xref: /linux/mm/rmap.c (revision bab2c80e5a6c855657482eac9e97f5f3eedb509a)
1 /*
2  * mm/rmap.c - physical to virtual reverse mappings
3  *
4  * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5  * Released under the General Public License (GPL).
6  *
7  * Simple, low overhead reverse mapping scheme.
8  * Please try to keep this thing as modular as possible.
9  *
10  * Provides methods for unmapping each kind of mapped page:
11  * the anon methods track anonymous pages, and
12  * the file methods track pages belonging to an inode.
13  *
14  * Original design by Rik van Riel <riel@conectiva.com.br> 2001
15  * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
16  * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
17  * Contributions by Hugh Dickins 2003, 2004
18  */
19 
20 /*
21  * Lock ordering in mm:
22  *
23  * inode->i_mutex	(while writing or truncating, not reading or faulting)
24  *   mm->mmap_sem
25  *     page->flags PG_locked (lock_page)
26  *       hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
27  *         mapping->i_mmap_rwsem
28  *           anon_vma->rwsem
29  *             mm->page_table_lock or pte_lock
30  *               zone_lru_lock (in mark_page_accessed, isolate_lru_page)
31  *               swap_lock (in swap_duplicate, swap_info_get)
32  *                 mmlist_lock (in mmput, drain_mmlist and others)
33  *                 mapping->private_lock (in __set_page_dirty_buffers)
34  *                   mem_cgroup_{begin,end}_page_stat (memcg->move_lock)
35  *                     i_pages lock (widely used)
36  *                 inode->i_lock (in set_page_dirty's __mark_inode_dirty)
37  *                 bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
38  *                   sb_lock (within inode_lock in fs/fs-writeback.c)
39  *                   i_pages lock (widely used, in set_page_dirty,
40  *                             in arch-dependent flush_dcache_mmap_lock,
41  *                             within bdi.wb->list_lock in __sync_single_inode)
42  *
43  * anon_vma->rwsem,mapping->i_mutex      (memory_failure, collect_procs_anon)
44  *   ->tasklist_lock
45  *     pte map lock
46  */
47 
48 #include <linux/mm.h>
49 #include <linux/sched/mm.h>
50 #include <linux/sched/task.h>
51 #include <linux/pagemap.h>
52 #include <linux/swap.h>
53 #include <linux/swapops.h>
54 #include <linux/slab.h>
55 #include <linux/init.h>
56 #include <linux/ksm.h>
57 #include <linux/rmap.h>
58 #include <linux/rcupdate.h>
59 #include <linux/export.h>
60 #include <linux/memcontrol.h>
61 #include <linux/mmu_notifier.h>
62 #include <linux/migrate.h>
63 #include <linux/hugetlb.h>
64 #include <linux/backing-dev.h>
65 #include <linux/page_idle.h>
66 #include <linux/memremap.h>
67 
68 #include <asm/tlbflush.h>
69 
70 #include <trace/events/tlb.h>
71 
72 #include "internal.h"
73 
74 static struct kmem_cache *anon_vma_cachep;
75 static struct kmem_cache *anon_vma_chain_cachep;
76 
77 static inline struct anon_vma *anon_vma_alloc(void)
78 {
79 	struct anon_vma *anon_vma;
80 
81 	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
82 	if (anon_vma) {
83 		atomic_set(&anon_vma->refcount, 1);
84 		anon_vma->degree = 1;	/* Reference for first vma */
85 		anon_vma->parent = anon_vma;
86 		/*
87 		 * Initialise the anon_vma root to point to itself. If called
88 		 * from fork, the root will be reset to the parents anon_vma.
89 		 */
90 		anon_vma->root = anon_vma;
91 	}
92 
93 	return anon_vma;
94 }
95 
96 static inline void anon_vma_free(struct anon_vma *anon_vma)
97 {
98 	VM_BUG_ON(atomic_read(&anon_vma->refcount));
99 
100 	/*
101 	 * Synchronize against page_lock_anon_vma_read() such that
102 	 * we can safely hold the lock without the anon_vma getting
103 	 * freed.
104 	 *
105 	 * Relies on the full mb implied by the atomic_dec_and_test() from
106 	 * put_anon_vma() against the acquire barrier implied by
107 	 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
108 	 *
109 	 * page_lock_anon_vma_read()	VS	put_anon_vma()
110 	 *   down_read_trylock()		  atomic_dec_and_test()
111 	 *   LOCK				  MB
112 	 *   atomic_read()			  rwsem_is_locked()
113 	 *
114 	 * LOCK should suffice since the actual taking of the lock must
115 	 * happen _before_ what follows.
116 	 */
117 	might_sleep();
118 	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
119 		anon_vma_lock_write(anon_vma);
120 		anon_vma_unlock_write(anon_vma);
121 	}
122 
123 	kmem_cache_free(anon_vma_cachep, anon_vma);
124 }
125 
126 static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
127 {
128 	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
129 }
130 
131 static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
132 {
133 	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
134 }
135 
136 static void anon_vma_chain_link(struct vm_area_struct *vma,
137 				struct anon_vma_chain *avc,
138 				struct anon_vma *anon_vma)
139 {
140 	avc->vma = vma;
141 	avc->anon_vma = anon_vma;
142 	list_add(&avc->same_vma, &vma->anon_vma_chain);
143 	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
144 }
145 
146 /**
147  * __anon_vma_prepare - attach an anon_vma to a memory region
148  * @vma: the memory region in question
149  *
150  * This makes sure the memory mapping described by 'vma' has
151  * an 'anon_vma' attached to it, so that we can associate the
152  * anonymous pages mapped into it with that anon_vma.
153  *
154  * The common case will be that we already have one, which
155  * is handled inline by anon_vma_prepare(). But if
156  * not we either need to find an adjacent mapping that we
157  * can re-use the anon_vma from (very common when the only
158  * reason for splitting a vma has been mprotect()), or we
159  * allocate a new one.
160  *
161  * Anon-vma allocations are very subtle, because we may have
162  * optimistically looked up an anon_vma in page_lock_anon_vma_read()
163  * and that may actually touch the spinlock even in the newly
164  * allocated vma (it depends on RCU to make sure that the
165  * anon_vma isn't actually destroyed).
166  *
167  * As a result, we need to do proper anon_vma locking even
168  * for the new allocation. At the same time, we do not want
169  * to do any locking for the common case of already having
170  * an anon_vma.
171  *
172  * This must be called with the mmap_sem held for reading.
173  */
174 int __anon_vma_prepare(struct vm_area_struct *vma)
175 {
176 	struct mm_struct *mm = vma->vm_mm;
177 	struct anon_vma *anon_vma, *allocated;
178 	struct anon_vma_chain *avc;
179 
180 	might_sleep();
181 
182 	avc = anon_vma_chain_alloc(GFP_KERNEL);
183 	if (!avc)
184 		goto out_enomem;
185 
186 	anon_vma = find_mergeable_anon_vma(vma);
187 	allocated = NULL;
188 	if (!anon_vma) {
189 		anon_vma = anon_vma_alloc();
190 		if (unlikely(!anon_vma))
191 			goto out_enomem_free_avc;
192 		allocated = anon_vma;
193 	}
194 
195 	anon_vma_lock_write(anon_vma);
196 	/* page_table_lock to protect against threads */
197 	spin_lock(&mm->page_table_lock);
198 	if (likely(!vma->anon_vma)) {
199 		vma->anon_vma = anon_vma;
200 		anon_vma_chain_link(vma, avc, anon_vma);
201 		/* vma reference or self-parent link for new root */
202 		anon_vma->degree++;
203 		allocated = NULL;
204 		avc = NULL;
205 	}
206 	spin_unlock(&mm->page_table_lock);
207 	anon_vma_unlock_write(anon_vma);
208 
209 	if (unlikely(allocated))
210 		put_anon_vma(allocated);
211 	if (unlikely(avc))
212 		anon_vma_chain_free(avc);
213 
214 	return 0;
215 
216  out_enomem_free_avc:
217 	anon_vma_chain_free(avc);
218  out_enomem:
219 	return -ENOMEM;
220 }
221 
222 /*
223  * This is a useful helper function for locking the anon_vma root as
224  * we traverse the vma->anon_vma_chain, looping over anon_vma's that
225  * have the same vma.
