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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 | * inode->i_alloc_sem (vmtruncate_range) |
25 | * mm->mmap_sem |
26 | * page->flags PG_locked (lock_page) |
27 | * mapping->i_mmap_lock |
28 | * anon_vma->lock |
29 | * mm->page_table_lock or pte_lock |
30 | * zone->lru_lock (in mark_page_accessed, isolate_lru_page) |
31 | * swap_lock (in swap_duplicate, swap_info_get) |
32 | * mmlist_lock (in mmput, drain_mmlist and others) |
33 | * mapping->private_lock (in __set_page_dirty_buffers) |
34 | * inode_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 inode_lock in __sync_single_inode) |
39 | * |
40 | * (code doesn't rely on that order so it could be switched around) |
41 | * ->tasklist_lock |
42 | * anon_vma->lock (memory_failure, collect_procs_anon) |
43 | * pte map lock |
44 | */ |
45 | |
46 | #include <linux/mm.h> |
47 | #include <linux/pagemap.h> |
48 | #include <linux/swap.h> |
49 | #include <linux/swapops.h> |
50 | #include <linux/slab.h> |
51 | #include <linux/init.h> |
52 | #include <linux/ksm.h> |
53 | #include <linux/rmap.h> |
54 | #include <linux/rcupdate.h> |
55 | #include <linux/module.h> |
56 | #include <linux/memcontrol.h> |
57 | #include <linux/mmu_notifier.h> |
58 | #include <linux/migrate.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 | return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
70 | } |
71 | |
72 | void anon_vma_free(struct anon_vma *anon_vma) |
73 | { |
74 | kmem_cache_free(anon_vma_cachep, anon_vma); |
75 | } |
76 | |
77 | static inline struct anon_vma_chain *anon_vma_chain_alloc(void) |
78 | { |
79 | return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL); |
80 | } |
81 | |
82 | void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
83 | { |
84 | kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); |
85 | } |
86 | |
87 | /** |
88 | * anon_vma_prepare - attach an anon_vma to a memory region |
89 | * @vma: the memory region in question |
90 | * |
91 | * This makes sure the memory mapping described by 'vma' has |
92 | * an 'anon_vma' attached to it, so that we can associate the |
93 | * anonymous pages mapped into it with that anon_vma. |
94 | * |
95 | * The common case will be that we already have one, but if |
96 | * if not we either need to find an adjacent mapping that we |
97 | * can re-use the anon_vma from (very common when the only |
98 | * reason for splitting a vma has been mprotect()), or we |
99 | * allocate a new one. |
100 | * |
101 | * Anon-vma allocations are very subtle, because we may have |
102 | * optimistically looked up an anon_vma in page_lock_anon_vma() |
103 | * and that may actually touch the spinlock even in the newly |
104 | * allocated vma (it depends on RCU to make sure that the |
105 | * anon_vma isn't actually destroyed). |
106 | * |
107 | * As a result, we need to do proper anon_vma locking even |
108 | * for the new allocation. At the same time, we do not want |
109 | * to do any locking for the common case of already having |
110 | * an anon_vma. |
111 | * |
112 | * This must be called with the mmap_sem held for reading. |
113 | */ |
114 | int anon_vma_prepare(struct vm_area_struct *vma) |
115 | { |
116 | struct anon_vma *anon_vma = vma->anon_vma; |
117 | struct anon_vma_chain *avc; |
118 | |
119 | might_sleep(); |
120 | if (unlikely(!anon_vma)) { |
121 | struct mm_struct *mm = vma->vm_mm; |
122 | struct anon_vma *allocated; |
123 | |
124 | avc = anon_vma_chain_alloc(); |
125 | if (!avc) |
126 | goto out_enomem; |
127 | |
128 | anon_vma = find_mergeable_anon_vma(vma); |
129 | allocated = NULL; |
130 | if (!anon_vma) { |
131 | anon_vma = anon_vma_alloc(); |
132 | if (unlikely(!anon_vma)) |
133 | goto out_enomem_free_avc; |
134 | allocated = anon_vma; |
135 | } |
136 | |
137 | spin_lock(&anon_vma->lock); |
138 | /* page_table_lock to protect against threads */ |
139 | spin_lock(&mm->page_table_lock); |
140 | if (likely(!vma->anon_vma)) { |
141 | vma->anon_vma = anon_vma; |
142 | avc->anon_vma = anon_vma; |
143 | avc->vma = vma; |
144 | list_add(&avc->same_vma, &vma->anon_vma_chain); |
145 | list_add(&avc->same_anon_vma, &anon_vma->head); |
146 | allocated = NULL; |
147 | avc = NULL; |
148 | } |
149 | spin_unlock(&mm->page_table_lock); |
150 | spin_unlock(&anon_vma->lock); |
151 | |
152 | if (unlikely(allocated)) |
153 | anon_vma_free(allocated); |
154 | if (unlikely(avc)) |
155 | anon_vma_chain_free(avc); |
156 | } |
157 | return 0; |
158 | |
159 | out_enomem_free_avc: |
160 | anon_vma_chain_free(avc); |
161 | out_enomem: |
162 | return -ENOMEM; |
163 | } |
164 | |
165 | static void anon_vma_chain_link(struct vm_area_struct *vma, |
166 | struct anon_vma_chain *avc, |
167 | struct anon_vma *anon_vma) |
168 | { |
169 | avc->vma = vma; |
170 | avc->anon_vma = anon_vma; |
171 | list_add(&avc->same_vma, &vma->anon_vma_chain); |
172 | |
173 | spin_lock(&anon_vma->lock); |
174 | list_add_tail(&avc->same_anon_vma, &anon_vma->head); |
175 | spin_unlock(&anon_vma->lock); |
176 | } |
177 | |
178 | /* |
179 | * Attach the anon_vmas from src to dst. |
180 | * Returns 0 on success, -ENOMEM on failure. |
181 | */ |
182 | int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
183 | { |
184 | struct anon_vma_chain *avc, *pavc; |
185 | |
186 | list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
187 | avc = anon_vma_chain_alloc(); |
188 | if (!avc) |
189 | goto enomem_failure; |
190 | anon_vma_chain_link(dst, avc, pavc->anon_vma); |
191 | } |
192 | return 0; |
193 | |
194 | enomem_failure: |
195 | unlink_anon_vmas(dst); |
196 | return -ENOMEM; |
197 | } |
198 | |
199 | /* |
200 | * Attach vma to its own anon_vma, as well as to the anon_vmas that |
201 | * the corresponding VMA in the parent process is attached to. |
202 | * Returns 0 on success, non-zero on failure. |
203 | */ |
204 | int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
205 | { |
206 | struct anon_vma_chain *avc; |
207 | struct anon_vma *anon_vma; |
208 | |
209 | /* Don't bother if the parent process has no anon_vma here. */ |
