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 | |
110 | * @node: rb node of this ksm page in the stable tree | |
111 | * @hlist: hlist head of rmap_items using this ksm page | |
112 | */ | |
113 | struct stable_node { | |
114 | struct rb_node node; | |
115 | struct hlist_head hlist; | |
116 | }; | |
117 | ||
31dbd01f IE |
118 | /** |
119 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 HD |
120 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
121 | * @filler: unused space we're making available in this patch | |
31dbd01f IE |
122 | * @mm: the memory structure this rmap_item is pointing into |
123 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
124 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
125 | * @node: rb node of this rmap_item in the unstable tree |
126 | * @head: pointer to stable_node heading this list in the stable tree | |
127 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
128 | */ |
129 | struct rmap_item { | |
6514d511 HD |
130 | struct rmap_item *rmap_list; |
131 | unsigned long filler; | |
31dbd01f IE |
132 | struct mm_struct *mm; |
133 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 134 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 135 | union { |
7b6ba2c7 HD |
136 | struct rb_node node; /* when node of unstable tree */ |
137 | struct { /* when listed from stable tree */ | |
138 | struct stable_node *head; | |
139 | struct hlist_node hlist; | |
140 | }; | |
31dbd01f IE |
141 | }; |
142 | }; | |
143 | ||
144 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
145 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
146 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
147 | |
148 | /* The stable and unstable tree heads */ | |
149 | static struct rb_root root_stable_tree = RB_ROOT; | |
150 | static struct rb_root root_unstable_tree = RB_ROOT; | |
151 | ||
152 | #define MM_SLOTS_HASH_HEADS 1024 | |
153 | static struct hlist_head *mm_slots_hash; | |
154 | ||
155 | static struct mm_slot ksm_mm_head = { | |
156 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
157 | }; | |
158 | static struct ksm_scan ksm_scan = { | |
159 | .mm_slot = &ksm_mm_head, | |
160 | }; | |
161 | ||
162 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 163 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
164 | static struct kmem_cache *mm_slot_cache; |
165 | ||
166 | /* The number of nodes in the stable tree */ | |
b4028260 | 167 | static unsigned long ksm_pages_shared; |
31dbd01f | 168 | |
e178dfde | 169 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 170 | static unsigned long ksm_pages_sharing; |
31dbd01f | 171 | |
473b0ce4 HD |
172 | /* The number of nodes in the unstable tree */ |
173 | static unsigned long ksm_pages_unshared; | |
174 | ||
175 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
176 | static unsigned long ksm_rmap_items; | |
177 | ||
31dbd01f | 178 | /* Limit on the number of unswappable pages used */ |
2c6854fd | 179 | static unsigned long ksm_max_kernel_pages; |
31dbd01f IE |
180 | |
181 | /* Number of pages ksmd should scan in one batch */ | |
2c6854fd | 182 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
183 | |
184 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 185 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
186 | |
187 | #define KSM_RUN_STOP 0 | |
188 | #define KSM_RUN_MERGE 1 | |
189 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 190 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
191 | |
192 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
193 | static DEFINE_MUTEX(ksm_thread_mutex); | |
194 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
195 | ||
196 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
197 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
198 | (__flags), NULL) | |
199 | ||
200 | static int __init ksm_slab_init(void) | |
201 | { | |
202 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
203 | if (!rmap_item_cache) | |
204 | goto out; | |
205 | ||
7b6ba2c7 HD |
206 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
207 | if (!stable_node_cache) | |
208 | goto out_free1; | |
209 | ||
31dbd01f IE |
210 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
211 | if (!mm_slot_cache) | |
7b6ba2c7 | 212 | goto out_free2; |
31dbd01f IE |
213 | |
214 | return 0; | |
215 | ||
7b6ba2c7 HD |
216 | out_free2: |
217 | kmem_cache_destroy(stable_node_cache); | |
218 | out_free1: | |
31dbd01f IE |
219 | kmem_cache_destroy(rmap_item_cache); |
220 | out: | |
221 | return -ENOMEM; | |
222 | } | |
223 | ||
224 | static void __init ksm_slab_free(void) | |
225 | { | |
226 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 227 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
228 | kmem_cache_destroy(rmap_item_cache); |
229 | mm_slot_cache = NULL; | |
230 | } | |
231 | ||
232 | static inline struct rmap_item *alloc_rmap_item(void) | |
233 | { | |
473b0ce4 HD |
234 | struct rmap_item *rmap_item; |
235 | ||
236 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
237 | if (rmap_item) | |
238 | ksm_rmap_items++; | |
239 | return rmap_item; | |
31dbd01f IE |
240 | } |
241 | ||
242 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
243 | { | |
473b0ce4 | 244 | ksm_rmap_items--; |
31dbd01f IE |
245 | rmap_item->mm = NULL; /* debug safety */ |
246 | kmem_cache_free(rmap_item_cache, rmap_item); | |
247 | } | |
248 | ||
7b6ba2c7 HD |
249 | static inline struct stable_node *alloc_stable_node(void) |
250 | { | |
251 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
252 | } | |
253 | ||
254 | static inline void free_stable_node(struct stable_node *stable_node) | |
255 | { | |
256 | kmem_cache_free(stable_node_cache, stable_node); | |
257 | } | |
258 | ||
31dbd01f IE |
259 | static inline struct mm_slot *alloc_mm_slot(void) |
260 | { | |
261 | if (!mm_slot_cache) /* initialization failed */ | |
262 | return NULL; | |
263 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
264 | } | |
265 | ||
266 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
267 | { | |
268 | kmem_cache_free(mm_slot_cache, mm_slot); | |
269 | } | |
270 | ||
271 | static int __init mm_slots_hash_init(void) | |
272 | { | |
273 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), | |
274 | GFP_KERNEL); | |
275 | if (!mm_slots_hash) | |
276 | return -ENOMEM; | |
277 | return 0; | |
278 | } | |
279 | ||
280 | static void __init mm_slots_hash_free(void) | |
281 | { | |
282 | kfree(mm_slots_hash); | |
283 | } | |
284 | ||
285 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
286 | { | |
287 | struct mm_slot *mm_slot; | |
288 | struct hlist_head *bucket; | |
289 | struct hlist_node *node; | |
290 | ||
291 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
292 | % MM_SLOTS_HASH_HEADS]; | |
293 | hlist_for_each_entry(mm_slot, node, bucket, link) { | |
294 | if (mm == mm_slot->mm) | |
295 | return mm_slot; | |
296 | } | |
297 | return NULL; | |
298 | } | |
299 | ||
300 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
301 | struct mm_slot *mm_slot) | |
302 | { | |
303 | struct hlist_head *bucket; | |
304 | ||
305 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
306 | % MM_SLOTS_HASH_HEADS]; | |
307 | mm_slot->mm = mm; | |
31dbd01f IE |
