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 | |
82 | * @rmap_list: head for this mm_slot's list of rmap_items | |
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; | |
88 | struct list_head rmap_list; | |
89 | struct mm_struct *mm; | |
90 | }; | |
91 | ||
92 | /** | |
93 | * struct ksm_scan - cursor for scanning | |
94 | * @mm_slot: the current mm_slot we are scanning | |
95 | * @address: the next address inside that to be scanned | |
96 | * @rmap_item: the current rmap that we are scanning inside the rmap_list | |
97 | * @seqnr: count of completed full scans (needed when removing unstable node) | |
98 | * | |
99 | * There is only the one ksm_scan instance of this cursor structure. | |
100 | */ | |
101 | struct ksm_scan { | |
102 | struct mm_slot *mm_slot; | |
103 | unsigned long address; | |
104 | struct rmap_item *rmap_item; | |
105 | unsigned long seqnr; | |
106 | }; | |
107 | ||
108 | /** | |
109 | * struct rmap_item - reverse mapping item for virtual addresses | |
110 | * @link: link into mm_slot's rmap_list (rmap_list is per mm) | |
111 | * @mm: the memory structure this rmap_item is pointing into | |
112 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
113 | * @oldchecksum: previous checksum of the page at that virtual address | |
114 | * @node: rb_node of this rmap_item in either unstable or stable tree | |
115 | * @next: next rmap_item hanging off the same node of the stable tree | |
116 | * @prev: previous rmap_item hanging off the same node of the stable tree | |
117 | */ | |
118 | struct rmap_item { | |
119 | struct list_head link; | |
120 | struct mm_struct *mm; | |
121 | unsigned long address; /* + low bits used for flags below */ | |
122 | union { | |
123 | unsigned int oldchecksum; /* when unstable */ | |
124 | struct rmap_item *next; /* when stable */ | |
125 | }; | |
126 | union { | |
127 | struct rb_node node; /* when tree node */ | |
128 | struct rmap_item *prev; /* in stable list */ | |
129 | }; | |
130 | }; | |
131 | ||
132 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
133 | #define NODE_FLAG 0x100 /* is a node of unstable or stable tree */ | |
134 | #define STABLE_FLAG 0x200 /* is a node or list item of stable tree */ | |
135 | ||
136 | /* The stable and unstable tree heads */ | |
137 | static struct rb_root root_stable_tree = RB_ROOT; | |
138 | static struct rb_root root_unstable_tree = RB_ROOT; | |
139 | ||
140 | #define MM_SLOTS_HASH_HEADS 1024 | |
141 | static struct hlist_head *mm_slots_hash; | |
142 | ||
143 | static struct mm_slot ksm_mm_head = { | |
144 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
145 | }; | |
146 | static struct ksm_scan ksm_scan = { | |
147 | .mm_slot = &ksm_mm_head, | |
148 | }; | |
149 | ||
150 | static struct kmem_cache *rmap_item_cache; | |
151 | static struct kmem_cache *mm_slot_cache; | |
152 | ||
153 | /* The number of nodes in the stable tree */ | |
b4028260 | 154 | static unsigned long ksm_pages_shared; |
31dbd01f | 155 | |
e178dfde | 156 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 157 | static unsigned long ksm_pages_sharing; |
31dbd01f | 158 | |
473b0ce4 HD |
159 | /* The number of nodes in the unstable tree */ |
160 | static unsigned long ksm_pages_unshared; | |
161 | ||
162 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
163 | static unsigned long ksm_rmap_items; | |
164 | ||
31dbd01f | 165 | /* Limit on the number of unswappable pages used */ |
2c6854fd | 166 | static unsigned long ksm_max_kernel_pages; |
31dbd01f IE |
167 | |
168 | /* Number of pages ksmd should scan in one batch */ | |
2c6854fd | 169 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
170 | |
171 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 172 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
173 | |
174 | #define KSM_RUN_STOP 0 | |
175 | #define KSM_RUN_MERGE 1 | |
176 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 177 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
178 | |
179 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
180 | static DEFINE_MUTEX(ksm_thread_mutex); | |
181 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
182 | ||
183 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
184 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
185 | (__flags), NULL) | |
186 | ||
187 | static int __init ksm_slab_init(void) | |
188 | { | |
189 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
190 | if (!rmap_item_cache) | |
191 | goto out; | |
192 | ||
193 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); | |
194 | if (!mm_slot_cache) | |
195 | goto out_free; | |
196 | ||
197 | return 0; | |
198 | ||
199 | out_free: | |
200 | kmem_cache_destroy(rmap_item_cache); | |
201 | out: | |
202 | return -ENOMEM; | |
203 | } | |
204 | ||
205 | static void __init ksm_slab_free(void) | |
206 | { | |
207 | kmem_cache_destroy(mm_slot_cache); | |
208 | kmem_cache_destroy(rmap_item_cache); | |
209 | mm_slot_cache = NULL; | |
210 | } | |
211 | ||
212 | static inline struct rmap_item *alloc_rmap_item(void) | |
213 | { | |
473b0ce4 HD |
214 | struct rmap_item *rmap_item; |
215 | ||
216 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
217 | if (rmap_item) | |
218 | ksm_rmap_items++; | |
219 | return rmap_item; | |
31dbd01f IE |
220 | } |
221 | ||
222 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
223 | { | |
473b0ce4 | 224 | ksm_rmap_items--; |
31dbd01f IE |
225 | rmap_item->mm = NULL; /* debug safety */ |
226 | kmem_cache_free(rmap_item_cache, rmap_item); | |
227 | } | |
228 | ||
229 | static inline struct mm_slot *alloc_mm_slot(void) | |
230 | { | |
231 | if (!mm_slot_cache) /* initialization failed */ | |
232 | return NULL; | |
233 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
234 | } | |
235 | ||
236 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
237 | { | |
238 | kmem_cache_free(mm_slot_cache, mm_slot); | |
239 | } | |
240 | ||
241 | static int __init mm_slots_hash_init(void) | |
242 | { | |
243 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), | |
244 | GFP_KERNEL); | |
245 | if (!mm_slots_hash) | |
246 | return -ENOMEM; | |
247 | return 0; | |
248 | } | |
249 | ||
250 | static void __init mm_slots_hash_free(void) | |
251 | { | |
252 | kfree(mm_slots_hash); | |
253 | } | |
254 | ||
255 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
256 | { | |
257 | struct mm_slot *mm_slot; | |
258 | struct hlist_head *bucket; | |
259 | struct hlist_node *node; | |
260 | ||
261 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
262 | % MM_SLOTS_HASH_HEADS]; | |
263 | hlist_for_each_entry(mm_slot, node, bucket, link) { | |
264 | if (mm == mm_slot->mm) | |
265 | return mm_slot; | |
266 | } | |
267 | return NULL; | |
268 | } | |
269 | ||
270 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
271 | struct mm_slot *mm_slot) | |
272 | { | |
273 | struct hlist_head *bucket; | |
274 | ||
275 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
276 | % MM_SLOTS_HASH_HEADS]; | |
277 | mm_slot->mm = mm; | |
278 | INIT_LIST_HEAD(&mm_slot->rmap_list); | |
279 | hlist_add_head(&mm_slot->link, bucket); | |
280 | } | |
281 | ||
282 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
283 | { | |
