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1 | /* |
2 | * mm/rmap.c - physical to virtual reverse mappings |
3 | * |
4 | * Copyright 2001, Rik van Riel <riel@conectiva.com.br> |
5 | * Released under the General Public License (GPL). |
6 | * |
7 | * Simple, low overhead reverse mapping scheme. |
8 | * Please try to keep this thing as modular as possible. |
9 | * |
10 | * Provides methods for unmapping each kind of mapped page: |
11 | * the anon methods track anonymous pages, and |
12 | * the file methods track pages belonging to an inode. |
13 | * |
14 | * Original design by Rik van Riel <riel@conectiva.com.br> 2001 |
15 | * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004 |
16 | * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004 |
17 | * Contributions by Hugh Dickins 2003, 2004 |
18 | */ |
19 | |
20 | /* |
21 | * Lock ordering in mm: |
22 | * |
23 | * inode->i_mutex (while writing or truncating, not reading or faulting) |
24 | * mm->mmap_sem |
25 | * page->flags PG_locked (lock_page) |
26 | * mapping->i_mmap_mutex |
27 | * anon_vma->mutex |
28 | * mm->page_table_lock or pte_lock |
29 | * zone->lru_lock (in mark_page_accessed, isolate_lru_page) |
30 | * swap_lock (in swap_duplicate, swap_info_get) |
31 | * mmlist_lock (in mmput, drain_mmlist and others) |
32 | * mapping->private_lock (in __set_page_dirty_buffers) |
33 | * inode->i_lock (in set_page_dirty's __mark_inode_dirty) |
34 | * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty) |
35 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
36 | * mapping->tree_lock (widely used, in set_page_dirty, |
37 | * in arch-dependent flush_dcache_mmap_lock, |
38 | * within bdi.wb->list_lock in __sync_single_inode) |
39 | * |
40 | * anon_vma->mutex,mapping->i_mutex (memory_failure, collect_procs_anon) |
41 | * ->tasklist_lock |
42 | * pte map lock |
43 | */ |
44 | |
45 | #include <linux/mm.h> |
46 | #include <linux/pagemap.h> |
47 | #include <linux/swap.h> |
48 | #include <linux/swapops.h> |
49 | #include <linux/slab.h> |
50 | #include <linux/init.h> |
51 | #include <linux/ksm.h> |
52 | #include <linux/rmap.h> |
53 | #include <linux/rcupdate.h> |
54 | #include <linux/export.h> |
55 | #include <linux/memcontrol.h> |
56 | #include <linux/mmu_notifier.h> |
57 | #include <linux/migrate.h> |
58 | #include <linux/hugetlb.h> |
59 | |
60 | #include <asm/tlbflush.h> |
61 | |
62 | #include "internal.h" |
63 | |
64 | static struct kmem_cache *anon_vma_cachep; |
65 | static struct kmem_cache *anon_vma_chain_cachep; |
66 | |
67 | static inline struct anon_vma *anon_vma_alloc(void) |
68 | { |
69 | struct anon_vma *anon_vma; |
70 | |
71 | anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
72 | if (anon_vma) { |
73 | atomic_set(&anon_vma->refcount, 1); |
74 | /* |
75 | * Initialise the anon_vma root to point to itself. If called |
76 | * from fork, the root will be reset to the parents anon_vma. |
77 | */ |
78 | anon_vma->root = anon_vma; |
79 | } |
80 | |
81 | return anon_vma; |
82 | } |
83 | |
84 | static inline void anon_vma_free(struct anon_vma *anon_vma) |
85 | { |
86 | VM_BUG_ON(atomic_read(&anon_vma->refcount)); |
87 | |
88 | /* |
89 | * Synchronize against page_lock_anon_vma() such that |
90 | * we can safely hold the lock without the anon_vma getting |
91 | * freed. |
92 | * |
93 | * Relies on the full mb implied by the atomic_dec_and_test() from |
94 | * put_anon_vma() against the acquire barrier implied by |
95 | * mutex_trylock() from page_lock_anon_vma(). This orders: |
96 | * |
97 | * page_lock_anon_vma() VS put_anon_vma() |
98 | * mutex_trylock() atomic_dec_and_test() |
99 | * LOCK MB |
100 | * atomic_read() mutex_is_locked() |
101 | * |
102 | * LOCK should suffice since the actual taking of the lock must |
103 | * happen _before_ what follows. |
104 | */ |
105 | if (mutex_is_locked(&anon_vma->root->mutex)) { |
106 | anon_vma_lock(anon_vma); |
107 | anon_vma_unlock(anon_vma); |
108 | } |
109 | |
110 | kmem_cache_free(anon_vma_cachep, anon_vma); |
111 | } |
112 | |
113 | static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp) |
114 | { |
115 | return kmem_cache_alloc(anon_vma_chain_cachep, gfp); |
116 | } |
117 | |
118 | static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
119 | { |
120 | kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); |
121 | } |
122 | |
123 | static void anon_vma_chain_link(struct vm_area_struct *vma, |
124 | struct anon_vma_chain *avc, |
125 | struct anon_vma *anon_vma) |
126 | { |
127 | avc->vma = vma; |
128 | avc->anon_vma = anon_vma; |
129 | list_add(&avc->same_vma, &vma->anon_vma_chain); |
130 | |
131 | /* |
132 | * It's critical to add new vmas to the tail of the anon_vma, |
133 | * see comment in huge_memory.c:__split_huge_page(). |
134 | */ |
135 | list_add_tail(&avc->same_anon_vma, &anon_vma->head); |
136 | } |
137 | |
138 | /** |
139 | * anon_vma_prepare - attach an anon_vma to a memory region |
140 | * @vma: the memory region in question |
141 | * |
142 | * This makes sure the memory mapping described by 'vma' has |
143 | * an 'anon_vma' attached to it, so that we can associate the |
144 | * anonymous pages mapped into it with that anon_vma. |
145 | * |
146 | * The common case will be that we already have one, but if |
147 | * not we either need to find an adjacent mapping that we |
148 | * can re-use the anon_vma from (very common when the only |
149 | * reason for splitting a vma has been mprotect()), or we |
150 | * allocate a new one. |
151 | * |
152 | * Anon-vma allocations are very subtle, because we may have |
153 | * optimistically looked up an anon_vma in page_lock_anon_vma() |
154 | * and that may actually touch the spinlock even in the newly |
155 | * allocated vma (it depends on RCU to make sure that the |
156 | * anon_vma isn't actually destroyed). |
157 | * |
158 | * As a result, we need to do proper anon_vma locking even |
159 | * for the new allocation. At the same time, we do not want |
160 | * to do any locking for the common case of already having |
161 | * an anon_vma. |
162 | * |
163 | * This must be called with the mmap_sem held for reading. |
164 | */ |
165 | int anon_vma_prepare(struct vm_area_struct *vma) |
166 | { |
167 | struct anon_vma *anon_vma = vma->anon_vma; |
168 | struct anon_vma_chain *avc; |
169 | |
170 | might_sleep(); |
171 | if (unlikely(!anon_vma)) { |
172 | struct mm_struct *mm = vma->vm_mm; |
173 | struct anon_vma *allocated; |
174 | |
175 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
176 | if (!avc) |
177 | goto out_enomem; |
178 | |
179 | anon_vma = find_mergeable_anon_vma(vma); |
180 | allocated = NULL; |
181 | if (!anon_vma) { |
182 | anon_vma = anon_vma_alloc(); |
183 | if (unlikely(!anon_vma)) |
184 | goto out_enomem_free_avc; |
185 | allocated = anon_vma; |
186 | } |
187 | |
188 | anon_vma_lock(anon_vma); |
189 | /* page_table_lock to protect against threads */ |
190 | spin_lock(&mm->page_table_lock); |
191 | if (likely(!vma->anon_vma)) { |
192 | vma->anon_vma = anon_vma; |
193 | anon_vma_chain_link(vma, avc, anon_vma); |
194 | allocated = NULL; |
195 | avc = NULL; |
196 | } |
197 | spin_unlock(&mm->page_table_lock); |
198 | anon_vma_unlock(anon_vma); |
199 | |
200 | if (unlikely(allocated)) |
201 | put_anon_vma(allocated); |
202 | if (unlikely(avc)) |
203 | anon_vma_chain_free(avc); |
204 | } |
205 | return 0; |
206 | |
207 | out_enomem_free_avc: |
208 | anon_vma_chain_free(avc); |
209 | out_enomem: |
210 | return -ENOMEM; |
211 | } |
212 | |
213 | /* |
214 | * This is a useful helper function for locking the anon_vma root as |
215 | * we traverse the vma->anon_vma_chain, looping over anon_vma's that |
216 | * have the same vma. |
217 | * |
218 | * Such anon_vma's should have the same root, so you'd expect to see |
219 | * just a single mutex_lock for the whole traversal. |
220 | */ |
221 | static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) |
222 | { |
223 | struct anon_vma *new_root = anon_vma->root; |
224 | if (new_root != root) { |
225 | if (WARN_ON_ONCE(root)) |
226 | mutex_unlock(&root->mutex); |
227 | root = new_root; |
228 | mutex_lock(&root->mutex); |
229 | } |
230 | return root; |
231 | } |
232 | |
