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 | 36 | #include <asm/tlbflush.h> |
73848b46 | 37 | #include "internal.h" |
31dbd01f IE |
38 | |
39 | /* | |
40 | * A few notes about the KSM scanning process, | |
41 | * to make it easier to understand the data structures below: | |
42 | * | |
43 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
44 | * contents into a data structure that holds pointers to the pages' locations. | |
45 | * | |
46 | * Since the contents of the pages may change at any moment, KSM cannot just | |
47 | * insert the pages into a normal sorted tree and expect it to find anything. | |
48 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
49 | * | |
50 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
51 | * by their contents. Because each such page is write-protected, searching on | |
52 | * this tree is fully assured to be working (except when pages are unmapped), | |
53 | * and therefore this tree is called the stable tree. | |
54 | * | |
55 | * In addition to the stable tree, KSM uses a second data structure called the | |
56 | * unstable tree: this tree holds pointers to pages which have been found to | |
57 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
58 | * by their contents, but since they are not write-protected, KSM cannot rely | |
59 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
60 | * be corrupted as its contents are modified, and so it is called unstable. | |
61 | * | |
62 | * KSM solves this problem by several techniques: | |
63 | * | |
64 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
65 | * memory areas, and then the tree is rebuilt again from the beginning. | |
66 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
67 | * has not changed since the previous scan of all memory areas. | |
68 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
69 | * colors of the nodes and not on their contents, assuring that even when | |
70 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
71 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
72 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
73 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
74 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
75 | * it is secured in the stable tree. (When we scan a new page, we first | |
76 | * compare it against the stable tree, and then against the unstable tree.) | |
77 | */ | |
78 | ||
79 | /** | |
80 | * struct mm_slot - ksm information per mm that is being scanned | |
81 | * @link: link to the mm_slots hash list | |
82 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 83 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
84 | * @mm: the mm that this information is valid for |
85 | */ | |
86 | struct mm_slot { | |
87 | struct hlist_node link; | |
88 | struct list_head mm_list; | |
6514d511 | 89 | struct rmap_item *rmap_list; |
31dbd01f IE |
90 | struct mm_struct *mm; |
91 | }; | |
92 | ||
93 | /** | |
94 | * struct ksm_scan - cursor for scanning | |
95 | * @mm_slot: the current mm_slot we are scanning | |
96 | * @address: the next address inside that to be scanned | |
6514d511 | 97 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
98 | * @seqnr: count of completed full scans (needed when removing unstable node) |
99 | * | |
100 | * There is only the one ksm_scan instance of this cursor structure. | |
101 | */ | |
102 | struct ksm_scan { | |
103 | struct mm_slot *mm_slot; | |
104 | unsigned long address; | |
6514d511 | 105 | struct rmap_item **rmap_list; |
31dbd01f IE |
106 | unsigned long seqnr; |
107 | }; | |
108 | ||
7b6ba2c7 HD |
109 | /** |
110 | * struct stable_node - node of the stable rbtree | |
08beca44 | 111 | * @page: pointer to struct page of the ksm page |
7b6ba2c7 HD |
112 | * @node: rb node of this ksm page in the stable tree |
113 | * @hlist: hlist head of rmap_items using this ksm page | |
114 | */ | |
115 | struct stable_node { | |
08beca44 | 116 | struct page *page; |
7b6ba2c7 HD |
117 | struct rb_node node; |
118 | struct hlist_head hlist; | |
119 | }; | |
120 | ||
31dbd01f IE |
121 | /** |
122 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 HD |
123 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
124 | * @filler: unused space we're making available in this patch | |
31dbd01f IE |
125 | * @mm: the memory structure this rmap_item is pointing into |
126 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
127 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
128 | * @node: rb node of this rmap_item in the unstable tree |
129 | * @head: pointer to stable_node heading this list in the stable tree | |
130 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
131 | */ |
132 | struct rmap_item { | |
6514d511 HD |
133 | struct rmap_item *rmap_list; |
134 | unsigned long filler; | |
31dbd01f IE |
135 | struct mm_struct *mm; |
136 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 137 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 138 | union { |
7b6ba2c7 HD |
139 | struct rb_node node; /* when node of unstable tree */ |
140 | struct { /* when listed from stable tree */ | |
141 | struct stable_node *head; | |
142 | struct hlist_node hlist; | |
143 | }; | |
31dbd01f IE |
144 | }; |
145 | }; | |
146 | ||
147 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
148 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
149 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
150 | |
151 | /* The stable and unstable tree heads */ | |
152 | static struct rb_root root_stable_tree = RB_ROOT; | |
153 | static struct rb_root root_unstable_tree = RB_ROOT; | |
154 | ||
155 | #define MM_SLOTS_HASH_HEADS 1024 | |
156 | static struct hlist_head *mm_slots_hash; | |
157 | ||
158 | static struct mm_slot ksm_mm_head = { | |
159 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
160 | }; | |
161 | static struct ksm_scan ksm_scan = { | |
162 | .mm_slot = &ksm_mm_head, | |
163 | }; | |
164 | ||
165 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 166 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
167 | static struct kmem_cache *mm_slot_cache; |
168 | ||
169 | /* The number of nodes in the stable tree */ | |
b4028260 | 170 | static unsigned long ksm_pages_shared; |
31dbd01f | 171 | |
e178dfde | 172 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 173 | static unsigned long ksm_pages_sharing; |
31dbd01f | 174 | |
473b0ce4 HD |
175 | /* The number of nodes in the unstable tree */ |
176 | static unsigned long ksm_pages_unshared; | |
177 | ||
178 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
179 | static unsigned long ksm_rmap_items; | |
180 | ||
31dbd01f | 181 | /* Limit on the number of unswappable pages used */ |
2c6854fd | 182 | static unsigned long ksm_max_kernel_pages; |
31dbd01f IE |
183 | |
184 | /* Number of pages ksmd should scan in one batch */ | |
2c6854fd | 185 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
186 | |
187 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 188 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
189 | |
190 | #define KSM_RUN_STOP 0 | |
191 | #define KSM_RUN_MERGE 1 | |
192 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 193 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
194 | |
195 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
196 | static DEFINE_MUTEX(ksm_thread_mutex); | |
197 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
198 | ||
199 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
200 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
201 | (__flags), NULL) | |
202 | ||
