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 | * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share) |
27 | * mapping->i_mmap_rwsem |
28 | * anon_vma->rwsem |
29 | * mm->page_table_lock or pte_lock |
30 | * pgdat->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 | * mem_cgroup_{begin,end}_page_stat (memcg->move_lock) |
35 | * i_pages lock (widely used) |
36 | * inode->i_lock (in set_page_dirty's __mark_inode_dirty) |
37 | * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty) |
38 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
39 | * i_pages lock (widely used, in set_page_dirty, |
40 | * in arch-dependent flush_dcache_mmap_lock, |
41 | * within bdi.wb->list_lock in __sync_single_inode) |
42 | * |
43 | * anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon) |
44 | * ->tasklist_lock |
45 | * pte map lock |
46 | */ |
47 | |
48 | #include <linux/mm.h> |
49 | #include <linux/sched/mm.h> |
50 | #include <linux/sched/task.h> |
51 | #include <linux/pagemap.h> |
52 | #include <linux/swap.h> |
53 | #include <linux/swapops.h> |
54 | #include <linux/slab.h> |
55 | #include <linux/init.h> |
56 | #include <linux/ksm.h> |
57 | #include <linux/rmap.h> |
58 | #include <linux/rcupdate.h> |
59 | #include <linux/export.h> |
60 | #include <linux/memcontrol.h> |
61 | #include <linux/mmu_notifier.h> |
62 | #include <linux/migrate.h> |
63 | #include <linux/hugetlb.h> |
64 | #include <linux/backing-dev.h> |
65 | #include <linux/page_idle.h> |
66 | #include <linux/memremap.h> |
67 | #include <linux/userfaultfd_k.h> |
68 | |
69 | #include <asm/tlbflush.h> |
70 | |
71 | #include <trace/events/tlb.h> |
72 | |
73 | #include "internal.h" |
74 | |
75 | static struct kmem_cache *anon_vma_cachep; |
76 | static struct kmem_cache *anon_vma_chain_cachep; |
77 | |
78 | static inline struct anon_vma *anon_vma_alloc(void) |
79 | { |
80 | struct anon_vma *anon_vma; |
81 | |
82 | anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
83 | if (anon_vma) { |
84 | atomic_set(&anon_vma->refcount, 1); |
85 | anon_vma->degree = 1; /* Reference for first vma */ |
86 | anon_vma->parent = anon_vma; |
87 | /* |
88 | * Initialise the anon_vma root to point to itself. If called |
89 | * from fork, the root will be reset to the parents anon_vma. |
90 | */ |
91 | anon_vma->root = anon_vma; |
92 | } |
93 | |
94 | return anon_vma; |
95 | } |
96 | |
97 | static inline void anon_vma_free(struct anon_vma *anon_vma) |
98 | { |
99 | VM_BUG_ON(atomic_read(&anon_vma->refcount)); |
100 | |
101 | /* |
102 | * Synchronize against page_lock_anon_vma_read() such that |
103 | * we can safely hold the lock without the anon_vma getting |
104 | * freed. |
105 | * |
106 | * Relies on the full mb implied by the atomic_dec_and_test() from |
107 | * put_anon_vma() against the acquire barrier implied by |
108 | * down_read_trylock() from page_lock_anon_vma_read(). This orders: |
109 | * |
110 | * page_lock_anon_vma_read() VS put_anon_vma() |
111 | * down_read_trylock() atomic_dec_and_test() |
112 | * LOCK MB |
113 | * atomic_read() rwsem_is_locked() |
114 | * |
115 | * LOCK should suffice since the actual taking of the lock must |
116 | * happen _before_ what follows. |
117 | */ |
118 | might_sleep(); |
119 | if (rwsem_is_locked(&anon_vma->root->rwsem)) { |
120 | anon_vma_lock_write(anon_vma); |
121 | anon_vma_unlock_write(anon_vma); |
122 | } |
123 | |
124 | kmem_cache_free(anon_vma_cachep, anon_vma); |
125 | } |
126 | |
127 | static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp) |
128 | { |
129 | return kmem_cache_alloc(anon_vma_chain_cachep, gfp); |
130 | } |
131 | |
132 | static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
133 | { |
134 | kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); |
135 | } |
136 | |
137 | static void anon_vma_chain_link(struct vm_area_struct *vma, |
138 | struct anon_vma_chain *avc, |
139 | struct anon_vma *anon_vma) |
140 | { |
141 | avc->vma = vma; |
142 | avc->anon_vma = anon_vma; |
143 | list_add(&avc->same_vma, &vma->anon_vma_chain); |
144 | anon_vma_interval_tree_insert(avc, &anon_vma->rb_root); |
145 | } |
146 | |
147 | /** |
148 | * __anon_vma_prepare - attach an anon_vma to a memory region |
149 | * @vma: the memory region in question |
150 | * |
151 | * This makes sure the memory mapping described by 'vma' has |
152 | * an 'anon_vma' attached to it, so that we can associate the |
153 | * anonymous pages mapped into it with that anon_vma. |
154 | * |
155 | * The common case will be that we already have one, which |
156 | * is handled inline by anon_vma_prepare(). But if |
157 | * not we either need to find an adjacent mapping that we |
158 | * can re-use the anon_vma from (very common when the only |
159 | * reason for splitting a vma has been mprotect()), or we |
160 | * allocate a new one. |
161 | * |
162 | * Anon-vma allocations are very subtle, because we may have |
163 | * optimistically looked up an anon_vma in page_lock_anon_vma_read() |
164 | * and that may actually touch the spinlock even in the newly |
165 | * allocated vma (it depends on RCU to make sure that the |
166 | * anon_vma isn't actually destroyed). |
167 | * |
168 | * As a result, we need to do proper anon_vma locking even |
169 | * for the new allocation. At the same time, we do not want |
170 | * to do any locking for the common case of already having |
171 | * an anon_vma. |
172 | * |
173 | * This must be called with the mmap_sem held for reading. |
174 | */ |
175 | int __anon_vma_prepare(struct vm_area_struct *vma) |
176 | { |
177 | struct mm_struct *mm = vma->vm_mm; |
178 | struct anon_vma *anon_vma, *allocated; |
179 | struct anon_vma_chain *avc; |
180 | |
181 | might_sleep(); |
182 | |
183 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
184 | if (!avc) |
185 | goto out_enomem; |
186 | |
187 | anon_vma = find_mergeable_anon_vma(vma); |
188 | allocated = NULL; |
189 | if (!anon_vma) { |
190 | anon_vma = anon_vma_alloc(); |
191 | if (unlikely(!anon_vma)) |
192 | goto out_enomem_free_avc; |
193 | allocated = anon_vma; |
194 | } |
195 | |
196 | anon_vma_lock_write(anon_vma); |
197 | /* page_table_lock to protect against threads */ |
198 | spin_lock(&mm->page_table_lock); |
199 | if (likely(!vma->anon_vma)) { |
200 | vma->anon_vma = anon_vma; |
201 | anon_vma_chain_link(vma, avc, anon_vma); |
202 | /* vma reference or self-parent link for new root */ |
203 | anon_vma->degree++; |
204 | allocated = NULL; |
205 | avc = NULL; |
206 | } |
207 | spin_unlock(&mm->page_table_lock); |
208 | anon_vma_unlock_write(anon_vma); |
209 | |
210 | if (unlikely(allocated)) |
211 | put_anon_vma(allocated); |
212 | if (unlikely(avc)) |
213 | anon_vma_chain_free(avc); |
214 | |
215 | return 0; |
216 | |
217 | out_enomem_free_avc: |
218 | anon_vma_chain_free(avc); |
219 | out_enomem: |
220 | return -ENOMEM; |
221 | } |
222 | |
223 | /* |
224 | * This is a useful helper function for locking the anon_vma root as |
225 | * we traverse the vma->anon_vma_chain, looping over anon_vma's that |
226 | * have the same vma. |
227 | * |
228 | * Such anon_vma's should have the same root, so you'd expect to see |
229 | * just a single mutex_lock for the whole traversal. |
230 | */ |
231 | static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) |
232 | { |
233 | struct anon_vma *new_root = anon_vma->root; |
234 | if (new_root != root) { |
235 | if (WARN_ON_ONCE(root)) |
236 | up_write(&root->rwsem); |
237 | root = new_root; |
238 | down_write(&root->rwsem); |
239 | } |
240 | return root; |
241 | } |
242 | |
243 | static inline void unlock_anon_vma_root(struct anon_vma *root) |
244 | { |
245 | if (root) |
246 | up_write(&root->rwsem); |
247 | } |
248 | |
249 | /* |
250 | * Attach the anon_vmas from src to dst. |
251 | * Returns 0 on success, -ENOMEM on failure. |
252 | * |
253 | * If dst->anon_vma is NULL this function tries to find and reuse existing |
254 | * anon_vma which has no vmas and only one child anon_vma. This prevents |
255 | * degradation of anon_vma hierarchy to endless linear chain in case of |
256 | * constantly forking task. On the other hand, an anon_vma with more than one |
257 | * child isn't reused even if there was no alive vma, thus rmap walker has a |
258 | * good chance of avoiding scanning the whole hierarchy when it searches where |
