909 | */ |
1910 | ||
1911 | mutex_lock(&ksm_thread_mutex); | |
1912 | if (ksm_run != flags) { | |
1913 | ksm_run = flags; | |
d952b791 | 1914 | if (flags & KSM_RUN_UNMERGE) { |
72788c38 DR |
1915 | int oom_score_adj; |
1916 | ||
1917 | oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX); | |
d952b791 | 1918 | err = unmerge_and_remove_all_rmap_items(); |
43362a49 DR |
1919 | compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, |
1920 | oom_score_adj); | |
d952b791 HD |
1921 | if (err) { |
1922 | ksm_run = KSM_RUN_STOP; | |
1923 | count = err; | |
1924 | } | |
1925 | } | |
31dbd01f IE |
1926 | } |
1927 | mutex_unlock(&ksm_thread_mutex); | |
1928 | ||
1929 | if (flags & KSM_RUN_MERGE) | |
1930 | wake_up_interruptible(&ksm_thread_wait); | |
1931 | ||
1932 | return count; | |
1933 | } | |
1934 | KSM_ATTR(run); | |
1935 | ||
b4028260 HD |
1936 | static ssize_t pages_shared_show(struct kobject *kobj, |
1937 | struct kobj_attribute *attr, char *buf) | |
1938 | { | |
1939 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1940 | } | |
1941 | KSM_ATTR_RO(pages_shared); | |
1942 | ||
1943 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1944 | struct kobj_attribute *attr, char *buf) | |
1945 | { | |
e178dfde | 1946 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1947 | } |
1948 | KSM_ATTR_RO(pages_sharing); | |
1949 | ||
473b0ce4 HD |
1950 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1951 | struct kobj_attribute *attr, char *buf) | |
1952 | { | |
1953 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1954 | } | |
1955 | KSM_ATTR_RO(pages_unshared); | |
1956 | ||
1957 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1958 | struct kobj_attribute *attr, char *buf) | |
1959 | { | |
1960 | long ksm_pages_volatile; | |
1961 | ||
1962 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1963 | - ksm_pages_sharing - ksm_pages_unshared; | |
1964 | /* | |
1965 | * It was not worth any locking to calculate that statistic, | |
1966 | * but it might therefore sometimes be negative: conceal that. | |
1967 | */ | |
1968 | if (ksm_pages_volatile < 0) | |
1969 | ksm_pages_volatile = 0; | |
1970 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1971 | } | |
1972 | KSM_ATTR_RO(pages_volatile); | |
1973 | ||
1974 | static ssize_t full_scans_show(struct kobject *kobj, | |
1975 | struct kobj_attribute *attr, char *buf) | |
1976 | { | |
1977 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1978 | } | |
1979 | KSM_ATTR_RO(full_scans); | |
1980 | ||
31dbd01f IE |
1981 | static struct attribute *ksm_attrs[] = { |
1982 | &sleep_millisecs_attr.attr, | |
1983 | &pages_to_scan_attr.attr, | |
1984 | &run_attr.attr, | |
b4028260 HD |
1985 | &pages_shared_attr.attr, |
1986 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1987 | &pages_unshared_attr.attr, |
1988 | &pages_volatile_attr.attr, | |
1989 | &full_scans_attr.attr, | |
31dbd01f IE |
1990 | NULL, |
1991 | }; | |
1992 | ||
1993 | static struct attribute_group ksm_attr_group = { | |
1994 | .attrs = ksm_attrs, | |
1995 | .name = "ksm", | |
1996 | }; | |
2ffd8679 | 1997 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1998 | |
1999 | static int __init ksm_init(void) | |
2000 | { | |
2001 | struct task_struct *ksm_thread; | |
2002 | int err; | |
2003 | ||
2004 | err = ksm_slab_init(); | |
2005 | if (err) | |
2006 | goto out; | |
2007 | ||
31dbd01f IE |
2008 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
2009 | if (IS_ERR(ksm_thread)) { | |
2010 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
2011 | err = PTR_ERR(ksm_thread); | |
d9f8984c | 2012 | goto out_free; |
31dbd01f IE |
2013 | } |
2014 | ||
2ffd8679 | 2015 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
2016 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
2017 | if (err) { | |
2018 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 | 2019 | kthread_stop(ksm_thread); |
d9f8984c | 2020 | goto out_free; |
31dbd01f | 2021 | } |
c73602ad HD |
2022 | #else |
2023 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
2024 | ||
2ffd8679 | 2025 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 2026 | |
62b61f61 HD |
2027 | #ifdef CONFIG_MEMORY_HOTREMOVE |
2028 | /* | |
2029 | * Choose a high priority since the callback takes ksm_thread_mutex: | |
2030 | * later callbacks could only be taking locks which nest within that. | |
2031 | */ | |
2032 | hotplug_memory_notifier(ksm_memory_callback, 100); | |
2033 | #endif | |
31dbd01f IE |
2034 | return 0; |
2035 | ||
d9f8984c | 2036 | out_free: |
31dbd01f IE |
2037 | ksm_slab_free(); |
2038 | out: | |
2039 | return err; | |
f8af4da3 | 2040 | } |
31dbd01f | 2041 | module_init(ksm_init) |