203 | static int __init ksm_slab_init(void) | |
204 | { | |
205 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
206 | if (!rmap_item_cache) | |
207 | goto out; | |
208 | ||
7b6ba2c7 HD |
209 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
210 | if (!stable_node_cache) | |
211 | goto out_free1; | |
212 | ||
31dbd01f IE |
213 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
214 | if (!mm_slot_cache) | |
7b6ba2c7 | 215 | goto out_free2; |
31dbd01f IE |
216 | |
217 | return 0; | |
218 | ||
7b6ba2c7 HD |
219 | out_free2: |
220 | kmem_cache_destroy(stable_node_cache); | |
221 | out_free1: | |
31dbd01f IE |
222 | kmem_cache_destroy(rmap_item_cache); |
223 | out: | |
224 | return -ENOMEM; | |
225 | } | |
226 | ||
227 | static void __init ksm_slab_free(void) | |
228 | { | |
229 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 230 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
231 | kmem_cache_destroy(rmap_item_cache); |
232 | mm_slot_cache = NULL; | |
233 | } | |
234 | ||
235 | static inline struct rmap_item *alloc_rmap_item(void) | |
236 | { | |
473b0ce4 HD |
237 | struct rmap_item *rmap_item; |
238 | ||
239 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
240 | if (rmap_item) | |
241 | ksm_rmap_items++; | |
242 | return rmap_item; | |
31dbd01f IE |
243 | } |
244 | ||
245 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
246 | { | |
473b0ce4 | 247 | ksm_rmap_items--; |
31dbd01f IE |
248 | rmap_item->mm = NULL; /* debug safety */ |
249 | kmem_cache_free(rmap_item_cache, rmap_item); | |
250 | } | |
251 | ||
7b6ba2c7 HD |
252 | static inline struct stable_node *alloc_stable_node(void) |
253 | { | |
254 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
255 | } | |
256 | ||
257 | static inline void free_stable_node(struct stable_node *stable_node) | |
258 | { | |
259 | kmem_cache_free(stable_node_cache, stable_node); | |
260 | } | |
261 | ||
31dbd01f IE |
262 | static inline struct mm_slot *alloc_mm_slot(void) |
263 | { | |
264 | if (!mm_slot_cache) /* initialization failed */ | |
265 | return NULL; | |
266 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
267 | } | |
268 | ||
269 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
270 | { | |
271 | kmem_cache_free(mm_slot_cache, mm_slot); | |
272 | } | |
273 | ||
274 | static int __init mm_slots_hash_init(void) | |
275 | { | |
276 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), | |
277 | GFP_KERNEL); | |
278 | if (!mm_slots_hash) | |
279 | return -ENOMEM; | |
280 | return 0; | |
281 | } | |
282 | ||
283 | static void __init mm_slots_hash_free(void) | |
284 | { | |
285 | kfree(mm_slots_hash); | |
286 | } | |
287 | ||
288 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
289 | { | |
290 | struct mm_slot *mm_slot; | |
291 | struct hlist_head *bucket; | |
292 | struct hlist_node *node; | |
293 | ||
294 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
295 | % MM_SLOTS_HASH_HEADS]; | |
296 | hlist_for_each_entry(mm_slot, node, bucket, link) { | |
297 | if (mm == mm_slot->mm) | |
298 | return mm_slot; | |
299 | } | |
300 | return NULL; | |
301 | } | |
302 | ||
303 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
304 | struct mm_slot *mm_slot) | |
305 | { | |
306 | struct hlist_head *bucket; | |
307 | ||
308 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
309 | % MM_SLOTS_HASH_HEADS]; | |
310 | mm_slot->mm = mm; | |
31dbd01f IE |
311 | hlist_add_head(&mm_slot->link, bucket); |
312 | } | |
313 | ||
314 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
315 | { | |
316 | return rmap_item->address & STABLE_FLAG; | |
317 | } | |
318 | ||
a913e182 HD |
319 | /* |
320 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
321 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
322 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
323 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
324 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
325 | * places for correctness, in some places just to avoid unnecessary work. | |
326 | */ | |
327 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
328 | { | |
329 | return atomic_read(&mm->mm_users) == 0; | |
330 | } | |
331 | ||
31dbd01f IE |
332 | /* |
333 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
334 | * | |
335 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
336 | * put_page(page); | |
337 | * | |
338 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
339 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
340 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
341 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
342 | */ | |
d952b791 | 343 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
344 | { |
345 | struct page *page; | |
d952b791 | 346 | int ret = 0; |
31dbd01f IE |
347 | |
348 | do { | |
349 | cond_resched(); | |
350 | page = follow_page(vma, addr, FOLL_GET); | |
351 | if (!page) | |
352 | break; | |
353 | if (PageKsm(page)) | |
354 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
355 | FAULT_FLAG_WRITE); | |
356 | else | |
357 | ret = VM_FAULT_WRITE; | |
358 | put_page(page); | |
d952b791 HD |
359 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
360 | /* | |
361 | * We must loop because handle_mm_fault() may back out if there's | |
362 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
363 | * | |
364 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
365 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
366 | * but note that a concurrent fault might break PageKsm for us. | |
367 | * | |
368 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
369 | * backing file, which also invalidates anonymous pages: that's | |
370 | * okay, that truncation will have unmapped the PageKsm for us. | |
371 | * | |
372 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
373 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
374 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
375 | * to user; and ksmd, having no mm, would never be chosen for that. | |
376 | * | |
377 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
378 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
379 | * even ksmd can fail in this way - though it's usually breaking ksm | |
380 | * just to undo a merge it made a moment before, so unlikely to oom. | |
381 | * | |
382 | * That's a pity: we might therefore have more kernel pages allocated | |
383 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
384 | * will retry to break_cow on each pass, so should recover the page | |
385 | * in due course. The important thing is to not let VM_MERGEABLE | |
386 | * be cleared while any such pages might remain in the area. | |
387 | */ | |
388 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
389 | } |
390 | ||
8dd3557a | 391 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 392 | { |
8dd3557a HD |
393 | struct mm_struct *mm = rmap_item->mm; |
394 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
395 | struct vm_area_struct *vma; |
396 | ||
81464e30 | 397 | down_read(&mm->mmap_sem); |
9ba69294 HD |
398 | if (ksm_test_exit(mm)) |
399 | goto out; | |
31dbd01f IE |
400 | vma = find_vma(mm, addr); |
401 | if (!vma || vma->vm_start > addr) | |
81464e30 | 402 | goto out; |
31dbd01f | 403 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 404 | goto out; |
31dbd01f | 405 | break_ksm(vma, addr); |
81464e30 | 406 | out: |
31dbd01f IE |
407 | up_read(&mm->mmap_sem); |
408 | } | |
409 | ||
410 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
411 | { | |
412 | struct mm_struct *mm = rmap_item->mm; | |