259 | * page is mapped. |
260 | */ |
261 | int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
262 | { |
263 | struct anon_vma_chain *avc, *pavc; |
264 | struct anon_vma *root = NULL; |
265 | |
266 | list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
267 | struct anon_vma *anon_vma; |
268 | |
269 | avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); |
270 | if (unlikely(!avc)) { |
271 | unlock_anon_vma_root(root); |
272 | root = NULL; |
273 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
274 | if (!avc) |
275 | goto enomem_failure; |
276 | } |
277 | anon_vma = pavc->anon_vma; |
278 | root = lock_anon_vma_root(root, anon_vma); |
279 | anon_vma_chain_link(dst, avc, anon_vma); |
280 | |
281 | /* |
282 | * Reuse existing anon_vma if its degree lower than two, |
283 | * that means it has no vma and only one anon_vma child. |
284 | * |
285 | * Do not chose parent anon_vma, otherwise first child |
286 | * will always reuse it. Root anon_vma is never reused: |
287 | * it has self-parent reference and at least one child. |
288 | */ |
289 | if (!dst->anon_vma && anon_vma != src->anon_vma && |
290 | anon_vma->degree < 2) |
291 | dst->anon_vma = anon_vma; |
292 | } |
293 | if (dst->anon_vma) |
294 | dst->anon_vma->degree++; |
295 | unlock_anon_vma_root(root); |
296 | return 0; |
297 | |
298 | enomem_failure: |
299 | /* |
300 | * dst->anon_vma is dropped here otherwise its degree can be incorrectly |
301 | * decremented in unlink_anon_vmas(). |
302 | * We can safely do this because callers of anon_vma_clone() don't care |
303 | * about dst->anon_vma if anon_vma_clone() failed. |
304 | */ |
305 | dst->anon_vma = NULL; |
306 | unlink_anon_vmas(dst); |
307 | return -ENOMEM; |
308 | } |
309 | |
310 | /* |
311 | * Attach vma to its own anon_vma, as well as to the anon_vmas that |
312 | * the corresponding VMA in the parent process is attached to. |
313 | * Returns 0 on success, non-zero on failure. |
314 | */ |
315 | int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
316 | { |
317 | struct anon_vma_chain *avc; |
318 | struct anon_vma *anon_vma; |
319 | int error; |
320 | |
321 | /* Don't bother if the parent process has no anon_vma here. */ |
322 | if (!pvma->anon_vma) |
323 | return 0; |
324 | |
325 | /* Drop inherited anon_vma, we'll reuse existing or allocate new. */ |
326 | vma->anon_vma = NULL; |
327 | |
328 | /* |
329 | * First, attach the new VMA to the parent VMA's anon_vmas, |
330 | * so rmap can find non-COWed pages in child processes. |
331 | */ |
332 | error = anon_vma_clone(vma, pvma); |
333 | if (error) |
334 | return error; |
335 | |
336 | /* An existing anon_vma has been reused, all done then. */ |
337 | if (vma->anon_vma) |
338 | return 0; |
339 | |
340 | /* Then add our own anon_vma. */ |
341 | anon_vma = anon_vma_alloc(); |
342 | if (!anon_vma) |
343 | goto out_error; |
344 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
345 | if (!avc) |
346 | goto out_error_free_anon_vma; |
347 | |
348 | /* |
349 | * The root anon_vma's spinlock is the lock actually used when we |
350 | * lock any of the anon_vmas in this anon_vma tree. |
351 | */ |
352 | anon_vma->root = pvma->anon_vma->root; |
353 | anon_vma->parent = pvma->anon_vma; |
354 | /* |
355 | * With refcounts, an anon_vma can stay around longer than the |
356 | * process it belongs to. The root anon_vma needs to be pinned until |
357 | * this anon_vma is freed, because the lock lives in the root. |
358 | */ |
359 | get_anon_vma(anon_vma->root); |
360 | /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
361 | vma->anon_vma = anon_vma; |
362 | anon_vma_lock_write(anon_vma); |
363 | anon_vma_chain_link(vma, avc, anon_vma); |
364 | anon_vma->parent->degree++; |
365 | anon_vma_unlock_write(anon_vma); |
366 | |
367 | return 0; |
368 | |
369 | out_error_free_anon_vma: |
370 | put_anon_vma(anon_vma); |
371 | out_error: |
372 | unlink_anon_vmas(vma); |
373 | return -ENOMEM; |
374 | } |
375 | |
376 | void unlink_anon_vmas(struct vm_area_struct *vma) |
377 | { |
378 | struct anon_vma_chain *avc, *next; |
379 | struct anon_vma *root = NULL; |
380 | |
381 | /* |
382 | * Unlink each anon_vma chained to the VMA. This list is ordered |
383 | * from newest to oldest, ensuring the root anon_vma gets freed last. |
384 | */ |
385 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
386 | struct anon_vma *anon_vma = avc->anon_vma; |
387 | |
388 | root = lock_anon_vma_root(root, anon_vma); |
389 | anon_vma_interval_tree_remove(avc, &anon_vma->rb_root); |
390 | |
391 | /* |
392 | * Leave empty anon_vmas on the list - we'll need |
393 | * to free them outside the lock. |
394 | */ |
395 | if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) { |
396 | anon_vma->parent->degree--; |
397 | continue; |
398 | } |
399 | |
400 | list_del(&avc->same_vma); |
401 | anon_vma_chain_free(avc); |
402 | } |
403 | if (vma->anon_vma) |
404 | vma->anon_vma->degree--; |
405 | unlock_anon_vma_root(root); |
406 | |
407 | /* |
408 | * Iterate the list once more, it now only contains empty and unlinked |
409 | * anon_vmas, destroy them. Could not do before due to __put_anon_vma() |
410 | * needing to write-acquire the anon_vma->root->rwsem. |
411 | */ |
412 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
413 | struct anon_vma *anon_vma = avc->anon_vma; |
414 | |
415 | VM_WARN_ON(anon_vma->degree); |
416 | put_anon_vma(anon_vma); |
417 | |
418 | list_del(&avc->same_vma); |
419 | anon_vma_chain_free(avc); |
420 | } |
421 | } |
422 | |
423 | static void anon_vma_ctor(void *data) |
424 | { |
425 | struct anon_vma *anon_vma = data; |
426 | |
427 | init_rwsem(&anon_vma->rwsem); |
428 | atomic_set(&anon_vma->refcount, 0); |
429 | anon_vma->rb_root = RB_ROOT_CACHED; |
430 | } |
431 | |
432 | void __init anon_vma_init(void) |
433 | { |
434 | anon_vma_cachep = kmem_cache_create("anon_vma" , sizeof(struct anon_vma), |
435 | 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT, |
436 | anon_vma_ctor); |
437 | anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, |
438 | SLAB_PANIC|SLAB_ACCOUNT); |
439 | } |
440 | |
441 | /* |
442 | * Getting a lock on a stable anon_vma from a page off the LRU is tricky! |
443 | * |
444 | * Since there is no serialization what so ever against page_remove_rmap() |
445 | * the best this function can do is return a locked anon_vma that might |
446 | * have been relevant to this page. |
447 | * |
448 | * The page might have been remapped to a different anon_vma or the anon_vma |
449 | * returned may already be freed (and even reused). |
450 | * |
451 | * In case it was remapped to a different anon_vma, the new anon_vma will be a |
452 | * child of the old anon_vma, and the anon_vma lifetime rules will therefore |
453 | * ensure that any anon_vma obtained from the page will still be valid for as |
454 | * long as we observe page_mapped() [ hence all those page_mapped() tests ]. |
455 | * |
456 | * All users of this function must be very careful when walking the anon_vma |
457 | * chain and verify that the page in question is indeed mapped in it |
458 | * [ something equivalent to page_mapped_in_vma() ]. |
459 | * |
460 | * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap() |
461 | * that the anon_vma pointer from page->mapping is valid if there is a |
462 | * mapcount, we can dereference the anon_vma after observing those. |
463 | */ |
464 | struct anon_vma *page_get_anon_vma(struct page *page) |
465 | { |
466 | struct anon_vma *anon_vma = NULL; |
467 | unsigned long anon_mapping; |
468 | |
469 | rcu_read_lock(); |
470 | anon_mapping = (unsigned long)READ_ONCE(page->mapping); |
471 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
472 | goto out; |
473 | if (!page_mapped(page)) |
474 | goto out; |
475 | |
476 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
477 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
478 | anon_vma = NULL; |
479 | goto out; |
480 | } |
481 | |
482 | /* |
483 | * If this page is still mapped, then its anon_vma cannot have been |
484 | * freed. But if it has been unmapped, we have no security against the |
485 | * anon_vma structure being freed and reused (for another anon_vma: |
486 | * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero() |
487 | * above cannot corrupt). |
488 | */ |