226  *
227  * Such anon_vma's should have the same root, so you'd expect to see
228  * just a single mutex_lock for the whole traversal.
229  */
230 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
231 {
232 	struct anon_vma *new_root = anon_vma->root;
233 	if (new_root != root) {
234 		if (WARN_ON_ONCE(root))
235 			up_write(&root->rwsem);
236 		root = new_root;
237 		down_write(&root->rwsem);
238 	}
239 	return root;
240 }
241 
242 static inline void unlock_anon_vma_root(struct anon_vma *root)
243 {
244 	if (root)
245 		up_write(&root->rwsem);
246 }
247 
248 /*
249  * Attach the anon_vmas from src to dst.
250  * Returns 0 on success, -ENOMEM on failure.
251  *
252  * If dst->anon_vma is NULL this function tries to find and reuse existing
253  * anon_vma which has no vmas and only one child anon_vma. This prevents
254  * degradation of anon_vma hierarchy to endless linear chain in case of
255  * constantly forking task. On the other hand, an anon_vma with more than one
256  * child isn't reused even if there was no alive vma, thus rmap walker has a
257  * good chance of avoiding scanning the whole hierarchy when it searches where
258  * page is mapped.
259  */
260 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
261 {
262 	struct anon_vma_chain *avc, *pavc;
263 	struct anon_vma *root = NULL;
264 
265 	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
266 		struct anon_vma *anon_vma;
267 
268 		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
269 		if (unlikely(!avc)) {
270 			unlock_anon_vma_root(root);
271 			root = NULL;
272 			avc = anon_vma_chain_alloc(GFP_KERNEL);
273 			if (!avc)
274 				goto enomem_failure;
275 		}
276 		anon_vma = pavc->anon_vma;
277 		root = lock_anon_vma_root(root, anon_vma);
278 		anon_vma_chain_link(dst, avc, anon_vma);
279 
280 		/*
281 		 * Reuse existing anon_vma if its degree lower than two,
282 		 * that means it has no vma and only one anon_vma child.
283 		 *
284 		 * Do not chose parent anon_vma, otherwise first child
285 		 * will always reuse it. Root anon_vma is never reused:
286 		 * it has self-parent reference and at least one child.
287 		 */
288 		if (!dst->anon_vma && anon_vma != src->anon_vma &&
289 				anon_vma->degree < 2)
290 			dst->anon_vma = anon_vma;
291 	}
292 	if (dst->anon_vma)
293 		dst->anon_vma->degree++;
294 	unlock_anon_vma_root(root);
295 	return 0;
296 
297  enomem_failure:
298 	/*
299 	 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
300 	 * decremented in unlink_anon_vmas().
301 	 * We can safely do this because callers of anon_vma_clone() don't care
302 	 * about dst->anon_vma if anon_vma_clone() failed.
303 	 */
304 	dst->anon_vma = NULL;
305 	unlink_anon_vmas(dst);
306 	return -ENOMEM;
307 }
308 
309 /*
310  * Attach vma to its own anon_vma, as well as to the anon_vmas that
311  * the corresponding VMA in the parent process is attached to.
312  * Returns 0 on success, non-zero on failure.
313  */
314 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
315 {
316 	struct anon_vma_chain *avc;
317 	struct anon_vma *anon_vma;
318 	int error;
319 
320 	/* Don't bother if the parent process has no anon_vma here. */
321 	if (!pvma->anon_vma)
322 		return 0;
323 
324 	/* Drop inherited anon_vma, we'll reuse existing or allocate new. */
325 	vma->anon_vma = NULL;
326 
327 	/*
328 	 * First, attach the new VMA to the parent VMA's anon_vmas,
329 	 * so rmap can find non-COWed pages in child processes.
330 	 */
331 	error = anon_vma_clone(vma, pvma);
332 	if (error)
333 		return error;
334 
335 	/* An existing anon_vma has been reused, all done then. */
336 	if (vma->anon_vma)
337 		return 0;
338 
339 	/* Then add our own anon_vma. */
340 	anon_vma = anon_vma_alloc();
341 	if (!anon_vma)
342 		goto out_error;
343 	avc = anon_vma_chain_alloc(GFP_KERNEL);
344 	if (!avc)
345 		goto out_error_free_anon_vma;
346 
347 	/*
348 	 * The root anon_vma's spinlock is the lock actually used when we
349 	 * lock any of the anon_vmas in this anon_vma tree.
350 	 */
351 	anon_vma->root = pvma->anon_vma->root;
352 	anon_vma->parent = pvma->anon_vma;
353 	/*
354 	 * With refcounts, an anon_vma can stay around longer than the
355 	 * process it belongs to. The root anon_vma needs to be pinned until
356 	 * this anon_vma is freed, because the lock lives in the root.
357 	 */
358 	get_anon_vma(anon_vma->root);
359 	/* Mark this anon_vma as the one where our new (COWed) pages go. */
360 	vma->anon_vma = anon_vma;
361 	anon_vma_lock_write(anon_vma);
362 	anon_vma_chain_link(vma, avc, anon_vma);
363 	anon_vma->parent->degree++;
364 	anon_vma_unlock_write(anon_vma);
365 
366 	return 0;
367 
368  out_error_free_anon_vma:
369 	put_anon_vma(anon_vma);
370  out_error:
371 	unlink_anon_vmas(vma);
372 	return -ENOMEM;
373 }
374 
375 void unlink_anon_vmas(struct vm_area_struct *vma)
376 {
377 	struct anon_vma_chain *avc, *next;
378 	struct anon_vma *root = NULL;
379 
380 	/*
381 	 * Unlink each anon_vma chained to the VMA.  This list is ordered
382 	 * from newest to oldest, ensuring the root anon_vma gets freed last.
383 	 */
384 	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
385 		struct anon_vma *anon_vma = avc->anon_vma;
386 
387 		root = lock_anon_vma_root(root, anon_vma);
388 		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
389 
390 		/*
391 		 * Leave empty anon_vmas on the list - we'll need
392 		 * to free them outside the lock.
393 		 */
394 		if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
395 			anon_vma->parent->degree--;
396 			continue;
397 		}
398 
399 		list_del(&avc->same_vma);
400 		anon_vma_chain_free(avc);
401 	}
402 	if (vma->anon_vma)
403 		vma->anon_vma->degree--;
404 	unlock_anon_vma_root(root);
405 
406 	/*
407 	 * Iterate the list once more, it now only contains empty and unlinked
408 	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
409 	 * needing to write-acquire the anon_vma->root->rwsem.
410 	 */
411 	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
412 		struct anon_vma *anon_vma = avc->anon_vma;
413 
414 		VM_WARN_ON(anon_vma->degree);
415 		put_anon_vma(anon_vma);
416 
417 		list_del(&avc->same_vma);
418 		anon_vma_chain_free(avc);
419 	}
420 }
421 
422 static void anon_vma_ctor(void *data)
423 {
424 	struct anon_vma *anon_vma = data;
425 
426 	init_rwsem(&anon_vma->rwsem);
427 	atomic_set(&anon_vma->refcount, 0);
428 	anon_vma->rb_root = RB_ROOT_CACHED;
429 }
430 
431 void __init anon_vma_init(void)
432 {
433 	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
434 			0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
435 			anon_vma_ctor);
436 	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
437 			SLAB_PANIC|SLAB_ACCOUNT);
438 }
439 
440 /*
441  * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
442  *
443  * Since there is no serialization what so ever against page_remove_rmap()
444  * the best this function can do is return a locked anon_vma that might
445  * have been relevant to this page.
446  *
447  * The page might have been remapped to a different anon_vma or the anon_vma
448  * returned may already be freed (and even reused).
449  *
450  * In case it was remapped to a different anon_vma, the new anon_vma will be a
451  * child of the old anon_vma, and the anon_vma lifetime rules will therefore
452  * ensure that any anon_vma obtained from the page will still be valid for as
453  * long as we observe page_mapped() [ hence all those page_mapped() tests ].
454  *
455  * All users of this function must be very careful when walking the anon_vma
456  * chain and verify that the page in question is indeed mapped in it
457  * [ something equivalent to page_mapped_in_vma() ].
