1	/*
2	* mm/rmap.c - physical to virtual reverse mappings
3	*
4	* Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5	* Released under the General Public License (GPL).
6	*
7	* Simple, low overhead reverse mapping scheme.
8	* Please try to keep this thing as modular as possible.
9	*
10	* Provides methods for unmapping each kind of mapped page:
11	* the anon methods track anonymous pages, and
12	* the file methods track pages belonging to an inode.
13	*
14	* Original design by Rik van Riel <riel@conectiva.com.br> 2001
15	* File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
16	* Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
17	* Contributions by Hugh Dickins 2003, 2004
18	*/
19
20	/*
21	* Lock ordering in mm:
22	*
23	* inode->i_rwsem (while writing or truncating, not reading or faulting)
24	* mm->mmap_lock
25	* mapping->invalidate_lock (in filemap_fault)
26	* page->flags PG_locked (lock_page)
27	* hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
28	* vma_start_write
29	* mapping->i_mmap_rwsem
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 block_dirty_folio)
35	* folio_lock_memcg move_lock (in block_dirty_folio)
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() take locks in this order:
50	* hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
51	* vma_lock (hugetlb specific lock for pmd_sharing)
52	* mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
53	* page->flags PG_locked (lock_page)
54	*/
55
56	#include <linux/mm.h>
57	#include <linux/sched/mm.h>
58	#include <linux/sched/task.h>
59	#include <linux/pagemap.h>
60	#include <linux/swap.h>
61	#include <linux/swapops.h>
62	#include <linux/slab.h>
63	#include <linux/init.h>
64	#include <linux/ksm.h>
65	#include <linux/rmap.h>
66	#include <linux/rcupdate.h>
67	#include <linux/export.h>
68	#include <linux/memcontrol.h>
69	#include <linux/mmu_notifier.h>
70	#include <linux/migrate.h>
71	#include <linux/hugetlb.h>
72	#include <linux/huge_mm.h>
73	#include <linux/backing-dev.h>
74	#include <linux/page_idle.h>
75	#include <linux/memremap.h>
76	#include <linux/userfaultfd_k.h>
77	#include <linux/mm_inline.h>
78
79	#include <asm/tlbflush.h>
80
81	#define CREATE_TRACE_POINTS
82	#include <trace/events/tlb.h>
83	#include <trace/events/migrate.h>
84
85	#include "internal.h"
86
87	static struct kmem_cache *anon_vma_cachep;
88	static struct kmem_cache *anon_vma_chain_cachep;
89
90	static inline struct anon_vma *anon_vma_alloc(void)
91	{
92	struct anon_vma *anon_vma;
93
94	anon_vma = kmem_cache_alloc(cachep: anon_vma_cachep, GFP_KERNEL);
95	if (anon_vma) {
96	atomic_set(v: &anon_vma->refcount, i: 1);
97	anon_vma->num_children = 0;
98	anon_vma->num_active_vmas = 0;
99	anon_vma->parent = anon_vma;
100	/*
101	* Initialise the anon_vma root to point to itself. If called
102	* from fork, the root will be reset to the parents anon_vma.
103	*/
104	anon_vma->root = anon_vma;
105	}
106
107	return anon_vma;
108	}
109
110	static inline void anon_vma_free(struct anon_vma *anon_vma)
111	{
112	VM_BUG_ON(atomic_read(&anon_vma->refcount));
113
114	/*
115	* Synchronize against folio_lock_anon_vma_read() such that
116	* we can safely hold the lock without the anon_vma getting
117	* freed.
118	*
119	* Relies on the full mb implied by the atomic_dec_and_test() from
120	* put_anon_vma() against the acquire barrier implied by
121	* down_read_trylock() from folio_lock_anon_vma_read(). This orders:
122	*
123	* folio_lock_anon_vma_read() VS put_anon_vma()
124	* down_read_trylock() atomic_dec_and_test()
125	* LOCK MB
126	* atomic_read() rwsem_is_locked()
127	*
128	* LOCK should suffice since the actual taking of the lock must
129	* happen _before_ what follows.
130	*/
131	might_sleep();
132	if (rwsem_is_locked(sem: &anon_vma->root->rwsem)) {
133	anon_vma_lock_write(anon_vma);
134	anon_vma_unlock_write(anon_vma);
135	}
136
137	kmem_cache_free(s: anon_vma_cachep, objp: anon_vma);
138	}
139
140	static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
141	{
142	return kmem_cache_alloc(cachep: anon_vma_chain_cachep, flags: gfp);
143	}
144
145	static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
146	{
147	kmem_cache_free(s: anon_vma_chain_cachep, objp: anon_vma_chain);
148	}
149
150	static void anon_vma_chain_link(struct vm_area_struct *vma,
151	struct anon_vma_chain *avc,
152	struct anon_vma *anon_vma)
153	{
154	avc->vma = vma;
155	avc->anon_vma = anon_vma;
156	list_add(new: &avc->same_vma, head: &vma->anon_vma_chain);
157	anon_vma_interval_tree_insert(node: avc, root: &anon_vma->rb_root);
158	}
159
160	/**
161	* __anon_vma_prepare - attach an anon_vma to a memory region
162	* @vma: the memory region in question
163	*
164	* This makes sure the memory mapping described by 'vma' has
165	* an 'anon_vma' attached to it, so that we can associate the
166	* anonymous pages mapped into it with that anon_vma.
167	*
168	* The common case will be that we already have one, which
169	* is handled inline by anon_vma_prepare(). But if
170	* not we either need to find an adjacent mapping that we
171	* can re-use the anon_vma from (very common when the only
172	* reason for splitting a vma has been mprotect()), or we
173	* allocate a new one.
174	*
175	* Anon-vma allocations are very subtle, because we may have
176	* optimistically looked up an anon_vma in folio_lock_anon_vma_read()
177	* and that may actually touch the rwsem even in the newly
178	* allocated vma (it depends on RCU to make sure that the
179	* anon_vma isn't actually destroyed).
180	*
181	* As a result, we need to do proper anon_vma locking even
182	* for the new allocation. At the same time, we do not want
183	* to do any locking for the common case of already having
184	* an anon_vma.
185	*
186	* This must be called with the mmap_lock held for reading.
187	*/
188	int __anon_vma_prepare(struct vm_area_struct *vma)
189	{
190	struct mm_struct *mm = vma->vm_mm;
191	struct anon_vma *anon_vma, *allocated;
192	struct anon_vma_chain *avc;
193
194	might_sleep();
195
196	avc = anon_vma_chain_alloc(GFP_KERNEL);
197	if (!avc)
198	goto out_enomem;
199
200	anon_vma = find_mergeable_anon_vma(vma);
201	allocated = NULL;
202	if (!anon_vma) {
203	anon_vma = anon_vma_alloc();
204	if (unlikely(!anon_vma))
205	goto out_enomem_free_avc;
206	anon_vma->num_children++; /* self-parent link for new root */
207	allocated = anon_vma;
208	}
209
210	anon_vma_lock_write(anon_vma);
211	/* page_table_lock to protect against threads */
212	spin_lock(lock: &mm->page_table_lock);
213	if (likely(!vma->anon_vma)) {
214	vma->anon_vma = anon_vma;
215	anon_vma_chain_link(vma, avc, anon_vma);
216	anon_vma->num_active_vmas++;
217	allocated = NULL;
218	avc = NULL;
219	}
220	spin_unlock(lock: &mm->page_table_lock);
221	anon_vma_unlock_write(anon_vma);
222
223	if (unlikely(allocated))
224	put_anon_vma(anon_vma: allocated);
225	if (unlikely(avc))
226	anon_vma_chain_free(anon_vma_chain: avc);
227
228	return 0;
229
230	out_enomem_free_avc:
231	anon_vma_chain_free(anon_vma_chain: avc);
232	out_enomem:
233	return -ENOMEM;
234	}
235
236	/*
237	* This is a useful helper function for locking the anon_vma root as
238	* we traverse the vma->anon_vma_chain, looping over anon_vma's that
239	* have the same vma.
240	*
241	* Such anon_vma's should have the same root, so you'd expect to see
242	* just a single mutex_lock for the whole traversal.
243	*/
244	static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
245	{
246	struct anon_vma *new_root = anon_vma->root;
247	if (new_root != root) {
248	if (WARN_ON_ONCE(root))
249	up_write(sem: &root->rwsem);
250	root = new_root;
251	down_write(sem: &root->rwsem);
252	}
253	return root;
254	}
255
256	static inline void unlock_anon_vma_root(struct anon_vma *root)
257	{
258	if (root)
259	up_write(sem: &root->rwsem);
260	}
261
262	/*
263	* Attach the anon_vmas from src to dst.
264	* Returns 0 on success, -ENOMEM on failure.
265	*
266	* anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(),
267	* copy_vma() and anon_vma_fork(). The first four want an exact copy of src,
268	* while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to
269	* prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before
270	* call, we can identify this case by checking (!dst->anon_vma &&
271	* src->anon_vma).
272	*
273	* If (!dst->anon_vma && src->anon_vma) is true, this function tries to find
274	* and reuse existing anon_vma which has no vmas and only one child anon_vma.
275	* This prevents degradation of anon_vma hierarchy to endless linear chain in
276	* case of constantly forking task. On the other hand, an anon_vma with more
277	* than one child isn't reused even if there was no alive vma, thus rmap
278	* walker has a good chance of avoiding scanning the whole hierarchy when it
279	* searches where page is mapped.
280	*/
281	int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
282	{
283	struct anon_vma_chain *avc, *pavc;
284	struct anon_vma *root = NULL;
285
286	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
287	struct anon_vma *anon_vma;
288
289	avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
290	if (unlikely(!avc)) {
291	unlock_anon_vma_root(root);
292	root = NULL;
293	avc = anon_vma_chain_alloc(GFP_KERNEL);
294	if (!avc)
295	goto enomem_failure;
296	}
297	anon_vma = pavc->anon_vma;
298	root = lock_anon_vma_root(root, anon_vma);
299	anon_vma_chain_link(vma: dst, avc, anon_vma);
300
301	/*
302	* Reuse existing anon_vma if it has no vma and only one
303	* anon_vma child.
304	*
305	* Root anon_vma is never reused:
306	* it has self-parent reference and at least one child.
307	*/
308	if (!dst->anon_vma && src->anon_vma &&
309	anon_vma->num_children < 2 &&
310	anon_vma->num_active_vmas == 0)
311	dst->anon_vma = anon_vma;
312	}
313	if (dst->anon_vma)
314	dst->anon_vma->num_active_vmas++;
315	unlock_anon_vma_root(root);
316	return 0;
317
318	enomem_failure:
319	/*
320	* dst->anon_vma is dropped here otherwise its num_active_vmas can
321	* be incorrectly decremented in unlink_anon_vmas().
322	* We can safely do this because callers of anon_vma_clone() don't care
323	* about dst->anon_vma if anon_vma_clone() failed.
324	*/
325	dst->anon_vma = NULL;
326	unlink_anon_vmas(dst);
327	return -ENOMEM;
328	}
329
330	/*
331	* Attach vma to its own anon_vma, as well as to the anon_vmas that
332	* the corresponding VMA in the parent process is attached to.
333	* Returns 0 on success, non-zero on failure.
334	*/
335	int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
336	{
337	struct anon_vma_chain *avc;
338	struct anon_vma *anon_vma;
339	int error;
340
341	/* Don't bother if the parent process has no anon_vma here. */
342	if (!pvma->anon_vma)
343	return 0;
344
345	/* Drop inherited anon_vma, we'll reuse existing or allocate new. */
346	vma->anon_vma = NULL;
347
348	/*
349	* First, attach the new VMA to the parent VMA's anon_vmas,
350	* so rmap can find non-COWed pages in child processes.
