Commit | Line | Data |
---|---|---|
f8af4da3 | 1 | /* |
31dbd01f IE |
2 | * Memory merging support. |
3 | * | |
4 | * This code enables dynamic sharing of identical pages found in different | |
5 | * memory areas, even if they are not shared by fork() | |
6 | * | |
36b2528d | 7 | * Copyright (C) 2008-2009 Red Hat, Inc. |
31dbd01f IE |
8 | * Authors: |
9 | * Izik Eidus | |
10 | * Andrea Arcangeli | |
11 | * Chris Wright | |
36b2528d | 12 | * Hugh Dickins |
31dbd01f IE |
13 | * |
14 | * This work is licensed under the terms of the GNU GPL, version 2. | |
f8af4da3 HD |
15 | */ |
16 | ||
17 | #include <linux/errno.h> | |
31dbd01f IE |
18 | #include <linux/mm.h> |
19 | #include <linux/fs.h> | |
f8af4da3 | 20 | #include <linux/mman.h> |
31dbd01f IE |
21 | #include <linux/sched.h> |
22 | #include <linux/rwsem.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/rmap.h> | |
25 | #include <linux/spinlock.h> | |
26 | #include <linux/jhash.h> | |
27 | #include <linux/delay.h> | |
28 | #include <linux/kthread.h> | |
29 | #include <linux/wait.h> | |
30 | #include <linux/slab.h> | |
31 | #include <linux/rbtree.h> | |
32 | #include <linux/mmu_notifier.h> | |
2c6854fd | 33 | #include <linux/swap.h> |
f8af4da3 HD |
34 | #include <linux/ksm.h> |
35 | ||
31dbd01f IE |
36 | #include <asm/tlbflush.h> |
37 | ||
38 | /* | |
39 | * A few notes about the KSM scanning process, | |
40 | * to make it easier to understand the data structures below: | |
41 | * | |
42 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
43 | * contents into a data structure that holds pointers to the pages' locations. | |
44 | * | |
45 | * Since the contents of the pages may change at any moment, KSM cannot just | |
46 | * insert the pages into a normal sorted tree and expect it to find anything. | |
47 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
48 | * | |
49 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
50 | * by their contents. Because each such page is write-protected, searching on | |
51 | * this tree is fully assured to be working (except when pages are unmapped), | |
52 | * and therefore this tree is called the stable tree. | |
53 | * | |
54 | * In addition to the stable tree, KSM uses a second data structure called the | |
55 | * unstable tree: this tree holds pointers to pages which have been found to | |
56 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
57 | * by their contents, but since they are not write-protected, KSM cannot rely | |
58 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
59 | * be corrupted as its contents are modified, and so it is called unstable. | |
60 | * | |
61 | * KSM solves this problem by several techniques: | |
62 | * | |
63 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
64 | * memory areas, and then the tree is rebuilt again from the beginning. | |
65 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
66 | * has not changed since the previous scan of all memory areas. | |
67 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
68 | * colors of the nodes and not on their contents, assuring that even when | |
69 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
70 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
71 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
72 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
73 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
74 | * it is secured in the stable tree. (When we scan a new page, we first | |
75 | * compare it against the stable tree, and then against the unstable tree.) | |
76 | */ | |
77 | ||
78 | /** | |
79 | * struct mm_slot - ksm information per mm that is being scanned | |
80 | * @link: link to the mm_slots hash list | |
81 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 82 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
83 | * @mm: the mm that this information is valid for |
84 | */ | |
85 | struct mm_slot { | |
86 | struct hlist_node link; | |
87 | struct list_head mm_list; | |
6514d511 | 88 | struct rmap_item *rmap_list; |
31dbd01f IE |
89 | struct mm_struct *mm; |
90 | }; | |
91 | ||
92 | /** | |
93 | * struct ksm_scan - cursor for scanning | |
94 | * @mm_slot: the current mm_slot we are scanning | |
95 | * @address: the next address inside that to be scanned | |
6514d511 | 96 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
97 | * @seqnr: count of completed full scans (needed when removing unstable node) |
98 | * | |
99 | * There is only the one ksm_scan instance of this cursor structure. | |
100 | */ | |
101 | struct ksm_scan { | |
102 | struct mm_slot *mm_slot; | |
103 | unsigned long address; | |
6514d511 | 104 | struct rmap_item **rmap_list; |
31dbd01f IE |
105 | unsigned long seqnr; |
106 | }; | |
107 | ||
108 | /** | |
109 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 HD |
110 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
111 | * @filler: unused space we're making available in this patch | |
31dbd01f IE |
112 | * @mm: the memory structure this rmap_item is pointing into |
113 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
114 | * @oldchecksum: previous checksum of the page at that virtual address | |
115 | * @node: rb_node of this rmap_item in either unstable or stable tree | |
116 | * @next: next rmap_item hanging off the same node of the stable tree | |
117 | * @prev: previous rmap_item hanging off the same node of the stable tree | |
118 | */ | |
119 | struct rmap_item { | |
6514d511 HD |
120 | struct rmap_item *rmap_list; |
121 | unsigned long filler; | |
31dbd01f IE |
122 | struct mm_struct *mm; |
123 | unsigned long address; /* + low bits used for flags below */ | |
124 | union { | |
125 | unsigned int oldchecksum; /* when unstable */ | |
126 | struct rmap_item *next; /* when stable */ | |
127 | }; | |
128 | union { | |
129 | struct rb_node node; /* when tree node */ | |
130 | struct rmap_item *prev; /* in stable list */ | |
131 | }; | |
132 | }; | |
133 | ||
134 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
135 | #define NODE_FLAG 0x100 /* is a node of unstable or stable tree */ | |
136 | #define STABLE_FLAG 0x200 /* is a node or list item of stable tree */ | |
137 | ||
138 | /* The stable and unstable tree heads */ | |
139 | static struct rb_root root_stable_tree = RB_ROOT; | |
140 | static struct rb_root root_unstable_tree = RB_ROOT; | |
141 | ||
142 | #define MM_SLOTS_HASH_HEADS 1024 | |
143 | static struct hlist_head *mm_slots_hash; | |
144 | ||
145 | static struct mm_slot ksm_mm_head = { | |
146 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
147 | }; | |
148 | static struct ksm_scan ksm_scan = { | |
149 | .mm_slot = &ksm_mm_head, | |
150 | }; | |
151 | ||
152 | static struct kmem_cache *rmap_item_cache; | |
153 | static struct kmem_cache *mm_slot_cache; | |
154 | ||
155 | /* The number of nodes in the stable tree */ | |
b4028260 | 156 | static unsigned long ksm_pages_shared; |
31dbd01f | 157 | |
e178dfde | 158 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 159 | static unsigned long ksm_pages_sharing; |
31dbd01f | 160 | |
473b0ce4 HD |
161 | /* The number of nodes in the unstable tree */ |
162 | static unsigned long ksm_pages_unshared; | |
163 | ||
164 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
165 | static unsigned long ksm_rmap_items; | |
166 | ||
31dbd01f | 167 | /* Limit on the number of unswappable pages used */ |
2c6854fd | 168 | static unsigned long ksm_max_kernel_pages; |
31dbd01f IE |
169 | |
170 | /* Number of pages ksmd should scan in one batch */ | |
2c6854fd | 171 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
172 | |
173 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 174 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f IE |