233 | static inline void unlock_anon_vma_root(struct anon_vma *root) |
234 | { |
235 | if (root) |
236 | mutex_unlock(&root->mutex); |
237 | } |
238 | |
239 | /* |
240 | * Attach the anon_vmas from src to dst. |
241 | * Returns 0 on success, -ENOMEM on failure. |
242 | */ |
243 | int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
244 | { |
245 | struct anon_vma_chain *avc, *pavc; |
246 | struct anon_vma *root = NULL; |
247 | |
248 | list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
249 | struct anon_vma *anon_vma; |
250 | |
251 | avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); |
252 | if (unlikely(!avc)) { |
253 | unlock_anon_vma_root(root); |
254 | root = NULL; |
255 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
256 | if (!avc) |
257 | goto enomem_failure; |
258 | } |
259 | anon_vma = pavc->anon_vma; |
260 | root = lock_anon_vma_root(root, anon_vma); |
261 | anon_vma_chain_link(dst, avc, anon_vma); |
262 | } |
263 | unlock_anon_vma_root(root); |
264 | return 0; |
265 | |
266 | enomem_failure: |
267 | unlink_anon_vmas(dst); |
268 | return -ENOMEM; |
269 | } |
270 | |
271 | /* |
272 | * Some rmap walk that needs to find all ptes/hugepmds without false |
273 | * negatives (like migrate and split_huge_page) running concurrent |
274 | * with operations that copy or move pagetables (like mremap() and |
275 | * fork()) to be safe. They depend on the anon_vma "same_anon_vma" |
276 | * list to be in a certain order: the dst_vma must be placed after the |
277 | * src_vma in the list. This is always guaranteed by fork() but |
278 | * mremap() needs to call this function to enforce it in case the |
279 | * dst_vma isn't newly allocated and chained with the anon_vma_clone() |
280 | * function but just an extension of a pre-existing vma through |
281 | * vma_merge. |
282 | * |
283 | * NOTE: the same_anon_vma list can still be changed by other |
284 | * processes while mremap runs because mremap doesn't hold the |
285 | * anon_vma mutex to prevent modifications to the list while it |
286 | * runs. All we need to enforce is that the relative order of this |
287 | * process vmas isn't changing (we don't care about other vmas |
288 | * order). Each vma corresponds to an anon_vma_chain structure so |
289 | * there's no risk that other processes calling anon_vma_moveto_tail() |
290 | * and changing the same_anon_vma list under mremap() will screw with |
291 | * the relative order of this process vmas in the list, because we |
292 | * they can't alter the order of any vma that belongs to this |
293 | * process. And there can't be another anon_vma_moveto_tail() running |
294 | * concurrently with mremap() coming from this process because we hold |
295 | * the mmap_sem for the whole mremap(). fork() ordering dependency |
296 | * also shouldn't be affected because fork() only cares that the |
297 | * parent vmas are placed in the list before the child vmas and |
298 | * anon_vma_moveto_tail() won't reorder vmas from either the fork() |
299 | * parent or child. |
300 | */ |
301 | void anon_vma_moveto_tail(struct vm_area_struct *dst) |
302 | { |
303 | struct anon_vma_chain *pavc; |
304 | struct anon_vma *root = NULL; |
305 | |
306 | list_for_each_entry_reverse(pavc, &dst->anon_vma_chain, same_vma) { |
307 | struct anon_vma *anon_vma = pavc->anon_vma; |
308 | VM_BUG_ON(pavc->vma != dst); |
309 | root = lock_anon_vma_root(root, anon_vma); |
310 | list_del(&pavc->same_anon_vma); |
311 | list_add_tail(&pavc->same_anon_vma, &anon_vma->head); |
312 | } |
313 | unlock_anon_vma_root(root); |
314 | } |
315 | |
316 | /* |
317 | * Attach vma to its own anon_vma, as well as to the anon_vmas that |
318 | * the corresponding VMA in the parent process is attached to. |
319 | * Returns 0 on success, non-zero on failure. |
320 | */ |
321 | int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
322 | { |
323 | struct anon_vma_chain *avc; |
324 | struct anon_vma *anon_vma; |
325 | |
326 | /* Don't bother if the parent process has no anon_vma here. */ |
327 | if (!pvma->anon_vma) |
328 | return 0; |
329 | |
330 | /* |
331 | * First, attach the new VMA to the parent VMA's anon_vmas, |
332 | * so rmap can find non-COWed pages in child processes. |
333 | */ |
334 | if (anon_vma_clone(vma, pvma)) |
335 | return -ENOMEM; |
336 | |
337 | /* Then add our own anon_vma. */ |
338 | anon_vma = anon_vma_alloc(); |
339 | if (!anon_vma) |
340 | goto out_error; |
341 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
342 | if (!avc) |
343 | goto out_error_free_anon_vma; |
344 | |
345 | /* |
346 | * The root anon_vma's spinlock is the lock actually used when we |
347 | * lock any of the anon_vmas in this anon_vma tree. |
348 | */ |
349 | anon_vma->root = pvma->anon_vma->root; |
350 | /* |
351 | * With refcounts, an anon_vma can stay around longer than the |
352 | * process it belongs to. The root anon_vma needs to be pinned until |
353 | * this anon_vma is freed, because the lock lives in the root. |
354 | */ |
355 | get_anon_vma(anon_vma->root); |
356 | /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
357 | vma->anon_vma = anon_vma; |
358 | anon_vma_lock(anon_vma); |
359 | anon_vma_chain_link(vma, avc, anon_vma); |
360 | anon_vma_unlock(anon_vma); |
361 | |
362 | return 0; |
363 | |
364 | out_error_free_anon_vma: |
365 | put_anon_vma(anon_vma); |
366 | out_error: |
367 | unlink_anon_vmas(vma); |
368 | return -ENOMEM; |
369 | } |
370 | |
371 | void unlink_anon_vmas(struct vm_area_struct *vma) |
372 | { |
373 | struct anon_vma_chain *avc, *next; |
374 | struct anon_vma *root = NULL; |
375 | |
376 | /* |
377 | * Unlink each anon_vma chained to the VMA. This list is ordered |
378 | * from newest to oldest, ensuring the root anon_vma gets freed last. |
379 | */ |
380 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
381 | struct anon_vma *anon_vma = avc->anon_vma; |
382 | |
383 | root = lock_anon_vma_root(root, anon_vma); |
384 | list_del(&avc->same_anon_vma); |
385 | |
386 | /* |
387 | * Leave empty anon_vmas on the list - we'll need |
388 | * to free them outside the lock. |
389 | */ |
390 | if (list_empty(&anon_vma->head)) |
391 | continue; |
392 | |
393 | list_del(&avc->same_vma); |
394 | anon_vma_chain_free(avc); |
395 | } |
396 | unlock_anon_vma_root(root); |
397 | |
398 | /* |
399 | * Iterate the list once more, it now only contains empty and unlinked |
400 | * anon_vmas, destroy them. Could not do before due to __put_anon_vma() |
401 | * needing to acquire the anon_vma->root->mutex. |
402 | */ |
403 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
404 | struct anon_vma *anon_vma = avc->anon_vma; |
405 | |
406 | put_anon_vma(anon_vma); |
407 | |
408 | list_del(&avc->same_vma); |
409 | anon_vma_chain_free(avc); |
410 | } |
411 | } |
412 | |
413 | static void anon_vma_ctor(void *data) |
414 | { |
415 | struct anon_vma *anon_vma = data; |
416 | |
417 | mutex_init(&anon_vma->mutex); |
418 | atomic_set(&anon_vma->refcount, 0); |
419 | INIT_LIST_HEAD(&anon_vma->head); |
420 | } |
421 | |
422 | void __init anon_vma_init(void) |
423 | { |
424 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), |
425 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor); |
426 | anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC); |
427 | } |
428 | |
429 | /* |
430 | * Getting a lock on a stable anon_vma from a page off the LRU is tricky! |
431 | * |
432 | * Since there is no serialization what so ever against page_remove_rmap() |
433 | * the best this function can do is return a locked anon_vma that might |
434 | * have been relevant to this page. |
435 | * |
436 | * The page might have been remapped to a different anon_vma or the anon_vma |
437 | * returned may already be freed (and even reused). |
438 | * |
439 | * In case it was remapped to a different anon_vma, the new anon_vma will be a |
440 | * child of the old anon_vma, and the anon_vma lifetime rules will therefore |
441 | * ensure that any anon_vma obtained from the page will still be valid for as |
442 | * long as we observe page_mapped() [ hence all those page_mapped() tests ]. |
443 | * |
444 | * All users of this function must be very careful when walking the anon_vma |
445 | * chain and verify that the page in question is indeed mapped in it |