284 | return rmap_item->address & STABLE_FLAG; | |
285 | } | |
286 | ||
a913e182 HD |
287 | /* |
288 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
289 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
290 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
291 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
292 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
293 | * places for correctness, in some places just to avoid unnecessary work. | |
294 | */ | |
295 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
296 | { | |
297 | return atomic_read(&mm->mm_users) == 0; | |
298 | } | |
299 | ||
31dbd01f IE |
300 | /* |
301 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
302 | * | |
303 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
304 | * put_page(page); | |
305 | * | |
306 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
307 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
308 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
309 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
310 | */ | |
d952b791 | 311 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
312 | { |
313 | struct page *page; | |
d952b791 | 314 | int ret = 0; |
31dbd01f IE |
315 | |
316 | do { | |
317 | cond_resched(); | |
318 | page = follow_page(vma, addr, FOLL_GET); | |
319 | if (!page) | |
320 | break; | |
321 | if (PageKsm(page)) | |
322 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
323 | FAULT_FLAG_WRITE); | |
324 | else | |
325 | ret = VM_FAULT_WRITE; | |
326 | put_page(page); | |
d952b791 HD |
327 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
328 | /* | |
329 | * We must loop because handle_mm_fault() may back out if there's | |
330 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
331 | * | |
332 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
333 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
334 | * but note that a concurrent fault might break PageKsm for us. | |
335 | * | |
336 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
337 | * backing file, which also invalidates anonymous pages: that's | |
338 | * okay, that truncation will have unmapped the PageKsm for us. | |
339 | * | |
340 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
341 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
342 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
343 | * to user; and ksmd, having no mm, would never be chosen for that. | |
344 | * | |
345 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
346 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
347 | * even ksmd can fail in this way - though it's usually breaking ksm | |
348 | * just to undo a merge it made a moment before, so unlikely to oom. | |
349 | * | |
350 | * That's a pity: we might therefore have more kernel pages allocated | |
351 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
352 | * will retry to break_cow on each pass, so should recover the page | |
353 | * in due course. The important thing is to not let VM_MERGEABLE | |
354 | * be cleared while any such pages might remain in the area. | |
355 | */ | |
356 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
357 | } |
358 | ||
81464e30 | 359 | static void break_cow(struct mm_struct *mm, unsigned long addr) |
31dbd01f IE |
360 | { |
361 | struct vm_area_struct *vma; | |
362 | ||
81464e30 | 363 | down_read(&mm->mmap_sem); |
9ba69294 HD |
364 | if (ksm_test_exit(mm)) |
365 | goto out; | |
31dbd01f IE |
366 | vma = find_vma(mm, addr); |
367 | if (!vma || vma->vm_start > addr) | |
81464e30 | 368 | goto out; |
31dbd01f | 369 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 370 | goto out; |
31dbd01f | 371 | break_ksm(vma, addr); |
81464e30 | 372 | out: |
31dbd01f IE |
373 | up_read(&mm->mmap_sem); |
374 | } | |
375 | ||
376 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
377 | { | |
378 | struct mm_struct *mm = rmap_item->mm; | |
379 | unsigned long addr = rmap_item->address; | |
380 | struct vm_area_struct *vma; | |
381 | struct page *page; | |
382 | ||
383 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
384 | if (ksm_test_exit(mm)) |
385 | goto out; | |
31dbd01f IE |
386 | vma = find_vma(mm, addr); |
387 | if (!vma || vma->vm_start > addr) | |
388 | goto out; | |
389 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
390 | goto out; | |
391 | ||
392 | page = follow_page(vma, addr, FOLL_GET); | |
393 | if (!page) | |
394 | goto out; | |
395 | if (PageAnon(page)) { | |
396 | flush_anon_page(vma, page, addr); | |
397 | flush_dcache_page(page); | |
398 | } else { | |
399 | put_page(page); | |
400 | out: page = NULL; | |
401 | } | |
402 | up_read(&mm->mmap_sem); | |
403 | return page; | |
404 | } | |
405 | ||
406 | /* | |
407 | * get_ksm_page: checks if the page at the virtual address in rmap_item | |
408 | * is still PageKsm, in which case we can trust the content of the page, | |
409 | * and it returns the gotten page; but NULL if the page has been zapped. | |
410 | */ | |
411 | static struct page *get_ksm_page(struct rmap_item *rmap_item) | |
412 | { | |
413 | struct page *page; | |
414 | ||
415 | page = get_mergeable_page(rmap_item); | |
416 | if (page && !PageKsm(page)) { | |
417 | put_page(page); | |
418 | page = NULL; | |
419 | } | |
420 | return page; | |
421 | } | |
422 | ||
423 | /* | |
424 | * Removing rmap_item from stable or unstable tree. | |
425 | * This function will clean the information from the stable/unstable tree. | |
426 | */ | |
427 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
428 | { | |
429 | if (in_stable_tree(rmap_item)) { | |
430 | struct rmap_item *next_item = rmap_item->next; | |
431 | ||
432 | if (rmap_item->address & NODE_FLAG) { | |
433 | if (next_item) { | |
434 | rb_replace_node(&rmap_item->node, | |
435 | &next_item->node, | |
436 | &root_stable_tree); | |
437 | next_item->address |= NODE_FLAG; | |
e178dfde | 438 | ksm_pages_sharing--; |
31dbd01f IE |
439 | } else { |
440 | rb_erase(&rmap_item->node, &root_stable_tree); | |
b4028260 | 441 | ksm_pages_shared--; |
31dbd01f IE |
442 | } |
443 | } else { | |
444 | struct rmap_item *prev_item = rmap_item->prev; | |
445 | ||
446 | BUG_ON(prev_item->next != rmap_item); | |
447 | prev_item->next = next_item; | |
448 | if (next_item) { | |
449 | BUG_ON(next_item->prev != rmap_item); | |
450 | next_item->prev = rmap_item->prev; | |
451 | } | |
e178dfde | 452 | ksm_pages_sharing--; |
31dbd01f IE |
453 | } |
454 | ||
455 | rmap_item->next = NULL; | |
31dbd01f IE |
456 | |
457 | } else if (rmap_item->address & NODE_FLAG) { | |
458 | unsigned char age; | |
459 | /* | |
9ba69294 | 460 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 461 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
462 | * But be careful when an mm is exiting: do the rb_erase |
463 | * if this rmap_item was inserted by this scan, rather | |
464 | * than left over from before. | |
31dbd01f IE |
465 | */ |
466 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 467 | BUG_ON(age > 1); |
31dbd01f IE |
468 | if (!age) |
469 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
473b0ce4 | 470 | ksm_pages_unshared--; |
31dbd01f IE |
471 | } |
472 | ||
473 | rmap_item->address &= PAGE_MASK; | |
474 | ||