489 | if (!page_mapped(page)) { |
490 | rcu_read_unlock(); |
491 | put_anon_vma(anon_vma); |
492 | return NULL; |
493 | } |
494 | out: |
495 | rcu_read_unlock(); |
496 | |
497 | return anon_vma; |
498 | } |
499 | |
500 | /* |
501 | * Similar to page_get_anon_vma() except it locks the anon_vma. |
502 | * |
503 | * Its a little more complex as it tries to keep the fast path to a single |
504 | * atomic op -- the trylock. If we fail the trylock, we fall back to getting a |
505 | * reference like with page_get_anon_vma() and then block on the mutex. |
506 | */ |
507 | struct anon_vma *page_lock_anon_vma_read(struct page *page) |
508 | { |
509 | struct anon_vma *anon_vma = NULL; |
510 | struct anon_vma *root_anon_vma; |
511 | unsigned long anon_mapping; |
512 | |
513 | rcu_read_lock(); |
514 | anon_mapping = (unsigned long)READ_ONCE(page->mapping); |
515 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
516 | goto out; |
517 | if (!page_mapped(page)) |
518 | goto out; |
519 | |
520 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
521 | root_anon_vma = READ_ONCE(anon_vma->root); |
522 | if (down_read_trylock(&root_anon_vma->rwsem)) { |
523 | /* |
524 | * If the page is still mapped, then this anon_vma is still |
525 | * its anon_vma, and holding the mutex ensures that it will |
526 | * not go away, see anon_vma_free(). |
527 | */ |
528 | if (!page_mapped(page)) { |
529 | up_read(&root_anon_vma->rwsem); |
530 | anon_vma = NULL; |
531 | } |
532 | goto out; |
533 | } |
534 | |
535 | /* trylock failed, we got to sleep */ |
536 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
537 | anon_vma = NULL; |
538 | goto out; |
539 | } |
540 | |
541 | if (!page_mapped(page)) { |
542 | rcu_read_unlock(); |
543 | put_anon_vma(anon_vma); |
544 | return NULL; |
545 | } |
546 | |
547 | /* we pinned the anon_vma, its safe to sleep */ |
548 | rcu_read_unlock(); |
549 | anon_vma_lock_read(anon_vma); |
550 | |
551 | if (atomic_dec_and_test(&anon_vma->refcount)) { |
552 | /* |
553 | * Oops, we held the last refcount, release the lock |
554 | * and bail -- can't simply use put_anon_vma() because |
555 | * we'll deadlock on the anon_vma_lock_write() recursion. |
556 | */ |
557 | anon_vma_unlock_read(anon_vma); |
558 | __put_anon_vma(anon_vma); |
559 | anon_vma = NULL; |
560 | } |
561 | |
562 | return anon_vma; |
563 | |
564 | out: |
565 | rcu_read_unlock(); |
566 | return anon_vma; |
567 | } |
568 | |
569 | void page_unlock_anon_vma_read(struct anon_vma *anon_vma) |
570 | { |
571 | anon_vma_unlock_read(anon_vma); |
572 | } |
573 | |
574 | #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH |
575 | /* |
576 | * Flush TLB entries for recently unmapped pages from remote CPUs. It is |
577 | * important if a PTE was dirty when it was unmapped that it's flushed |
578 | * before any IO is initiated on the page to prevent lost writes. Similarly, |
579 | * it must be flushed before freeing to prevent data leakage. |
580 | */ |
581 | void try_to_unmap_flush(void) |
582 | { |
583 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
584 | |
585 | if (!tlb_ubc->flush_required) |
586 | return; |
587 | |
588 | arch_tlbbatch_flush(&tlb_ubc->arch); |
589 | tlb_ubc->flush_required = false; |
590 | tlb_ubc->writable = false; |
591 | } |
592 | |
593 | /* Flush iff there are potentially writable TLB entries that can race with IO */ |
594 | void try_to_unmap_flush_dirty(void) |
595 | { |
596 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
597 | |
598 | if (tlb_ubc->writable) |
599 | try_to_unmap_flush(); |
600 | } |
601 | |
602 | static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable) |
603 | { |
604 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
605 | |
606 | arch_tlbbatch_add_mm(&tlb_ubc->arch, mm); |
607 | tlb_ubc->flush_required = true; |
608 | |
609 | /* |
610 | * Ensure compiler does not re-order the setting of tlb_flush_batched |
611 | * before the PTE is cleared. |
612 | */ |
613 | barrier(); |
614 | mm->tlb_flush_batched = true; |
615 | |
616 | /* |
617 | * If the PTE was dirty then it's best to assume it's writable. The |
618 | * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush() |
619 | * before the page is queued for IO. |
620 | */ |
621 | if (writable) |
622 | tlb_ubc->writable = true; |
623 | } |
624 | |
625 | /* |
626 | * Returns true if the TLB flush should be deferred to the end of a batch of |
627 | * unmap operations to reduce IPIs. |
628 | */ |
629 | static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
630 | { |
631 | bool should_defer = false; |
632 | |
633 | if (!(flags & TTU_BATCH_FLUSH)) |
634 | return false; |
635 | |
636 | /* If remote CPUs need to be flushed then defer batch the flush */ |
637 | if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids) |
638 | should_defer = true; |
639 | put_cpu(); |
640 | |
641 | return should_defer; |
642 | } |
643 | |
644 | /* |
645 | * Reclaim unmaps pages under the PTL but do not flush the TLB prior to |
646 | * releasing the PTL if TLB flushes are batched. It's possible for a parallel |
647 | * operation such as mprotect or munmap to race between reclaim unmapping |
648 | * the page and flushing the page. If this race occurs, it potentially allows |
649 | * access to data via a stale TLB entry. Tracking all mm's that have TLB |
650 | * batching in flight would be expensive during reclaim so instead track |
651 | * whether TLB batching occurred in the past and if so then do a flush here |
652 | * if required. This will cost one additional flush per reclaim cycle paid |
653 | * by the first operation at risk such as mprotect and mumap. |
654 | * |
655 | * This must be called under the PTL so that an access to tlb_flush_batched |
656 | * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise |
657 | * via the PTL. |
658 | */ |
659 | void flush_tlb_batched_pending(struct mm_struct *mm) |
660 | { |
661 | if (mm->tlb_flush_batched) { |
662 | flush_tlb_mm(mm); |
663 | |
664 | /* |
665 | * Do not allow the compiler to re-order the clearing of |
666 | * tlb_flush_batched before the tlb is flushed. |
667 | */ |
668 | barrier(); |
669 | mm->tlb_flush_batched = false; |
670 | } |
671 | } |
672 | #else |
673 | static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable) |
674 | { |
675 | } |
676 | |
677 | static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
678 | { |
679 | return false; |
680 | } |
681 | #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */ |
682 | |
683 | /* |
684 | * At what user virtual address is page expected in vma? |
685 | * Caller should check the page is actually part of the vma. |
686 | */ |
687 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
688 | { |
689 | unsigned long address; |
690 | if (PageAnon(page)) { |
691 | struct anon_vma *page__anon_vma = page_anon_vma(page); |
692 | /* |
693 | * Note: swapoff's unuse_vma() is more efficient with this |
694 | * check, and needs it to match anon_vma when KSM is active. |
695 | */ |
696 | if (!vma->anon_vma || !page__anon_vma || |
697 | vma->anon_vma->root != page__anon_vma->root) |
698 | return -EFAULT; |
699 | } else if (page->mapping) { |
700 | if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping) |
701 | return -EFAULT; |
702 | } else |
703 | return -EFAULT; |
704 | address = __vma_address(page, vma); |
705 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) |
706 | return -EFAULT; |
707 | return address; |
708 | } |
709 | |
710 | pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) |
711 | { |
712 | pgd_t *pgd; |
713 | p4d_t *p4d; |
714 | pud_t *pud; |
715 | pmd_t *pmd = NULL; |
716 | pmd_t pmde; |
717 | |
718 | pgd = pgd_offset(mm, address); |
719 | if (!pgd_present(*pgd)) |
720 | goto out; |
721 | |
722 | p4d = p4d_offset(pgd, address); |
723 | if (!p4d_present(*p4d)) |
724 | goto out; |
725 | |
726 | pud = pud_offset(p4d, address); |
727 | if (!pud_present(*pud)) |
728 | goto out; |
729 | |
730 | pmd = pmd_offset(pud, address); |
731 | /* |
732 | * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() |
733 | * without holding anon_vma lock for write. So when looking for a |
734 | * genuine pmde (in which to find pte), test present and !THP together. |
735 | */ |
736 | pmde = *pmd; |
737 | barrier(); |
738 | if (!pmd_present(pmde) || pmd_trans_huge(pmde)) |