446 | * [ something equivalent to page_mapped_in_vma() ]. |
447 | * |
448 | * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap() |
449 | * that the anon_vma pointer from page->mapping is valid if there is a |
450 | * mapcount, we can dereference the anon_vma after observing those. |
451 | */ |
452 | struct anon_vma *page_get_anon_vma(struct page *page) |
453 | { |
454 | struct anon_vma *anon_vma = NULL; |
455 | unsigned long anon_mapping; |
456 | |
457 | rcu_read_lock(); |
458 | anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping); |
459 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
460 | goto out; |
461 | if (!page_mapped(page)) |
462 | goto out; |
463 | |
464 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
465 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
466 | anon_vma = NULL; |
467 | goto out; |
468 | } |
469 | |
470 | /* |
471 | * If this page is still mapped, then its anon_vma cannot have been |
472 | * freed. But if it has been unmapped, we have no security against the |
473 | * anon_vma structure being freed and reused (for another anon_vma: |
474 | * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero() |
475 | * above cannot corrupt). |
476 | */ |
477 | if (!page_mapped(page)) { |
478 | put_anon_vma(anon_vma); |
479 | anon_vma = NULL; |
480 | } |
481 | out: |
482 | rcu_read_unlock(); |
483 | |
484 | return anon_vma; |
485 | } |
486 | |
487 | /* |
488 | * Similar to page_get_anon_vma() except it locks the anon_vma. |
489 | * |
490 | * Its a little more complex as it tries to keep the fast path to a single |
491 | * atomic op -- the trylock. If we fail the trylock, we fall back to getting a |
492 | * reference like with page_get_anon_vma() and then block on the mutex. |
493 | */ |
494 | struct anon_vma *page_lock_anon_vma(struct page *page) |
495 | { |
496 | struct anon_vma *anon_vma = NULL; |
497 | struct anon_vma *root_anon_vma; |
498 | unsigned long anon_mapping; |
499 | |
500 | rcu_read_lock(); |
501 | anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping); |
502 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
503 | goto out; |
504 | if (!page_mapped(page)) |
505 | goto out; |
506 | |
507 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
508 | root_anon_vma = ACCESS_ONCE(anon_vma->root); |
509 | if (mutex_trylock(&root_anon_vma->mutex)) { |
510 | /* |
511 | * If the page is still mapped, then this anon_vma is still |
512 | * its anon_vma, and holding the mutex ensures that it will |
513 | * not go away, see anon_vma_free(). |
514 | */ |
515 | if (!page_mapped(page)) { |
516 | mutex_unlock(&root_anon_vma->mutex); |
517 | anon_vma = NULL; |
518 | } |
519 | goto out; |
520 | } |
521 | |
522 | /* trylock failed, we got to sleep */ |
523 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
524 | anon_vma = NULL; |
525 | goto out; |
526 | } |
527 | |
528 | if (!page_mapped(page)) { |
529 | put_anon_vma(anon_vma); |
530 | anon_vma = NULL; |
531 | goto out; |
532 | } |
533 | |
534 | /* we pinned the anon_vma, its safe to sleep */ |
535 | rcu_read_unlock(); |
536 | anon_vma_lock(anon_vma); |
537 | |
538 | if (atomic_dec_and_test(&anon_vma->refcount)) { |
539 | /* |
540 | * Oops, we held the last refcount, release the lock |
541 | * and bail -- can't simply use put_anon_vma() because |
542 | * we'll deadlock on the anon_vma_lock() recursion. |
543 | */ |
544 | anon_vma_unlock(anon_vma); |
545 | __put_anon_vma(anon_vma); |
546 | anon_vma = NULL; |
547 | } |
548 | |
549 | return anon_vma; |
550 | |
551 | out: |
552 | rcu_read_unlock(); |
553 | return anon_vma; |
554 | } |
555 | |
556 | void page_unlock_anon_vma(struct anon_vma *anon_vma) |
557 | { |
558 | anon_vma_unlock(anon_vma); |
559 | } |
560 | |
561 | /* |
562 | * At what user virtual address is page expected in @vma? |
563 | * Returns virtual address or -EFAULT if page's index/offset is not |
564 | * within the range mapped the @vma. |
565 | */ |
566 | inline unsigned long |
567 | vma_address(struct page *page, struct vm_area_struct *vma) |
568 | { |
569 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
570 | unsigned long address; |
571 | |
572 | if (unlikely(is_vm_hugetlb_page(vma))) |
573 | pgoff = page->index << huge_page_order(page_hstate(page)); |
574 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
575 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { |
576 | /* page should be within @vma mapping range */ |
577 | return -EFAULT; |
578 | } |
579 | return address; |
580 | } |
581 | |
582 | /* |
583 | * At what user virtual address is page expected in vma? |
584 | * Caller should check the page is actually part of the vma. |
585 | */ |
586 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
587 | { |
588 | if (PageAnon(page)) { |
589 | struct anon_vma *page__anon_vma = page_anon_vma(page); |
590 | /* |
591 | * Note: swapoff's unuse_vma() is more efficient with this |
592 | * check, and needs it to match anon_vma when KSM is active. |
593 | */ |
594 | if (!vma->anon_vma || !page__anon_vma || |
595 | vma->anon_vma->root != page__anon_vma->root) |
596 | return -EFAULT; |
597 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { |
598 | if (!vma->vm_file || |
599 | vma->vm_file->f_mapping != page->mapping) |
600 | return -EFAULT; |
601 | } else |
602 | return -EFAULT; |
603 | return vma_address(page, vma); |
604 | } |
605 | |
606 | /* |
607 | * Check that @page is mapped at @address into @mm. |
608 | * |
609 | * If @sync is false, page_check_address may perform a racy check to avoid |
610 | * the page table lock when the pte is not present (helpful when reclaiming |
611 | * highly shared pages). |
612 | * |
613 | * On success returns with pte mapped and locked. |
614 | */ |
615 | pte_t *__page_check_address(struct page *page, struct mm_struct *mm, |
616 | unsigned long address, spinlock_t **ptlp, int sync) |
617 | { |
618 | pgd_t *pgd; |
619 | pud_t *pud; |
620 | pmd_t *pmd; |
621 | pte_t *pte; |
622 | spinlock_t *ptl; |
623 | |
624 | if (unlikely(PageHuge(page))) { |
625 | pte = huge_pte_offset(mm, address); |
626 | ptl = &mm->page_table_lock; |
627 | goto check; |
628 | } |
629 | |
630 | pgd = pgd_offset(mm, address); |
631 | if (!pgd_present(*pgd)) |
632 | return NULL; |
633 | |
634 | pud = pud_offset(pgd, address); |
635 | if (!pud_present(*pud)) |
636 | return NULL; |
637 | |
638 | pmd = pmd_offset(pud, address); |
639 | if (!pmd_present(*pmd)) |
640 | return NULL; |
641 | if (pmd_trans_huge(*pmd)) |
642 | return NULL; |
643 | |
644 | pte = pte_offset_map(pmd, address); |
645 | /* Make a quick check before getting the lock */ |
646 | if (!sync && !pte_present(*pte)) { |
647 | pte_unmap(pte); |
648 | return NULL; |
649 | } |
650 | |
651 | ptl = pte_lockptr(mm, pmd); |
652 | check: |
653 | spin_lock(ptl); |
654 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { |
655 | *ptlp = ptl; |
656 | return pte; |
657 | } |
658 | pte_unmap_unlock(pte, ptl); |
659 | return NULL; |
660 | } |
661 | |
662 | /** |
663 | * page_mapped_in_vma - check whether a page is really mapped in a VMA |
664 | * @page: the page to test |
665 | * @vma: the VMA to test |
666 | * |
667 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 |
668 | * if the page is not mapped into the page tables of this VMA. Only |
669 | * valid for normal file or anonymous VMAs. |
670 | */ |
671 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) |
672 | { |
673 | unsigned long address; |
674 | pte_t *pte; |
675 | spinlock_t *ptl; |
676 | |
677 | address = vma_address(page, vma); |
678 | if (address == -EFAULT) /* out of vma range */ |
679 | return 0; |
680 | pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); |
681 | if (!pte) /* the page is not in this mm */ |
682 | return 0; |
683 | pte_unmap_unlock(pte, ptl); |
684 | |
685 | return 1; |
686 | } |
687 | |
688 | /* |
689 | * Subfunctions of page_referenced: page_referenced_one called |
690 | * repeatedly from either page_referenced_anon or page_referenced_file. |
691 | */ |
692 | int page_referenced_one(struct page *page, struct vm_area_struct *vma, |
693 | unsigned long address, unsigned int *mapcount, |
694 | unsigned long *vm_flags) |
695 | { |