210 | if (!pvma->anon_vma) |
211 | return 0; |
212 | |
213 | /* |
214 | * First, attach the new VMA to the parent VMA's anon_vmas, |
215 | * so rmap can find non-COWed pages in child processes. |
216 | */ |
217 | if (anon_vma_clone(vma, pvma)) |
218 | return -ENOMEM; |
219 | |
220 | /* Then add our own anon_vma. */ |
221 | anon_vma = anon_vma_alloc(); |
222 | if (!anon_vma) |
223 | goto out_error; |
224 | avc = anon_vma_chain_alloc(); |
225 | if (!avc) |
226 | goto out_error_free_anon_vma; |
227 | anon_vma_chain_link(vma, avc, anon_vma); |
228 | /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
229 | vma->anon_vma = anon_vma; |
230 | |
231 | return 0; |
232 | |
233 | out_error_free_anon_vma: |
234 | anon_vma_free(anon_vma); |
235 | out_error: |
236 | unlink_anon_vmas(vma); |
237 | return -ENOMEM; |
238 | } |
239 | |
240 | static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain) |
241 | { |
242 | struct anon_vma *anon_vma = anon_vma_chain->anon_vma; |
243 | int empty; |
244 | |
245 | /* If anon_vma_fork fails, we can get an empty anon_vma_chain. */ |
246 | if (!anon_vma) |
247 | return; |
248 | |
249 | spin_lock(&anon_vma->lock); |
250 | list_del(&anon_vma_chain->same_anon_vma); |
251 | |
252 | /* We must garbage collect the anon_vma if it's empty */ |
253 | empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma); |
254 | spin_unlock(&anon_vma->lock); |
255 | |
256 | if (empty) |
257 | anon_vma_free(anon_vma); |
258 | } |
259 | |
260 | void unlink_anon_vmas(struct vm_area_struct *vma) |
261 | { |
262 | struct anon_vma_chain *avc, *next; |
263 | |
264 | /* Unlink each anon_vma chained to the VMA. */ |
265 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
266 | anon_vma_unlink(avc); |
267 | list_del(&avc->same_vma); |
268 | anon_vma_chain_free(avc); |
269 | } |
270 | } |
271 | |
272 | static void anon_vma_ctor(void *data) |
273 | { |
274 | struct anon_vma *anon_vma = data; |
275 | |
276 | spin_lock_init(&anon_vma->lock); |
277 | ksm_refcount_init(anon_vma); |
278 | INIT_LIST_HEAD(&anon_vma->head); |
279 | } |
280 | |
281 | void __init anon_vma_init(void) |
282 | { |
283 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), |
284 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor); |
285 | anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC); |
286 | } |
287 | |
288 | /* |
289 | * Getting a lock on a stable anon_vma from a page off the LRU is |
290 | * tricky: page_lock_anon_vma rely on RCU to guard against the races. |
291 | */ |
292 | struct anon_vma *page_lock_anon_vma(struct page *page) |
293 | { |
294 | struct anon_vma *anon_vma; |
295 | unsigned long anon_mapping; |
296 | |
297 | rcu_read_lock(); |
298 | anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping); |
299 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
300 | goto out; |
301 | if (!page_mapped(page)) |
302 | goto out; |
303 | |
304 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
305 | spin_lock(&anon_vma->lock); |
306 | return anon_vma; |
307 | out: |
308 | rcu_read_unlock(); |
309 | return NULL; |
310 | } |
311 | |
312 | void page_unlock_anon_vma(struct anon_vma *anon_vma) |
313 | { |
314 | spin_unlock(&anon_vma->lock); |
315 | rcu_read_unlock(); |
316 | } |
317 | |
318 | /* |
319 | * At what user virtual address is page expected in @vma? |
320 | * Returns virtual address or -EFAULT if page's index/offset is not |
321 | * within the range mapped the @vma. |
322 | */ |
323 | static inline unsigned long |
324 | vma_address(struct page *page, struct vm_area_struct *vma) |
325 | { |
326 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
327 | unsigned long address; |
328 | |
329 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
330 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { |
331 | /* page should be within @vma mapping range */ |
332 | return -EFAULT; |
333 | } |
334 | return address; |
335 | } |
336 | |
337 | /* |
338 | * At what user virtual address is page expected in vma? |
339 | * checking that the page matches the vma. |
340 | */ |
341 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
342 | { |
343 | if (PageAnon(page)) { |
344 | if (vma->anon_vma != page_anon_vma(page)) |
345 | return -EFAULT; |
346 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { |
347 | if (!vma->vm_file || |
348 | vma->vm_file->f_mapping != page->mapping) |
349 | return -EFAULT; |
350 | } else |
351 | return -EFAULT; |
352 | return vma_address(page, vma); |
353 | } |
354 | |
355 | /* |
356 | * Check that @page is mapped at @address into @mm. |
357 | * |
358 | * If @sync is false, page_check_address may perform a racy check to avoid |
359 | * the page table lock when the pte is not present (helpful when reclaiming |
360 | * highly shared pages). |
361 | * |
362 | * On success returns with pte mapped and locked. |
363 | */ |
364 | pte_t *page_check_address(struct page *page, struct mm_struct *mm, |
365 | unsigned long address, spinlock_t **ptlp, int sync) |
366 | { |
367 | pgd_t *pgd; |
368 | pud_t *pud; |
369 | pmd_t *pmd; |
370 | pte_t *pte; |
371 | spinlock_t *ptl; |
372 | |
373 | pgd = pgd_offset(mm, address); |
374 | if (!pgd_present(*pgd)) |
375 | return NULL; |
376 | |
377 | pud = pud_offset(pgd, address); |
378 | if (!pud_present(*pud)) |
379 | return NULL; |
380 | |
381 | pmd = pmd_offset(pud, address); |
382 | if (!pmd_present(*pmd)) |
383 | return NULL; |
384 | |
385 | pte = pte_offset_map(pmd, address); |
386 | /* Make a quick check before getting the lock */ |
387 | if (!sync && !pte_present(*pte)) { |
388 | pte_unmap(pte); |
389 | return NULL; |
390 | } |
391 | |
392 | ptl = pte_lockptr(mm, pmd); |
393 | spin_lock(ptl); |
394 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { |
395 | *ptlp = ptl; |
396 | return pte; |
397 | } |
398 | pte_unmap_unlock(pte, ptl); |
399 | return NULL; |
400 | } |
401 | |
402 | /** |
403 | * page_mapped_in_vma - check whether a page is really mapped in a VMA |
404 | * @page: the page to test |
405 | * @vma: the VMA to test |
406 | * |
407 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 |