739 | pmd = NULL; |
740 | out: |
741 | return pmd; |
742 | } |
743 | |
744 | struct page_referenced_arg { |
745 | int mapcount; |
746 | int referenced; |
747 | unsigned long vm_flags; |
748 | struct mem_cgroup *memcg; |
749 | }; |
750 | /* |
751 | * arg: page_referenced_arg will be passed |
752 | */ |
753 | static bool page_referenced_one(struct page *page, struct vm_area_struct *vma, |
754 | unsigned long address, void *arg) |
755 | { |
756 | struct page_referenced_arg *pra = arg; |
757 | struct page_vma_mapped_walk pvmw = { |
758 | .page = page, |
759 | .vma = vma, |
760 | .address = address, |
761 | }; |
762 | int referenced = 0; |
763 | |
764 | while (page_vma_mapped_walk(&pvmw)) { |
765 | address = pvmw.address; |
766 | |
767 | if (vma->vm_flags & VM_LOCKED) { |
768 | page_vma_mapped_walk_done(&pvmw); |
769 | pra->vm_flags |= VM_LOCKED; |
770 | return false; /* To break the loop */ |
771 | } |
772 | |
773 | if (pvmw.pte) { |
774 | if (ptep_clear_flush_young_notify(vma, address, |
775 | pvmw.pte)) { |
776 | /* |
777 | * Don't treat a reference through |
778 | * a sequentially read mapping as such. |
779 | * If the page has been used in another mapping, |
780 | * we will catch it; if this other mapping is |
781 | * already gone, the unmap path will have set |
782 | * PG_referenced or activated the page. |
783 | */ |
784 | if (likely(!(vma->vm_flags & VM_SEQ_READ))) |
785 | referenced++; |
786 | } |
787 | } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
788 | if (pmdp_clear_flush_young_notify(vma, address, |
789 | pvmw.pmd)) |
790 | referenced++; |
791 | } else { |
792 | /* unexpected pmd-mapped page? */ |
793 | WARN_ON_ONCE(1); |
794 | } |
795 | |
796 | pra->mapcount--; |
797 | } |
798 | |
799 | if (referenced) |
800 | clear_page_idle(page); |
801 | if (test_and_clear_page_young(page)) |
802 | referenced++; |
803 | |
804 | if (referenced) { |
805 | pra->referenced++; |
806 | pra->vm_flags |= vma->vm_flags; |
807 | } |
808 | |
809 | if (!pra->mapcount) |
810 | return false; /* To break the loop */ |
811 | |
812 | return true; |
813 | } |
814 | |
815 | static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg) |
816 | { |
817 | struct page_referenced_arg *pra = arg; |
818 | struct mem_cgroup *memcg = pra->memcg; |
819 | |
820 | if (!mm_match_cgroup(vma->vm_mm, memcg)) |
821 | return true; |
822 | |
823 | return false; |
824 | } |
825 | |
826 | /** |
827 | * page_referenced - test if the page was referenced |
828 | * @page: the page to test |
829 | * @is_locked: caller holds lock on the page |
830 | * @memcg: target memory cgroup |
831 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
832 | * |
833 | * Quick test_and_clear_referenced for all mappings to a page, |
834 | * returns the number of ptes which referenced the page. |
835 | */ |
836 | int page_referenced(struct page *page, |
837 | int is_locked, |
838 | struct mem_cgroup *memcg, |
839 | unsigned long *vm_flags) |
840 | { |
841 | int we_locked = 0; |
842 | struct page_referenced_arg pra = { |
843 | .mapcount = total_mapcount(page), |
844 | .memcg = memcg, |
845 | }; |
846 | struct rmap_walk_control rwc = { |
847 | .rmap_one = page_referenced_one, |
848 | .arg = (void *)&pra, |
849 | .anon_lock = page_lock_anon_vma_read, |
850 | }; |
851 | |
852 | *vm_flags = 0; |
853 | if (!page_mapped(page)) |
854 | return 0; |
855 | |
856 | if (!page_rmapping(page)) |
857 | return 0; |
858 | |
859 | if (!is_locked && (!PageAnon(page) || PageKsm(page))) { |
860 | we_locked = trylock_page(page); |
861 | if (!we_locked) |
862 | return 1; |
863 | } |
864 | |
865 | /* |
866 | * If we are reclaiming on behalf of a cgroup, skip |
867 | * counting on behalf of references from different |
868 | * cgroups |
869 | */ |
870 | if (memcg) { |
871 | rwc.invalid_vma = invalid_page_referenced_vma; |
872 | } |
873 | |
874 | rmap_walk(page, &rwc); |
875 | *vm_flags = pra.vm_flags; |
876 | |
877 | if (we_locked) |
878 | unlock_page(page); |
879 | |
880 | return pra.referenced; |
881 | } |
882 | |
883 | static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
884 | unsigned long address, void *arg) |
885 | { |
886 | struct page_vma_mapped_walk pvmw = { |
887 | .page = page, |
888 | .vma = vma, |
889 | .address = address, |
890 | .flags = PVMW_SYNC, |
891 | }; |
892 | struct mmu_notifier_range range; |
893 | int *cleaned = arg; |
894 | |
895 | /* |
896 | * We have to assume the worse case ie pmd for invalidation. Note that |
897 | * the page can not be free from this function. |
898 | */ |
899 | mmu_notifier_range_init(&range, vma->vm_mm, address, |
900 | min(vma->vm_end, address + |
901 | (PAGE_SIZE << compound_order(page)))); |
902 | mmu_notifier_invalidate_range_start(&range); |
903 | |
904 | while (page_vma_mapped_walk(&pvmw)) { |
905 | unsigned long cstart; |
906 | int ret = 0; |
907 | |
908 | cstart = address = pvmw.address; |
909 | if (pvmw.pte) { |
910 | pte_t entry; |
911 | pte_t *pte = pvmw.pte; |
912 | |
913 | if (!pte_dirty(*pte) && !pte_write(*pte)) |
914 | continue; |
915 | |
916 | flush_cache_page(vma, address, pte_pfn(*pte)); |
917 | entry = ptep_clear_flush(vma, address, pte); |
918 | entry = pte_wrprotect(entry); |
919 | entry = pte_mkclean(entry); |
920 | set_pte_at(vma->vm_mm, address, pte, entry); |
921 | ret = 1; |
922 | } else { |
923 | #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE |
924 | pmd_t *pmd = pvmw.pmd; |
925 | pmd_t entry; |
926 | |
927 | if (!pmd_dirty(*pmd) && !pmd_write(*pmd)) |
928 | continue; |
929 | |
930 | flush_cache_page(vma, address, page_to_pfn(page)); |
931 | entry = pmdp_huge_clear_flush(vma, address, pmd); |
932 | entry = pmd_wrprotect(entry); |
933 | entry = pmd_mkclean(entry); |
934 | set_pmd_at(vma->vm_mm, address, pmd, entry); |
935 | cstart &= PMD_MASK; |
936 | ret = 1; |
937 | #else |
938 | /* unexpected pmd-mapped page? */ |
939 | WARN_ON_ONCE(1); |
940 | #endif |
941 | } |
942 | |
943 | /* |
944 | * No need to call mmu_notifier_invalidate_range() as we are |
945 | * downgrading page table protection not changing it to point |
946 | * to a new page. |
947 | * |
948 | * See Documentation/vm/mmu_notifier.rst |
949 | */ |
950 | if (ret) |
951 | (*cleaned)++; |
952 | } |
953 | |
954 | mmu_notifier_invalidate_range_end(&range); |
955 | |
956 | return true; |
957 | } |
958 | |
959 | static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg) |
960 | { |
961 | if (vma->vm_flags & VM_SHARED) |
962 | return false; |
963 | |
964 | return true; |
965 | } |
966 | |
967 | int page_mkclean(struct page *page) |
968 | { |
969 | int cleaned = 0; |
970 | struct address_space *mapping; |
971 | struct rmap_walk_control rwc = { |
972 | .arg = (void *)&cleaned, |
973 | .rmap_one = page_mkclean_one, |
974 | .invalid_vma = invalid_mkclean_vma, |
975 | }; |
976 | |
977 | BUG_ON(!PageLocked(page)); |
978 | |
979 | if (!page_mapped(page)) |
980 | return 0; |
981 | |
982 | mapping = page_mapping(page); |
983 | if (!mapping) |
984 | return 0; |
985 | |
986 | rmap_walk(page, &rwc); |
987 | |
988 | return cleaned; |
989 | } |
990 | EXPORT_SYMBOL_GPL(page_mkclean); |
991 | |
992 | /** |
993 | * page_move_anon_rmap - move a page to our anon_vma |
994 | * @page: the page to move to our anon_vma |
995 | * @vma: the vma the page belongs to |
996 | * |
997 | * When a page belongs exclusively to one process after a COW event, |
998 | * that page can be moved into the anon_vma that belongs to just that |
999 | * process, so the rmap code will not search the parent or sibling |
1000 | * processes. |
1001 | */ |
1002 | void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma) |
1003 | { |
1004 | struct anon_vma *anon_vma = vma->anon_vma; |
1005 | |
1006 | page = compound_head(page); |
1007 | |
1008 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1009 | VM_BUG_ON_VMA(!anon_vma, vma); |
1010 | |
1011 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1012 | /* |
1013 | * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written |
1014 | * simultaneously, so a concurrent reader (eg page_referenced()'s |
1015 | * PageAnon()) will not see one without the other. |
1016 | */ |
1017 | WRITE_ONCE(page->mapping, (struct address_space *) anon_vma); |
1018 | } |
1019 | |
1020 | /** |
1021 | * __page_set_anon_rmap - set up new anonymous rmap |