351	*/
352	error = anon_vma_clone(dst: vma, src: pvma);
353	if (error)
354	return error;
355
356	/* An existing anon_vma has been reused, all done then. */
357	if (vma->anon_vma)
358	return 0;
359
360	/* Then add our own anon_vma. */
361	anon_vma = anon_vma_alloc();
362	if (!anon_vma)
363	goto out_error;
364	anon_vma->num_active_vmas++;
365	avc = anon_vma_chain_alloc(GFP_KERNEL);
366	if (!avc)
367	goto out_error_free_anon_vma;
368
369	/*
370	* The root anon_vma's rwsem is the lock actually used when we
371	* lock any of the anon_vmas in this anon_vma tree.
372	*/
373	anon_vma->root = pvma->anon_vma->root;
374	anon_vma->parent = pvma->anon_vma;
375	/*
376	* With refcounts, an anon_vma can stay around longer than the
377	* process it belongs to. The root anon_vma needs to be pinned until
378	* this anon_vma is freed, because the lock lives in the root.
379	*/
380	get_anon_vma(anon_vma: anon_vma->root);
381	/* Mark this anon_vma as the one where our new (COWed) pages go. */
382	vma->anon_vma = anon_vma;
383	anon_vma_lock_write(anon_vma);
384	anon_vma_chain_link(vma, avc, anon_vma);
385	anon_vma->parent->num_children++;
386	anon_vma_unlock_write(anon_vma);
387
388	return 0;
389
390	out_error_free_anon_vma:
391	put_anon_vma(anon_vma);
392	out_error:
393	unlink_anon_vmas(vma);
394	return -ENOMEM;
395	}
396
397	void unlink_anon_vmas(struct vm_area_struct *vma)
398	{
399	struct anon_vma_chain *avc, *next;
400	struct anon_vma *root = NULL;
401
402	/*
403	* Unlink each anon_vma chained to the VMA. This list is ordered
404	* from newest to oldest, ensuring the root anon_vma gets freed last.
405	*/
406	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
407	struct anon_vma *anon_vma = avc->anon_vma;
408
409	root = lock_anon_vma_root(root, anon_vma);
410	anon_vma_interval_tree_remove(node: avc, root: &anon_vma->rb_root);
411
412	/*
413	* Leave empty anon_vmas on the list - we'll need
414	* to free them outside the lock.
415	*/
416	if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
417	anon_vma->parent->num_children--;
418	continue;
419	}
420
421	list_del(entry: &avc->same_vma);
422	anon_vma_chain_free(anon_vma_chain: avc);
423	}
424	if (vma->anon_vma) {
425	vma->anon_vma->num_active_vmas--;
426
427	/*
428	* vma would still be needed after unlink, and anon_vma will be prepared
429	* when handle fault.
430	*/
431	vma->anon_vma = NULL;
432	}
433	unlock_anon_vma_root(root);
434
435	/*
436	* Iterate the list once more, it now only contains empty and unlinked
437	* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
438	* needing to write-acquire the anon_vma->root->rwsem.
439	*/
440	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
441	struct anon_vma *anon_vma = avc->anon_vma;
442
443	VM_WARN_ON(anon_vma->num_children);
444	VM_WARN_ON(anon_vma->num_active_vmas);
445	put_anon_vma(anon_vma);
446
447	list_del(entry: &avc->same_vma);
448	anon_vma_chain_free(anon_vma_chain: avc);
449	}
450	}
451
452	static void anon_vma_ctor(void *data)
453	{
454	struct anon_vma *anon_vma = data;
455
456	init_rwsem(&anon_vma->rwsem);
457	atomic_set(v: &anon_vma->refcount, i: 0);
458	anon_vma->rb_root = RB_ROOT_CACHED;
459	}
460
461	void __init anon_vma_init(void)
462	{
463	anon_vma_cachep = kmem_cache_create(name: "anon_vma", size: sizeof(struct anon_vma),
464	align: 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
465	ctor: anon_vma_ctor);
466	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
467	SLAB_PANIC|SLAB_ACCOUNT);
468	}
469
470	/*
471	* Getting a lock on a stable anon_vma from a page off the LRU is tricky!
472	*
473	* Since there is no serialization what so ever against page_remove_rmap()
474	* the best this function can do is return a refcount increased anon_vma
475	* that might have been relevant to this page.
476	*
477	* The page might have been remapped to a different anon_vma or the anon_vma
478	* returned may already be freed (and even reused).
479	*
480	* In case it was remapped to a different anon_vma, the new anon_vma will be a
481	* child of the old anon_vma, and the anon_vma lifetime rules will therefore
482	* ensure that any anon_vma obtained from the page will still be valid for as
483	* long as we observe page_mapped() [ hence all those page_mapped() tests ].
484	*
485	* All users of this function must be very careful when walking the anon_vma
486	* chain and verify that the page in question is indeed mapped in it
487	* [ something equivalent to page_mapped_in_vma() ].
488	*
489	* Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from
490	* page_remove_rmap() that the anon_vma pointer from page->mapping is valid
491	* if there is a mapcount, we can dereference the anon_vma after observing
492	* those.
493	*/
494	struct anon_vma *folio_get_anon_vma(struct folio *folio)
495	{
496	struct anon_vma *anon_vma = NULL;
497	unsigned long anon_mapping;
498
499	rcu_read_lock();
500	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
501	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
502	goto out;
503	if (!folio_mapped(folio))
504	goto out;
505
506	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
507	if (!atomic_inc_not_zero(v: &anon_vma->refcount)) {
508	anon_vma = NULL;
509	goto out;
510	}
511
512	/*
513	* If this folio is still mapped, then its anon_vma cannot have been
514	* freed. But if it has been unmapped, we have no security against the
515	* anon_vma structure being freed and reused (for another anon_vma:
516	* SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
517	* above cannot corrupt).
518	*/
519	if (!folio_mapped(folio)) {
520	rcu_read_unlock();
521	put_anon_vma(anon_vma);
522	return NULL;
523	}
524	out:
525	rcu_read_unlock();
526
527	return anon_vma;
528	}
529
530	/*
531	* Similar to folio_get_anon_vma() except it locks the anon_vma.
532	*
533	* Its a little more complex as it tries to keep the fast path to a single
534	* atomic op -- the trylock. If we fail the trylock, we fall back to getting a
535	* reference like with folio_get_anon_vma() and then block on the mutex
536	* on !rwc->try_lock case.
537	*/
538	struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
539	struct rmap_walk_control *rwc)
540	{
541	struct anon_vma *anon_vma = NULL;
542	struct anon_vma *root_anon_vma;
543	unsigned long anon_mapping;
544
545	rcu_read_lock();
546	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
547	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
548	goto out;
549	if (!folio_mapped(folio))
550	goto out;
551
552	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
553	root_anon_vma = READ_ONCE(anon_vma->root);
554	if (down_read_trylock(sem: &root_anon_vma->rwsem)) {
555	/*
556	* If the folio is still mapped, then this anon_vma is still
557	* its anon_vma, and holding the mutex ensures that it will
558	* not go away, see anon_vma_free().
559	*/
560	if (!folio_mapped(folio)) {
561	up_read(sem: &root_anon_vma->rwsem);
562	anon_vma = NULL;
563	}
564	goto out;
565	}
566
567	if (rwc && rwc->try_lock) {
568	anon_vma = NULL;
569	rwc->contended = true;
570	goto out;
571	}
572
573	/* trylock failed, we got to sleep */
574	if (!atomic_inc_not_zero(v: &anon_vma->refcount)) {
575	anon_vma = NULL;
576	goto out;
577	}
578
579	if (!folio_mapped(folio)) {
580	rcu_read_unlock();
581	put_anon_vma(anon_vma);
582	return NULL;
583	}
584
585	/* we pinned the anon_vma, its safe to sleep */
586	rcu_read_unlock();
587	anon_vma_lock_read(anon_vma);
588
589	if (atomic_dec_and_test(v: &anon_vma->refcount)) {
590	/*
591	* Oops, we held the last refcount, release the lock
592	* and bail -- can't simply use put_anon_vma() because
593	* we'll deadlock on the anon_vma_lock_write() recursion.
594	*/
595	anon_vma_unlock_read(anon_vma);
596	__put_anon_vma(anon_vma);
597	anon_vma = NULL;
598	}
599
600	return anon_vma;
601
602	out:
603	rcu_read_unlock();
604	return anon_vma;
605	}
606
607	#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
608	/*
609	* Flush TLB entries for recently unmapped pages from remote CPUs. It is
610	* important if a PTE was dirty when it was unmapped that it's flushed
611	* before any IO is initiated on the page to prevent lost writes. Similarly,
612	* it must be flushed before freeing to prevent data leakage.
613	*/
614	void try_to_unmap_flush(void)
615	{
616	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
617
618	if (!tlb_ubc->flush_required)
619	return;
620
621	arch_tlbbatch_flush(batch: &tlb_ubc->arch);
622	tlb_ubc->flush_required = false;
623	tlb_ubc->writable = false;
624	}
625
626	/* Flush iff there are potentially writable TLB entries that can race with IO */
627	void try_to_unmap_flush_dirty(void)
628	{
629	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
630
631	if (tlb_ubc->writable)
632	try_to_unmap_flush();
633	}
634
635	/*
636	* Bits 0-14 of mm->tlb_flush_batched record pending generations.
637	* Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
638	*/
639	#define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16
640	#define TLB_FLUSH_BATCH_PENDING_MASK \
641	((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
642	#define TLB_FLUSH_BATCH_PENDING_LARGE \
643	(TLB_FLUSH_BATCH_PENDING_MASK / 2)
644
645	static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
646	unsigned long uaddr)
647	{
648	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
649	int batch;
650	bool writable = pte_dirty(pte: pteval);
651
652	if (!pte_accessible(mm, a: pteval))
653	return;
654
655	arch_tlbbatch_add_pending(batch: &tlb_ubc->arch, mm, uaddr);
656	tlb_ubc->flush_required = true;
657
658	/*
659	* Ensure compiler does not re-order the setting of tlb_flush_batched
660	* before the PTE is cleared.
661	*/
662	barrier();
663	batch = atomic_read(v: &mm->tlb_flush_batched);
664	retry:
665	if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
666	/*
667	* Prevent `pending' from catching up with `flushed' because of
668	* overflow. Reset `pending' and `flushed' to be 1 and 0 if
669	* `pending' becomes large.
670	*/
671	if (!atomic_try_cmpxchg(v: &mm->tlb_flush_batched, old: &batch, new: 1))
672	goto retry;
673	} else {
674	atomic_inc(v: &mm->tlb_flush_batched);
675	}
676
677	/*
678	* If the PTE was dirty then it's best to assume it's writable. The
679	* caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
680	* before the page is queued for IO.
681	*/
682	if (writable)
683	tlb_ubc->writable = true;
684	}
685
686	/*
687	* Returns true if the TLB flush should be deferred to the end of a batch of
688	* unmap operations to reduce IPIs.
689	*/
690	static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
691	{
692	if (!(flags & TTU_BATCH_FLUSH))
693	return false;
694
695	return arch_tlbbatch_should_defer(mm);
696	}
697
698	/*
699	* Reclaim unmaps pages under the PTL but do not flush the TLB prior to
700	* releasing the PTL if TLB flushes are batched. It's possible for a parallel
701	* operation such as mprotect or munmap to race between reclaim unmapping
702	* the page and flushing the page. If this race occurs, it potentially allows
703	* access to data via a stale TLB entry. Tracking all mm's that have TLB
704	* batching in flight would be expensive during reclaim so instead track
705	* whether TLB batching occurred in the past and if so then do a flush here
706	* if required. This will cost one additional flush per reclaim cycle paid
707	* by the first operation at risk such as mprotect and mumap.
