Line data Source code
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_rwsem (while writing or truncating, not reading or faulting)
24 : * mm->mmap_lock
25 : * mapping->invalidate_lock (in filemap_fault)
26 : * page->flags PG_locked (lock_page)
27 : * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
28 : * mapping->i_mmap_rwsem
29 : * anon_vma->rwsem
30 : * mm->page_table_lock or pte_lock
31 : * swap_lock (in swap_duplicate, swap_info_get)
32 : * mmlist_lock (in mmput, drain_mmlist and others)
33 : * mapping->private_lock (in block_dirty_folio)
34 : * folio_lock_memcg move_lock (in block_dirty_folio)
35 : * i_pages lock (widely used)
36 : * lruvec->lru_lock (in folio_lruvec_lock_irq)
37 : * inode->i_lock (in set_page_dirty's __mark_inode_dirty)
38 : * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
39 : * sb_lock (within inode_lock in fs/fs-writeback.c)
40 : * i_pages lock (widely used, in set_page_dirty,
41 : * in arch-dependent flush_dcache_mmap_lock,
42 : * within bdi.wb->list_lock in __sync_single_inode)
43 : *
44 : * anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon)
45 : * ->tasklist_lock
46 : * pte map lock
47 : *
48 : * hugetlbfs PageHuge() take locks in this order:
49 : * hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
50 : * vma_lock (hugetlb specific lock for pmd_sharing)
51 : * mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
52 : * page->flags PG_locked (lock_page)
53 : */
54 :
55 : #include <linux/mm.h>
56 : #include <linux/sched/mm.h>
57 : #include <linux/sched/task.h>
58 : #include <linux/pagemap.h>
59 : #include <linux/swap.h>
60 : #include <linux/swapops.h>
61 : #include <linux/slab.h>
62 : #include <linux/init.h>
63 : #include <linux/ksm.h>
64 : #include <linux/rmap.h>
65 : #include <linux/rcupdate.h>
66 : #include <linux/export.h>
67 : #include <linux/memcontrol.h>
68 : #include <linux/mmu_notifier.h>
69 : #include <linux/migrate.h>
70 : #include <linux/hugetlb.h>
71 : #include <linux/huge_mm.h>
72 : #include <linux/backing-dev.h>
73 : #include <linux/page_idle.h>
74 : #include <linux/memremap.h>
75 : #include <linux/userfaultfd_k.h>
76 : #include <linux/mm_inline.h>
77 :
78 : #include <asm/tlbflush.h>
79 :
80 : #define CREATE_TRACE_POINTS
81 : #include <trace/events/tlb.h>
82 : #include <trace/events/migrate.h>
83 :
84 : #include "internal.h"
85 :
86 : static struct kmem_cache *anon_vma_cachep;
87 : static struct kmem_cache *anon_vma_chain_cachep;
88 :
89 0 : static inline struct anon_vma *anon_vma_alloc(void)
90 : {
91 : struct anon_vma *anon_vma;
92 :
93 0 : anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
94 0 : if (anon_vma) {
95 0 : atomic_set(&anon_vma->refcount, 1);
96 0 : anon_vma->num_children = 0;
97 0 : anon_vma->num_active_vmas = 0;
98 0 : anon_vma->parent = anon_vma;
99 : /*
100 : * Initialise the anon_vma root to point to itself. If called
101 : * from fork, the root will be reset to the parents anon_vma.
102 : */
103 0 : anon_vma->root = anon_vma;
104 : }
105 :
106 0 : return anon_vma;
107 : }
108 :
109 0 : static inline void anon_vma_free(struct anon_vma *anon_vma)
110 : {
111 : VM_BUG_ON(atomic_read(&anon_vma->refcount));
112 :
113 : /*
114 : * Synchronize against folio_lock_anon_vma_read() such that
115 : * we can safely hold the lock without the anon_vma getting
116 : * freed.
117 : *
118 : * Relies on the full mb implied by the atomic_dec_and_test() from
119 : * put_anon_vma() against the acquire barrier implied by
120 : * down_read_trylock() from folio_lock_anon_vma_read(). This orders:
121 : *
122 : * folio_lock_anon_vma_read() VS put_anon_vma()
123 : * down_read_trylock() atomic_dec_and_test()
124 : * LOCK MB
125 : * atomic_read() rwsem_is_locked()
126 : *
127 : * LOCK should suffice since the actual taking of the lock must
128 : * happen _before_ what follows.
129 : */
130 : might_sleep();
131 0 : if (rwsem_is_locked(&anon_vma->root->rwsem)) {
132 0 : anon_vma_lock_write(anon_vma);
133 0 : anon_vma_unlock_write(anon_vma);
134 : }
135 :
136 0 : kmem_cache_free(anon_vma_cachep, anon_vma);
137 0 : }
138 :
139 : static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
140 : {
141 0 : return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
142 : }
143 :
144 : static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
145 : {
146 0 : kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
147 : }
148 :
149 : static void anon_vma_chain_link(struct vm_area_struct *vma,
150 : struct anon_vma_chain *avc,
151 : struct anon_vma *anon_vma)
152 : {
153 0 : avc->vma = vma;
154 0 : avc->anon_vma = anon_vma;
155 0 : list_add(&avc->same_vma, &vma->anon_vma_chain);
156 0 : anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
157 : }
158 :
159 : /**
160 : * __anon_vma_prepare - attach an anon_vma to a memory region
161 : * @vma: the memory region in question
162 : *
163 : * This makes sure the memory mapping described by 'vma' has
164 : * an 'anon_vma' attached to it, so that we can associate the
165 : * anonymous pages mapped into it with that anon_vma.
166 : *
167 : * The common case will be that we already have one, which
168 : * is handled inline by anon_vma_prepare(). But if
169 : * not we either need to find an adjacent mapping that we
170 : * can re-use the anon_vma from (very common when the only
171 : * reason for splitting a vma has been mprotect()), or we
172 : * allocate a new one.
173 : *
174 : * Anon-vma allocations are very subtle, because we may have
175 : * optimistically looked up an anon_vma in folio_lock_anon_vma_read()
176 : * and that may actually touch the rwsem even in the newly
177 : * allocated vma (it depends on RCU to make sure that the
178 : * anon_vma isn't actually destroyed).
179 : *
180 : * As a result, we need to do proper anon_vma locking even
181 : * for the new allocation. At the same time, we do not want
182 : * to do any locking for the common case of already having
183 : * an anon_vma.
184 : *
185 : * This must be called with the mmap_lock held for reading.
186 : */
187 0 : int __anon_vma_prepare(struct vm_area_struct *vma)
188 : {
189 0 : struct mm_struct *mm = vma->vm_mm;
190 : struct anon_vma *anon_vma, *allocated;
191 : struct anon_vma_chain *avc;
192 :
193 : might_sleep();
194 :
195 0 : avc = anon_vma_chain_alloc(GFP_KERNEL);
196 0 : if (!avc)
197 : goto out_enomem;
198 :
199 0 : anon_vma = find_mergeable_anon_vma(vma);
200 0 : allocated = NULL;
201 0 : if (!anon_vma) {
202 0 : anon_vma = anon_vma_alloc();
203 0 : if (unlikely(!anon_vma))
204 : goto out_enomem_free_avc;
205 0 : anon_vma->num_children++; /* self-parent link for new root */
206 0 : allocated = anon_vma;
207 : }
208 :
209 0 : anon_vma_lock_write(anon_vma);
210 : /* page_table_lock to protect against threads */
211 0 : spin_lock(&mm->page_table_lock);
212 0 : if (likely(!vma->anon_vma)) {
213 0 : vma->anon_vma = anon_vma;
214 0 : anon_vma_chain_link(vma, avc, anon_vma);
215 0 : anon_vma->num_active_vmas++;
216 0 : allocated = NULL;
217 0 : avc = NULL;
218 : }
219 0 : spin_unlock(&mm->page_table_lock);
220 0 : anon_vma_unlock_write(anon_vma);
221 :
222 0 : if (unlikely(allocated))
223 : put_anon_vma(allocated);
224 0 : if (unlikely(avc))
225 : anon_vma_chain_free(avc);
226 :
227 : return 0;
228 :
229 : out_enomem_free_avc:
230 : anon_vma_chain_free(avc);
231 : out_enomem:
232 : return -ENOMEM;
233 : }
234 :
235 : /*
236 : * This is a useful helper function for locking the anon_vma root as
237 : * we traverse the vma->anon_vma_chain, looping over anon_vma's that
238 : * have the same vma.
239 : *
240 : * Such anon_vma's should have the same root, so you'd expect to see
241 : * just a single mutex_lock for the whole traversal.
242 : */
243 0 : static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
244 : {
245 0 : struct anon_vma *new_root = anon_vma->root;
246 0 : if (new_root != root) {
247 0 : if (WARN_ON_ONCE(root))
248 0 : up_write(&root->rwsem);
249 0 : root = new_root;
250 0 : down_write(&root->rwsem);
251 : }
252 0 : return root;
253 : }
254 :
255 : static inline void unlock_anon_vma_root(struct anon_vma *root)
256 : {
257 0 : if (root)
258 0 : up_write(&root->rwsem);
259 : }
260 :
261 : /*
262 : * Attach the anon_vmas from src to dst.
263 : * Returns 0 on success, -ENOMEM on failure.
264 : *
265 : * anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(),
266 : * copy_vma() and anon_vma_fork(). The first four want an exact copy of src,
267 : * while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to
268 : * prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before
269 : * call, we can identify this case by checking (!dst->anon_vma &&
270 : * src->anon_vma).
271 : *
272 : * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find
273 : * and reuse existing anon_vma which has no vmas and only one child anon_vma.
274 : * This prevents degradation of anon_vma hierarchy to endless linear chain in
275 : * case of constantly forking task. On the other hand, an anon_vma with more
276 : * than one child isn't reused even if there was no alive vma, thus rmap
277 : * walker has a good chance of avoiding scanning the whole hierarchy when it
278 : * searches where page is mapped.
279 : */
280 0 : int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
281 : {
282 : struct anon_vma_chain *avc, *pavc;
283 0 : struct anon_vma *root = NULL;
284 :
285 0 : list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
286 : struct anon_vma *anon_vma;
287 :
288 0 : avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
289 0 : if (unlikely(!avc)) {
290 0 : unlock_anon_vma_root(root);
291 0 : root = NULL;
292 0 : avc = anon_vma_chain_alloc(GFP_KERNEL);
293 0 : if (!avc)
294 : goto enomem_failure;
295 : }
296 0 : anon_vma = pavc->anon_vma;
297 0 : root = lock_anon_vma_root(root, anon_vma);
298 0 : anon_vma_chain_link(dst, avc, anon_vma);
299 :
300 : /*
301 : * Reuse existing anon_vma if it has no vma and only one
302 : * anon_vma child.
303 : *
304 : * Root anon_vma is never reused:
305 : * it has self-parent reference and at least one child.
306 : */
307 0 : if (!dst->anon_vma && src->anon_vma &&
308 0 : anon_vma->num_children < 2 &&
309 0 : anon_vma->num_active_vmas == 0)
310 0 : dst->anon_vma = anon_vma;
311 : }
312 0 : if (dst->anon_vma)
313 0 : dst->anon_vma->num_active_vmas++;
314 : unlock_anon_vma_root(root);
315 : return 0;
316 :
317 : enomem_failure:
318 : /*
319 : * dst->anon_vma is dropped here otherwise its num_active_vmas can
320 : * be incorrectly decremented in unlink_anon_vmas().
321 : * We can safely do this because callers of anon_vma_clone() don't care
322 : * about dst->anon_vma if anon_vma_clone() failed.
323 : */
324 0 : dst->anon_vma = NULL;
325 0 : unlink_anon_vmas(dst);
326 0 : return -ENOMEM;
327 : }
328 :
329 : /*
330 : * Attach vma to its own anon_vma, as well as to the anon_vmas that
331 : * the corresponding VMA in the parent process is attached to.