1022 | * @page: Page or Hugepage to add to rmap |
1023 | * @vma: VM area to add page to. |
1024 | * @address: User virtual address of the mapping |
1025 | * @exclusive: the page is exclusively owned by the current process |
1026 | */ |
1027 | static void __page_set_anon_rmap(struct page *page, |
1028 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
1029 | { |
1030 | struct anon_vma *anon_vma = vma->anon_vma; |
1031 | |
1032 | BUG_ON(!anon_vma); |
1033 | |
1034 | if (PageAnon(page)) |
1035 | return; |
1036 | |
1037 | /* |
1038 | * If the page isn't exclusively mapped into this vma, |
1039 | * we must use the _oldest_ possible anon_vma for the |
1040 | * page mapping! |
1041 | */ |
1042 | if (!exclusive) |
1043 | anon_vma = anon_vma->root; |
1044 | |
1045 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1046 | page->mapping = (struct address_space *) anon_vma; |
1047 | page->index = linear_page_index(vma, address); |
1048 | } |
1049 | |
1050 | /** |
1051 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
1052 | * @page: the page to add the mapping to |
1053 | * @vma: the vm area in which the mapping is added |
1054 | * @address: the user virtual address mapped |
1055 | */ |
1056 | static void __page_check_anon_rmap(struct page *page, |
1057 | struct vm_area_struct *vma, unsigned long address) |
1058 | { |
1059 | #ifdef CONFIG_DEBUG_VM |
1060 | /* |
1061 | * The page's anon-rmap details (mapping and index) are guaranteed to |
1062 | * be set up correctly at this point. |
1063 | * |
1064 | * We have exclusion against page_add_anon_rmap because the caller |
1065 | * always holds the page locked, except if called from page_dup_rmap, |
1066 | * in which case the page is already known to be setup. |
1067 | * |
1068 | * We have exclusion against page_add_new_anon_rmap because those pages |
1069 | * are initially only visible via the pagetables, and the pte is locked |
1070 | * over the call to page_add_new_anon_rmap. |
1071 | */ |
1072 | BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root); |
1073 | BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address)); |
1074 | #endif |
1075 | } |
1076 | |
1077 | /** |
1078 | * page_add_anon_rmap - add pte mapping to an anonymous page |
1079 | * @page: the page to add the mapping to |
1080 | * @vma: the vm area in which the mapping is added |
1081 | * @address: the user virtual address mapped |
1082 | * @compound: charge the page as compound or small page |
1083 | * |
1084 | * The caller needs to hold the pte lock, and the page must be locked in |
1085 | * the anon_vma case: to serialize mapping,index checking after setting, |
1086 | * and to ensure that PageAnon is not being upgraded racily to PageKsm |
1087 | * (but PageKsm is never downgraded to PageAnon). |
1088 | */ |
1089 | void page_add_anon_rmap(struct page *page, |
1090 | struct vm_area_struct *vma, unsigned long address, bool compound) |
1091 | { |
1092 | do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0); |
1093 | } |
1094 | |
1095 | /* |
1096 | * Special version of the above for do_swap_page, which often runs |
1097 | * into pages that are exclusively owned by the current process. |
1098 | * Everybody else should continue to use page_add_anon_rmap above. |
1099 | */ |
1100 | void do_page_add_anon_rmap(struct page *page, |
1101 | struct vm_area_struct *vma, unsigned long address, int flags) |
1102 | { |
1103 | bool compound = flags & RMAP_COMPOUND; |
1104 | bool first; |
1105 | |
1106 | if (compound) { |
1107 | atomic_t *mapcount; |
1108 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1109 | VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
1110 | mapcount = compound_mapcount_ptr(page); |
1111 | first = atomic_inc_and_test(mapcount); |
1112 | } else { |
1113 | first = atomic_inc_and_test(&page->_mapcount); |
1114 | } |
1115 | |
1116 | if (first) { |
1117 | int nr = compound ? hpage_nr_pages(page) : 1; |
1118 | /* |
1119 | * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
1120 | * these counters are not modified in interrupt context, and |
1121 | * pte lock(a spinlock) is held, which implies preemption |
1122 | * disabled. |
1123 | */ |
1124 | if (compound) |
1125 | __inc_node_page_state(page, NR_ANON_THPS); |
1126 | __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr); |
1127 | } |
1128 | if (unlikely(PageKsm(page))) |
1129 | return; |
1130 | |
1131 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1132 | |
1133 | /* address might be in next vma when migration races vma_adjust */ |
1134 | if (first) |
1135 | __page_set_anon_rmap(page, vma, address, |
1136 | flags & RMAP_EXCLUSIVE); |
1137 | else |
1138 | __page_check_anon_rmap(page, vma, address); |
1139 | } |
1140 | |
1141 | /** |
1142 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
1143 | * @page: the page to add the mapping to |
1144 | * @vma: the vm area in which the mapping is added |
1145 | * @address: the user virtual address mapped |
1146 | * @compound: charge the page as compound or small page |
1147 | * |
1148 | * Same as page_add_anon_rmap but must only be called on *new* pages. |
1149 | * This means the inc-and-test can be bypassed. |
1150 | * Page does not have to be locked. |
1151 | */ |
1152 | void page_add_new_anon_rmap(struct page *page, |
1153 | struct vm_area_struct *vma, unsigned long address, bool compound) |
1154 | { |
1155 | int nr = compound ? hpage_nr_pages(page) : 1; |
1156 | |
1157 | VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); |
1158 | __SetPageSwapBacked(page); |
1159 | if (compound) { |
1160 | VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
1161 | /* increment count (starts at -1) */ |
1162 | atomic_set(compound_mapcount_ptr(page), 0); |
1163 | __inc_node_page_state(page, NR_ANON_THPS); |
1164 | } else { |
1165 | /* Anon THP always mapped first with PMD */ |
1166 | VM_BUG_ON_PAGE(PageTransCompound(page), page); |
1167 | /* increment count (starts at -1) */ |
1168 | atomic_set(&page->_mapcount, 0); |
1169 | } |
1170 | __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr); |
1171 | __page_set_anon_rmap(page, vma, address, 1); |
1172 | } |
1173 | |
1174 | /** |
1175 | * page_add_file_rmap - add pte mapping to a file page |
1176 | * @page: the page to add the mapping to |
1177 | * @compound: charge the page as compound or small page |
1178 | * |
1179 | * The caller needs to hold the pte lock. |
1180 | */ |
1181 | void page_add_file_rmap(struct page *page, bool compound) |
1182 | { |
1183 | int i, nr = 1; |
1184 | |
1185 | VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); |
1186 | lock_page_memcg(page); |
1187 | if (compound && PageTransHuge(page)) { |
1188 | for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
1189 | if (atomic_inc_and_test(&page[i]._mapcount)) |
1190 | nr++; |
1191 | } |
1192 | if (!atomic_inc_and_test(compound_mapcount_ptr(page))) |
1193 | goto out; |
1194 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
1195 | __inc_node_page_state(page, NR_SHMEM_PMDMAPPED); |
1196 | } else { |
1197 | if (PageTransCompound(page) && page_mapping(page)) { |
1198 | VM_WARN_ON_ONCE(!PageLocked(page)); |
1199 | |
1200 | SetPageDoubleMap(compound_head(page)); |
1201 | if (PageMlocked(page)) |
1202 | clear_page_mlock(compound_head(page)); |
1203 | } |
1204 | if (!atomic_inc_and_test(&page->_mapcount)) |
1205 | goto out; |
1206 | } |
1207 | __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr); |
1208 | out: |
1209 | unlock_page_memcg(page); |
1210 | } |
1211 | |
1212 | static void page_remove_file_rmap(struct page *page, bool compound) |
1213 | { |
1214 | int i, nr = 1; |
1215 | |
1216 | VM_BUG_ON_PAGE(compound && !PageHead(page), page); |
1217 | lock_page_memcg(page); |
1218 | |
1219 | /* Hugepages are not counted in NR_FILE_MAPPED for now. */ |
1220 | if (unlikely(PageHuge(page))) { |
1221 | /* hugetlb pages are always mapped with pmds */ |
1222 | atomic_dec(compound_mapcount_ptr(page)); |
1223 | goto out; |
1224 | } |
1225 | |
1226 | /* page still mapped by someone else? */ |
1227 | if (compound && PageTransHuge(page)) { |
1228 | for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
1229 | if (atomic_add_negative(-1, &page[i]._mapcount)) |
1230 | nr++; |
1231 | } |
1232 | if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
1233 | goto out; |