408 | * if the page is not mapped into the page tables of this VMA. Only |
409 | * valid for normal file or anonymous VMAs. |
410 | */ |
411 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) |
412 | { |
413 | unsigned long address; |
414 | pte_t *pte; |
415 | spinlock_t *ptl; |
416 | |
417 | address = vma_address(page, vma); |
418 | if (address == -EFAULT) /* out of vma range */ |
419 | return 0; |
420 | pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); |
421 | if (!pte) /* the page is not in this mm */ |
422 | return 0; |
423 | pte_unmap_unlock(pte, ptl); |
424 | |
425 | return 1; |
426 | } |
427 | |
428 | /* |
429 | * Subfunctions of page_referenced: page_referenced_one called |
430 | * repeatedly from either page_referenced_anon or page_referenced_file. |
431 | */ |
432 | int page_referenced_one(struct page *page, struct vm_area_struct *vma, |
433 | unsigned long address, unsigned int *mapcount, |
434 | unsigned long *vm_flags) |
435 | { |
436 | struct mm_struct *mm = vma->vm_mm; |
437 | pte_t *pte; |
438 | spinlock_t *ptl; |
439 | int referenced = 0; |
440 | |
441 | pte = page_check_address(page, mm, address, &ptl, 0); |
442 | if (!pte) |
443 | goto out; |
444 | |
445 | /* |
446 | * Don't want to elevate referenced for mlocked page that gets this far, |
447 | * in order that it progresses to try_to_unmap and is moved to the |
448 | * unevictable list. |
449 | */ |
450 | if (vma->vm_flags & VM_LOCKED) { |
451 | *mapcount = 1; /* break early from loop */ |
452 | *vm_flags |= VM_LOCKED; |
453 | goto out_unmap; |
454 | } |
455 | |
456 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
457 | /* |
458 | * Don't treat a reference through a sequentially read |
459 | * mapping as such. If the page has been used in |
460 | * another mapping, we will catch it; if this other |
461 | * mapping is already gone, the unmap path will have |
462 | * set PG_referenced or activated the page. |
463 | */ |
464 | if (likely(!VM_SequentialReadHint(vma))) |
465 | referenced++; |
466 | } |
467 | |
468 | /* Pretend the page is referenced if the task has the |
469 | swap token and is in the middle of a page fault. */ |
470 | if (mm != current->mm && has_swap_token(mm) && |
471 | rwsem_is_locked(&mm->mmap_sem)) |
472 | referenced++; |
473 | |
474 | out_unmap: |
475 | (*mapcount)--; |
476 | pte_unmap_unlock(pte, ptl); |
477 | |
478 | if (referenced) |
479 | *vm_flags |= vma->vm_flags; |
480 | out: |
481 | return referenced; |
482 | } |
483 | |
484 | static int page_referenced_anon(struct page *page, |
485 | struct mem_cgroup *mem_cont, |
486 | unsigned long *vm_flags) |
487 | { |
488 | unsigned int mapcount; |
489 | struct anon_vma *anon_vma; |
490 | struct anon_vma_chain *avc; |
491 | int referenced = 0; |
492 | |
493 | anon_vma = page_lock_anon_vma(page); |
494 | if (!anon_vma) |
495 | return referenced; |
496 | |
497 | mapcount = page_mapcount(page); |
498 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
499 | struct vm_area_struct *vma = avc->vma; |
500 | unsigned long address = vma_address(page, vma); |
501 | if (address == -EFAULT) |
502 | continue; |
503 | /* |
504 | * If we are reclaiming on behalf of a cgroup, skip |
505 | * counting on behalf of references from different |
506 | * cgroups |
507 | */ |
508 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
509 | continue; |
510 | referenced += page_referenced_one(page, vma, address, |
511 | &mapcount, vm_flags); |
512 | if (!mapcount) |
513 | break; |
514 | } |
515 | |
516 | page_unlock_anon_vma(anon_vma); |
517 | return referenced; |
518 | } |
519 | |
520 | /** |
521 | * page_referenced_file - referenced check for object-based rmap |
522 | * @page: the page we're checking references on. |
523 | * @mem_cont: target memory controller |
524 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
525 | * |
526 | * For an object-based mapped page, find all the places it is mapped and |
527 | * check/clear the referenced flag. This is done by following the page->mapping |
528 | * pointer, then walking the chain of vmas it holds. It returns the number |
529 | * of references it found. |
530 | * |
531 | * This function is only called from page_referenced for object-based pages. |
532 | */ |
533 | static int page_referenced_file(struct page *page, |
534 | struct mem_cgroup *mem_cont, |
535 | unsigned long *vm_flags) |
536 | { |
537 | unsigned int mapcount; |
538 | struct address_space *mapping = page->mapping; |
539 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
540 | struct vm_area_struct *vma; |
541 | struct prio_tree_iter iter; |
542 | int referenced = 0; |
543 | |
544 | /* |
545 | * The caller's checks on page->mapping and !PageAnon have made |
546 | * sure that this is a file page: the check for page->mapping |
547 | * excludes the case just before it gets set on an anon page. |
548 | */ |
549 | BUG_ON(PageAnon(page)); |
550 | |
551 | /* |
552 | * The page lock not only makes sure that page->mapping cannot |
553 | * suddenly be NULLified by truncation, it makes sure that the |
554 | * structure at mapping cannot be freed and reused yet, |
555 | * so we can safely take mapping->i_mmap_lock. |
556 | */ |
557 | BUG_ON(!PageLocked(page)); |
558 | |
559 | spin_lock(&mapping->i_mmap_lock); |
560 | |
561 | /* |
562 | * i_mmap_lock does not stabilize mapcount at all, but mapcount |
563 | * is more likely to be accurate if we note it after spinning. |
564 | */ |
565 | mapcount = page_mapcount(page); |
566 | |
567 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
568 | unsigned long address = vma_address(page, vma); |
569 | if (address == -EFAULT) |
570 | continue; |
571 | /* |
572 | * If we are reclaiming on behalf of a cgroup, skip |
573 | * counting on behalf of references from different |
574 | * cgroups |
575 | */ |
576 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
577 | continue; |
578 | referenced += page_referenced_one(page, vma, address, |
579 | &mapcount, vm_flags); |
580 | if (!mapcount) |
581 | break; |
582 | } |
583 | |
584 | spin_unlock(&mapping->i_mmap_lock); |