308 | hlist_add_head(&mm_slot->link, bucket); |
309 | } | |
310 | ||
311 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
312 | { | |
313 | return rmap_item->address & STABLE_FLAG; | |
314 | } | |
315 | ||
a913e182 HD |
316 | /* |
317 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
318 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
319 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
320 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
321 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
322 | * places for correctness, in some places just to avoid unnecessary work. | |
323 | */ | |
324 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
325 | { | |
326 | return atomic_read(&mm->mm_users) == 0; | |
327 | } | |
328 | ||
31dbd01f IE |
329 | /* |
330 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
331 | * | |
332 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
333 | * put_page(page); | |
334 | * | |
335 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
336 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
337 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
338 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
339 | */ | |
d952b791 | 340 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
341 | { |
342 | struct page *page; | |
d952b791 | 343 | int ret = 0; |
31dbd01f IE |
344 | |
345 | do { | |
346 | cond_resched(); | |
347 | page = follow_page(vma, addr, FOLL_GET); | |
348 | if (!page) | |
349 | break; | |
350 | if (PageKsm(page)) | |
351 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
352 | FAULT_FLAG_WRITE); | |
353 | else | |
354 | ret = VM_FAULT_WRITE; | |
355 | put_page(page); | |
d952b791 HD |
356 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
357 | /* | |
358 | * We must loop because handle_mm_fault() may back out if there's | |
359 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
360 | * | |
361 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
362 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
363 | * but note that a concurrent fault might break PageKsm for us. | |
364 | * | |
365 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
366 | * backing file, which also invalidates anonymous pages: that's | |
367 | * okay, that truncation will have unmapped the PageKsm for us. | |
368 | * | |
369 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
370 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
371 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
372 | * to user; and ksmd, having no mm, would never be chosen for that. | |
373 | * | |
374 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
375 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
376 | * even ksmd can fail in this way - though it's usually breaking ksm | |
377 | * just to undo a merge it made a moment before, so unlikely to oom. | |
378 | * | |
379 | * That's a pity: we might therefore have more kernel pages allocated | |
380 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
381 | * will retry to break_cow on each pass, so should recover the page | |
382 | * in due course. The important thing is to not let VM_MERGEABLE | |
383 | * be cleared while any such pages might remain in the area. | |
384 | */ | |
385 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
386 | } |
387 | ||
8dd3557a | 388 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 389 | { |
8dd3557a HD |
390 | struct mm_struct *mm = rmap_item->mm; |
391 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
392 | struct vm_area_struct *vma; |
393 | ||
81464e30 | 394 | down_read(&mm->mmap_sem); |
9ba69294 HD |
395 | if (ksm_test_exit(mm)) |
396 | goto out; | |
31dbd01f IE |
397 | vma = find_vma(mm, addr); |
398 | if (!vma || vma->vm_start > addr) | |
81464e30 | 399 | goto out; |
31dbd01f | 400 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 401 | goto out; |
31dbd01f | 402 | break_ksm(vma, addr); |
81464e30 | 403 | out: |
31dbd01f IE |
404 | up_read(&mm->mmap_sem); |
405 | } | |
406 | ||
407 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
408 | { | |
409 | struct mm_struct *mm = rmap_item->mm; | |
410 | unsigned long addr = rmap_item->address; | |
411 | struct vm_area_struct *vma; | |
412 | struct page *page; | |
413 | ||
414 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
415 | if (ksm_test_exit(mm)) |
416 | goto out; | |
31dbd01f IE |
417 | vma = find_vma(mm, addr); |
418 | if (!vma || vma->vm_start > addr) | |
419 | goto out; | |
420 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
421 | goto out; | |
422 | ||
423 | page = follow_page(vma, addr, FOLL_GET); | |
424 | if (!page) | |
425 | goto out; | |
426 | if (PageAnon(page)) { | |
427 | flush_anon_page(vma, page, addr); | |
428 | flush_dcache_page(page); | |
429 | } else { | |
430 | put_page(page); | |
431 | out: page = NULL; | |
432 | } | |
433 | up_read(&mm->mmap_sem); | |
434 | return page; | |
435 | } | |
436 | ||
437 | /* | |
438 | * get_ksm_page: checks if the page at the virtual address in rmap_item | |
439 | * is still PageKsm, in which case we can trust the content of the page, | |
440 | * and it returns the gotten page; but NULL if the page has been zapped. | |
441 | */ | |
442 | static struct page *get_ksm_page(struct rmap_item *rmap_item) | |
443 | { | |
444 | struct page *page; | |
445 | ||
446 | page = get_mergeable_page(rmap_item); | |
447 | if (page && !PageKsm(page)) { | |
448 | put_page(page); | |
449 | page = NULL; | |
450 | } | |
451 | return page; | |
452 | } | |
453 | ||
454 | /* | |
455 | * Removing rmap_item from stable or unstable tree. | |
456 | * This function will clean the information from the stable/unstable tree. | |
457 | */ | |
458 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
459 | { | |
7b6ba2c7 HD |
460 | if (rmap_item->address & STABLE_FLAG) { |
461 | struct stable_node *stable_node; | |
31dbd01f | 462 | |
7b6ba2c7 HD |
463 | stable_node = rmap_item->head; |
464 | hlist_del(&rmap_item->hlist); | |
465 | if (stable_node->hlist.first) | |
e178dfde | 466 | ksm_pages_sharing--; |
7b6ba2c7 HD |
467 | else { |
468 | rb_erase(&stable_node->node, &root_stable_tree); | |
469 | free_stable_node(stable_node); | |
470 | ksm_pages_shared--; | |
31dbd01f IE |
471 | } |
472 | ||
93d17715 | 473 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 474 | |
7b6ba2c7 | 475 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
476 | unsigned char age; |
477 | /* | |
9ba69294 | 478 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 479 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
480 | * But be careful when an mm is exiting: do the rb_erase |
481 | * if this rmap_item was inserted by this scan, rather | |
482 | * than left over from before. | |
31dbd01f IE |
483 | */ |
484 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 485 | BUG_ON(age > 1); |
31dbd01f IE |
486 | if (!age) |
487 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
93d17715 | 488 | |
473b0ce4 | 489 | ksm_pages_unshared--; |
93d17715 | 490 | rmap_item->address &= PAGE_MASK; |
31dbd01f IE |
491 | } |
492 | ||
31dbd01f IE |
493 | cond_resched(); /* we're called from many long loops */ |
494 | } | |
495 | ||
31dbd01f | 496 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 497 | struct rmap_item **rmap_list) |