175 | |
176 | #define KSM_RUN_STOP 0 | |
177 | #define KSM_RUN_MERGE 1 | |
178 | #define KSM_RUN_UNMERGE 2 | |
2c6854fd | 179 | static unsigned int ksm_run = KSM_RUN_STOP; |
31dbd01f IE |
180 | |
181 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
182 | static DEFINE_MUTEX(ksm_thread_mutex); | |
183 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
184 | ||
185 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
186 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
187 | (__flags), NULL) | |
188 | ||
189 | static int __init ksm_slab_init(void) | |
190 | { | |
191 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
192 | if (!rmap_item_cache) | |
193 | goto out; | |
194 | ||
195 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); | |
196 | if (!mm_slot_cache) | |
197 | goto out_free; | |
198 | ||
199 | return 0; | |
200 | ||
201 | out_free: | |
202 | kmem_cache_destroy(rmap_item_cache); | |
203 | out: | |
204 | return -ENOMEM; | |
205 | } | |
206 | ||
207 | static void __init ksm_slab_free(void) | |
208 | { | |
209 | kmem_cache_destroy(mm_slot_cache); | |
210 | kmem_cache_destroy(rmap_item_cache); | |
211 | mm_slot_cache = NULL; | |
212 | } | |
213 | ||
214 | static inline struct rmap_item *alloc_rmap_item(void) | |
215 | { | |
473b0ce4 HD |
216 | struct rmap_item *rmap_item; |
217 | ||
218 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
219 | if (rmap_item) | |
220 | ksm_rmap_items++; | |
221 | return rmap_item; | |
31dbd01f IE |
222 | } |
223 | ||
224 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
225 | { | |
473b0ce4 | 226 | ksm_rmap_items--; |
31dbd01f IE |
227 | rmap_item->mm = NULL; /* debug safety */ |
228 | kmem_cache_free(rmap_item_cache, rmap_item); | |
229 | } | |
230 | ||
231 | static inline struct mm_slot *alloc_mm_slot(void) | |
232 | { | |
233 | if (!mm_slot_cache) /* initialization failed */ | |
234 | return NULL; | |
235 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
236 | } | |
237 | ||
238 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
239 | { | |
240 | kmem_cache_free(mm_slot_cache, mm_slot); | |
241 | } | |
242 | ||
243 | static int __init mm_slots_hash_init(void) | |
244 | { | |
245 | mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), | |
246 | GFP_KERNEL); | |
247 | if (!mm_slots_hash) | |
248 | return -ENOMEM; | |
249 | return 0; | |
250 | } | |
251 | ||
252 | static void __init mm_slots_hash_free(void) | |
253 | { | |
254 | kfree(mm_slots_hash); | |
255 | } | |
256 | ||
257 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
258 | { | |
259 | struct mm_slot *mm_slot; | |
260 | struct hlist_head *bucket; | |
261 | struct hlist_node *node; | |
262 | ||
263 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
264 | % MM_SLOTS_HASH_HEADS]; | |
265 | hlist_for_each_entry(mm_slot, node, bucket, link) { | |
266 | if (mm == mm_slot->mm) | |
267 | return mm_slot; | |
268 | } | |
269 | return NULL; | |
270 | } | |
271 | ||
272 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
273 | struct mm_slot *mm_slot) | |
274 | { | |
275 | struct hlist_head *bucket; | |
276 | ||
277 | bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) | |
278 | % MM_SLOTS_HASH_HEADS]; | |
279 | mm_slot->mm = mm; | |
31dbd01f IE |
280 | hlist_add_head(&mm_slot->link, bucket); |
281 | } | |
282 | ||
283 | static inline int in_stable_tree(struct rmap_item *rmap_item) | |
284 | { | |
285 | return rmap_item->address & STABLE_FLAG; | |
286 | } | |
287 | ||
a913e182 HD |
288 | /* |
289 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
290 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
291 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
292 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
293 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
294 | * places for correctness, in some places just to avoid unnecessary work. | |
295 | */ | |
296 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
297 | { | |
298 | return atomic_read(&mm->mm_users) == 0; | |
299 | } | |
300 | ||
31dbd01f IE |
301 | /* |
302 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
303 | * | |
304 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
305 | * put_page(page); | |
306 | * | |
307 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
308 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
309 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
310 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
311 | */ | |
d952b791 | 312 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
313 | { |
314 | struct page *page; | |
d952b791 | 315 | int ret = 0; |
31dbd01f IE |
316 | |
317 | do { | |
318 | cond_resched(); | |
319 | page = follow_page(vma, addr, FOLL_GET); | |
320 | if (!page) | |
321 | break; | |
322 | if (PageKsm(page)) | |
323 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
324 | FAULT_FLAG_WRITE); | |
325 | else | |
326 | ret = VM_FAULT_WRITE; | |
327 | put_page(page); | |
d952b791 HD |
328 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
329 | /* | |
330 | * We must loop because handle_mm_fault() may back out if there's | |
331 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
332 | * | |
333 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
334 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
335 | * but note that a concurrent fault might break PageKsm for us. | |
336 | * | |
337 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
338 | * backing file, which also invalidates anonymous pages: that's | |
339 | * okay, that truncation will have unmapped the PageKsm for us. | |
340 | * | |
341 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
342 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
343 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
344 | * to user; and ksmd, having no mm, would never be chosen for that. | |
345 | * | |
346 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
347 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
348 | * even ksmd can fail in this way - though it's usually breaking ksm | |
349 | * just to undo a merge it made a moment before, so unlikely to oom. | |
350 | * | |
351 | * That's a pity: we might therefore have more kernel pages allocated | |
352 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
353 | * will retry to break_cow on each pass, so should recover the page | |
354 | * in due course. The important thing is to not let VM_MERGEABLE | |
355 | * be cleared while any such pages might remain in the area. | |
356 | */ | |
357 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
358 | } |
359 | ||
8dd3557a | 360 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 361 | { |
8dd3557a HD |
362 | struct mm_struct *mm = rmap_item->mm; |
363 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
364 | struct vm_area_struct *vma; |
365 | ||
81464e30 | 366 | down_read(&mm->mmap_sem); |
9ba69294 HD |
367 | if (ksm_test_exit(mm)) |
368 | goto out; | |
31dbd01f IE |
369 | vma = find_vma(mm, addr); |
370 | if (!vma || vma->vm_start > addr) | |
81464e30 | 371 | goto out; |
31dbd01f | 372 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
81464e30 | 373 | goto out; |
31dbd01f | 374 | break_ksm(vma, addr); |
81464e30 | 375 | out: |
31dbd01f IE |
376 | up_read(&mm->mmap_sem); |
377 | } | |
378 | ||
379 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
380 | { | |
381 | struct mm_struct *mm = rmap_item->mm; | |
382 | unsigned long addr = rmap_item->address; | |
383 | struct vm_area_struct *vma; | |
384 | struct page *page; | |
385 | ||
386 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
387 | if (ksm_test_exit(mm)) |
388 | goto out; | |
31dbd01f IE |
389 | vma = find_vma(mm, addr); |