696 | struct mm_struct *mm = vma->vm_mm; |
697 | int referenced = 0; |
698 | |
699 | if (unlikely(PageTransHuge(page))) { |
700 | pmd_t *pmd; |
701 | |
702 | spin_lock(&mm->page_table_lock); |
703 | /* |
704 | * rmap might return false positives; we must filter |
705 | * these out using page_check_address_pmd(). |
706 | */ |
707 | pmd = page_check_address_pmd(page, mm, address, |
708 | PAGE_CHECK_ADDRESS_PMD_FLAG); |
709 | if (!pmd) { |
710 | spin_unlock(&mm->page_table_lock); |
711 | goto out; |
712 | } |
713 | |
714 | if (vma->vm_flags & VM_LOCKED) { |
715 | spin_unlock(&mm->page_table_lock); |
716 | *mapcount = 0; /* break early from loop */ |
717 | *vm_flags |= VM_LOCKED; |
718 | goto out; |
719 | } |
720 | |
721 | /* go ahead even if the pmd is pmd_trans_splitting() */ |
722 | if (pmdp_clear_flush_young_notify(vma, address, pmd)) |
723 | referenced++; |
724 | spin_unlock(&mm->page_table_lock); |
725 | } else { |
726 | pte_t *pte; |
727 | spinlock_t *ptl; |
728 | |
729 | /* |
730 | * rmap might return false positives; we must filter |
731 | * these out using page_check_address(). |
732 | */ |
733 | pte = page_check_address(page, mm, address, &ptl, 0); |
734 | if (!pte) |
735 | goto out; |
736 | |
737 | if (vma->vm_flags & VM_LOCKED) { |
738 | pte_unmap_unlock(pte, ptl); |
739 | *mapcount = 0; /* break early from loop */ |
740 | *vm_flags |= VM_LOCKED; |
741 | goto out; |
742 | } |
743 | |
744 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
745 | /* |
746 | * Don't treat a reference through a sequentially read |
747 | * mapping as such. If the page has been used in |
748 | * another mapping, we will catch it; if this other |
749 | * mapping is already gone, the unmap path will have |
750 | * set PG_referenced or activated the page. |
751 | */ |
752 | if (likely(!VM_SequentialReadHint(vma))) |
753 | referenced++; |
754 | } |
755 | pte_unmap_unlock(pte, ptl); |
756 | } |
757 | |
758 | /* Pretend the page is referenced if the task has the |
759 | swap token and is in the middle of a page fault. */ |
760 | if (mm != current->mm && has_swap_token(mm) && |
761 | rwsem_is_locked(&mm->mmap_sem)) |
762 | referenced++; |
763 | |
764 | (*mapcount)--; |
765 | |
766 | if (referenced) |
767 | *vm_flags |= vma->vm_flags; |
768 | out: |
769 | return referenced; |
770 | } |
771 | |
772 | static int page_referenced_anon(struct page *page, |
773 | struct mem_cgroup *memcg, |
774 | unsigned long *vm_flags) |
775 | { |
776 | unsigned int mapcount; |
777 | struct anon_vma *anon_vma; |
778 | struct anon_vma_chain *avc; |
779 | int referenced = 0; |
780 | |
781 | anon_vma = page_lock_anon_vma(page); |
782 | if (!anon_vma) |
783 | return referenced; |
784 | |
785 | mapcount = page_mapcount(page); |
786 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
787 | struct vm_area_struct *vma = avc->vma; |
788 | unsigned long address = vma_address(page, vma); |
789 | if (address == -EFAULT) |
790 | continue; |
791 | /* |
792 | * If we are reclaiming on behalf of a cgroup, skip |
793 | * counting on behalf of references from different |
794 | * cgroups |
795 | */ |
796 | if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) |
797 | continue; |
798 | referenced += page_referenced_one(page, vma, address, |
799 | &mapcount, vm_flags); |
800 | if (!mapcount) |
801 | break; |
802 | } |
803 | |
804 | page_unlock_anon_vma(anon_vma); |
805 | return referenced; |
806 | } |
807 | |
808 | /** |
809 | * page_referenced_file - referenced check for object-based rmap |
810 | * @page: the page we're checking references on. |
811 | * @memcg: target memory control group |
812 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
813 | * |
814 | * For an object-based mapped page, find all the places it is mapped and |
815 | * check/clear the referenced flag. This is done by following the page->mapping |
816 | * pointer, then walking the chain of vmas it holds. It returns the number |
817 | * of references it found. |
818 | * |
819 | * This function is only called from page_referenced for object-based pages. |
820 | */ |
821 | static int page_referenced_file(struct page *page, |
822 | struct mem_cgroup *memcg, |
823 | unsigned long *vm_flags) |
824 | { |
825 | unsigned int mapcount; |
826 | struct address_space *mapping = page->mapping; |
827 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
828 | struct vm_area_struct *vma; |
829 | struct prio_tree_iter iter; |
830 | int referenced = 0; |
831 | |
832 | /* |
833 | * The caller's checks on page->mapping and !PageAnon have made |
834 | * sure that this is a file page: the check for page->mapping |
835 | * excludes the case just before it gets set on an anon page. |
836 | */ |
837 | BUG_ON(PageAnon(page)); |
838 | |
839 | /* |
840 | * The page lock not only makes sure that page->mapping cannot |
841 | * suddenly be NULLified by truncation, it makes sure that the |
842 | * structure at mapping cannot be freed and reused yet, |
843 | * so we can safely take mapping->i_mmap_mutex. |
844 | */ |
845 | BUG_ON(!PageLocked(page)); |
846 | |
847 | mutex_lock(&mapping->i_mmap_mutex); |
848 | |
849 | /* |
850 | * i_mmap_mutex does not stabilize mapcount at all, but mapcount |
851 | * is more likely to be accurate if we note it after spinning. |
852 | */ |
853 | mapcount = page_mapcount(page); |
854 | |
855 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
856 | unsigned long address = vma_address(page, vma); |
857 | if (address == -EFAULT) |
858 | continue; |
859 | /* |
860 | * If we are reclaiming on behalf of a cgroup, skip |
861 | * counting on behalf of references from different |
862 | * cgroups |
863 | */ |
864 | if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) |
865 | continue; |
866 | referenced += page_referenced_one(page, vma, address, |
867 | &mapcount, vm_flags); |
868 | if (!mapcount) |
869 | break; |
870 | } |
871 | |
872 | mutex_unlock(&mapping->i_mmap_mutex); |
873 | return referenced; |
874 | } |
875 | |
876 | /** |
877 | * page_referenced - test if the page was referenced |
878 | * @page: the page to test |
879 | * @is_locked: caller holds lock on the page |
880 | * @memcg: target memory cgroup |
881 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
882 | * |
883 | * Quick test_and_clear_referenced for all mappings to a page, |
884 | * returns the number of ptes which referenced the page. |
885 | */ |
886 | int page_referenced(struct page *page, |
887 | int is_locked, |
888 | struct mem_cgroup *memcg, |
889 | unsigned long *vm_flags) |
890 | { |
891 | int referenced = 0; |
892 | int we_locked = 0; |
893 | |
894 | *vm_flags = 0; |
895 | if (page_mapped(page) && page_rmapping(page)) { |
896 | if (!is_locked && (!PageAnon(page) || PageKsm(page))) { |
897 | we_locked = trylock_page(page); |
898 | if (!we_locked) { |
899 | referenced++; |
900 | goto out; |
901 | } |
902 | } |
903 | if (unlikely(PageKsm(page))) |
904 | referenced += page_referenced_ksm(page, memcg, |
905 | vm_flags); |
906 | else if (PageAnon(page)) |
907 | referenced += page_referenced_anon(page, memcg, |
908 | vm_flags); |
909 | else if (page->mapping) |
910 | referenced += page_referenced_file(page, memcg, |
911 | vm_flags); |
912 | if (we_locked) |
913 | unlock_page(page); |
914 | |
915 | if (page_test_and_clear_young(page_to_pfn(page))) |
916 | referenced++; |
917 | } |
918 | out: |
919 | return referenced; |
920 | } |
921 | |
922 | static int page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
923 | unsigned long address) |
924 | { |
925 | struct mm_struct *mm = vma->vm_mm; |
926 | pte_t *pte; |
927 | spinlock_t *ptl; |
928 | int ret = 0; |
929 | |
930 | pte = page_check_address(page, mm, address, &ptl, 1); |
931 | if (!pte) |
932 | goto out; |
933 | |
934 | if (pte_dirty(*pte) || pte_write(*pte)) { |
935 | pte_t entry; |
936 | |
937 | flush_cache_page(vma, address, pte_pfn(*pte)); |
938 | entry = ptep_clear_flush_notify(vma, address, pte); |
939 | entry = pte_wrprotect(entry); |
940 | entry = pte_mkclean(entry); |
941 | set_pte_at(mm, address, pte, entry); |
942 | ret = 1; |
943 | } |
944 | |
945 | pte_unmap_unlock(pte, ptl); |
946 | out: |
947 | return ret; |
948 | } |
949 | |
950 | static int page_mkclean_file(struct address_space *mapping, struct page *page) |