332 : * Returns 0 on success, non-zero on failure.
333 : */
334 0 : int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
335 : {
336 : struct anon_vma_chain *avc;
337 : struct anon_vma *anon_vma;
338 : int error;
339 :
340 : /* Don't bother if the parent process has no anon_vma here. */
341 0 : if (!pvma->anon_vma)
342 : return 0;
343 :
344 : /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
345 0 : vma->anon_vma = NULL;
346 :
347 : /*
348 : * First, attach the new VMA to the parent VMA's anon_vmas,
349 : * so rmap can find non-COWed pages in child processes.
350 : */
351 0 : error = anon_vma_clone(vma, pvma);
352 0 : if (error)
353 : return error;
354 :
355 : /* An existing anon_vma has been reused, all done then. */
356 0 : if (vma->anon_vma)
357 : return 0;
358 :
359 : /* Then add our own anon_vma. */
360 0 : anon_vma = anon_vma_alloc();
361 0 : if (!anon_vma)
362 : goto out_error;
363 0 : anon_vma->num_active_vmas++;
364 0 : avc = anon_vma_chain_alloc(GFP_KERNEL);
365 0 : if (!avc)
366 : goto out_error_free_anon_vma;
367 :
368 : /*
369 : * The root anon_vma's rwsem is the lock actually used when we
370 : * lock any of the anon_vmas in this anon_vma tree.
371 : */
372 0 : anon_vma->root = pvma->anon_vma->root;
373 0 : anon_vma->parent = pvma->anon_vma;
374 : /*
375 : * With refcounts, an anon_vma can stay around longer than the
376 : * process it belongs to. The root anon_vma needs to be pinned until
377 : * this anon_vma is freed, because the lock lives in the root.
378 : */
379 0 : get_anon_vma(anon_vma->root);
380 : /* Mark this anon_vma as the one where our new (COWed) pages go. */
381 0 : vma->anon_vma = anon_vma;
382 0 : anon_vma_lock_write(anon_vma);
383 0 : anon_vma_chain_link(vma, avc, anon_vma);
384 0 : anon_vma->parent->num_children++;
385 0 : anon_vma_unlock_write(anon_vma);
386 :
387 0 : return 0;
388 :
389 : out_error_free_anon_vma:
390 : put_anon_vma(anon_vma);
391 : out_error:
392 0 : unlink_anon_vmas(vma);
393 0 : return -ENOMEM;
394 : }
395 :
396 0 : void unlink_anon_vmas(struct vm_area_struct *vma)
397 : {
398 : struct anon_vma_chain *avc, *next;
399 0 : struct anon_vma *root = NULL;
400 :
401 : /*
402 : * Unlink each anon_vma chained to the VMA. This list is ordered
403 : * from newest to oldest, ensuring the root anon_vma gets freed last.
404 : */
405 0 : list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
406 0 : struct anon_vma *anon_vma = avc->anon_vma;
407 :
408 0 : root = lock_anon_vma_root(root, anon_vma);
409 0 : anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
410 :
411 : /*
412 : * Leave empty anon_vmas on the list - we'll need
413 : * to free them outside the lock.
414 : */
415 0 : if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
416 0 : anon_vma->parent->num_children--;
417 0 : continue;
418 : }
419 :
420 0 : list_del(&avc->same_vma);
421 : anon_vma_chain_free(avc);
422 : }
423 0 : if (vma->anon_vma) {
424 0 : vma->anon_vma->num_active_vmas--;
425 :
426 : /*
427 : * vma would still be needed after unlink, and anon_vma will be prepared
428 : * when handle fault.
429 : */
430 0 : vma->anon_vma = NULL;
431 : }
432 0 : unlock_anon_vma_root(root);
433 :
434 : /*
435 : * Iterate the list once more, it now only contains empty and unlinked
436 : * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
437 : * needing to write-acquire the anon_vma->root->rwsem.
438 : */
439 0 : list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
440 0 : struct anon_vma *anon_vma = avc->anon_vma;
441 :
442 : VM_WARN_ON(anon_vma->num_children);
443 : VM_WARN_ON(anon_vma->num_active_vmas);
444 0 : put_anon_vma(anon_vma);
445 :
446 0 : list_del(&avc->same_vma);
447 0 : anon_vma_chain_free(avc);
448 : }
449 0 : }
450 :
451 0 : static void anon_vma_ctor(void *data)
452 : {
453 0 : struct anon_vma *anon_vma = data;
454 :
455 0 : init_rwsem(&anon_vma->rwsem);
456 0 : atomic_set(&anon_vma->refcount, 0);
457 0 : anon_vma->rb_root = RB_ROOT_CACHED;
458 0 : }
459 :
460 1 : void __init anon_vma_init(void)
461 : {
462 1 : anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
463 : 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
464 : anon_vma_ctor);
465 1 : anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
466 : SLAB_PANIC|SLAB_ACCOUNT);
467 1 : }
468 :
469 : /*
470 : * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
471 : *
472 : * Since there is no serialization what so ever against page_remove_rmap()
473 : * the best this function can do is return a refcount increased anon_vma
474 : * that might have been relevant to this page.
475 : *
476 : * The page might have been remapped to a different anon_vma or the anon_vma
477 : * returned may already be freed (and even reused).
478 : *
479 : * In case it was remapped to a different anon_vma, the new anon_vma will be a
480 : * child of the old anon_vma, and the anon_vma lifetime rules will therefore
481 : * ensure that any anon_vma obtained from the page will still be valid for as
482 : * long as we observe page_mapped() [ hence all those page_mapped() tests ].
483 : *
484 : * All users of this function must be very careful when walking the anon_vma
485 : * chain and verify that the page in question is indeed mapped in it
486 : * [ something equivalent to page_mapped_in_vma() ].
487 : *
488 : * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from
489 : * page_remove_rmap() that the anon_vma pointer from page->mapping is valid
490 : * if there is a mapcount, we can dereference the anon_vma after observing
491 : * those.
492 : */
493 0 : struct anon_vma *folio_get_anon_vma(struct folio *folio)
494 : {
495 0 : struct anon_vma *anon_vma = NULL;
496 : unsigned long anon_mapping;
497 :
498 : rcu_read_lock();
499 0 : anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
500 0 : if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
501 : goto out;
502 0 : if (!folio_mapped(folio))
503 : goto out;
504 :
505 0 : anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
506 0 : if (!atomic_inc_not_zero(&anon_vma->refcount)) {
507 : anon_vma = NULL;
508 : goto out;
509 : }
510 :
511 : /*
512 : * If this folio is still mapped, then its anon_vma cannot have been
513 : * freed. But if it has been unmapped, we have no security against the
514 : * anon_vma structure being freed and reused (for another anon_vma:
515 : * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
516 : * above cannot corrupt).
517 : */
518 0 : if (!folio_mapped(folio)) {
519 0 : rcu_read_unlock();
520 : put_anon_vma(anon_vma);
521 : return NULL;
522 : }
523 : out:
524 : rcu_read_unlock();
525 :
526 0 : return anon_vma;
527 : }
528 :
529 : /*
530 : * Similar to folio_get_anon_vma() except it locks the anon_vma.
531 : *
532 : * Its a little more complex as it tries to keep the fast path to a single
533 : * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
534 : * reference like with folio_get_anon_vma() and then block on the mutex
535 : * on !rwc->try_lock case.
536 : */
537 0 : struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
538 : struct rmap_walk_control *rwc)
539 : {
540 0 : struct anon_vma *anon_vma = NULL;
541 : struct anon_vma *root_anon_vma;
542 : unsigned long anon_mapping;
543 :
544 : rcu_read_lock();
545 0 : anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
546 0 : if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
547 : goto out;
548 0 : if (!folio_mapped(folio))
549 : goto out;
550 :
551 0 : anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
552 0 : root_anon_vma = READ_ONCE(anon_vma->root);
553 0 : if (down_read_trylock(&root_anon_vma->rwsem)) {
554 : /*
555 : * If the folio is still mapped, then this anon_vma is still
556 : * its anon_vma, and holding the mutex ensures that it will
557 : * not go away, see anon_vma_free().
558 : */
559 0 : if (!folio_mapped(folio)) {
560 0 : up_read(&root_anon_vma->rwsem);
561 0 : anon_vma = NULL;
562 : }
563 : goto out;
564 : }
565 :
566 0 : if (rwc && rwc->try_lock) {
567 0 : anon_vma = NULL;
568 0 : rwc->contended = true;
569 0 : goto out;
570 : }
571 :
572 : /* trylock failed, we got to sleep */
573 0 : if (!atomic_inc_not_zero(&anon_vma->refcount)) {
574 : anon_vma = NULL;
575 : goto out;
576 : }
577 :
578 0 : if (!folio_mapped(folio)) {
579 0 : rcu_read_unlock();
580 : put_anon_vma(anon_vma);
581 : return NULL;
582 : }
583 :
584 : /* we pinned the anon_vma, its safe to sleep */
585 : rcu_read_unlock();
586 0 : anon_vma_lock_read(anon_vma);
587 :
588 0 : if (atomic_dec_and_test(&anon_vma->refcount)) {
589 : /*
590 : * Oops, we held the last refcount, release the lock
591 : * and bail -- can't simply use put_anon_vma() because
592 : * we'll deadlock on the anon_vma_lock_write() recursion.
593 : */
594 0 : anon_vma_unlock_read(anon_vma);
595 0 : __put_anon_vma(anon_vma);
596 0 : anon_vma = NULL;
597 : }
598 :
599 : return anon_vma;
600 :
601 : out:
602 : rcu_read_unlock();
603 0 : return anon_vma;
604 : }
605 :
606 : #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
607 : /*
608 : * Flush TLB entries for recently unmapped pages from remote CPUs. It is
609 : * important if a PTE was dirty when it was unmapped that it's flushed
610 : * before any IO is initiated on the page to prevent lost writes. Similarly,
611 : * it must be flushed before freeing to prevent data leakage.
612 : */
613 : void try_to_unmap_flush(void)
614 : {
615 : struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
616 :
617 : if (!tlb_ubc->flush_required)
618 : return;
619 :
620 : arch_tlbbatch_flush(&tlb_ubc->arch);
621 : tlb_ubc->flush_required = false;
622 : tlb_ubc->writable = false;
623 : }
624 :
625 : /* Flush iff there are potentially writable TLB entries that can race with IO */
626 : void try_to_unmap_flush_dirty(void)
627 : {
628 : struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
629 :
630 : if (tlb_ubc->writable)
631 : try_to_unmap_flush();
632 : }
633 :
634 : /*
635 : * Bits 0-14 of mm->tlb_flush_batched record pending generations.
636 : * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
637 : */
638 : #define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16
639 : #define TLB_FLUSH_BATCH_PENDING_MASK \
640 : ((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
641 : #define TLB_FLUSH_BATCH_PENDING_LARGE \
642 : (TLB_FLUSH_BATCH_PENDING_MASK / 2)
643 :
644 : static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
645 : {
646 : struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
647 : int batch, nbatch;
648 :
649 : arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
650 : tlb_ubc->flush_required = true;
651 :
652 : /*
653 : * Ensure compiler does not re-order the setting of tlb_flush_batched
654 : * before the PTE is cleared.
655 : */
656 : barrier();
657 : batch = atomic_read(&mm->tlb_flush_batched);
658 : retry:
659 : if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
660 : /*
661 : * Prevent `pending' from catching up with `flushed' because of
662 : * overflow. Reset `pending' and `flushed' to be 1 and 0 if
663 : * `pending' becomes large.
664 : */
665 : nbatch = atomic_cmpxchg(&mm->tlb_flush_batched, batch, 1);
666 : if (nbatch != batch) {
667 : batch = nbatch;
668 : goto retry;
669 : }
670 : } else {
671 : atomic_inc(&mm->tlb_flush_batched);
672 : }
673 :
674 : /*
675 : * If the PTE was dirty then it's best to assume it's writable. The
676 : * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
677 : * before the page is queued for IO.