458  *
459  * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
460  * that the anon_vma pointer from page->mapping is valid if there is a
461  * mapcount, we can dereference the anon_vma after observing those.
462  */
463 struct anon_vma *page_get_anon_vma(struct page *page)
464 {
465 	struct anon_vma *anon_vma = NULL;
466 	unsigned long anon_mapping;
467 
468 	rcu_read_lock();
469 	anon_mapping = (unsigned long)READ_ONCE(page->mapping);
470 	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
471 		goto out;
472 	if (!page_mapped(page))
473 		goto out;
474 
475 	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
476 	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
477 		anon_vma = NULL;
478 		goto out;
479 	}
480 
481 	/*
482 	 * If this page is still mapped, then its anon_vma cannot have been
483 	 * freed.  But if it has been unmapped, we have no security against the
484 	 * anon_vma structure being freed and reused (for another anon_vma:
485 	 * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
486 	 * above cannot corrupt).
487 	 */
488 	if (!page_mapped(page)) {
489 		rcu_read_unlock();
490 		put_anon_vma(anon_vma);
491 		return NULL;
492 	}
493 out:
494 	rcu_read_unlock();
495 
496 	return anon_vma;
497 }
498 
499 /*
500  * Similar to page_get_anon_vma() except it locks the anon_vma.
501  *
502  * Its a little more complex as it tries to keep the fast path to a single
503  * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
504  * reference like with page_get_anon_vma() and then block on the mutex.
505  */
506 struct anon_vma *page_lock_anon_vma_read(struct page *page)
507 {
508 	struct anon_vma *anon_vma = NULL;
509 	struct anon_vma *root_anon_vma;
510 	unsigned long anon_mapping;
511 
512 	rcu_read_lock();
513 	anon_mapping = (unsigned long)READ_ONCE(page->mapping);
514 	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
515 		goto out;
516 	if (!page_mapped(page))
517 		goto out;
518 
519 	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
520 	root_anon_vma = READ_ONCE(anon_vma->root);
521 	if (down_read_trylock(&root_anon_vma->rwsem)) {
522 		/*
523 		 * If the page is still mapped, then this anon_vma is still
524 		 * its anon_vma, and holding the mutex ensures that it will
525 		 * not go away, see anon_vma_free().
526 		 */
527 		if (!page_mapped(page)) {
528 			up_read(&root_anon_vma->rwsem);
529 			anon_vma = NULL;
530 		}
531 		goto out;
532 	}
533 
534 	/* trylock failed, we got to sleep */
535 	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
536 		anon_vma = NULL;
537 		goto out;
538 	}
539 
540 	if (!page_mapped(page)) {
541 		rcu_read_unlock();
542 		put_anon_vma(anon_vma);
543 		return NULL;
544 	}
545 
546 	/* we pinned the anon_vma, its safe to sleep */
547 	rcu_read_unlock();
548 	anon_vma_lock_read(anon_vma);
549 
550 	if (atomic_dec_and_test(&anon_vma->refcount)) {
551 		/*
552 		 * Oops, we held the last refcount, release the lock
553 		 * and bail -- can't simply use put_anon_vma() because
554 		 * we'll deadlock on the anon_vma_lock_write() recursion.
555 		 */
556 		anon_vma_unlock_read(anon_vma);
557 		__put_anon_vma(anon_vma);
558 		anon_vma = NULL;
559 	}
560 
561 	return anon_vma;
562 
563 out:
564 	rcu_read_unlock();
565 	return anon_vma;
566 }
567 
568 void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
569 {
570 	anon_vma_unlock_read(anon_vma);
571 }
572 
573 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
574 /*
575  * Flush TLB entries for recently unmapped pages from remote CPUs. It is
576  * important if a PTE was dirty when it was unmapped that it's flushed
577  * before any IO is initiated on the page to prevent lost writes. Similarly,
578  * it must be flushed before freeing to prevent data leakage.
579  */
580 void try_to_unmap_flush(void)
581 {
582 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
583 
584 	if (!tlb_ubc->flush_required)
585 		return;
586 
587 	arch_tlbbatch_flush(&tlb_ubc->arch);
588 	tlb_ubc->flush_required = false;
589 	tlb_ubc->writable = false;
590 }
591 
592 /* Flush iff there are potentially writable TLB entries that can race with IO */
593 void try_to_unmap_flush_dirty(void)
594 {
595 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
596 
597 	if (tlb_ubc->writable)
598 		try_to_unmap_flush();
599 }
600 
601 static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
602 {
603 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
604 
605 	arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
606 	tlb_ubc->flush_required = true;
607 
608 	/*
609 	 * Ensure compiler does not re-order the setting of tlb_flush_batched
610 	 * before the PTE is cleared.
611 	 */
612 	barrier();
613 	mm->tlb_flush_batched = true;
614 
615 	/*
616 	 * If the PTE was dirty then it's best to assume it's writable. The
617 	 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
618 	 * before the page is queued for IO.
619 	 */
620 	if (writable)
621 		tlb_ubc->writable = true;
622 }
623 
624 /*
625  * Returns true if the TLB flush should be deferred to the end of a batch of
626  * unmap operations to reduce IPIs.
627  */
628 static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
629 {
630 	bool should_defer = false;
631 
632 	if (!(flags & TTU_BATCH_FLUSH))
633 		return false;
634 
635 	/* If remote CPUs need to be flushed then defer batch the flush */
636 	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
637 		should_defer = true;
638 	put_cpu();
639 
640 	return should_defer;
641 }
642 
643 /*
644  * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
645  * releasing the PTL if TLB flushes are batched. It's possible for a parallel
646  * operation such as mprotect or munmap to race between reclaim unmapping
647  * the page and flushing the page. If this race occurs, it potentially allows
648  * access to data via a stale TLB entry. Tracking all mm's that have TLB
649  * batching in flight would be expensive during reclaim so instead track
650  * whether TLB batching occurred in the past and if so then do a flush here
651  * if required. This will cost one additional flush per reclaim cycle paid
652  * by the first operation at risk such as mprotect and mumap.
653  *
654  * This must be called under the PTL so that an access to tlb_flush_batched
655  * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
656  * via the PTL.
657  */
658 void flush_tlb_batched_pending(struct mm_struct *mm)
659 {
660 	if (mm->tlb_flush_batched) {
661 		flush_tlb_mm(mm);
662 
663 		/*
664 		 * Do not allow the compiler to re-order the clearing of
665 		 * tlb_flush_batched before the tlb is flushed.
666 		 */
667 		barrier();
668 		mm->tlb_flush_batched = false;
669 	}
670 }
671 #else
672 static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
673 {
674 }
675 
676 static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
677 {
678 	return false;
679 }
680 #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
681 
682 /*
683  * At what user virtual address is page expected in vma?
684  * Caller should check the page is actually part of the vma.
685  */
686 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
687 {
688 	unsigned long address;
689 	if (PageAnon(page)) {
690 		struct anon_vma *page__anon_vma = page_anon_vma(page);
691 		/*
692 		 * Note: swapoff's unuse_vma() is more efficient with this
693 		 * check, and needs it to match anon_vma when KSM is active.
694 		 */
695 		if (!vma->anon_vma || !page__anon_vma ||
696 		    vma->anon_vma->root != page__anon_vma->root)
697 			return -EFAULT;
698 	} else if (page->mapping) {
699 		if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
700 			return -EFAULT;
701 	} else
702 		return -EFAULT;
703 	address = __vma_address(page, vma);
704 	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
705 		return -EFAULT;
706 	return address;
707 }
708 
709 pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
710 {
711 	pgd_t *pgd;
712 	p4d_t *p4d;
713 	pud_t *pud;
714 	pmd_t *pmd = NULL;
715 	pmd_t pmde;
716 
717 	pgd = pgd_offset(mm, address);
718 	if (!pgd_present(*pgd))
719 		goto out;
720 
721 	p4d = p4d_offset(pgd, address);
722 	if (!p4d_present(*p4d))
723 		goto out;
724 
725 	pud = pud_offset(p4d, address);
726 	if (!pud_present(*pud))
727 		goto out;
728 
729 	pmd = pmd_offset(pud, address);
730 	/*
731 	 * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
732 	 * without holding anon_vma lock for write.  So when looking for a
733 	 * genuine pmde (in which to find pte), test present and !THP together.