390 | if (!vma || vma->vm_start > addr) | |
391 | goto out; | |
392 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
393 | goto out; | |
394 | ||
395 | page = follow_page(vma, addr, FOLL_GET); | |
396 | if (!page) | |
397 | goto out; | |
398 | if (PageAnon(page)) { | |
399 | flush_anon_page(vma, page, addr); | |
400 | flush_dcache_page(page); | |
401 | } else { | |
402 | put_page(page); | |
403 | out: page = NULL; | |
404 | } | |
405 | up_read(&mm->mmap_sem); | |
406 | return page; | |
407 | } | |
408 | ||
409 | /* | |
410 | * get_ksm_page: checks if the page at the virtual address in rmap_item | |
411 | * is still PageKsm, in which case we can trust the content of the page, | |
412 | * and it returns the gotten page; but NULL if the page has been zapped. | |
413 | */ | |
414 | static struct page *get_ksm_page(struct rmap_item *rmap_item) | |
415 | { | |
416 | struct page *page; | |
417 | ||
418 | page = get_mergeable_page(rmap_item); | |
419 | if (page && !PageKsm(page)) { | |
420 | put_page(page); | |
421 | page = NULL; | |
422 | } | |
423 | return page; | |
424 | } | |
425 | ||
426 | /* | |
427 | * Removing rmap_item from stable or unstable tree. | |
428 | * This function will clean the information from the stable/unstable tree. | |
429 | */ | |
430 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
431 | { | |
432 | if (in_stable_tree(rmap_item)) { | |
433 | struct rmap_item *next_item = rmap_item->next; | |
434 | ||
435 | if (rmap_item->address & NODE_FLAG) { | |
436 | if (next_item) { | |
437 | rb_replace_node(&rmap_item->node, | |
438 | &next_item->node, | |
439 | &root_stable_tree); | |
440 | next_item->address |= NODE_FLAG; | |
e178dfde | 441 | ksm_pages_sharing--; |
31dbd01f IE |
442 | } else { |
443 | rb_erase(&rmap_item->node, &root_stable_tree); | |
b4028260 | 444 | ksm_pages_shared--; |
31dbd01f IE |
445 | } |
446 | } else { | |
447 | struct rmap_item *prev_item = rmap_item->prev; | |
448 | ||
449 | BUG_ON(prev_item->next != rmap_item); | |
450 | prev_item->next = next_item; | |
451 | if (next_item) { | |
452 | BUG_ON(next_item->prev != rmap_item); | |
453 | next_item->prev = rmap_item->prev; | |
454 | } | |
e178dfde | 455 | ksm_pages_sharing--; |
31dbd01f IE |
456 | } |
457 | ||
458 | rmap_item->next = NULL; | |
93d17715 | 459 | rmap_item->address &= PAGE_MASK; |
31dbd01f IE |
460 | |
461 | } else if (rmap_item->address & NODE_FLAG) { | |
462 | unsigned char age; | |
463 | /* | |
9ba69294 | 464 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 465 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
466 | * But be careful when an mm is exiting: do the rb_erase |
467 | * if this rmap_item was inserted by this scan, rather | |
468 | * than left over from before. | |
31dbd01f IE |
469 | */ |
470 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 471 | BUG_ON(age > 1); |
31dbd01f IE |
472 | if (!age) |
473 | rb_erase(&rmap_item->node, &root_unstable_tree); | |
93d17715 | 474 | |
473b0ce4 | 475 | ksm_pages_unshared--; |
93d17715 | 476 | rmap_item->address &= PAGE_MASK; |
31dbd01f IE |
477 | } |
478 | ||
31dbd01f IE |
479 | cond_resched(); /* we're called from many long loops */ |
480 | } | |
481 | ||
31dbd01f | 482 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 483 | struct rmap_item **rmap_list) |
31dbd01f | 484 | { |
6514d511 HD |
485 | while (*rmap_list) { |
486 | struct rmap_item *rmap_item = *rmap_list; | |
487 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 488 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
489 | free_rmap_item(rmap_item); |
490 | } | |
491 | } | |
492 | ||
493 | /* | |
494 | * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather | |
495 | * than check every pte of a given vma, the locking doesn't quite work for | |
496 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
497 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
498 | * rmap_items from parent to child at fork time (so as not to waste time | |
499 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
500 | * |
501 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
502 | * and freeing memory) when unmerging an area, it's easier to leave that | |
503 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
504 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 505 | */ |
d952b791 HD |
506 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
507 | unsigned long start, unsigned long end) | |
31dbd01f IE |
508 | { |
509 | unsigned long addr; | |
d952b791 | 510 | int err = 0; |
31dbd01f | 511 | |
d952b791 | 512 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
513 | if (ksm_test_exit(vma->vm_mm)) |
514 | break; | |
d952b791 HD |
515 | if (signal_pending(current)) |
516 | err = -ERESTARTSYS; | |
517 | else | |
518 | err = break_ksm(vma, addr); | |
519 | } | |
520 | return err; | |
31dbd01f IE |
521 | } |
522 | ||
2ffd8679 HD |
523 | #ifdef CONFIG_SYSFS |
524 | /* | |
525 | * Only called through the sysfs control interface: | |
526 | */ | |
d952b791 | 527 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
528 | { |
529 | struct mm_slot *mm_slot; | |
530 | struct mm_struct *mm; | |
531 | struct vm_area_struct *vma; | |
d952b791 HD |
532 | int err = 0; |
533 | ||
534 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 535 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
536 | struct mm_slot, mm_list); |
537 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 538 | |
9ba69294 HD |
539 | for (mm_slot = ksm_scan.mm_slot; |
540 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
541 | mm = mm_slot->mm; |
542 | down_read(&mm->mmap_sem); | |
543 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
544 | if (ksm_test_exit(mm)) |
545 | break; | |
31dbd01f IE |
546 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
547 | continue; | |
d952b791 HD |
548 | err = unmerge_ksm_pages(vma, |
549 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
550 | if (err) |
551 | goto error; | |
31dbd01f | 552 | } |
9ba69294 | 553 | |
6514d511 | 554 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
555 | |
556 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 557 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 558 | struct mm_slot, mm_list); |
9ba69294 HD |
559 | if (ksm_test_exit(mm)) { |
560 | hlist_del(&mm_slot->link); | |
561 | list_del(&mm_slot->mm_list); | |
562 | spin_unlock(&ksm_mmlist_lock); | |
563 | ||
564 | free_mm_slot(mm_slot); | |
565 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
566 | up_read(&mm->mmap_sem); | |
567 | mmdrop(mm); | |
568 | } else { | |
569 | spin_unlock(&ksm_mmlist_lock); | |
570 | up_read(&mm->mmap_sem); | |
571 | } | |
31dbd01f IE |
572 | } |
573 | ||
d952b791 | 574 | ksm_scan.seqnr = 0; |
9ba69294 HD |
575 | return 0; |
576 | ||
577 | error: | |
578 | up_read(&mm->mmap_sem); | |
31dbd01f | 579 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 580 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 581 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 582 | return err; |
31dbd01f | 583 | } |
2ffd8679 | 584 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 585 | |
31dbd01f IE |
586 | static u32 calc_checksum(struct page *page) |
587 | { | |
588 | u32 checksum; | |
589 | void *addr = kmap_atomic(page, KM_USER0); | |
590 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); | |
591 | kunmap_atomic(addr, KM_USER0); | |
592 | return checksum; | |
593 | } | |
594 | ||
595 | static int memcmp_pages(struct page *page1, struct page *page2) | |
596 | { | |
597 | char *addr1, *addr2; | |
598 | int ret; | |
599 | ||
600 | addr1 = kmap_atomic(page1, KM_USER0); | |
601 | addr2 = kmap_atomic(page2, KM_USER1); | |
602 | ret = memcmp(addr1, addr2, PAGE_SIZE); | |