1234 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
1235 | __dec_node_page_state(page, NR_SHMEM_PMDMAPPED); |
1236 | } else { |
1237 | if (!atomic_add_negative(-1, &page->_mapcount)) |
1238 | goto out; |
1239 | } |
1240 | |
1241 | /* |
1242 | * We use the irq-unsafe __{inc|mod}_lruvec_page_state because |
1243 | * these counters are not modified in interrupt context, and |
1244 | * pte lock(a spinlock) is held, which implies preemption disabled. |
1245 | */ |
1246 | __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr); |
1247 | |
1248 | if (unlikely(PageMlocked(page))) |
1249 | clear_page_mlock(page); |
1250 | out: |
1251 | unlock_page_memcg(page); |
1252 | } |
1253 | |
1254 | static void page_remove_anon_compound_rmap(struct page *page) |
1255 | { |
1256 | int i, nr; |
1257 | |
1258 | if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
1259 | return; |
1260 | |
1261 | /* Hugepages are not counted in NR_ANON_PAGES for now. */ |
1262 | if (unlikely(PageHuge(page))) |
1263 | return; |
1264 | |
1265 | if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) |
1266 | return; |
1267 | |
1268 | __dec_node_page_state(page, NR_ANON_THPS); |
1269 | |
1270 | if (TestClearPageDoubleMap(page)) { |
1271 | /* |
1272 | * Subpages can be mapped with PTEs too. Check how many of |
1273 | * themi are still mapped. |
1274 | */ |
1275 | for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
1276 | if (atomic_add_negative(-1, &page[i]._mapcount)) |
1277 | nr++; |
1278 | } |
1279 | } else { |
1280 | nr = HPAGE_PMD_NR; |
1281 | } |
1282 | |
1283 | if (unlikely(PageMlocked(page))) |
1284 | clear_page_mlock(page); |
1285 | |
1286 | if (nr) { |
1287 | __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr); |
1288 | deferred_split_huge_page(page); |
1289 | } |
1290 | } |
1291 | |
1292 | /** |
1293 | * page_remove_rmap - take down pte mapping from a page |
1294 | * @page: page to remove mapping from |
1295 | * @compound: uncharge the page as compound or small page |
1296 | * |
1297 | * The caller needs to hold the pte lock. |
1298 | */ |
1299 | void page_remove_rmap(struct page *page, bool compound) |
1300 | { |
1301 | if (!PageAnon(page)) |
1302 | return page_remove_file_rmap(page, compound); |
1303 | |
1304 | if (compound) |
1305 | return page_remove_anon_compound_rmap(page); |
1306 | |
1307 | /* page still mapped by someone else? */ |
1308 | if (!atomic_add_negative(-1, &page->_mapcount)) |
1309 | return; |
1310 | |
1311 | /* |
1312 | * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
1313 | * these counters are not modified in interrupt context, and |
1314 | * pte lock(a spinlock) is held, which implies preemption disabled. |
1315 | */ |
1316 | __dec_node_page_state(page, NR_ANON_MAPPED); |
1317 | |
1318 | if (unlikely(PageMlocked(page))) |
1319 | clear_page_mlock(page); |
1320 | |
1321 | if (PageTransCompound(page)) |
1322 | deferred_split_huge_page(compound_head(page)); |
1323 | |
1324 | /* |
1325 | * It would be tidy to reset the PageAnon mapping here, |
1326 | * but that might overwrite a racing page_add_anon_rmap |
1327 | * which increments mapcount after us but sets mapping |
1328 | * before us: so leave the reset to free_unref_page, |
1329 | * and remember that it's only reliable while mapped. |
1330 | * Leaving it set also helps swapoff to reinstate ptes |
1331 | * faster for those pages still in swapcache. |
1332 | */ |
1333 | } |
1334 | |
1335 | /* |
1336 | * @arg: enum ttu_flags will be passed to this argument |
1337 | */ |
1338 | static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
1339 | unsigned long address, void *arg) |
1340 | { |
1341 | struct mm_struct *mm = vma->vm_mm; |
1342 | struct page_vma_mapped_walk pvmw = { |
1343 | .page = page, |
1344 | .vma = vma, |
1345 | .address = address, |
1346 | }; |
1347 | pte_t pteval; |
1348 | struct page *subpage; |
1349 | bool ret = true; |
1350 | struct mmu_notifier_range range; |
1351 | enum ttu_flags flags = (enum ttu_flags)arg; |
1352 | |
1353 | /* munlock has nothing to gain from examining un-locked vmas */ |
1354 | if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) |
1355 | return true; |
1356 | |
1357 | if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) && |
1358 | is_zone_device_page(page) && !is_device_private_page(page)) |
1359 | return true; |
1360 | |
1361 | if (flags & TTU_SPLIT_HUGE_PMD) { |
1362 | split_huge_pmd_address(vma, address, |
1363 | flags & TTU_SPLIT_FREEZE, page); |
1364 | } |
1365 | |
1366 | /* |
1367 | * For THP, we have to assume the worse case ie pmd for invalidation. |
1368 | * For hugetlb, it could be much worse if we need to do pud |
1369 | * invalidation in the case of pmd sharing. |
1370 | * |
1371 | * Note that the page can not be free in this function as call of |
1372 | * try_to_unmap() must hold a reference on the page. |
1373 | */ |
1374 | mmu_notifier_range_init(&range, vma->vm_mm, address, |
1375 | min(vma->vm_end, address + |
1376 | (PAGE_SIZE << compound_order(page)))); |
1377 | if (PageHuge(page)) { |
1378 | /* |
1379 | * If sharing is possible, start and end will be adjusted |
1380 | * accordingly. |
1381 | */ |
1382 | adjust_range_if_pmd_sharing_possible(vma, &range.start, |
1383 | &range.end); |
1384 | } |
1385 | mmu_notifier_invalidate_range_start(&range); |
1386 | |
1387 | while (page_vma_mapped_walk(&pvmw)) { |
1388 | #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
1389 | /* PMD-mapped THP migration entry */ |
1390 | if (!pvmw.pte && (flags & TTU_MIGRATION)) { |
1391 | VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); |
1392 | |
1393 | set_pmd_migration_entry(&pvmw, page); |
1394 | continue; |
1395 | } |
1396 | #endif |
1397 | |
1398 | /* |
1399 | * If the page is mlock()d, we cannot swap it out. |
1400 | * If it's recently referenced (perhaps page_referenced |
1401 | * skipped over this mm) then we should reactivate it. |
1402 | */ |
1403 | if (!(flags & TTU_IGNORE_MLOCK)) { |
1404 | if (vma->vm_flags & VM_LOCKED) { |
1405 | /* PTE-mapped THP are never mlocked */ |
1406 | if (!PageTransCompound(page)) { |
1407 | /* |
1408 | * Holding pte lock, we do *not* need |
1409 | * mmap_sem here |
1410 | */ |
1411 | mlock_vma_page(page); |
1412 | } |
1413 | ret = false; |
1414 | page_vma_mapped_walk_done(&pvmw); |
1415 | break; |
1416 | } |
1417 | if (flags & TTU_MUNLOCK) |
1418 | continue; |
1419 | } |
1420 | |
1421 | /* Unexpected PMD-mapped THP? */ |
1422 | VM_BUG_ON_PAGE(!pvmw.pte, page); |
1423 | |
1424 | subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte); |
1425 | address = pvmw.address; |
1426 | |
1427 | if (PageHuge(page)) { |
1428 | if (huge_pmd_unshare(mm, &address, pvmw.pte)) { |
1429 | /* |
1430 | * huge_pmd_unshare unmapped an entire PMD |
1431 | * page. There is no way of knowing exactly |
1432 | * which PMDs may be cached for this mm, so |
1433 | * we must flush them all. start/end were |
1434 | * already adjusted above to cover this range. |
1435 | */ |
1436 | flush_cache_range(vma, range.start, range.end); |
1437 | flush_tlb_range(vma, range.start, range.end); |
1438 | mmu_notifier_invalidate_range(mm, range.start, |
1439 | range.end); |
1440 | |
1441 | /* |
1442 | * The ref count of the PMD page was dropped |
1443 | * which is part of the way map counting |
1444 | * is done for shared PMDs. Return 'true' |
1445 | * here. When there is no other sharing, |
1446 | * huge_pmd_unshare returns false and we will |
1447 | * unmap the actual page and drop map count |
1448 | * to zero. |
1449 | */ |
1450 | page_vma_mapped_walk_done(&pvmw); |
1451 | break; |
1452 | } |
1453 | } |
1454 | |
1455 | if (IS_ENABLED(CONFIG_MIGRATION) && |
1456 | (flags & TTU_MIGRATION) && |
1457 | is_zone_device_page(page)) { |
1458 | swp_entry_t entry; |
1459 | pte_t swp_pte; |
1460 | |
1461 | pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.pte); |
1462 | |
1463 | /* |
1464 | * Store the pfn of the page in a special migration |
1465 | * pte. do_swap_page() will wait until the migration |
1466 | * pte is removed and then restart fault handling. |
1467 | */ |
1468 | entry = make_migration_entry(page, 0); |
1469 | swp_pte = swp_entry_to_pte(entry); |
1470 | if (pte_soft_dirty(pteval)) |
1471 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
1472 | set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte); |