475 | cond_resched(); /* we're called from many long loops */ | |
476 | } | |
477 | ||
31dbd01f IE |
478 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
479 | struct list_head *cur) | |
480 | { | |
481 | struct rmap_item *rmap_item; | |
482 | ||
483 | while (cur != &mm_slot->rmap_list) { | |
484 | rmap_item = list_entry(cur, struct rmap_item, link); | |
485 | cur = cur->next; | |
486 | remove_rmap_item_from_tree(rmap_item); | |
487 | list_del(&rmap_item->link); | |
488 | free_rmap_item(rmap_item); | |
489 | } | |
490 | } | |
491 | ||
492 | /* | |
493 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather | |
494 | * than check every pte of a given vma, the locking doesn't quite work for | |
495 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
496 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
497 | * rmap_items from parent to child at fork time (so as not to waste time | |
498 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
499 | * |
500 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
501 | * and freeing memory) when unmerging an area, it's easier to leave that | |
502 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
503 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 504 | */ |
d952b791 HD |
505 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
506 | unsigned long start, unsigned long end) | |
31dbd01f IE |
507 | { |
508 | unsigned long addr; | |
d952b791 | 509 | int err = 0; |
31dbd01f | 510 | |
d952b791 | 511 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
512 | if (ksm_test_exit(vma->vm_mm)) |
513 | break; | |
d952b791 HD |
514 | if (signal_pending(current)) |
515 | err = -ERESTARTSYS; | |
516 | else | |
517 | err = break_ksm(vma, addr); | |
518 | } | |
519 | return err; | |
31dbd01f IE |
520 | } |
521 | ||
2ffd8679 HD |
522 | #ifdef CONFIG_SYSFS |
523 | /* | |
524 | * Only called through the sysfs control interface: | |
525 | */ | |
d952b791 | 526 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
527 | { |
528 | struct mm_slot *mm_slot; | |
529 | struct mm_struct *mm; | |
530 | struct vm_area_struct *vma; | |
d952b791 HD |
531 | int err = 0; |
532 | ||
533 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 534 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
535 | struct mm_slot, mm_list); |
536 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 537 | |
9ba69294 HD |
538 | for (mm_slot = ksm_scan.mm_slot; |
539 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
540 | mm = mm_slot->mm; |
541 | down_read(&mm->mmap_sem); | |
542 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
543 | if (ksm_test_exit(mm)) |
544 | break; | |
31dbd01f IE |
545 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
546 | continue; | |
d952b791 HD |
547 | err = unmerge_ksm_pages(vma, |
548 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
549 | if (err) |
550 | goto error; | |
31dbd01f | 551 | } |
9ba69294 | 552 | |
81464e30 | 553 | remove_trailing_rmap_items(mm_slot, mm_slot->rmap_list.next); |
d952b791 HD |
554 | |
555 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 556 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 557 | struct mm_slot, mm_list); |
9ba69294 HD |
558 | if (ksm_test_exit(mm)) { |
559 | hlist_del(&mm_slot->link); | |
560 | list_del(&mm_slot->mm_list); | |
561 | spin_unlock(&ksm_mmlist_lock); | |
562 | ||
563 | free_mm_slot(mm_slot); | |
564 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
565 | up_read(&mm->mmap_sem); | |
566 | mmdrop(mm); | |
567 | } else { | |
568 | spin_unlock(&ksm_mmlist_lock); | |
569 | up_read(&mm->mmap_sem); | |
570 | } | |
31dbd01f IE |
571 | } |
572 | ||
d952b791 | 573 | ksm_scan.seqnr = 0; |
9ba69294 HD |
574 | return 0; |
575 | ||
576 | error: | |
577 | up_read(&mm->mmap_sem); | |
31dbd01f | 578 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 579 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 580 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 581 | return err; |
31dbd01f | 582 | } |
2ffd8679 | 583 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 584 | |
31dbd01f IE |
585 | static u32 calc_checksum(struct page *page) |
586 | { | |
587 | u32 checksum; | |
588 | void *addr = kmap_atomic(page, KM_USER0); | |
589 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); | |
590 | kunmap_atomic(addr, KM_USER0); | |
591 | return checksum; | |
592 | } | |
593 | ||
594 | static int memcmp_pages(struct page *page1, struct page *page2) | |
595 | { | |
596 | char *addr1, *addr2; | |
597 | int ret; | |
598 | ||
599 | addr1 = kmap_atomic(page1, KM_USER0); | |
600 | addr2 = kmap_atomic(page2, KM_USER1); | |
601 | ret = memcmp(addr1, addr2, PAGE_SIZE); | |
602 | kunmap_atomic(addr2, KM_USER1); | |
603 | kunmap_atomic(addr1, KM_USER0); | |
604 | return ret; | |
605 | } | |
606 | ||
607 | static inline int pages_identical(struct page *page1, struct page *page2) | |
608 | { | |
609 | return !memcmp_pages(page1, page2); | |
610 | } | |
611 | ||
612 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
613 | pte_t *orig_pte) | |
614 | { | |
615 | struct mm_struct *mm = vma->vm_mm; | |
616 | unsigned long addr; | |
617 | pte_t *ptep; | |
618 | spinlock_t *ptl; | |
619 | int swapped; | |
620 | int err = -EFAULT; | |
621 | ||
622 | addr = page_address_in_vma(page, vma); | |
623 | if (addr == -EFAULT) | |
624 | goto out; | |
625 | ||
626 | ptep = page_check_address(page, mm, addr, &ptl, 0); | |
627 | if (!ptep) | |
628 | goto out; | |
629 | ||
630 | if (pte_write(*ptep)) { | |
631 | pte_t entry; | |
632 | ||
633 | swapped = PageSwapCache(page); | |
634 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
635 | /* | |
636 | * Ok this is tricky, when get_user_pages_fast() run it doesnt | |
637 | * take any lock, therefore the check that we are going to make | |
638 | * with the pagecount against the mapcount is racey and | |
639 | * O_DIRECT can happen right after the check. | |
640 | * So we clear the pte and flush the tlb before the check | |
641 | * this assure us that no O_DIRECT can happen after the check | |
642 | * or in the middle of the check. | |
643 | */ | |
644 | entry = ptep_clear_flush(vma, addr, ptep); | |
645 | /* | |
646 | * Check that no O_DIRECT or similar I/O is in progress on the | |
647 | * page | |
648 | */ | |
649 | if ((page_mapcount(page) + 2 + swapped) != page_count(page)) { | |
650 | set_pte_at_notify(mm, addr, ptep, entry); | |
651 | goto out_unlock; | |
652 | } | |
653 | entry = pte_wrprotect(entry); | |
654 | set_pte_at_notify(mm, addr, ptep, entry); | |
655 | } | |
656 | *orig_pte = *ptep; | |
657 | err = 0; | |
658 | ||
659 | out_unlock: | |
660 | pte_unmap_unlock(ptep, ptl); | |
661 | out: | |
662 | return err; | |
663 | } | |
664 | ||
665 | /** | |
666 | * replace_page - replace page in vma by new ksm page | |
667 | * @vma: vma that holds the pte pointing to oldpage | |
668 | * @oldpage: the page we are replacing by newpage | |
669 | * @newpage: the ksm page we replace oldpage by | |
670 | * @orig_pte: the original value of the pte | |
671 | * | |
672 | * Returns 0 on success, -EFAULT on failure. | |
673 | */ | |
674 | static int replace_page(struct vm_area_struct *vma, struct page *oldpage, | |