31dbd01f | 498 | { |
6514d511 HD |
499 | while (*rmap_list) { |
500 | struct rmap_item *rmap_item = *rmap_list; | |
501 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 502 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
503 | free_rmap_item(rmap_item); |
504 | } | |
505 | } | |
506 | ||
507 | /* | |
508 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather | |
509 | * than check every pte of a given vma, the locking doesn't quite work for | |
510 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
511 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
512 | * rmap_items from parent to child at fork time (so as not to waste time | |
513 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
514 | * |
515 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
516 | * and freeing memory) when unmerging an area, it's easier to leave that | |
517 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
518 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 519 | */ |
d952b791 HD |
520 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
521 | unsigned long start, unsigned long end) | |
31dbd01f IE |
522 | { |
523 | unsigned long addr; | |
d952b791 | 524 | int err = 0; |
31dbd01f | 525 | |
d952b791 | 526 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
527 | if (ksm_test_exit(vma->vm_mm)) |
528 | break; | |
d952b791 HD |
529 | if (signal_pending(current)) |
530 | err = -ERESTARTSYS; | |
531 | else | |
532 | err = break_ksm(vma, addr); | |
533 | } | |
534 | return err; | |
31dbd01f IE |
535 | } |
536 | ||
2ffd8679 HD |
537 | #ifdef CONFIG_SYSFS |
538 | /* | |
539 | * Only called through the sysfs control interface: | |
540 | */ | |
d952b791 | 541 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
542 | { |
543 | struct mm_slot *mm_slot; | |
544 | struct mm_struct *mm; | |
545 | struct vm_area_struct *vma; | |
d952b791 HD |
546 | int err = 0; |
547 | ||
548 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 549 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
550 | struct mm_slot, mm_list); |
551 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 552 | |
9ba69294 HD |
553 | for (mm_slot = ksm_scan.mm_slot; |
554 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
555 | mm = mm_slot->mm; |
556 | down_read(&mm->mmap_sem); | |
557 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
558 | if (ksm_test_exit(mm)) |
559 | break; | |
31dbd01f IE |
560 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
561 | continue; | |
d952b791 HD |
562 | err = unmerge_ksm_pages(vma, |
563 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
564 | if (err) |
565 | goto error; | |
31dbd01f | 566 | } |
9ba69294 | 567 | |
6514d511 | 568 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
569 | |
570 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 571 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 572 | struct mm_slot, mm_list); |
9ba69294 HD |
573 | if (ksm_test_exit(mm)) { |
574 | hlist_del(&mm_slot->link); | |
575 | list_del(&mm_slot->mm_list); | |
576 | spin_unlock(&ksm_mmlist_lock); | |
577 | ||
578 | free_mm_slot(mm_slot); | |
579 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
580 | up_read(&mm->mmap_sem); | |
581 | mmdrop(mm); | |
582 | } else { | |
583 | spin_unlock(&ksm_mmlist_lock); | |
584 | up_read(&mm->mmap_sem); | |
585 | } | |
31dbd01f IE |
586 | } |
587 | ||
d952b791 | 588 | ksm_scan.seqnr = 0; |
9ba69294 HD |
589 | return 0; |
590 | ||
591 | error: | |
592 | up_read(&mm->mmap_sem); | |
31dbd01f | 593 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 594 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 595 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 596 | return err; |
31dbd01f | 597 | } |
2ffd8679 | 598 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 599 | |
31dbd01f IE |
600 | static u32 calc_checksum(struct page *page) |
601 | { | |
602 | u32 checksum; | |
603 | void *addr = kmap_atomic(page, KM_USER0); | |
604 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); | |
605 | kunmap_atomic(addr, KM_USER0); | |
606 | return checksum; | |
607 | } | |
608 | ||
609 | static int memcmp_pages(struct page *page1, struct page *page2) | |
610 | { | |
611 | char *addr1, *addr2; | |
612 | int ret; | |
613 | ||
614 | addr1 = kmap_atomic(page1, KM_USER0); | |
615 | addr2 = kmap_atomic(page2, KM_USER1); | |
616 | ret = memcmp(addr1, addr2, PAGE_SIZE); | |
617 | kunmap_atomic(addr2, KM_USER1); | |
618 | kunmap_atomic(addr1, KM_USER0); | |
619 | return ret; | |
620 | } | |
621 | ||
622 | static inline int pages_identical(struct page *page1, struct page *page2) | |
623 | { | |
624 | return !memcmp_pages(page1, page2); | |
625 | } | |
626 | ||
627 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
628 | pte_t *orig_pte) | |
629 | { | |
630 | struct mm_struct *mm = vma->vm_mm; | |
631 | unsigned long addr; | |
632 | pte_t *ptep; | |
633 | spinlock_t *ptl; | |
634 | int swapped; | |
635 | int err = -EFAULT; | |
636 | ||
637 | addr = page_address_in_vma(page, vma); | |
638 | if (addr == -EFAULT) | |
639 | goto out; | |
640 | ||
641 | ptep = page_check_address(page, mm, addr, &ptl, 0); | |
642 | if (!ptep) | |
643 | goto out; | |
644 | ||
645 | if (pte_write(*ptep)) { | |
646 | pte_t entry; | |
647 | ||
648 | swapped = PageSwapCache(page); | |
649 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
650 | /* | |
651 | * Ok this is tricky, when get_user_pages_fast() run it doesnt | |
652 | * take any lock, therefore the check that we are going to make | |
653 | * with the pagecount against the mapcount is racey and | |
654 | * O_DIRECT can happen right after the check. | |
655 | * So we clear the pte and flush the tlb before the check | |
656 | * this assure us that no O_DIRECT can happen after the check | |
657 | * or in the middle of the check. | |
658 | */ | |
659 | entry = ptep_clear_flush(vma, addr, ptep); | |
660 | /* | |
661 | * Check that no O_DIRECT or similar I/O is in progress on the | |
662 | * page | |
663 | */ | |
31e855ea | 664 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
31dbd01f IE |
665 | set_pte_at_notify(mm, addr, ptep, entry); |
666 | goto out_unlock; | |
667 | } | |
668 | entry = pte_wrprotect(entry); | |
669 | set_pte_at_notify(mm, addr, ptep, entry); | |
670 | } | |
671 | *orig_pte = *ptep; | |
672 | err = 0; | |
673 | ||
674 | out_unlock: | |
675 | pte_unmap_unlock(ptep, ptl); | |
676 | out: | |
677 | return err; | |
678 | } | |
679 | ||
680 | /** | |
681 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
682 | * @vma: vma that holds the pte pointing to page |
683 | * @page: the page we are replacing by kpage | |
684 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
685 | * @orig_pte: the original value of the pte |
686 | * | |
687 | * Returns 0 on success, -EFAULT on failure. | |
688 | */ | |
8dd3557a HD |
689 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
690 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
691 | { |
692 | struct mm_struct *mm = vma->vm_mm; | |
693 | pgd_t *pgd; | |
694 | pud_t *pud; | |
695 | pmd_t *pmd; | |
696 | pte_t *ptep; | |
697 | spinlock_t *ptl; | |
698 | unsigned long addr; | |
31dbd01f IE |