603 | kunmap_atomic(addr2, KM_USER1); | |
604 | kunmap_atomic(addr1, KM_USER0); | |
605 | return ret; | |
606 | } | |
607 | ||
608 | static inline int pages_identical(struct page *page1, struct page *page2) | |
609 | { | |
610 | return !memcmp_pages(page1, page2); | |
611 | } | |
612 | ||
613 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
614 | pte_t *orig_pte) | |
615 | { | |
616 | struct mm_struct *mm = vma->vm_mm; | |
617 | unsigned long addr; | |
618 | pte_t *ptep; | |
619 | spinlock_t *ptl; | |
620 | int swapped; | |
621 | int err = -EFAULT; | |
622 | ||
623 | addr = page_address_in_vma(page, vma); | |
624 | if (addr == -EFAULT) | |
625 | goto out; | |
626 | ||
627 | ptep = page_check_address(page, mm, addr, &ptl, 0); | |
628 | if (!ptep) | |
629 | goto out; | |
630 | ||
631 | if (pte_write(*ptep)) { | |
632 | pte_t entry; | |
633 | ||
634 | swapped = PageSwapCache(page); | |
635 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
636 | /* | |
637 | * Ok this is tricky, when get_user_pages_fast() run it doesnt | |
638 | * take any lock, therefore the check that we are going to make | |
639 | * with the pagecount against the mapcount is racey and | |
640 | * O_DIRECT can happen right after the check. | |
641 | * So we clear the pte and flush the tlb before the check | |
642 | * this assure us that no O_DIRECT can happen after the check | |
643 | * or in the middle of the check. | |
644 | */ | |
645 | entry = ptep_clear_flush(vma, addr, ptep); | |
646 | /* | |
647 | * Check that no O_DIRECT or similar I/O is in progress on the | |
648 | * page | |
649 | */ | |
31e855ea | 650 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
31dbd01f IE |
651 | set_pte_at_notify(mm, addr, ptep, entry); |
652 | goto out_unlock; | |
653 | } | |
654 | entry = pte_wrprotect(entry); | |
655 | set_pte_at_notify(mm, addr, ptep, entry); | |
656 | } | |
657 | *orig_pte = *ptep; | |
658 | err = 0; | |
659 | ||
660 | out_unlock: | |
661 | pte_unmap_unlock(ptep, ptl); | |
662 | out: | |
663 | return err; | |
664 | } | |
665 | ||
666 | /** | |
667 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
668 | * @vma: vma that holds the pte pointing to page |
669 | * @page: the page we are replacing by kpage | |
670 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
671 | * @orig_pte: the original value of the pte |
672 | * | |
673 | * Returns 0 on success, -EFAULT on failure. | |
674 | */ | |
8dd3557a HD |
675 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
676 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
677 | { |
678 | struct mm_struct *mm = vma->vm_mm; | |
679 | pgd_t *pgd; | |
680 | pud_t *pud; | |
681 | pmd_t *pmd; | |
682 | pte_t *ptep; | |
683 | spinlock_t *ptl; | |
684 | unsigned long addr; | |
31dbd01f IE |
685 | int err = -EFAULT; |
686 | ||
8dd3557a | 687 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
688 | if (addr == -EFAULT) |
689 | goto out; | |
690 | ||
691 | pgd = pgd_offset(mm, addr); | |
692 | if (!pgd_present(*pgd)) | |
693 | goto out; | |
694 | ||
695 | pud = pud_offset(pgd, addr); | |
696 | if (!pud_present(*pud)) | |
697 | goto out; | |
698 | ||
699 | pmd = pmd_offset(pud, addr); | |
700 | if (!pmd_present(*pmd)) | |
701 | goto out; | |
702 | ||
703 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
704 | if (!pte_same(*ptep, orig_pte)) { | |
705 | pte_unmap_unlock(ptep, ptl); | |
706 | goto out; | |
707 | } | |
708 | ||
8dd3557a HD |
709 | get_page(kpage); |
710 | page_add_ksm_rmap(kpage); | |
31dbd01f IE |
711 | |
712 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
713 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 714 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 715 | |
8dd3557a HD |
716 | page_remove_rmap(page); |
717 | put_page(page); | |
31dbd01f IE |
718 | |
719 | pte_unmap_unlock(ptep, ptl); | |
720 | err = 0; | |
721 | out: | |
722 | return err; | |
723 | } | |
724 | ||
725 | /* | |
726 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
727 | * @vma: the vma that holds the pte pointing to page |
728 | * @page: the PageAnon page that we want to replace with kpage | |
729 | * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap | |
730 | * will make PageKsm) that we want to map instead of page | |
31dbd01f IE |
731 | * |
732 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
733 | */ | |
734 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 735 | struct page *page, struct page *kpage) |
31dbd01f IE |
736 | { |
737 | pte_t orig_pte = __pte(0); | |
738 | int err = -EFAULT; | |
739 | ||
740 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
741 | goto out; | |
8dd3557a | 742 | if (!PageAnon(page)) |
31dbd01f IE |
743 | goto out; |
744 | ||
31dbd01f IE |
745 | /* |
746 | * We need the page lock to read a stable PageSwapCache in | |
747 | * write_protect_page(). We use trylock_page() instead of | |
748 | * lock_page() because we don't want to wait here - we | |
749 | * prefer to continue scanning and merging different pages, | |
750 | * then come back to this page when it is unlocked. | |
751 | */ | |
8dd3557a | 752 | if (!trylock_page(page)) |
31e855ea | 753 | goto out; |
31dbd01f IE |
754 | /* |
755 | * If this anonymous page is mapped only here, its pte may need | |
756 | * to be write-protected. If it's mapped elsewhere, all of its | |
757 | * ptes are necessarily already write-protected. But in either | |
758 | * case, we need to lock and check page_count is not raised. | |
759 | */ | |
8dd3557a HD |
760 | if (write_protect_page(vma, page, &orig_pte) == 0 && |
761 | pages_identical(page, kpage)) | |
762 | err = replace_page(vma, page, kpage, orig_pte); | |
31dbd01f | 763 | |
8dd3557a | 764 | unlock_page(page); |
31dbd01f IE |
765 | out: |
766 | return err; | |
767 | } | |
768 | ||
81464e30 HD |
769 | /* |
770 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
771 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
772 | * |
773 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 774 | */ |
8dd3557a HD |
775 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
776 | struct page *page, struct page *kpage) | |
81464e30 | 777 | { |
8dd3557a | 778 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
779 | struct vm_area_struct *vma; |
780 | int err = -EFAULT; | |
781 | ||
8dd3557a HD |
782 | down_read(&mm->mmap_sem); |
783 | if (ksm_test_exit(mm)) | |
9ba69294 | 784 | goto out; |
8dd3557a HD |
785 | vma = find_vma(mm, rmap_item->address); |
786 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
787 | goto out; |
788 | ||
8dd3557a | 789 | err = try_to_merge_one_page(vma, page, kpage); |
81464e30 | 790 | out: |
8dd3557a | 791 | up_read(&mm->mmap_sem); |
81464e30 HD |
792 | return err; |
793 | } | |
794 | ||
31dbd01f IE |
795 | /* |
796 | * try_to_merge_two_pages - take two identical pages and prepare them | |
797 | * to be merged into one page. | |
798 | * | |
8dd3557a HD |
799 | * This function returns the kpage if we successfully merged two identical |
800 | * pages into one ksm page, NULL otherwise. | |
31dbd01f IE |
801 | * |
802 | * Note that this function allocates a new kernel page: if one of the pages | |
803 | * is already a ksm page, try_to_merge_with_ksm_page should be used. | |
804 | */ | |
8dd3557a HD |
805 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
806 | struct page *page, | |
807 | struct rmap_item *tree_rmap_item, | |
808 | struct page *tree_page) | |
31dbd01f | 809 | { |
8dd3557a | 810 | struct mm_struct *mm = rmap_item->mm; |
31dbd01f IE |
811 | struct vm_area_struct *vma; |
812 | struct page *kpage; | |
813 | int err = -EFAULT; | |
814 | ||
815 | /* | |
816 | * The number of nodes in the stable tree | |