951 | { |
952 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
953 | struct vm_area_struct *vma; |
954 | struct prio_tree_iter iter; |
955 | int ret = 0; |
956 | |
957 | BUG_ON(PageAnon(page)); |
958 | |
959 | mutex_lock(&mapping->i_mmap_mutex); |
960 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
961 | if (vma->vm_flags & VM_SHARED) { |
962 | unsigned long address = vma_address(page, vma); |
963 | if (address == -EFAULT) |
964 | continue; |
965 | ret += page_mkclean_one(page, vma, address); |
966 | } |
967 | } |
968 | mutex_unlock(&mapping->i_mmap_mutex); |
969 | return ret; |
970 | } |
971 | |
972 | int page_mkclean(struct page *page) |
973 | { |
974 | int ret = 0; |
975 | |
976 | BUG_ON(!PageLocked(page)); |
977 | |
978 | if (page_mapped(page)) { |
979 | struct address_space *mapping = page_mapping(page); |
980 | if (mapping) { |
981 | ret = page_mkclean_file(mapping, page); |
982 | if (page_test_and_clear_dirty(page_to_pfn(page), 1)) |
983 | ret = 1; |
984 | } |
985 | } |
986 | |
987 | return ret; |
988 | } |
989 | EXPORT_SYMBOL_GPL(page_mkclean); |
990 | |
991 | /** |
992 | * page_move_anon_rmap - move a page to our anon_vma |
993 | * @page: the page to move to our anon_vma |
994 | * @vma: the vma the page belongs to |
995 | * @address: the user virtual address mapped |
996 | * |
997 | * When a page belongs exclusively to one process after a COW event, |
998 | * that page can be moved into the anon_vma that belongs to just that |
999 | * process, so the rmap code will not search the parent or sibling |
1000 | * processes. |
1001 | */ |
1002 | void page_move_anon_rmap(struct page *page, |
1003 | struct vm_area_struct *vma, unsigned long address) |
1004 | { |
1005 | struct anon_vma *anon_vma = vma->anon_vma; |
1006 | |
1007 | VM_BUG_ON(!PageLocked(page)); |
1008 | VM_BUG_ON(!anon_vma); |
1009 | VM_BUG_ON(page->index != linear_page_index(vma, address)); |
1010 | |
1011 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1012 | page->mapping = (struct address_space *) anon_vma; |
1013 | } |
1014 | |
1015 | /** |
1016 | * __page_set_anon_rmap - set up new anonymous rmap |
1017 | * @page: Page to add to rmap |
1018 | * @vma: VM area to add page to. |
1019 | * @address: User virtual address of the mapping |
1020 | * @exclusive: the page is exclusively owned by the current process |
1021 | */ |
1022 | static void __page_set_anon_rmap(struct page *page, |
1023 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
1024 | { |
1025 | struct anon_vma *anon_vma = vma->anon_vma; |
1026 | |
1027 | BUG_ON(!anon_vma); |
1028 | |
1029 | if (PageAnon(page)) |
1030 | return; |
1031 | |
1032 | /* |
1033 | * If the page isn't exclusively mapped into this vma, |
1034 | * we must use the _oldest_ possible anon_vma for the |
1035 | * page mapping! |
1036 | */ |
1037 | if (!exclusive) |
1038 | anon_vma = anon_vma->root; |
1039 | |
1040 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1041 | page->mapping = (struct address_space *) anon_vma; |
1042 | page->index = linear_page_index(vma, address); |
1043 | } |
1044 | |
1045 | /** |
1046 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
1047 | * @page: the page to add the mapping to |
1048 | * @vma: the vm area in which the mapping is added |
1049 | * @address: the user virtual address mapped |
1050 | */ |
1051 | static void __page_check_anon_rmap(struct page *page, |
1052 | struct vm_area_struct *vma, unsigned long address) |
1053 | { |
1054 | #ifdef CONFIG_DEBUG_VM |
1055 | /* |
1056 | * The page's anon-rmap details (mapping and index) are guaranteed to |
1057 | * be set up correctly at this point. |
1058 | * |
1059 | * We have exclusion against page_add_anon_rmap because the caller |
1060 | * always holds the page locked, except if called from page_dup_rmap, |
1061 | * in which case the page is already known to be setup. |
1062 | * |
1063 | * We have exclusion against page_add_new_anon_rmap because those pages |
1064 | * are initially only visible via the pagetables, and the pte is locked |
1065 | * over the call to page_add_new_anon_rmap. |
1066 | */ |
1067 | BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root); |
1068 | BUG_ON(page->index != linear_page_index(vma, address)); |
1069 | #endif |
1070 | } |
1071 | |
1072 | /** |
1073 | * page_add_anon_rmap - add pte mapping to an anonymous page |
1074 | * @page: the page to add the mapping to |
1075 | * @vma: the vm area in which the mapping is added |
1076 | * @address: the user virtual address mapped |
1077 | * |
1078 | * The caller needs to hold the pte lock, and the page must be locked in |
1079 | * the anon_vma case: to serialize mapping,index checking after setting, |
1080 | * and to ensure that PageAnon is not being upgraded racily to PageKsm |
1081 | * (but PageKsm is never downgraded to PageAnon). |
1082 | */ |
1083 | void page_add_anon_rmap(struct page *page, |
1084 | struct vm_area_struct *vma, unsigned long address) |
1085 | { |
1086 | do_page_add_anon_rmap(page, vma, address, 0); |
1087 | } |
1088 | |
1089 | /* |
1090 | * Special version of the above for do_swap_page, which often runs |
1091 | * into pages that are exclusively owned by the current process. |
1092 | * Everybody else should continue to use page_add_anon_rmap above. |
1093 | */ |
1094 | void do_page_add_anon_rmap(struct page *page, |
1095 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
1096 | { |
1097 | int first = atomic_inc_and_test(&page->_mapcount); |
1098 | if (first) { |
1099 | if (!PageTransHuge(page)) |
1100 | __inc_zone_page_state(page, NR_ANON_PAGES); |
1101 | else |
1102 | __inc_zone_page_state(page, |
1103 | NR_ANON_TRANSPARENT_HUGEPAGES); |
1104 | } |
1105 | if (unlikely(PageKsm(page))) |
1106 | return; |
1107 | |
1108 | VM_BUG_ON(!PageLocked(page)); |
1109 | /* address might be in next vma when migration races vma_adjust */ |
1110 | if (first) |
1111 | __page_set_anon_rmap(page, vma, address, exclusive); |
1112 | else |
1113 | __page_check_anon_rmap(page, vma, address); |
1114 | } |
1115 | |
1116 | /** |
1117 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
1118 | * @page: the page to add the mapping to |
1119 | * @vma: the vm area in which the mapping is added |
1120 | * @address: the user virtual address mapped |
1121 | * |
1122 | * Same as page_add_anon_rmap but must only be called on *new* pages. |
1123 | * This means the inc-and-test can be bypassed. |
1124 | * Page does not have to be locked. |
1125 | */ |
1126 | void page_add_new_anon_rmap(struct page *page, |
1127 | struct vm_area_struct *vma, unsigned long address) |
1128 | { |
1129 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
1130 | SetPageSwapBacked(page); |
1131 | atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */ |
1132 | if (!PageTransHuge(page)) |
1133 | __inc_zone_page_state(page, NR_ANON_PAGES); |
1134 | else |
1135 | __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); |
1136 | __page_set_anon_rmap(page, vma, address, 1); |
1137 | if (page_evictable(page, vma)) |
1138 | lru_cache_add_lru(page, LRU_ACTIVE_ANON); |
1139 | else |
1140 | add_page_to_unevictable_list(page); |
1141 | } |
1142 | |
1143 | /** |
1144 | * page_add_file_rmap - add pte mapping to a file page |
1145 | * @page: the page to add the mapping to |
1146 | * |
1147 | * The caller needs to hold the pte lock. |
1148 | */ |
1149 | void page_add_file_rmap(struct page *page) |
1150 | { |
1151 | bool locked; |
1152 | unsigned long flags; |
1153 | |
1154 | mem_cgroup_begin_update_page_stat(page, &locked, &flags); |
1155 | if (atomic_inc_and_test(&page->_mapcount)) { |
1156 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
1157 | mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED); |
1158 | } |
1159 | mem_cgroup_end_update_page_stat(page, &locked, &flags); |
1160 | } |
1161 | |
1162 | /** |
1163 | * page_remove_rmap - take down pte mapping from a page |
1164 | * @page: page to remove mapping from |
1165 | * |
1166 | * The caller needs to hold the pte lock. |
1167 | */ |
1168 | void page_remove_rmap(struct page *page) |
1169 | { |
1170 | bool anon = PageAnon(page); |
1171 | bool locked; |
1172 | unsigned long flags; |
1173 | |
1174 | /* |