699 | int err = -EFAULT; |
700 | ||
8dd3557a | 701 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
702 | if (addr == -EFAULT) |
703 | goto out; | |
704 | ||
705 | pgd = pgd_offset(mm, addr); | |
706 | if (!pgd_present(*pgd)) | |
707 | goto out; | |
708 | ||
709 | pud = pud_offset(pgd, addr); | |
710 | if (!pud_present(*pud)) | |
711 | goto out; | |
712 | ||
713 | pmd = pmd_offset(pud, addr); | |
714 | if (!pmd_present(*pmd)) | |
715 | goto out; | |
716 | ||
717 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
718 | if (!pte_same(*ptep, orig_pte)) { | |
719 | pte_unmap_unlock(ptep, ptl); | |
720 | goto out; | |
721 | } | |
722 | ||
8dd3557a HD |
723 | get_page(kpage); |
724 | page_add_ksm_rmap(kpage); | |
31dbd01f IE |
725 | |
726 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
727 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 728 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 729 | |
8dd3557a HD |
730 | page_remove_rmap(page); |
731 | put_page(page); | |
31dbd01f IE |
732 | |
733 | pte_unmap_unlock(ptep, ptl); | |
734 | err = 0; | |
735 | out: | |
736 | return err; | |
737 | } | |
738 | ||
739 | /* | |
740 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
741 | * @vma: the vma that holds the pte pointing to page |
742 | * @page: the PageAnon page that we want to replace with kpage | |
743 | * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap | |
744 | * will make PageKsm) that we want to map instead of page | |
31dbd01f IE |
745 | * |
746 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
747 | */ | |
748 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 749 | struct page *page, struct page *kpage) |
31dbd01f IE |
750 | { |
751 | pte_t orig_pte = __pte(0); | |
752 | int err = -EFAULT; | |
753 | ||
754 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
755 | goto out; | |
8dd3557a | 756 | if (!PageAnon(page)) |
31dbd01f IE |
757 | goto out; |
758 | ||
31dbd01f IE |
759 | /* |
760 | * We need the page lock to read a stable PageSwapCache in | |
761 | * write_protect_page(). We use trylock_page() instead of | |
762 | * lock_page() because we don't want to wait here - we | |
763 | * prefer to continue scanning and merging different pages, | |
764 | * then come back to this page when it is unlocked. | |
765 | */ | |
8dd3557a | 766 | if (!trylock_page(page)) |
31e855ea | 767 | goto out; |
31dbd01f IE |
768 | /* |
769 | * If this anonymous page is mapped only here, its pte may need | |
770 | * to be write-protected. If it's mapped elsewhere, all of its | |
771 | * ptes are necessarily already write-protected. But in either | |
772 | * case, we need to lock and check page_count is not raised. | |
773 | */ | |
8dd3557a HD |
774 | if (write_protect_page(vma, page, &orig_pte) == 0 && |
775 | pages_identical(page, kpage)) | |
776 | err = replace_page(vma, page, kpage, orig_pte); | |
31dbd01f | 777 | |
8dd3557a | 778 | unlock_page(page); |
31dbd01f IE |
779 | out: |
780 | return err; | |
781 | } | |
782 | ||
81464e30 HD |
783 | /* |
784 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
785 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
786 | * |
787 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 788 | */ |
8dd3557a HD |
789 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
790 | struct page *page, struct page *kpage) | |
81464e30 | 791 | { |
8dd3557a | 792 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
793 | struct vm_area_struct *vma; |
794 | int err = -EFAULT; | |
795 | ||
8dd3557a HD |
796 | down_read(&mm->mmap_sem); |
797 | if (ksm_test_exit(mm)) | |
9ba69294 | 798 | goto out; |
8dd3557a HD |
799 | vma = find_vma(mm, rmap_item->address); |
800 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
801 | goto out; |
802 | ||
8dd3557a | 803 | err = try_to_merge_one_page(vma, page, kpage); |
81464e30 | 804 | out: |
8dd3557a | 805 | up_read(&mm->mmap_sem); |
81464e30 HD |
806 | return err; |
807 | } | |
808 | ||
31dbd01f IE |
809 | /* |
810 | * try_to_merge_two_pages - take two identical pages and prepare them | |
811 | * to be merged into one page. | |
812 | * | |
8dd3557a HD |
813 | * This function returns the kpage if we successfully merged two identical |
814 | * pages into one ksm page, NULL otherwise. | |
31dbd01f IE |
815 | * |
816 | * Note that this function allocates a new kernel page: if one of the pages | |
817 | * is already a ksm page, try_to_merge_with_ksm_page should be used. | |
818 | */ | |
8dd3557a HD |
819 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
820 | struct page *page, | |
821 | struct rmap_item *tree_rmap_item, | |
822 | struct page *tree_page) | |
31dbd01f | 823 | { |
8dd3557a | 824 | struct mm_struct *mm = rmap_item->mm; |
31dbd01f IE |
825 | struct vm_area_struct *vma; |
826 | struct page *kpage; | |
827 | int err = -EFAULT; | |
828 | ||
829 | /* | |
830 | * The number of nodes in the stable tree | |
831 | * is the number of kernel pages that we hold. | |
832 | */ | |
833 | if (ksm_max_kernel_pages && | |
b4028260 | 834 | ksm_max_kernel_pages <= ksm_pages_shared) |
8dd3557a | 835 | return NULL; |
31dbd01f IE |
836 | |
837 | kpage = alloc_page(GFP_HIGHUSER); | |
838 | if (!kpage) | |
8dd3557a | 839 | return NULL; |
31dbd01f | 840 | |
8dd3557a HD |
841 | down_read(&mm->mmap_sem); |
842 | if (ksm_test_exit(mm)) | |
843 | goto up; | |
844 | vma = find_vma(mm, rmap_item->address); | |
845 | if (!vma || vma->vm_start > rmap_item->address) | |
846 | goto up; | |
847 | ||
848 | copy_user_highpage(kpage, page, rmap_item->address, vma); | |
849 | err = try_to_merge_one_page(vma, page, kpage); | |
850 | up: | |
851 | up_read(&mm->mmap_sem); | |
31dbd01f IE |
852 | |
853 | if (!err) { | |
8dd3557a HD |
854 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
855 | tree_page, kpage); | |
31dbd01f | 856 | /* |
81464e30 HD |
857 | * If that fails, we have a ksm page with only one pte |
858 | * pointing to it: so break it. | |
31dbd01f IE |
859 | */ |
860 | if (err) | |
8dd3557a | 861 | break_cow(rmap_item); |
31dbd01f | 862 | } |
8dd3557a HD |
863 | if (err) { |
864 | put_page(kpage); | |
865 | kpage = NULL; | |
866 | } | |
867 | return kpage; | |
31dbd01f IE |
868 | } |
869 | ||
31dbd01f | 870 | /* |
8dd3557a | 871 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
872 | * |
873 | * This function checks if there is a page inside the stable tree | |
874 | * with identical content to the page that we are scanning right now. | |
875 | * | |
7b6ba2c7 | 876 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
877 | * NULL otherwise. |
878 | */ | |
7b6ba2c7 HD |
879 | static struct stable_node *stable_tree_search(struct page *page, |
880 | struct page **tree_pagep) | |
31dbd01f IE |
881 | { |
882 | struct rb_node *node = root_stable_tree.rb_node; | |
7b6ba2c7 | 883 | struct stable_node *stable_node; |
31dbd01f IE |
884 | |
885 | while (node) { | |
7b6ba2c7 HD |
886 | struct hlist_node *hlist, *hnext; |
887 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 888 | struct page *tree_page; |
31dbd01f IE |
889 | int ret; |
890 | ||
7b6ba2c7 HD |
891 | stable_node = rb_entry(node, struct stable_node, node); |
892 | hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, | |