678 : */
679 : if (writable)
680 : tlb_ubc->writable = true;
681 : }
682 :
683 : /*
684 : * Returns true if the TLB flush should be deferred to the end of a batch of
685 : * unmap operations to reduce IPIs.
686 : */
687 : static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
688 : {
689 : bool should_defer = false;
690 :
691 : if (!(flags & TTU_BATCH_FLUSH))
692 : return false;
693 :
694 : /* If remote CPUs need to be flushed then defer batch the flush */
695 : if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
696 : should_defer = true;
697 : put_cpu();
698 :
699 : return should_defer;
700 : }
701 :
702 : /*
703 : * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
704 : * releasing the PTL if TLB flushes are batched. It's possible for a parallel
705 : * operation such as mprotect or munmap to race between reclaim unmapping
706 : * the page and flushing the page. If this race occurs, it potentially allows
707 : * access to data via a stale TLB entry. Tracking all mm's that have TLB
708 : * batching in flight would be expensive during reclaim so instead track
709 : * whether TLB batching occurred in the past and if so then do a flush here
710 : * if required. This will cost one additional flush per reclaim cycle paid
711 : * by the first operation at risk such as mprotect and mumap.
712 : *
713 : * This must be called under the PTL so that an access to tlb_flush_batched
714 : * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
715 : * via the PTL.
716 : */
717 : void flush_tlb_batched_pending(struct mm_struct *mm)
718 : {
719 : int batch = atomic_read(&mm->tlb_flush_batched);
720 : int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
721 : int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
722 :
723 : if (pending != flushed) {
724 : flush_tlb_mm(mm);
725 : /*
726 : * If the new TLB flushing is pending during flushing, leave
727 : * mm->tlb_flush_batched as is, to avoid losing flushing.
728 : */
729 : atomic_cmpxchg(&mm->tlb_flush_batched, batch,
730 : pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
731 : }
732 : }
733 : #else
734 : static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
735 : {
736 : }
737 :
738 : static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
739 : {
740 : return false;
741 : }
742 : #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
743 :
744 : /*
745 : * At what user virtual address is page expected in vma?
746 : * Caller should check the page is actually part of the vma.
747 : */
748 0 : unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
749 : {
750 0 : struct folio *folio = page_folio(page);
751 0 : if (folio_test_anon(folio)) {
752 0 : struct anon_vma *page__anon_vma = folio_anon_vma(folio);
753 : /*
754 : * Note: swapoff's unuse_vma() is more efficient with this
755 : * check, and needs it to match anon_vma when KSM is active.
756 : */
757 0 : if (!vma->anon_vma || !page__anon_vma ||
758 0 : vma->anon_vma->root != page__anon_vma->root)
759 : return -EFAULT;
760 0 : } else if (!vma->vm_file) {
761 : return -EFAULT;
762 0 : } else if (vma->vm_file->f_mapping != folio->mapping) {
763 : return -EFAULT;
764 : }
765 :
766 0 : return vma_address(page, vma);
767 : }
768 :
769 : /*
770 : * Returns the actual pmd_t* where we expect 'address' to be mapped from, or
771 : * NULL if it doesn't exist. No guarantees / checks on what the pmd_t*
772 : * represents.
773 : */
774 0 : pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
775 : {
776 : pgd_t *pgd;
777 : p4d_t *p4d;
778 : pud_t *pud;
779 0 : pmd_t *pmd = NULL;
780 :
781 0 : pgd = pgd_offset(mm, address);
782 : if (!pgd_present(*pgd))
783 : goto out;
784 :
785 0 : p4d = p4d_offset(pgd, address);
786 : if (!p4d_present(*p4d))
787 : goto out;
788 :
789 0 : pud = pud_offset(p4d, address);
790 0 : if (!pud_present(*pud))
791 : goto out;
792 :
793 0 : pmd = pmd_offset(pud, address);
794 : out:
795 0 : return pmd;
796 : }
797 :
798 : struct folio_referenced_arg {
799 : int mapcount;
800 : int referenced;
801 : unsigned long vm_flags;
802 : struct mem_cgroup *memcg;
803 : };
804 : /*
805 : * arg: folio_referenced_arg will be passed
806 : */
807 0 : static bool folio_referenced_one(struct folio *folio,
808 : struct vm_area_struct *vma, unsigned long address, void *arg)
809 : {
810 0 : struct folio_referenced_arg *pra = arg;
811 0 : DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
812 0 : int referenced = 0;
813 :
814 0 : while (page_vma_mapped_walk(&pvmw)) {
815 0 : address = pvmw.address;
816 :
817 0 : if ((vma->vm_flags & VM_LOCKED) &&
818 0 : (!folio_test_large(folio) || !pvmw.pte)) {
819 : /* Restore the mlock which got missed */
820 0 : mlock_vma_folio(folio, vma, !pvmw.pte);
821 0 : page_vma_mapped_walk_done(&pvmw);
822 0 : pra->vm_flags |= VM_LOCKED;
823 0 : return false; /* To break the loop */
824 : }
825 :
826 0 : if (pvmw.pte) {
827 : if (lru_gen_enabled() && pte_young(*pvmw.pte)) {
828 : lru_gen_look_around(&pvmw);
829 : referenced++;
830 : }
831 :
832 0 : if (ptep_clear_flush_young_notify(vma, address,
833 : pvmw.pte))
834 0 : referenced++;
835 : } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
836 : if (pmdp_clear_flush_young_notify(vma, address,
837 : pvmw.pmd))
838 : referenced++;
839 : } else {
840 : /* unexpected pmd-mapped folio? */
841 0 : WARN_ON_ONCE(1);
842 : }
843 :
844 0 : pra->mapcount--;
845 : }
846 :
847 : if (referenced)
848 : folio_clear_idle(folio);
849 0 : if (folio_test_clear_young(folio))
850 : referenced++;
851 :
852 0 : if (referenced) {
853 0 : pra->referenced++;
854 0 : pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
855 : }
856 :
857 0 : if (!pra->mapcount)
858 : return false; /* To break the loop */
859 :
860 0 : return true;
861 : }
862 :
863 0 : static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
864 : {
865 0 : struct folio_referenced_arg *pra = arg;
866 0 : struct mem_cgroup *memcg = pra->memcg;
867 :
868 : /*
869 : * Ignore references from this mapping if it has no recency. If the
870 : * folio has been used in another mapping, we will catch it; if this
871 : * other mapping is already gone, the unmap path will have set the
872 : * referenced flag or activated the folio in zap_pte_range().
873 : */
874 0 : if (!vma_has_recency(vma))
875 : return true;
876 :
877 : /*
878 : * If we are reclaiming on behalf of a cgroup, skip counting on behalf
879 : * of references from different cgroups.
880 : */
881 : if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
882 : return true;
883 :
884 : return false;
885 : }
886 :
887 : /**
888 : * folio_referenced() - Test if the folio was referenced.
889 : * @folio: The folio to test.
890 : * @is_locked: Caller holds lock on the folio.
891 : * @memcg: target memory cgroup
892 : * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
893 : *
894 : * Quick test_and_clear_referenced for all mappings of a folio,
895 : *
896 : * Return: The number of mappings which referenced the folio. Return -1 if
897 : * the function bailed out due to rmap lock contention.
898 : */
899 0 : int folio_referenced(struct folio *folio, int is_locked,
900 : struct mem_cgroup *memcg, unsigned long *vm_flags)
901 : {
902 0 : int we_locked = 0;
903 0 : struct folio_referenced_arg pra = {
904 0 : .mapcount = folio_mapcount(folio),
905 : .memcg = memcg,
906 : };
907 0 : struct rmap_walk_control rwc = {
908 : .rmap_one = folio_referenced_one,
909 : .arg = (void *)&pra,
910 : .anon_lock = folio_lock_anon_vma_read,
911 : .try_lock = true,
912 : .invalid_vma = invalid_folio_referenced_vma,
913 : };
914 :
915 0 : *vm_flags = 0;
916 0 : if (!pra.mapcount)
917 : return 0;
918 :
919 0 : if (!folio_raw_mapping(folio))
920 : return 0;
921 :
922 0 : if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
923 0 : we_locked = folio_trylock(folio);
924 0 : if (!we_locked)
925 : return 1;
926 : }
927 :
928 0 : rmap_walk(folio, &rwc);
929 0 : *vm_flags = pra.vm_flags;
930 :
931 0 : if (we_locked)
932 0 : folio_unlock(folio);
933 :
934 0 : return rwc.contended ? -1 : pra.referenced;
935 : }
936 :
937 0 : static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
938 : {
939 0 : int cleaned = 0;
940 0 : struct vm_area_struct *vma = pvmw->vma;
941 : struct mmu_notifier_range range;
942 0 : unsigned long address = pvmw->address;
943 :
944 : /*
945 : * We have to assume the worse case ie pmd for invalidation. Note that
946 : * the folio can not be freed from this function.
947 : */
948 : mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0,
949 : vma->vm_mm, address, vma_address_end(pvmw));
950 : mmu_notifier_invalidate_range_start(&range);
951 :
952 0 : while (page_vma_mapped_walk(pvmw)) {
953 0 : int ret = 0;
954 :
955 0 : address = pvmw->address;
956 0 : if (pvmw->pte) {
957 : pte_t entry;
958 0 : pte_t *pte = pvmw->pte;
959 :
960 0 : if (!pte_dirty(*pte) && !pte_write(*pte))
961 0 : continue;
962 :
963 0 : flush_cache_page(vma, address, pte_pfn(*pte));
964 0 : entry = ptep_clear_flush(vma, address, pte);
965 0 : entry = pte_wrprotect(entry);
966 0 : entry = pte_mkclean(entry);
967 0 : set_pte_at(vma->vm_mm, address, pte, entry);
968 : ret = 1;
969 : } else {
970 : #ifdef CONFIG_TRANSPARENT_HUGEPAGE
971 : pmd_t *pmd = pvmw->pmd;
972 : pmd_t entry;
973 :
974 : if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
975 : continue;
976 :
977 : flush_cache_range(vma, address,
978 : address + HPAGE_PMD_SIZE);
979 : entry = pmdp_invalidate(vma, address, pmd);
980 : entry = pmd_wrprotect(entry);
981 : entry = pmd_mkclean(entry);
982 : set_pmd_at(vma->vm_mm, address, pmd, entry);
983 : ret = 1;
984 : #else
985 : /* unexpected pmd-mapped folio? */
986 0 : WARN_ON_ONCE(1);
987 : #endif
988 : }
989 :
990 : /*
991 : * No need to call mmu_notifier_invalidate_range() as we are
992 : * downgrading page table protection not changing it to point
993 : * to a new page.
994 : *
995 : * See Documentation/mm/mmu_notifier.rst
996 : */
997 0 : if (ret)
998 0 : cleaned++;
999 : }
1000 :
1001 0 : mmu_notifier_invalidate_range_end(&range);
1002 :
1003 0 : return cleaned;
1004 : }
1005 :
1006 0 : static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
1007 : unsigned long address, void *arg)
1008 : {
1009 0 : DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
1010 0 : int *cleaned = arg;
1011 :
1012 0 : *cleaned += page_vma_mkclean_one(&pvmw);
1013 :
1014 0 : return true;
1015 : }
1016 :
1017 0 : static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
1018 : {
1019 0 : if (vma->vm_flags & VM_SHARED)
1020 : return false;
1021 :
1022 0 : return true;
1023 : }
1024 :
1025 0 : int folio_mkclean(struct folio *folio)
1026 : {
1027 0 : int cleaned = 0;
1028 : struct address_space *mapping;
1029 0 : struct rmap_walk_control rwc = {
1030 : .arg = (void *)&cleaned,
1031 : .rmap_one = page_mkclean_one,
1032 : .invalid_vma = invalid_mkclean_vma,
1033 : };
1034 :
1035 0 : BUG_ON(!folio_test_locked(folio));
1036 :
1037 0 : if (!folio_mapped(folio))
1038 : return 0;
1039 :
1040 0 : mapping = folio_mapping(folio);
1041 0 : if (!mapping)
1042 : return 0;
1043 :
1044 0 : rmap_walk(folio, &rwc);
1045 :
1046 0 : return cleaned;
1047 : }
1048 : EXPORT_SYMBOL_GPL(folio_mkclean);
1049 :
1050 : /**
1051 : * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
1052 : * [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
1053 : * within the @vma of shared mappings. And since clean PTEs
1054 : * should also be readonly, write protects them too.