585 | return referenced; |
586 | } |
587 | |
588 | /** |
589 | * page_referenced - test if the page was referenced |
590 | * @page: the page to test |
591 | * @is_locked: caller holds lock on the page |
592 | * @mem_cont: target memory controller |
593 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
594 | * |
595 | * Quick test_and_clear_referenced for all mappings to a page, |
596 | * returns the number of ptes which referenced the page. |
597 | */ |
598 | int page_referenced(struct page *page, |
599 | int is_locked, |
600 | struct mem_cgroup *mem_cont, |
601 | unsigned long *vm_flags) |
602 | { |
603 | int referenced = 0; |
604 | int we_locked = 0; |
605 | |
606 | *vm_flags = 0; |
607 | if (page_mapped(page) && page_rmapping(page)) { |
608 | if (!is_locked && (!PageAnon(page) || PageKsm(page))) { |
609 | we_locked = trylock_page(page); |
610 | if (!we_locked) { |
611 | referenced++; |
612 | goto out; |
613 | } |
614 | } |
615 | if (unlikely(PageKsm(page))) |
616 | referenced += page_referenced_ksm(page, mem_cont, |
617 | vm_flags); |
618 | else if (PageAnon(page)) |
619 | referenced += page_referenced_anon(page, mem_cont, |
620 | vm_flags); |
621 | else if (page->mapping) |
622 | referenced += page_referenced_file(page, mem_cont, |
623 | vm_flags); |
624 | if (we_locked) |
625 | unlock_page(page); |
626 | } |
627 | out: |
628 | if (page_test_and_clear_young(page)) |
629 | referenced++; |
630 | |
631 | return referenced; |
632 | } |
633 | |
634 | static int page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
635 | unsigned long address) |
636 | { |
637 | struct mm_struct *mm = vma->vm_mm; |
638 | pte_t *pte; |
639 | spinlock_t *ptl; |
640 | int ret = 0; |
641 | |
642 | pte = page_check_address(page, mm, address, &ptl, 1); |
643 | if (!pte) |
644 | goto out; |
645 | |
646 | if (pte_dirty(*pte) || pte_write(*pte)) { |
647 | pte_t entry; |
648 | |
649 | flush_cache_page(vma, address, pte_pfn(*pte)); |
650 | entry = ptep_clear_flush_notify(vma, address, pte); |
651 | entry = pte_wrprotect(entry); |
652 | entry = pte_mkclean(entry); |
653 | set_pte_at(mm, address, pte, entry); |
654 | ret = 1; |
655 | } |
656 | |
657 | pte_unmap_unlock(pte, ptl); |
658 | out: |
659 | return ret; |
660 | } |
661 | |
662 | static int page_mkclean_file(struct address_space *mapping, struct page *page) |
663 | { |
664 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
665 | struct vm_area_struct *vma; |
666 | struct prio_tree_iter iter; |
667 | int ret = 0; |
668 | |
669 | BUG_ON(PageAnon(page)); |
670 | |
671 | spin_lock(&mapping->i_mmap_lock); |
672 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
673 | if (vma->vm_flags & VM_SHARED) { |
674 | unsigned long address = vma_address(page, vma); |
675 | if (address == -EFAULT) |
676 | continue; |
677 | ret += page_mkclean_one(page, vma, address); |
678 | } |
679 | } |
680 | spin_unlock(&mapping->i_mmap_lock); |
681 | return ret; |
682 | } |
683 | |
684 | int page_mkclean(struct page *page) |
685 | { |
686 | int ret = 0; |
687 | |
688 | BUG_ON(!PageLocked(page)); |
689 | |
690 | if (page_mapped(page)) { |
691 | struct address_space *mapping = page_mapping(page); |
692 | if (mapping) { |
693 | ret = page_mkclean_file(mapping, page); |
694 | if (page_test_dirty(page)) { |
695 | page_clear_dirty(page); |
696 | ret = 1; |
697 | } |
698 | } |
699 | } |
700 | |
701 | return ret; |
702 | } |
703 | EXPORT_SYMBOL_GPL(page_mkclean); |
704 | |
705 | /** |
706 | * page_move_anon_rmap - move a page to our anon_vma |
707 | * @page: the page to move to our anon_vma |
708 | * @vma: the vma the page belongs to |
709 | * @address: the user virtual address mapped |
710 | * |
711 | * When a page belongs exclusively to one process after a COW event, |
712 | * that page can be moved into the anon_vma that belongs to just that |
713 | * process, so the rmap code will not search the parent or sibling |
714 | * processes. |
715 | */ |
716 | void page_move_anon_rmap(struct page *page, |
717 | struct vm_area_struct *vma, unsigned long address) |
718 | { |
719 | struct anon_vma *anon_vma = vma->anon_vma; |
720 | |
721 | VM_BUG_ON(!PageLocked(page)); |
722 | VM_BUG_ON(!anon_vma); |
723 | VM_BUG_ON(page->index != linear_page_index(vma, address)); |
724 | |
725 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
726 | page->mapping = (struct address_space *) anon_vma; |
727 | } |
728 | |
729 | /** |
730 | * __page_set_anon_rmap - setup new anonymous rmap |
731 | * @page: the page to add the mapping to |
732 | * @vma: the vm area in which the mapping is added |
733 | * @address: the user virtual address mapped |
734 | * @exclusive: the page is exclusively owned by the current process |
735 | */ |
736 | static void __page_set_anon_rmap(struct page *page, |
737 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
738 | { |
739 | struct anon_vma *anon_vma = vma->anon_vma; |
740 | |
741 | BUG_ON(!anon_vma); |
742 | |
743 | /* |
744 | * If the page isn't exclusively mapped into this vma, |
745 | * we must use the _oldest_ possible anon_vma for the |
746 | * page mapping! |
747 | * |
748 | * So take the last AVC chain entry in the vma, which is |
749 | * the deepest ancestor, and use the anon_vma from that. |
750 | */ |
751 | if (!exclusive) { |
752 | struct anon_vma_chain *avc; |
753 | avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma); |
754 | anon_vma = avc->anon_vma; |
755 | } |
756 | |
757 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
758 | page->mapping = (struct address_space *) anon_vma; |
759 | page->index = linear_page_index(vma, address); |
760 | } |
761 | |
762 | /** |
763 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
764 | * @page: the page to add the mapping to |
765 | * @vma: the vm area in which the mapping is added |
766 | * @address: the user virtual address mapped |
767 | */ |
768 | static void __page_check_anon_rmap(struct page *page, |
769 | struct vm_area_struct *vma, unsigned long address) |
770 | { |
771 | #ifdef CONFIG_DEBUG_VM |
772 | /* |
773 | * The page's anon-rmap details (mapping and index) are guaranteed to |