817 | * is the number of kernel pages that we hold. | |
818 | */ | |
819 | if (ksm_max_kernel_pages && | |
b4028260 | 820 | ksm_max_kernel_pages <= ksm_pages_shared) |
8dd3557a | 821 | return NULL; |
31dbd01f IE |
822 | |
823 | kpage = alloc_page(GFP_HIGHUSER); | |
824 | if (!kpage) | |
8dd3557a | 825 | return NULL; |
31dbd01f | 826 | |
8dd3557a HD |
827 | down_read(&mm->mmap_sem); |
828 | if (ksm_test_exit(mm)) | |
829 | goto up; | |
830 | vma = find_vma(mm, rmap_item->address); | |
831 | if (!vma || vma->vm_start > rmap_item->address) | |
832 | goto up; | |
833 | ||
834 | copy_user_highpage(kpage, page, rmap_item->address, vma); | |
835 | err = try_to_merge_one_page(vma, page, kpage); | |
836 | up: | |
837 | up_read(&mm->mmap_sem); | |
31dbd01f IE |
838 | |
839 | if (!err) { | |
8dd3557a HD |
840 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
841 | tree_page, kpage); | |
31dbd01f | 842 | /* |
81464e30 HD |
843 | * If that fails, we have a ksm page with only one pte |
844 | * pointing to it: so break it. | |
31dbd01f IE |
845 | */ |
846 | if (err) | |
8dd3557a | 847 | break_cow(rmap_item); |
31dbd01f | 848 | } |
8dd3557a HD |
849 | if (err) { |
850 | put_page(kpage); | |
851 | kpage = NULL; | |
852 | } | |
853 | return kpage; | |
31dbd01f IE |
854 | } |
855 | ||
31dbd01f | 856 | /* |
8dd3557a | 857 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
858 | * |
859 | * This function checks if there is a page inside the stable tree | |
860 | * with identical content to the page that we are scanning right now. | |
861 | * | |
862 | * This function return rmap_item pointer to the identical item if found, | |
863 | * NULL otherwise. | |
864 | */ | |
865 | static struct rmap_item *stable_tree_search(struct page *page, | |
8dd3557a | 866 | struct page **tree_pagep) |
31dbd01f IE |
867 | { |
868 | struct rb_node *node = root_stable_tree.rb_node; | |
869 | ||
870 | while (node) { | |
871 | struct rmap_item *tree_rmap_item, *next_rmap_item; | |
8dd3557a | 872 | struct page *tree_page; |
31dbd01f IE |
873 | int ret; |
874 | ||
875 | tree_rmap_item = rb_entry(node, struct rmap_item, node); | |
876 | while (tree_rmap_item) { | |
877 | BUG_ON(!in_stable_tree(tree_rmap_item)); | |
878 | cond_resched(); | |
8dd3557a HD |
879 | tree_page = get_ksm_page(tree_rmap_item); |
880 | if (tree_page) | |
31dbd01f IE |
881 | break; |
882 | next_rmap_item = tree_rmap_item->next; | |
883 | remove_rmap_item_from_tree(tree_rmap_item); | |
884 | tree_rmap_item = next_rmap_item; | |
885 | } | |
886 | if (!tree_rmap_item) | |
887 | return NULL; | |
888 | ||
8dd3557a | 889 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
890 | |
891 | if (ret < 0) { | |
8dd3557a | 892 | put_page(tree_page); |
31dbd01f IE |
893 | node = node->rb_left; |
894 | } else if (ret > 0) { | |
8dd3557a | 895 | put_page(tree_page); |
31dbd01f IE |
896 | node = node->rb_right; |
897 | } else { | |
8dd3557a | 898 | *tree_pagep = tree_page; |
31dbd01f IE |
899 | return tree_rmap_item; |
900 | } | |
901 | } | |
902 | ||
903 | return NULL; | |
904 | } | |
905 | ||
906 | /* | |
907 | * stable_tree_insert - insert rmap_item pointing to new ksm page | |
908 | * into the stable tree. | |
909 | * | |
31dbd01f IE |
910 | * This function returns rmap_item if success, NULL otherwise. |
911 | */ | |
8dd3557a | 912 | static struct rmap_item *stable_tree_insert(struct page *kpage, |
31dbd01f IE |
913 | struct rmap_item *rmap_item) |
914 | { | |
915 | struct rb_node **new = &root_stable_tree.rb_node; | |
916 | struct rb_node *parent = NULL; | |
917 | ||
918 | while (*new) { | |
919 | struct rmap_item *tree_rmap_item, *next_rmap_item; | |
920 | struct page *tree_page; | |
921 | int ret; | |
922 | ||
923 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); | |
924 | while (tree_rmap_item) { | |
925 | BUG_ON(!in_stable_tree(tree_rmap_item)); | |
926 | cond_resched(); | |
927 | tree_page = get_ksm_page(tree_rmap_item); | |
928 | if (tree_page) | |
929 | break; | |
930 | next_rmap_item = tree_rmap_item->next; | |
931 | remove_rmap_item_from_tree(tree_rmap_item); | |
932 | tree_rmap_item = next_rmap_item; | |
933 | } | |
934 | if (!tree_rmap_item) | |
935 | return NULL; | |
936 | ||
8dd3557a | 937 | ret = memcmp_pages(kpage, tree_page); |
31dbd01f IE |
938 | put_page(tree_page); |
939 | ||
940 | parent = *new; | |
941 | if (ret < 0) | |
942 | new = &parent->rb_left; | |
943 | else if (ret > 0) | |
944 | new = &parent->rb_right; | |
945 | else { | |
946 | /* | |
947 | * It is not a bug that stable_tree_search() didn't | |
948 | * find this node: because at that time our page was | |
949 | * not yet write-protected, so may have changed since. | |
950 | */ | |
951 | return NULL; | |
952 | } | |
953 | } | |
954 | ||
31dbd01f IE |
955 | rmap_item->address |= NODE_FLAG | STABLE_FLAG; |
956 | rmap_item->next = NULL; | |
957 | rb_link_node(&rmap_item->node, parent, new); | |
958 | rb_insert_color(&rmap_item->node, &root_stable_tree); | |
959 | ||
e178dfde | 960 | ksm_pages_shared++; |
31dbd01f IE |
961 | return rmap_item; |
962 | } | |
963 | ||
964 | /* | |
8dd3557a HD |
965 | * unstable_tree_search_insert - search for identical page, |
966 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
967 | * |
968 | * This function searches for a page in the unstable tree identical to the | |
969 | * page currently being scanned; and if no identical page is found in the | |
970 | * tree, we insert rmap_item as a new object into the unstable tree. | |
971 | * | |
972 | * This function returns pointer to rmap_item found to be identical | |
973 | * to the currently scanned page, NULL otherwise. | |
974 | * | |
975 | * This function does both searching and inserting, because they share | |
976 | * the same walking algorithm in an rbtree. | |
977 | */ | |
8dd3557a HD |
978 | static |
979 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
980 | struct page *page, | |
981 | struct page **tree_pagep) | |
982 | ||
31dbd01f IE |
983 | { |
984 | struct rb_node **new = &root_unstable_tree.rb_node; | |
985 | struct rb_node *parent = NULL; | |
986 | ||
987 | while (*new) { | |
988 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 989 | struct page *tree_page; |
31dbd01f IE |
990 | int ret; |
991 | ||
d178f27f | 992 | cond_resched(); |
31dbd01f | 993 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a HD |
994 | tree_page = get_mergeable_page(tree_rmap_item); |
995 | if (!tree_page) | |
31dbd01f IE |
996 | return NULL; |
997 | ||
998 | /* | |
8dd3557a | 999 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1000 | */ |
8dd3557a HD |
1001 | if (page == tree_page) { |
1002 | put_page(tree_page); | |
31dbd01f IE |
1003 | return NULL; |
1004 | } | |
1005 | ||
8dd3557a | 1006 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1007 | |
1008 | parent = *new; | |
1009 | if (ret < 0) { | |
8dd3557a | 1010 | put_page(tree_page); |
31dbd01f IE |
1011 | new = &parent->rb_left; |
1012 | } else if (ret > 0) { | |
8dd3557a | 1013 | put_page(tree_page); |
31dbd01f IE |
1014 | new = &parent->rb_right; |
1015 | } else { | |
8dd3557a | 1016 | *tree_pagep = tree_page; |
31dbd01f IE |
1017 | return tree_rmap_item; |
1018 | } | |
1019 | } | |
1020 | ||
1021 | rmap_item->address |= NODE_FLAG; | |
1022 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); | |
1023 | rb_link_node(&rmap_item->node, parent, new); | |
1024 | rb_insert_color(&rmap_item->node, &root_unstable_tree); | |
1025 | ||
473b0ce4 | 1026 | ksm_pages_unshared++; |
31dbd01f IE |
1027 | return NULL; |
1028 | } | |
1029 | ||
1030 | /* | |
1031 | * stable_tree_append - add another rmap_item to the linked list of | |
1032 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1033 | * the same ksm page. | |