1055 : * @pfn: start pfn.
1056 : * @nr_pages: number of physically contiguous pages srarting with @pfn.
1057 : * @pgoff: page offset that the @pfn mapped with.
1058 : * @vma: vma that @pfn mapped within.
1059 : *
1060 : * Returns the number of cleaned PTEs (including PMDs).
1061 : */
1062 0 : int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
1063 : struct vm_area_struct *vma)
1064 : {
1065 0 : struct page_vma_mapped_walk pvmw = {
1066 : .pfn = pfn,
1067 : .nr_pages = nr_pages,
1068 : .pgoff = pgoff,
1069 : .vma = vma,
1070 : .flags = PVMW_SYNC,
1071 : };
1072 :
1073 0 : if (invalid_mkclean_vma(vma, NULL))
1074 : return 0;
1075 :
1076 0 : pvmw.address = vma_pgoff_address(pgoff, nr_pages, vma);
1077 : VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
1078 :
1079 0 : return page_vma_mkclean_one(&pvmw);
1080 : }
1081 :
1082 0 : int folio_total_mapcount(struct folio *folio)
1083 : {
1084 0 : int mapcount = folio_entire_mapcount(folio);
1085 : int nr_pages;
1086 : int i;
1087 :
1088 : /* In the common case, avoid the loop when no pages mapped by PTE */
1089 0 : if (folio_nr_pages_mapped(folio) == 0)
1090 : return mapcount;
1091 : /*
1092 : * Add all the PTE mappings of those pages mapped by PTE.
1093 : * Limit the loop to folio_nr_pages_mapped()?
1094 : * Perhaps: given all the raciness, that may be a good or a bad idea.
1095 : */
1096 0 : nr_pages = folio_nr_pages(folio);
1097 0 : for (i = 0; i < nr_pages; i++)
1098 0 : mapcount += atomic_read(&folio_page(folio, i)->_mapcount);
1099 :
1100 : /* But each of those _mapcounts was based on -1 */
1101 0 : mapcount += nr_pages;
1102 0 : return mapcount;
1103 : }
1104 :
1105 : /**
1106 : * page_move_anon_rmap - move a page to our anon_vma
1107 : * @page: the page to move to our anon_vma
1108 : * @vma: the vma the page belongs to
1109 : *
1110 : * When a page belongs exclusively to one process after a COW event,
1111 : * that page can be moved into the anon_vma that belongs to just that
1112 : * process, so the rmap code will not search the parent or sibling
1113 : * processes.
1114 : */
1115 0 : void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
1116 : {
1117 0 : void *anon_vma = vma->anon_vma;
1118 0 : struct folio *folio = page_folio(page);
1119 :
1120 : VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1121 : VM_BUG_ON_VMA(!anon_vma, vma);
1122 :
1123 0 : anon_vma += PAGE_MAPPING_ANON;
1124 : /*
1125 : * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1126 : * simultaneously, so a concurrent reader (eg folio_referenced()'s
1127 : * folio_test_anon()) will not see one without the other.
1128 : */
1129 0 : WRITE_ONCE(folio->mapping, anon_vma);
1130 0 : SetPageAnonExclusive(page);
1131 0 : }
1132 :
1133 : /**
1134 : * __page_set_anon_rmap - set up new anonymous rmap
1135 : * @folio: Folio which contains page.
1136 : * @page: Page to add to rmap.
1137 : * @vma: VM area to add page to.
1138 : * @address: User virtual address of the mapping
1139 : * @exclusive: the page is exclusively owned by the current process
1140 : */
1141 0 : static void __page_set_anon_rmap(struct folio *folio, struct page *page,
1142 : struct vm_area_struct *vma, unsigned long address, int exclusive)
1143 : {
1144 0 : struct anon_vma *anon_vma = vma->anon_vma;
1145 :
1146 0 : BUG_ON(!anon_vma);
1147 :
1148 0 : if (folio_test_anon(folio))
1149 : goto out;
1150 :
1151 : /*
1152 : * If the page isn't exclusively mapped into this vma,
1153 : * we must use the _oldest_ possible anon_vma for the
1154 : * page mapping!
1155 : */
1156 0 : if (!exclusive)
1157 0 : anon_vma = anon_vma->root;
1158 :
1159 : /*
1160 : * page_idle does a lockless/optimistic rmap scan on folio->mapping.
1161 : * Make sure the compiler doesn't split the stores of anon_vma and
1162 : * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
1163 : * could mistake the mapping for a struct address_space and crash.
1164 : */
1165 0 : anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1166 0 : WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
1167 0 : folio->index = linear_page_index(vma, address);
1168 : out:
1169 0 : if (exclusive)
1170 : SetPageAnonExclusive(page);
1171 0 : }
1172 :
1173 : /**
1174 : * __page_check_anon_rmap - sanity check anonymous rmap addition
1175 : * @page: the page to add the mapping to
1176 : * @vma: the vm area in which the mapping is added
1177 : * @address: the user virtual address mapped
1178 : */
1179 : static void __page_check_anon_rmap(struct page *page,
1180 : struct vm_area_struct *vma, unsigned long address)
1181 : {
1182 0 : struct folio *folio = page_folio(page);
1183 : /*
1184 : * The page's anon-rmap details (mapping and index) are guaranteed to
1185 : * be set up correctly at this point.
1186 : *
1187 : * We have exclusion against page_add_anon_rmap because the caller
1188 : * always holds the page locked.
1189 : *
1190 : * We have exclusion against page_add_new_anon_rmap because those pages
1191 : * are initially only visible via the pagetables, and the pte is locked
1192 : * over the call to page_add_new_anon_rmap.
1193 : */
1194 : VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
1195 : folio);
1196 : VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
1197 : page);
1198 : }
1199 :
1200 : /**
1201 : * page_add_anon_rmap - add pte mapping to an anonymous page
1202 : * @page: the page to add the mapping to
1203 : * @vma: the vm area in which the mapping is added
1204 : * @address: the user virtual address mapped
1205 : * @flags: the rmap flags
1206 : *
1207 : * The caller needs to hold the pte lock, and the page must be locked in
1208 : * the anon_vma case: to serialize mapping,index checking after setting,
1209 : * and to ensure that PageAnon is not being upgraded racily to PageKsm
1210 : * (but PageKsm is never downgraded to PageAnon).
1211 : */
1212 0 : void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
1213 : unsigned long address, rmap_t flags)
1214 : {
1215 0 : struct folio *folio = page_folio(page);
1216 0 : atomic_t *mapped = &folio->_nr_pages_mapped;
1217 0 : int nr = 0, nr_pmdmapped = 0;
1218 0 : bool compound = flags & RMAP_COMPOUND;
1219 0 : bool first = true;
1220 :
1221 : /* Is page being mapped by PTE? Is this its first map to be added? */
1222 0 : if (likely(!compound)) {
1223 0 : first = atomic_inc_and_test(&page->_mapcount);
1224 0 : nr = first;
1225 0 : if (first && folio_test_large(folio)) {
1226 0 : nr = atomic_inc_return_relaxed(mapped);
1227 0 : nr = (nr < COMPOUND_MAPPED);
1228 : }
1229 : } else if (folio_test_pmd_mappable(folio)) {
1230 : /* That test is redundant: it's for safety or to optimize out */
1231 :
1232 : first = atomic_inc_and_test(&folio->_entire_mapcount);
1233 : if (first) {
1234 : nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
1235 : if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
1236 : nr_pmdmapped = folio_nr_pages(folio);
1237 : nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1238 : /* Raced ahead of a remove and another add? */
1239 : if (unlikely(nr < 0))
1240 : nr = 0;
1241 : } else {
1242 : /* Raced ahead of a remove of COMPOUND_MAPPED */
1243 : nr = 0;
1244 : }
1245 : }
1246 : }
1247 :
1248 : VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
1249 : VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
1250 :
1251 : if (nr_pmdmapped)
1252 : __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped);
1253 0 : if (nr)
1254 0 : __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
1255 :
1256 0 : if (likely(!folio_test_ksm(folio))) {
1257 : /* address might be in next vma when migration races vma_merge */
1258 0 : if (first)
1259 0 : __page_set_anon_rmap(folio, page, vma, address,
1260 0 : !!(flags & RMAP_EXCLUSIVE));
1261 : else
1262 0 : __page_check_anon_rmap(page, vma, address);
1263 : }
1264 :
1265 0 : mlock_vma_folio(folio, vma, compound);
1266 0 : }
1267 :
1268 : /**
1269 : * folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
1270 : * @folio: The folio to add the mapping to.
1271 : * @vma: the vm area in which the mapping is added
1272 : * @address: the user virtual address mapped
1273 : *
1274 : * Like page_add_anon_rmap() but must only be called on *new* folios.
1275 : * This means the inc-and-test can be bypassed.
1276 : * The folio does not have to be locked.
1277 : *
1278 : * If the folio is large, it is accounted as a THP. As the folio
1279 : * is new, it's assumed to be mapped exclusively by a single process.
1280 : */
1281 0 : void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
1282 : unsigned long address)
1283 : {
1284 : int nr;
1285 :
1286 : VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1287 0 : __folio_set_swapbacked(folio);
1288 :
1289 0 : if (likely(!folio_test_pmd_mappable(folio))) {
1290 : /* increment count (starts at -1) */
1291 0 : atomic_set(&folio->_mapcount, 0);
1292 0 : nr = 1;
1293 : } else {
1294 : /* increment count (starts at -1) */
1295 : atomic_set(&folio->_entire_mapcount, 0);
1296 : atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED);
1297 : nr = folio_nr_pages(folio);
1298 : __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
1299 : }
1300 :
1301 0 : __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
1302 0 : __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
1303 0 : }
1304 :
1305 : /**
1306 : * page_add_file_rmap - add pte mapping to a file page
1307 : * @page: the page to add the mapping to
1308 : * @vma: the vm area in which the mapping is added
1309 : * @compound: charge the page as compound or small page
1310 : *
1311 : * The caller needs to hold the pte lock.
1312 : */
1313 0 : void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
1314 : bool compound)
1315 : {
1316 0 : struct folio *folio = page_folio(page);
1317 0 : atomic_t *mapped = &folio->_nr_pages_mapped;
1318 0 : int nr = 0, nr_pmdmapped = 0;
1319 : bool first;
1320 :
1321 : VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
1322 :
1323 : /* Is page being mapped by PTE? Is this its first map to be added? */
1324 0 : if (likely(!compound)) {
1325 0 : first = atomic_inc_and_test(&page->_mapcount);
1326 0 : nr = first;
1327 0 : if (first && folio_test_large(folio)) {
1328 0 : nr = atomic_inc_return_relaxed(mapped);
1329 0 : nr = (nr < COMPOUND_MAPPED);
1330 : }
1331 : } else if (folio_test_pmd_mappable(folio)) {
1332 : /* That test is redundant: it's for safety or to optimize out */
1333 :
1334 : first = atomic_inc_and_test(&folio->_entire_mapcount);
1335 : if (first) {
1336 : nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
1337 : if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
1338 : nr_pmdmapped = folio_nr_pages(folio);
1339 : nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1340 : /* Raced ahead of a remove and another add? */
1341 : if (unlikely(nr < 0))
1342 : nr = 0;
1343 : } else {
1344 : /* Raced ahead of a remove of COMPOUND_MAPPED */
1345 : nr = 0;
1346 : }
1347 : }
1348 : }
1349 :
1350 : if (nr_pmdmapped)
1351 : __lruvec_stat_mod_folio(folio, folio_test_swapbacked(folio) ?