413 | unsigned long addr = rmap_item->address; | |
414 | struct vm_area_struct *vma; | |
415 | struct page *page; | |
416 | ||
417 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
418 | if (ksm_test_exit(mm)) |
419 | goto out; | |
31dbd01f IE |
420 | vma = find_vma(mm, addr); |
421 | if (!vma || vma->vm_start > addr) | |
422 | goto out; | |
423 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
424 | goto out; | |
425 | ||
426 | page = follow_page(vma, addr, FOLL_GET); | |
427 | if (!page) | |
428 | goto out; | |
429 | if (PageAnon(page)) { | |
430 | flush_anon_page(vma, page, addr); | |
431 | flush_dcache_page(page); | |
432 | } else { | |
433 | put_page(page); | |
434 | out: page = NULL; | |
435 | } | |
436 | up_read(&mm->mmap_sem); | |
437 | return page; | |
438 | } | |
439 | ||
31dbd01f IE |
440 | /* |
441 | * Removing rmap_item from stable or unstable tree. | |
442 | * This function will clean the information from the stable/unstable tree. | |
443 | */ | |
444 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
445 | { | |
7b6ba2c7 HD |
446 | if (rmap_item->address & STABLE_FLAG) { |
447 | struct stable_node *stable_node; | |
31dbd01f | 448 | |
7b6ba2c7 HD |
449 | stable_node = rmap_item->head; |
450 | hlist_del(&rmap_item->hlist); | |
451 | if (stable_node->hlist.first) | |
e178dfde | 452 | ksm_pages_sharing--; |
7b6ba2c7 | 453 | else { |
08beca44 HD |
454 | set_page_stable_node(stable_node->page, NULL); |
455 | put_page(stable_node->page); | |
456 | ||
7b6ba2c7 HD |
457 | rb_erase(&stable_node->node, &root_stable_tree); |
458 | free_stable_node(stable_node); | |
459 | ksm_pages_shared--; | |
31dbd01f IE |
460 | } |
461 | ||
93d17715 | 462 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 463 | |
7b6ba2c7 | 464 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
465 | unsigned char age; |
466 | /* | |
9ba69294 | 467 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 468 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
469 | * But be careful when an mm is exiting: do the rb_erase |
470 | * if this rmap_item was inserted by this scan, rather | |
471 | * than left over from before. | |
31dbd01f IE |
472 | */ |
473 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 474 | BUG_ON(age > 1); |
31dbd01f IE |
475 | if (!age) |
476 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
93d17715 | 477 | |
473b0ce4 | 478 | ksm_pages_unshared--; |
93d17715 | 479 | rmap_item->address &= PAGE_MASK; |
31dbd01f IE |
480 | } |
481 | ||
31dbd01f IE |
482 | cond_resched(); /* we're called from many long loops */ |
483 | } | |
484 | ||
31dbd01f | 485 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 486 | struct rmap_item **rmap_list) |
31dbd01f | 487 | { |
6514d511 HD |
488 | while (*rmap_list) { |
489 | struct rmap_item *rmap_item = *rmap_list; | |
490 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 491 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
492 | free_rmap_item(rmap_item); |
493 | } | |
494 | } | |
495 | ||
496 | /* | |
497 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather | |
498 | * than check every pte of a given vma, the locking doesn't quite work for | |
499 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
500 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
501 | * rmap_items from parent to child at fork time (so as not to waste time | |
502 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
503 | * |
504 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
505 | * and freeing memory) when unmerging an area, it's easier to leave that | |
506 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
507 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 508 | */ |
d952b791 HD |
509 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
510 | unsigned long start, unsigned long end) | |
31dbd01f IE |
511 | { |
512 | unsigned long addr; | |
d952b791 | 513 | int err = 0; |
31dbd01f | 514 | |
d952b791 | 515 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
516 | if (ksm_test_exit(vma->vm_mm)) |
517 | break; | |
d952b791 HD |
518 | if (signal_pending(current)) |
519 | err = -ERESTARTSYS; | |
520 | else | |
521 | err = break_ksm(vma, addr); | |
522 | } | |
523 | return err; | |
31dbd01f IE |
524 | } |
525 | ||
2ffd8679 HD |
526 | #ifdef CONFIG_SYSFS |
527 | /* | |
528 | * Only called through the sysfs control interface: | |
529 | */ | |
d952b791 | 530 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
531 | { |
532 | struct mm_slot *mm_slot; | |
533 | struct mm_struct *mm; | |
534 | struct vm_area_struct *vma; | |
d952b791 HD |
535 | int err = 0; |
536 | ||
537 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 538 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
539 | struct mm_slot, mm_list); |
540 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 541 | |
9ba69294 HD |
542 | for (mm_slot = ksm_scan.mm_slot; |
543 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
544 | mm = mm_slot->mm; |
545 | down_read(&mm->mmap_sem); | |
546 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
547 | if (ksm_test_exit(mm)) |
548 | break; | |
31dbd01f IE |
549 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
550 | continue; | |
d952b791 HD |
551 | err = unmerge_ksm_pages(vma, |
552 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
553 | if (err) |
554 | goto error; | |
31dbd01f | 555 | } |
9ba69294 | 556 | |
6514d511 | 557 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
558 | |
559 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 560 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 561 | struct mm_slot, mm_list); |
9ba69294 HD |
562 | if (ksm_test_exit(mm)) { |
563 | hlist_del(&mm_slot->link); | |
564 | list_del(&mm_slot->mm_list); | |
565 | spin_unlock(&ksm_mmlist_lock); | |
566 | ||
567 | free_mm_slot(mm_slot); | |
568 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
569 | up_read(&mm->mmap_sem); | |
570 | mmdrop(mm); | |
571 | } else { | |
572 | spin_unlock(&ksm_mmlist_lock); | |
573 | up_read(&mm->mmap_sem); | |
574 | } | |
31dbd01f IE |
575 | } |
576 | ||
d952b791 | 577 | ksm_scan.seqnr = 0; |
9ba69294 HD |
578 | return 0; |
579 | ||
580 | error: | |
581 | up_read(&mm->mmap_sem); | |
31dbd01f | 582 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 583 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 584 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 585 | return err; |
31dbd01f | 586 | } |
2ffd8679 | 587 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 588 | |
31dbd01f IE |
589 | static u32 calc_checksum(struct page *page) |
590 | { | |
591 | u32 checksum; | |
592 | void *addr = kmap_atomic(page, KM_USER0); | |
593 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); | |
594 | kunmap_atomic(addr, KM_USER0); | |
595 | return checksum; | |
596 | } | |
597 | ||
598 | static int memcmp_pages(struct page *page1, struct page *page2) | |
599 | { | |
600 | char *addr1, *addr2; | |
601 | int ret; | |
602 | ||
603 | addr1 = kmap_atomic(page1, KM_USER0); | |
604 | addr2 = kmap_atomic(page2, KM_USER1); | |
605 | ret = memcmp(addr1, addr2, PAGE_SIZE); | |
606 | kunmap_atomic(addr2, KM_USER1); | |
607 | kunmap_atomic(addr1, KM_USER0); | |
608 | return ret; | |
609 | } | |
610 | ||
611 | static inline int pages_identical(struct page *page1, struct page *page2) | |
612 | { | |
613 | return !memcmp_pages(page1, page2); | |
614 | } | |
615 | ||
616 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
617 | pte_t *orig_pte) | |
618 | { | |
619 | struct mm_struct *mm = vma->vm_mm; | |