1473 | /* |
1474 | * No need to invalidate here it will synchronize on |
1475 | * against the special swap migration pte. |
1476 | */ |
1477 | goto discard; |
1478 | } |
1479 | |
1480 | if (!(flags & TTU_IGNORE_ACCESS)) { |
1481 | if (ptep_clear_flush_young_notify(vma, address, |
1482 | pvmw.pte)) { |
1483 | ret = false; |
1484 | page_vma_mapped_walk_done(&pvmw); |
1485 | break; |
1486 | } |
1487 | } |
1488 | |
1489 | /* Nuke the page table entry. */ |
1490 | flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); |
1491 | if (should_defer_flush(mm, flags)) { |
1492 | /* |
1493 | * We clear the PTE but do not flush so potentially |
1494 | * a remote CPU could still be writing to the page. |
1495 | * If the entry was previously clean then the |
1496 | * architecture must guarantee that a clear->dirty |
1497 | * transition on a cached TLB entry is written through |
1498 | * and traps if the PTE is unmapped. |
1499 | */ |
1500 | pteval = ptep_get_and_clear(mm, address, pvmw.pte); |
1501 | |
1502 | set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); |
1503 | } else { |
1504 | pteval = ptep_clear_flush(vma, address, pvmw.pte); |
1505 | } |
1506 | |
1507 | /* Move the dirty bit to the page. Now the pte is gone. */ |
1508 | if (pte_dirty(pteval)) |
1509 | set_page_dirty(page); |
1510 | |
1511 | /* Update high watermark before we lower rss */ |
1512 | update_hiwater_rss(mm); |
1513 | |
1514 | if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
1515 | pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); |
1516 | if (PageHuge(page)) { |
1517 | int nr = 1 << compound_order(page); |
1518 | hugetlb_count_sub(nr, mm); |
1519 | set_huge_swap_pte_at(mm, address, |
1520 | pvmw.pte, pteval, |
1521 | vma_mmu_pagesize(vma)); |
1522 | } else { |
1523 | dec_mm_counter(mm, mm_counter(page)); |
1524 | set_pte_at(mm, address, pvmw.pte, pteval); |
1525 | } |
1526 | |
1527 | } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { |
1528 | /* |
1529 | * The guest indicated that the page content is of no |
1530 | * interest anymore. Simply discard the pte, vmscan |
1531 | * will take care of the rest. |
1532 | * A future reference will then fault in a new zero |
1533 | * page. When userfaultfd is active, we must not drop |
1534 | * this page though, as its main user (postcopy |
1535 | * migration) will not expect userfaults on already |
1536 | * copied pages. |
1537 | */ |
1538 | dec_mm_counter(mm, mm_counter(page)); |
1539 | /* We have to invalidate as we cleared the pte */ |
1540 | mmu_notifier_invalidate_range(mm, address, |
1541 | address + PAGE_SIZE); |
1542 | } else if (IS_ENABLED(CONFIG_MIGRATION) && |
1543 | (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) { |
1544 | swp_entry_t entry; |
1545 | pte_t swp_pte; |
1546 | |
1547 | if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
1548 | set_pte_at(mm, address, pvmw.pte, pteval); |
1549 | ret = false; |
1550 | page_vma_mapped_walk_done(&pvmw); |
1551 | break; |
1552 | } |
1553 | |
1554 | /* |
1555 | * Store the pfn of the page in a special migration |
1556 | * pte. do_swap_page() will wait until the migration |
1557 | * pte is removed and then restart fault handling. |
1558 | */ |
1559 | entry = make_migration_entry(subpage, |
1560 | pte_write(pteval)); |
1561 | swp_pte = swp_entry_to_pte(entry); |
1562 | if (pte_soft_dirty(pteval)) |
1563 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
1564 | set_pte_at(mm, address, pvmw.pte, swp_pte); |
1565 | /* |
1566 | * No need to invalidate here it will synchronize on |
1567 | * against the special swap migration pte. |
1568 | */ |
1569 | } else if (PageAnon(page)) { |
1570 | swp_entry_t entry = { .val = page_private(subpage) }; |
1571 | pte_t swp_pte; |
1572 | /* |
1573 | * Store the swap location in the pte. |
1574 | * See handle_pte_fault() ... |
1575 | */ |
1576 | if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) { |
1577 | WARN_ON_ONCE(1); |
1578 | ret = false; |
1579 | /* We have to invalidate as we cleared the pte */ |
1580 | mmu_notifier_invalidate_range(mm, address, |
1581 | address + PAGE_SIZE); |
1582 | page_vma_mapped_walk_done(&pvmw); |
1583 | break; |
1584 | } |
1585 | |
1586 | /* MADV_FREE page check */ |
1587 | if (!PageSwapBacked(page)) { |
1588 | if (!PageDirty(page)) { |
1589 | /* Invalidate as we cleared the pte */ |
1590 | mmu_notifier_invalidate_range(mm, |
1591 | address, address + PAGE_SIZE); |
1592 | dec_mm_counter(mm, MM_ANONPAGES); |
1593 | goto discard; |
1594 | } |
1595 | |
1596 | /* |
1597 | * If the page was redirtied, it cannot be |
1598 | * discarded. Remap the page to page table. |
1599 | */ |
1600 | set_pte_at(mm, address, pvmw.pte, pteval); |
1601 | SetPageSwapBacked(page); |
1602 | ret = false; |
1603 | page_vma_mapped_walk_done(&pvmw); |
1604 | break; |
1605 | } |
1606 | |
1607 | if (swap_duplicate(entry) < 0) { |
1608 | set_pte_at(mm, address, pvmw.pte, pteval); |
1609 | ret = false; |
1610 | page_vma_mapped_walk_done(&pvmw); |
1611 | break; |
1612 | } |
1613 | if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
1614 | set_pte_at(mm, address, pvmw.pte, pteval); |
1615 | ret = false; |
1616 | page_vma_mapped_walk_done(&pvmw); |
1617 | break; |
1618 | } |
1619 | if (list_empty(&mm->mmlist)) { |
1620 | spin_lock(&mmlist_lock); |
1621 | if (list_empty(&mm->mmlist)) |
1622 | list_add(&mm->mmlist, &init_mm.mmlist); |
1623 | spin_unlock(&mmlist_lock); |
1624 | } |
1625 | dec_mm_counter(mm, MM_ANONPAGES); |
1626 | inc_mm_counter(mm, MM_SWAPENTS); |
1627 | swp_pte = swp_entry_to_pte(entry); |
1628 | if (pte_soft_dirty(pteval)) |
1629 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
1630 | set_pte_at(mm, address, pvmw.pte, swp_pte); |
1631 | /* Invalidate as we cleared the pte */ |
1632 | mmu_notifier_invalidate_range(mm, address, |
1633 | address + PAGE_SIZE); |
1634 | } else { |
1635 | /* |
1636 | * This is a locked file-backed page, thus it cannot |
1637 | * be removed from the page cache and replaced by a new |
1638 | * page before mmu_notifier_invalidate_range_end, so no |
1639 | * concurrent thread might update its page table to |
1640 | * point at new page while a device still is using this |
1641 | * page. |
1642 | * |
1643 | * See Documentation/vm/mmu_notifier.rst |
1644 | */ |
1645 | dec_mm_counter(mm, mm_counter_file(page)); |
1646 | } |
1647 | discard: |
1648 | /* |
1649 | * No need to call mmu_notifier_invalidate_range() it has be |
1650 | * done above for all cases requiring it to happen under page |
1651 | * table lock before mmu_notifier_invalidate_range_end() |
1652 | * |
1653 | * See Documentation/vm/mmu_notifier.rst |
1654 | */ |
1655 | page_remove_rmap(subpage, PageHuge(page)); |
1656 | put_page(page); |
1657 | } |
1658 | |
1659 | mmu_notifier_invalidate_range_end(&range); |
1660 | |
1661 | return ret; |
1662 | } |
1663 | |
1664 | bool is_vma_temporary_stack(struct vm_area_struct *vma) |
1665 | { |
1666 | int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP); |
1667 | |
1668 | if (!maybe_stack) |
1669 | return false; |
1670 | |
1671 | if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) == |
1672 | VM_STACK_INCOMPLETE_SETUP) |
1673 | return true; |
1674 | |
1675 | return false; |
1676 | } |
1677 | |
1678 | static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg) |
1679 | { |
1680 | return is_vma_temporary_stack(vma); |
1681 | } |
1682 | |
1683 | static int page_mapcount_is_zero(struct page *page) |
1684 | { |
1685 | return !total_mapcount(page); |
1686 | } |
1687 | |
1688 | /** |
1689 | * try_to_unmap - try to remove all page table mappings to a page |
1690 | * @page: the page to get unmapped |
1691 | * @flags: action and flags |
1692 | * |
1693 | * Tries to remove all the page table entries which are mapping this |
1694 | * page, used in the pageout path. Caller must hold the page lock. |
1695 | * |
1696 | * If unmap is successful, return true. Otherwise, false. |
1697 | */ |
1698 | bool try_to_unmap(struct page *page, enum ttu_flags flags) |
1699 | { |
1700 | struct rmap_walk_control rwc = { |
1701 | .rmap_one = try_to_unmap_one, |
1702 | .arg = (void *)flags, |
1703 | .done = page_mapcount_is_zero, |
1704 | .anon_lock = page_lock_anon_vma_read, |
1705 | }; |
1706 | |
1707 | /* |
1708 | * During exec, a temporary VMA is setup and later moved. |