675 | struct page *newpage, pte_t orig_pte) | |
676 | { | |
677 | struct mm_struct *mm = vma->vm_mm; | |
678 | pgd_t *pgd; | |
679 | pud_t *pud; | |
680 | pmd_t *pmd; | |
681 | pte_t *ptep; | |
682 | spinlock_t *ptl; | |
683 | unsigned long addr; | |
684 | pgprot_t prot; | |
685 | int err = -EFAULT; | |
686 | ||
687 | prot = vm_get_page_prot(vma->vm_flags & ~VM_WRITE); | |
688 | ||
689 | addr = page_address_in_vma(oldpage, vma); | |
690 | if (addr == -EFAULT) | |
691 | goto out; | |
692 | ||
693 | pgd = pgd_offset(mm, addr); | |
694 | if (!pgd_present(*pgd)) | |
695 | goto out; | |
696 | ||
697 | pud = pud_offset(pgd, addr); | |
698 | if (!pud_present(*pud)) | |
699 | goto out; | |
700 | ||
701 | pmd = pmd_offset(pud, addr); | |
702 | if (!pmd_present(*pmd)) | |
703 | goto out; | |
704 | ||
705 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
706 | if (!pte_same(*ptep, orig_pte)) { | |
707 | pte_unmap_unlock(ptep, ptl); | |
708 | goto out; | |
709 | } | |
710 | ||
711 | get_page(newpage); | |
712 | page_add_ksm_rmap(newpage); | |
713 | ||
714 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
715 | ptep_clear_flush(vma, addr, ptep); | |
716 | set_pte_at_notify(mm, addr, ptep, mk_pte(newpage, prot)); | |
717 | ||
718 | page_remove_rmap(oldpage); | |
719 | put_page(oldpage); | |
720 | ||
721 | pte_unmap_unlock(ptep, ptl); | |
722 | err = 0; | |
723 | out: | |
724 | return err; | |
725 | } | |
726 | ||
727 | /* | |
728 | * try_to_merge_one_page - take two pages and merge them into one | |
729 | * @vma: the vma that hold the pte pointing into oldpage | |
730 | * @oldpage: the page that we want to replace with newpage | |
731 | * @newpage: the page that we want to map instead of oldpage | |
732 | * | |
733 | * Note: | |
734 | * oldpage should be a PageAnon page, while newpage should be a PageKsm page, | |
735 | * or a newly allocated kernel page which page_add_ksm_rmap will make PageKsm. | |
736 | * | |
737 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
738 | */ | |
739 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
740 | struct page *oldpage, | |
741 | struct page *newpage) | |
742 | { | |
743 | pte_t orig_pte = __pte(0); | |
744 | int err = -EFAULT; | |
745 | ||
746 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
747 | goto out; | |
748 | ||
749 | if (!PageAnon(oldpage)) | |
750 | goto out; | |
751 | ||
752 | get_page(newpage); | |
753 | get_page(oldpage); | |
754 | ||
755 | /* | |
756 | * We need the page lock to read a stable PageSwapCache in | |
757 | * write_protect_page(). We use trylock_page() instead of | |
758 | * lock_page() because we don't want to wait here - we | |
759 | * prefer to continue scanning and merging different pages, | |
760 | * then come back to this page when it is unlocked. | |
761 | */ | |
762 | if (!trylock_page(oldpage)) | |
763 | goto out_putpage; | |
764 | /* | |
765 | * If this anonymous page is mapped only here, its pte may need | |
766 | * to be write-protected. If it's mapped elsewhere, all of its | |
767 | * ptes are necessarily already write-protected. But in either | |
768 | * case, we need to lock and check page_count is not raised. | |
769 | */ | |
770 | if (write_protect_page(vma, oldpage, &orig_pte)) { | |
771 | unlock_page(oldpage); | |
772 | goto out_putpage; | |
773 | } | |
774 | unlock_page(oldpage); | |
775 | ||
776 | if (pages_identical(oldpage, newpage)) | |
777 | err = replace_page(vma, oldpage, newpage, orig_pte); | |
778 | ||
779 | out_putpage: | |
780 | put_page(oldpage); | |
781 | put_page(newpage); | |
782 | out: | |
783 | return err; | |
784 | } | |
785 | ||
81464e30 HD |
786 | /* |
787 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
788 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
789 | */ | |
790 | static int try_to_merge_with_ksm_page(struct mm_struct *mm1, | |
791 | unsigned long addr1, | |
792 | struct page *page1, | |
793 | struct page *kpage) | |
794 | { | |
795 | struct vm_area_struct *vma; | |
796 | int err = -EFAULT; | |
797 | ||
798 | down_read(&mm1->mmap_sem); | |
9ba69294 HD |
799 | if (ksm_test_exit(mm1)) |
800 | goto out; | |
801 | ||
81464e30 HD |
802 | vma = find_vma(mm1, addr1); |
803 | if (!vma || vma->vm_start > addr1) | |
804 | goto out; | |
805 | ||
806 | err = try_to_merge_one_page(vma, page1, kpage); | |
807 | out: | |
808 | up_read(&mm1->mmap_sem); | |
809 | return err; | |
810 | } | |
811 | ||
31dbd01f IE |
812 | /* |
813 | * try_to_merge_two_pages - take two identical pages and prepare them | |
814 | * to be merged into one page. | |
815 | * | |
816 | * This function returns 0 if we successfully mapped two identical pages | |
817 | * into one page, -EFAULT otherwise. | |
818 | * | |
819 | * Note that this function allocates a new kernel page: if one of the pages | |
820 | * is already a ksm page, try_to_merge_with_ksm_page should be used. | |
821 | */ | |
822 | static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1, | |
823 | struct page *page1, struct mm_struct *mm2, | |
824 | unsigned long addr2, struct page *page2) | |
825 | { | |
826 | struct vm_area_struct *vma; | |
827 | struct page *kpage; | |
828 | int err = -EFAULT; | |
829 | ||
830 | /* | |
831 | * The number of nodes in the stable tree | |
832 | * is the number of kernel pages that we hold. | |
833 | */ | |
834 | if (ksm_max_kernel_pages && | |
b4028260 | 835 | ksm_max_kernel_pages <= ksm_pages_shared) |
31dbd01f IE |
836 | return err; |
837 | ||
838 | kpage = alloc_page(GFP_HIGHUSER); | |
839 | if (!kpage) | |
840 | return err; | |
841 | ||
842 | down_read(&mm1->mmap_sem); | |
9ba69294 HD |
843 | if (ksm_test_exit(mm1)) { |
844 | up_read(&mm1->mmap_sem); | |
845 | goto out; | |
846 | } | |
31dbd01f IE |
847 | vma = find_vma(mm1, addr1); |
848 | if (!vma || vma->vm_start > addr1) { | |
31dbd01f | 849 | up_read(&mm1->mmap_sem); |
81464e30 | 850 | goto out; |
31dbd01f IE |
851 | } |
852 | ||
853 | copy_user_highpage(kpage, page1, addr1, vma); | |
854 | err = try_to_merge_one_page(vma, page1, kpage); | |
855 | up_read(&mm1->mmap_sem); | |
856 | ||
857 | if (!err) { | |
81464e30 | 858 | err = try_to_merge_with_ksm_page(mm2, addr2, page2, kpage); |
31dbd01f | 859 | /* |
81464e30 HD |
860 | * If that fails, we have a ksm page with only one pte |
861 | * pointing to it: so break it. | |
31dbd01f IE |
862 | */ |
863 | if (err) | |
864 | break_cow(mm1, addr1); | |
31dbd01f | 865 | } |
81464e30 | 866 | out: |
31dbd01f IE |
867 | put_page(kpage); |
868 | return err; | |
869 | } | |
870 | ||
31dbd01f IE |
871 | /* |
872 | * stable_tree_search - search page inside the stable tree | |
873 | * @page: the page that we are searching identical pages to. | |
874 | * @page2: pointer into identical page that we are holding inside the stable | |
875 | * tree that we have found. | |
876 | * @rmap_item: the reverse mapping item | |
877 | * | |
878 | * This function checks if there is a page inside the stable tree | |
879 | * with identical content to the page that we are scanning right now. | |
880 | * | |
881 | * This function return rmap_item pointer to the identical item if found, | |
882 | * NULL otherwise. | |
883 | */ | |
884 | static struct rmap_item *stable_tree_search(struct page *page, | |