774 | * be set up correctly at this point. |
775 | * |
776 | * We have exclusion against page_add_anon_rmap because the caller |
777 | * always holds the page locked, except if called from page_dup_rmap, |
778 | * in which case the page is already known to be setup. |
779 | * |
780 | * We have exclusion against page_add_new_anon_rmap because those pages |
781 | * are initially only visible via the pagetables, and the pte is locked |
782 | * over the call to page_add_new_anon_rmap. |
783 | */ |
784 | BUG_ON(page->index != linear_page_index(vma, address)); |
785 | #endif |
786 | } |
787 | |
788 | /** |
789 | * page_add_anon_rmap - add pte mapping to an anonymous page |
790 | * @page: the page to add the mapping to |
791 | * @vma: the vm area in which the mapping is added |
792 | * @address: the user virtual address mapped |
793 | * |
794 | * The caller needs to hold the pte lock, and the page must be locked in |
795 | * the anon_vma case: to serialize mapping,index checking after setting, |
796 | * and to ensure that PageAnon is not being upgraded racily to PageKsm |
797 | * (but PageKsm is never downgraded to PageAnon). |
798 | */ |
799 | void page_add_anon_rmap(struct page *page, |
800 | struct vm_area_struct *vma, unsigned long address) |
801 | { |
802 | int first = atomic_inc_and_test(&page->_mapcount); |
803 | if (first) |
804 | __inc_zone_page_state(page, NR_ANON_PAGES); |
805 | if (unlikely(PageKsm(page))) |
806 | return; |
807 | |
808 | VM_BUG_ON(!PageLocked(page)); |
809 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
810 | if (first) |
811 | __page_set_anon_rmap(page, vma, address, 0); |
812 | else |
813 | __page_check_anon_rmap(page, vma, address); |
814 | } |
815 | |
816 | /** |
817 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
818 | * @page: the page to add the mapping to |
819 | * @vma: the vm area in which the mapping is added |
820 | * @address: the user virtual address mapped |
821 | * |
822 | * Same as page_add_anon_rmap but must only be called on *new* pages. |
823 | * This means the inc-and-test can be bypassed. |
824 | * Page does not have to be locked. |
825 | */ |
826 | void page_add_new_anon_rmap(struct page *page, |
827 | struct vm_area_struct *vma, unsigned long address) |
828 | { |
829 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
830 | SetPageSwapBacked(page); |
831 | atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */ |
832 | __inc_zone_page_state(page, NR_ANON_PAGES); |
833 | __page_set_anon_rmap(page, vma, address, 1); |
834 | if (page_evictable(page, vma)) |
835 | lru_cache_add_lru(page, LRU_ACTIVE_ANON); |
836 | else |
837 | add_page_to_unevictable_list(page); |
838 | } |
839 | |
840 | /** |
841 | * page_add_file_rmap - add pte mapping to a file page |
842 | * @page: the page to add the mapping to |
843 | * |
844 | * The caller needs to hold the pte lock. |
845 | */ |
846 | void page_add_file_rmap(struct page *page) |
847 | { |
848 | if (atomic_inc_and_test(&page->_mapcount)) { |
849 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
850 | mem_cgroup_update_file_mapped(page, 1); |
851 | } |
852 | } |
853 | |
854 | /** |
855 | * page_remove_rmap - take down pte mapping from a page |
856 | * @page: page to remove mapping from |
857 | * |
858 | * The caller needs to hold the pte lock. |
859 | */ |
860 | void page_remove_rmap(struct page *page) |
861 | { |
862 | /* page still mapped by someone else? */ |
863 | if (!atomic_add_negative(-1, &page->_mapcount)) |
864 | return; |
865 | |
866 | /* |
867 | * Now that the last pte has gone, s390 must transfer dirty |
868 | * flag from storage key to struct page. We can usually skip |
869 | * this if the page is anon, so about to be freed; but perhaps |
870 | * not if it's in swapcache - there might be another pte slot |
871 | * containing the swap entry, but page not yet written to swap. |
872 | */ |
873 | if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) { |
874 | page_clear_dirty(page); |
875 | set_page_dirty(page); |
876 | } |
877 | if (PageAnon(page)) { |
878 | mem_cgroup_uncharge_page(page); |
879 | __dec_zone_page_state(page, NR_ANON_PAGES); |
880 | } else { |
881 | __dec_zone_page_state(page, NR_FILE_MAPPED); |
882 | mem_cgroup_update_file_mapped(page, -1); |
883 | } |
884 | /* |
885 | * It would be tidy to reset the PageAnon mapping here, |
886 | * but that might overwrite a racing page_add_anon_rmap |
887 | * which increments mapcount after us but sets mapping |
888 | * before us: so leave the reset to free_hot_cold_page, |
889 | * and remember that it's only reliable while mapped. |
890 | * Leaving it set also helps swapoff to reinstate ptes |
891 | * faster for those pages still in swapcache. |
892 | */ |
893 | } |
894 | |
895 | /* |
896 | * Subfunctions of try_to_unmap: try_to_unmap_one called |
897 | * repeatedly from either try_to_unmap_anon or try_to_unmap_file. |
898 | */ |
899 | int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
900 | unsigned long address, enum ttu_flags flags) |
901 | { |
902 | struct mm_struct *mm = vma->vm_mm; |
903 | pte_t *pte; |
904 | pte_t pteval; |
905 | spinlock_t *ptl; |
906 | int ret = SWAP_AGAIN; |
907 | |
908 | pte = page_check_address(page, mm, address, &ptl, 0); |
909 | if (!pte) |
910 | goto out; |
911 | |
912 | /* |
913 | * If the page is mlock()d, we cannot swap it out. |
914 | * If it's recently referenced (perhaps page_referenced |
915 | * skipped over this mm) then we should reactivate it. |
916 | */ |
917 | if (!(flags & TTU_IGNORE_MLOCK)) { |
918 | if (vma->vm_flags & VM_LOCKED) |
919 | goto out_mlock; |
920 | |
921 | if (TTU_ACTION(flags) == TTU_MUNLOCK) |
922 | goto out_unmap; |
923 | } |
924 | if (!(flags & TTU_IGNORE_ACCESS)) { |
925 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
926 | ret = SWAP_FAIL; |
927 | goto out_unmap; |
928 | } |
929 | } |
930 | |
931 | /* Nuke the page table entry. */ |
932 | flush_cache_page(vma, address, page_to_pfn(page)); |
933 | pteval = ptep_clear_flush_notify(vma, address, pte); |
934 | |