893 | &stable_node->hlist, hlist) { | |
31dbd01f IE |
894 | BUG_ON(!in_stable_tree(tree_rmap_item)); |
895 | cond_resched(); | |
8dd3557a HD |
896 | tree_page = get_ksm_page(tree_rmap_item); |
897 | if (tree_page) | |
31dbd01f | 898 | break; |
31dbd01f | 899 | remove_rmap_item_from_tree(tree_rmap_item); |
31dbd01f | 900 | } |
7b6ba2c7 | 901 | if (!hlist) |
31dbd01f IE |
902 | return NULL; |
903 | ||
8dd3557a | 904 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
905 | |
906 | if (ret < 0) { | |
8dd3557a | 907 | put_page(tree_page); |
31dbd01f IE |
908 | node = node->rb_left; |
909 | } else if (ret > 0) { | |
8dd3557a | 910 | put_page(tree_page); |
31dbd01f IE |
911 | node = node->rb_right; |
912 | } else { | |
8dd3557a | 913 | *tree_pagep = tree_page; |
7b6ba2c7 | 914 | return stable_node; |
31dbd01f IE |
915 | } |
916 | } | |
917 | ||
918 | return NULL; | |
919 | } | |
920 | ||
921 | /* | |
922 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
923 | * into the stable tree. | |
924 | * | |
7b6ba2c7 HD |
925 | * This function returns the stable tree node just allocated on success, |
926 | * NULL otherwise. | |
31dbd01f | 927 | */ |
7b6ba2c7 | 928 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f IE |
929 | { |
930 | struct rb_node **new = &root_stable_tree.rb_node; | |
931 | struct rb_node *parent = NULL; | |
7b6ba2c7 | 932 | struct stable_node *stable_node; |
31dbd01f IE |
933 | |
934 | while (*new) { | |
7b6ba2c7 HD |
935 | struct hlist_node *hlist, *hnext; |
936 | struct rmap_item *tree_rmap_item; | |
31dbd01f IE |
937 | struct page *tree_page; |
938 | int ret; | |
939 | ||
7b6ba2c7 HD |
940 | stable_node = rb_entry(*new, struct stable_node, node); |
941 | hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, | |
942 | &stable_node->hlist, hlist) { | |
31dbd01f IE |
943 | BUG_ON(!in_stable_tree(tree_rmap_item)); |
944 | cond_resched(); | |
945 | tree_page = get_ksm_page(tree_rmap_item); | |
946 | if (tree_page) | |
947 | break; | |
31dbd01f | 948 | remove_rmap_item_from_tree(tree_rmap_item); |
31dbd01f | 949 | } |
7b6ba2c7 | 950 | if (!hlist) |
31dbd01f IE |
951 | return NULL; |
952 | ||
8dd3557a | 953 | ret = memcmp_pages(kpage, tree_page); |
31dbd01f IE |
954 | put_page(tree_page); |
955 | ||
956 | parent = *new; | |
957 | if (ret < 0) | |
958 | new = &parent->rb_left; | |
959 | else if (ret > 0) | |
960 | new = &parent->rb_right; | |
961 | else { | |
962 | /* | |
963 | * It is not a bug that stable_tree_search() didn't | |
964 | * find this node: because at that time our page was | |
965 | * not yet write-protected, so may have changed since. | |
966 | */ | |
967 | return NULL; | |
968 | } | |
969 | } | |
970 | ||
7b6ba2c7 HD |
971 | stable_node = alloc_stable_node(); |
972 | if (!stable_node) | |
973 | return NULL; | |
31dbd01f | 974 | |
7b6ba2c7 HD |
975 | rb_link_node(&stable_node->node, parent, new); |
976 | rb_insert_color(&stable_node->node, &root_stable_tree); | |
977 | ||
978 | INIT_HLIST_HEAD(&stable_node->hlist); | |
979 | ||
980 | return stable_node; | |
31dbd01f IE |
981 | } |
982 | ||
983 | /* | |
8dd3557a HD |
984 | * unstable_tree_search_insert - search for identical page, |
985 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
986 | * |
987 | * This function searches for a page in the unstable tree identical to the | |
988 | * page currently being scanned; and if no identical page is found in the | |
989 | * tree, we insert rmap_item as a new object into the unstable tree. | |
990 | * | |
991 | * This function returns pointer to rmap_item found to be identical | |
992 | * to the currently scanned page, NULL otherwise. | |
993 | * | |
994 | * This function does both searching and inserting, because they share | |
995 | * the same walking algorithm in an rbtree. | |
996 | */ | |
8dd3557a HD |
997 | static |
998 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
999 | struct page *page, | |
1000 | struct page **tree_pagep) | |
1001 | ||
31dbd01f IE |
1002 | { |
1003 | struct rb_node **new = &root_unstable_tree.rb_node; | |
1004 | struct rb_node *parent = NULL; | |
1005 | ||
1006 | while (*new) { | |
1007 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1008 | struct page *tree_page; |
31dbd01f IE |
1009 | int ret; |
1010 | ||
d178f27f | 1011 | cond_resched(); |
31dbd01f | 1012 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a HD |
1013 | tree_page = get_mergeable_page(tree_rmap_item); |
1014 | if (!tree_page) | |
31dbd01f IE |
1015 | return NULL; |
1016 | ||
1017 | /* | |
8dd3557a | 1018 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1019 | */ |
8dd3557a HD |
1020 | if (page == tree_page) { |
1021 | put_page(tree_page); | |
31dbd01f IE |
1022 | return NULL; |
1023 | } | |
1024 | ||
8dd3557a | 1025 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1026 | |
1027 | parent = *new; | |
1028 | if (ret < 0) { | |
8dd3557a | 1029 | put_page(tree_page); |
31dbd01f IE |
1030 | new = &parent->rb_left; |
1031 | } else if (ret > 0) { | |
8dd3557a | 1032 | put_page(tree_page); |
31dbd01f IE |
1033 | new = &parent->rb_right; |
1034 | } else { | |
8dd3557a | 1035 | *tree_pagep = tree_page; |
31dbd01f IE |
1036 | return tree_rmap_item; |
1037 | } | |
1038 | } | |
1039 | ||
7b6ba2c7 | 1040 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f IE |
1041 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
1042 | rb_link_node(&rmap_item->node, parent, new); | |
1043 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1044 | ||
473b0ce4 | 1045 | ksm_pages_unshared++; |
31dbd01f IE |
1046 | return NULL; |
1047 | } | |
1048 | ||
1049 | /* | |
1050 | * stable_tree_append - add another rmap_item to the linked list of | |
1051 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1052 | * the same ksm page. | |
1053 | */ | |
1054 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1055 | struct stable_node *stable_node) |
31dbd01f | 1056 | { |
7b6ba2c7 | 1057 | rmap_item->head = stable_node; |
31dbd01f | 1058 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1059 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1060 | |
7b6ba2c7 HD |
1061 | if (rmap_item->hlist.next) |
1062 | ksm_pages_sharing++; | |
1063 | else | |
1064 | ksm_pages_shared++; | |
31dbd01f IE |
1065 | } |
1066 | ||
1067 | /* | |
81464e30 HD |
1068 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1069 | * if not, compare checksum to previous and if it's the same, see if page can | |
1070 | * be inserted into the unstable tree, or merged with a page already there and | |
1071 | * both transferred to the stable tree. | |
31dbd01f IE |
1072 | * |
1073 | * @page: the page that we are searching identical page to. | |
1074 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1075 | */ | |
1076 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1077 | { | |
31dbd01f | 1078 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1079 | struct page *tree_page = NULL; |
7b6ba2c7 | 1080 | struct stable_node *stable_node; |
8dd3557a | 1081 | struct page *kpage; |
31dbd01f IE |
1082 | unsigned int checksum; |
1083 | int err; | |
1084 | ||
93d17715 | 1085 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1086 | |
1087 | /* We first start with searching the page inside the stable tree */ | |
7b6ba2c7 HD |