885 | struct page **page2, | |
886 | struct rmap_item *rmap_item) | |
887 | { | |
888 | struct rb_node *node = root_stable_tree.rb_node; | |
889 | ||
890 | while (node) { | |
891 | struct rmap_item *tree_rmap_item, *next_rmap_item; | |
892 | int ret; | |
893 | ||
894 | tree_rmap_item = rb_entry(node, struct rmap_item, node); | |
895 | while (tree_rmap_item) { | |
896 | BUG_ON(!in_stable_tree(tree_rmap_item)); | |
897 | cond_resched(); | |
898 | page2[0] = get_ksm_page(tree_rmap_item); | |
899 | if (page2[0]) | |
900 | break; | |
901 | next_rmap_item = tree_rmap_item->next; | |
902 | remove_rmap_item_from_tree(tree_rmap_item); | |
903 | tree_rmap_item = next_rmap_item; | |
904 | } | |
905 | if (!tree_rmap_item) | |
906 | return NULL; | |
907 | ||
908 | ret = memcmp_pages(page, page2[0]); | |
909 | ||
910 | if (ret < 0) { | |
911 | put_page(page2[0]); | |
912 | node = node->rb_left; | |
913 | } else if (ret > 0) { | |
914 | put_page(page2[0]); | |
915 | node = node->rb_right; | |
916 | } else { | |
917 | return tree_rmap_item; | |
918 | } | |
919 | } | |
920 | ||
921 | return NULL; | |
922 | } | |
923 | ||
924 | /* | |
925 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
926 | * into the stable tree. | |
927 | * | |
928 | * @page: the page that we are searching identical page to inside the stable | |
929 | * tree. | |
930 | * @rmap_item: pointer to the reverse mapping item. | |
931 | * | |
932 | * This function returns rmap_item if success, NULL otherwise. | |
933 | */ | |
934 | static struct rmap_item *stable_tree_insert(struct page *page, | |
935 | struct rmap_item *rmap_item) | |
936 | { | |
937 | struct rb_node **new = &root_stable_tree.rb_node; | |
938 | struct rb_node *parent = NULL; | |
939 | ||
940 | while (*new) { | |
941 | struct rmap_item *tree_rmap_item, *next_rmap_item; | |
942 | struct page *tree_page; | |
943 | int ret; | |
944 | ||
945 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); | |
946 | while (tree_rmap_item) { | |
947 | BUG_ON(!in_stable_tree(tree_rmap_item)); | |
948 | cond_resched(); | |
949 | tree_page = get_ksm_page(tree_rmap_item); | |
950 | if (tree_page) | |
951 | break; | |
952 | next_rmap_item = tree_rmap_item->next; | |
953 | remove_rmap_item_from_tree(tree_rmap_item); | |
954 | tree_rmap_item = next_rmap_item; | |
955 | } | |
956 | if (!tree_rmap_item) | |
957 | return NULL; | |
958 | ||
959 | ret = memcmp_pages(page, tree_page); | |
960 | put_page(tree_page); | |
961 | ||
962 | parent = *new; | |
963 | if (ret < 0) | |
964 | new = &parent->rb_left; | |
965 | else if (ret > 0) | |
966 | new = &parent->rb_right; | |
967 | else { | |
968 | /* | |
969 | * It is not a bug that stable_tree_search() didn't | |
970 | * find this node: because at that time our page was | |
971 | * not yet write-protected, so may have changed since. | |
972 | */ | |
973 | return NULL; | |
974 | } | |
975 | } | |
976 | ||
31dbd01f IE |
977 | rmap_item->address |= NODE_FLAG | STABLE_FLAG; |
978 | rmap_item->next = NULL; | |
979 | rb_link_node(&rmap_item->node, parent, new); | |
980 | rb_insert_color(&rmap_item->node, &root_stable_tree); | |
981 | ||
e178dfde | 982 | ksm_pages_shared++; |
31dbd01f IE |
983 | return rmap_item; |
984 | } | |
985 | ||
986 | /* | |
987 | * unstable_tree_search_insert - search and insert items into the unstable tree. | |
988 | * | |
989 | * @page: the page that we are going to search for identical page or to insert | |
990 | * into the unstable tree | |
991 | * @page2: pointer into identical page that was found inside the unstable tree | |
992 | * @rmap_item: the reverse mapping item of page | |
993 | * | |
994 | * This function searches for a page in the unstable tree identical to the | |
995 | * page currently being scanned; and if no identical page is found in the | |
996 | * tree, we insert rmap_item as a new object into the unstable tree. | |
997 | * | |
998 | * This function returns pointer to rmap_item found to be identical | |
999 | * to the currently scanned page, NULL otherwise. | |
1000 | * | |
1001 | * This function does both searching and inserting, because they share | |
1002 | * the same walking algorithm in an rbtree. | |
1003 | */ | |
1004 | static struct rmap_item *unstable_tree_search_insert(struct page *page, | |
1005 | struct page **page2, | |
1006 | struct rmap_item *rmap_item) | |
1007 | { | |
1008 | struct rb_node **new = &root_unstable_tree.rb_node; | |
1009 | struct rb_node *parent = NULL; | |
1010 | ||
1011 | while (*new) { | |
1012 | struct rmap_item *tree_rmap_item; | |
1013 | int ret; | |
1014 | ||
1015 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); | |
1016 | page2[0] = get_mergeable_page(tree_rmap_item); | |
1017 | if (!page2[0]) | |
1018 | return NULL; | |
1019 | ||
1020 | /* | |
1021 | * Don't substitute an unswappable ksm page | |
1022 | * just for one good swappable forked page. | |
1023 | */ | |
1024 | if (page == page2[0]) { | |
1025 | put_page(page2[0]); | |
1026 | return NULL; | |
1027 | } | |
1028 | ||
1029 | ret = memcmp_pages(page, page2[0]); | |
1030 | ||
1031 | parent = *new; | |
1032 | if (ret < 0) { | |
1033 | put_page(page2[0]); | |
1034 | new = &parent->rb_left; | |
1035 | } else if (ret > 0) { | |
1036 | put_page(page2[0]); | |
1037 | new = &parent->rb_right; | |
1038 | } else { | |
1039 | return tree_rmap_item; | |
1040 | } | |
1041 | } | |
1042 | ||
1043 | rmap_item->address |= NODE_FLAG; | |
1044 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); | |
1045 | rb_link_node(&rmap_item->node, parent, new); | |
1046 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1047 | ||
473b0ce4 | 1048 | ksm_pages_unshared++; |
31dbd01f IE |
1049 | return NULL; |
1050 | } | |
1051 | ||
1052 | /* | |
1053 | * stable_tree_append - add another rmap_item to the linked list of | |
1054 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1055 | * the same ksm page. | |
1056 | */ | |
1057 | static void stable_tree_append(struct rmap_item *rmap_item, | |
1058 | struct rmap_item *tree_rmap_item) | |
1059 | { | |
1060 | rmap_item->next = tree_rmap_item->next; | |
1061 | rmap_item->prev = tree_rmap_item; | |
1062 | ||
1063 | if (tree_rmap_item->next) | |
1064 | tree_rmap_item->next->prev = rmap_item; | |
1065 | ||
1066 | tree_rmap_item->next = rmap_item; | |
1067 | rmap_item->address |= STABLE_FLAG; | |
e178dfde HD |
1068 | |
1069 | ksm_pages_sharing++; | |
31dbd01f IE |
1070 | } |
1071 | ||
1072 | /* | |
81464e30 HD |
1073 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1074 | * if not, compare checksum to previous and if it's the same, see if page can | |
1075 | * be inserted into the unstable tree, or merged with a page already there and | |
1076 | * both transferred to the stable tree. | |
31dbd01f IE |
1077 | * |
1078 | * @page: the page that we are searching identical page to. | |
1079 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1080 | */ | |
1081 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1082 | { | |
1083 | struct page *page2[1]; | |
1084 | struct rmap_item *tree_rmap_item; | |
1085 | unsigned int checksum; | |
1086 | int err; | |
1087 | ||
1088 | if (in_stable_tree(rmap_item)) | |
1089 | remove_rmap_item_from_tree(rmap_item); | |