935 | /* Move the dirty bit to the physical page now the pte is gone. */ |
936 | if (pte_dirty(pteval)) |
937 | set_page_dirty(page); |
938 | |
939 | /* Update high watermark before we lower rss */ |
940 | update_hiwater_rss(mm); |
941 | |
942 | if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
943 | if (PageAnon(page)) |
944 | dec_mm_counter(mm, MM_ANONPAGES); |
945 | else |
946 | dec_mm_counter(mm, MM_FILEPAGES); |
947 | set_pte_at(mm, address, pte, |
948 | swp_entry_to_pte(make_hwpoison_entry(page))); |
949 | } else if (PageAnon(page)) { |
950 | swp_entry_t entry = { .val = page_private(page) }; |
951 | |
952 | if (PageSwapCache(page)) { |
953 | /* |
954 | * Store the swap location in the pte. |
955 | * See handle_pte_fault() ... |
956 | */ |
957 | if (swap_duplicate(entry) < 0) { |
958 | set_pte_at(mm, address, pte, pteval); |
959 | ret = SWAP_FAIL; |
960 | goto out_unmap; |
961 | } |
962 | if (list_empty(&mm->mmlist)) { |
963 | spin_lock(&mmlist_lock); |
964 | if (list_empty(&mm->mmlist)) |
965 | list_add(&mm->mmlist, &init_mm.mmlist); |
966 | spin_unlock(&mmlist_lock); |
967 | } |
968 | dec_mm_counter(mm, MM_ANONPAGES); |
969 | inc_mm_counter(mm, MM_SWAPENTS); |
970 | } else if (PAGE_MIGRATION) { |
971 | /* |
972 | * Store the pfn of the page in a special migration |
973 | * pte. do_swap_page() will wait until the migration |
974 | * pte is removed and then restart fault handling. |
975 | */ |
976 | BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION); |
977 | entry = make_migration_entry(page, pte_write(pteval)); |
978 | } |
979 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
980 | BUG_ON(pte_file(*pte)); |
981 | } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) { |
982 | /* Establish migration entry for a file page */ |
983 | swp_entry_t entry; |
984 | entry = make_migration_entry(page, pte_write(pteval)); |
985 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
986 | } else |
987 | dec_mm_counter(mm, MM_FILEPAGES); |
988 | |
989 | page_remove_rmap(page); |
990 | page_cache_release(page); |
991 | |
992 | out_unmap: |
993 | pte_unmap_unlock(pte, ptl); |
994 | out: |
995 | return ret; |
996 | |
997 | out_mlock: |
998 | pte_unmap_unlock(pte, ptl); |
999 | |
1000 | |
1001 | /* |
1002 | * We need mmap_sem locking, Otherwise VM_LOCKED check makes |
1003 | * unstable result and race. Plus, We can't wait here because |
1004 | * we now hold anon_vma->lock or mapping->i_mmap_lock. |
1005 | * if trylock failed, the page remain in evictable lru and later |
1006 | * vmscan could retry to move the page to unevictable lru if the |
1007 | * page is actually mlocked. |
1008 | */ |
1009 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
1010 | if (vma->vm_flags & VM_LOCKED) { |
1011 | mlock_vma_page(page); |
1012 | ret = SWAP_MLOCK; |
1013 | } |
1014 | up_read(&vma->vm_mm->mmap_sem); |
1015 | } |
1016 | return ret; |
1017 | } |
1018 | |
1019 | /* |
1020 | * objrmap doesn't work for nonlinear VMAs because the assumption that |
1021 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. |
1022 | * Consequently, given a particular page and its ->index, we cannot locate the |
1023 | * ptes which are mapping that page without an exhaustive linear search. |
1024 | * |
1025 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which |
1026 | * maps the file to which the target page belongs. The ->vm_private_data field |
1027 | * holds the current cursor into that scan. Successive searches will circulate |
1028 | * around the vma's virtual address space. |
1029 | * |
1030 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, |
1031 | * more scanning pressure is placed against them as well. Eventually pages |
1032 | * will become fully unmapped and are eligible for eviction. |
1033 | * |
1034 | * For very sparsely populated VMAs this is a little inefficient - chances are |
1035 | * there there won't be many ptes located within the scan cluster. In this case |
1036 | * maybe we could scan further - to the end of the pte page, perhaps. |
1037 | * |
1038 | * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can |
1039 | * acquire it without blocking. If vma locked, mlock the pages in the cluster, |
1040 | * rather than unmapping them. If we encounter the "check_page" that vmscan is |
1041 | * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. |
1042 | */ |
1043 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) |
1044 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) |
1045 | |
1046 | static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, |
1047 | struct vm_area_struct *vma, struct page *check_page) |
1048 | { |
1049 | struct mm_struct *mm = vma->vm_mm; |
1050 | pgd_t *pgd; |
1051 | pud_t *pud; |
1052 | pmd_t *pmd; |
1053 | pte_t *pte; |
1054 | pte_t pteval; |
1055 | spinlock_t *ptl; |
1056 | struct page *page; |
1057 | unsigned long address; |
1058 | unsigned long end; |
1059 | int ret = SWAP_AGAIN; |
1060 | int locked_vma = 0; |
1061 | |
1062 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
1063 | end = address + CLUSTER_SIZE; |
1064 | if (address < vma->vm_start) |
1065 | address = vma->vm_start; |
1066 | if (end > vma->vm_end) |
1067 | end = vma->vm_end; |
1068 | |
1069 | pgd = pgd_offset(mm, address); |
1070 | if (!pgd_present(*pgd)) |
1071 | return ret; |
1072 | |
1073 | pud = pud_offset(pgd, address); |
1074 | if (!pud_present(*pud)) |
1075 | return ret; |
1076 | |
1077 | pmd = pmd_offset(pud, address); |
1078 | if (!pmd_present(*pmd)) |
1079 | return ret; |
1080 | |
1081 | /* |
1082 | * If we can acquire the mmap_sem for read, and vma is VM_LOCKED, |
1083 | * keep the sem while scanning the cluster for mlocking pages. |
1084 | */ |
1085 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
1086 | locked_vma = (vma->vm_flags & VM_LOCKED); |
1087 | if (!locked_vma) |
1088 | up_read(&vma->vm_mm->mmap_sem); /* don't need it */ |
1089 | } |
1090 | |
1091 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
1092 | |
1093 | /* Update high watermark before we lower rss */ |
1094 | update_hiwater_rss(mm); |
1095 | |