1175 | * The anon case has no mem_cgroup page_stat to update; but may |
1176 | * uncharge_page() below, where the lock ordering can deadlock if |
1177 | * we hold the lock against page_stat move: so avoid it on anon. |
1178 | */ |
1179 | if (!anon) |
1180 | mem_cgroup_begin_update_page_stat(page, &locked, &flags); |
1181 | |
1182 | /* page still mapped by someone else? */ |
1183 | if (!atomic_add_negative(-1, &page->_mapcount)) |
1184 | goto out; |
1185 | |
1186 | /* |
1187 | * Now that the last pte has gone, s390 must transfer dirty |
1188 | * flag from storage key to struct page. We can usually skip |
1189 | * this if the page is anon, so about to be freed; but perhaps |
1190 | * not if it's in swapcache - there might be another pte slot |
1191 | * containing the swap entry, but page not yet written to swap. |
1192 | */ |
1193 | if ((!anon || PageSwapCache(page)) && |
1194 | page_test_and_clear_dirty(page_to_pfn(page), 1)) |
1195 | set_page_dirty(page); |
1196 | /* |
1197 | * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED |
1198 | * and not charged by memcg for now. |
1199 | */ |
1200 | if (unlikely(PageHuge(page))) |
1201 | goto out; |
1202 | if (anon) { |
1203 | mem_cgroup_uncharge_page(page); |
1204 | if (!PageTransHuge(page)) |
1205 | __dec_zone_page_state(page, NR_ANON_PAGES); |
1206 | else |
1207 | __dec_zone_page_state(page, |
1208 | NR_ANON_TRANSPARENT_HUGEPAGES); |
1209 | } else { |
1210 | __dec_zone_page_state(page, NR_FILE_MAPPED); |
1211 | mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED); |
1212 | } |
1213 | /* |
1214 | * It would be tidy to reset the PageAnon mapping here, |
1215 | * but that might overwrite a racing page_add_anon_rmap |
1216 | * which increments mapcount after us but sets mapping |
1217 | * before us: so leave the reset to free_hot_cold_page, |
1218 | * and remember that it's only reliable while mapped. |
1219 | * Leaving it set also helps swapoff to reinstate ptes |
1220 | * faster for those pages still in swapcache. |
1221 | */ |
1222 | out: |
1223 | if (!anon) |
1224 | mem_cgroup_end_update_page_stat(page, &locked, &flags); |
1225 | } |
1226 | |
1227 | /* |
1228 | * Subfunctions of try_to_unmap: try_to_unmap_one called |
1229 | * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file. |
1230 | */ |
1231 | int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
1232 | unsigned long address, enum ttu_flags flags) |
1233 | { |
1234 | struct mm_struct *mm = vma->vm_mm; |
1235 | pte_t *pte; |
1236 | pte_t pteval; |
1237 | spinlock_t *ptl; |
1238 | int ret = SWAP_AGAIN; |
1239 | |
1240 | pte = page_check_address(page, mm, address, &ptl, 0); |
1241 | if (!pte) |
1242 | goto out; |
1243 | |
1244 | /* |
1245 | * If the page is mlock()d, we cannot swap it out. |
1246 | * If it's recently referenced (perhaps page_referenced |
1247 | * skipped over this mm) then we should reactivate it. |
1248 | */ |
1249 | if (!(flags & TTU_IGNORE_MLOCK)) { |
1250 | if (vma->vm_flags & VM_LOCKED) |
1251 | goto out_mlock; |
1252 | |
1253 | if (TTU_ACTION(flags) == TTU_MUNLOCK) |
1254 | goto out_unmap; |
1255 | } |
1256 | if (!(flags & TTU_IGNORE_ACCESS)) { |
1257 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
1258 | ret = SWAP_FAIL; |
1259 | goto out_unmap; |
1260 | } |
1261 | } |
1262 | |
1263 | /* Nuke the page table entry. */ |
1264 | flush_cache_page(vma, address, page_to_pfn(page)); |
1265 | pteval = ptep_clear_flush_notify(vma, address, pte); |
1266 | |
1267 | /* Move the dirty bit to the physical page now the pte is gone. */ |
1268 | if (pte_dirty(pteval)) |
1269 | set_page_dirty(page); |
1270 | |
1271 | /* Update high watermark before we lower rss */ |
1272 | update_hiwater_rss(mm); |
1273 | |
1274 | if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
1275 | if (PageAnon(page)) |
1276 | dec_mm_counter(mm, MM_ANONPAGES); |
1277 | else |
1278 | dec_mm_counter(mm, MM_FILEPAGES); |
1279 | set_pte_at(mm, address, pte, |
1280 | swp_entry_to_pte(make_hwpoison_entry(page))); |
1281 | } else if (PageAnon(page)) { |
1282 | swp_entry_t entry = { .val = page_private(page) }; |
1283 | |
1284 | if (PageSwapCache(page)) { |
1285 | /* |
1286 | * Store the swap location in the pte. |
1287 | * See handle_pte_fault() ... |
1288 | */ |
1289 | if (swap_duplicate(entry) < 0) { |
1290 | set_pte_at(mm, address, pte, pteval); |
1291 | ret = SWAP_FAIL; |
1292 | goto out_unmap; |
1293 | } |
1294 | if (list_empty(&mm->mmlist)) { |
1295 | spin_lock(&mmlist_lock); |
1296 | if (list_empty(&mm->mmlist)) |
1297 | list_add(&mm->mmlist, &init_mm.mmlist); |
1298 | spin_unlock(&mmlist_lock); |
1299 | } |
1300 | dec_mm_counter(mm, MM_ANONPAGES); |
1301 | inc_mm_counter(mm, MM_SWAPENTS); |
1302 | } else if (IS_ENABLED(CONFIG_MIGRATION)) { |
1303 | /* |
1304 | * Store the pfn of the page in a special migration |
1305 | * pte. do_swap_page() will wait until the migration |
1306 | * pte is removed and then restart fault handling. |
1307 | */ |
1308 | BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION); |
1309 | entry = make_migration_entry(page, pte_write(pteval)); |
1310 | } |
1311 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
1312 | BUG_ON(pte_file(*pte)); |
1313 | } else if (IS_ENABLED(CONFIG_MIGRATION) && |
1314 | (TTU_ACTION(flags) == TTU_MIGRATION)) { |
1315 | /* Establish migration entry for a file page */ |
1316 | swp_entry_t entry; |
1317 | entry = make_migration_entry(page, pte_write(pteval)); |
1318 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
1319 | } else |
1320 | dec_mm_counter(mm, MM_FILEPAGES); |
1321 | |
1322 | page_remove_rmap(page); |
1323 | page_cache_release(page); |
1324 | |
1325 | out_unmap: |
1326 | pte_unmap_unlock(pte, ptl); |
1327 | out: |
1328 | return ret; |
1329 | |
1330 | out_mlock: |
1331 | pte_unmap_unlock(pte, ptl); |
1332 | |
1333 | |
1334 | /* |
1335 | * We need mmap_sem locking, Otherwise VM_LOCKED check makes |
1336 | * unstable result and race. Plus, We can't wait here because |
1337 | * we now hold anon_vma->mutex or mapping->i_mmap_mutex. |
1338 | * if trylock failed, the page remain in evictable lru and later |
1339 | * vmscan could retry to move the page to unevictable lru if the |
1340 | * page is actually mlocked. |
1341 | */ |
1342 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
1343 | if (vma->vm_flags & VM_LOCKED) { |
1344 | mlock_vma_page(page); |
1345 | ret = SWAP_MLOCK; |
1346 | } |
1347 | up_read(&vma->vm_mm->mmap_sem); |
1348 | } |
1349 | return ret; |
1350 | } |
1351 | |
1352 | /* |
1353 | * objrmap doesn't work for nonlinear VMAs because the assumption that |
1354 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. |
1355 | * Consequently, given a particular page and its ->index, we cannot locate the |
1356 | * ptes which are mapping that page without an exhaustive linear search. |
1357 | * |
1358 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which |
1359 | * maps the file to which the target page belongs. The ->vm_private_data field |
1360 | * holds the current cursor into that scan. Successive searches will circulate |
1361 | * around the vma's virtual address space. |
1362 | * |
1363 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, |
1364 | * more scanning pressure is placed against them as well. Eventually pages |
1365 | * will become fully unmapped and are eligible for eviction. |
1366 | * |
1367 | * For very sparsely populated VMAs this is a little inefficient - chances are |
1368 | * there there won't be many ptes located within the scan cluster. In this case |
1369 | * maybe we could scan further - to the end of the pte page, perhaps. |
1370 | * |
1371 | * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can |
1372 | * acquire it without blocking. If vma locked, mlock the pages in the cluster, |
1373 | * rather than unmapping them. If we encounter the "check_page" that vmscan is |
1374 | * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. |
1375 | */ |
1376 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) |
1377 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) |
1378 | |
1379 | static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, |
1380 | struct vm_area_struct *vma, struct page *check_page) |