1088 | stable_node = stable_tree_search(page, &tree_page); |
1089 | if (stable_node) { | |
8dd3557a HD |
1090 | kpage = tree_page; |
1091 | if (page == kpage) /* forked */ | |
31dbd01f | 1092 | err = 0; |
e178dfde | 1093 | else |
8dd3557a HD |
1094 | err = try_to_merge_with_ksm_page(rmap_item, |
1095 | page, kpage); | |
31dbd01f IE |
1096 | if (!err) { |
1097 | /* | |
1098 | * The page was successfully merged: | |
1099 | * add its rmap_item to the stable tree. | |
1100 | */ | |
7b6ba2c7 | 1101 | stable_tree_append(rmap_item, stable_node); |
31dbd01f | 1102 | } |
8dd3557a | 1103 | put_page(kpage); |
31dbd01f IE |
1104 | return; |
1105 | } | |
1106 | ||
1107 | /* | |
1108 | * A ksm page might have got here by fork, but its other | |
1109 | * references have already been removed from the stable tree. | |
d952b791 HD |
1110 | * Or it might be left over from a break_ksm which failed |
1111 | * when the mem_cgroup had reached its limit: try again now. | |
31dbd01f IE |
1112 | */ |
1113 | if (PageKsm(page)) | |
8dd3557a | 1114 | break_cow(rmap_item); |
31dbd01f IE |
1115 | |
1116 | /* | |
1117 | * In case the hash value of the page was changed from the last time we | |
1118 | * have calculated it, this page to be changed frequely, therefore we | |
1119 | * don't want to insert it to the unstable tree, and we don't want to | |
1120 | * waste our time to search if there is something identical to it there. | |
1121 | */ | |
1122 | checksum = calc_checksum(page); | |
1123 | if (rmap_item->oldchecksum != checksum) { | |
1124 | rmap_item->oldchecksum = checksum; | |
1125 | return; | |
1126 | } | |
1127 | ||
8dd3557a HD |
1128 | tree_rmap_item = |
1129 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1130 | if (tree_rmap_item) { |
8dd3557a HD |
1131 | kpage = try_to_merge_two_pages(rmap_item, page, |
1132 | tree_rmap_item, tree_page); | |
1133 | put_page(tree_page); | |
31dbd01f IE |
1134 | /* |
1135 | * As soon as we merge this page, we want to remove the | |
1136 | * rmap_item of the page we have merged with from the unstable | |
1137 | * tree, and insert it instead as new node in the stable tree. | |
1138 | */ | |
8dd3557a | 1139 | if (kpage) { |
93d17715 | 1140 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1141 | |
7b6ba2c7 HD |
1142 | stable_node = stable_tree_insert(kpage); |
1143 | if (stable_node) { | |
1144 | stable_tree_append(tree_rmap_item, stable_node); | |
1145 | stable_tree_append(rmap_item, stable_node); | |
1146 | } | |
1147 | put_page(kpage); | |
1148 | ||
31dbd01f IE |
1149 | /* |
1150 | * If we fail to insert the page into the stable tree, | |
1151 | * we will have 2 virtual addresses that are pointing | |
1152 | * to a ksm page left outside the stable tree, | |
1153 | * in which case we need to break_cow on both. | |
1154 | */ | |
7b6ba2c7 | 1155 | if (!stable_node) { |
8dd3557a HD |
1156 | break_cow(tree_rmap_item); |
1157 | break_cow(rmap_item); | |
31dbd01f IE |
1158 | } |
1159 | } | |
31dbd01f IE |
1160 | } |
1161 | } | |
1162 | ||
1163 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1164 | struct rmap_item **rmap_list, |
31dbd01f IE |
1165 | unsigned long addr) |
1166 | { | |
1167 | struct rmap_item *rmap_item; | |
1168 | ||
6514d511 HD |
1169 | while (*rmap_list) { |
1170 | rmap_item = *rmap_list; | |
93d17715 | 1171 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1172 | return rmap_item; |
31dbd01f IE |
1173 | if (rmap_item->address > addr) |
1174 | break; | |
6514d511 | 1175 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1176 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1177 | free_rmap_item(rmap_item); |
1178 | } | |
1179 | ||
1180 | rmap_item = alloc_rmap_item(); | |
1181 | if (rmap_item) { | |
1182 | /* It has already been zeroed */ | |
1183 | rmap_item->mm = mm_slot->mm; | |
1184 | rmap_item->address = addr; | |
6514d511 HD |
1185 | rmap_item->rmap_list = *rmap_list; |
1186 | *rmap_list = rmap_item; | |
31dbd01f IE |
1187 | } |
1188 | return rmap_item; | |
1189 | } | |
1190 | ||
1191 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1192 | { | |
1193 | struct mm_struct *mm; | |
1194 | struct mm_slot *slot; | |
1195 | struct vm_area_struct *vma; | |
1196 | struct rmap_item *rmap_item; | |
1197 | ||
1198 | if (list_empty(&ksm_mm_head.mm_list)) | |
1199 | return NULL; | |
1200 | ||
1201 | slot = ksm_scan.mm_slot; | |
1202 | if (slot == &ksm_mm_head) { | |
1203 | root_unstable_tree = RB_ROOT; | |
1204 | ||
1205 | spin_lock(&ksm_mmlist_lock); | |
1206 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1207 | ksm_scan.mm_slot = slot; | |
1208 | spin_unlock(&ksm_mmlist_lock); | |
1209 | next_mm: | |
1210 | ksm_scan.address = 0; | |
6514d511 | 1211 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1212 | } |
1213 | ||
1214 | mm = slot->mm; | |
1215 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1216 | if (ksm_test_exit(mm)) |
1217 | vma = NULL; | |
1218 | else | |
1219 | vma = find_vma(mm, ksm_scan.address); | |
1220 | ||
1221 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1222 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1223 | continue; | |
1224 | if (ksm_scan.address < vma->vm_start) | |
1225 | ksm_scan.address = vma->vm_start; | |
1226 | if (!vma->anon_vma) | |
1227 | ksm_scan.address = vma->vm_end; | |
1228 | ||
1229 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1230 | if (ksm_test_exit(mm)) |
1231 | break; | |
31dbd01f IE |
1232 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
1233 | if (*page && PageAnon(*page)) { | |
1234 | flush_anon_page(vma, *page, ksm_scan.address); | |
1235 | flush_dcache_page(*page); | |
1236 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1237 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1238 | if (rmap_item) { |
6514d511 HD |
1239 | ksm_scan.rmap_list = |
1240 | &rmap_item->rmap_list; | |
31dbd01f IE |
1241 | ksm_scan.address += PAGE_SIZE; |
1242 | } else | |
1243 | put_page(*page); | |
1244 | up_read(&mm->mmap_sem); | |
1245 | return rmap_item; | |
1246 | } | |
1247 | if (*page) | |
1248 | put_page(*page); | |
1249 | ksm_scan.address += PAGE_SIZE; | |
1250 | cond_resched(); | |
1251 | } | |
1252 | } | |
1253 | ||
9ba69294 HD |
1254 | if (ksm_test_exit(mm)) { |
1255 | ksm_scan.address = 0; | |
6514d511 | 1256 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1257 | } |
31dbd01f IE |
1258 | /* |
1259 | * Nuke all the rmap_items that are above this current rmap: | |
1260 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1261 | */ | |
6514d511 | 1262 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1263 | |
1264 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1265 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1266 | struct mm_slot, mm_list); | |
1267 | if (ksm_scan.address == 0) { | |
1268 | /* | |
1269 | * We've completed a full scan of all vmas, holding mmap_sem | |
1270 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1271 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1272 | * This applies either when cleaning up after __ksm_exit |
1273 | * (but beware: we can reach here even before __ksm_exit), | |
1274 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1275 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1276 | */ |