1096 | for (; address < end; pte++, address += PAGE_SIZE) { |
1097 | if (!pte_present(*pte)) |
1098 | continue; |
1099 | page = vm_normal_page(vma, address, *pte); |
1100 | BUG_ON(!page || PageAnon(page)); |
1101 | |
1102 | if (locked_vma) { |
1103 | mlock_vma_page(page); /* no-op if already mlocked */ |
1104 | if (page == check_page) |
1105 | ret = SWAP_MLOCK; |
1106 | continue; /* don't unmap */ |
1107 | } |
1108 | |
1109 | if (ptep_clear_flush_young_notify(vma, address, pte)) |
1110 | continue; |
1111 | |
1112 | /* Nuke the page table entry. */ |
1113 | flush_cache_page(vma, address, pte_pfn(*pte)); |
1114 | pteval = ptep_clear_flush_notify(vma, address, pte); |
1115 | |
1116 | /* If nonlinear, store the file page offset in the pte. */ |
1117 | if (page->index != linear_page_index(vma, address)) |
1118 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); |
1119 | |
1120 | /* Move the dirty bit to the physical page now the pte is gone. */ |
1121 | if (pte_dirty(pteval)) |
1122 | set_page_dirty(page); |
1123 | |
1124 | page_remove_rmap(page); |
1125 | page_cache_release(page); |
1126 | dec_mm_counter(mm, MM_FILEPAGES); |
1127 | (*mapcount)--; |
1128 | } |
1129 | pte_unmap_unlock(pte - 1, ptl); |
1130 | if (locked_vma) |
1131 | up_read(&vma->vm_mm->mmap_sem); |
1132 | return ret; |
1133 | } |
1134 | |
1135 | /** |
1136 | * try_to_unmap_anon - unmap or unlock anonymous page using the object-based |
1137 | * rmap method |
1138 | * @page: the page to unmap/unlock |
1139 | * @flags: action and flags |
1140 | * |
1141 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1142 | * contained in the anon_vma struct it points to. |
1143 | * |
1144 | * This function is only called from try_to_unmap/try_to_munlock for |
1145 | * anonymous pages. |
1146 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1147 | * where the page was found will be held for write. So, we won't recheck |
1148 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1149 | * 'LOCKED. |
1150 | */ |
1151 | static int try_to_unmap_anon(struct page *page, enum ttu_flags flags) |
1152 | { |
1153 | struct anon_vma *anon_vma; |
1154 | struct anon_vma_chain *avc; |
1155 | int ret = SWAP_AGAIN; |
1156 | |
1157 | anon_vma = page_lock_anon_vma(page); |
1158 | if (!anon_vma) |
1159 | return ret; |
1160 | |
1161 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1162 | struct vm_area_struct *vma = avc->vma; |
1163 | unsigned long address = vma_address(page, vma); |
1164 | if (address == -EFAULT) |
1165 | continue; |
1166 | ret = try_to_unmap_one(page, vma, address, flags); |
1167 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1168 | break; |
1169 | } |
1170 | |
1171 | page_unlock_anon_vma(anon_vma); |
1172 | return ret; |
1173 | } |
1174 | |
1175 | /** |
1176 | * try_to_unmap_file - unmap/unlock file page using the object-based rmap method |
1177 | * @page: the page to unmap/unlock |
1178 | * @flags: action and flags |
1179 | * |
1180 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1181 | * contained in the address_space struct it points to. |
1182 | * |
1183 | * This function is only called from try_to_unmap/try_to_munlock for |
1184 | * object-based pages. |
1185 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1186 | * where the page was found will be held for write. So, we won't recheck |
1187 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1188 | * 'LOCKED. |
1189 | */ |
1190 | static int try_to_unmap_file(struct page *page, enum ttu_flags flags) |
1191 | { |
1192 | struct address_space *mapping = page->mapping; |
1193 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
1194 | struct vm_area_struct *vma; |
1195 | struct prio_tree_iter iter; |
1196 | int ret = SWAP_AGAIN; |
1197 | unsigned long cursor; |
1198 | unsigned long max_nl_cursor = 0; |
1199 | unsigned long max_nl_size = 0; |
1200 | unsigned int mapcount; |
1201 | |
1202 | spin_lock(&mapping->i_mmap_lock); |
1203 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1204 | unsigned long address = vma_address(page, vma); |
1205 | if (address == -EFAULT) |
1206 | continue; |
1207 | ret = try_to_unmap_one(page, vma, address, flags); |
1208 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1209 | goto out; |
1210 | } |
1211 | |
1212 | if (list_empty(&mapping->i_mmap_nonlinear)) |
1213 | goto out; |
1214 | |
1215 | /* |
1216 | * We don't bother to try to find the munlocked page in nonlinears. |
1217 | * It's costly. Instead, later, page reclaim logic may call |
1218 | * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily. |
1219 | */ |
1220 | if (TTU_ACTION(flags) == TTU_MUNLOCK) |
1221 | goto out; |
1222 | |
1223 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1224 | shared.vm_set.list) { |
1225 | cursor = (unsigned long) vma->vm_private_data; |
1226 | if (cursor > max_nl_cursor) |
1227 | max_nl_cursor = cursor; |
1228 | cursor = vma->vm_end - vma->vm_start; |
1229 | if (cursor > max_nl_size) |
1230 | max_nl_size = cursor; |
1231 | } |
1232 | |
1233 | if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ |
1234 | ret = SWAP_FAIL; |
1235 | goto out; |
1236 | } |
1237 | |
1238 | /* |
1239 | * We don't try to search for this page in the nonlinear vmas, |
1240 | * and page_referenced wouldn't have found it anyway. Instead |
1241 | * just walk the nonlinear vmas trying to age and unmap some. |
1242 | * The mapcount of the page we came in with is irrelevant, |
1243 | * but even so use it as a guide to how hard we should try? |
1244 | */ |
1245 | mapcount = page_mapcount(page); |
1246 | if (!mapcount) |
1247 | goto out; |
1248 | cond_resched_lock(&mapping->i_mmap_lock); |
1249 | |
1250 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; |
1251 | if (max_nl_cursor == 0) |
1252 | max_nl_cursor = CLUSTER_SIZE; |
1253 | |
1254 | do { |
1255 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1256 | shared.vm_set.list) { |
1257 | cursor = (unsigned long) vma->vm_private_data; |
1258 | while ( cursor < max_nl_cursor && |
1259 | cursor < vma->vm_end - vma->vm_start) { |
1260 | if (try_to_unmap_cluster(cursor, &mapcount, |