1090 | ||
1091 | /* We first start with searching the page inside the stable tree */ | |
1092 | tree_rmap_item = stable_tree_search(page, page2, rmap_item); | |
1093 | if (tree_rmap_item) { | |
e178dfde | 1094 | if (page == page2[0]) /* forked */ |
31dbd01f | 1095 | err = 0; |
e178dfde | 1096 | else |
31dbd01f IE |
1097 | err = try_to_merge_with_ksm_page(rmap_item->mm, |
1098 | rmap_item->address, | |
1099 | page, page2[0]); | |
1100 | put_page(page2[0]); | |
1101 | ||
1102 | if (!err) { | |
1103 | /* | |
1104 | * The page was successfully merged: | |
1105 | * add its rmap_item to the stable tree. | |
1106 | */ | |
1107 | stable_tree_append(rmap_item, tree_rmap_item); | |
1108 | } | |
1109 | return; | |
1110 | } | |
1111 | ||
1112 | /* | |
1113 | * A ksm page might have got here by fork, but its other | |
1114 | * references have already been removed from the stable tree. | |
d952b791 HD |
1115 | * Or it might be left over from a break_ksm which failed |
1116 | * when the mem_cgroup had reached its limit: try again now. | |
31dbd01f IE |
1117 | */ |
1118 | if (PageKsm(page)) | |
1119 | break_cow(rmap_item->mm, rmap_item->address); | |
1120 | ||
1121 | /* | |
1122 | * In case the hash value of the page was changed from the last time we | |
1123 | * have calculated it, this page to be changed frequely, therefore we | |
1124 | * don't want to insert it to the unstable tree, and we don't want to | |
1125 | * waste our time to search if there is something identical to it there. | |
1126 | */ | |
1127 | checksum = calc_checksum(page); | |
1128 | if (rmap_item->oldchecksum != checksum) { | |
1129 | rmap_item->oldchecksum = checksum; | |
1130 | return; | |
1131 | } | |
1132 | ||
1133 | tree_rmap_item = unstable_tree_search_insert(page, page2, rmap_item); | |
1134 | if (tree_rmap_item) { | |
1135 | err = try_to_merge_two_pages(rmap_item->mm, | |
1136 | rmap_item->address, page, | |
1137 | tree_rmap_item->mm, | |
1138 | tree_rmap_item->address, page2[0]); | |
1139 | /* | |
1140 | * As soon as we merge this page, we want to remove the | |
1141 | * rmap_item of the page we have merged with from the unstable | |
1142 | * tree, and insert it instead as new node in the stable tree. | |
1143 | */ | |
1144 | if (!err) { | |
1145 | rb_erase(&tree_rmap_item->node, &root_unstable_tree); | |
1146 | tree_rmap_item->address &= ~NODE_FLAG; | |
473b0ce4 HD |
1147 | ksm_pages_unshared--; |
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 | */ | |
1155 | if (stable_tree_insert(page2[0], tree_rmap_item)) | |
1156 | stable_tree_append(rmap_item, tree_rmap_item); | |
1157 | else { | |
1158 | break_cow(tree_rmap_item->mm, | |
1159 | tree_rmap_item->address); | |
1160 | break_cow(rmap_item->mm, rmap_item->address); | |
31dbd01f IE |
1161 | } |
1162 | } | |
1163 | ||
1164 | put_page(page2[0]); | |
1165 | } | |
1166 | } | |
1167 | ||
1168 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
1169 | struct list_head *cur, | |
1170 | unsigned long addr) | |
1171 | { | |
1172 | struct rmap_item *rmap_item; | |
1173 | ||
1174 | while (cur != &mm_slot->rmap_list) { | |
1175 | rmap_item = list_entry(cur, struct rmap_item, link); | |
1176 | if ((rmap_item->address & PAGE_MASK) == addr) { | |
1177 | if (!in_stable_tree(rmap_item)) | |
1178 | remove_rmap_item_from_tree(rmap_item); | |
1179 | return rmap_item; | |
1180 | } | |
1181 | if (rmap_item->address > addr) | |
1182 | break; | |
1183 | cur = cur->next; | |
1184 | remove_rmap_item_from_tree(rmap_item); | |
1185 | list_del(&rmap_item->link); | |
1186 | free_rmap_item(rmap_item); | |
1187 | } | |
1188 | ||
1189 | rmap_item = alloc_rmap_item(); | |
1190 | if (rmap_item) { | |
1191 | /* It has already been zeroed */ | |
1192 | rmap_item->mm = mm_slot->mm; | |
1193 | rmap_item->address = addr; | |
1194 | list_add_tail(&rmap_item->link, cur); | |
1195 | } | |
1196 | return rmap_item; | |
1197 | } | |
1198 | ||
1199 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1200 | { | |
1201 | struct mm_struct *mm; | |
1202 | struct mm_slot *slot; | |
1203 | struct vm_area_struct *vma; | |
1204 | struct rmap_item *rmap_item; | |
1205 | ||
1206 | if (list_empty(&ksm_mm_head.mm_list)) | |
1207 | return NULL; | |
1208 | ||
1209 | slot = ksm_scan.mm_slot; | |
1210 | if (slot == &ksm_mm_head) { | |
1211 | root_unstable_tree = RB_ROOT; | |
1212 | ||
1213 | spin_lock(&ksm_mmlist_lock); | |
1214 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1215 | ksm_scan.mm_slot = slot; | |
1216 | spin_unlock(&ksm_mmlist_lock); | |
1217 | next_mm: | |
1218 | ksm_scan.address = 0; | |
1219 | ksm_scan.rmap_item = list_entry(&slot->rmap_list, | |
1220 | struct rmap_item, link); | |
1221 | } | |
1222 | ||
1223 | mm = slot->mm; | |
1224 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1225 | if (ksm_test_exit(mm)) |
1226 | vma = NULL; | |
1227 | else | |
1228 | vma = find_vma(mm, ksm_scan.address); | |
1229 | ||
1230 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1231 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1232 | continue; | |
1233 | if (ksm_scan.address < vma->vm_start) | |
1234 | ksm_scan.address = vma->vm_start; | |
1235 | if (!vma->anon_vma) | |
1236 | ksm_scan.address = vma->vm_end; | |
1237 | ||
1238 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1239 | if (ksm_test_exit(mm)) |
1240 | break; | |
31dbd01f IE |
1241 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
1242 | if (*page && PageAnon(*page)) { | |
1243 | flush_anon_page(vma, *page, ksm_scan.address); | |
1244 | flush_dcache_page(*page); | |
1245 | rmap_item = get_next_rmap_item(slot, | |
1246 | ksm_scan.rmap_item->link.next, | |
1247 | ksm_scan.address); | |
1248 | if (rmap_item) { | |
1249 | ksm_scan.rmap_item = rmap_item; | |
1250 | ksm_scan.address += PAGE_SIZE; | |
1251 | } else | |
1252 | put_page(*page); | |
1253 | up_read(&mm->mmap_sem); | |
1254 | return rmap_item; | |
1255 | } | |
1256 | if (*page) | |
1257 | put_page(*page); | |
1258 | ksm_scan.address += PAGE_SIZE; | |
1259 | cond_resched(); | |
1260 | } | |
1261 | } | |
1262 | ||
9ba69294 HD |
1263 | if (ksm_test_exit(mm)) { |
1264 | ksm_scan.address = 0; | |
1265 | ksm_scan.rmap_item = list_entry(&slot->rmap_list, | |
1266 | struct rmap_item, link); | |
1267 | } | |
31dbd01f IE |
1268 | /* |
1269 | * Nuke all the rmap_items that are above this current rmap: | |
1270 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1271 | */ | |
1272 | remove_trailing_rmap_items(slot, ksm_scan.rmap_item->link.next); | |
31dbd01f IE |
1273 | |
1274 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1275 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1276 | struct mm_slot, mm_list); | |
1277 | if (ksm_scan.address == 0) { | |
1278 | /* | |
1279 | * We've completed a full scan of all vmas, holding mmap_sem | |
1280 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1281 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1282 | * This applies either when cleaning up after __ksm_exit |
1283 | * (but beware: we can reach here even before __ksm_exit), | |
1284 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1285 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1286 | */ |
1287 | hlist_del(&slot->link); | |