1277 | hlist_del(&slot->link); | |
1278 | list_del(&slot->mm_list); | |
9ba69294 HD |
1279 | spin_unlock(&ksm_mmlist_lock); |
1280 | ||
cd551f97 HD |
1281 | free_mm_slot(slot); |
1282 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1283 | up_read(&mm->mmap_sem); |
1284 | mmdrop(mm); | |
1285 | } else { | |
1286 | spin_unlock(&ksm_mmlist_lock); | |
1287 | up_read(&mm->mmap_sem); | |
cd551f97 | 1288 | } |
31dbd01f IE |
1289 | |
1290 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1291 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1292 | if (slot != &ksm_mm_head) |
1293 | goto next_mm; | |
1294 | ||
31dbd01f IE |
1295 | ksm_scan.seqnr++; |
1296 | return NULL; | |
1297 | } | |
1298 | ||
1299 | /** | |
1300 | * ksm_do_scan - the ksm scanner main worker function. | |
1301 | * @scan_npages - number of pages we want to scan before we return. | |
1302 | */ | |
1303 | static void ksm_do_scan(unsigned int scan_npages) | |
1304 | { | |
1305 | struct rmap_item *rmap_item; | |
1306 | struct page *page; | |
1307 | ||
1308 | while (scan_npages--) { | |
1309 | cond_resched(); | |
1310 | rmap_item = scan_get_next_rmap_item(&page); | |
1311 | if (!rmap_item) | |
1312 | return; | |
1313 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1314 | cmp_and_merge_page(page, rmap_item); | |
26465d3e HD |
1315 | else if (page_mapcount(page) == 1) { |
1316 | /* | |
1317 | * Replace now-unshared ksm page by ordinary page. | |
1318 | */ | |
8dd3557a | 1319 | break_cow(rmap_item); |
26465d3e HD |
1320 | remove_rmap_item_from_tree(rmap_item); |
1321 | rmap_item->oldchecksum = calc_checksum(page); | |
1322 | } | |
31dbd01f IE |
1323 | put_page(page); |
1324 | } | |
1325 | } | |
1326 | ||
6e158384 HD |
1327 | static int ksmd_should_run(void) |
1328 | { | |
1329 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1330 | } | |
1331 | ||
31dbd01f IE |
1332 | static int ksm_scan_thread(void *nothing) |
1333 | { | |
339aa624 | 1334 | set_user_nice(current, 5); |
31dbd01f IE |
1335 | |
1336 | while (!kthread_should_stop()) { | |
6e158384 HD |
1337 | mutex_lock(&ksm_thread_mutex); |
1338 | if (ksmd_should_run()) | |
31dbd01f | 1339 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1340 | mutex_unlock(&ksm_thread_mutex); |
1341 | ||
1342 | if (ksmd_should_run()) { | |
31dbd01f IE |
1343 | schedule_timeout_interruptible( |
1344 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1345 | } else { | |
1346 | wait_event_interruptible(ksm_thread_wait, | |
6e158384 | 1347 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1348 | } |
1349 | } | |
1350 | return 0; | |
1351 | } | |
1352 | ||
f8af4da3 HD |
1353 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1354 | unsigned long end, int advice, unsigned long *vm_flags) | |
1355 | { | |
1356 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1357 | int err; |
f8af4da3 HD |
1358 | |
1359 | switch (advice) { | |
1360 | case MADV_MERGEABLE: | |
1361 | /* | |
1362 | * Be somewhat over-protective for now! | |
1363 | */ | |
1364 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1365 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1366 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
1367 | VM_MIXEDMAP | VM_SAO)) | |
1368 | return 0; /* just ignore the advice */ | |
1369 | ||
d952b791 HD |
1370 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1371 | err = __ksm_enter(mm); | |
1372 | if (err) | |
1373 | return err; | |
1374 | } | |
f8af4da3 HD |
1375 | |
1376 | *vm_flags |= VM_MERGEABLE; | |
1377 | break; | |
1378 | ||
1379 | case MADV_UNMERGEABLE: | |
1380 | if (!(*vm_flags & VM_MERGEABLE)) | |
1381 | return 0; /* just ignore the advice */ | |
1382 | ||
d952b791 HD |
1383 | if (vma->anon_vma) { |
1384 | err = unmerge_ksm_pages(vma, start, end); | |
1385 | if (err) | |
1386 | return err; | |
1387 | } | |
f8af4da3 HD |
1388 | |
1389 | *vm_flags &= ~VM_MERGEABLE; | |
1390 | break; | |
1391 | } | |
1392 | ||
1393 | return 0; | |
1394 | } | |
1395 | ||
1396 | int __ksm_enter(struct mm_struct *mm) | |
1397 | { | |
6e158384 HD |
1398 | struct mm_slot *mm_slot; |
1399 | int needs_wakeup; | |
1400 | ||
1401 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1402 | if (!mm_slot) |
1403 | return -ENOMEM; | |
1404 | ||
6e158384 HD |
1405 | /* Check ksm_run too? Would need tighter locking */ |
1406 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1407 | ||
31dbd01f IE |
1408 | spin_lock(&ksm_mmlist_lock); |
1409 | insert_to_mm_slots_hash(mm, mm_slot); | |
1410 | /* | |
1411 | * Insert just behind the scanning cursor, to let the area settle | |
1412 | * down a little; when fork is followed by immediate exec, we don't | |
1413 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1414 | */ | |
1415 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1416 | spin_unlock(&ksm_mmlist_lock); | |
1417 | ||
f8af4da3 | 1418 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1419 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1420 | |
1421 | if (needs_wakeup) | |
1422 | wake_up_interruptible(&ksm_thread_wait); | |
1423 | ||
f8af4da3 HD |
1424 | return 0; |
1425 | } | |
1426 | ||
1c2fb7a4 | 1427 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1428 | { |
cd551f97 | 1429 | struct mm_slot *mm_slot; |
9ba69294 | 1430 | int easy_to_free = 0; |
cd551f97 | 1431 | |
31dbd01f | 1432 | /* |
9ba69294 HD |
1433 | * This process is exiting: if it's straightforward (as is the |
1434 | * case when ksmd was never running), free mm_slot immediately. | |
1435 | * But if it's at the cursor or has rmap_items linked to it, use | |
1436 | * mmap_sem to synchronize with any break_cows before pagetables | |
1437 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1438 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1439 | */ |
9ba69294 | 1440 | |
cd551f97 HD |
1441 | spin_lock(&ksm_mmlist_lock); |
1442 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1443 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1444 | if (!mm_slot->rmap_list) { |
9ba69294 HD |
1445 | hlist_del(&mm_slot->link); |
1446 | list_del(&mm_slot->mm_list); | |
1447 | easy_to_free = 1; | |
1448 | } else { | |
1449 | list_move(&mm_slot->mm_list, | |
1450 | &ksm_scan.mm_slot->mm_list); | |
1451 | } | |
cd551f97 | 1452 | } |
cd551f97 HD |
1453 | spin_unlock(&ksm_mmlist_lock); |
1454 | ||
9ba69294 HD |
1455 | if (easy_to_free) { |
1456 | free_mm_slot(mm_slot); | |
1457 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1458 | mmdrop(mm); | |
1459 | } else if (mm_slot) { | |
9ba69294 HD |
1460 | down_write(&mm->mmap_sem); |
1461 | up_write(&mm->mmap_sem); | |
9ba69294 | 1462 | } |
31dbd01f IE |
1463 | } |
1464 | ||
2ffd8679 HD |
1465 | #ifdef CONFIG_SYSFS |
1466 | /* | |
1467 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1468 | */ | |
1469 | ||
31dbd01f IE |
1470 | #define KSM_ATTR_RO(_name) \ |
1471 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1472 | #define KSM_ATTR(_name) \ | |
1473 | static struct kobj_attribute _name##_attr = \ | |
1474 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1475 | ||
1476 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1477 | struct kobj_attribute *attr, char *buf) | |
1478 | { | |
1479 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1480 | } | |