708	*
709	* This must be called under the PTL so that an access to tlb_flush_batched
710	* that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
711	* via the PTL.
712	*/
713	void flush_tlb_batched_pending(struct mm_struct *mm)
714	{
715	int batch = atomic_read(v: &mm->tlb_flush_batched);
716	int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
717	int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
718
719	if (pending != flushed) {
720	arch_flush_tlb_batched_pending(mm);
721	/*
722	* If the new TLB flushing is pending during flushing, leave
723	* mm->tlb_flush_batched as is, to avoid losing flushing.
724	*/
725	atomic_cmpxchg(v: &mm->tlb_flush_batched, old: batch,
726	new: pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
727	}
728	}
729	#else
730	static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
731	unsigned long uaddr)
732	{
733	}
734
735	static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
736	{
737	return false;
738	}
739	#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
740
741	/*
742	* At what user virtual address is page expected in vma?
743	* Caller should check the page is actually part of the vma.
744	*/
745	unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
746	{
747	struct folio *folio = page_folio(page);
748	if (folio_test_anon(folio)) {
749	struct anon_vma *page__anon_vma = folio_anon_vma(folio);
750	/*
751	* Note: swapoff's unuse_vma() is more efficient with this
752	* check, and needs it to match anon_vma when KSM is active.
753	*/
754	if (!vma->anon_vma || !page__anon_vma ||
755	vma->anon_vma->root != page__anon_vma->root)
756	return -EFAULT;
757	} else if (!vma->vm_file) {
758	return -EFAULT;
759	} else if (vma->vm_file->f_mapping != folio->mapping) {
760	return -EFAULT;
761	}
762
763	return vma_address(page, vma);
764	}
765
766	/*
767	* Returns the actual pmd_t* where we expect 'address' to be mapped from, or
768	* NULL if it doesn't exist. No guarantees / checks on what the pmd_t*
769	* represents.
770	*/
771	pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
772	{
773	pgd_t *pgd;
774	p4d_t *p4d;
775	pud_t *pud;
776	pmd_t *pmd = NULL;
777
778	pgd = pgd_offset(mm, address);
779	if (!pgd_present(pgd: *pgd))
780	goto out;
781
782	p4d = p4d_offset(pgd, address);
783	if (!p4d_present(p4d: *p4d))
784	goto out;
785
786	pud = pud_offset(p4d, address);
787	if (!pud_present(pud: *pud))
788	goto out;
789
790	pmd = pmd_offset(pud, address);
791	out:
792	return pmd;
793	}
794
795	struct folio_referenced_arg {
796	int mapcount;
797	int referenced;
798	unsigned long vm_flags;
799	struct mem_cgroup *memcg;
800	};
801
802	/*
803	* arg: folio_referenced_arg will be passed
804	*/
805	static bool folio_referenced_one(struct folio *folio,
806	struct vm_area_struct *vma, unsigned long address, void *arg)
807	{
808	struct folio_referenced_arg *pra = arg;
809	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
810	int referenced = 0;
811	unsigned long start = address, ptes = 0;
812
813	while (page_vma_mapped_walk(pvmw: &pvmw)) {
814	address = pvmw.address;
815
816	if (vma->vm_flags & VM_LOCKED) {
817	if (!folio_test_large(folio) || !pvmw.pte) {
818	/* Restore the mlock which got missed */
819	mlock_vma_folio(folio, vma);
820	page_vma_mapped_walk_done(pvmw: &pvmw);
821	pra->vm_flags |= VM_LOCKED;
822	return false; /* To break the loop */
823	}
824	/*
825	* For large folio fully mapped to VMA, will
826	* be handled after the pvmw loop.
827	*
828	* For large folio cross VMA boundaries, it's
829	* expected to be picked by page reclaim. But
830	* should skip reference of pages which are in
831	* the range of VM_LOCKED vma. As page reclaim
832	* should just count the reference of pages out
833	* the range of VM_LOCKED vma.
834	*/
835	ptes++;
836	pra->mapcount--;
837	continue;
838	}
839
840	if (pvmw.pte) {
841	if (lru_gen_enabled() &&
842	pte_young(pte: ptep_get(ptep: pvmw.pte))) {
843	lru_gen_look_around(pvmw: &pvmw);
844	referenced++;
845	}
846
847	if (ptep_clear_flush_young_notify(vma, address,
848	pvmw.pte))
849	referenced++;
850	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
851	if (pmdp_clear_flush_young_notify(vma, address,
852	pvmw.pmd))
853	referenced++;
854	} else {
855	/* unexpected pmd-mapped folio? */
856	WARN_ON_ONCE(1);
857	}
858
859	pra->mapcount--;
860	}
861
862	if ((vma->vm_flags & VM_LOCKED) &&
863	folio_test_large(folio) &&
864	folio_within_vma(folio, vma)) {
865	unsigned long s_align, e_align;
866
867	s_align = ALIGN_DOWN(start, PMD_SIZE);
868	e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE);
869
870	/* folio doesn't cross page table boundary and fully mapped */
871	if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) {
872	/* Restore the mlock which got missed */
873	mlock_vma_folio(folio, vma);
874	pra->vm_flags |= VM_LOCKED;
875	return false; /* To break the loop */
876	}
877	}
878
879	if (referenced)
880	folio_clear_idle(folio);
881	if (folio_test_clear_young(folio))
882	referenced++;
883
884	if (referenced) {
885	pra->referenced++;
886	pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
887	}
888
889	if (!pra->mapcount)
890	return false; /* To break the loop */
891
892	return true;
893	}
894
895	static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
896	{
897	struct folio_referenced_arg *pra = arg;
898	struct mem_cgroup *memcg = pra->memcg;
899
900	/*
901	* Ignore references from this mapping if it has no recency. If the
902	* folio has been used in another mapping, we will catch it; if this
903	* other mapping is already gone, the unmap path will have set the
904	* referenced flag or activated the folio in zap_pte_range().
905	*/
906	if (!vma_has_recency(vma))
907	return true;
908
909	/*
910	* If we are reclaiming on behalf of a cgroup, skip counting on behalf
911	* of references from different cgroups.
912	*/
913	if (memcg && !mm_match_cgroup(mm: vma->vm_mm, memcg))
914	return true;
915
916	return false;
917	}
918
919	/**
920	* folio_referenced() - Test if the folio was referenced.
921	* @folio: The folio to test.
922	* @is_locked: Caller holds lock on the folio.
923	* @memcg: target memory cgroup
924	* @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
925	*
926	* Quick test_and_clear_referenced for all mappings of a folio,
927	*
928	* Return: The number of mappings which referenced the folio. Return -1 if
929	* the function bailed out due to rmap lock contention.
930	*/
931	int folio_referenced(struct folio *folio, int is_locked,
932	struct mem_cgroup *memcg, unsigned long *vm_flags)
933	{
934	int we_locked = 0;
935	struct folio_referenced_arg pra = {
936	.mapcount = folio_mapcount(folio),
937	.memcg = memcg,
938	};
939	struct rmap_walk_control rwc = {
940	.rmap_one = folio_referenced_one,
941	.arg = (void *)&pra,
942	.anon_lock = folio_lock_anon_vma_read,
943	.try_lock = true,
944	.invalid_vma = invalid_folio_referenced_vma,
945	};
946
947	*vm_flags = 0;
948	if (!pra.mapcount)
949	return 0;
950
951	if (!folio_raw_mapping(folio))
952	return 0;
953
954	if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
955	we_locked = folio_trylock(folio);
956	if (!we_locked)
957	return 1;
958	}
959
960	rmap_walk(folio, rwc: &rwc);
961	*vm_flags = pra.vm_flags;
962
963	if (we_locked)
964	folio_unlock(folio);
965
966	return rwc.contended ? -1 : pra.referenced;
967	}
968
969	static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
970	{
971	int cleaned = 0;
972	struct vm_area_struct *vma = pvmw->vma;
973	struct mmu_notifier_range range;
974	unsigned long address = pvmw->address;
975
976	/*
977	* We have to assume the worse case ie pmd for invalidation. Note that
978	* the folio can not be freed from this function.
979	*/
980	mmu_notifier_range_init(range: &range, event: MMU_NOTIFY_PROTECTION_PAGE, flags: 0,
981	mm: vma->vm_mm, start: address, end: vma_address_end(pvmw));
982	mmu_notifier_invalidate_range_start(range: &range);
983
984	while (page_vma_mapped_walk(pvmw)) {
985	int ret = 0;
986
987	address = pvmw->address;
988	if (pvmw->pte) {
989	pte_t *pte = pvmw->pte;
990	pte_t entry = ptep_get(ptep: pte);
991
992	if (!pte_dirty(pte: entry) && !pte_write(pte: entry))
993	continue;
994
995	flush_cache_page(vma, vmaddr: address, pfn: pte_pfn(pte: entry));
996	entry = ptep_clear_flush(vma, address, ptep: pte);
997	entry = pte_wrprotect(pte: entry);
998	entry = pte_mkclean(pte: entry);
999	set_pte_at(vma->vm_mm, address, pte, entry);
1000	ret = 1;
1001	} else {
1002	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1003	pmd_t *pmd = pvmw->pmd;
1004	pmd_t entry;
1005
1006	if (!pmd_dirty(pmd: *pmd) && !pmd_write(pmd: *pmd))
1007	continue;
1008
1009	flush_cache_range(vma, start: address,
1010	end: address + HPAGE_PMD_SIZE);
1011	entry = pmdp_invalidate(vma, address, pmdp: pmd);
1012	entry = pmd_wrprotect(pmd: entry);
1013	entry = pmd_mkclean(pmd: entry);
1014	set_pmd_at(mm: vma->vm_mm, addr: address, pmdp: pmd, pmd: entry);
1015	ret = 1;
1016	#else
1017	/* unexpected pmd-mapped folio? */
1018	WARN_ON_ONCE(1);
1019	#endif
1020	}
1021
1022	if (ret)
1023	cleaned++;
1024	}
1025
1026	mmu_notifier_invalidate_range_end(range: &range);
1027
1028	return cleaned;
1029	}
1030
1031	static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
1032	unsigned long address, void *arg)
1033	{
1034	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
1035	int *cleaned = arg;
1036
1037	*cleaned += page_vma_mkclean_one(pvmw: &pvmw);
1038
1039	return true;
1040	}
1041
1042	static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
1043	{
1044	if (vma->vm_flags & VM_SHARED)
1045	return false;
1046
1047	return true;
1048	}
1049
1050	int folio_mkclean(struct folio *folio)
1051	{
1052	int cleaned = 0;
1053	struct address_space *mapping;
1054	struct rmap_walk_control rwc = {
1055	.arg = (void *)&cleaned,
1056	.rmap_one = page_mkclean_one,
1057	.invalid_vma = invalid_mkclean_vma,
1058	};
1059
1060	BUG_ON(!folio_test_locked(folio));
1061
1062	if (!folio_mapped(folio))
1063	return 0;
1064
1065	mapping = folio_mapping(folio);
1066	if (!mapping)
1067	return 0;
1068
1069	rmap_walk(folio, rwc: &rwc);
1070
1071	return cleaned;
1072	}
1073	EXPORT_SYMBOL_GPL(folio_mkclean);
1074
1075	/**
1076	* pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
1077	* [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
1078	* within the @vma of shared mappings. And since clean PTEs
1079	* should also be readonly, write protects them too.
1080	* @pfn: start pfn.
1081	* @nr_pages: number of physically contiguous pages srarting with @pfn.
1082	* @pgoff: page offset that the @pfn mapped with.
1083	* @vma: vma that @pfn mapped within.
1084	*
1085	* Returns the number of cleaned PTEs (including PMDs).