1261 | vma, page) == SWAP_MLOCK) |
1262 | ret = SWAP_MLOCK; |
1263 | cursor += CLUSTER_SIZE; |
1264 | vma->vm_private_data = (void *) cursor; |
1265 | if ((int)mapcount <= 0) |
1266 | goto out; |
1267 | } |
1268 | vma->vm_private_data = (void *) max_nl_cursor; |
1269 | } |
1270 | cond_resched_lock(&mapping->i_mmap_lock); |
1271 | max_nl_cursor += CLUSTER_SIZE; |
1272 | } while (max_nl_cursor <= max_nl_size); |
1273 | |
1274 | /* |
1275 | * Don't loop forever (perhaps all the remaining pages are |
1276 | * in locked vmas). Reset cursor on all unreserved nonlinear |
1277 | * vmas, now forgetting on which ones it had fallen behind. |
1278 | */ |
1279 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
1280 | vma->vm_private_data = NULL; |
1281 | out: |
1282 | spin_unlock(&mapping->i_mmap_lock); |
1283 | return ret; |
1284 | } |
1285 | |
1286 | /** |
1287 | * try_to_unmap - try to remove all page table mappings to a page |
1288 | * @page: the page to get unmapped |
1289 | * @flags: action and flags |
1290 | * |
1291 | * Tries to remove all the page table entries which are mapping this |
1292 | * page, used in the pageout path. Caller must hold the page lock. |
1293 | * Return values are: |
1294 | * |
1295 | * SWAP_SUCCESS - we succeeded in removing all mappings |
1296 | * SWAP_AGAIN - we missed a mapping, try again later |
1297 | * SWAP_FAIL - the page is unswappable |
1298 | * SWAP_MLOCK - page is mlocked. |
1299 | */ |
1300 | int try_to_unmap(struct page *page, enum ttu_flags flags) |
1301 | { |
1302 | int ret; |
1303 | |
1304 | BUG_ON(!PageLocked(page)); |
1305 | |
1306 | if (unlikely(PageKsm(page))) |
1307 | ret = try_to_unmap_ksm(page, flags); |
1308 | else if (PageAnon(page)) |
1309 | ret = try_to_unmap_anon(page, flags); |
1310 | else |
1311 | ret = try_to_unmap_file(page, flags); |
1312 | if (ret != SWAP_MLOCK && !page_mapped(page)) |
1313 | ret = SWAP_SUCCESS; |
1314 | return ret; |
1315 | } |
1316 | |
1317 | /** |
1318 | * try_to_munlock - try to munlock a page |
1319 | * @page: the page to be munlocked |
1320 | * |
1321 | * Called from munlock code. Checks all of the VMAs mapping the page |
1322 | * to make sure nobody else has this page mlocked. The page will be |
1323 | * returned with PG_mlocked cleared if no other vmas have it mlocked. |
1324 | * |
1325 | * Return values are: |
1326 | * |
1327 | * SWAP_AGAIN - no vma is holding page mlocked, or, |
1328 | * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem |
1329 | * SWAP_FAIL - page cannot be located at present |
1330 | * SWAP_MLOCK - page is now mlocked. |
1331 | */ |
1332 | int try_to_munlock(struct page *page) |
1333 | { |
1334 | VM_BUG_ON(!PageLocked(page) || PageLRU(page)); |
1335 | |
1336 | if (unlikely(PageKsm(page))) |
1337 | return try_to_unmap_ksm(page, TTU_MUNLOCK); |
1338 | else if (PageAnon(page)) |
1339 | return try_to_unmap_anon(page, TTU_MUNLOCK); |
1340 | else |
1341 | return try_to_unmap_file(page, TTU_MUNLOCK); |
1342 | } |
1343 | |
1344 | #ifdef CONFIG_MIGRATION |
1345 | /* |
1346 | * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file(): |
1347 | * Called by migrate.c to remove migration ptes, but might be used more later. |
1348 | */ |
1349 | static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, |
1350 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1351 | { |
1352 | struct anon_vma *anon_vma; |
1353 | struct anon_vma_chain *avc; |
1354 | int ret = SWAP_AGAIN; |
1355 | |
1356 | /* |
1357 | * Note: remove_migration_ptes() cannot use page_lock_anon_vma() |
1358 | * because that depends on page_mapped(); but not all its usages |
1359 | * are holding mmap_sem, which also gave the necessary guarantee |
1360 | * (that this anon_vma's slab has not already been destroyed). |
1361 | * This needs to be reviewed later: avoiding page_lock_anon_vma() |
1362 | * is risky, and currently limits the usefulness of rmap_walk(). |
1363 | */ |
1364 | anon_vma = page_anon_vma(page); |
1365 | if (!anon_vma) |
1366 | return ret; |
1367 | spin_lock(&anon_vma->lock); |
1368 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1369 | struct vm_area_struct *vma = avc->vma; |
1370 | unsigned long address = vma_address(page, vma); |
1371 | if (address == -EFAULT) |
1372 | continue; |
1373 | ret = rmap_one(page, vma, address, arg); |
1374 | if (ret != SWAP_AGAIN) |
1375 | break; |
1376 | } |
1377 | spin_unlock(&anon_vma->lock); |
1378 | return ret; |
1379 | } |
1380 | |
1381 | static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *, |
1382 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1383 | { |
1384 | struct address_space *mapping = page->mapping; |
1385 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
1386 | struct vm_area_struct *vma; |
1387 | struct prio_tree_iter iter; |
1388 | int ret = SWAP_AGAIN; |
1389 | |
1390 | if (!mapping) |
1391 | return ret; |
1392 | spin_lock(&mapping->i_mmap_lock); |
1393 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1394 | unsigned long address = vma_address(page, vma); |
1395 | if (address == -EFAULT) |
1396 | continue; |
1397 | ret = rmap_one(page, vma, address, arg); |
1398 | if (ret != SWAP_AGAIN) |
1399 | break; |
1400 | } |
1401 | /* |
1402 | * No nonlinear handling: being always shared, nonlinear vmas |
1403 | * never contain migration ptes. Decide what to do about this |
1404 | * limitation to linear when we need rmap_walk() on nonlinear. |
1405 | */ |
1406 | spin_unlock(&mapping->i_mmap_lock); |
1407 | return ret; |
1408 | } |
1409 | |
1410 | int rmap_walk(struct page *page, int (*rmap_one)(struct page *, |
1411 | struct vm_area_struct *, unsigned long, void *), void *arg) |
1412 | { |
1413 | VM_BUG_ON(!PageLocked(page)); |
1414 | |
1415 | if (unlikely(PageKsm(page))) |
1416 | return rmap_walk_ksm(page, rmap_one, arg); |
1417 | else if (PageAnon(page)) |
1418 | return rmap_walk_anon(page, rmap_one, arg); |
1419 | else |
1420 | return rmap_walk_file(page, rmap_one, arg); |
1421 | } |
1422 | #endif /* CONFIG_MIGRATION */ |
1423 |
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