1352 : NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped);
1353 0 : if (nr)
1354 0 : __lruvec_stat_mod_folio(folio, NR_FILE_MAPPED, nr);
1355 :
1356 0 : mlock_vma_folio(folio, vma, compound);
1357 0 : }
1358 :
1359 : /**
1360 : * page_remove_rmap - take down pte mapping from a page
1361 : * @page: page to remove mapping from
1362 : * @vma: the vm area from which the mapping is removed
1363 : * @compound: uncharge the page as compound or small page
1364 : *
1365 : * The caller needs to hold the pte lock.
1366 : */
1367 0 : void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
1368 : bool compound)
1369 : {
1370 0 : struct folio *folio = page_folio(page);
1371 0 : atomic_t *mapped = &folio->_nr_pages_mapped;
1372 0 : int nr = 0, nr_pmdmapped = 0;
1373 : bool last;
1374 : enum node_stat_item idx;
1375 :
1376 : VM_BUG_ON_PAGE(compound && !PageHead(page), page);
1377 :
1378 : /* Hugetlb pages are not counted in NR_*MAPPED */
1379 0 : if (unlikely(folio_test_hugetlb(folio))) {
1380 : /* hugetlb pages are always mapped with pmds */
1381 : atomic_dec(&folio->_entire_mapcount);
1382 : return;
1383 : }
1384 :
1385 : /* Is page being unmapped by PTE? Is this its last map to be removed? */
1386 0 : if (likely(!compound)) {
1387 0 : last = atomic_add_negative(-1, &page->_mapcount);
1388 0 : nr = last;
1389 0 : if (last && folio_test_large(folio)) {
1390 0 : nr = atomic_dec_return_relaxed(mapped);
1391 0 : nr = (nr < COMPOUND_MAPPED);
1392 : }
1393 : } else if (folio_test_pmd_mappable(folio)) {
1394 : /* That test is redundant: it's for safety or to optimize out */
1395 :
1396 : last = atomic_add_negative(-1, &folio->_entire_mapcount);
1397 : if (last) {
1398 : nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
1399 : if (likely(nr < COMPOUND_MAPPED)) {
1400 : nr_pmdmapped = folio_nr_pages(folio);
1401 : nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1402 : /* Raced ahead of another remove and an add? */
1403 : if (unlikely(nr < 0))
1404 : nr = 0;
1405 : } else {
1406 : /* An add of COMPOUND_MAPPED raced ahead */
1407 : nr = 0;
1408 : }
1409 : }
1410 : }
1411 :
1412 : if (nr_pmdmapped) {
1413 : if (folio_test_anon(folio))
1414 : idx = NR_ANON_THPS;
1415 : else if (folio_test_swapbacked(folio))
1416 : idx = NR_SHMEM_PMDMAPPED;
1417 : else
1418 : idx = NR_FILE_PMDMAPPED;
1419 : __lruvec_stat_mod_folio(folio, idx, -nr_pmdmapped);
1420 : }
1421 0 : if (nr) {
1422 0 : idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
1423 0 : __lruvec_stat_mod_folio(folio, idx, -nr);
1424 :
1425 : /*
1426 : * Queue anon THP for deferred split if at least one
1427 : * page of the folio is unmapped and at least one page
1428 : * is still mapped.
1429 : */
1430 0 : if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))
1431 : if (!compound || nr < nr_pmdmapped)
1432 : deferred_split_folio(folio);
1433 : }
1434 :
1435 : /*
1436 : * It would be tidy to reset folio_test_anon mapping when fully
1437 : * unmapped, but that might overwrite a racing page_add_anon_rmap
1438 : * which increments mapcount after us but sets mapping before us:
1439 : * so leave the reset to free_pages_prepare, and remember that
1440 : * it's only reliable while mapped.
1441 : */
1442 :
1443 0 : munlock_vma_folio(folio, vma, compound);
1444 : }
1445 :
1446 : /*
1447 : * @arg: enum ttu_flags will be passed to this argument
1448 : */
1449 0 : static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
1450 : unsigned long address, void *arg)
1451 : {
1452 0 : struct mm_struct *mm = vma->vm_mm;
1453 0 : DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1454 : pte_t pteval;
1455 : struct page *subpage;
1456 0 : bool anon_exclusive, ret = true;
1457 : struct mmu_notifier_range range;
1458 0 : enum ttu_flags flags = (enum ttu_flags)(long)arg;
1459 :
1460 : /*
1461 : * When racing against e.g. zap_pte_range() on another cpu,
1462 : * in between its ptep_get_and_clear_full() and page_remove_rmap(),
1463 : * try_to_unmap() may return before page_mapped() has become false,
1464 : * if page table locking is skipped: use TTU_SYNC to wait for that.
1465 : */
1466 0 : if (flags & TTU_SYNC)
1467 0 : pvmw.flags = PVMW_SYNC;
1468 :
1469 : if (flags & TTU_SPLIT_HUGE_PMD)
1470 : split_huge_pmd_address(vma, address, false, folio);
1471 :
1472 : /*
1473 : * For THP, we have to assume the worse case ie pmd for invalidation.
1474 : * For hugetlb, it could be much worse if we need to do pud
1475 : * invalidation in the case of pmd sharing.
1476 : *
1477 : * Note that the folio can not be freed in this function as call of
1478 : * try_to_unmap() must hold a reference on the folio.
1479 : */
1480 : range.end = vma_address_end(&pvmw);
1481 : mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
1482 : address, range.end);
1483 : if (folio_test_hugetlb(folio)) {
1484 : /*
1485 : * If sharing is possible, start and end will be adjusted
1486 : * accordingly.
1487 : */
1488 : adjust_range_if_pmd_sharing_possible(vma, &range.start,
1489 : &range.end);
1490 : }
1491 : mmu_notifier_invalidate_range_start(&range);
1492 :
1493 0 : while (page_vma_mapped_walk(&pvmw)) {
1494 : /* Unexpected PMD-mapped THP? */
1495 : VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1496 :
1497 : /*
1498 : * If the folio is in an mlock()d vma, we must not swap it out.
1499 : */
1500 0 : if (!(flags & TTU_IGNORE_MLOCK) &&
1501 0 : (vma->vm_flags & VM_LOCKED)) {
1502 : /* Restore the mlock which got missed */
1503 0 : mlock_vma_folio(folio, vma, false);
1504 0 : page_vma_mapped_walk_done(&pvmw);
1505 : ret = false;
1506 : break;
1507 : }
1508 :
1509 0 : subpage = folio_page(folio,
1510 : pte_pfn(*pvmw.pte) - folio_pfn(folio));
1511 0 : address = pvmw.address;
1512 0 : anon_exclusive = folio_test_anon(folio) &&
1513 0 : PageAnonExclusive(subpage);
1514 :
1515 0 : if (folio_test_hugetlb(folio)) {
1516 : bool anon = folio_test_anon(folio);
1517 :
1518 : /*
1519 : * The try_to_unmap() is only passed a hugetlb page
1520 : * in the case where the hugetlb page is poisoned.
1521 : */
1522 : VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
1523 : /*
1524 : * huge_pmd_unshare may unmap an entire PMD page.
1525 : * There is no way of knowing exactly which PMDs may
1526 : * be cached for this mm, so we must flush them all.
1527 : * start/end were already adjusted above to cover this
1528 : * range.
1529 : */
1530 : flush_cache_range(vma, range.start, range.end);
1531 :
1532 : /*
1533 : * To call huge_pmd_unshare, i_mmap_rwsem must be
1534 : * held in write mode. Caller needs to explicitly
1535 : * do this outside rmap routines.
1536 : *
1537 : * We also must hold hugetlb vma_lock in write mode.
1538 : * Lock order dictates acquiring vma_lock BEFORE
1539 : * i_mmap_rwsem. We can only try lock here and fail
1540 : * if unsuccessful.
1541 : */
1542 : if (!anon) {
1543 : VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1544 : if (!hugetlb_vma_trylock_write(vma)) {
1545 : page_vma_mapped_walk_done(&pvmw);
1546 : ret = false;
1547 : break;
1548 : }
1549 : if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
1550 : hugetlb_vma_unlock_write(vma);
1551 : flush_tlb_range(vma,
1552 : range.start, range.end);
1553 : mmu_notifier_invalidate_range(mm,
1554 : range.start, range.end);
1555 : /*
1556 : * The ref count of the PMD page was
1557 : * dropped which is part of the way map
1558 : * counting is done for shared PMDs.
1559 : * Return 'true' here. When there is
1560 : * no other sharing, huge_pmd_unshare
1561 : * returns false and we will unmap the
1562 : * actual page and drop map count
1563 : * to zero.
1564 : */
1565 : page_vma_mapped_walk_done(&pvmw);
1566 : break;
1567 : }
1568 : hugetlb_vma_unlock_write(vma);
1569 : }
1570 : pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
1571 : } else {
1572 0 : flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
1573 : /* Nuke the page table entry. */
1574 0 : if (should_defer_flush(mm, flags)) {
1575 : /*
1576 : * We clear the PTE but do not flush so potentially
1577 : * a remote CPU could still be writing to the folio.
1578 : * If the entry was previously clean then the
1579 : * architecture must guarantee that a clear->dirty
1580 : * transition on a cached TLB entry is written through
1581 : * and traps if the PTE is unmapped.
1582 : */
1583 : pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1584 :
1585 : set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
1586 : } else {
1587 0 : pteval = ptep_clear_flush(vma, address, pvmw.pte);
1588 : }
1589 : }
1590 :
1591 : /*
1592 : * Now the pte is cleared. If this pte was uffd-wp armed,
1593 : * we may want to replace a none pte with a marker pte if
1594 : * it's file-backed, so we don't lose the tracking info.
1595 : */
1596 0 : pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval);
1597 :
1598 : /* Set the dirty flag on the folio now the pte is gone. */
1599 0 : if (pte_dirty(pteval))
1600 0 : folio_mark_dirty(folio);
1601 :
1602 : /* Update high watermark before we lower rss */
1603 0 : update_hiwater_rss(mm);
1604 :
1605 0 : if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
1606 : pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
1607 : if (folio_test_hugetlb(folio)) {
1608 : hugetlb_count_sub(folio_nr_pages(folio), mm);
1609 : set_huge_pte_at(mm, address, pvmw.pte, pteval);
1610 : } else {
1611 : dec_mm_counter(mm, mm_counter(&folio->page));
1612 : set_pte_at(mm, address, pvmw.pte, pteval);
1613 : }
1614 :
1615 0 : } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
1616 : /*
1617 : * The guest indicated that the page content is of no
1618 : * interest anymore. Simply discard the pte, vmscan
1619 : * will take care of the rest.
1620 : * A future reference will then fault in a new zero
1621 : * page. When userfaultfd is active, we must not drop
1622 : * this page though, as its main user (postcopy
1623 : * migration) will not expect userfaults on already
1624 : * copied pages.
1625 : */
1626 : dec_mm_counter(mm, mm_counter(&folio->page));
1627 : /* We have to invalidate as we cleared the pte */
1628 : mmu_notifier_invalidate_range(mm, address,
1629 : address + PAGE_SIZE);
1630 0 : } else if (folio_test_anon(folio)) {
1631 0 : swp_entry_t entry = { .val = page_private(subpage) };
1632 : pte_t swp_pte;
1633 : /*
1634 : * Store the swap location in the pte.
1635 : * See handle_pte_fault() ...