1288 | list_del(&slot->mm_list); | |
9ba69294 HD |
1289 | spin_unlock(&ksm_mmlist_lock); |
1290 | ||
cd551f97 HD |
1291 | free_mm_slot(slot); |
1292 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1293 | up_read(&mm->mmap_sem); |
1294 | mmdrop(mm); | |
1295 | } else { | |
1296 | spin_unlock(&ksm_mmlist_lock); | |
1297 | up_read(&mm->mmap_sem); | |
cd551f97 | 1298 | } |
31dbd01f IE |
1299 | |
1300 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1301 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1302 | if (slot != &ksm_mm_head) |
1303 | goto next_mm; | |
1304 | ||
31dbd01f IE |
1305 | ksm_scan.seqnr++; |
1306 | return NULL; | |
1307 | } | |
1308 | ||
1309 | /** | |
1310 | * ksm_do_scan - the ksm scanner main worker function. | |
1311 | * @scan_npages - number of pages we want to scan before we return. | |
1312 | */ | |
1313 | static void ksm_do_scan(unsigned int scan_npages) | |
1314 | { | |
1315 | struct rmap_item *rmap_item; | |
1316 | struct page *page; | |
1317 | ||
1318 | while (scan_npages--) { | |
1319 | cond_resched(); | |
1320 | rmap_item = scan_get_next_rmap_item(&page); | |
1321 | if (!rmap_item) | |
1322 | return; | |
1323 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1324 | cmp_and_merge_page(page, rmap_item); | |
26465d3e HD |
1325 | else if (page_mapcount(page) == 1) { |
1326 | /* | |
1327 | * Replace now-unshared ksm page by ordinary page. | |
1328 | */ | |
1329 | break_cow(rmap_item->mm, rmap_item->address); | |
1330 | remove_rmap_item_from_tree(rmap_item); | |
1331 | rmap_item->oldchecksum = calc_checksum(page); | |
1332 | } | |
31dbd01f IE |
1333 | put_page(page); |
1334 | } | |
1335 | } | |
1336 | ||
6e158384 HD |
1337 | static int ksmd_should_run(void) |
1338 | { | |
1339 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1340 | } | |
1341 | ||
31dbd01f IE |
1342 | static int ksm_scan_thread(void *nothing) |
1343 | { | |
339aa624 | 1344 | set_user_nice(current, 5); |
31dbd01f IE |
1345 | |
1346 | while (!kthread_should_stop()) { | |
6e158384 HD |
1347 | mutex_lock(&ksm_thread_mutex); |
1348 | if (ksmd_should_run()) | |
31dbd01f | 1349 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1350 | mutex_unlock(&ksm_thread_mutex); |
1351 | ||
1352 | if (ksmd_should_run()) { | |
31dbd01f IE |
1353 | schedule_timeout_interruptible( |
1354 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1355 | } else { | |
1356 | wait_event_interruptible(ksm_thread_wait, | |
6e158384 | 1357 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1358 | } |
1359 | } | |
1360 | return 0; | |
1361 | } | |
1362 | ||
f8af4da3 HD |
1363 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1364 | unsigned long end, int advice, unsigned long *vm_flags) | |
1365 | { | |
1366 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1367 | int err; |
f8af4da3 HD |
1368 | |
1369 | switch (advice) { | |
1370 | case MADV_MERGEABLE: | |
1371 | /* | |
1372 | * Be somewhat over-protective for now! | |
1373 | */ | |
1374 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1375 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1376 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
1377 | VM_MIXEDMAP | VM_SAO)) | |
1378 | return 0; /* just ignore the advice */ | |
1379 | ||
d952b791 HD |
1380 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1381 | err = __ksm_enter(mm); | |
1382 | if (err) | |
1383 | return err; | |
1384 | } | |
f8af4da3 HD |
1385 | |
1386 | *vm_flags |= VM_MERGEABLE; | |
1387 | break; | |
1388 | ||
1389 | case MADV_UNMERGEABLE: | |
1390 | if (!(*vm_flags & VM_MERGEABLE)) | |
1391 | return 0; /* just ignore the advice */ | |
1392 | ||
d952b791 HD |
1393 | if (vma->anon_vma) { |
1394 | err = unmerge_ksm_pages(vma, start, end); | |
1395 | if (err) | |
1396 | return err; | |
1397 | } | |
f8af4da3 HD |
1398 | |
1399 | *vm_flags &= ~VM_MERGEABLE; | |
1400 | break; | |
1401 | } | |
1402 | ||
1403 | return 0; | |
1404 | } | |
1405 | ||
1406 | int __ksm_enter(struct mm_struct *mm) | |
1407 | { | |
6e158384 HD |
1408 | struct mm_slot *mm_slot; |
1409 | int needs_wakeup; | |
1410 | ||
1411 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1412 | if (!mm_slot) |
1413 | return -ENOMEM; | |
1414 | ||
6e158384 HD |
1415 | /* Check ksm_run too? Would need tighter locking */ |
1416 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1417 | ||
31dbd01f IE |
1418 | spin_lock(&ksm_mmlist_lock); |
1419 | insert_to_mm_slots_hash(mm, mm_slot); | |
1420 | /* | |
1421 | * Insert just behind the scanning cursor, to let the area settle | |
1422 | * down a little; when fork is followed by immediate exec, we don't | |
1423 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1424 | */ | |
1425 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1426 | spin_unlock(&ksm_mmlist_lock); | |
1427 | ||
f8af4da3 | 1428 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1429 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1430 | |
1431 | if (needs_wakeup) | |
1432 | wake_up_interruptible(&ksm_thread_wait); | |
1433 | ||
f8af4da3 HD |
1434 | return 0; |
1435 | } | |
1436 | ||
1c2fb7a4 | 1437 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1438 | { |
cd551f97 | 1439 | struct mm_slot *mm_slot; |
9ba69294 | 1440 | int easy_to_free = 0; |
cd551f97 | 1441 | |
31dbd01f | 1442 | /* |
9ba69294 HD |
1443 | * This process is exiting: if it's straightforward (as is the |
1444 | * case when ksmd was never running), free mm_slot immediately. | |
1445 | * But if it's at the cursor or has rmap_items linked to it, use | |
1446 | * mmap_sem to synchronize with any break_cows before pagetables | |
1447 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1448 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1449 | */ |
9ba69294 | 1450 | |
cd551f97 HD |
1451 | spin_lock(&ksm_mmlist_lock); |
1452 | mm_slot = get_mm_slot(mm); | |
9ba69294 HD |
1453 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
1454 | if (list_empty(&mm_slot->rmap_list)) { | |
1455 | hlist_del(&mm_slot->link); | |
1456 | list_del(&mm_slot->mm_list); | |
1457 | easy_to_free = 1; | |
1458 | } else { | |
1459 | list_move(&mm_slot->mm_list, | |
1460 | &ksm_scan.mm_slot->mm_list); | |
1461 | } | |
cd551f97 | 1462 | } |
cd551f97 HD |
1463 | spin_unlock(&ksm_mmlist_lock); |
1464 | ||
9ba69294 HD |
1465 | if (easy_to_free) { |
1466 | free_mm_slot(mm_slot); | |
1467 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1468 | mmdrop(mm); | |
1469 | } else if (mm_slot) { | |
9ba69294 HD |
1470 | down_write(&mm->mmap_sem); |
1471 | up_write(&mm->mmap_sem); | |
9ba69294 | 1472 | } |
31dbd01f IE |
1473 | } |
1474 | ||
2ffd8679 HD |
1475 | #ifdef CONFIG_SYSFS |
1476 | /* | |
1477 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1478 | */ | |
1479 | ||
31dbd01f IE |
1480 | #define KSM_ATTR_RO(_name) \ |
1481 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1482 | #define KSM_ATTR(_name) \ | |
1483 | static struct kobj_attribute _name##_attr = \ | |
1484 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1485 | ||
1486 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1487 | struct kobj_attribute *attr, char *buf) | |
1488 | { | |
1489 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1490 | } | |