620 | unsigned long addr; | |
621 | pte_t *ptep; | |
622 | spinlock_t *ptl; | |
623 | int swapped; | |
624 | int err = -EFAULT; | |
625 | ||
626 | addr = page_address_in_vma(page, vma); | |
627 | if (addr == -EFAULT) | |
628 | goto out; | |
629 | ||
630 | ptep = page_check_address(page, mm, addr, &ptl, 0); | |
631 | if (!ptep) | |
632 | goto out; | |
633 | ||
634 | if (pte_write(*ptep)) { | |
635 | pte_t entry; | |
636 | ||
637 | swapped = PageSwapCache(page); | |
638 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
639 | /* | |
640 | * Ok this is tricky, when get_user_pages_fast() run it doesnt | |
641 | * take any lock, therefore the check that we are going to make | |
642 | * with the pagecount against the mapcount is racey and | |
643 | * O_DIRECT can happen right after the check. | |
644 | * So we clear the pte and flush the tlb before the check | |
645 | * this assure us that no O_DIRECT can happen after the check | |
646 | * or in the middle of the check. | |
647 | */ | |
648 | entry = ptep_clear_flush(vma, addr, ptep); | |
649 | /* | |
650 | * Check that no O_DIRECT or similar I/O is in progress on the | |
651 | * page | |
652 | */ | |
31e855ea | 653 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
31dbd01f IE |
654 | set_pte_at_notify(mm, addr, ptep, entry); |
655 | goto out_unlock; | |
656 | } | |
657 | entry = pte_wrprotect(entry); | |
658 | set_pte_at_notify(mm, addr, ptep, entry); | |
659 | } | |
660 | *orig_pte = *ptep; | |
661 | err = 0; | |
662 | ||
663 | out_unlock: | |
664 | pte_unmap_unlock(ptep, ptl); | |
665 | out: | |
666 | return err; | |
667 | } | |
668 | ||
669 | /** | |
670 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
671 | * @vma: vma that holds the pte pointing to page |
672 | * @page: the page we are replacing by kpage | |
673 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
674 | * @orig_pte: the original value of the pte |
675 | * | |
676 | * Returns 0 on success, -EFAULT on failure. | |
677 | */ | |
8dd3557a HD |
678 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
679 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
680 | { |
681 | struct mm_struct *mm = vma->vm_mm; | |
682 | pgd_t *pgd; | |
683 | pud_t *pud; | |
684 | pmd_t *pmd; | |
685 | pte_t *ptep; | |
686 | spinlock_t *ptl; | |
687 | unsigned long addr; | |
31dbd01f IE |
688 | int err = -EFAULT; |
689 | ||
8dd3557a | 690 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
691 | if (addr == -EFAULT) |
692 | goto out; | |
693 | ||
694 | pgd = pgd_offset(mm, addr); | |
695 | if (!pgd_present(*pgd)) | |
696 | goto out; | |
697 | ||
698 | pud = pud_offset(pgd, addr); | |
699 | if (!pud_present(*pud)) | |
700 | goto out; | |
701 | ||
702 | pmd = pmd_offset(pud, addr); | |
703 | if (!pmd_present(*pmd)) | |
704 | goto out; | |
705 | ||
706 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
707 | if (!pte_same(*ptep, orig_pte)) { | |
708 | pte_unmap_unlock(ptep, ptl); | |
709 | goto out; | |
710 | } | |
711 | ||
8dd3557a HD |
712 | get_page(kpage); |
713 | page_add_ksm_rmap(kpage); | |
31dbd01f IE |
714 | |
715 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
716 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 717 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 718 | |
8dd3557a HD |
719 | page_remove_rmap(page); |
720 | put_page(page); | |
31dbd01f IE |
721 | |
722 | pte_unmap_unlock(ptep, ptl); | |
723 | err = 0; | |
724 | out: | |
725 | return err; | |
726 | } | |
727 | ||
728 | /* | |
729 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
730 | * @vma: the vma that holds the pte pointing to page |
731 | * @page: the PageAnon page that we want to replace with kpage | |
08beca44 | 732 | * @kpage: the PageKsm page that we want to map instead of page |
31dbd01f IE |
733 | * |
734 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
735 | */ | |
736 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 737 | struct page *page, struct page *kpage) |
31dbd01f IE |
738 | { |
739 | pte_t orig_pte = __pte(0); | |
740 | int err = -EFAULT; | |
741 | ||
742 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
743 | goto out; | |
8dd3557a | 744 | if (!PageAnon(page)) |
31dbd01f IE |
745 | goto out; |
746 | ||
31dbd01f IE |
747 | /* |
748 | * We need the page lock to read a stable PageSwapCache in | |
749 | * write_protect_page(). We use trylock_page() instead of | |
750 | * lock_page() because we don't want to wait here - we | |
751 | * prefer to continue scanning and merging different pages, | |
752 | * then come back to this page when it is unlocked. | |
753 | */ | |
8dd3557a | 754 | if (!trylock_page(page)) |
31e855ea | 755 | goto out; |
31dbd01f IE |
756 | /* |
757 | * If this anonymous page is mapped only here, its pte may need | |
758 | * to be write-protected. If it's mapped elsewhere, all of its | |
759 | * ptes are necessarily already write-protected. But in either | |
760 | * case, we need to lock and check page_count is not raised. | |
761 | */ | |
8dd3557a HD |
762 | if (write_protect_page(vma, page, &orig_pte) == 0 && |
763 | pages_identical(page, kpage)) | |
764 | err = replace_page(vma, page, kpage, orig_pte); | |
31dbd01f | 765 | |
73848b46 HD |
766 | if ((vma->vm_flags & VM_LOCKED) && !err) |
767 | munlock_vma_page(page); | |
768 | ||
8dd3557a | 769 | unlock_page(page); |
31dbd01f IE |
770 | out: |
771 | return err; | |
772 | } | |
773 | ||
81464e30 HD |
774 | /* |
775 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
776 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
777 | * |
778 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 779 | */ |
8dd3557a HD |
780 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
781 | struct page *page, struct page *kpage) | |
81464e30 | 782 | { |
8dd3557a | 783 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
784 | struct vm_area_struct *vma; |
785 | int err = -EFAULT; | |
786 | ||
08beca44 HD |
787 | if (page == kpage) /* ksm page forked */ |
788 | return 0; | |
789 | ||
8dd3557a HD |
790 | down_read(&mm->mmap_sem); |
791 | if (ksm_test_exit(mm)) | |
9ba69294 | 792 | goto out; |
8dd3557a HD |
793 | vma = find_vma(mm, rmap_item->address); |
794 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
795 | goto out; |
796 | ||
8dd3557a | 797 | err = try_to_merge_one_page(vma, page, kpage); |
81464e30 | 798 | out: |
8dd3557a | 799 | up_read(&mm->mmap_sem); |
81464e30 HD |
800 | return err; |
801 | } | |
802 | ||
31dbd01f IE |
803 | /* |
804 | * try_to_merge_two_pages - take two identical pages and prepare them | |
805 | * to be merged into one page. | |
806 | * | |
8dd3557a HD |
807 | * This function returns the kpage if we successfully merged two identical |
808 | * pages into one ksm page, NULL otherwise. | |
31dbd01f IE |
809 | * |
810 | * Note that this function allocates a new kernel page: if one of the pages | |
811 | * is already a ksm page, try_to_merge_with_ksm_page should be used. | |
812 | */ | |
8dd3557a HD |
813 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
814 | struct page *page, | |
815 | struct rmap_item *tree_rmap_item, | |
816 | struct page *tree_page) | |
31dbd01f | 817 | { |
8dd3557a | 818 | struct mm_struct *mm = rmap_item->mm; |
31dbd01f IE |
819 | struct vm_area_struct *vma; |
820 | struct page *kpage; | |
821 | int err = -EFAULT; | |
822 | ||
823 | /* | |
824 | * The number of nodes in the stable tree | |
825 | * is the number of kernel pages that we hold. | |
826 | */ | |
827 | if (ksm_max_kernel_pages && | |
b4028260 | 828 | ksm_max_kernel_pages <= ksm_pages_shared) |