1086	*/
1087	int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
1088	struct vm_area_struct *vma)
1089	{
1090	struct page_vma_mapped_walk pvmw = {
1091	.pfn = pfn,
1092	.nr_pages = nr_pages,
1093	.pgoff = pgoff,
1094	.vma = vma,
1095	.flags = PVMW_SYNC,
1096	};
1097
1098	if (invalid_mkclean_vma(vma, NULL))
1099	return 0;
1100
1101	pvmw.address = vma_pgoff_address(pgoff, nr_pages, vma);
1102	VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
1103
1104	return page_vma_mkclean_one(pvmw: &pvmw);
1105	}
1106
1107	int folio_total_mapcount(struct folio *folio)
1108	{
1109	int mapcount = folio_entire_mapcount(folio);
1110	int nr_pages;
1111	int i;
1112
1113	/* In the common case, avoid the loop when no pages mapped by PTE */
1114	if (folio_nr_pages_mapped(folio) == 0)
1115	return mapcount;
1116	/*
1117	* Add all the PTE mappings of those pages mapped by PTE.
1118	* Limit the loop to folio_nr_pages_mapped()?
1119	* Perhaps: given all the raciness, that may be a good or a bad idea.
1120	*/
1121	nr_pages = folio_nr_pages(folio);
1122	for (i = 0; i < nr_pages; i++)
1123	mapcount += atomic_read(v: &folio_page(folio, i)->_mapcount);
1124
1125	/* But each of those _mapcounts was based on -1 */
1126	mapcount += nr_pages;
1127	return mapcount;
1128	}
1129
1130	/**
1131	* folio_move_anon_rmap - move a folio to our anon_vma
1132	* @folio: The folio to move to our anon_vma
1133	* @vma: The vma the folio belongs to
1134	*
1135	* When a folio belongs exclusively to one process after a COW event,
1136	* that folio can be moved into the anon_vma that belongs to just that
1137	* process, so the rmap code will not search the parent or sibling processes.
1138	*/
1139	void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
1140	{
1141	void *anon_vma = vma->anon_vma;
1142
1143	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1144	VM_BUG_ON_VMA(!anon_vma, vma);
1145
1146	anon_vma += PAGE_MAPPING_ANON;
1147	/*
1148	* Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1149	* simultaneously, so a concurrent reader (eg folio_referenced()'s
1150	* folio_test_anon()) will not see one without the other.
1151	*/
1152	WRITE_ONCE(folio->mapping, anon_vma);
1153	}
1154
1155	/**
1156	* __folio_set_anon - set up a new anonymous rmap for a folio
1157	* @folio: The folio to set up the new anonymous rmap for.
1158	* @vma: VM area to add the folio to.
1159	* @address: User virtual address of the mapping
1160	* @exclusive: Whether the folio is exclusive to the process.
1161	*/
1162	static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
1163	unsigned long address, bool exclusive)
1164	{
1165	struct anon_vma *anon_vma = vma->anon_vma;
1166
1167	BUG_ON(!anon_vma);
1168
1169	/*
1170	* If the folio isn't exclusive to this vma, we must use the _oldest_
1171	* possible anon_vma for the folio mapping!
1172	*/
1173	if (!exclusive)
1174	anon_vma = anon_vma->root;
1175
1176	/*
1177	* page_idle does a lockless/optimistic rmap scan on folio->mapping.
1178	* Make sure the compiler doesn't split the stores of anon_vma and
1179	* the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
1180	* could mistake the mapping for a struct address_space and crash.
1181	*/
1182	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1183	WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
1184	folio->index = linear_page_index(vma, address);
1185	}
1186
1187	/**
1188	* __page_check_anon_rmap - sanity check anonymous rmap addition
1189	* @folio: The folio containing @page.
1190	* @page: the page to check the mapping of
1191	* @vma: the vm area in which the mapping is added
1192	* @address: the user virtual address mapped
1193	*/
1194	static void __page_check_anon_rmap(struct folio *folio, struct page *page,
1195	struct vm_area_struct *vma, unsigned long address)
1196	{
1197	/*
1198	* The page's anon-rmap details (mapping and index) are guaranteed to
1199	* be set up correctly at this point.
1200	*
1201	* We have exclusion against page_add_anon_rmap because the caller
1202	* always holds the page locked.
1203	*
1204	* We have exclusion against page_add_new_anon_rmap because those pages
1205	* are initially only visible via the pagetables, and the pte is locked
1206	* over the call to page_add_new_anon_rmap.
1207	*/
1208	VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
1209	folio);
1210	VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
1211	page);
1212	}
1213
1214	/**
1215	* page_add_anon_rmap - add pte mapping to an anonymous page
1216	* @page: the page to add the mapping to
1217	* @vma: the vm area in which the mapping is added
1218	* @address: the user virtual address mapped
1219	* @flags: the rmap flags
1220	*
1221	* The caller needs to hold the pte lock, and the page must be locked in
1222	* the anon_vma case: to serialize mapping,index checking after setting,
1223	* and to ensure that PageAnon is not being upgraded racily to PageKsm
1224	* (but PageKsm is never downgraded to PageAnon).
1225	*/
1226	void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
1227	unsigned long address, rmap_t flags)
1228	{
1229	struct folio *folio = page_folio(page);
1230	atomic_t *mapped = &folio->_nr_pages_mapped;
1231	int nr = 0, nr_pmdmapped = 0;
1232	bool compound = flags & RMAP_COMPOUND;
1233	bool first;
1234
1235	/* Is page being mapped by PTE? Is this its first map to be added? */
1236	if (likely(!compound)) {
1237	first = atomic_inc_and_test(v: &page->_mapcount);
1238	nr = first;
1239	if (first && folio_test_large(folio)) {
1240	nr = atomic_inc_return_relaxed(v: mapped);
1241	nr = (nr < COMPOUND_MAPPED);
1242	}
1243	} else if (folio_test_pmd_mappable(folio)) {
1244	/* That test is redundant: it's for safety or to optimize out */
1245
1246	first = atomic_inc_and_test(v: &folio->_entire_mapcount);
1247	if (first) {
1248	nr = atomic_add_return_relaxed(COMPOUND_MAPPED, v: mapped);
1249	if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
1250	nr_pmdmapped = folio_nr_pages(folio);
1251	nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1252	/* Raced ahead of a remove and another add? */
1253	if (unlikely(nr < 0))
1254	nr = 0;
1255	} else {
1256	/* Raced ahead of a remove of COMPOUND_MAPPED */
1257	nr = 0;
1258	}
1259	}
1260	}
1261
1262	if (nr_pmdmapped)
1263	__lruvec_stat_mod_folio(folio, idx: NR_ANON_THPS, val: nr_pmdmapped);
1264	if (nr)
1265	__lruvec_stat_mod_folio(folio, idx: NR_ANON_MAPPED, val: nr);
1266
1267	if (unlikely(!folio_test_anon(folio))) {
1268	VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
1269	/*
1270	* For a PTE-mapped large folio, we only know that the single
1271	* PTE is exclusive. Further, __folio_set_anon() might not get
1272	* folio->index right when not given the address of the head
1273	* page.
1274	*/
1275	VM_WARN_ON_FOLIO(folio_test_large(folio) && !compound, folio);
1276	__folio_set_anon(folio, vma, address,
1277	exclusive: !!(flags & RMAP_EXCLUSIVE));
1278	} else if (likely(!folio_test_ksm(folio))) {
1279	__page_check_anon_rmap(folio, page, vma, address);
1280	}
1281	if (flags & RMAP_EXCLUSIVE)
1282	SetPageAnonExclusive(page);
1283	/* While PTE-mapping a THP we have a PMD and a PTE mapping. */
1284	VM_WARN_ON_FOLIO((atomic_read(&page->_mapcount) > 0 ||
1285	(folio_test_large(folio) && folio_entire_mapcount(folio) > 1)) &&
1286	PageAnonExclusive(page), folio);
1287
1288	/*
1289	* For large folio, only mlock it if it's fully mapped to VMA. It's
1290	* not easy to check whether the large folio is fully mapped to VMA
1291	* here. Only mlock normal 4K folio and leave page reclaim to handle
1292	* large folio.
1293	*/
1294	if (!folio_test_large(folio))
1295	mlock_vma_folio(folio, vma);
1296	}
1297
1298	/**
1299	* folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
1300	* @folio: The folio to add the mapping to.
1301	* @vma: the vm area in which the mapping is added
1302	* @address: the user virtual address mapped
1303	*
1304	* Like page_add_anon_rmap() but must only be called on *new* folios.
1305	* This means the inc-and-test can be bypassed.
1306	* The folio does not have to be locked.
1307	*
1308	* If the folio is large, it is accounted as a THP. As the folio
1309	* is new, it's assumed to be mapped exclusively by a single process.
1310	*/
1311	void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
1312	unsigned long address)
1313	{
1314	int nr;
1315
1316	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1317	__folio_set_swapbacked(folio);
1318
1319	if (likely(!folio_test_pmd_mappable(folio))) {
1320	/* increment count (starts at -1) */
1321	atomic_set(v: &folio->_mapcount, i: 0);
1322	nr = 1;
1323	} else {
1324	/* increment count (starts at -1) */
1325	atomic_set(v: &folio->_entire_mapcount, i: 0);
1326	atomic_set(v: &folio->_nr_pages_mapped, COMPOUND_MAPPED);
1327	nr = folio_nr_pages(folio);
1328	__lruvec_stat_mod_folio(folio, idx: NR_ANON_THPS, val: nr);
1329	}
1330
1331	__lruvec_stat_mod_folio(folio, idx: NR_ANON_MAPPED, val: nr);
1332	__folio_set_anon(folio, vma, address, exclusive: true);
1333	SetPageAnonExclusive(&folio->page);
1334	}
1335
1336	/**
1337	* folio_add_file_rmap_range - add pte mapping to page range of a folio
1338	* @folio: The folio to add the mapping to
1339	* @page: The first page to add
1340	* @nr_pages: The number of pages which will be mapped
1341	* @vma: the vm area in which the mapping is added
1342	* @compound: charge the page as compound or small page
1343	*
1344	* The page range of folio is defined by [first_page, first_page + nr_pages)
1345	*
1346	* The caller needs to hold the pte lock.
1347	*/
1348	void folio_add_file_rmap_range(struct folio *folio, struct page *page,
1349	unsigned int nr_pages, struct vm_area_struct *vma,
1350	bool compound)
1351	{
1352	atomic_t *mapped = &folio->_nr_pages_mapped;
1353	unsigned int nr_pmdmapped = 0, first;
1354	int nr = 0;
1355
1356	VM_WARN_ON_FOLIO(compound && !folio_test_pmd_mappable(folio), folio);
1357
1358	/* Is page being mapped by PTE? Is this its first map to be added? */
1359	if (likely(!compound)) {
1360	do {
1361	first = atomic_inc_and_test(v: &page->_mapcount);
1362	if (first && folio_test_large(folio)) {
1363	first = atomic_inc_return_relaxed(v: mapped);
1364	first = (first < COMPOUND_MAPPED);
1365	}
1366
1367	if (first)
1368	nr++;
1369	} while (page++, --nr_pages > 0);
1370	} else if (folio_test_pmd_mappable(folio)) {
1371	/* That test is redundant: it's for safety or to optimize out */
1372
1373	first = atomic_inc_and_test(v: &folio->_entire_mapcount);
1374	if (first) {
1375	nr = atomic_add_return_relaxed(COMPOUND_MAPPED, v: mapped);
1376	if (likely(nr < COMPOUND_MAPPED + COMPOUND_MAPPED)) {
1377	nr_pmdmapped = folio_nr_pages(folio);
1378	nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1379	/* Raced ahead of a remove and another add? */
1380	if (unlikely(nr < 0))
1381	nr = 0;
1382	} else {
1383	/* Raced ahead of a remove of COMPOUND_MAPPED */
1384	nr = 0;
1385	}
1386	}
1387	}
1388
1389	if (nr_pmdmapped)
1390	__lruvec_stat_mod_folio(folio, idx: folio_test_swapbacked(folio) ?