1636 : */
1637 0 : if (unlikely(folio_test_swapbacked(folio) !=
1638 : folio_test_swapcache(folio))) {
1639 0 : WARN_ON_ONCE(1);
1640 0 : ret = false;
1641 : /* We have to invalidate as we cleared the pte */
1642 0 : mmu_notifier_invalidate_range(mm, address,
1643 : address + PAGE_SIZE);
1644 0 : page_vma_mapped_walk_done(&pvmw);
1645 : break;
1646 : }
1647 :
1648 : /* MADV_FREE page check */
1649 0 : if (!folio_test_swapbacked(folio)) {
1650 : int ref_count, map_count;
1651 :
1652 : /*
1653 : * Synchronize with gup_pte_range():
1654 : * - clear PTE; barrier; read refcount
1655 : * - inc refcount; barrier; read PTE
1656 : */
1657 0 : smp_mb();
1658 :
1659 0 : ref_count = folio_ref_count(folio);
1660 0 : map_count = folio_mapcount(folio);
1661 :
1662 : /*
1663 : * Order reads for page refcount and dirty flag
1664 : * (see comments in __remove_mapping()).
1665 : */
1666 0 : smp_rmb();
1667 :
1668 : /*
1669 : * The only page refs must be one from isolation
1670 : * plus the rmap(s) (dropped by discard:).
1671 : */
1672 0 : if (ref_count == 1 + map_count &&
1673 0 : !folio_test_dirty(folio)) {
1674 : /* Invalidate as we cleared the pte */
1675 0 : mmu_notifier_invalidate_range(mm,
1676 : address, address + PAGE_SIZE);
1677 0 : dec_mm_counter(mm, MM_ANONPAGES);
1678 0 : goto discard;
1679 : }
1680 :
1681 : /*
1682 : * If the folio was redirtied, it cannot be
1683 : * discarded. Remap the page to page table.
1684 : */
1685 0 : set_pte_at(mm, address, pvmw.pte, pteval);
1686 0 : folio_set_swapbacked(folio);
1687 0 : ret = false;
1688 0 : page_vma_mapped_walk_done(&pvmw);
1689 : break;
1690 : }
1691 :
1692 0 : if (swap_duplicate(entry) < 0) {
1693 0 : set_pte_at(mm, address, pvmw.pte, pteval);
1694 0 : ret = false;
1695 0 : page_vma_mapped_walk_done(&pvmw);
1696 : break;
1697 : }
1698 0 : if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1699 : swap_free(entry);
1700 : set_pte_at(mm, address, pvmw.pte, pteval);
1701 : ret = false;
1702 : page_vma_mapped_walk_done(&pvmw);
1703 : break;
1704 : }
1705 :
1706 : /* See page_try_share_anon_rmap(): clear PTE first. */
1707 0 : if (anon_exclusive &&
1708 0 : page_try_share_anon_rmap(subpage)) {
1709 0 : swap_free(entry);
1710 0 : set_pte_at(mm, address, pvmw.pte, pteval);
1711 0 : ret = false;
1712 0 : page_vma_mapped_walk_done(&pvmw);
1713 : break;
1714 : }
1715 0 : if (list_empty(&mm->mmlist)) {
1716 0 : spin_lock(&mmlist_lock);
1717 0 : if (list_empty(&mm->mmlist))
1718 0 : list_add(&mm->mmlist, &init_mm.mmlist);
1719 : spin_unlock(&mmlist_lock);
1720 : }
1721 0 : dec_mm_counter(mm, MM_ANONPAGES);
1722 0 : inc_mm_counter(mm, MM_SWAPENTS);
1723 0 : swp_pte = swp_entry_to_pte(entry);
1724 0 : if (anon_exclusive)
1725 : swp_pte = pte_swp_mkexclusive(swp_pte);
1726 0 : if (pte_soft_dirty(pteval))
1727 : swp_pte = pte_swp_mksoft_dirty(swp_pte);
1728 : if (pte_uffd_wp(pteval))
1729 : swp_pte = pte_swp_mkuffd_wp(swp_pte);
1730 0 : set_pte_at(mm, address, pvmw.pte, swp_pte);
1731 : /* Invalidate as we cleared the pte */
1732 0 : mmu_notifier_invalidate_range(mm, address,
1733 : address + PAGE_SIZE);
1734 : } else {
1735 : /*
1736 : * This is a locked file-backed folio,
1737 : * so it cannot be removed from the page
1738 : * cache and replaced by a new folio before
1739 : * mmu_notifier_invalidate_range_end, so no
1740 : * concurrent thread might update its page table
1741 : * to point at a new folio while a device is
1742 : * still using this folio.
1743 : *
1744 : * See Documentation/mm/mmu_notifier.rst
1745 : */
1746 0 : dec_mm_counter(mm, mm_counter_file(&folio->page));
1747 : }
1748 : discard:
1749 : /*
1750 : * No need to call mmu_notifier_invalidate_range() it has be
1751 : * done above for all cases requiring it to happen under page
1752 : * table lock before mmu_notifier_invalidate_range_end()
1753 : *
1754 : * See Documentation/mm/mmu_notifier.rst
1755 : */
1756 0 : page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
1757 0 : if (vma->vm_flags & VM_LOCKED)
1758 0 : mlock_drain_local();
1759 : folio_put(folio);
1760 : }
1761 :
1762 0 : mmu_notifier_invalidate_range_end(&range);
1763 :
1764 0 : return ret;
1765 : }
1766 :
1767 0 : static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1768 : {
1769 0 : return vma_is_temporary_stack(vma);
1770 : }
1771 :
1772 0 : static int folio_not_mapped(struct folio *folio)
1773 : {
1774 0 : return !folio_mapped(folio);
1775 : }
1776 :
1777 : /**
1778 : * try_to_unmap - Try to remove all page table mappings to a folio.
1779 : * @folio: The folio to unmap.
1780 : * @flags: action and flags
1781 : *
1782 : * Tries to remove all the page table entries which are mapping this
1783 : * folio. It is the caller's responsibility to check if the folio is
1784 : * still mapped if needed (use TTU_SYNC to prevent accounting races).
1785 : *
1786 : * Context: Caller must hold the folio lock.
1787 : */
1788 0 : void try_to_unmap(struct folio *folio, enum ttu_flags flags)
1789 : {
1790 0 : struct rmap_walk_control rwc = {
1791 : .rmap_one = try_to_unmap_one,
1792 0 : .arg = (void *)flags,
1793 : .done = folio_not_mapped,
1794 : .anon_lock = folio_lock_anon_vma_read,
1795 : };
1796 :
1797 0 : if (flags & TTU_RMAP_LOCKED)
1798 0 : rmap_walk_locked(folio, &rwc);
1799 : else
1800 0 : rmap_walk(folio, &rwc);
1801 0 : }
1802 :
1803 : /*
1804 : * @arg: enum ttu_flags will be passed to this argument.
1805 : *
1806 : * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
1807 : * containing migration entries.
1808 : */
1809 0 : static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
1810 : unsigned long address, void *arg)
1811 : {
1812 0 : struct mm_struct *mm = vma->vm_mm;
1813 0 : DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1814 : pte_t pteval;
1815 : struct page *subpage;
1816 0 : bool anon_exclusive, ret = true;
1817 : struct mmu_notifier_range range;
1818 0 : enum ttu_flags flags = (enum ttu_flags)(long)arg;
1819 :
1820 : /*
1821 : * When racing against e.g. zap_pte_range() on another cpu,
1822 : * in between its ptep_get_and_clear_full() and page_remove_rmap(),
1823 : * try_to_migrate() may return before page_mapped() has become false,
1824 : * if page table locking is skipped: use TTU_SYNC to wait for that.
1825 : */
1826 0 : if (flags & TTU_SYNC)
1827 0 : pvmw.flags = PVMW_SYNC;
1828 :
1829 : /*
1830 : * unmap_page() in mm/huge_memory.c is the only user of migration with
1831 : * TTU_SPLIT_HUGE_PMD and it wants to freeze.
1832 : */
1833 : if (flags & TTU_SPLIT_HUGE_PMD)
1834 : split_huge_pmd_address(vma, address, true, folio);
1835 :
1836 : /*
1837 : * For THP, we have to assume the worse case ie pmd for invalidation.
1838 : * For hugetlb, it could be much worse if we need to do pud
1839 : * invalidation in the case of pmd sharing.
1840 : *
1841 : * Note that the page can not be free in this function as call of
1842 : * try_to_unmap() must hold a reference on the page.
1843 : */
1844 : range.end = vma_address_end(&pvmw);
1845 : mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
1846 : address, range.end);
1847 : if (folio_test_hugetlb(folio)) {
1848 : /*
1849 : * If sharing is possible, start and end will be adjusted
1850 : * accordingly.
1851 : */
1852 : adjust_range_if_pmd_sharing_possible(vma, &range.start,
1853 : &range.end);
1854 : }
1855 : mmu_notifier_invalidate_range_start(&range);
1856 :
1857 0 : while (page_vma_mapped_walk(&pvmw)) {
1858 : #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1859 : /* PMD-mapped THP migration entry */
1860 : if (!pvmw.pte) {
1861 : subpage = folio_page(folio,
1862 : pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
1863 : VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
1864 : !folio_test_pmd_mappable(folio), folio);
1865 :
1866 : if (set_pmd_migration_entry(&pvmw, subpage)) {
1867 : ret = false;
1868 : page_vma_mapped_walk_done(&pvmw);
1869 : break;
1870 : }
1871 : continue;
1872 : }
1873 : #endif
1874 :
1875 : /* Unexpected PMD-mapped THP? */
1876 : VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1877 :
1878 0 : if (folio_is_zone_device(folio)) {
1879 : /*
1880 : * Our PTE is a non-present device exclusive entry and
1881 : * calculating the subpage as for the common case would
1882 : * result in an invalid pointer.
1883 : *
1884 : * Since only PAGE_SIZE pages can currently be
1885 : * migrated, just set it to page. This will need to be
1886 : * changed when hugepage migrations to device private
1887 : * memory are supported.
1888 : */
1889 : VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
1890 : subpage = &folio->page;
1891 : } else {
1892 0 : subpage = folio_page(folio,
1893 : pte_pfn(*pvmw.pte) - folio_pfn(folio));
1894 : }
1895 0 : address = pvmw.address;
1896 0 : anon_exclusive = folio_test_anon(folio) &&
1897 0 : PageAnonExclusive(subpage);
1898 :
1899 0 : if (folio_test_hugetlb(folio)) {
1900 : bool anon = folio_test_anon(folio);
1901 :
1902 : /*
1903 : * huge_pmd_unshare may unmap an entire PMD page.
1904 : * There is no way of knowing exactly which PMDs may
1905 : * be cached for this mm, so we must flush them all.
1906 : * start/end were already adjusted above to cover this
1907 : * range.
1908 : */
1909 : flush_cache_range(vma, range.start, range.end);
1910 :
1911 : /*
1912 : * To call huge_pmd_unshare, i_mmap_rwsem must be
1913 : * held in write mode. Caller needs to explicitly
1914 : * do this outside rmap routines.
1915 : *
1916 : * We also must hold hugetlb vma_lock in write mode.
1917 : * Lock order dictates acquiring vma_lock BEFORE
1918 : * i_mmap_rwsem. We can only try lock here and
1919 : * fail if unsuccessful.
1920 : */
1921 : if (!anon) {
1922 : VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1923 : if (!hugetlb_vma_trylock_write(vma)) {
1924 : page_vma_mapped_walk_done(&pvmw);
1925 : ret = false;
1926 : break;
1927 : }
1928 : if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
1929 : hugetlb_vma_unlock_write(vma);
1930 : flush_tlb_range(vma,
1931 : range.start, range.end);
1932 : mmu_notifier_invalidate_range(mm,
1933 : range.start, range.end);
1934 :
1935 : /*
1936 : * The ref count of the PMD page was
1937 : * dropped which is part of the way map
1938 : * counting is done for shared PMDs.
1939 : * Return 'true' here. When there is
1940 : * no other sharing, huge_pmd_unshare
1941 : * returns false and we will unmap the
1942 : * actual page and drop map count
1943 : * to zero.