734 	 */
735 	pmde = *pmd;
736 	barrier();
737 	if (!pmd_present(pmde) || pmd_trans_huge(pmde))
738 		pmd = NULL;
739 out:
740 	return pmd;
741 }
742 
743 struct page_referenced_arg {
744 	int mapcount;
745 	int referenced;
746 	unsigned long vm_flags;
747 	struct mem_cgroup *memcg;
748 };
749 /*
750  * arg: page_referenced_arg will be passed
751  */
752 static bool page_referenced_one(struct page *page, struct vm_area_struct *vma,
753 			unsigned long address, void *arg)
754 {
755 	struct page_referenced_arg *pra = arg;
756 	struct page_vma_mapped_walk pvmw = {
757 		.page = page,
758 		.vma = vma,
759 		.address = address,
760 	};
761 	int referenced = 0;
762 
763 	while (page_vma_mapped_walk(&pvmw)) {
764 		address = pvmw.address;
765 
766 		if (vma->vm_flags & VM_LOCKED) {
767 			page_vma_mapped_walk_done(&pvmw);
768 			pra->vm_flags |= VM_LOCKED;
769 			return false; /* To break the loop */
770 		}
771 
772 		if (pvmw.pte) {
773 			if (ptep_clear_flush_young_notify(vma, address,
774 						pvmw.pte)) {
775 				/*
776 				 * Don't treat a reference through
777 				 * a sequentially read mapping as such.
778 				 * If the page has been used in another mapping,
779 				 * we will catch it; if this other mapping is
780 				 * already gone, the unmap path will have set
781 				 * PG_referenced or activated the page.
782 				 */
783 				if (likely(!(vma->vm_flags & VM_SEQ_READ)))
784 					referenced++;
785 			}
786 		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
787 			if (pmdp_clear_flush_young_notify(vma, address,
788 						pvmw.pmd))
789 				referenced++;
790 		} else {
791 			/* unexpected pmd-mapped page? */
792 			WARN_ON_ONCE(1);
793 		}
794 
795 		pra->mapcount--;
796 	}
797 
798 	if (referenced)
799 		clear_page_idle(page);
800 	if (test_and_clear_page_young(page))
801 		referenced++;
802 
803 	if (referenced) {
804 		pra->referenced++;
805 		pra->vm_flags |= vma->vm_flags;
806 	}
807 
808 	if (!pra->mapcount)
809 		return false; /* To break the loop */
810 
811 	return true;
812 }
813 
814 static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
815 {
816 	struct page_referenced_arg *pra = arg;
817 	struct mem_cgroup *memcg = pra->memcg;
818 
819 	if (!mm_match_cgroup(vma->vm_mm, memcg))
820 		return true;
821 
822 	return false;
823 }
824 
825 /**
826  * page_referenced - test if the page was referenced
827  * @page: the page to test
828  * @is_locked: caller holds lock on the page
829  * @memcg: target memory cgroup
830  * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
831  *
832  * Quick test_and_clear_referenced for all mappings to a page,
833  * returns the number of ptes which referenced the page.
834  */
835 int page_referenced(struct page *page,
836 		    int is_locked,
837 		    struct mem_cgroup *memcg,
838 		    unsigned long *vm_flags)
839 {
840 	int we_locked = 0;
841 	struct page_referenced_arg pra = {
842 		.mapcount = total_mapcount(page),
843 		.memcg = memcg,
844 	};
845 	struct rmap_walk_control rwc = {
846 		.rmap_one = page_referenced_one,
847 		.arg = (void *)&pra,
848 		.anon_lock = page_lock_anon_vma_read,
849 	};
850 
851 	*vm_flags = 0;
852 	if (!page_mapped(page))
853 		return 0;
854 
855 	if (!page_rmapping(page))
856 		return 0;
857 
858 	if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
859 		we_locked = trylock_page(page);
860 		if (!we_locked)
861 			return 1;
862 	}
863 
864 	/*
865 	 * If we are reclaiming on behalf of a cgroup, skip
866 	 * counting on behalf of references from different
867 	 * cgroups
868 	 */
869 	if (memcg) {
870 		rwc.invalid_vma = invalid_page_referenced_vma;
871 	}
872 
873 	rmap_walk(page, &rwc);
874 	*vm_flags = pra.vm_flags;
875 
876 	if (we_locked)
877 		unlock_page(page);
878 
879 	return pra.referenced;
880 }
881 
882 static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
883 			    unsigned long address, void *arg)
884 {
885 	struct page_vma_mapped_walk pvmw = {
886 		.page = page,
887 		.vma = vma,
888 		.address = address,
889 		.flags = PVMW_SYNC,
890 	};
891 	unsigned long start = address, end;
892 	int *cleaned = arg;
893 
894 	/*
895 	 * We have to assume the worse case ie pmd for invalidation. Note that
896 	 * the page can not be free from this function.
897 	 */
898 	end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
899 	mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
900 
901 	while (page_vma_mapped_walk(&pvmw)) {
902 		unsigned long cstart;
903 		int ret = 0;
904 
905 		cstart = address = pvmw.address;
906 		if (pvmw.pte) {
907 			pte_t entry;
908 			pte_t *pte = pvmw.pte;
909 
910 			if (!pte_dirty(*pte) && !pte_write(*pte))
911 				continue;
912 
913 			flush_cache_page(vma, address, pte_pfn(*pte));
914 			entry = ptep_clear_flush(vma, address, pte);
915 			entry = pte_wrprotect(entry);
916 			entry = pte_mkclean(entry);
917 			set_pte_at(vma->vm_mm, address, pte, entry);
918 			ret = 1;
919 		} else {
920 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
921 			pmd_t *pmd = pvmw.pmd;
922 			pmd_t entry;
923 
924 			if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
925 				continue;
926 
927 			flush_cache_page(vma, address, page_to_pfn(page));
928 			entry = pmdp_huge_clear_flush(vma, address, pmd);
929 			entry = pmd_wrprotect(entry);
930 			entry = pmd_mkclean(entry);
931 			set_pmd_at(vma->vm_mm, address, pmd, entry);
932 			cstart &= PMD_MASK;
933 			ret = 1;
934 #else
935 			/* unexpected pmd-mapped page? */
936 			WARN_ON_ONCE(1);
937 #endif
938 		}
939 
940 		/*
941 		 * No need to call mmu_notifier_invalidate_range() as we are
942 		 * downgrading page table protection not changing it to point
943 		 * to a new page.
944 		 *
945 		 * See Documentation/vm/mmu_notifier.rst
946 		 */
947 		if (ret)
948 			(*cleaned)++;
949 	}
950 
951 	mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
952 
953 	return true;
954 }
955 
956 static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
957 {
958 	if (vma->vm_flags & VM_SHARED)
959 		return false;
960 
961 	return true;
962 }
963 
964 int page_mkclean(struct page *page)
965 {
966 	int cleaned = 0;
967 	struct address_space *mapping;
968 	struct rmap_walk_control rwc = {
969 		.arg = (void *)&cleaned,
970 		.rmap_one = page_mkclean_one,
971 		.invalid_vma = invalid_mkclean_vma,
972 	};
973 
974 	BUG_ON(!PageLocked(page));
975 
976 	if (!page_mapped(page))
977 		return 0;
978 
979 	mapping = page_mapping(page);
980 	if (!mapping)
981 		return 0;
982 
983 	rmap_walk(page, &rwc);
984 
985 	return cleaned;
986 }
987 EXPORT_SYMBOL_GPL(page_mkclean);
988 
989 /**
990  * page_move_anon_rmap - move a page to our anon_vma
991  * @page:	the page to move to our anon_vma
992  * @vma:	the vma the page belongs to
993  *
994  * When a page belongs exclusively to one process after a COW event,
995  * that page can be moved into the anon_vma that belongs to just that
996  * process, so the rmap code will not search the parent or sibling
997  * processes.