1391	NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, val: nr_pmdmapped);
1392	if (nr)
1393	__lruvec_stat_mod_folio(folio, idx: NR_FILE_MAPPED, val: nr);
1394
1395	/* See comments in page_add_anon_rmap() */
1396	if (!folio_test_large(folio))
1397	mlock_vma_folio(folio, vma);
1398	}
1399
1400	/**
1401	* page_add_file_rmap - add pte mapping to a file page
1402	* @page: the page to add the mapping to
1403	* @vma: the vm area in which the mapping is added
1404	* @compound: charge the page as compound or small page
1405	*
1406	* The caller needs to hold the pte lock.
1407	*/
1408	void page_add_file_rmap(struct page *page, struct vm_area_struct *vma,
1409	bool compound)
1410	{
1411	struct folio *folio = page_folio(page);
1412	unsigned int nr_pages;
1413
1414	VM_WARN_ON_ONCE_PAGE(compound && !PageTransHuge(page), page);
1415
1416	if (likely(!compound))
1417	nr_pages = 1;
1418	else
1419	nr_pages = folio_nr_pages(folio);
1420
1421	folio_add_file_rmap_range(folio, page, nr_pages, vma, compound);
1422	}
1423
1424	/**
1425	* page_remove_rmap - take down pte mapping from a page
1426	* @page: page to remove mapping from
1427	* @vma: the vm area from which the mapping is removed
1428	* @compound: uncharge the page as compound or small page
1429	*
1430	* The caller needs to hold the pte lock.
1431	*/
1432	void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
1433	bool compound)
1434	{
1435	struct folio *folio = page_folio(page);
1436	atomic_t *mapped = &folio->_nr_pages_mapped;
1437	int nr = 0, nr_pmdmapped = 0;
1438	bool last;
1439	enum node_stat_item idx;
1440
1441	VM_BUG_ON_PAGE(compound && !PageHead(page), page);
1442
1443	/* Hugetlb pages are not counted in NR_*MAPPED */
1444	if (unlikely(folio_test_hugetlb(folio))) {
1445	/* hugetlb pages are always mapped with pmds */
1446	atomic_dec(v: &folio->_entire_mapcount);
1447	return;
1448	}
1449
1450	/* Is page being unmapped by PTE? Is this its last map to be removed? */
1451	if (likely(!compound)) {
1452	last = atomic_add_negative(i: -1, v: &page->_mapcount);
1453	nr = last;
1454	if (last && folio_test_large(folio)) {
1455	nr = atomic_dec_return_relaxed(v: mapped);
1456	nr = (nr < COMPOUND_MAPPED);
1457	}
1458	} else if (folio_test_pmd_mappable(folio)) {
1459	/* That test is redundant: it's for safety or to optimize out */
1460
1461	last = atomic_add_negative(i: -1, v: &folio->_entire_mapcount);
1462	if (last) {
1463	nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, v: mapped);
1464	if (likely(nr < COMPOUND_MAPPED)) {
1465	nr_pmdmapped = folio_nr_pages(folio);
1466	nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1467	/* Raced ahead of another remove and an add? */
1468	if (unlikely(nr < 0))
1469	nr = 0;
1470	} else {
1471	/* An add of COMPOUND_MAPPED raced ahead */
1472	nr = 0;
1473	}
1474	}
1475	}
1476
1477	if (nr_pmdmapped) {
1478	if (folio_test_anon(folio))
1479	idx = NR_ANON_THPS;
1480	else if (folio_test_swapbacked(folio))
1481	idx = NR_SHMEM_PMDMAPPED;
1482	else
1483	idx = NR_FILE_PMDMAPPED;
1484	__lruvec_stat_mod_folio(folio, idx, val: -nr_pmdmapped);
1485	}
1486	if (nr) {
1487	idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
1488	__lruvec_stat_mod_folio(folio, idx, val: -nr);
1489
1490	/*
1491	* Queue anon THP for deferred split if at least one
1492	* page of the folio is unmapped and at least one page
1493	* is still mapped.
1494	*/
1495	if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))
1496	if (!compound || nr < nr_pmdmapped)
1497	deferred_split_folio(folio);
1498	}
1499
1500	/*
1501	* It would be tidy to reset folio_test_anon mapping when fully
1502	* unmapped, but that might overwrite a racing page_add_anon_rmap
1503	* which increments mapcount after us but sets mapping before us:
1504	* so leave the reset to free_pages_prepare, and remember that
1505	* it's only reliable while mapped.
1506	*/
1507
1508	munlock_vma_folio(folio, vma);
1509	}
1510
1511	/*
1512	* @arg: enum ttu_flags will be passed to this argument
1513	*/
1514	static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
1515	unsigned long address, void *arg)
1516	{
1517	struct mm_struct *mm = vma->vm_mm;
1518	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1519	pte_t pteval;
1520	struct page *subpage;
1521	bool anon_exclusive, ret = true;
1522	struct mmu_notifier_range range;
1523	enum ttu_flags flags = (enum ttu_flags)(long)arg;
1524	unsigned long pfn;
1525	unsigned long hsz = 0;
1526
1527	/*
1528	* When racing against e.g. zap_pte_range() on another cpu,
1529	* in between its ptep_get_and_clear_full() and page_remove_rmap(),
1530	* try_to_unmap() may return before page_mapped() has become false,
1531	* if page table locking is skipped: use TTU_SYNC to wait for that.
1532	*/
1533	if (flags & TTU_SYNC)
1534	pvmw.flags = PVMW_SYNC;
1535
1536	if (flags & TTU_SPLIT_HUGE_PMD)
1537	split_huge_pmd_address(vma, address, freeze: false, folio);
1538
1539	/*
1540	* For THP, we have to assume the worse case ie pmd for invalidation.
1541	* For hugetlb, it could be much worse if we need to do pud
1542	* invalidation in the case of pmd sharing.
1543	*
1544	* Note that the folio can not be freed in this function as call of
1545	* try_to_unmap() must hold a reference on the folio.
1546	*/
1547	range.end = vma_address_end(pvmw: &pvmw);
1548	mmu_notifier_range_init(range: &range, event: MMU_NOTIFY_CLEAR, flags: 0, mm: vma->vm_mm,
1549	start: address, end: range.end);
1550	if (folio_test_hugetlb(folio)) {
1551	/*
1552	* If sharing is possible, start and end will be adjusted
1553	* accordingly.
1554	*/
1555	adjust_range_if_pmd_sharing_possible(vma, start: &range.start,
1556	end: &range.end);
1557
1558	/* We need the huge page size for set_huge_pte_at() */
1559	hsz = huge_page_size(h: hstate_vma(vma));
1560	}
1561	mmu_notifier_invalidate_range_start(range: &range);
1562
1563	while (page_vma_mapped_walk(pvmw: &pvmw)) {
1564	/* Unexpected PMD-mapped THP? */
1565	VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1566
1567	/*
1568	* If the folio is in an mlock()d vma, we must not swap it out.
1569	*/
1570	if (!(flags & TTU_IGNORE_MLOCK) &&
1571	(vma->vm_flags & VM_LOCKED)) {
1572	/* Restore the mlock which got missed */
1573	if (!folio_test_large(folio))
1574	mlock_vma_folio(folio, vma);
1575	page_vma_mapped_walk_done(pvmw: &pvmw);
1576	ret = false;
1577	break;
1578	}
1579
1580	pfn = pte_pfn(pte: ptep_get(ptep: pvmw.pte));
1581	subpage = folio_page(folio, pfn - folio_pfn(folio));
1582	address = pvmw.address;
1583	anon_exclusive = folio_test_anon(folio) &&
1584	PageAnonExclusive(page: subpage);
1585
1586	if (folio_test_hugetlb(folio)) {
1587	bool anon = folio_test_anon(folio);
1588
1589	/*
1590	* The try_to_unmap() is only passed a hugetlb page
1591	* in the case where the hugetlb page is poisoned.
1592	*/
1593	VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
1594	/*
1595	* huge_pmd_unshare may unmap an entire PMD page.
1596	* There is no way of knowing exactly which PMDs may
1597	* be cached for this mm, so we must flush them all.
1598	* start/end were already adjusted above to cover this
1599	* range.
1600	*/
1601	flush_cache_range(vma, start: range.start, end: range.end);
1602
1603	/*
1604	* To call huge_pmd_unshare, i_mmap_rwsem must be
1605	* held in write mode. Caller needs to explicitly
1606	* do this outside rmap routines.
1607	*
1608	* We also must hold hugetlb vma_lock in write mode.
1609	* Lock order dictates acquiring vma_lock BEFORE
1610	* i_mmap_rwsem. We can only try lock here and fail
1611	* if unsuccessful.
1612	*/
1613	if (!anon) {
1614	VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1615	if (!hugetlb_vma_trylock_write(vma)) {
1616	page_vma_mapped_walk_done(pvmw: &pvmw);
1617	ret = false;
1618	break;
1619	}
1620	if (huge_pmd_unshare(mm, vma, addr: address, ptep: pvmw.pte)) {
1621	hugetlb_vma_unlock_write(vma);
1622	flush_tlb_range(vma,
1623	range.start, range.end);
1624	/*
1625	* The ref count of the PMD page was
1626	* dropped which is part of the way map
1627	* counting is done for shared PMDs.
1628	* Return 'true' here. When there is
1629	* no other sharing, huge_pmd_unshare
1630	* returns false and we will unmap the
1631	* actual page and drop map count
1632	* to zero.
1633	*/
1634	page_vma_mapped_walk_done(pvmw: &pvmw);
1635	break;
1636	}
1637	hugetlb_vma_unlock_write(vma);
1638	}
1639	pteval = huge_ptep_clear_flush(vma, addr: address, ptep: pvmw.pte);
1640	} else {
1641	flush_cache_page(vma, vmaddr: address, pfn);
1642	/* Nuke the page table entry. */
1643	if (should_defer_flush(mm, flags)) {
1644	/*
1645	* We clear the PTE but do not flush so potentially
1646	* a remote CPU could still be writing to the folio.
1647	* If the entry was previously clean then the
1648	* architecture must guarantee that a clear->dirty
1649	* transition on a cached TLB entry is written through
1650	* and traps if the PTE is unmapped.
1651	*/
1652	pteval = ptep_get_and_clear(mm, addr: address, ptep: pvmw.pte);
1653
1654	set_tlb_ubc_flush_pending(mm, pteval, uaddr: address);
1655	} else {
1656	pteval = ptep_clear_flush(vma, address, ptep: pvmw.pte);
1657	}
1658	}
1659
1660	/*
1661	* Now the pte is cleared. If this pte was uffd-wp armed,
1662	* we may want to replace a none pte with a marker pte if
1663	* it's file-backed, so we don't lose the tracking info.