1481 | ||
1482 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1483 | struct kobj_attribute *attr, | |
1484 | const char *buf, size_t count) | |
1485 | { | |
1486 | unsigned long msecs; | |
1487 | int err; | |
1488 | ||
1489 | err = strict_strtoul(buf, 10, &msecs); | |
1490 | if (err || msecs > UINT_MAX) | |
1491 | return -EINVAL; | |
1492 | ||
1493 | ksm_thread_sleep_millisecs = msecs; | |
1494 | ||
1495 | return count; | |
1496 | } | |
1497 | KSM_ATTR(sleep_millisecs); | |
1498 | ||
1499 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1500 | struct kobj_attribute *attr, char *buf) | |
1501 | { | |
1502 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1503 | } | |
1504 | ||
1505 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1506 | struct kobj_attribute *attr, | |
1507 | const char *buf, size_t count) | |
1508 | { | |
1509 | int err; | |
1510 | unsigned long nr_pages; | |
1511 | ||
1512 | err = strict_strtoul(buf, 10, &nr_pages); | |
1513 | if (err || nr_pages > UINT_MAX) | |
1514 | return -EINVAL; | |
1515 | ||
1516 | ksm_thread_pages_to_scan = nr_pages; | |
1517 | ||
1518 | return count; | |
1519 | } | |
1520 | KSM_ATTR(pages_to_scan); | |
1521 | ||
1522 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1523 | char *buf) | |
1524 | { | |
1525 | return sprintf(buf, "%u\n", ksm_run); | |
1526 | } | |
1527 | ||
1528 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1529 | const char *buf, size_t count) | |
1530 | { | |
1531 | int err; | |
1532 | unsigned long flags; | |
1533 | ||
1534 | err = strict_strtoul(buf, 10, &flags); | |
1535 | if (err || flags > UINT_MAX) | |
1536 | return -EINVAL; | |
1537 | if (flags > KSM_RUN_UNMERGE) | |
1538 | return -EINVAL; | |
1539 | ||
1540 | /* | |
1541 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1542 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
b4028260 | 1543 | * breaking COW to free the unswappable pages_shared (but leaves |
31dbd01f IE |
1544 | * mm_slots on the list for when ksmd may be set running again). |
1545 | */ | |
1546 | ||
1547 | mutex_lock(&ksm_thread_mutex); | |
1548 | if (ksm_run != flags) { | |
1549 | ksm_run = flags; | |
d952b791 | 1550 | if (flags & KSM_RUN_UNMERGE) { |
35451bee | 1551 | current->flags |= PF_OOM_ORIGIN; |
d952b791 | 1552 | err = unmerge_and_remove_all_rmap_items(); |
35451bee | 1553 | current->flags &= ~PF_OOM_ORIGIN; |
d952b791 HD |
1554 | if (err) { |
1555 | ksm_run = KSM_RUN_STOP; | |
1556 | count = err; | |
1557 | } | |
1558 | } | |
31dbd01f IE |
1559 | } |
1560 | mutex_unlock(&ksm_thread_mutex); | |
1561 | ||
1562 | if (flags & KSM_RUN_MERGE) | |
1563 | wake_up_interruptible(&ksm_thread_wait); | |
1564 | ||
1565 | return count; | |
1566 | } | |
1567 | KSM_ATTR(run); | |
1568 | ||
31dbd01f IE |
1569 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
1570 | struct kobj_attribute *attr, | |
1571 | const char *buf, size_t count) | |
1572 | { | |
1573 | int err; | |
1574 | unsigned long nr_pages; | |
1575 | ||
1576 | err = strict_strtoul(buf, 10, &nr_pages); | |
1577 | if (err) | |
1578 | return -EINVAL; | |
1579 | ||
1580 | ksm_max_kernel_pages = nr_pages; | |
1581 | ||
1582 | return count; | |
1583 | } | |
1584 | ||
1585 | static ssize_t max_kernel_pages_show(struct kobject *kobj, | |
1586 | struct kobj_attribute *attr, char *buf) | |
1587 | { | |
1588 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); | |
1589 | } | |
1590 | KSM_ATTR(max_kernel_pages); | |
1591 | ||
b4028260 HD |
1592 | static ssize_t pages_shared_show(struct kobject *kobj, |
1593 | struct kobj_attribute *attr, char *buf) | |
1594 | { | |
1595 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1596 | } | |
1597 | KSM_ATTR_RO(pages_shared); | |
1598 | ||
1599 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1600 | struct kobj_attribute *attr, char *buf) | |
1601 | { | |
e178dfde | 1602 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1603 | } |
1604 | KSM_ATTR_RO(pages_sharing); | |
1605 | ||
473b0ce4 HD |
1606 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1607 | struct kobj_attribute *attr, char *buf) | |
1608 | { | |
1609 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1610 | } | |
1611 | KSM_ATTR_RO(pages_unshared); | |
1612 | ||
1613 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1614 | struct kobj_attribute *attr, char *buf) | |
1615 | { | |
1616 | long ksm_pages_volatile; | |
1617 | ||
1618 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1619 | - ksm_pages_sharing - ksm_pages_unshared; | |
1620 | /* | |
1621 | * It was not worth any locking to calculate that statistic, | |
1622 | * but it might therefore sometimes be negative: conceal that. | |
1623 | */ | |
1624 | if (ksm_pages_volatile < 0) | |
1625 | ksm_pages_volatile = 0; | |
1626 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1627 | } | |
1628 | KSM_ATTR_RO(pages_volatile); | |
1629 | ||
1630 | static ssize_t full_scans_show(struct kobject *kobj, | |
1631 | struct kobj_attribute *attr, char *buf) | |
1632 | { | |
1633 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1634 | } | |
1635 | KSM_ATTR_RO(full_scans); | |
1636 | ||
31dbd01f IE |
1637 | static struct attribute *ksm_attrs[] = { |
1638 | &sleep_millisecs_attr.attr, | |
1639 | &pages_to_scan_attr.attr, | |
1640 | &run_attr.attr, | |
31dbd01f | 1641 | &max_kernel_pages_attr.attr, |
b4028260 HD |
1642 | &pages_shared_attr.attr, |
1643 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1644 | &pages_unshared_attr.attr, |
1645 | &pages_volatile_attr.attr, | |
1646 | &full_scans_attr.attr, | |
31dbd01f IE |
1647 | NULL, |
1648 | }; | |
1649 | ||
1650 | static struct attribute_group ksm_attr_group = { | |
1651 | .attrs = ksm_attrs, | |
1652 | .name = "ksm", | |
1653 | }; | |
2ffd8679 | 1654 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1655 | |
1656 | static int __init ksm_init(void) | |
1657 | { | |
1658 | struct task_struct *ksm_thread; | |
1659 | int err; | |
1660 | ||
c73602ad | 1661 | ksm_max_kernel_pages = totalram_pages / 4; |
2c6854fd | 1662 | |
31dbd01f IE |
1663 | err = ksm_slab_init(); |
1664 | if (err) | |
1665 | goto out; | |
1666 | ||
1667 | err = mm_slots_hash_init(); | |
1668 | if (err) | |
1669 | goto out_free1; | |
1670 | ||
1671 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); | |
1672 | if (IS_ERR(ksm_thread)) { | |
1673 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
1674 | err = PTR_ERR(ksm_thread); | |
1675 | goto out_free2; | |
1676 | } | |
1677 | ||
2ffd8679 | 1678 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
1679 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
1680 | if (err) { | |
1681 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 HD |
1682 | kthread_stop(ksm_thread); |
1683 | goto out_free2; | |
31dbd01f | 1684 | } |
c73602ad HD |
1685 | #else |
1686 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
1687 | ||
2ffd8679 | 1688 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1689 | |
1690 | return 0; | |
1691 | ||
31dbd01f IE |
1692 | out_free2: |
1693 | mm_slots_hash_free(); | |
1694 | out_free1: | |
1695 | ksm_slab_free(); | |
1696 | out: | |
1697 | return err; | |
f8af4da3 | 1698 | } |
31dbd01f | 1699 | module_init(ksm_init) |