998  */
999 void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
1000 {
1001 	struct anon_vma *anon_vma = vma->anon_vma;
1002 
1003 	page = compound_head(page);
1004 
1005 	VM_BUG_ON_PAGE(!PageLocked(page), page);
1006 	VM_BUG_ON_VMA(!anon_vma, vma);
1007 
1008 	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1009 	/*
1010 	 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1011 	 * simultaneously, so a concurrent reader (eg page_referenced()'s
1012 	 * PageAnon()) will not see one without the other.
1013 	 */
1014 	WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
1015 }
1016 
1017 /**
1018  * __page_set_anon_rmap - set up new anonymous rmap
1019  * @page:	Page to add to rmap
1020  * @vma:	VM area to add page to.
1021  * @address:	User virtual address of the mapping
1022  * @exclusive:	the page is exclusively owned by the current process
1023  */
1024 static void __page_set_anon_rmap(struct page *page,
1025 	struct vm_area_struct *vma, unsigned long address, int exclusive)
1026 {
1027 	struct anon_vma *anon_vma = vma->anon_vma;
1028 
1029 	BUG_ON(!anon_vma);
1030 
1031 	if (PageAnon(page))
1032 		return;
1033 
1034 	/*
1035 	 * If the page isn't exclusively mapped into this vma,
1036 	 * we must use the _oldest_ possible anon_vma for the
1037 	 * page mapping!
1038 	 */
1039 	if (!exclusive)
1040 		anon_vma = anon_vma->root;
1041 
1042 	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1043 	page->mapping = (struct address_space *) anon_vma;
1044 	page->index = linear_page_index(vma, address);
1045 }
1046 
1047 /**
1048  * __page_check_anon_rmap - sanity check anonymous rmap addition
1049  * @page:	the page to add the mapping to
1050  * @vma:	the vm area in which the mapping is added
1051  * @address:	the user virtual address mapped
1052  */
1053 static void __page_check_anon_rmap(struct page *page,
1054 	struct vm_area_struct *vma, unsigned long address)
1055 {
1056 #ifdef CONFIG_DEBUG_VM
1057 	/*
1058 	 * The page's anon-rmap details (mapping and index) are guaranteed to
1059 	 * be set up correctly at this point.
1060 	 *
1061 	 * We have exclusion against page_add_anon_rmap because the caller
1062 	 * always holds the page locked, except if called from page_dup_rmap,
1063 	 * in which case the page is already known to be setup.
1064 	 *
1065 	 * We have exclusion against page_add_new_anon_rmap because those pages
1066 	 * are initially only visible via the pagetables, and the pte is locked
1067 	 * over the call to page_add_new_anon_rmap.
1068 	 */
1069 	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1070 	BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
1071 #endif
1072 }
1073 
1074 /**
1075  * page_add_anon_rmap - add pte mapping to an anonymous page
1076  * @page:	the page to add the mapping to
1077  * @vma:	the vm area in which the mapping is added
1078  * @address:	the user virtual address mapped
1079  * @compound:	charge the page as compound or small page
1080  *
1081  * The caller needs to hold the pte lock, and the page must be locked in
1082  * the anon_vma case: to serialize mapping,index checking after setting,
1083  * and to ensure that PageAnon is not being upgraded racily to PageKsm
1084  * (but PageKsm is never downgraded to PageAnon).
1085  */
1086 void page_add_anon_rmap(struct page *page,
1087 	struct vm_area_struct *vma, unsigned long address, bool compound)
1088 {
1089 	do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0);
1090 }
1091 
1092 /*
1093  * Special version of the above for do_swap_page, which often runs
1094  * into pages that are exclusively owned by the current process.
1095  * Everybody else should continue to use page_add_anon_rmap above.
1096  */
1097 void do_page_add_anon_rmap(struct page *page,
1098 	struct vm_area_struct *vma, unsigned long address, int flags)
1099 {
1100 	bool compound = flags & RMAP_COMPOUND;
1101 	bool first;
1102 
1103 	if (compound) {
1104 		atomic_t *mapcount;
1105 		VM_BUG_ON_PAGE(!PageLocked(page), page);
1106 		VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1107 		mapcount = compound_mapcount_ptr(page);
1108 		first = atomic_inc_and_test(mapcount);
1109 	} else {
1110 		first = atomic_inc_and_test(&page->_mapcount);
1111 	}
1112 
1113 	if (first) {
1114 		int nr = compound ? hpage_nr_pages(page) : 1;
1115 		/*
1116 		 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1117 		 * these counters are not modified in interrupt context, and
1118 		 * pte lock(a spinlock) is held, which implies preemption
1119 		 * disabled.
1120 		 */
1121 		if (compound)
1122 			__inc_node_page_state(page, NR_ANON_THPS);
1123 		__mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1124 	}
1125 	if (unlikely(PageKsm(page)))
1126 		return;
1127 
1128 	VM_BUG_ON_PAGE(!PageLocked(page), page);
1129 
1130 	/* address might be in next vma when migration races vma_adjust */
1131 	if (first)
1132 		__page_set_anon_rmap(page, vma, address,
1133 				flags & RMAP_EXCLUSIVE);
1134 	else
1135 		__page_check_anon_rmap(page, vma, address);
1136 }
1137 
1138 /**
1139  * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1140  * @page:	the page to add the mapping to
1141  * @vma:	the vm area in which the mapping is added
1142  * @address:	the user virtual address mapped
1143  * @compound:	charge the page as compound or small page
1144  *
1145  * Same as page_add_anon_rmap but must only be called on *new* pages.
1146  * This means the inc-and-test can be bypassed.
1147  * Page does not have to be locked.
1148  */
1149 void page_add_new_anon_rmap(struct page *page,
1150 	struct vm_area_struct *vma, unsigned long address, bool compound)
1151 {
1152 	int nr = compound ? hpage_nr_pages(page) : 1;
1153 
1154 	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1155 	__SetPageSwapBacked(page);
1156 	if (compound) {
1157 		VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1158 		/* increment count (starts at -1) */
1159 		atomic_set(compound_mapcount_ptr(page), 0);
1160 		__inc_node_page_state(page, NR_ANON_THPS);
1161 	} else {
1162 		/* Anon THP always mapped first with PMD */
1163 		VM_BUG_ON_PAGE(PageTransCompound(page), page);
1164 		/* increment count (starts at -1) */
1165 		atomic_set(&page->_mapcount, 0);
1166 	}
1167 	__mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1168 	__page_set_anon_rmap(page, vma, address, 1);
1169 }
1170 
1171 /**
1172  * page_add_file_rmap - add pte mapping to a file page
1173  * @page: the page to add the mapping to
1174  * @compound: charge the page as compound or small page
1175  *
1176  * The caller needs to hold the pte lock.
1177  */
1178 void page_add_file_rmap(struct page *page, bool compound)
1179 {
1180 	int i, nr = 1;
1181 
1182 	VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
1183 	lock_page_memcg(page);
1184 	if (compound && PageTransHuge(page)) {
1185 		for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1186 			if (atomic_inc_and_test(&page[i]._mapcount))
1187 				nr++;
1188 		}
1189 		if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
1190 			goto out;
1191 		VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1192 		__inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
1193 	} else {
1194 		if (PageTransCompound(page) && page_mapping(page)) {
1195 			VM_WARN_ON_ONCE(!PageLocked(page));
1196 
1197 			SetPageDoubleMap(compound_head(page));
1198 			if (PageMlocked(page))
1199 				clear_page_mlock(compound_head(page));
1200 		}
1201 		if (!atomic_inc_and_test(&page->_mapcount))
1202 			goto out;
1203 	}
1204 	__mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
1205 out:
1206 	unlock_page_memcg(page);
1207 }
1208 
1209 static void page_remove_file_rmap(struct page *page, bool compound)
1210 {
1211 	int i, nr = 1;
1212 
1213 	VM_BUG_ON_PAGE(compound && !PageHead(page), page);
1214 	lock_page_memcg(page);
1215 
1216 	/* Hugepages are not counted in NR_FILE_MAPPED for now. */
1217 	if (unlikely(PageHuge(page))) {
1218 		/* hugetlb pages are always mapped with pmds */
1219 		atomic_dec(compound_mapcount_ptr(page));
1220 		goto out;
1221 	}
1222 
1223 	/* page still mapped by someone else? */
1224 	if (compound && PageTransHuge(page)) {
1225 		for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1226 			if (atomic_add_negative(-1, &page[i]._mapcount))
1227 				nr++;
1228 		}
1229 		if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1230 			goto out;
1231 		VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1232 		__dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
1233 	} else {
1234 		if (!atomic_add_negative(-1, &page->_mapcount))
1235 			goto out;
1236 	}
1237 
1238 	/*
1239 	 * We use the irq-unsafe __{inc|mod}_lruvec_page_state because
1240 	 * these counters are not modified in interrupt context, and
1241 	 * pte lock(a spinlock) is held, which implies preemption disabled.