1381 | { |
1382 | struct mm_struct *mm = vma->vm_mm; |
1383 | pgd_t *pgd; |
1384 | pud_t *pud; |
1385 | pmd_t *pmd; |
1386 | pte_t *pte; |
1387 | pte_t pteval; |
1388 | spinlock_t *ptl; |
1389 | struct page *page; |
1390 | unsigned long address; |
1391 | unsigned long end; |
1392 | int ret = SWAP_AGAIN; |
1393 | int locked_vma = 0; |
1394 | |
1395 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
1396 | end = address + CLUSTER_SIZE; |
1397 | if (address < vma->vm_start) |
1398 | address = vma->vm_start; |
1399 | if (end > vma->vm_end) |
1400 | end = vma->vm_end; |
1401 | |
1402 | pgd = pgd_offset(mm, address); |
1403 | if (!pgd_present(*pgd)) |
1404 | return ret; |
1405 | |
1406 | pud = pud_offset(pgd, address); |
1407 | if (!pud_present(*pud)) |
1408 | return ret; |
1409 | |
1410 | pmd = pmd_offset(pud, address); |
1411 | if (!pmd_present(*pmd)) |
1412 | return ret; |
1413 | |
1414 | /* |
1415 | * If we can acquire the mmap_sem for read, and vma is VM_LOCKED, |
1416 | * keep the sem while scanning the cluster for mlocking pages. |
1417 | */ |
1418 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
1419 | locked_vma = (vma->vm_flags & VM_LOCKED); |
1420 | if (!locked_vma) |
1421 | up_read(&vma->vm_mm->mmap_sem); /* don't need it */ |
1422 | } |
1423 | |
1424 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
1425 | |
1426 | /* Update high watermark before we lower rss */ |
1427 | update_hiwater_rss(mm); |
1428 | |
1429 | for (; address < end; pte++, address += PAGE_SIZE) { |
1430 | if (!pte_present(*pte)) |
1431 | continue; |
1432 | page = vm_normal_page(vma, address, *pte); |
1433 | BUG_ON(!page || PageAnon(page)); |
1434 | |
1435 | if (locked_vma) { |
1436 | mlock_vma_page(page); /* no-op if already mlocked */ |
1437 | if (page == check_page) |
1438 | ret = SWAP_MLOCK; |
1439 | continue; /* don't unmap */ |
1440 | } |
1441 | |
1442 | if (ptep_clear_flush_young_notify(vma, address, pte)) |
1443 | continue; |
1444 | |
1445 | /* Nuke the page table entry. */ |
1446 | flush_cache_page(vma, address, pte_pfn(*pte)); |
1447 | pteval = ptep_clear_flush_notify(vma, address, pte); |
1448 | |
1449 | /* If nonlinear, store the file page offset in the pte. */ |
1450 | if (page->index != linear_page_index(vma, address)) |
1451 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); |
1452 | |
1453 | /* Move the dirty bit to the physical page now the pte is gone. */ |
1454 | if (pte_dirty(pteval)) |
1455 | set_page_dirty(page); |
1456 | |
1457 | page_remove_rmap(page); |
1458 | page_cache_release(page); |
1459 | dec_mm_counter(mm, MM_FILEPAGES); |
1460 | (*mapcount)--; |
1461 | } |
1462 | pte_unmap_unlock(pte - 1, ptl); |
1463 | if (locked_vma) |
1464 | up_read(&vma->vm_mm->mmap_sem); |
1465 | return ret; |
1466 | } |
1467 | |
1468 | bool is_vma_temporary_stack(struct vm_area_struct *vma) |
1469 | { |
1470 | int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP); |
1471 | |
1472 | if (!maybe_stack) |
1473 | return false; |
1474 | |
1475 | if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) == |
1476 | VM_STACK_INCOMPLETE_SETUP) |
1477 | return true; |
1478 | |
1479 | return false; |
1480 | } |
1481 | |
1482 | /** |
1483 | * try_to_unmap_anon - unmap or unlock anonymous page using the object-based |
1484 | * rmap method |
1485 | * @page: the page to unmap/unlock |
1486 | * @flags: action and flags |
1487 | * |
1488 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1489 | * contained in the anon_vma struct it points to. |
1490 | * |
1491 | * This function is only called from try_to_unmap/try_to_munlock for |
1492 | * anonymous pages. |
1493 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1494 | * where the page was found will be held for write. So, we won't recheck |
1495 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1496 | * 'LOCKED. |
1497 | */ |
1498 | static int try_to_unmap_anon(struct page *page, enum ttu_flags flags) |
1499 | { |
1500 | struct anon_vma *anon_vma; |
1501 | struct anon_vma_chain *avc; |
1502 | int ret = SWAP_AGAIN; |
1503 | |
1504 | anon_vma = page_lock_anon_vma(page); |
1505 | if (!anon_vma) |
1506 | return ret; |
1507 | |
1508 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1509 | struct vm_area_struct *vma = avc->vma; |
1510 | unsigned long address; |
1511 | |
1512 | /* |
1513 | * During exec, a temporary VMA is setup and later moved. |
1514 | * The VMA is moved under the anon_vma lock but not the |
1515 | * page tables leading to a race where migration cannot |
1516 | * find the migration ptes. Rather than increasing the |
1517 | * locking requirements of exec(), migration skips |
1518 | * temporary VMAs until after exec() completes. |
1519 | */ |
1520 | if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) && |
1521 | is_vma_temporary_stack(vma)) |
1522 | continue; |
1523 | |
1524 | address = vma_address(page, vma); |
1525 | if (address == -EFAULT) |
1526 | continue; |
1527 | ret = try_to_unmap_one(page, vma, address, flags); |
1528 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1529 | break; |
1530 | } |
1531 | |
1532 | page_unlock_anon_vma(anon_vma); |
1533 | return ret; |
1534 | } |
1535 | |
1536 | /** |
1537 | * try_to_unmap_file - unmap/unlock file page using the object-based rmap method |
1538 | * @page: the page to unmap/unlock |
1539 | * @flags: action and flags |
1540 | * |
1541 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1542 | * contained in the address_space struct it points to. |
1543 | * |
1544 | * This function is only called from try_to_unmap/try_to_munlock for |
1545 | * object-based pages. |
1546 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1547 | * where the page was found will be held for write. So, we won't recheck |
1548 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1549 | * 'LOCKED. |
1550 | */ |
1551 | static int try_to_unmap_file(struct page *page, enum ttu_flags flags) |
1552 | { |
1553 | struct address_space *mapping = page->mapping; |
1554 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
1555 | struct vm_area_struct *vma; |
1556 | struct prio_tree_iter iter; |
1557 | int ret = SWAP_AGAIN; |
1558 | unsigned long cursor; |
1559 | unsigned long max_nl_cursor = 0; |
1560 | unsigned long max_nl_size = 0; |
1561 | unsigned int mapcount; |
1562 | |
1563 | mutex_lock(&mapping->i_mmap_mutex); |
1564 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1565 | unsigned long address = vma_address(page, vma); |
1566 | if (address == -EFAULT) |
1567 | continue; |
1568 | ret = try_to_unmap_one(page, vma, address, flags); |
1569 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1570 | goto out; |
1571 | } |
1572 | |
1573 | if (list_empty(&mapping->i_mmap_nonlinear)) |
1574 | goto out; |
1575 | |
1576 | /* |
1577 | * We don't bother to try to find the munlocked page in nonlinears. |
1578 | * It's costly. Instead, later, page reclaim logic may call |
1579 | * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily. |
1580 | */ |
1581 | if (TTU_ACTION(flags) == TTU_MUNLOCK) |
1582 | goto out; |
1583 | |
1584 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1585 | shared.vm_set.list) { |
1586 | cursor = (unsigned long) vma->vm_private_data; |
1587 | if (cursor > max_nl_cursor) |
1588 | max_nl_cursor = cursor; |
1589 | cursor = vma->vm_end - vma->vm_start; |
1590 | if (cursor > max_nl_size) |
1591 | max_nl_size = cursor; |
1592 | } |
1593 | |
1594 | if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ |
1595 | ret = SWAP_FAIL; |
1596 | goto out; |
1597 | } |
1598 | |
1599 | /* |
1600 | * We don't try to search for this page in the nonlinear vmas, |
1601 | * and page_referenced wouldn't have found it anyway. Instead |
1602 | * just walk the nonlinear vmas trying to age and unmap some. |
1603 | * The mapcount of the page we came in with is irrelevant, |
1604 | * but even so use it as a guide to how hard we should try? |
1605 | */ |
1606 | mapcount = page_mapcount(page); |
1607 | if (!mapcount) |
1608 | goto out; |
1609 | cond_resched(); |
1610 | |
1611 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; |
1612 | if (max_nl_cursor == 0) |
1613 | max_nl_cursor = CLUSTER_SIZE; |
1614 | |
1615 | do { |
