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