1664	*/
1665	pte_install_uffd_wp_if_needed(vma, addr: address, pte: pvmw.pte, pteval);
1666
1667	/* Set the dirty flag on the folio now the pte is gone. */
1668	if (pte_dirty(pte: pteval))
1669	folio_mark_dirty(folio);
1670
1671	/* Update high watermark before we lower rss */
1672	update_hiwater_rss(mm);
1673
1674	if (PageHWPoison(page: subpage) && (flags & TTU_HWPOISON)) {
1675	pteval = swp_entry_to_pte(entry: make_hwpoison_entry(page: subpage));
1676	if (folio_test_hugetlb(folio)) {
1677	hugetlb_count_sub(l: folio_nr_pages(folio), mm);
1678	set_huge_pte_at(mm, addr: address, ptep: pvmw.pte, pte: pteval,
1679	sz: hsz);
1680	} else {
1681	dec_mm_counter(mm, member: mm_counter(page: &folio->page));
1682	set_pte_at(mm, address, pvmw.pte, pteval);
1683	}
1684
1685	} else if (pte_unused(pte: pteval) && !userfaultfd_armed(vma)) {
1686	/*
1687	* The guest indicated that the page content is of no
1688	* interest anymore. Simply discard the pte, vmscan
1689	* will take care of the rest.
1690	* A future reference will then fault in a new zero
1691	* page. When userfaultfd is active, we must not drop
1692	* this page though, as its main user (postcopy
1693	* migration) will not expect userfaults on already
1694	* copied pages.
1695	*/
1696	dec_mm_counter(mm, member: mm_counter(page: &folio->page));
1697	} else if (folio_test_anon(folio)) {
1698	swp_entry_t entry = page_swap_entry(page: subpage);
1699	pte_t swp_pte;
1700	/*
1701	* Store the swap location in the pte.
1702	* See handle_pte_fault() ...
1703	*/
1704	if (unlikely(folio_test_swapbacked(folio) !=
1705	folio_test_swapcache(folio))) {
1706	WARN_ON_ONCE(1);
1707	ret = false;
1708	page_vma_mapped_walk_done(pvmw: &pvmw);
1709	break;
1710	}
1711
1712	/* MADV_FREE page check */
1713	if (!folio_test_swapbacked(folio)) {
1714	int ref_count, map_count;
1715
1716	/*
1717	* Synchronize with gup_pte_range():
1718	* - clear PTE; barrier; read refcount
1719	* - inc refcount; barrier; read PTE
1720	*/
1721	smp_mb();
1722
1723	ref_count = folio_ref_count(folio);
1724	map_count = folio_mapcount(folio);
1725
1726	/*
1727	* Order reads for page refcount and dirty flag
1728	* (see comments in __remove_mapping()).
1729	*/
1730	smp_rmb();
1731
1732	/*
1733	* The only page refs must be one from isolation
1734	* plus the rmap(s) (dropped by discard:).
1735	*/
1736	if (ref_count == 1 + map_count &&
1737	!folio_test_dirty(folio)) {
1738	dec_mm_counter(mm, member: MM_ANONPAGES);
1739	goto discard;
1740	}
1741
1742	/*
1743	* If the folio was redirtied, it cannot be
1744	* discarded. Remap the page to page table.
1745	*/
1746	set_pte_at(mm, address, pvmw.pte, pteval);
1747	folio_set_swapbacked(folio);
1748	ret = false;
1749	page_vma_mapped_walk_done(pvmw: &pvmw);
1750	break;
1751	}
1752
1753	if (swap_duplicate(entry) < 0) {
1754	set_pte_at(mm, address, pvmw.pte, pteval);
1755	ret = false;
1756	page_vma_mapped_walk_done(pvmw: &pvmw);
1757	break;
1758	}
1759	if (arch_unmap_one(mm, vma, addr: address, orig_pte: pteval) < 0) {
1760	swap_free(entry);
1761	set_pte_at(mm, address, pvmw.pte, pteval);
1762	ret = false;
1763	page_vma_mapped_walk_done(pvmw: &pvmw);
1764	break;
1765	}
1766
1767	/* See page_try_share_anon_rmap(): clear PTE first. */
1768	if (anon_exclusive &&
1769	page_try_share_anon_rmap(page: subpage)) {
1770	swap_free(entry);
1771	set_pte_at(mm, address, pvmw.pte, pteval);
1772	ret = false;
1773	page_vma_mapped_walk_done(pvmw: &pvmw);
1774	break;
1775	}
1776	if (list_empty(head: &mm->mmlist)) {
1777	spin_lock(lock: &mmlist_lock);
1778	if (list_empty(head: &mm->mmlist))
1779	list_add(new: &mm->mmlist, head: &init_mm.mmlist);
1780	spin_unlock(lock: &mmlist_lock);
1781	}
1782	dec_mm_counter(mm, member: MM_ANONPAGES);
1783	inc_mm_counter(mm, member: MM_SWAPENTS);
1784	swp_pte = swp_entry_to_pte(entry);
1785	if (anon_exclusive)
1786	swp_pte = pte_swp_mkexclusive(pte: swp_pte);
1787	if (pte_soft_dirty(pte: pteval))
1788	swp_pte = pte_swp_mksoft_dirty(pte: swp_pte);
1789	if (pte_uffd_wp(pte: pteval))
1790	swp_pte = pte_swp_mkuffd_wp(pte: swp_pte);
1791	set_pte_at(mm, address, pvmw.pte, swp_pte);
1792	} else {
1793	/*
1794	* This is a locked file-backed folio,
1795	* so it cannot be removed from the page
1796	* cache and replaced by a new folio before
1797	* mmu_notifier_invalidate_range_end, so no
1798	* concurrent thread might update its page table
1799	* to point at a new folio while a device is
1800	* still using this folio.
1801	*
1802	* See Documentation/mm/mmu_notifier.rst
1803	*/
1804	dec_mm_counter(mm, member: mm_counter_file(page: &folio->page));
1805	}
1806	discard:
1807	page_remove_rmap(page: subpage, vma, compound: folio_test_hugetlb(folio));
1808	if (vma->vm_flags & VM_LOCKED)
1809	mlock_drain_local();
1810	folio_put(folio);
1811	}
1812
1813	mmu_notifier_invalidate_range_end(range: &range);
1814
1815	return ret;
1816	}
1817
1818	static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1819	{
1820	return vma_is_temporary_stack(vma);
1821	}
1822
1823	static int folio_not_mapped(struct folio *folio)
1824	{
1825	return !folio_mapped(folio);
1826	}
1827
1828	/**
1829	* try_to_unmap - Try to remove all page table mappings to a folio.
1830	* @folio: The folio to unmap.
1831	* @flags: action and flags
1832	*
1833	* Tries to remove all the page table entries which are mapping this
1834	* folio. It is the caller's responsibility to check if the folio is
1835	* still mapped if needed (use TTU_SYNC to prevent accounting races).
1836	*
1837	* Context: Caller must hold the folio lock.
1838	*/
1839	void try_to_unmap(struct folio *folio, enum ttu_flags flags)
1840	{
1841	struct rmap_walk_control rwc = {
1842	.rmap_one = try_to_unmap_one,
1843	.arg = (void *)flags,
1844	.done = folio_not_mapped,
1845	.anon_lock = folio_lock_anon_vma_read,
1846	};
1847
1848	if (flags & TTU_RMAP_LOCKED)
1849	rmap_walk_locked(folio, rwc: &rwc);
1850	else
1851	rmap_walk(folio, rwc: &rwc);
1852	}
1853
1854	/*
1855	* @arg: enum ttu_flags will be passed to this argument.
1856	*
1857	* If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
1858	* containing migration entries.
1859	*/
1860	static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
1861	unsigned long address, void *arg)
1862	{
1863	struct mm_struct *mm = vma->vm_mm;
1864	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1865	pte_t pteval;
1866	struct page *subpage;
1867	bool anon_exclusive, ret = true;
1868	struct mmu_notifier_range range;
1869	enum ttu_flags flags = (enum ttu_flags)(long)arg;
1870	unsigned long pfn;
1871	unsigned long hsz = 0;
1872
1873	/*
1874	* When racing against e.g. zap_pte_range() on another cpu,
1875	* in between its ptep_get_and_clear_full() and page_remove_rmap(),
1876	* try_to_migrate() may return before page_mapped() has become false,
1877	* if page table locking is skipped: use TTU_SYNC to wait for that.
1878	*/
1879	if (flags & TTU_SYNC)
1880	pvmw.flags = PVMW_SYNC;
1881
1882	/*
1883	* unmap_page() in mm/huge_memory.c is the only user of migration with
1884	* TTU_SPLIT_HUGE_PMD and it wants to freeze.
1885	*/
1886	if (flags & TTU_SPLIT_HUGE_PMD)
1887	split_huge_pmd_address(vma, address, freeze: true, folio);
1888
1889	/*
1890	* For THP, we have to assume the worse case ie pmd for invalidation.
1891	* For hugetlb, it could be much worse if we need to do pud
1892	* invalidation in the case of pmd sharing.
1893	*
1894	* Note that the page can not be free in this function as call of
1895	* try_to_unmap() must hold a reference on the page.
1896	*/
1897	range.end = vma_address_end(pvmw: &pvmw);
1898	mmu_notifier_range_init(range: &range, event: MMU_NOTIFY_CLEAR, flags: 0, mm: vma->vm_mm,
1899	start: address, end: range.end);
1900	if (folio_test_hugetlb(folio)) {
1901	/*
1902	* If sharing is possible, start and end will be adjusted
1903	* accordingly.
1904	*/
1905	adjust_range_if_pmd_sharing_possible(vma, start: &range.start,
1906	end: &range.end);
1907
1908	/* We need the huge page size for set_huge_pte_at() */
1909	hsz = huge_page_size(h: hstate_vma(vma));
1910	}
1911	mmu_notifier_invalidate_range_start(range: &range);
1912
1913	while (page_vma_mapped_walk(pvmw: &pvmw)) {
1914	#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1915	/* PMD-mapped THP migration entry */
1916	if (!pvmw.pte) {
1917	subpage = folio_page(folio,
1918	pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
1919	VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
1920	!folio_test_pmd_mappable(folio), folio);
1921
1922	if (set_pmd_migration_entry(pvmw: &pvmw, page: subpage)) {
1923	ret = false;
1924	page_vma_mapped_walk_done(pvmw: &pvmw);
1925	break;
1926	}
1927	continue;
1928	}
1929	#endif
1930
1931	/* Unexpected PMD-mapped THP? */
1932	VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1933
1934	pfn = pte_pfn(pte: ptep_get(ptep: pvmw.pte));
1935
1936	if (folio_is_zone_device(folio)) {
1937	/*
1938	* Our PTE is a non-present device exclusive entry and
1939	* calculating the subpage as for the common case would
1940	* result in an invalid pointer.
1941	*
1942	* Since only PAGE_SIZE pages can currently be
1943	* migrated, just set it to page. This will need to be
1944	* changed when hugepage migrations to device private
1945	* memory are supported.
1946	*/
1947	VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
1948	subpage = &folio->page;
1949	} else {
1950	subpage = folio_page(folio, pfn - folio_pfn(folio));
1951	}
1952	address = pvmw.address;
1953	anon_exclusive = folio_test_anon(folio) &&
1954	PageAnonExclusive(page: subpage);
1955
1956	if (folio_test_hugetlb(folio)) {
1957	bool anon = folio_test_anon(folio);
1958
1959	/*
1960	* huge_pmd_unshare may unmap an entire PMD page.
1961	* There is no way of knowing exactly which PMDs may
1962	* be cached for this mm, so we must flush them all.
1963	* start/end were already adjusted above to cover this
1964	* range.
1965	*/
1966	flush_cache_range(vma, start: range.start, end: range.end);
1967
1968	/*
1969	* To call huge_pmd_unshare, i_mmap_rwsem must be
1970	* held in write mode. Caller needs to explicitly
1971	* do this outside rmap routines.
1972	*
1973	* We also must hold hugetlb vma_lock in write mode.
1974	* Lock order dictates acquiring vma_lock BEFORE
1975	* i_mmap_rwsem. We can only try lock here and
1976	* fail if unsuccessful.