1944 : */
1945 : page_vma_mapped_walk_done(&pvmw);
1946 : break;
1947 : }
1948 : hugetlb_vma_unlock_write(vma);
1949 : }
1950 : /* Nuke the hugetlb page table entry */
1951 : pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
1952 : } else {
1953 0 : flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
1954 : /* Nuke the page table entry. */
1955 0 : if (should_defer_flush(mm, flags)) {
1956 : /*
1957 : * We clear the PTE but do not flush so potentially
1958 : * a remote CPU could still be writing to the folio.
1959 : * If the entry was previously clean then the
1960 : * architecture must guarantee that a clear->dirty
1961 : * transition on a cached TLB entry is written through
1962 : * and traps if the PTE is unmapped.
1963 : */
1964 : pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1965 :
1966 : set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
1967 : } else {
1968 0 : pteval = ptep_clear_flush(vma, address, pvmw.pte);
1969 : }
1970 : }
1971 :
1972 : /* Set the dirty flag on the folio now the pte is gone. */
1973 0 : if (pte_dirty(pteval))
1974 0 : folio_mark_dirty(folio);
1975 :
1976 : /* Update high watermark before we lower rss */
1977 0 : update_hiwater_rss(mm);
1978 :
1979 0 : if (folio_is_device_private(folio)) {
1980 : unsigned long pfn = folio_pfn(folio);
1981 : swp_entry_t entry;
1982 : pte_t swp_pte;
1983 :
1984 : if (anon_exclusive)
1985 : BUG_ON(page_try_share_anon_rmap(subpage));
1986 :
1987 : /*
1988 : * Store the pfn of the page in a special migration
1989 : * pte. do_swap_page() will wait until the migration
1990 : * pte is removed and then restart fault handling.
1991 : */
1992 : entry = pte_to_swp_entry(pteval);
1993 : if (is_writable_device_private_entry(entry))
1994 : entry = make_writable_migration_entry(pfn);
1995 : else if (anon_exclusive)
1996 : entry = make_readable_exclusive_migration_entry(pfn);
1997 : else
1998 : entry = make_readable_migration_entry(pfn);
1999 : swp_pte = swp_entry_to_pte(entry);
2000 :
2001 : /*
2002 : * pteval maps a zone device page and is therefore
2003 : * a swap pte.
2004 : */
2005 : if (pte_swp_soft_dirty(pteval))
2006 : swp_pte = pte_swp_mksoft_dirty(swp_pte);
2007 : if (pte_swp_uffd_wp(pteval))
2008 : swp_pte = pte_swp_mkuffd_wp(swp_pte);
2009 : set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
2010 : trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
2011 : compound_order(&folio->page));
2012 : /*
2013 : * No need to invalidate here it will synchronize on
2014 : * against the special swap migration pte.
2015 : */
2016 0 : } else if (PageHWPoison(subpage)) {
2017 : pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
2018 : if (folio_test_hugetlb(folio)) {
2019 : hugetlb_count_sub(folio_nr_pages(folio), mm);
2020 : set_huge_pte_at(mm, address, pvmw.pte, pteval);
2021 : } else {
2022 : dec_mm_counter(mm, mm_counter(&folio->page));
2023 : set_pte_at(mm, address, pvmw.pte, pteval);
2024 : }
2025 :
2026 0 : } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
2027 : /*
2028 : * The guest indicated that the page content is of no
2029 : * interest anymore. Simply discard the pte, vmscan
2030 : * will take care of the rest.
2031 : * A future reference will then fault in a new zero
2032 : * page. When userfaultfd is active, we must not drop
2033 : * this page though, as its main user (postcopy
2034 : * migration) will not expect userfaults on already
2035 : * copied pages.
2036 : */
2037 : dec_mm_counter(mm, mm_counter(&folio->page));
2038 : /* We have to invalidate as we cleared the pte */
2039 : mmu_notifier_invalidate_range(mm, address,
2040 : address + PAGE_SIZE);
2041 : } else {
2042 : swp_entry_t entry;
2043 : pte_t swp_pte;
2044 :
2045 0 : if (arch_unmap_one(mm, vma, address, pteval) < 0) {
2046 : if (folio_test_hugetlb(folio))
2047 : set_huge_pte_at(mm, address, pvmw.pte, pteval);
2048 : else
2049 : set_pte_at(mm, address, pvmw.pte, pteval);
2050 : ret = false;
2051 : page_vma_mapped_walk_done(&pvmw);
2052 : break;
2053 : }
2054 : VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
2055 : !anon_exclusive, subpage);
2056 :
2057 : /* See page_try_share_anon_rmap(): clear PTE first. */
2058 0 : if (anon_exclusive &&
2059 0 : page_try_share_anon_rmap(subpage)) {
2060 0 : if (folio_test_hugetlb(folio))
2061 : set_huge_pte_at(mm, address, pvmw.pte, pteval);
2062 : else
2063 0 : set_pte_at(mm, address, pvmw.pte, pteval);
2064 0 : ret = false;
2065 0 : page_vma_mapped_walk_done(&pvmw);
2066 : break;
2067 : }
2068 :
2069 : /*
2070 : * Store the pfn of the page in a special migration
2071 : * pte. do_swap_page() will wait until the migration
2072 : * pte is removed and then restart fault handling.
2073 : */
2074 0 : if (pte_write(pteval))
2075 0 : entry = make_writable_migration_entry(
2076 0 : page_to_pfn(subpage));
2077 0 : else if (anon_exclusive)
2078 0 : entry = make_readable_exclusive_migration_entry(
2079 0 : page_to_pfn(subpage));
2080 : else
2081 0 : entry = make_readable_migration_entry(
2082 0 : page_to_pfn(subpage));
2083 0 : if (pte_young(pteval))
2084 : entry = make_migration_entry_young(entry);
2085 0 : if (pte_dirty(pteval))
2086 : entry = make_migration_entry_dirty(entry);
2087 0 : swp_pte = swp_entry_to_pte(entry);
2088 0 : if (pte_soft_dirty(pteval))
2089 : swp_pte = pte_swp_mksoft_dirty(swp_pte);
2090 : if (pte_uffd_wp(pteval))
2091 : swp_pte = pte_swp_mkuffd_wp(swp_pte);
2092 0 : if (folio_test_hugetlb(folio))
2093 : set_huge_pte_at(mm, address, pvmw.pte, swp_pte);
2094 : else
2095 0 : set_pte_at(mm, address, pvmw.pte, swp_pte);
2096 0 : trace_set_migration_pte(address, pte_val(swp_pte),
2097 0 : compound_order(&folio->page));
2098 : /*
2099 : * No need to invalidate here it will synchronize on
2100 : * against the special swap migration pte.
2101 : */
2102 : }
2103 :
2104 : /*
2105 : * No need to call mmu_notifier_invalidate_range() it has be
2106 : * done above for all cases requiring it to happen under page
2107 : * table lock before mmu_notifier_invalidate_range_end()
2108 : *
2109 : * See Documentation/mm/mmu_notifier.rst
2110 : */
2111 0 : page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
2112 0 : if (vma->vm_flags & VM_LOCKED)
2113 0 : mlock_drain_local();
2114 : folio_put(folio);
2115 : }
2116 :
2117 0 : mmu_notifier_invalidate_range_end(&range);
2118 :
2119 0 : return ret;
2120 : }
2121 :
2122 : /**
2123 : * try_to_migrate - try to replace all page table mappings with swap entries
2124 : * @folio: the folio to replace page table entries for
2125 : * @flags: action and flags
2126 : *
2127 : * Tries to remove all the page table entries which are mapping this folio and
2128 : * replace them with special swap entries. Caller must hold the folio lock.
2129 : */
2130 0 : void try_to_migrate(struct folio *folio, enum ttu_flags flags)
2131 : {
2132 0 : struct rmap_walk_control rwc = {
2133 : .rmap_one = try_to_migrate_one,
2134 0 : .arg = (void *)flags,
2135 : .done = folio_not_mapped,
2136 : .anon_lock = folio_lock_anon_vma_read,
2137 : };
2138 :
2139 : /*
2140 : * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
2141 : * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
2142 : */
2143 0 : if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2144 : TTU_SYNC | TTU_BATCH_FLUSH)))
2145 0 : return;
2146 :
2147 0 : if (folio_is_zone_device(folio) &&
2148 : (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
2149 : return;
2150 :
2151 : /*
2152 : * During exec, a temporary VMA is setup and later moved.
2153 : * The VMA is moved under the anon_vma lock but not the
2154 : * page tables leading to a race where migration cannot
2155 : * find the migration ptes. Rather than increasing the
2156 : * locking requirements of exec(), migration skips
2157 : * temporary VMAs until after exec() completes.
2158 : */
2159 0 : if (!folio_test_ksm(folio) && folio_test_anon(folio))
2160 0 : rwc.invalid_vma = invalid_migration_vma;
2161 :
2162 0 : if (flags & TTU_RMAP_LOCKED)
2163 0 : rmap_walk_locked(folio, &rwc);
2164 : else
2165 0 : rmap_walk(folio, &rwc);
2166 : }
2167 :
2168 : #ifdef CONFIG_DEVICE_PRIVATE
2169 : struct make_exclusive_args {
2170 : struct mm_struct *mm;
2171 : unsigned long address;
2172 : void *owner;
2173 : bool valid;
2174 : };
2175 :
2176 : static bool page_make_device_exclusive_one(struct folio *folio,
2177 : struct vm_area_struct *vma, unsigned long address, void *priv)
2178 : {
2179 : struct mm_struct *mm = vma->vm_mm;
2180 : DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
2181 : struct make_exclusive_args *args = priv;
2182 : pte_t pteval;
2183 : struct page *subpage;
2184 : bool ret = true;
2185 : struct mmu_notifier_range range;
2186 : swp_entry_t entry;
2187 : pte_t swp_pte;
2188 :
2189 : mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
2190 : vma->vm_mm, address, min(vma->vm_end,
2191 : address + folio_size(folio)),
2192 : args->owner);
2193 : mmu_notifier_invalidate_range_start(&range);
2194 :
2195 : while (page_vma_mapped_walk(&pvmw)) {
2196 : /* Unexpected PMD-mapped THP? */
2197 : VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2198 :
2199 : if (!pte_present(*pvmw.pte)) {
2200 : ret = false;
2201 : page_vma_mapped_walk_done(&pvmw);
2202 : break;
2203 : }
2204 :
2205 : subpage = folio_page(folio,
2206 : pte_pfn(*pvmw.pte) - folio_pfn(folio));
2207 : address = pvmw.address;
2208 :
2209 : /* Nuke the page table entry. */
2210 : flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
2211 : pteval = ptep_clear_flush(vma, address, pvmw.pte);
2212 :
2213 : /* Set the dirty flag on the folio now the pte is gone. */
2214 : if (pte_dirty(pteval))
2215 : folio_mark_dirty(folio);
2216 :
2217 : /*
2218 : * Check that our target page is still mapped at the expected
2219 : * address.
2220 : */
2221 : if (args->mm == mm && args->address == address &&
2222 : pte_write(pteval))
2223 : args->valid = true;
2224 :
2225 : /*
2226 : * Store the pfn of the page in a special migration
2227 : * pte. do_swap_page() will wait until the migration
2228 : * pte is removed and then restart fault handling.
2229 : */
2230 : if (pte_write(pteval))
2231 : entry = make_writable_device_exclusive_entry(
2232 : page_to_pfn(subpage));
2233 : else
2234 : entry = make_readable_device_exclusive_entry(
2235 : page_to_pfn(subpage));
2236 : swp_pte = swp_entry_to_pte(entry);
2237 : if (pte_soft_dirty(pteval))
2238 : swp_pte = pte_swp_mksoft_dirty(swp_pte);
2239 : if (pte_uffd_wp(pteval))
2240 : swp_pte = pte_swp_mkuffd_wp(swp_pte);
2241 :
2242 : set_pte_at(mm, address, pvmw.pte, swp_pte);
2243 :
2244 : /*
2245 : * There is a reference on the page for the swap entry which has
2246 : * been removed, so shouldn't take another.