1491 | ||
1492 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1493 | struct kobj_attribute *attr, | |
1494 | const char *buf, size_t count) | |
1495 | { | |
1496 | unsigned long msecs; | |
1497 | int err; | |
1498 | ||
1499 | err = strict_strtoul(buf, 10, &msecs); | |
1500 | if (err || msecs > UINT_MAX) | |
1501 | return -EINVAL; | |
1502 | ||
1503 | ksm_thread_sleep_millisecs = msecs; | |
1504 | ||
1505 | return count; | |
1506 | } | |
1507 | KSM_ATTR(sleep_millisecs); | |
1508 | ||
1509 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1510 | struct kobj_attribute *attr, char *buf) | |
1511 | { | |
1512 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1513 | } | |
1514 | ||
1515 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1516 | struct kobj_attribute *attr, | |
1517 | const char *buf, size_t count) | |
1518 | { | |
1519 | int err; | |
1520 | unsigned long nr_pages; | |
1521 | ||
1522 | err = strict_strtoul(buf, 10, &nr_pages); | |
1523 | if (err || nr_pages > UINT_MAX) | |
1524 | return -EINVAL; | |
1525 | ||
1526 | ksm_thread_pages_to_scan = nr_pages; | |
1527 | ||
1528 | return count; | |
1529 | } | |
1530 | KSM_ATTR(pages_to_scan); | |
1531 | ||
1532 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1533 | char *buf) | |
1534 | { | |
1535 | return sprintf(buf, "%u\n", ksm_run); | |
1536 | } | |
1537 | ||
1538 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1539 | const char *buf, size_t count) | |
1540 | { | |
1541 | int err; | |
1542 | unsigned long flags; | |
1543 | ||
1544 | err = strict_strtoul(buf, 10, &flags); | |
1545 | if (err || flags > UINT_MAX) | |
1546 | return -EINVAL; | |
1547 | if (flags > KSM_RUN_UNMERGE) | |
1548 | return -EINVAL; | |
1549 | ||
1550 | /* | |
1551 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1552 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
b4028260 | 1553 | * breaking COW to free the unswappable pages_shared (but leaves |
31dbd01f IE |
1554 | * mm_slots on the list for when ksmd may be set running again). |
1555 | */ | |
1556 | ||
1557 | mutex_lock(&ksm_thread_mutex); | |
1558 | if (ksm_run != flags) { | |
1559 | ksm_run = flags; | |
d952b791 | 1560 | if (flags & KSM_RUN_UNMERGE) { |
35451bee | 1561 | current->flags |= PF_OOM_ORIGIN; |
d952b791 | 1562 | err = unmerge_and_remove_all_rmap_items(); |
35451bee | 1563 | current->flags &= ~PF_OOM_ORIGIN; |
d952b791 HD |
1564 | if (err) { |
1565 | ksm_run = KSM_RUN_STOP; | |
1566 | count = err; | |
1567 | } | |
1568 | } | |
31dbd01f IE |
1569 | } |
1570 | mutex_unlock(&ksm_thread_mutex); | |
1571 | ||
1572 | if (flags & KSM_RUN_MERGE) | |
1573 | wake_up_interruptible(&ksm_thread_wait); | |
1574 | ||
1575 | return count; | |
1576 | } | |
1577 | KSM_ATTR(run); | |
1578 | ||
31dbd01f IE |
1579 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
1580 | struct kobj_attribute *attr, | |
1581 | const char *buf, size_t count) | |
1582 | { | |
1583 | int err; | |
1584 | unsigned long nr_pages; | |
1585 | ||
1586 | err = strict_strtoul(buf, 10, &nr_pages); | |
1587 | if (err) | |
1588 | return -EINVAL; | |
1589 | ||
1590 | ksm_max_kernel_pages = nr_pages; | |
1591 | ||
1592 | return count; | |
1593 | } | |
1594 | ||
1595 | static ssize_t max_kernel_pages_show(struct kobject *kobj, | |
1596 | struct kobj_attribute *attr, char *buf) | |
1597 | { | |
1598 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); | |
1599 | } | |
1600 | KSM_ATTR(max_kernel_pages); | |
1601 | ||
b4028260 HD |
1602 | static ssize_t pages_shared_show(struct kobject *kobj, |
1603 | struct kobj_attribute *attr, char *buf) | |
1604 | { | |
1605 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1606 | } | |
1607 | KSM_ATTR_RO(pages_shared); | |
1608 | ||
1609 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1610 | struct kobj_attribute *attr, char *buf) | |
1611 | { | |
e178dfde | 1612 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1613 | } |
1614 | KSM_ATTR_RO(pages_sharing); | |
1615 | ||
473b0ce4 HD |
1616 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1617 | struct kobj_attribute *attr, char *buf) | |
1618 | { | |
1619 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1620 | } | |
1621 | KSM_ATTR_RO(pages_unshared); | |
1622 | ||
1623 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1624 | struct kobj_attribute *attr, char *buf) | |
1625 | { | |
1626 | long ksm_pages_volatile; | |
1627 | ||
1628 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1629 | - ksm_pages_sharing - ksm_pages_unshared; | |
1630 | /* | |
1631 | * It was not worth any locking to calculate that statistic, | |
1632 | * but it might therefore sometimes be negative: conceal that. | |
1633 | */ | |
1634 | if (ksm_pages_volatile < 0) | |
1635 | ksm_pages_volatile = 0; | |
1636 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1637 | } | |
1638 | KSM_ATTR_RO(pages_volatile); | |
1639 | ||
1640 | static ssize_t full_scans_show(struct kobject *kobj, | |
1641 | struct kobj_attribute *attr, char *buf) | |
1642 | { | |
1643 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1644 | } | |
1645 | KSM_ATTR_RO(full_scans); | |
1646 | ||
31dbd01f IE |
1647 | static struct attribute *ksm_attrs[] = { |
1648 | &sleep_millisecs_attr.attr, | |
1649 | &pages_to_scan_attr.attr, | |
1650 | &run_attr.attr, | |
31dbd01f | 1651 | &max_kernel_pages_attr.attr, |
b4028260 HD |
1652 | &pages_shared_attr.attr, |
1653 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1654 | &pages_unshared_attr.attr, |
1655 | &pages_volatile_attr.attr, | |
1656 | &full_scans_attr.attr, | |
31dbd01f IE |
1657 | NULL, |
1658 | }; | |
1659 | ||
1660 | static struct attribute_group ksm_attr_group = { | |
1661 | .attrs = ksm_attrs, | |
1662 | .name = "ksm", | |
1663 | }; | |
2ffd8679 | 1664 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1665 | |
1666 | static int __init ksm_init(void) | |
1667 | { | |
1668 | struct task_struct *ksm_thread; | |
1669 | int err; | |
1670 | ||
c73602ad | 1671 | ksm_max_kernel_pages = totalram_pages / 4; |
2c6854fd | 1672 | |
31dbd01f IE |
1673 | err = ksm_slab_init(); |
1674 | if (err) | |
1675 | goto out; | |
1676 | ||
1677 | err = mm_slots_hash_init(); | |
1678 | if (err) | |
1679 | goto out_free1; | |
1680 | ||
1681 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); | |
1682 | if (IS_ERR(ksm_thread)) { | |
1683 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
1684 | err = PTR_ERR(ksm_thread); | |
1685 | goto out_free2; | |
1686 | } | |
1687 | ||
2ffd8679 | 1688 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
1689 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
1690 | if (err) { | |
1691 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 HD |
1692 | kthread_stop(ksm_thread); |
1693 | goto out_free2; | |
31dbd01f | 1694 | } |
c73602ad HD |
1695 | #else |
1696 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
1697 | ||
2ffd8679 | 1698 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1699 | |
1700 | return 0; | |
1701 | ||
31dbd01f IE |
1702 | out_free2: |
1703 | mm_slots_hash_free(); | |
1704 | out_free1: | |
1705 | ksm_slab_free(); | |
1706 | out: | |
1707 | return err; | |
f8af4da3 | 1708 | } |
31dbd01f | 1709 | module_init(ksm_init) |