1977	*/
1978	if (!anon) {
1979	VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1980	if (!hugetlb_vma_trylock_write(vma)) {
1981	page_vma_mapped_walk_done(pvmw: &pvmw);
1982	ret = false;
1983	break;
1984	}
1985	if (huge_pmd_unshare(mm, vma, addr: address, ptep: pvmw.pte)) {
1986	hugetlb_vma_unlock_write(vma);
1987	flush_tlb_range(vma,
1988	range.start, range.end);
1989
1990	/*
1991	* The ref count of the PMD page was
1992	* dropped which is part of the way map
1993	* counting is done for shared PMDs.
1994	* Return 'true' here. When there is
1995	* no other sharing, huge_pmd_unshare
1996	* returns false and we will unmap the
1997	* actual page and drop map count
1998	* to zero.
1999	*/
2000	page_vma_mapped_walk_done(pvmw: &pvmw);
2001	break;
2002	}
2003	hugetlb_vma_unlock_write(vma);
2004	}
2005	/* Nuke the hugetlb page table entry */
2006	pteval = huge_ptep_clear_flush(vma, addr: address, ptep: pvmw.pte);
2007	} else {
2008	flush_cache_page(vma, vmaddr: address, pfn);
2009	/* Nuke the page table entry. */
2010	if (should_defer_flush(mm, flags)) {
2011	/*
2012	* We clear the PTE but do not flush so potentially
2013	* a remote CPU could still be writing to the folio.
2014	* If the entry was previously clean then the
2015	* architecture must guarantee that a clear->dirty
2016	* transition on a cached TLB entry is written through
2017	* and traps if the PTE is unmapped.
2018	*/
2019	pteval = ptep_get_and_clear(mm, addr: address, ptep: pvmw.pte);
2020
2021	set_tlb_ubc_flush_pending(mm, pteval, uaddr: address);
2022	} else {
2023	pteval = ptep_clear_flush(vma, address, ptep: pvmw.pte);
2024	}
2025	}
2026
2027	/* Set the dirty flag on the folio now the pte is gone. */
2028	if (pte_dirty(pte: pteval))
2029	folio_mark_dirty(folio);
2030
2031	/* Update high watermark before we lower rss */
2032	update_hiwater_rss(mm);
2033
2034	if (folio_is_device_private(folio)) {
2035	unsigned long pfn = folio_pfn(folio);
2036	swp_entry_t entry;
2037	pte_t swp_pte;
2038
2039	if (anon_exclusive)
2040	BUG_ON(page_try_share_anon_rmap(subpage));
2041
2042	/*
2043	* Store the pfn of the page in a special migration
2044	* pte. do_swap_page() will wait until the migration
2045	* pte is removed and then restart fault handling.
2046	*/
2047	entry = pte_to_swp_entry(pte: pteval);
2048	if (is_writable_device_private_entry(entry))
2049	entry = make_writable_migration_entry(offset: pfn);
2050	else if (anon_exclusive)
2051	entry = make_readable_exclusive_migration_entry(offset: pfn);
2052	else
2053	entry = make_readable_migration_entry(offset: pfn);
2054	swp_pte = swp_entry_to_pte(entry);
2055
2056	/*
2057	* pteval maps a zone device page and is therefore
2058	* a swap pte.
2059	*/
2060	if (pte_swp_soft_dirty(pte: pteval))
2061	swp_pte = pte_swp_mksoft_dirty(pte: swp_pte);
2062	if (pte_swp_uffd_wp(pte: pteval))
2063	swp_pte = pte_swp_mkuffd_wp(pte: swp_pte);
2064	set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
2065	trace_set_migration_pte(addr: pvmw.address, pte: pte_val(pte: swp_pte),
2066	order: compound_order(page: &folio->page));
2067	/*
2068	* No need to invalidate here it will synchronize on
2069	* against the special swap migration pte.
2070	*/
2071	} else if (PageHWPoison(page: subpage)) {
2072	pteval = swp_entry_to_pte(entry: make_hwpoison_entry(page: subpage));
2073	if (folio_test_hugetlb(folio)) {
2074	hugetlb_count_sub(l: folio_nr_pages(folio), mm);
2075	set_huge_pte_at(mm, addr: address, ptep: pvmw.pte, pte: pteval,
2076	sz: hsz);
2077	} else {
2078	dec_mm_counter(mm, member: mm_counter(page: &folio->page));
2079	set_pte_at(mm, address, pvmw.pte, pteval);
2080	}
2081
2082	} else if (pte_unused(pte: pteval) && !userfaultfd_armed(vma)) {
2083	/*
2084	* The guest indicated that the page content is of no
2085	* interest anymore. Simply discard the pte, vmscan
2086	* will take care of the rest.
2087	* A future reference will then fault in a new zero
2088	* page. When userfaultfd is active, we must not drop
2089	* this page though, as its main user (postcopy
2090	* migration) will not expect userfaults on already
2091	* copied pages.
2092	*/
2093	dec_mm_counter(mm, member: mm_counter(page: &folio->page));
2094	} else {
2095	swp_entry_t entry;
2096	pte_t swp_pte;
2097
2098	if (arch_unmap_one(mm, vma, addr: address, orig_pte: pteval) < 0) {
2099	if (folio_test_hugetlb(folio))
2100	set_huge_pte_at(mm, addr: address, ptep: pvmw.pte,
2101	pte: pteval, sz: hsz);
2102	else
2103	set_pte_at(mm, address, pvmw.pte, pteval);
2104	ret = false;
2105	page_vma_mapped_walk_done(pvmw: &pvmw);
2106	break;
2107	}
2108	VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
2109	!anon_exclusive, subpage);
2110
2111	/* See page_try_share_anon_rmap(): clear PTE first. */
2112	if (anon_exclusive &&
2113	page_try_share_anon_rmap(page: subpage)) {
2114	if (folio_test_hugetlb(folio))
2115	set_huge_pte_at(mm, addr: address, ptep: pvmw.pte,
2116	pte: pteval, sz: hsz);
2117	else
2118	set_pte_at(mm, address, pvmw.pte, pteval);
2119	ret = false;
2120	page_vma_mapped_walk_done(pvmw: &pvmw);
2121	break;
2122	}
2123
2124	/*
2125	* Store the pfn of the page in a special migration
2126	* pte. do_swap_page() will wait until the migration
2127	* pte is removed and then restart fault handling.
2128	*/
2129	if (pte_write(pte: pteval))
2130	entry = make_writable_migration_entry(
2131	page_to_pfn(subpage));
2132	else if (anon_exclusive)
2133	entry = make_readable_exclusive_migration_entry(
2134	page_to_pfn(subpage));
2135	else
2136	entry = make_readable_migration_entry(
2137	page_to_pfn(subpage));
2138	if (pte_young(pte: pteval))
2139	entry = make_migration_entry_young(entry);
2140	if (pte_dirty(pte: pteval))
2141	entry = make_migration_entry_dirty(entry);
2142	swp_pte = swp_entry_to_pte(entry);
2143	if (pte_soft_dirty(pte: pteval))
2144	swp_pte = pte_swp_mksoft_dirty(pte: swp_pte);
2145	if (pte_uffd_wp(pte: pteval))
2146	swp_pte = pte_swp_mkuffd_wp(pte: swp_pte);
2147	if (folio_test_hugetlb(folio))
2148	set_huge_pte_at(mm, addr: address, ptep: pvmw.pte, pte: swp_pte,
2149	sz: hsz);
2150	else
2151	set_pte_at(mm, address, pvmw.pte, swp_pte);
2152	trace_set_migration_pte(addr: address, pte: pte_val(pte: swp_pte),
2153	order: compound_order(page: &folio->page));
2154	/*
2155	* No need to invalidate here it will synchronize on
2156	* against the special swap migration pte.
2157	*/
2158	}
2159
2160	page_remove_rmap(page: subpage, vma, compound: folio_test_hugetlb(folio));
2161	if (vma->vm_flags & VM_LOCKED)
2162	mlock_drain_local();
2163	folio_put(folio);
2164	}
2165
2166	mmu_notifier_invalidate_range_end(range: &range);
2167
2168	return ret;
2169	}
2170
2171	/**
2172	* try_to_migrate - try to replace all page table mappings with swap entries
2173	* @folio: the folio to replace page table entries for
2174	* @flags: action and flags
2175	*
2176	* Tries to remove all the page table entries which are mapping this folio and
2177	* replace them with special swap entries. Caller must hold the folio lock.
2178	*/
2179	void try_to_migrate(struct folio *folio, enum ttu_flags flags)
2180	{
2181	struct rmap_walk_control rwc = {
2182	.rmap_one = try_to_migrate_one,
2183	.arg = (void *)flags,
2184	.done = folio_not_mapped,
2185	.anon_lock = folio_lock_anon_vma_read,
2186	};
2187
2188	/*
2189	* Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
2190	* TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
2191	*/
2192	if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2193	TTU_SYNC | TTU_BATCH_FLUSH)))
2194	return;
2195
2196	if (folio_is_zone_device(folio) &&
2197	(!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
2198	return;
2199
2200	/*
2201	* During exec, a temporary VMA is setup and later moved.
2202	* The VMA is moved under the anon_vma lock but not the
2203	* page tables leading to a race where migration cannot
2204	* find the migration ptes. Rather than increasing the
2205	* locking requirements of exec(), migration skips
2206	* temporary VMAs until after exec() completes.
2207	*/
2208	if (!folio_test_ksm(folio) && folio_test_anon(folio))
2209	rwc.invalid_vma = invalid_migration_vma;
2210
2211	if (flags & TTU_RMAP_LOCKED)
2212	rmap_walk_locked(folio, rwc: &rwc);
2213	else
2214	rmap_walk(folio, rwc: &rwc);
2215	}
2216
2217	#ifdef CONFIG_DEVICE_PRIVATE
2218	struct make_exclusive_args {
2219	struct mm_struct *mm;
2220	unsigned long address;
2221	void *owner;
2222	bool valid;
2223	};
2224
2225	static bool page_make_device_exclusive_one(struct folio *folio,
2226	struct vm_area_struct *vma, unsigned long address, void *priv)
2227	{
2228	struct mm_struct *mm = vma->vm_mm;
2229	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
2230	struct make_exclusive_args *args = priv;
2231	pte_t pteval;
2232	struct page *subpage;
2233	bool ret = true;
2234	struct mmu_notifier_range range;
2235	swp_entry_t entry;
2236	pte_t swp_pte;
2237	pte_t ptent;
2238
2239	mmu_notifier_range_init_owner(range: &range, event: MMU_NOTIFY_EXCLUSIVE, flags: 0,
2240	mm: vma->vm_mm, start: address, min(vma->vm_end,
2241	address + folio_size(folio)),
2242	owner: args->owner);
2243	mmu_notifier_invalidate_range_start(range: &range);
2244
2245	while (page_vma_mapped_walk(pvmw: &pvmw)) {
2246	/* Unexpected PMD-mapped THP? */
2247	VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2248
2249	ptent = ptep_get(ptep: pvmw.pte);
2250	if (!pte_present(a: ptent)) {
2251	ret = false;
2252	page_vma_mapped_walk_done(pvmw: &pvmw);
2253	break;
2254	}
2255
2256	subpage = folio_page(folio,
2257	pte_pfn(ptent) - folio_pfn(folio));
2258	address = pvmw.address;
2259
2260	/* Nuke the page table entry. */
2261	flush_cache_page(vma, vmaddr: address, pfn: pte_pfn(pte: ptent));
2262	pteval = ptep_clear_flush(vma, address, ptep: pvmw.pte);
2263
2264	/* Set the dirty flag on the folio now the pte is gone. */
2265	if (pte_dirty(pte: pteval))
2266	folio_mark_dirty(folio);
2267
2268	/*
2269	* Check that our target page is still mapped at the expected
2270	* address.