8dd3557a | 829 | return NULL; |
31dbd01f IE |
830 | |
831 | kpage = alloc_page(GFP_HIGHUSER); | |
832 | if (!kpage) | |
8dd3557a | 833 | return NULL; |
31dbd01f | 834 | |
8dd3557a HD |
835 | down_read(&mm->mmap_sem); |
836 | if (ksm_test_exit(mm)) | |
837 | goto up; | |
838 | vma = find_vma(mm, rmap_item->address); | |
839 | if (!vma || vma->vm_start > rmap_item->address) | |
840 | goto up; | |
841 | ||
842 | copy_user_highpage(kpage, page, rmap_item->address, vma); | |
08beca44 HD |
843 | |
844 | set_page_stable_node(kpage, NULL); /* mark it PageKsm */ | |
845 | ||
8dd3557a HD |
846 | err = try_to_merge_one_page(vma, page, kpage); |
847 | up: | |
848 | up_read(&mm->mmap_sem); | |
31dbd01f IE |
849 | |
850 | if (!err) { | |
8dd3557a HD |
851 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
852 | tree_page, kpage); | |
31dbd01f | 853 | /* |
81464e30 HD |
854 | * If that fails, we have a ksm page with only one pte |
855 | * pointing to it: so break it. | |
31dbd01f IE |
856 | */ |
857 | if (err) | |
8dd3557a | 858 | break_cow(rmap_item); |
31dbd01f | 859 | } |
8dd3557a HD |
860 | if (err) { |
861 | put_page(kpage); | |
862 | kpage = NULL; | |
863 | } | |
864 | return kpage; | |
31dbd01f IE |
865 | } |
866 | ||
31dbd01f | 867 | /* |
8dd3557a | 868 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
869 | * |
870 | * This function checks if there is a page inside the stable tree | |
871 | * with identical content to the page that we are scanning right now. | |
872 | * | |
7b6ba2c7 | 873 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
874 | * NULL otherwise. |
875 | */ | |
08beca44 | 876 | static struct stable_node *stable_tree_search(struct page *page) |
31dbd01f IE |
877 | { |
878 | struct rb_node *node = root_stable_tree.rb_node; | |
7b6ba2c7 | 879 | struct stable_node *stable_node; |
31dbd01f | 880 | |
08beca44 HD |
881 | stable_node = page_stable_node(page); |
882 | if (stable_node) { /* ksm page forked */ | |
883 | get_page(page); | |
884 | return stable_node; | |
885 | } | |
886 | ||
31dbd01f | 887 | while (node) { |
31dbd01f IE |
888 | int ret; |
889 | ||
08beca44 | 890 | cond_resched(); |
7b6ba2c7 | 891 | stable_node = rb_entry(node, struct stable_node, node); |
31dbd01f | 892 | |
08beca44 | 893 | ret = memcmp_pages(page, stable_node->page); |
31dbd01f | 894 | |
08beca44 | 895 | if (ret < 0) |
31dbd01f | 896 | node = node->rb_left; |
08beca44 | 897 | else if (ret > 0) |
31dbd01f | 898 | node = node->rb_right; |
08beca44 HD |
899 | else { |
900 | get_page(stable_node->page); | |
7b6ba2c7 | 901 | return stable_node; |
31dbd01f IE |
902 | } |
903 | } | |
904 | ||
905 | return NULL; | |
906 | } | |
907 | ||
908 | /* | |
909 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
910 | * into the stable tree. | |
911 | * | |
7b6ba2c7 HD |
912 | * This function returns the stable tree node just allocated on success, |
913 | * NULL otherwise. | |
31dbd01f | 914 | */ |
7b6ba2c7 | 915 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f IE |
916 | { |
917 | struct rb_node **new = &root_stable_tree.rb_node; | |
918 | struct rb_node *parent = NULL; | |
7b6ba2c7 | 919 | struct stable_node *stable_node; |
31dbd01f IE |
920 | |
921 | while (*new) { | |
31dbd01f IE |
922 | int ret; |
923 | ||
08beca44 | 924 | cond_resched(); |
7b6ba2c7 | 925 | stable_node = rb_entry(*new, struct stable_node, node); |
31dbd01f | 926 | |
08beca44 | 927 | ret = memcmp_pages(kpage, stable_node->page); |
31dbd01f IE |
928 | |
929 | parent = *new; | |
930 | if (ret < 0) | |
931 | new = &parent->rb_left; | |
932 | else if (ret > 0) | |
933 | new = &parent->rb_right; | |
934 | else { | |
935 | /* | |
936 | * It is not a bug that stable_tree_search() didn't | |
937 | * find this node: because at that time our page was | |
938 | * not yet write-protected, so may have changed since. | |
939 | */ | |
940 | return NULL; | |
941 | } | |
942 | } | |
943 | ||
7b6ba2c7 HD |
944 | stable_node = alloc_stable_node(); |
945 | if (!stable_node) | |
946 | return NULL; | |
31dbd01f | 947 | |
7b6ba2c7 HD |
948 | rb_link_node(&stable_node->node, parent, new); |
949 | rb_insert_color(&stable_node->node, &root_stable_tree); | |
950 | ||
951 | INIT_HLIST_HEAD(&stable_node->hlist); | |
952 | ||
08beca44 HD |
953 | get_page(kpage); |
954 | stable_node->page = kpage; | |
955 | set_page_stable_node(kpage, stable_node); | |
956 | ||
7b6ba2c7 | 957 | return stable_node; |
31dbd01f IE |
958 | } |
959 | ||
960 | /* | |
8dd3557a HD |
961 | * unstable_tree_search_insert - search for identical page, |
962 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
963 | * |
964 | * This function searches for a page in the unstable tree identical to the | |
965 | * page currently being scanned; and if no identical page is found in the | |
966 | * tree, we insert rmap_item as a new object into the unstable tree. | |
967 | * | |
968 | * This function returns pointer to rmap_item found to be identical | |
969 | * to the currently scanned page, NULL otherwise. | |
970 | * | |
971 | * This function does both searching and inserting, because they share | |
972 | * the same walking algorithm in an rbtree. | |
973 | */ | |
8dd3557a HD |
974 | static |
975 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
976 | struct page *page, | |
977 | struct page **tree_pagep) | |
978 | ||
31dbd01f IE |
979 | { |
980 | struct rb_node **new = &root_unstable_tree.rb_node; | |
981 | struct rb_node *parent = NULL; | |
982 | ||
983 | while (*new) { | |
984 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 985 | struct page *tree_page; |
31dbd01f IE |
986 | int ret; |
987 | ||
d178f27f | 988 | cond_resched(); |
31dbd01f | 989 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a HD |
990 | tree_page = get_mergeable_page(tree_rmap_item); |
991 | if (!tree_page) | |
31dbd01f IE |
992 | return NULL; |
993 | ||
994 | /* | |
8dd3557a | 995 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 996 | */ |
8dd3557a HD |
997 | if (page == tree_page) { |
998 | put_page(tree_page); | |
31dbd01f IE |
999 | return NULL; |
1000 | } | |
1001 | ||
8dd3557a | 1002 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1003 | |
1004 | parent = *new; | |
1005 | if (ret < 0) { | |
8dd3557a | 1006 | put_page(tree_page); |
31dbd01f IE |
1007 | new = &parent->rb_left; |
1008 | } else if (ret > 0) { | |
8dd3557a | 1009 | put_page(tree_page); |
31dbd01f IE |
1010 | new = &parent->rb_right; |
1011 | } else { | |
8dd3557a | 1012 | *tree_pagep = tree_page; |
31dbd01f IE |
1013 | return tree_rmap_item; |
1014 | } | |
1015 | } | |
1016 | ||
7b6ba2c7 | 1017 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f IE |
1018 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
1019 | rb_link_node(&rmap_item->node, parent, new); | |
1020 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1021 | ||
473b0ce4 | 1022 | ksm_pages_unshared++; |
31dbd01f IE |
1023 | return NULL; |
1024 | } | |
1025 | ||
1026 | /* | |
1027 | * stable_tree_append - add another rmap_item to the linked list of | |
1028 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1029 | * the same ksm page. | |
1030 | */ | |
1031 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1032 | struct stable_node *stable_node) |
31dbd01f | 1033 | { |
7b6ba2c7 | 1034 | rmap_item->head = stable_node; |
31dbd01f | 1035 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1036 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1037 | |
7b6ba2c7 HD |
1038 | if (rmap_item->hlist.next) |
1039 | ksm_pages_sharing++; | |
1040 | else | |
