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