1616 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1617 | shared.vm_set.list) { |
1618 | cursor = (unsigned long) vma->vm_private_data; |
1619 | while ( cursor < max_nl_cursor && |
1620 | cursor < vma->vm_end - vma->vm_start) { |
1621 | if (try_to_unmap_cluster(cursor, &mapcount, |
1622 | vma, page) == SWAP_MLOCK) |
1623 | ret = SWAP_MLOCK; |
1624 | cursor += CLUSTER_SIZE; |
1625 | vma->vm_private_data = (void *) cursor; |
1626 | if ((int)mapcount <= 0) |
1627 | goto out; |
1628 | } |
1629 | vma->vm_private_data = (void *) max_nl_cursor; |
1630 | } |
1631 | cond_resched(); |
1632 | max_nl_cursor += CLUSTER_SIZE; |
1633 | } while (max_nl_cursor <= max_nl_size); |
1634 | |
1635 | /* |
1636 | * Don't loop forever (perhaps all the remaining pages are |
1637 | * in locked vmas). Reset cursor on all unreserved nonlinear |
1638 | * vmas, now forgetting on which ones it had fallen behind. |
1639 | */ |
1640 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
1641 | vma->vm_private_data = NULL; |
1642 | out: |
1643 | mutex_unlock(&mapping->i_mmap_mutex); |
1644 | return ret; |
1645 | } |
1646 | |
1647 | /** |
1648 | * try_to_unmap - try to remove all page table mappings to a page |
1649 | * @page: the page to get unmapped |
1650 | * @flags: action and flags |
1651 | * |
1652 | * Tries to remove all the page table entries which are mapping this |
1653 | * page, used in the pageout path. Caller must hold the page lock. |
1654 | * Return values are: |
1655 | * |
1656 | * SWAP_SUCCESS - we succeeded in removing all mappings |
1657 | * SWAP_AGAIN - we missed a mapping, try again later |
1658 | * SWAP_FAIL - the page is unswappable |
1659 | * SWAP_MLOCK - page is mlocked. |
1660 | */ |
1661 | int try_to_unmap(struct page *page, enum ttu_flags flags) |
1662 | { |
1663 | int ret; |
1664 | |
1665 | BUG_ON(!PageLocked(page)); |
1666 | VM_BUG_ON(!PageHuge(page) && PageTransHuge(page)); |
1667 | |
1668 | if (unlikely(PageKsm(page))) |
1669 | ret = try_to_unmap_ksm(page, flags); |
1670 | else if (PageAnon(page)) |
1671 | ret = try_to_unmap_anon(page, flags); |
1672 | else |
1673 | ret = try_to_unmap_file(page, flags); |
1674 | if (ret != SWAP_MLOCK && !page_mapped(page)) |
1675 | ret = SWAP_SUCCESS; |
1676 | return ret; |
1677 | } |
1678 | |
1679 | /** |
1680 | * try_to_munlock - try to munlock a page |
1681 | * @page: the page to be munlocked |
1682 | * |
1683 | * Called from munlock code. Checks all of the VMAs mapping the page |
1684 | * to make sure nobody else has this page mlocked. The page will be |
1685 | * returned with PG_mlocked cleared if no other vmas have it mlocked. |
1686 | * |
1687 | * Return values are: |
1688 | * |
1689 | * SWAP_AGAIN - no vma is holding page mlocked, or, |
1690 | * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem |
1691 | * SWAP_FAIL - page cannot be located at present |
1692 | * SWAP_MLOCK - page is now mlocked. |
1693 | */ |
1694 | int try_to_munlock(struct page *page) |
1695 | { |
1696 | VM_BUG_ON(!PageLocked(page) || PageLRU(page)); |
1697 | |
1698 | if (unlikely(PageKsm(page))) |
1699 | return try_to_unmap_ksm(page, TTU_MUNLOCK); |
1700 | else if (PageAnon(page)) |
1701 | return try_to_unmap_anon(page, TTU_MUNLOCK); |
1702 | else |
1703 | return try_to_unmap_file(page, TTU_MUNLOCK); |
1704 | } |
1705 | |
1706 | void __put_anon_vma(struct anon_vma *anon_vma) |
1707 | { |
1708 | struct anon_vma *root = anon_vma->root; |
1709 | |
1710 | if (root != anon_vma && atomic_dec_and_test(&root->refcount)) |
1711 | anon_vma_free(root); |
1712 | |
1713 | anon_vma_free(anon_vma); |
1714 | } |
1715 | |
1716 | #ifdef CONFIG_MIGRATION |
1717 | /* |
1718 | * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file(): |
1719 | * Called by migrate.c to remove migration ptes, but might be used more later. |
1720 | */ |
1721 | static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, |
1722 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1723 | { |
1724 | struct anon_vma *anon_vma; |
1725 | struct anon_vma_chain *avc; |
1726 | int ret = SWAP_AGAIN; |
1727 | |
1728 | /* |
1729 | * Note: remove_migration_ptes() cannot use page_lock_anon_vma() |
1730 | * because that depends on page_mapped(); but not all its usages |
1731 | * are holding mmap_sem. Users without mmap_sem are required to |
1732 | * take a reference count to prevent the anon_vma disappearing |
1733 | */ |
1734 | anon_vma = page_anon_vma(page); |
1735 | if (!anon_vma) |
1736 | return ret; |
1737 | anon_vma_lock(anon_vma); |
1738 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1739 | struct vm_area_struct *vma = avc->vma; |
1740 | unsigned long address = vma_address(page, vma); |
1741 | if (address == -EFAULT) |
1742 | continue; |
1743 | ret = rmap_one(page, vma, address, arg); |
1744 | if (ret != SWAP_AGAIN) |
1745 | break; |
1746 | } |
1747 | anon_vma_unlock(anon_vma); |
1748 | return ret; |
1749 | } |
1750 | |
1751 | static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *, |
1752 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1753 | { |
1754 | struct address_space *mapping = page->mapping; |
1755 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
1756 | struct vm_area_struct *vma; |
1757 | struct prio_tree_iter iter; |
1758 | int ret = SWAP_AGAIN; |
1759 | |
1760 | if (!mapping) |
1761 | return ret; |
1762 | mutex_lock(&mapping->i_mmap_mutex); |
1763 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1764 | unsigned long address = vma_address(page, vma); |
1765 | if (address == -EFAULT) |
1766 | continue; |
1767 | ret = rmap_one(page, vma, address, arg); |
1768 | if (ret != SWAP_AGAIN) |
1769 | break; |
1770 | } |
1771 | /* |
1772 | * No nonlinear handling: being always shared, nonlinear vmas |
1773 | * never contain migration ptes. Decide what to do about this |
1774 | * limitation to linear when we need rmap_walk() on nonlinear. |
1775 | */ |
1776 | mutex_unlock(&mapping->i_mmap_mutex); |
1777 | return ret; |
1778 | } |
1779 | |
1780 | int rmap_walk(struct page *page, int (*rmap_one)(struct page *, |
1781 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1782 | { |
1783 | VM_BUG_ON(!PageLocked(page)); |
1784 | |
1785 | if (unlikely(PageKsm(page))) |
1786 | return rmap_walk_ksm(page, rmap_one, arg); |
1787 | else if (PageAnon(page)) |
1788 | return rmap_walk_anon(page, rmap_one, arg); |
1789 | else |
1790 | return rmap_walk_file(page, rmap_one, arg); |
1791 | } |
1792 | #endif /* CONFIG_MIGRATION */ |
1793 | |
1794 | #ifdef CONFIG_HUGETLB_PAGE |
1795 | /* |
1796 | * The following three functions are for anonymous (private mapped) hugepages. |
1797 | * Unlike common anonymous pages, anonymous hugepages have no accounting code |
1798 | * and no lru code, because we handle hugepages differently from common pages. |
1799 | */ |
1800 | static void __hugepage_set_anon_rmap(struct page *page, |
1801 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
1802 | { |
1803 | struct anon_vma *anon_vma = vma->anon_vma; |
1804 | |
1805 | BUG_ON(!anon_vma); |
1806 | |
1807 | if (PageAnon(page)) |
1808 | return; |
1809 | if (!exclusive) |
1810 | anon_vma = anon_vma->root; |
1811 | |
1812 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1813 | page->mapping = (struct address_space *) anon_vma; |
1814 | page->index = linear_page_index(vma, address); |
1815 | } |
1816 | |
1817 | void hugepage_add_anon_rmap(struct page *page, |
1818 | struct vm_area_struct *vma, unsigned long address) |
1819 | { |
1820 | struct anon_vma *anon_vma = vma->anon_vma; |
1821 | int first; |
1822 | |
1823 | BUG_ON(!PageLocked(page)); |
1824 | BUG_ON(!anon_vma); |
1825 | /* address might be in next vma when migration races vma_adjust */ |
1826 | first = atomic_inc_and_test(&page->_mapcount); |
1827 | if (first) |
1828 | __hugepage_set_anon_rmap(page, vma, address, 0); |
1829 | } |
1830 | |
1831 | void hugepage_add_new_anon_rmap(struct page *page, |
1832 | struct vm_area_struct *vma, unsigned long address) |
1833 | { |
1834 | BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
1835 | atomic_set(&page->_mapcount, 0); |
1836 | __hugepage_set_anon_rmap(page, vma, address, 1); |
1837 | } |
1838 | #endif /* CONFIG_HUGETLB_PAGE */ |
1839 |
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