1242 	 */
1243 	__mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr);
1244 
1245 	if (unlikely(PageMlocked(page)))
1246 		clear_page_mlock(page);
1247 out:
1248 	unlock_page_memcg(page);
1249 }
1250 
1251 static void page_remove_anon_compound_rmap(struct page *page)
1252 {
1253 	int i, nr;
1254 
1255 	if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1256 		return;
1257 
1258 	/* Hugepages are not counted in NR_ANON_PAGES for now. */
1259 	if (unlikely(PageHuge(page)))
1260 		return;
1261 
1262 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1263 		return;
1264 
1265 	__dec_node_page_state(page, NR_ANON_THPS);
1266 
1267 	if (TestClearPageDoubleMap(page)) {
1268 		/*
1269 		 * Subpages can be mapped with PTEs too. Check how many of
1270 		 * themi are still mapped.
1271 		 */
1272 		for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1273 			if (atomic_add_negative(-1, &page[i]._mapcount))
1274 				nr++;
1275 		}
1276 	} else {
1277 		nr = HPAGE_PMD_NR;
1278 	}
1279 
1280 	if (unlikely(PageMlocked(page)))
1281 		clear_page_mlock(page);
1282 
1283 	if (nr) {
1284 		__mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
1285 		deferred_split_huge_page(page);
1286 	}
1287 }
1288 
1289 /**
1290  * page_remove_rmap - take down pte mapping from a page
1291  * @page:	page to remove mapping from
1292  * @compound:	uncharge the page as compound or small page
1293  *
1294  * The caller needs to hold the pte lock.
1295  */
1296 void page_remove_rmap(struct page *page, bool compound)
1297 {
1298 	if (!PageAnon(page))
1299 		return page_remove_file_rmap(page, compound);
1300 
1301 	if (compound)
1302 		return page_remove_anon_compound_rmap(page);
1303 
1304 	/* page still mapped by someone else? */
1305 	if (!atomic_add_negative(-1, &page->_mapcount))
1306 		return;
1307 
1308 	/*
1309 	 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1310 	 * these counters are not modified in interrupt context, and
1311 	 * pte lock(a spinlock) is held, which implies preemption disabled.
1312 	 */
1313 	__dec_node_page_state(page, NR_ANON_MAPPED);
1314 
1315 	if (unlikely(PageMlocked(page)))
1316 		clear_page_mlock(page);
1317 
1318 	if (PageTransCompound(page))
1319 		deferred_split_huge_page(compound_head(page));
1320 
1321 	/*
1322 	 * It would be tidy to reset the PageAnon mapping here,
1323 	 * but that might overwrite a racing page_add_anon_rmap
1324 	 * which increments mapcount after us but sets mapping
1325 	 * before us: so leave the reset to free_unref_page,
1326 	 * and remember that it's only reliable while mapped.
1327 	 * Leaving it set also helps swapoff to reinstate ptes
1328 	 * faster for those pages still in swapcache.
1329 	 */
1330 }
1331 
1332 /*
1333  * @arg: enum ttu_flags will be passed to this argument
1334  */
1335 static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1336 		     unsigned long address, void *arg)
1337 {
1338 	struct mm_struct *mm = vma->vm_mm;
1339 	struct page_vma_mapped_walk pvmw = {
1340 		.page = page,
1341 		.vma = vma,
1342 		.address = address,
1343 	};
1344 	pte_t pteval;
1345 	struct page *subpage;
1346 	bool ret = true;
1347 	unsigned long start = address, end;
1348 	enum ttu_flags flags = (enum ttu_flags)arg;
1349 
1350 	/* munlock has nothing to gain from examining un-locked vmas */
1351 	if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
1352 		return true;
1353 
1354 	if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1355 	    is_zone_device_page(page) && !is_device_private_page(page))
1356 		return true;
1357 
1358 	if (flags & TTU_SPLIT_HUGE_PMD) {
1359 		split_huge_pmd_address(vma, address,
1360 				flags & TTU_SPLIT_FREEZE, page);
1361 	}
1362 
1363 	/*
1364 	 * We have to assume the worse case ie pmd for invalidation. Note that
1365 	 * the page can not be free in this function as call of try_to_unmap()
1366 	 * must hold a reference on the page.
1367 	 */
1368 	end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
1369 	mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
1370 
1371 	while (page_vma_mapped_walk(&pvmw)) {
1372 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1373 		/* PMD-mapped THP migration entry */
1374 		if (!pvmw.pte && (flags & TTU_MIGRATION)) {
1375 			VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
1376 
1377 			set_pmd_migration_entry(&pvmw, page);
1378 			continue;
1379 		}
1380 #endif
1381 
1382 		/*
1383 		 * If the page is mlock()d, we cannot swap it out.
1384 		 * If it's recently referenced (perhaps page_referenced
1385 		 * skipped over this mm) then we should reactivate it.
1386 		 */
1387 		if (!(flags & TTU_IGNORE_MLOCK)) {
1388 			if (vma->vm_flags & VM_LOCKED) {
1389 				/* PTE-mapped THP are never mlocked */
1390 				if (!PageTransCompound(page)) {
1391 					/*
1392 					 * Holding pte lock, we do *not* need
1393 					 * mmap_sem here
1394 					 */
1395 					mlock_vma_page(page);
1396 				}
1397 				ret = false;
1398 				page_vma_mapped_walk_done(&pvmw);
1399 				break;
1400 			}
1401 			if (flags & TTU_MUNLOCK)
1402 				continue;
1403 		}
1404 
1405 		/* Unexpected PMD-mapped THP? */
1406 		VM_BUG_ON_PAGE(!pvmw.pte, page);
1407 
1408 		subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
1409 		address = pvmw.address;
1410 
1411 
1412 		if (IS_ENABLED(CONFIG_MIGRATION) &&
1413 		    (flags & TTU_MIGRATION) &&
1414 		    is_zone_device_page(page)) {
1415 			swp_entry_t entry;
1416 			pte_t swp_pte;
1417 
1418 			pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.pte);
1419 
1420 			/*
1421 			 * Store the pfn of the page in a special migration
1422 			 * pte. do_swap_page() will wait until the migration
1423 			 * pte is removed and then restart fault handling.
1424 			 */
1425 			entry = make_migration_entry(page, 0);
1426 			swp_pte = swp_entry_to_pte(entry);
1427 			if (pte_soft_dirty(pteval))
1428 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
1429 			set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
1430 			/*
1431 			 * No need to invalidate here it will synchronize on
1432 			 * against the special swap migration pte.
1433 			 */
1434 			goto discard;
1435 		}
1436 
1437 		if (!(flags & TTU_IGNORE_ACCESS)) {
1438 			if (ptep_clear_flush_young_notify(vma, address,
1439 						pvmw.pte)) {
1440 				ret = false;
1441 				page_vma_mapped_walk_done(&pvmw);
1442 				break;
1443 			}
1444 		}
1445 
1446 		/* Nuke the page table entry. */
1447 		flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
1448 		if (should_defer_flush(mm, flags)) {
1449 			/*
1450 			 * We clear the PTE but do not flush so potentially
1451 			 * a remote CPU could still be writing to the page.
1452 			 * If the entry was previously clean then the
1453 			 * architecture must guarantee that a clear->dirty
1454 			 * transition on a cached TLB entry is written through
1455 			 * and traps if the PTE is unmapped.