1034 | */ | |
1035 | static void stable_tree_append(struct rmap_item *rmap_item, | |
1036 | struct rmap_item *tree_rmap_item) | |
1037 | { | |
1038 | rmap_item->next = tree_rmap_item->next; | |
1039 | rmap_item->prev = tree_rmap_item; | |
1040 | ||
1041 | if (tree_rmap_item->next) | |
1042 | tree_rmap_item->next->prev = rmap_item; | |
1043 | ||
1044 | tree_rmap_item->next = rmap_item; | |
1045 | rmap_item->address |= STABLE_FLAG; | |
e178dfde HD |
1046 | |
1047 | ksm_pages_sharing++; | |
31dbd01f IE |
1048 | } |
1049 | ||
1050 | /* | |
81464e30 HD |
1051 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1052 | * if not, compare checksum to previous and if it's the same, see if page can | |
1053 | * be inserted into the unstable tree, or merged with a page already there and | |
1054 | * both transferred to the stable tree. | |
31dbd01f IE |
1055 | * |
1056 | * @page: the page that we are searching identical page to. | |
1057 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1058 | */ | |
1059 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1060 | { | |
31dbd01f | 1061 | struct rmap_item *tree_rmap_item; |
8dd3557a HD |
1062 | struct page *tree_page = NULL; |
1063 | struct page *kpage; | |
31dbd01f IE |
1064 | unsigned int checksum; |
1065 | int err; | |
1066 | ||
93d17715 | 1067 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1068 | |
1069 | /* We first start with searching the page inside the stable tree */ | |
8dd3557a | 1070 | tree_rmap_item = stable_tree_search(page, &tree_page); |
31dbd01f | 1071 | if (tree_rmap_item) { |
8dd3557a HD |
1072 | kpage = tree_page; |
1073 | if (page == kpage) /* forked */ | |
31dbd01f | 1074 | err = 0; |
e178dfde | 1075 | else |
8dd3557a HD |
1076 | err = try_to_merge_with_ksm_page(rmap_item, |
1077 | page, kpage); | |
31dbd01f IE |
1078 | if (!err) { |
1079 | /* | |
1080 | * The page was successfully merged: | |
1081 | * add its rmap_item to the stable tree. | |
1082 | */ | |
1083 | stable_tree_append(rmap_item, tree_rmap_item); | |
1084 | } | |
8dd3557a | 1085 | put_page(kpage); |
31dbd01f IE |
1086 | return; |
1087 | } | |
1088 | ||
1089 | /* | |
1090 | * A ksm page might have got here by fork, but its other | |
1091 | * references have already been removed from the stable tree. | |
d952b791 HD |
1092 | * Or it might be left over from a break_ksm which failed |
1093 | * when the mem_cgroup had reached its limit: try again now. | |
31dbd01f IE |
1094 | */ |
1095 | if (PageKsm(page)) | |
8dd3557a | 1096 | break_cow(rmap_item); |
31dbd01f IE |
1097 | |
1098 | /* | |
1099 | * In case the hash value of the page was changed from the last time we | |
1100 | * have calculated it, this page to be changed frequely, therefore we | |
1101 | * don't want to insert it to the unstable tree, and we don't want to | |
1102 | * waste our time to search if there is something identical to it there. | |
1103 | */ | |
1104 | checksum = calc_checksum(page); | |
1105 | if (rmap_item->oldchecksum != checksum) { | |
1106 | rmap_item->oldchecksum = checksum; | |
1107 | return; | |
1108 | } | |
1109 | ||
8dd3557a HD |
1110 | tree_rmap_item = |
1111 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1112 | if (tree_rmap_item) { |
8dd3557a HD |
1113 | kpage = try_to_merge_two_pages(rmap_item, page, |
1114 | tree_rmap_item, tree_page); | |
1115 | put_page(tree_page); | |
31dbd01f IE |
1116 | /* |
1117 | * As soon as we merge this page, we want to remove the | |
1118 | * rmap_item of the page we have merged with from the unstable | |
1119 | * tree, and insert it instead as new node in the stable tree. | |
1120 | */ | |
8dd3557a | 1121 | if (kpage) { |
93d17715 | 1122 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1123 | |
31dbd01f IE |
1124 | /* |
1125 | * If we fail to insert the page into the stable tree, | |
1126 | * we will have 2 virtual addresses that are pointing | |
1127 | * to a ksm page left outside the stable tree, | |
1128 | * in which case we need to break_cow on both. | |
1129 | */ | |
8dd3557a | 1130 | if (stable_tree_insert(kpage, tree_rmap_item)) |
31dbd01f IE |
1131 | stable_tree_append(rmap_item, tree_rmap_item); |
1132 | else { | |
8dd3557a HD |
1133 | break_cow(tree_rmap_item); |
1134 | break_cow(rmap_item); | |
31dbd01f | 1135 | } |
8dd3557a | 1136 | put_page(kpage); |
31dbd01f | 1137 | } |
31dbd01f IE |
1138 | } |
1139 | } | |
1140 | ||
1141 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1142 | struct rmap_item **rmap_list, |
31dbd01f IE |
1143 | unsigned long addr) |
1144 | { | |
1145 | struct rmap_item *rmap_item; | |
1146 | ||
6514d511 HD |
1147 | while (*rmap_list) { |
1148 | rmap_item = *rmap_list; | |
93d17715 | 1149 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1150 | return rmap_item; |
31dbd01f IE |
1151 | if (rmap_item->address > addr) |
1152 | break; | |
6514d511 | 1153 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1154 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1155 | free_rmap_item(rmap_item); |
1156 | } | |
1157 | ||
1158 | rmap_item = alloc_rmap_item(); | |
1159 | if (rmap_item) { | |
1160 | /* It has already been zeroed */ | |
1161 | rmap_item->mm = mm_slot->mm; | |
1162 | rmap_item->address = addr; | |
6514d511 HD |
1163 | rmap_item->rmap_list = *rmap_list; |
1164 | *rmap_list = rmap_item; | |
31dbd01f IE |
1165 | } |
1166 | return rmap_item; | |
1167 | } | |
1168 | ||
1169 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1170 | { | |
1171 | struct mm_struct *mm; | |
1172 | struct mm_slot *slot; | |
1173 | struct vm_area_struct *vma; | |
1174 | struct rmap_item *rmap_item; | |
1175 | ||
1176 | if (list_empty(&ksm_mm_head.mm_list)) | |
1177 | return NULL; | |
1178 | ||
1179 | slot = ksm_scan.mm_slot; | |
1180 | if (slot == &ksm_mm_head) { | |
1181 | root_unstable_tree = RB_ROOT; | |
1182 | ||
1183 | spin_lock(&ksm_mmlist_lock); | |
1184 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1185 | ksm_scan.mm_slot = slot; | |
1186 | spin_unlock(&ksm_mmlist_lock); | |
1187 | next_mm: | |
1188 | ksm_scan.address = 0; | |
6514d511 | 1189 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1190 | } |
1191 | ||
1192 | mm = slot->mm; | |
1193 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1194 | if (ksm_test_exit(mm)) |
1195 | vma = NULL; | |
1196 | else | |
1197 | vma = find_vma(mm, ksm_scan.address); | |
1198 | ||
1199 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1200 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1201 | continue; | |
1202 | if (ksm_scan.address < vma->vm_start) | |
1203 | ksm_scan.address = vma->vm_start; | |
1204 | if (!vma->anon_vma) | |
1205 | ksm_scan.address = vma->vm_end; | |
1206 | ||
1207 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1208 | if (ksm_test_exit(mm)) |
1209 | break; | |
31dbd01f IE |
1210 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
1211 | if (*page && PageAnon(*page)) { | |
1212 | flush_anon_page(vma, *page, ksm_scan.address); | |
1213 | flush_dcache_page(*page); | |
1214 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1215 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1216 | if (rmap_item) { |
6514d511 HD |
1217 | ksm_scan.rmap_list = |
1218 | &rmap_item->rmap_list; | |
31dbd01f IE |
1219 | ksm_scan.address += PAGE_SIZE; |
1220 | } else | |
1221 | put_page(*page); | |
1222 | up_read(&mm->mmap_sem); | |
1223 | return rmap_item; | |
1224 | } | |
1225 | if (*page) | |
1226 | put_page(*page); | |
1227 | ksm_scan.address += PAGE_SIZE; | |
1228 | cond_resched(); | |
1229 | } | |
1230 | } | |
1231 | ||
9ba69294 HD |
1232 | if (ksm_test_exit(mm)) { |
1233 | ksm_scan.address = 0; | |
6514d511 | 1234 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1235 | } |