1041 | ksm_pages_shared++; | |
31dbd01f IE |
1042 | } |
1043 | ||
1044 | /* | |
81464e30 HD |
1045 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1046 | * if not, compare checksum to previous and if it's the same, see if page can | |
1047 | * be inserted into the unstable tree, or merged with a page already there and | |
1048 | * both transferred to the stable tree. | |
31dbd01f IE |
1049 | * |
1050 | * @page: the page that we are searching identical page to. | |
1051 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1052 | */ | |
1053 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1054 | { | |
31dbd01f | 1055 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1056 | struct page *tree_page = NULL; |
7b6ba2c7 | 1057 | struct stable_node *stable_node; |
8dd3557a | 1058 | struct page *kpage; |
31dbd01f IE |
1059 | unsigned int checksum; |
1060 | int err; | |
1061 | ||
93d17715 | 1062 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1063 | |
1064 | /* We first start with searching the page inside the stable tree */ | |
08beca44 | 1065 | stable_node = stable_tree_search(page); |
7b6ba2c7 | 1066 | if (stable_node) { |
08beca44 HD |
1067 | kpage = stable_node->page; |
1068 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); | |
31dbd01f IE |
1069 | if (!err) { |
1070 | /* | |
1071 | * The page was successfully merged: | |
1072 | * add its rmap_item to the stable tree. | |
1073 | */ | |
7b6ba2c7 | 1074 | stable_tree_append(rmap_item, stable_node); |
31dbd01f | 1075 | } |
8dd3557a | 1076 | put_page(kpage); |
31dbd01f IE |
1077 | return; |
1078 | } | |
1079 | ||
1080 | /* | |
1081 | * A ksm page might have got here by fork, but its other | |
1082 | * references have already been removed from the stable tree. | |
d952b791 HD |
1083 | * Or it might be left over from a break_ksm which failed |
1084 | * when the mem_cgroup had reached its limit: try again now. | |
31dbd01f IE |
1085 | */ |
1086 | if (PageKsm(page)) | |
8dd3557a | 1087 | break_cow(rmap_item); |
31dbd01f IE |
1088 | |
1089 | /* | |
1090 | * In case the hash value of the page was changed from the last time we | |
1091 | * have calculated it, this page to be changed frequely, therefore we | |
1092 | * don't want to insert it to the unstable tree, and we don't want to | |
1093 | * waste our time to search if there is something identical to it there. | |
1094 | */ | |
1095 | checksum = calc_checksum(page); | |
1096 | if (rmap_item->oldchecksum != checksum) { | |
1097 | rmap_item->oldchecksum = checksum; | |
1098 | return; | |
1099 | } | |
1100 | ||
8dd3557a HD |
1101 | tree_rmap_item = |
1102 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1103 | if (tree_rmap_item) { |
8dd3557a HD |
1104 | kpage = try_to_merge_two_pages(rmap_item, page, |
1105 | tree_rmap_item, tree_page); | |
1106 | put_page(tree_page); | |
31dbd01f IE |
1107 | /* |
1108 | * As soon as we merge this page, we want to remove the | |
1109 | * rmap_item of the page we have merged with from the unstable | |
1110 | * tree, and insert it instead as new node in the stable tree. | |
1111 | */ | |
8dd3557a | 1112 | if (kpage) { |
93d17715 | 1113 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1114 | |
7b6ba2c7 HD |
1115 | stable_node = stable_tree_insert(kpage); |
1116 | if (stable_node) { | |
1117 | stable_tree_append(tree_rmap_item, stable_node); | |
1118 | stable_tree_append(rmap_item, stable_node); | |
1119 | } | |
1120 | put_page(kpage); | |
1121 | ||
31dbd01f IE |
1122 | /* |
1123 | * If we fail to insert the page into the stable tree, | |
1124 | * we will have 2 virtual addresses that are pointing | |
1125 | * to a ksm page left outside the stable tree, | |
1126 | * in which case we need to break_cow on both. | |
1127 | */ | |
7b6ba2c7 | 1128 | if (!stable_node) { |
8dd3557a HD |
1129 | break_cow(tree_rmap_item); |
1130 | break_cow(rmap_item); | |
31dbd01f IE |
1131 | } |
1132 | } | |
31dbd01f IE |
1133 | } |
1134 | } | |
1135 | ||
1136 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1137 | struct rmap_item **rmap_list, |
31dbd01f IE |
1138 | unsigned long addr) |
1139 | { | |
1140 | struct rmap_item *rmap_item; | |
1141 | ||
6514d511 HD |
1142 | while (*rmap_list) { |
1143 | rmap_item = *rmap_list; | |
93d17715 | 1144 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1145 | return rmap_item; |
31dbd01f IE |
1146 | if (rmap_item->address > addr) |
1147 | break; | |
6514d511 | 1148 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1149 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1150 | free_rmap_item(rmap_item); |
1151 | } | |
1152 | ||
1153 | rmap_item = alloc_rmap_item(); | |
1154 | if (rmap_item) { | |
1155 | /* It has already been zeroed */ | |
1156 | rmap_item->mm = mm_slot->mm; | |
1157 | rmap_item->address = addr; | |
6514d511 HD |
1158 | rmap_item->rmap_list = *rmap_list; |
1159 | *rmap_list = rmap_item; | |
31dbd01f IE |
1160 | } |
1161 | return rmap_item; | |
1162 | } | |
1163 | ||
1164 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1165 | { | |
1166 | struct mm_struct *mm; | |
1167 | struct mm_slot *slot; | |
1168 | struct vm_area_struct *vma; | |
1169 | struct rmap_item *rmap_item; | |
1170 | ||
1171 | if (list_empty(&ksm_mm_head.mm_list)) | |
1172 | return NULL; | |
1173 | ||
1174 | slot = ksm_scan.mm_slot; | |
1175 | if (slot == &ksm_mm_head) { | |
1176 | root_unstable_tree = RB_ROOT; | |
1177 | ||
1178 | spin_lock(&ksm_mmlist_lock); | |
1179 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1180 | ksm_scan.mm_slot = slot; | |
1181 | spin_unlock(&ksm_mmlist_lock); | |
1182 | next_mm: | |
1183 | ksm_scan.address = 0; | |
6514d511 | 1184 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1185 | } |
1186 | ||
1187 | mm = slot->mm; | |
1188 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1189 | if (ksm_test_exit(mm)) |
1190 | vma = NULL; | |
1191 | else | |
1192 | vma = find_vma(mm, ksm_scan.address); | |
1193 | ||
1194 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1195 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1196 | continue; | |
1197 | if (ksm_scan.address < vma->vm_start) | |
1198 | ksm_scan.address = vma->vm_start; | |
1199 | if (!vma->anon_vma) | |
1200 | ksm_scan.address = vma->vm_end; | |
1201 | ||
1202 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1203 | if (ksm_test_exit(mm)) |
1204 | break; | |
31dbd01f IE |
1205 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
1206 | if (*page && PageAnon(*page)) { | |
1207 | flush_anon_page(vma, *page, ksm_scan.address); | |
1208 | flush_dcache_page(*page); | |
1209 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1210 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1211 | if (rmap_item) { |
6514d511 HD |
1212 | ksm_scan.rmap_list = |
1213 | &rmap_item->rmap_list; | |
31dbd01f IE |
1214 | ksm_scan.address += PAGE_SIZE; |
1215 | } else | |
1216 | put_page(*page); | |
1217 | up_read(&mm->mmap_sem); | |
1218 | return rmap_item; | |
1219 | } | |
1220 | if (*page) | |
1221 | put_page(*page); | |
1222 | ksm_scan.address += PAGE_SIZE; | |
1223 | cond_resched(); | |
1224 | } | |
1225 | } | |
1226 | ||
9ba69294 HD |
1227 | if (ksm_test_exit(mm)) { |
1228 | ksm_scan.address = 0; | |
6514d511 | 1229 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1230 | } |
31dbd01f IE |
1231 | /* |
1232 | * Nuke all the rmap_items that are above this current rmap: | |
1233 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1234 | */ | |
6514d511 | 1235 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1236 | |