2247 : */
2248 : page_remove_rmap(subpage, vma, false);
2249 : }
2250 :
2251 : mmu_notifier_invalidate_range_end(&range);
2252 :
2253 : return ret;
2254 : }
2255 :
2256 : /**
2257 : * folio_make_device_exclusive - Mark the folio exclusively owned by a device.
2258 : * @folio: The folio to replace page table entries for.
2259 : * @mm: The mm_struct where the folio is expected to be mapped.
2260 : * @address: Address where the folio is expected to be mapped.
2261 : * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
2262 : *
2263 : * Tries to remove all the page table entries which are mapping this
2264 : * folio and replace them with special device exclusive swap entries to
2265 : * grant a device exclusive access to the folio.
2266 : *
2267 : * Context: Caller must hold the folio lock.
2268 : * Return: false if the page is still mapped, or if it could not be unmapped
2269 : * from the expected address. Otherwise returns true (success).
2270 : */
2271 : static bool folio_make_device_exclusive(struct folio *folio,
2272 : struct mm_struct *mm, unsigned long address, void *owner)
2273 : {
2274 : struct make_exclusive_args args = {
2275 : .mm = mm,
2276 : .address = address,
2277 : .owner = owner,
2278 : .valid = false,
2279 : };
2280 : struct rmap_walk_control rwc = {
2281 : .rmap_one = page_make_device_exclusive_one,
2282 : .done = folio_not_mapped,
2283 : .anon_lock = folio_lock_anon_vma_read,
2284 : .arg = &args,
2285 : };
2286 :
2287 : /*
2288 : * Restrict to anonymous folios for now to avoid potential writeback
2289 : * issues.
2290 : */
2291 : if (!folio_test_anon(folio))
2292 : return false;
2293 :
2294 : rmap_walk(folio, &rwc);
2295 :
2296 : return args.valid && !folio_mapcount(folio);
2297 : }
2298 :
2299 : /**
2300 : * make_device_exclusive_range() - Mark a range for exclusive use by a device
2301 : * @mm: mm_struct of associated target process
2302 : * @start: start of the region to mark for exclusive device access
2303 : * @end: end address of region
2304 : * @pages: returns the pages which were successfully marked for exclusive access
2305 : * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
2306 : *
2307 : * Returns: number of pages found in the range by GUP. A page is marked for
2308 : * exclusive access only if the page pointer is non-NULL.
2309 : *
2310 : * This function finds ptes mapping page(s) to the given address range, locks
2311 : * them and replaces mappings with special swap entries preventing userspace CPU
2312 : * access. On fault these entries are replaced with the original mapping after
2313 : * calling MMU notifiers.
2314 : *
2315 : * A driver using this to program access from a device must use a mmu notifier
2316 : * critical section to hold a device specific lock during programming. Once
2317 : * programming is complete it should drop the page lock and reference after
2318 : * which point CPU access to the page will revoke the exclusive access.
2319 : */
2320 : int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
2321 : unsigned long end, struct page **pages,
2322 : void *owner)
2323 : {
2324 : long npages = (end - start) >> PAGE_SHIFT;
2325 : long i;
2326 :
2327 : npages = get_user_pages_remote(mm, start, npages,
2328 : FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
2329 : pages, NULL, NULL);
2330 : if (npages < 0)
2331 : return npages;
2332 :
2333 : for (i = 0; i < npages; i++, start += PAGE_SIZE) {
2334 : struct folio *folio = page_folio(pages[i]);
2335 : if (PageTail(pages[i]) || !folio_trylock(folio)) {
2336 : folio_put(folio);
2337 : pages[i] = NULL;
2338 : continue;
2339 : }
2340 :
2341 : if (!folio_make_device_exclusive(folio, mm, start, owner)) {
2342 : folio_unlock(folio);
2343 : folio_put(folio);
2344 : pages[i] = NULL;
2345 : }
2346 : }
2347 :
2348 : return npages;
2349 : }
2350 : EXPORT_SYMBOL_GPL(make_device_exclusive_range);
2351 : #endif
2352 :
2353 0 : void __put_anon_vma(struct anon_vma *anon_vma)
2354 : {
2355 0 : struct anon_vma *root = anon_vma->root;
2356 :
2357 0 : anon_vma_free(anon_vma);
2358 0 : if (root != anon_vma && atomic_dec_and_test(&root->refcount))
2359 0 : anon_vma_free(root);
2360 0 : }
2361 :
2362 0 : static struct anon_vma *rmap_walk_anon_lock(struct folio *folio,
2363 : struct rmap_walk_control *rwc)
2364 : {
2365 : struct anon_vma *anon_vma;
2366 :
2367 0 : if (rwc->anon_lock)
2368 0 : return rwc->anon_lock(folio, rwc);
2369 :
2370 : /*
2371 : * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
2372 : * because that depends on page_mapped(); but not all its usages
2373 : * are holding mmap_lock. Users without mmap_lock are required to
2374 : * take a reference count to prevent the anon_vma disappearing
2375 : */
2376 0 : anon_vma = folio_anon_vma(folio);
2377 0 : if (!anon_vma)
2378 : return NULL;
2379 :
2380 0 : if (anon_vma_trylock_read(anon_vma))
2381 : goto out;
2382 :
2383 0 : if (rwc->try_lock) {
2384 0 : anon_vma = NULL;
2385 0 : rwc->contended = true;
2386 0 : goto out;
2387 : }
2388 :
2389 0 : anon_vma_lock_read(anon_vma);
2390 : out:
2391 : return anon_vma;
2392 : }
2393 :
2394 : /*
2395 : * rmap_walk_anon - do something to anonymous page using the object-based
2396 : * rmap method
2397 : * @page: the page to be handled
2398 : * @rwc: control variable according to each walk type
2399 : *
2400 : * Find all the mappings of a page using the mapping pointer and the vma chains
2401 : * contained in the anon_vma struct it points to.
2402 : */
2403 0 : static void rmap_walk_anon(struct folio *folio,
2404 : struct rmap_walk_control *rwc, bool locked)
2405 : {
2406 : struct anon_vma *anon_vma;
2407 : pgoff_t pgoff_start, pgoff_end;
2408 : struct anon_vma_chain *avc;
2409 :
2410 0 : if (locked) {
2411 0 : anon_vma = folio_anon_vma(folio);
2412 : /* anon_vma disappear under us? */
2413 : VM_BUG_ON_FOLIO(!anon_vma, folio);
2414 : } else {
2415 0 : anon_vma = rmap_walk_anon_lock(folio, rwc);
2416 : }
2417 0 : if (!anon_vma)
2418 : return;
2419 :
2420 0 : pgoff_start = folio_pgoff(folio);
2421 0 : pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2422 0 : anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
2423 : pgoff_start, pgoff_end) {
2424 0 : struct vm_area_struct *vma = avc->vma;
2425 0 : unsigned long address = vma_address(&folio->page, vma);
2426 :
2427 : VM_BUG_ON_VMA(address == -EFAULT, vma);
2428 0 : cond_resched();
2429 :
2430 0 : if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2431 0 : continue;
2432 :
2433 0 : if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2434 : break;
2435 0 : if (rwc->done && rwc->done(folio))
2436 : break;
2437 : }
2438 :
2439 0 : if (!locked)
2440 0 : anon_vma_unlock_read(anon_vma);
2441 : }
2442 :
2443 : /*
2444 : * rmap_walk_file - do something to file page using the object-based rmap method
2445 : * @page: the page to be handled
2446 : * @rwc: control variable according to each walk type
2447 : *
2448 : * Find all the mappings of a page using the mapping pointer and the vma chains
2449 : * contained in the address_space struct it points to.
2450 : */
2451 0 : static void rmap_walk_file(struct folio *folio,
2452 : struct rmap_walk_control *rwc, bool locked)
2453 : {
2454 0 : struct address_space *mapping = folio_mapping(folio);
2455 : pgoff_t pgoff_start, pgoff_end;
2456 : struct vm_area_struct *vma;
2457 :
2458 : /*
2459 : * The page lock not only makes sure that page->mapping cannot
2460 : * suddenly be NULLified by truncation, it makes sure that the
2461 : * structure at mapping cannot be freed and reused yet,
2462 : * so we can safely take mapping->i_mmap_rwsem.
2463 : */
2464 : VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2465 :
2466 0 : if (!mapping)
2467 : return;
2468 :
2469 0 : pgoff_start = folio_pgoff(folio);
2470 0 : pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2471 0 : if (!locked) {
2472 0 : if (i_mmap_trylock_read(mapping))
2473 : goto lookup;
2474 :
2475 0 : if (rwc->try_lock) {
2476 0 : rwc->contended = true;
2477 0 : return;
2478 : }
2479 :
2480 : i_mmap_lock_read(mapping);
2481 : }
2482 : lookup:
2483 0 : vma_interval_tree_foreach(vma, &mapping->i_mmap,
2484 : pgoff_start, pgoff_end) {
2485 0 : unsigned long address = vma_address(&folio->page, vma);
2486 :
2487 : VM_BUG_ON_VMA(address == -EFAULT, vma);
2488 0 : cond_resched();
2489 :
2490 0 : if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2491 0 : continue;
2492 :
2493 0 : if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2494 : goto done;
2495 0 : if (rwc->done && rwc->done(folio))
2496 : goto done;
2497 : }
2498 :
2499 : done:
2500 0 : if (!locked)
2501 : i_mmap_unlock_read(mapping);
2502 : }
2503 :
2504 0 : void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
2505 : {
2506 0 : if (unlikely(folio_test_ksm(folio)))
2507 : rmap_walk_ksm(folio, rwc);
2508 0 : else if (folio_test_anon(folio))
2509 0 : rmap_walk_anon(folio, rwc, false);
2510 : else
2511 0 : rmap_walk_file(folio, rwc, false);
2512 0 : }
2513 :
2514 : /* Like rmap_walk, but caller holds relevant rmap lock */
2515 0 : void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
2516 : {
2517 : /* no ksm support for now */
2518 : VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
2519 0 : if (folio_test_anon(folio))
2520 0 : rmap_walk_anon(folio, rwc, true);
2521 : else
2522 0 : rmap_walk_file(folio, rwc, true);
2523 0 : }
2524 :
2525 : #ifdef CONFIG_HUGETLB_PAGE
2526 : /*
2527 : * The following two functions are for anonymous (private mapped) hugepages.
2528 : * Unlike common anonymous pages, anonymous hugepages have no accounting code
2529 : * and no lru code, because we handle hugepages differently from common pages.
2530 : *
2531 : * RMAP_COMPOUND is ignored.
2532 : */
2533 : void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
2534 : unsigned long address, rmap_t flags)
2535 : {
2536 : struct folio *folio = page_folio(page);
2537 : struct anon_vma *anon_vma = vma->anon_vma;
2538 : int first;
2539 :
2540 : BUG_ON(!folio_test_locked(folio));
2541 : BUG_ON(!anon_vma);
2542 : /* address might be in next vma when migration races vma_merge */
2543 : first = atomic_inc_and_test(&folio->_entire_mapcount);
2544 : VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
2545 : VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
2546 : if (first)
2547 : __page_set_anon_rmap(folio, page, vma, address,
2548 : !!(flags & RMAP_EXCLUSIVE));
2549 : }
2550 :
2551 : void hugepage_add_new_anon_rmap(struct folio *folio,
2552 : struct vm_area_struct *vma, unsigned long address)
2553 : {
2554 : BUG_ON(address < vma->vm_start || address >= vma->vm_end);
2555 : /* increment count (starts at -1) */
2556 : atomic_set(&folio->_entire_mapcount, 0);
2557 : folio_clear_hugetlb_restore_reserve(folio);
2558 : __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
2559 : }
2560 : #endif /* CONFIG_HUGETLB_PAGE */
|