31dbd01f IE |
1236 | /* |
1237 | * Nuke all the rmap_items that are above this current rmap: | |
1238 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1239 | */ | |
6514d511 | 1240 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1241 | |
1242 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1243 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1244 | struct mm_slot, mm_list); | |
1245 | if (ksm_scan.address == 0) { | |
1246 | /* | |
1247 | * We've completed a full scan of all vmas, holding mmap_sem | |
1248 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1249 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1250 | * This applies either when cleaning up after __ksm_exit |
1251 | * (but beware: we can reach here even before __ksm_exit), | |
1252 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1253 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 HD |
1254 | */ |
1255 | hlist_del(&slot->link); | |
1256 | list_del(&slot->mm_list); | |
9ba69294 HD |
1257 | spin_unlock(&ksm_mmlist_lock); |
1258 | ||
cd551f97 HD |
1259 | free_mm_slot(slot); |
1260 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1261 | up_read(&mm->mmap_sem); |
1262 | mmdrop(mm); | |
1263 | } else { | |
1264 | spin_unlock(&ksm_mmlist_lock); | |
1265 | up_read(&mm->mmap_sem); | |
cd551f97 | 1266 | } |
31dbd01f IE |
1267 | |
1268 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1269 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1270 | if (slot != &ksm_mm_head) |
1271 | goto next_mm; | |
1272 | ||
31dbd01f IE |
1273 | ksm_scan.seqnr++; |
1274 | return NULL; | |
1275 | } | |
1276 | ||
1277 | /** | |
1278 | * ksm_do_scan - the ksm scanner main worker function. | |
1279 | * @scan_npages - number of pages we want to scan before we return. | |
1280 | */ | |
1281 | static void ksm_do_scan(unsigned int scan_npages) | |
1282 | { | |
1283 | struct rmap_item *rmap_item; | |
1284 | struct page *page; | |
1285 | ||
1286 | while (scan_npages--) { | |
1287 | cond_resched(); | |
1288 | rmap_item = scan_get_next_rmap_item(&page); | |
1289 | if (!rmap_item) | |
1290 | return; | |
1291 | if (!PageKsm(page) || !in_stable_tree(rmap_item)) | |
1292 | cmp_and_merge_page(page, rmap_item); | |
26465d3e HD |
1293 | else if (page_mapcount(page) == 1) { |
1294 | /* | |
1295 | * Replace now-unshared ksm page by ordinary page. | |
1296 | */ | |
8dd3557a | 1297 | break_cow(rmap_item); |
26465d3e HD |
1298 | remove_rmap_item_from_tree(rmap_item); |
1299 | rmap_item->oldchecksum = calc_checksum(page); | |
1300 | } | |
31dbd01f IE |
1301 | put_page(page); |
1302 | } | |
1303 | } | |
1304 | ||
6e158384 HD |
1305 | static int ksmd_should_run(void) |
1306 | { | |
1307 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1308 | } | |
1309 | ||
31dbd01f IE |
1310 | static int ksm_scan_thread(void *nothing) |
1311 | { | |
339aa624 | 1312 | set_user_nice(current, 5); |
31dbd01f IE |
1313 | |
1314 | while (!kthread_should_stop()) { | |
6e158384 HD |
1315 | mutex_lock(&ksm_thread_mutex); |
1316 | if (ksmd_should_run()) | |
31dbd01f | 1317 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1318 | mutex_unlock(&ksm_thread_mutex); |
1319 | ||
1320 | if (ksmd_should_run()) { | |
31dbd01f IE |
1321 | schedule_timeout_interruptible( |
1322 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1323 | } else { | |
1324 | wait_event_interruptible(ksm_thread_wait, | |
6e158384 | 1325 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1326 | } |
1327 | } | |
1328 | return 0; | |
1329 | } | |
1330 | ||
f8af4da3 HD |
1331 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1332 | unsigned long end, int advice, unsigned long *vm_flags) | |
1333 | { | |
1334 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1335 | int err; |
f8af4da3 HD |
1336 | |
1337 | switch (advice) { | |
1338 | case MADV_MERGEABLE: | |
1339 | /* | |
1340 | * Be somewhat over-protective for now! | |
1341 | */ | |
1342 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1343 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
1344 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | | |
1345 | VM_MIXEDMAP | VM_SAO)) | |
1346 | return 0; /* just ignore the advice */ | |
1347 | ||
d952b791 HD |
1348 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1349 | err = __ksm_enter(mm); | |
1350 | if (err) | |
1351 | return err; | |
1352 | } | |
f8af4da3 HD |
1353 | |
1354 | *vm_flags |= VM_MERGEABLE; | |
1355 | break; | |
1356 | ||
1357 | case MADV_UNMERGEABLE: | |
1358 | if (!(*vm_flags & VM_MERGEABLE)) | |
1359 | return 0; /* just ignore the advice */ | |
1360 | ||
d952b791 HD |
1361 | if (vma->anon_vma) { |
1362 | err = unmerge_ksm_pages(vma, start, end); | |
1363 | if (err) | |
1364 | return err; | |
1365 | } | |
f8af4da3 HD |
1366 | |
1367 | *vm_flags &= ~VM_MERGEABLE; | |
1368 | break; | |
1369 | } | |
1370 | ||
1371 | return 0; | |
1372 | } | |
1373 | ||
1374 | int __ksm_enter(struct mm_struct *mm) | |
1375 | { | |
6e158384 HD |
1376 | struct mm_slot *mm_slot; |
1377 | int needs_wakeup; | |
1378 | ||
1379 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1380 | if (!mm_slot) |
1381 | return -ENOMEM; | |
1382 | ||
6e158384 HD |
1383 | /* Check ksm_run too? Would need tighter locking */ |
1384 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1385 | ||
31dbd01f IE |
1386 | spin_lock(&ksm_mmlist_lock); |
1387 | insert_to_mm_slots_hash(mm, mm_slot); | |
1388 | /* | |
1389 | * Insert just behind the scanning cursor, to let the area settle | |
1390 | * down a little; when fork is followed by immediate exec, we don't | |
1391 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
1392 | */ | |
1393 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
1394 | spin_unlock(&ksm_mmlist_lock); | |
1395 | ||
f8af4da3 | 1396 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1397 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1398 | |
1399 | if (needs_wakeup) | |
1400 | wake_up_interruptible(&ksm_thread_wait); | |
1401 | ||
f8af4da3 HD |
1402 | return 0; |
1403 | } | |
1404 | ||
1c2fb7a4 | 1405 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1406 | { |
cd551f97 | 1407 | struct mm_slot *mm_slot; |
9ba69294 | 1408 | int easy_to_free = 0; |
cd551f97 | 1409 | |
31dbd01f | 1410 | /* |
9ba69294 HD |
1411 | * This process is exiting: if it's straightforward (as is the |
1412 | * case when ksmd was never running), free mm_slot immediately. | |
1413 | * But if it's at the cursor or has rmap_items linked to it, use | |
1414 | * mmap_sem to synchronize with any break_cows before pagetables | |
1415 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1416 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1417 | */ |
9ba69294 | 1418 | |
cd551f97 HD |
1419 | spin_lock(&ksm_mmlist_lock); |
1420 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1421 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1422 | if (!mm_slot->rmap_list) { |
9ba69294 HD |
1423 | hlist_del(&mm_slot->link); |
1424 | list_del(&mm_slot->mm_list); | |
1425 | easy_to_free = 1; | |
1426 | } else { | |
1427 | list_move(&mm_slot->mm_list, | |
1428 | &ksm_scan.mm_slot->mm_list); | |
1429 | } | |
cd551f97 | 1430 | } |
cd551f97 HD |
1431 | spin_unlock(&ksm_mmlist_lock); |
1432 | ||
9ba69294 HD |
1433 | if (easy_to_free) { |
1434 | free_mm_slot(mm_slot); | |
1435 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1436 | mmdrop(mm); | |
1437 | } else if (mm_slot) { | |
9ba69294 HD |
1438 | down_write(&mm->mmap_sem); |
1439 | up_write(&mm->mmap_sem); | |
9ba69294 | 1440 | } |
31dbd01f IE |
1441 | } |
1442 | ||
2ffd8679 HD |
1443 | #ifdef CONFIG_SYSFS |
1444 | /* | |
1445 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
1446 | */ | |
1447 | ||