1237 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1238 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1239 | struct mm_slot, mm_list); | |
1240 | if (ksm_scan.address == 0) { | |
1241 | /* | |
1242 | * We've completed a full scan of all vmas, holding mmap_sem | |
1243 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1244 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1245 | * This applies either when cleaning up after __ksm_exit |
1246 | * (but beware: we can reach here even before __ksm_exit), | |
1247 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1248 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1249 | */ |
1250 | hlist_del(&slot->link); | |
1251 | list_del(&slot->mm_list); | |
9ba69294 HD |
1252 | spin_unlock(&ksm_mmlist_lock); |
1253 | ||
cd551f97 HD |
1254 | free_mm_slot(slot); |
1255 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1256 | up_read(&mm->mmap_sem); |
1257 | mmdrop(mm); | |
1258 | } else { | |
1259 | spin_unlock(&ksm_mmlist_lock); | |
1260 | up_read(&mm->mmap_sem); | |
cd551f97 | 1261 | } |
31dbd01f IE |
1262 | |
1263 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1264 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1265 | if (slot != &ksm_mm_head) |
1266 | goto next_mm; | |
1267 | ||
31dbd01f IE |
1268 | ksm_scan.seqnr++; |
1269 | return NULL; | |
1270 | } | |
1271 | ||
1272 | /** | |
1273 | * ksm_do_scan - the ksm scanner main worker function. | |
1274 | * @scan_npages - number of pages we want to scan before we return. | |
1275 | */ | |
1276 | static void ksm_do_scan(unsigned int scan_npages) | |
1277 | { | |
1278 | struct rmap_item *rmap_item; | |
1279 | struct page *page; | |
1280 | ||
1281 | while (scan_npages--) { | |
1282 | cond_resched(); | |
1283 | rmap_item = scan_get_next_rmap_item(&page); | |
1284 | if (!rmap_item) | |
1285 | return; | |
1286 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1287 | cmp_and_merge_page(page, rmap_item); | |
26465d3e HD |
1288 | else if (page_mapcount(page) == 1) { |
1289 | /* | |
1290 | * Replace now-unshared ksm page by ordinary page. | |
1291 | */ | |
8dd3557a | 1292 | break_cow(rmap_item); |
26465d3e HD |
1293 | remove_rmap_item_from_tree(rmap_item); |
1294 | rmap_item->oldchecksum = calc_checksum(page); | |
1295 | } | |
31dbd01f IE |
1296 | put_page(page); |
1297 | } | |
1298 | } | |
1299 | ||
6e158384 HD |
1300 | static int ksmd_should_run(void) |
1301 | { | |
1302 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1303 | } | |
1304 | ||
31dbd01f IE |
1305 | static int ksm_scan_thread(void *nothing) |
1306 | { | |
339aa624 | 1307 | set_user_nice(current, 5); |
31dbd01f IE |
1308 | |
1309 | while (!kthread_should_stop()) { | |
6e158384 HD |
1310 | mutex_lock(&ksm_thread_mutex); |
1311 | if (ksmd_should_run()) | |
31dbd01f | 1312 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1313 | mutex_unlock(&ksm_thread_mutex); |
1314 | ||
1315 | if (ksmd_should_run()) { | |
31dbd01f IE |
1316 | schedule_timeout_interruptible( |
1317 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1318 | } else { | |
1319 | wait_event_interruptible(ksm_thread_wait, | |
6e158384 | 1320 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1321 | } |
1322 | } | |
1323 | return 0; | |
1324 | } | |
1325 | ||
f8af4da3 HD |
1326 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1327 | unsigned long end, int advice, unsigned long *vm_flags) | |
1328 | { | |
1329 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1330 | int err; |
f8af4da3 HD |
1331 | |
1332 | switch (advice) { | |
1333 | case MADV_MERGEABLE: | |
1334 | /* | |
1335 | * Be somewhat over-protective for now! | |
1336 | */ | |
1337 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1338 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1339 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
1340 | VM_MIXEDMAP | VM_SAO)) | |
1341 | return 0; /* just ignore the advice */ | |
1342 | ||
d952b791 HD |
1343 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1344 | err = __ksm_enter(mm); | |
1345 | if (err) | |
1346 | return err; | |
1347 | } | |
f8af4da3 HD |
1348 | |
1349 | *vm_flags |= VM_MERGEABLE; | |
1350 | break; | |
1351 | ||
1352 | case MADV_UNMERGEABLE: | |
1353 | if (!(*vm_flags & VM_MERGEABLE)) | |
1354 | return 0; /* just ignore the advice */ | |
1355 | ||
d952b791 HD |
1356 | if (vma->anon_vma) { |
1357 | err = unmerge_ksm_pages(vma, start, end); | |
1358 | if (err) | |
1359 | return err; | |
1360 | } | |
f8af4da3 HD |
1361 | |
1362 | *vm_flags &= ~VM_MERGEABLE; | |
1363 | break; | |
1364 | } | |
1365 | ||
1366 | return 0; | |
1367 | } | |
1368 | ||
1369 | int __ksm_enter(struct mm_struct *mm) | |
1370 | { | |
6e158384 HD |
1371 | struct mm_slot *mm_slot; |
1372 | int needs_wakeup; | |
1373 | ||
1374 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1375 | if (!mm_slot) |
1376 | return -ENOMEM; | |
1377 | ||
6e158384 HD |
1378 | /* Check ksm_run too? Would need tighter locking */ |
1379 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1380 | ||
31dbd01f IE |
1381 | spin_lock(&ksm_mmlist_lock); |
1382 | insert_to_mm_slots_hash(mm, mm_slot); | |
1383 | /* | |
1384 | * Insert just behind the scanning cursor, to let the area settle | |
1385 | * down a little; when fork is followed by immediate exec, we don't | |
1386 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1387 | */ | |
1388 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1389 | spin_unlock(&ksm_mmlist_lock); | |
1390 | ||
f8af4da3 | 1391 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1392 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1393 | |
1394 | if (needs_wakeup) | |
1395 | wake_up_interruptible(&ksm_thread_wait); | |
1396 | ||
f8af4da3 HD |
1397 | return 0; |
1398 | } | |
1399 | ||
1c2fb7a4 | 1400 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1401 | { |
cd551f97 | 1402 | struct mm_slot *mm_slot; |
9ba69294 | 1403 | int easy_to_free = 0; |
cd551f97 | 1404 | |
31dbd01f | 1405 | /* |
9ba69294 HD |
1406 | * This process is exiting: if it's straightforward (as is the |
1407 | * case when ksmd was never running), free mm_slot immediately. | |
1408 | * But if it's at the cursor or has rmap_items linked to it, use | |
1409 | * mmap_sem to synchronize with any break_cows before pagetables | |
1410 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1411 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1412 | */ |
9ba69294 | 1413 | |
cd551f97 HD |
1414 | spin_lock(&ksm_mmlist_lock); |
1415 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1416 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1417 | if (!mm_slot->rmap_list) { |
9ba69294 HD |
1418 | hlist_del(&mm_slot->link); |
1419 | list_del(&mm_slot->mm_list); | |
1420 | easy_to_free = 1; | |
1421 | } else { | |
1422 | list_move(&mm_slot->mm_list, | |
1423 | &ksm_scan.mm_slot->mm_list); | |
1424 | } | |
cd551f97 | 1425 | } |
cd551f97 HD |
1426 | spin_unlock(&ksm_mmlist_lock); |
1427 | ||
9ba69294 HD |
1428 | if (easy_to_free) { |
1429 | free_mm_slot(mm_slot); | |
1430 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1431 | mmdrop(mm); | |
1432 | } else if (mm_slot) { | |
9ba69294 HD |
1433 | down_write(&mm->mmap_sem); |
1434 | up_write(&mm->mmap_sem); | |
9ba69294 | 1435 | } |
31dbd01f IE |
1436 | } |
1437 | ||
2ffd8679 HD |
1438 | #ifdef CONFIG_SYSFS |
1439 | /* | |
1440 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1441 | */ | |
1442 | ||
31dbd01f IE |
1443 | #define KSM_ATTR_RO(_name) \ |
1444 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1445 | #define KSM_ATTR(_name) \ | |