1709 | * The VMA is moved under the anon_vma lock but not the |
1710 | * page tables leading to a race where migration cannot |
1711 | * find the migration ptes. Rather than increasing the |
1712 | * locking requirements of exec(), migration skips |
1713 | * temporary VMAs until after exec() completes. |
1714 | */ |
1715 | if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE)) |
1716 | && !PageKsm(page) && PageAnon(page)) |
1717 | rwc.invalid_vma = invalid_migration_vma; |
1718 | |
1719 | if (flags & TTU_RMAP_LOCKED) |
1720 | rmap_walk_locked(page, &rwc); |
1721 | else |
1722 | rmap_walk(page, &rwc); |
1723 | |
1724 | return !page_mapcount(page) ? true : false; |
1725 | } |
1726 | |
1727 | static int page_not_mapped(struct page *page) |
1728 | { |
1729 | return !page_mapped(page); |
1730 | }; |
1731 | |
1732 | /** |
1733 | * try_to_munlock - try to munlock a page |
1734 | * @page: the page to be munlocked |
1735 | * |
1736 | * Called from munlock code. Checks all of the VMAs mapping the page |
1737 | * to make sure nobody else has this page mlocked. The page will be |
1738 | * returned with PG_mlocked cleared if no other vmas have it mlocked. |
1739 | */ |
1740 | |
1741 | void try_to_munlock(struct page *page) |
1742 | { |
1743 | struct rmap_walk_control rwc = { |
1744 | .rmap_one = try_to_unmap_one, |
1745 | .arg = (void *)TTU_MUNLOCK, |
1746 | .done = page_not_mapped, |
1747 | .anon_lock = page_lock_anon_vma_read, |
1748 | |
1749 | }; |
1750 | |
1751 | VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); |
1752 | VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page); |
1753 | |
1754 | rmap_walk(page, &rwc); |
1755 | } |
1756 | |
1757 | void __put_anon_vma(struct anon_vma *anon_vma) |
1758 | { |
1759 | struct anon_vma *root = anon_vma->root; |
1760 | |
1761 | anon_vma_free(anon_vma); |
1762 | if (root != anon_vma && atomic_dec_and_test(&root->refcount)) |
1763 | anon_vma_free(root); |
1764 | } |
1765 | |
1766 | static struct anon_vma *rmap_walk_anon_lock(struct page *page, |
1767 | struct rmap_walk_control *rwc) |
1768 | { |
1769 | struct anon_vma *anon_vma; |
1770 | |
1771 | if (rwc->anon_lock) |
1772 | return rwc->anon_lock(page); |
1773 | |
1774 | /* |
1775 | * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read() |
1776 | * because that depends on page_mapped(); but not all its usages |
1777 | * are holding mmap_sem. Users without mmap_sem are required to |
1778 | * take a reference count to prevent the anon_vma disappearing |
1779 | */ |
1780 | anon_vma = page_anon_vma(page); |
1781 | if (!anon_vma) |
1782 | return NULL; |
1783 | |
1784 | anon_vma_lock_read(anon_vma); |
1785 | return anon_vma; |
1786 | } |
1787 | |
1788 | /* |
1789 | * rmap_walk_anon - do something to anonymous page using the object-based |
1790 | * rmap method |
1791 | * @page: the page to be handled |
1792 | * @rwc: control variable according to each walk type |
1793 | * |
1794 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1795 | * contained in the anon_vma struct it points to. |
1796 | * |
1797 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1798 | * where the page was found will be held for write. So, we won't recheck |
1799 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1800 | * LOCKED. |
1801 | */ |
1802 | static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc, |
1803 | bool locked) |
1804 | { |
1805 | struct anon_vma *anon_vma; |
1806 | pgoff_t pgoff_start, pgoff_end; |
1807 | struct anon_vma_chain *avc; |
1808 | |
1809 | if (locked) { |
1810 | anon_vma = page_anon_vma(page); |
1811 | /* anon_vma disappear under us? */ |
1812 | VM_BUG_ON_PAGE(!anon_vma, page); |
1813 | } else { |
1814 | anon_vma = rmap_walk_anon_lock(page, rwc); |
1815 | } |
1816 | if (!anon_vma) |
1817 | return; |
1818 | |
1819 | pgoff_start = page_to_pgoff(page); |
1820 | pgoff_end = pgoff_start + hpage_nr_pages(page) - 1; |
1821 | anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, |
1822 | pgoff_start, pgoff_end) { |
1823 | struct vm_area_struct *vma = avc->vma; |
1824 | unsigned long address = vma_address(page, vma); |
1825 | |
1826 | cond_resched(); |
1827 | |
1828 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
1829 | continue; |
1830 | |
1831 | if (!rwc->rmap_one(page, vma, address, rwc->arg)) |
1832 | break; |
1833 | if (rwc->done && rwc->done(page)) |
1834 | break; |
1835 | } |
1836 | |
1837 | if (!locked) |
1838 | anon_vma_unlock_read(anon_vma); |
1839 | } |
1840 | |
1841 | /* |
1842 | * rmap_walk_file - do something to file page using the object-based rmap method |
1843 | * @page: the page to be handled |
1844 | * @rwc: control variable according to each walk type |
1845 | * |
1846 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1847 | * contained in the address_space struct it points to. |
1848 | * |
1849 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1850 | * where the page was found will be held for write. So, we won't recheck |
1851 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1852 | * LOCKED. |
1853 | */ |
1854 | static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc, |
1855 | bool locked) |
1856 | { |
1857 | struct address_space *mapping = page_mapping(page); |
1858 | pgoff_t pgoff_start, pgoff_end; |
1859 | struct vm_area_struct *vma; |
1860 | |
1861 | /* |
1862 | * The page lock not only makes sure that page->mapping cannot |
1863 | * suddenly be NULLified by truncation, it makes sure that the |
1864 | * structure at mapping cannot be freed and reused yet, |
1865 | * so we can safely take mapping->i_mmap_rwsem. |
1866 | */ |
1867 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1868 | |
1869 | if (!mapping) |
1870 | return; |
1871 | |
1872 | pgoff_start = page_to_pgoff(page); |
1873 | pgoff_end = pgoff_start + hpage_nr_pages(page) - 1; |
1874 | if (!locked) |
1875 | i_mmap_lock_read(mapping); |
1876 | vma_interval_tree_foreach(vma, &mapping->i_mmap, |
1877 | pgoff_start, pgoff_end) { |
1878 | unsigned long address = vma_address(page, vma); |
1879 | |
1880 | cond_resched(); |
1881 | |
1882 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
1883 | continue; |
1884 | |
1885 | if (!rwc->rmap_one(page, vma, address, rwc->arg)) |
1886 | goto done; |
1887 | if (rwc->done && rwc->done(page)) |
1888 | goto done; |
1889 | } |
1890 | |
1891 | done: |
1892 | if (!locked) |
1893 | i_mmap_unlock_read(mapping); |
1894 | } |
1895 | |
1896 | void rmap_walk(struct page *page, struct rmap_walk_control *rwc) |
1897 | { |
1898 | if (unlikely(PageKsm(page))) |
1899 | rmap_walk_ksm(page, rwc); |
1900 | else if (PageAnon(page)) |
1901 | rmap_walk_anon(page, rwc, false); |
1902 | else |
1903 | rmap_walk_file(page, rwc, false); |
1904 | } |
1905 | |
1906 | /* Like rmap_walk, but caller holds relevant rmap lock */ |
1907 | void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc) |
1908 | { |
1909 | /* no ksm support for now */ |
1910 | VM_BUG_ON_PAGE(PageKsm(page), page); |
1911 | if (PageAnon(page)) |
1912 | rmap_walk_anon(page, rwc, true); |
1913 | else |
1914 | rmap_walk_file(page, rwc, true); |
1915 | } |
1916 | |
1917 | #ifdef CONFIG_HUGETLB_PAGE |
1918 | /* |
1919 | * The following two functions are for anonymous (private mapped) hugepages. |
1920 | * Unlike common anonymous pages, anonymous hugepages have no accounting code |
1921 | * and no lru code, because we handle hugepages differently from common pages. |
1922 | */ |
1923 | void hugepage_add_anon_rmap(struct page *page, |
1924 | struct vm_area_struct *vma, unsigned long address) |
1925 | { |
1926 | struct anon_vma *anon_vma = vma->anon_vma; |
1927 | int first; |
1928 | |
1929 | BUG_ON(!PageLocked(page)); |
1930 | BUG_ON(!anon_vma); |
1931 | /* address might be in next vma when migration races vma_adjust */ |
1932 | first = atomic_inc_and_test(compound_mapcount_ptr(page)); |
1933 | if (first) |
1934 | __page_set_anon_rmap(page, vma, address, 0); |
1935 | } |
1936 | |
1937 | void hugepage_add_new_anon_rmap(struct page *page, |
1938 | struct vm_area_struct *vma, unsigned long address) |
1939 | { |
1940 | BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
1941 | atomic_set(compound_mapcount_ptr(page), 0); |
1942 | __page_set_anon_rmap(page, vma, address, 1); |
1943 | } |
1944 | #endif /* CONFIG_HUGETLB_PAGE */ |
1945 | |