1456 			 */
1457 			pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1458 
1459 			set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
1460 		} else {
1461 			pteval = ptep_clear_flush(vma, address, pvmw.pte);
1462 		}
1463 
1464 		/* Move the dirty bit to the page. Now the pte is gone. */
1465 		if (pte_dirty(pteval))
1466 			set_page_dirty(page);
1467 
1468 		/* Update high watermark before we lower rss */
1469 		update_hiwater_rss(mm);
1470 
1471 		if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1472 			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
1473 			if (PageHuge(page)) {
1474 				int nr = 1 << compound_order(page);
1475 				hugetlb_count_sub(nr, mm);
1476 				set_huge_swap_pte_at(mm, address,
1477 						     pvmw.pte, pteval,
1478 						     vma_mmu_pagesize(vma));
1479 			} else {
1480 				dec_mm_counter(mm, mm_counter(page));
1481 				set_pte_at(mm, address, pvmw.pte, pteval);
1482 			}
1483 
1484 		} else if (pte_unused(pteval)) {
1485 			/*
1486 			 * The guest indicated that the page content is of no
1487 			 * interest anymore. Simply discard the pte, vmscan
1488 			 * will take care of the rest.
1489 			 */
1490 			dec_mm_counter(mm, mm_counter(page));
1491 			/* We have to invalidate as we cleared the pte */
1492 			mmu_notifier_invalidate_range(mm, address,
1493 						      address + PAGE_SIZE);
1494 		} else if (IS_ENABLED(CONFIG_MIGRATION) &&
1495 				(flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) {
1496 			swp_entry_t entry;
1497 			pte_t swp_pte;
1498 
1499 			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1500 				set_pte_at(mm, address, pvmw.pte, pteval);
1501 				ret = false;
1502 				page_vma_mapped_walk_done(&pvmw);
1503 				break;
1504 			}
1505 
1506 			/*
1507 			 * Store the pfn of the page in a special migration
1508 			 * pte. do_swap_page() will wait until the migration
1509 			 * pte is removed and then restart fault handling.
1510 			 */
1511 			entry = make_migration_entry(subpage,
1512 					pte_write(pteval));
1513 			swp_pte = swp_entry_to_pte(entry);
1514 			if (pte_soft_dirty(pteval))
1515 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
1516 			set_pte_at(mm, address, pvmw.pte, swp_pte);
1517 			/*
1518 			 * No need to invalidate here it will synchronize on
1519 			 * against the special swap migration pte.
1520 			 */
1521 		} else if (PageAnon(page)) {
1522 			swp_entry_t entry = { .val = page_private(subpage) };
1523 			pte_t swp_pte;
1524 			/*
1525 			 * Store the swap location in the pte.
1526 			 * See handle_pte_fault() ...
1527 			 */
1528 			if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
1529 				WARN_ON_ONCE(1);
1530 				ret = false;
1531 				/* We have to invalidate as we cleared the pte */
1532 				mmu_notifier_invalidate_range(mm, address,
1533 							address + PAGE_SIZE);
1534 				page_vma_mapped_walk_done(&pvmw);
1535 				break;
1536 			}
1537 
1538 			/* MADV_FREE page check */
1539 			if (!PageSwapBacked(page)) {
1540 				if (!PageDirty(page)) {
1541 					/* Invalidate as we cleared the pte */
1542 					mmu_notifier_invalidate_range(mm,
1543 						address, address + PAGE_SIZE);
1544 					dec_mm_counter(mm, MM_ANONPAGES);
1545 					goto discard;
1546 				}
1547 
1548 				/*
1549 				 * If the page was redirtied, it cannot be
1550 				 * discarded. Remap the page to page table.
1551 				 */
1552 				set_pte_at(mm, address, pvmw.pte, pteval);
1553 				SetPageSwapBacked(page);
1554 				ret = false;
1555 				page_vma_mapped_walk_done(&pvmw);
1556 				break;
1557 			}
1558 
1559 			if (swap_duplicate(entry) < 0) {
1560 				set_pte_at(mm, address, pvmw.pte, pteval);
1561 				ret = false;
1562 				page_vma_mapped_walk_done(&pvmw);
1563 				break;
1564 			}
1565 			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1566 				set_pte_at(mm, address, pvmw.pte, pteval);
1567 				ret = false;
1568 				page_vma_mapped_walk_done(&pvmw);
1569 				break;
1570 			}
1571 			if (list_empty(&mm->mmlist)) {
1572 				spin_lock(&mmlist_lock);
1573 				if (list_empty(&mm->mmlist))
1574 					list_add(&mm->mmlist, &init_mm.mmlist);
1575 				spin_unlock(&mmlist_lock);
1576 			}
1577 			dec_mm_counter(mm, MM_ANONPAGES);
1578 			inc_mm_counter(mm, MM_SWAPENTS);
1579 			swp_pte = swp_entry_to_pte(entry);
1580 			if (pte_soft_dirty(pteval))
1581 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
1582 			set_pte_at(mm, address, pvmw.pte, swp_pte);
1583 			/* Invalidate as we cleared the pte */
1584 			mmu_notifier_invalidate_range(mm, address,
1585 						      address + PAGE_SIZE);
1586 		} else {
1587 			/*
1588 			 * We should not need to notify here as we reach this
1589 			 * case only from freeze_page() itself only call from
1590 			 * split_huge_page_to_list() so everything below must
1591 			 * be true:
1592 			 *   - page is not anonymous
1593 			 *   - page is locked
1594 			 *
1595 			 * So as it is a locked file back page thus it can not
1596 			 * be remove from the page cache and replace by a new
1597 			 * page before mmu_notifier_invalidate_range_end so no
1598 			 * concurrent thread might update its page table to
1599 			 * point at new page while a device still is using this
1600 			 * page.
1601 			 *
1602 			 * See Documentation/vm/mmu_notifier.rst
1603 			 */
1604 			dec_mm_counter(mm, mm_counter_file(page));
1605 		}
1606 discard:
1607 		/*
1608 		 * No need to call mmu_notifier_invalidate_range() it has be
1609 		 * done above for all cases requiring it to happen under page
1610 		 * table lock before mmu_notifier_invalidate_range_end()
1611 		 *
1612 		 * See Documentation/vm/mmu_notifier.rst
1613 		 */
1614 		page_remove_rmap(subpage, PageHuge(page));
1615 		put_page(page);
1616 	}
1617 
1618 	mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
1619 
1620 	return ret;
1621 }
1622 
1623 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1624 {
1625 	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1626 
1627 	if (!maybe_stack)
1628 		return false;
1629 
1630 	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1631 						VM_STACK_INCOMPLETE_SETUP)
1632 		return true;
1633 
1634 	return false;
1635 }
1636 
1637 static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1638 {
1639 	return is_vma_temporary_stack(vma);
1640 }
1641 
1642 static int page_mapcount_is_zero(struct page *page)
1643 {
1644 	return !total_mapcount(page);
1645 }
1646 
1647 /**
1648  * try_to_unmap - try to remove all page table mappings to a page
1649  * @page: the page to get unmapped
1650  * @flags: action and flags
1651  *
1652  * Tries to remove all the page table entries which are mapping this
1653  * page, used in the pageout path.  Caller must hold the page lock.
1654  *
1655  * If unmap is successful, return true. Otherwise, false.
1656  */
1657 bool try_to_unmap(struct page *page, enum ttu_flags flags)
1658 {
1659 	struct rmap_walk_control rwc = {
1660 		.rmap_one = try_to_unmap_one,
1661 		.arg = (void *)flags,
1662 		.done = page_mapcount_is_zero,
1663 		.anon_lock = page_lock_anon_vma_read,
1664 	};
1665 
1666 	/*
1667 	 * During exec, a temporary VMA is setup and later moved.
1668 	 * The VMA is moved under the anon_vma lock but not the
1669 	 * page tables leading to a race where migration cannot
1670 	 * find the migration ptes. Rather than increasing the
1671 	 * locking requirements of exec(), migration skips
1672 	 * temporary VMAs until after exec() completes.