1446 | static struct kobj_attribute _name##_attr = \ | |
1447 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1448 | ||
1449 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1450 | struct kobj_attribute *attr, char *buf) | |
1451 | { | |
1452 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1453 | } | |
1454 | ||
1455 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1456 | struct kobj_attribute *attr, | |
1457 | const char *buf, size_t count) | |
1458 | { | |
1459 | unsigned long msecs; | |
1460 | int err; | |
1461 | ||
1462 | err = strict_strtoul(buf, 10, &msecs); | |
1463 | if (err || msecs > UINT_MAX) | |
1464 | return -EINVAL; | |
1465 | ||
1466 | ksm_thread_sleep_millisecs = msecs; | |
1467 | ||
1468 | return count; | |
1469 | } | |
1470 | KSM_ATTR(sleep_millisecs); | |
1471 | ||
1472 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1473 | struct kobj_attribute *attr, char *buf) | |
1474 | { | |
1475 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1476 | } | |
1477 | ||
1478 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1479 | struct kobj_attribute *attr, | |
1480 | const char *buf, size_t count) | |
1481 | { | |
1482 | int err; | |
1483 | unsigned long nr_pages; | |
1484 | ||
1485 | err = strict_strtoul(buf, 10, &nr_pages); | |
1486 | if (err || nr_pages > UINT_MAX) | |
1487 | return -EINVAL; | |
1488 | ||
1489 | ksm_thread_pages_to_scan = nr_pages; | |
1490 | ||
1491 | return count; | |
1492 | } | |
1493 | KSM_ATTR(pages_to_scan); | |
1494 | ||
1495 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1496 | char *buf) | |
1497 | { | |
1498 | return sprintf(buf, "%u\n", ksm_run); | |
1499 | } | |
1500 | ||
1501 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1502 | const char *buf, size_t count) | |
1503 | { | |
1504 | int err; | |
1505 | unsigned long flags; | |
1506 | ||
1507 | err = strict_strtoul(buf, 10, &flags); | |
1508 | if (err || flags > UINT_MAX) | |
1509 | return -EINVAL; | |
1510 | if (flags > KSM_RUN_UNMERGE) | |
1511 | return -EINVAL; | |
1512 | ||
1513 | /* | |
1514 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1515 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
b4028260 | 1516 | * breaking COW to free the unswappable pages_shared (but leaves |
31dbd01f IE |
1517 | * mm_slots on the list for when ksmd may be set running again). |
1518 | */ | |
1519 | ||
1520 | mutex_lock(&ksm_thread_mutex); | |
1521 | if (ksm_run != flags) { | |
1522 | ksm_run = flags; | |
d952b791 | 1523 | if (flags & KSM_RUN_UNMERGE) { |
35451bee | 1524 | current->flags |= PF_OOM_ORIGIN; |
d952b791 | 1525 | err = unmerge_and_remove_all_rmap_items(); |
35451bee | 1526 | current->flags &= ~PF_OOM_ORIGIN; |
d952b791 HD |
1527 | if (err) { |
1528 | ksm_run = KSM_RUN_STOP; | |
1529 | count = err; | |
1530 | } | |
1531 | } | |
31dbd01f IE |
1532 | } |
1533 | mutex_unlock(&ksm_thread_mutex); | |
1534 | ||
1535 | if (flags & KSM_RUN_MERGE) | |
1536 | wake_up_interruptible(&ksm_thread_wait); | |
1537 | ||
1538 | return count; | |
1539 | } | |
1540 | KSM_ATTR(run); | |
1541 | ||
31dbd01f IE |
1542 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
1543 | struct kobj_attribute *attr, | |
1544 | const char *buf, size_t count) | |
1545 | { | |
1546 | int err; | |
1547 | unsigned long nr_pages; | |
1548 | ||
1549 | err = strict_strtoul(buf, 10, &nr_pages); | |
1550 | if (err) | |
1551 | return -EINVAL; | |
1552 | ||
1553 | ksm_max_kernel_pages = nr_pages; | |
1554 | ||
1555 | return count; | |
1556 | } | |
1557 | ||
1558 | static ssize_t max_kernel_pages_show(struct kobject *kobj, | |
1559 | struct kobj_attribute *attr, char *buf) | |
1560 | { | |
1561 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); | |
1562 | } | |
1563 | KSM_ATTR(max_kernel_pages); | |
1564 | ||
b4028260 HD |
1565 | static ssize_t pages_shared_show(struct kobject *kobj, |
1566 | struct kobj_attribute *attr, char *buf) | |
1567 | { | |
1568 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1569 | } | |
1570 | KSM_ATTR_RO(pages_shared); | |
1571 | ||
1572 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1573 | struct kobj_attribute *attr, char *buf) | |
1574 | { | |
e178dfde | 1575 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1576 | } |
1577 | KSM_ATTR_RO(pages_sharing); | |
1578 | ||
473b0ce4 HD |
1579 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1580 | struct kobj_attribute *attr, char *buf) | |
1581 | { | |
1582 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1583 | } | |
1584 | KSM_ATTR_RO(pages_unshared); | |
1585 | ||
1586 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1587 | struct kobj_attribute *attr, char *buf) | |
1588 | { | |
1589 | long ksm_pages_volatile; | |
1590 | ||
1591 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1592 | - ksm_pages_sharing - ksm_pages_unshared; | |
1593 | /* | |
1594 | * It was not worth any locking to calculate that statistic, | |
1595 | * but it might therefore sometimes be negative: conceal that. | |
1596 | */ | |
1597 | if (ksm_pages_volatile < 0) | |
1598 | ksm_pages_volatile = 0; | |
1599 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1600 | } | |
1601 | KSM_ATTR_RO(pages_volatile); | |
1602 | ||
1603 | static ssize_t full_scans_show(struct kobject *kobj, | |
1604 | struct kobj_attribute *attr, char *buf) | |
1605 | { | |
1606 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1607 | } | |
1608 | KSM_ATTR_RO(full_scans); | |
1609 | ||
31dbd01f IE |
1610 | static struct attribute *ksm_attrs[] = { |
1611 | &sleep_millisecs_attr.attr, | |
1612 | &pages_to_scan_attr.attr, | |
1613 | &run_attr.attr, | |
31dbd01f | 1614 | &max_kernel_pages_attr.attr, |
b4028260 HD |
1615 | &pages_shared_attr.attr, |
1616 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1617 | &pages_unshared_attr.attr, |
1618 | &pages_volatile_attr.attr, | |
1619 | &full_scans_attr.attr, | |
31dbd01f IE |
1620 | NULL, |
1621 | }; | |
1622 | ||
1623 | static struct attribute_group ksm_attr_group = { | |
1624 | .attrs = ksm_attrs, | |
1625 | .name = "ksm", | |
1626 | }; | |
2ffd8679 | 1627 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1628 | |
1629 | static int __init ksm_init(void) | |
1630 | { | |
1631 | struct task_struct *ksm_thread; | |
1632 | int err; | |
1633 | ||
c73602ad | 1634 | ksm_max_kernel_pages = totalram_pages / 4; |
2c6854fd | 1635 | |
31dbd01f IE |
1636 | err = ksm_slab_init(); |
1637 | if (err) | |
1638 | goto out; | |
1639 | ||
1640 | err = mm_slots_hash_init(); | |
1641 | if (err) | |
1642 | goto out_free1; | |
1643 | ||
1644 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); | |
1645 | if (IS_ERR(ksm_thread)) { | |
1646 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
1647 | err = PTR_ERR(ksm_thread); | |
1648 | goto out_free2; | |
1649 | } | |
1650 | ||
2ffd8679 | 1651 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
1652 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
1653 | if (err) { | |
1654 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 HD |
1655 | kthread_stop(ksm_thread); |
1656 | goto out_free2; | |
31dbd01f | 1657 | } |
c73602ad HD |
1658 | #else |
1659 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
1660 | ||
2ffd8679 | 1661 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1662 | |
1663 | return 0; | |
1664 | ||
31dbd01f IE |
1665 | out_free2: |
1666 | mm_slots_hash_free(); | |
1667 | out_free1: | |
1668 | ksm_slab_free(); | |
1669 | out: | |
1670 | return err; | |
f8af4da3 | 1671 | } |
31dbd01f | 1672 | module_init(ksm_init) |