2271	*/
2272	if (args->mm == mm && args->address == address &&
2273	pte_write(pte: pteval))
2274	args->valid = true;
2275
2276	/*
2277	* Store the pfn of the page in a special migration
2278	* pte. do_swap_page() will wait until the migration
2279	* pte is removed and then restart fault handling.
2280	*/
2281	if (pte_write(pte: pteval))
2282	entry = make_writable_device_exclusive_entry(
2283	page_to_pfn(subpage));
2284	else
2285	entry = make_readable_device_exclusive_entry(
2286	page_to_pfn(subpage));
2287	swp_pte = swp_entry_to_pte(entry);
2288	if (pte_soft_dirty(pte: pteval))
2289	swp_pte = pte_swp_mksoft_dirty(pte: swp_pte);
2290	if (pte_uffd_wp(pte: pteval))
2291	swp_pte = pte_swp_mkuffd_wp(pte: swp_pte);
2292
2293	set_pte_at(mm, address, pvmw.pte, swp_pte);
2294
2295	/*
2296	* There is a reference on the page for the swap entry which has
2297	* been removed, so shouldn't take another.
2298	*/
2299	page_remove_rmap(page: subpage, vma, compound: false);
2300	}
2301
2302	mmu_notifier_invalidate_range_end(range: &range);
2303
2304	return ret;
2305	}
2306
2307	/**
2308	* folio_make_device_exclusive - Mark the folio exclusively owned by a device.
2309	* @folio: The folio to replace page table entries for.
2310	* @mm: The mm_struct where the folio is expected to be mapped.
2311	* @address: Address where the folio is expected to be mapped.
2312	* @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
2313	*
2314	* Tries to remove all the page table entries which are mapping this
2315	* folio and replace them with special device exclusive swap entries to
2316	* grant a device exclusive access to the folio.
2317	*
2318	* Context: Caller must hold the folio lock.
2319	* Return: false if the page is still mapped, or if it could not be unmapped
2320	* from the expected address. Otherwise returns true (success).
2321	*/
2322	static bool folio_make_device_exclusive(struct folio *folio,
2323	struct mm_struct *mm, unsigned long address, void *owner)
2324	{
2325	struct make_exclusive_args args = {
2326	.mm = mm,
2327	.address = address,
2328	.owner = owner,
2329	.valid = false,
2330	};
2331	struct rmap_walk_control rwc = {
2332	.rmap_one = page_make_device_exclusive_one,
2333	.done = folio_not_mapped,
2334	.anon_lock = folio_lock_anon_vma_read,
2335	.arg = &args,
2336	};
2337
2338	/*
2339	* Restrict to anonymous folios for now to avoid potential writeback
2340	* issues.
2341	*/
2342	if (!folio_test_anon(folio))
2343	return false;
2344
2345	rmap_walk(folio, rwc: &rwc);
2346
2347	return args.valid && !folio_mapcount(folio);
2348	}
2349
2350	/**
2351	* make_device_exclusive_range() - Mark a range for exclusive use by a device
2352	* @mm: mm_struct of associated target process
2353	* @start: start of the region to mark for exclusive device access
2354	* @end: end address of region
2355	* @pages: returns the pages which were successfully marked for exclusive access
2356	* @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
2357	*
2358	* Returns: number of pages found in the range by GUP. A page is marked for
2359	* exclusive access only if the page pointer is non-NULL.
2360	*
2361	* This function finds ptes mapping page(s) to the given address range, locks
2362	* them and replaces mappings with special swap entries preventing userspace CPU
2363	* access. On fault these entries are replaced with the original mapping after
2364	* calling MMU notifiers.
2365	*
2366	* A driver using this to program access from a device must use a mmu notifier
2367	* critical section to hold a device specific lock during programming. Once
2368	* programming is complete it should drop the page lock and reference after
2369	* which point CPU access to the page will revoke the exclusive access.
2370	*/
2371	int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
2372	unsigned long end, struct page **pages,
2373	void *owner)
2374	{
2375	long npages = (end - start) >> PAGE_SHIFT;
2376	long i;
2377
2378	npages = get_user_pages_remote(mm, start, nr_pages: npages,
2379	gup_flags: FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
2380	pages, NULL);
2381	if (npages < 0)
2382	return npages;
2383
2384	for (i = 0; i < npages; i++, start += PAGE_SIZE) {
2385	struct folio *folio = page_folio(pages[i]);
2386	if (PageTail(page: pages[i]) || !folio_trylock(folio)) {
2387	folio_put(folio);
2388	pages[i] = NULL;
2389	continue;
2390	}
2391
2392	if (!folio_make_device_exclusive(folio, mm, address: start, owner)) {
2393	folio_unlock(folio);
2394	folio_put(folio);
2395	pages[i] = NULL;
2396	}
2397	}
2398
2399	return npages;
2400	}
2401	EXPORT_SYMBOL_GPL(make_device_exclusive_range);
2402	#endif
2403
2404	void __put_anon_vma(struct anon_vma *anon_vma)
2405	{
2406	struct anon_vma *root = anon_vma->root;
2407
2408	anon_vma_free(anon_vma);
2409	if (root != anon_vma && atomic_dec_and_test(v: &root->refcount))
2410	anon_vma_free(anon_vma: root);
2411	}
2412
2413	static struct anon_vma *rmap_walk_anon_lock(struct folio *folio,
2414	struct rmap_walk_control *rwc)
2415	{
2416	struct anon_vma *anon_vma;
2417
2418	if (rwc->anon_lock)
2419	return rwc->anon_lock(folio, rwc);
2420
2421	/*
2422	* Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
2423	* because that depends on page_mapped(); but not all its usages
2424	* are holding mmap_lock. Users without mmap_lock are required to
2425	* take a reference count to prevent the anon_vma disappearing
2426	*/
2427	anon_vma = folio_anon_vma(folio);
2428	if (!anon_vma)
2429	return NULL;
2430
2431	if (anon_vma_trylock_read(anon_vma))
2432	goto out;
2433
2434	if (rwc->try_lock) {
2435	anon_vma = NULL;
2436	rwc->contended = true;
2437	goto out;
2438	}
2439
2440	anon_vma_lock_read(anon_vma);
2441	out:
2442	return anon_vma;
2443	}
2444
2445	/*
2446	* rmap_walk_anon - do something to anonymous page using the object-based
2447	* rmap method
2448	* @folio: the folio to be handled
2449	* @rwc: control variable according to each walk type
2450	* @locked: caller holds relevant rmap lock
2451	*
2452	* Find all the mappings of a folio using the mapping pointer and the vma
2453	* chains contained in the anon_vma struct it points to.
2454	*/
2455	static void rmap_walk_anon(struct folio *folio,
2456	struct rmap_walk_control *rwc, bool locked)
2457	{
2458	struct anon_vma *anon_vma;
2459	pgoff_t pgoff_start, pgoff_end;
2460	struct anon_vma_chain *avc;
2461
2462	if (locked) {
2463	anon_vma = folio_anon_vma(folio);
2464	/* anon_vma disappear under us? */
2465	VM_BUG_ON_FOLIO(!anon_vma, folio);
2466	} else {
2467	anon_vma = rmap_walk_anon_lock(folio, rwc);
2468	}
2469	if (!anon_vma)
2470	return;
2471
2472	pgoff_start = folio_pgoff(folio);
2473	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2474	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
2475	pgoff_start, pgoff_end) {
2476	struct vm_area_struct *vma = avc->vma;
2477	unsigned long address = vma_address(page: &folio->page, vma);
2478
2479	VM_BUG_ON_VMA(address == -EFAULT, vma);
2480	cond_resched();
2481
2482	if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2483	continue;
2484
2485	if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2486	break;
2487	if (rwc->done && rwc->done(folio))
2488	break;
2489	}
2490
2491	if (!locked)
2492	anon_vma_unlock_read(anon_vma);
2493	}
2494
2495	/*
2496	* rmap_walk_file - do something to file page using the object-based rmap method
2497	* @folio: the folio to be handled
2498	* @rwc: control variable according to each walk type
2499	* @locked: caller holds relevant rmap lock
2500	*
2501	* Find all the mappings of a folio using the mapping pointer and the vma chains
2502	* contained in the address_space struct it points to.
2503	*/
2504	static void rmap_walk_file(struct folio *folio,
2505	struct rmap_walk_control *rwc, bool locked)
2506	{
2507	struct address_space *mapping = folio_mapping(folio);
2508	pgoff_t pgoff_start, pgoff_end;
2509	struct vm_area_struct *vma;
2510
2511	/*
2512	* The page lock not only makes sure that page->mapping cannot
2513	* suddenly be NULLified by truncation, it makes sure that the
2514	* structure at mapping cannot be freed and reused yet,
2515	* so we can safely take mapping->i_mmap_rwsem.
2516	*/
2517	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2518
2519	if (!mapping)
2520	return;
2521
2522	pgoff_start = folio_pgoff(folio);
2523	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2524	if (!locked) {
2525	if (i_mmap_trylock_read(mapping))
2526	goto lookup;
2527
2528	if (rwc->try_lock) {
2529	rwc->contended = true;
2530	return;
2531	}
2532
2533	i_mmap_lock_read(mapping);
2534	}
2535	lookup:
2536	vma_interval_tree_foreach(vma, &mapping->i_mmap,
2537	pgoff_start, pgoff_end) {
2538	unsigned long address = vma_address(page: &folio->page, vma);
2539
2540	VM_BUG_ON_VMA(address == -EFAULT, vma);
2541	cond_resched();
2542
2543	if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2544	continue;
2545
2546	if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2547	goto done;
2548	if (rwc->done && rwc->done(folio))
2549	goto done;
2550	}
2551
2552	done:
2553	if (!locked)
2554	i_mmap_unlock_read(mapping);
2555	}
2556
2557	void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
2558	{
2559	if (unlikely(folio_test_ksm(folio)))
2560	rmap_walk_ksm(folio, rwc);
2561	else if (folio_test_anon(folio))
2562	rmap_walk_anon(folio, rwc, locked: false);
2563	else
2564	rmap_walk_file(folio, rwc, locked: false);
2565	}
2566
2567	/* Like rmap_walk, but caller holds relevant rmap lock */
2568	void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
2569	{
2570	/* no ksm support for now */
2571	VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
2572	if (folio_test_anon(folio))
2573	rmap_walk_anon(folio, rwc, locked: true);
2574	else
2575	rmap_walk_file(folio, rwc, locked: true);
2576	}
2577
2578	#ifdef CONFIG_HUGETLB_PAGE
2579	/*
2580	* The following two functions are for anonymous (private mapped) hugepages.
2581	* Unlike common anonymous pages, anonymous hugepages have no accounting code
2582	* and no lru code, because we handle hugepages differently from common pages.
2583	*
2584	* RMAP_COMPOUND is ignored.
2585	*/
2586	void hugepage_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
2587	unsigned long address, rmap_t flags)
2588	{
2589	VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
2590
2591	atomic_inc(v: &folio->_entire_mapcount);
2592	if (flags & RMAP_EXCLUSIVE)
2593	SetPageAnonExclusive(&folio->page);
2594	VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
2595	PageAnonExclusive(&folio->page), folio);
2596	}
2597
2598	void hugepage_add_new_anon_rmap(struct folio *folio,
2599	struct vm_area_struct *vma, unsigned long address)
2600	{
2601	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
2602	/* increment count (starts at -1) */
2603	atomic_set(v: &folio->_entire_mapcount, i: 0);
2604	folio_clear_hugetlb_restore_reserve(folio);
2605	__folio_set_anon(folio, vma, address, exclusive: true);
2606	SetPageAnonExclusive(&folio->page);
2607	}
2608	#endif /* CONFIG_HUGETLB_PAGE */
2609