1673 	 */
1674 	if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))
1675 	    && !PageKsm(page) && PageAnon(page))
1676 		rwc.invalid_vma = invalid_migration_vma;
1677 
1678 	if (flags & TTU_RMAP_LOCKED)
1679 		rmap_walk_locked(page, &rwc);
1680 	else
1681 		rmap_walk(page, &rwc);
1682 
1683 	return !page_mapcount(page) ? true : false;
1684 }
1685 
1686 static int page_not_mapped(struct page *page)
1687 {
1688 	return !page_mapped(page);
1689 };
1690 
1691 /**
1692  * try_to_munlock - try to munlock a page
1693  * @page: the page to be munlocked
1694  *
1695  * Called from munlock code.  Checks all of the VMAs mapping the page
1696  * to make sure nobody else has this page mlocked. The page will be
1697  * returned with PG_mlocked cleared if no other vmas have it mlocked.
1698  */
1699 
1700 void try_to_munlock(struct page *page)
1701 {
1702 	struct rmap_walk_control rwc = {
1703 		.rmap_one = try_to_unmap_one,
1704 		.arg = (void *)TTU_MUNLOCK,
1705 		.done = page_not_mapped,
1706 		.anon_lock = page_lock_anon_vma_read,
1707 
1708 	};
1709 
1710 	VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
1711 	VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
1712 
1713 	rmap_walk(page, &rwc);
1714 }
1715 
1716 void __put_anon_vma(struct anon_vma *anon_vma)
1717 {
1718 	struct anon_vma *root = anon_vma->root;
1719 
1720 	anon_vma_free(anon_vma);
1721 	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1722 		anon_vma_free(root);
1723 }
1724 
1725 static struct anon_vma *rmap_walk_anon_lock(struct page *page,
1726 					struct rmap_walk_control *rwc)
1727 {
1728 	struct anon_vma *anon_vma;
1729 
1730 	if (rwc->anon_lock)
1731 		return rwc->anon_lock(page);
1732 
1733 	/*
1734 	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1735 	 * because that depends on page_mapped(); but not all its usages
1736 	 * are holding mmap_sem. Users without mmap_sem are required to
1737 	 * take a reference count to prevent the anon_vma disappearing
1738 	 */
1739 	anon_vma = page_anon_vma(page);
1740 	if (!anon_vma)
1741 		return NULL;
1742 
1743 	anon_vma_lock_read(anon_vma);
1744 	return anon_vma;
1745 }
1746 
1747 /*
1748  * rmap_walk_anon - do something to anonymous page using the object-based
1749  * rmap method
1750  * @page: the page to be handled
1751  * @rwc: control variable according to each walk type
1752  *
1753  * Find all the mappings of a page using the mapping pointer and the vma chains
1754  * contained in the anon_vma struct it points to.
1755  *
1756  * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1757  * where the page was found will be held for write.  So, we won't recheck
1758  * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
1759  * LOCKED.
1760  */
1761 static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
1762 		bool locked)
1763 {
1764 	struct anon_vma *anon_vma;
1765 	pgoff_t pgoff_start, pgoff_end;
1766 	struct anon_vma_chain *avc;
1767 
1768 	if (locked) {
1769 		anon_vma = page_anon_vma(page);
1770 		/* anon_vma disappear under us? */
1771 		VM_BUG_ON_PAGE(!anon_vma, page);
1772 	} else {
1773 		anon_vma = rmap_walk_anon_lock(page, rwc);
1774 	}
1775 	if (!anon_vma)
1776 		return;
1777 
1778 	pgoff_start = page_to_pgoff(page);
1779 	pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
1780 	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
1781 			pgoff_start, pgoff_end) {
1782 		struct vm_area_struct *vma = avc->vma;
1783 		unsigned long address = vma_address(page, vma);
1784 
1785 		cond_resched();
1786 
1787 		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1788 			continue;
1789 
1790 		if (!rwc->rmap_one(page, vma, address, rwc->arg))
1791 			break;
1792 		if (rwc->done && rwc->done(page))
1793 			break;
1794 	}
1795 
1796 	if (!locked)
1797 		anon_vma_unlock_read(anon_vma);
1798 }
1799 
1800 /*
1801  * rmap_walk_file - do something to file page using the object-based rmap method
1802  * @page: the page to be handled
1803  * @rwc: control variable according to each walk type
1804  *
1805  * Find all the mappings of a page using the mapping pointer and the vma chains
1806  * contained in the address_space struct it points to.
1807  *
1808  * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1809  * where the page was found will be held for write.  So, we won't recheck
1810  * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
1811  * LOCKED.
1812  */
1813 static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
1814 		bool locked)
1815 {
1816 	struct address_space *mapping = page_mapping(page);
1817 	pgoff_t pgoff_start, pgoff_end;
1818 	struct vm_area_struct *vma;
1819 
1820 	/*
1821 	 * The page lock not only makes sure that page->mapping cannot
1822 	 * suddenly be NULLified by truncation, it makes sure that the
1823 	 * structure at mapping cannot be freed and reused yet,
1824 	 * so we can safely take mapping->i_mmap_rwsem.
1825 	 */
1826 	VM_BUG_ON_PAGE(!PageLocked(page), page);
1827 
1828 	if (!mapping)
1829 		return;
1830 
1831 	pgoff_start = page_to_pgoff(page);
1832 	pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
1833 	if (!locked)
1834 		i_mmap_lock_read(mapping);
1835 	vma_interval_tree_foreach(vma, &mapping->i_mmap,
1836 			pgoff_start, pgoff_end) {
1837 		unsigned long address = vma_address(page, vma);
1838 
1839 		cond_resched();
1840 
1841 		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1842 			continue;
1843 
1844 		if (!rwc->rmap_one(page, vma, address, rwc->arg))
1845 			goto done;
1846 		if (rwc->done && rwc->done(page))
1847 			goto done;
1848 	}
1849 
1850 done:
1851 	if (!locked)
1852 		i_mmap_unlock_read(mapping);
1853 }
1854 
1855 void rmap_walk(struct page *page, struct rmap_walk_control *rwc)
1856 {
1857 	if (unlikely(PageKsm(page)))
1858 		rmap_walk_ksm(page, rwc);
1859 	else if (PageAnon(page))
1860 		rmap_walk_anon(page, rwc, false);
1861 	else
1862 		rmap_walk_file(page, rwc, false);
1863 }
1864 
1865 /* Like rmap_walk, but caller holds relevant rmap lock */
1866 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
1867 {
1868 	/* no ksm support for now */
1869 	VM_BUG_ON_PAGE(PageKsm(page), page);
1870 	if (PageAnon(page))
1871 		rmap_walk_anon(page, rwc, true);
1872 	else
1873 		rmap_walk_file(page, rwc, true);
1874 }
1875 
1876 #ifdef CONFIG_HUGETLB_PAGE
1877 /*
1878  * The following three functions are for anonymous (private mapped) hugepages.
1879  * Unlike common anonymous pages, anonymous hugepages have no accounting code
1880  * and no lru code, because we handle hugepages differently from common pages.
1881  */
1882 static void __hugepage_set_anon_rmap(struct page *page,
1883 	struct vm_area_struct *vma, unsigned long address, int exclusive)
1884 {
1885 	struct anon_vma *anon_vma = vma->anon_vma;
1886 
1887 	BUG_ON(!anon_vma);
1888 
1889 	if (PageAnon(page))
1890 		return;
1891 	if (!exclusive)
1892 		anon_vma = anon_vma->root;
1893 
1894 	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1895 	page->mapping = (struct address_space *) anon_vma;
1896 	page->index = linear_page_index(vma, address);
1897 }
1898 
1899 void hugepage_add_anon_rmap(struct page *page,
1900 			    struct vm_area_struct *vma, unsigned long address)
1901 {
1902 	struct anon_vma *anon_vma = vma->anon_vma;
1903 	int first;
1904 
1905 	BUG_ON(!PageLocked(page));
1906 	BUG_ON(!anon_vma);
1907 	/* address might be in next vma when migration races vma_adjust */
1908 	first = atomic_inc_and_test(compound_mapcount_ptr(page));
1909 	if (first)
1910 		__hugepage_set_anon_rmap(page, vma, address, 0);
1911 }
1912 
1913 void hugepage_add_new_anon_rmap(struct page *page,
1914 			struct vm_area_struct *vma, unsigned long address)
1915 {
1916 	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1917 	atomic_set(compound_mapcount_ptr(page), 0);
1918 	__hugepage_set_anon_rmap(page, vma, address, 1);
1919 }
1920 #endif /* CONFIG_HUGETLB_PAGE */
1921