31dbd01f IE |
1448 | #define KSM_ATTR_RO(_name) \ |
1449 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
1450 | #define KSM_ATTR(_name) \ | |
1451 | static struct kobj_attribute _name##_attr = \ | |
1452 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
1453 | ||
1454 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
1455 | struct kobj_attribute *attr, char *buf) | |
1456 | { | |
1457 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
1458 | } | |
1459 | ||
1460 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
1461 | struct kobj_attribute *attr, | |
1462 | const char *buf, size_t count) | |
1463 | { | |
1464 | unsigned long msecs; | |
1465 | int err; | |
1466 | ||
1467 | err = strict_strtoul(buf, 10, &msecs); | |
1468 | if (err || msecs > UINT_MAX) | |
1469 | return -EINVAL; | |
1470 | ||
1471 | ksm_thread_sleep_millisecs = msecs; | |
1472 | ||
1473 | return count; | |
1474 | } | |
1475 | KSM_ATTR(sleep_millisecs); | |
1476 | ||
1477 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
1478 | struct kobj_attribute *attr, char *buf) | |
1479 | { | |
1480 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
1481 | } | |
1482 | ||
1483 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
1484 | struct kobj_attribute *attr, | |
1485 | const char *buf, size_t count) | |
1486 | { | |
1487 | int err; | |
1488 | unsigned long nr_pages; | |
1489 | ||
1490 | err = strict_strtoul(buf, 10, &nr_pages); | |
1491 | if (err || nr_pages > UINT_MAX) | |
1492 | return -EINVAL; | |
1493 | ||
1494 | ksm_thread_pages_to_scan = nr_pages; | |
1495 | ||
1496 | return count; | |
1497 | } | |
1498 | KSM_ATTR(pages_to_scan); | |
1499 | ||
1500 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
1501 | char *buf) | |
1502 | { | |
1503 | return sprintf(buf, "%u\n", ksm_run); | |
1504 | } | |
1505 | ||
1506 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
1507 | const char *buf, size_t count) | |
1508 | { | |
1509 | int err; | |
1510 | unsigned long flags; | |
1511 | ||
1512 | err = strict_strtoul(buf, 10, &flags); | |
1513 | if (err || flags > UINT_MAX) | |
1514 | return -EINVAL; | |
1515 | if (flags > KSM_RUN_UNMERGE) | |
1516 | return -EINVAL; | |
1517 | ||
1518 | /* | |
1519 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
1520 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
b4028260 | 1521 | * breaking COW to free the unswappable pages_shared (but leaves |
31dbd01f IE |
1522 | * mm_slots on the list for when ksmd may be set running again). |
1523 | */ | |
1524 | ||
1525 | mutex_lock(&ksm_thread_mutex); | |
1526 | if (ksm_run != flags) { | |
1527 | ksm_run = flags; | |
d952b791 | 1528 | if (flags & KSM_RUN_UNMERGE) { |
35451bee | 1529 | current->flags |= PF_OOM_ORIGIN; |
d952b791 | 1530 | err = unmerge_and_remove_all_rmap_items(); |
35451bee | 1531 | current->flags &= ~PF_OOM_ORIGIN; |
d952b791 HD |
1532 | if (err) { |
1533 | ksm_run = KSM_RUN_STOP; | |
1534 | count = err; | |
1535 | } | |
1536 | } | |
31dbd01f IE |
1537 | } |
1538 | mutex_unlock(&ksm_thread_mutex); | |
1539 | ||
1540 | if (flags & KSM_RUN_MERGE) | |
1541 | wake_up_interruptible(&ksm_thread_wait); | |
1542 | ||
1543 | return count; | |
1544 | } | |
1545 | KSM_ATTR(run); | |
1546 | ||
31dbd01f IE |
1547 | static ssize_t max_kernel_pages_store(struct kobject *kobj, |
1548 | struct kobj_attribute *attr, | |
1549 | const char *buf, size_t count) | |
1550 | { | |
1551 | int err; | |
1552 | unsigned long nr_pages; | |
1553 | ||
1554 | err = strict_strtoul(buf, 10, &nr_pages); | |
1555 | if (err) | |
1556 | return -EINVAL; | |
1557 | ||
1558 | ksm_max_kernel_pages = nr_pages; | |
1559 | ||
1560 | return count; | |
1561 | } | |
1562 | ||
1563 | static ssize_t max_kernel_pages_show(struct kobject *kobj, | |
1564 | struct kobj_attribute *attr, char *buf) | |
1565 | { | |
1566 | return sprintf(buf, "%lu\n", ksm_max_kernel_pages); | |
1567 | } | |
1568 | KSM_ATTR(max_kernel_pages); | |
1569 | ||
b4028260 HD |
1570 | static ssize_t pages_shared_show(struct kobject *kobj, |
1571 | struct kobj_attribute *attr, char *buf) | |
1572 | { | |
1573 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
1574 | } | |
1575 | KSM_ATTR_RO(pages_shared); | |
1576 | ||
1577 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
1578 | struct kobj_attribute *attr, char *buf) | |
1579 | { | |
e178dfde | 1580 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
1581 | } |
1582 | KSM_ATTR_RO(pages_sharing); | |
1583 | ||
473b0ce4 HD |
1584 | static ssize_t pages_unshared_show(struct kobject *kobj, |
1585 | struct kobj_attribute *attr, char *buf) | |
1586 | { | |
1587 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
1588 | } | |
1589 | KSM_ATTR_RO(pages_unshared); | |
1590 | ||
1591 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
1592 | struct kobj_attribute *attr, char *buf) | |
1593 | { | |
1594 | long ksm_pages_volatile; | |
1595 | ||
1596 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
1597 | - ksm_pages_sharing - ksm_pages_unshared; | |
1598 | /* | |
1599 | * It was not worth any locking to calculate that statistic, | |
1600 | * but it might therefore sometimes be negative: conceal that. | |
1601 | */ | |
1602 | if (ksm_pages_volatile < 0) | |
1603 | ksm_pages_volatile = 0; | |
1604 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
1605 | } | |
1606 | KSM_ATTR_RO(pages_volatile); | |
1607 | ||
1608 | static ssize_t full_scans_show(struct kobject *kobj, | |
1609 | struct kobj_attribute *attr, char *buf) | |
1610 | { | |
1611 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
1612 | } | |
1613 | KSM_ATTR_RO(full_scans); | |
1614 | ||
31dbd01f IE |
1615 | static struct attribute *ksm_attrs[] = { |
1616 | &sleep_millisecs_attr.attr, | |
1617 | &pages_to_scan_attr.attr, | |
1618 | &run_attr.attr, | |
31dbd01f | 1619 | &max_kernel_pages_attr.attr, |
b4028260 HD |
1620 | &pages_shared_attr.attr, |
1621 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
1622 | &pages_unshared_attr.attr, |
1623 | &pages_volatile_attr.attr, | |
1624 | &full_scans_attr.attr, | |
31dbd01f IE |
1625 | NULL, |
1626 | }; | |
1627 | ||
1628 | static struct attribute_group ksm_attr_group = { | |
1629 | .attrs = ksm_attrs, | |
1630 | .name = "ksm", | |
1631 | }; | |
2ffd8679 | 1632 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1633 | |
1634 | static int __init ksm_init(void) | |
1635 | { | |
1636 | struct task_struct *ksm_thread; | |
1637 | int err; | |
1638 | ||
c73602ad | 1639 | ksm_max_kernel_pages = totalram_pages / 4; |
2c6854fd | 1640 | |
31dbd01f IE |
1641 | err = ksm_slab_init(); |
1642 | if (err) | |
1643 | goto out; | |
1644 | ||
1645 | err = mm_slots_hash_init(); | |
1646 | if (err) | |
1647 | goto out_free1; | |
1648 | ||
1649 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); | |
1650 | if (IS_ERR(ksm_thread)) { | |
1651 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
1652 | err = PTR_ERR(ksm_thread); | |
1653 | goto out_free2; | |
1654 | } | |
1655 | ||
2ffd8679 | 1656 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
1657 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
1658 | if (err) { | |
1659 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 HD |
1660 | kthread_stop(ksm_thread); |
1661 | goto out_free2; | |
31dbd01f | 1662 | } |
c73602ad HD |
1663 | #else |
1664 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
1665 | ||
2ffd8679 | 1666 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
1667 | |
1668 | return 0; | |
1669 | ||
31dbd01f IE |
1670 | out_free2: |
1671 | mm_slots_hash_free(); | |
1672 | out_free1: | |
1673 | ksm_slab_free(); | |
1674 | out: | |
1675 | return err; | |
f8af4da3 | 1676 | } |
31dbd01f | 1677 | module_init(ksm_init) |