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Root/mm/rmap.c

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	* mapping->i_mmap_mutex
27	* anon_vma->rwsem
28	* mm->page_table_lock or pte_lock
29	* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
30	* swap_lock (in swap_duplicate, swap_info_get)
31	* mmlist_lock (in mmput, drain_mmlist and others)
32	* mapping->private_lock (in __set_page_dirty_buffers)
33	* inode->i_lock (in set_page_dirty's __mark_inode_dirty)
34	* bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
35	* sb_lock (within inode_lock in fs/fs-writeback.c)
36	* mapping->tree_lock (widely used, in set_page_dirty,
37	* in arch-dependent flush_dcache_mmap_lock,
38	* within bdi.wb->list_lock in __sync_single_inode)
39	*
40	* anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
41	* ->tasklist_lock
42	* pte map lock
43	*/
44
45	#include <linux/mm.h>
46	#include <linux/pagemap.h>
47	#include <linux/swap.h>
48	#include <linux/swapops.h>
49	#include <linux/slab.h>
50	#include <linux/init.h>
51	#include <linux/ksm.h>
52	#include <linux/rmap.h>
53	#include <linux/rcupdate.h>
54	#include <linux/export.h>
55	#include <linux/memcontrol.h>
56	#include <linux/mmu_notifier.h>
57	#include <linux/migrate.h>
58	#include <linux/hugetlb.h>
59	#include <linux/backing-dev.h>
60
61	#include <asm/tlbflush.h>
62
63	#include "internal.h"
64
65	static struct kmem_cache *anon_vma_cachep;
66	static struct kmem_cache *anon_vma_chain_cachep;
67
68	static inline struct anon_vma *anon_vma_alloc(void)
69	{
70	struct anon_vma *anon_vma;
71
72	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
73	if (anon_vma) {
74	atomic_set(&anon_vma->refcount, 1);
75	/*
76	* Initialise the anon_vma root to point to itself. If called
77	* from fork, the root will be reset to the parents anon_vma.
78	*/
79	anon_vma->root = anon_vma;
80	}
81
82	return anon_vma;
83	}
84
85	static inline void anon_vma_free(struct anon_vma *anon_vma)
86	{
87	VM_BUG_ON(atomic_read(&anon_vma->refcount));
88
89	/*
90	* Synchronize against page_lock_anon_vma_read() such that
91	* we can safely hold the lock without the anon_vma getting
92	* freed.
93	*
94	* Relies on the full mb implied by the atomic_dec_and_test() from
95	* put_anon_vma() against the acquire barrier implied by
96	* down_read_trylock() from page_lock_anon_vma_read(). This orders:
97	*
98	* page_lock_anon_vma_read() VS put_anon_vma()
99	* down_read_trylock() atomic_dec_and_test()
100	* LOCK MB
101	* atomic_read() rwsem_is_locked()
102	*
103	* LOCK should suffice since the actual taking of the lock must
104	* happen _before_ what follows.
105	*/
106	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
107	anon_vma_lock_write(anon_vma);
108	anon_vma_unlock_write(anon_vma);
109	}
110
111	kmem_cache_free(anon_vma_cachep, anon_vma);
112	}
113
114	static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
115	{
116	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
117	}
118
119	static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
120	{
121	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
122	}
123
124	static void anon_vma_chain_link(struct vm_area_struct *vma,
125	struct anon_vma_chain *avc,
126	struct anon_vma *anon_vma)
127	{
128	avc->vma = vma;
129	avc->anon_vma = anon_vma;
130	list_add(&avc->same_vma, &vma->anon_vma_chain);
131	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
132	}
133
134	/**
135	* anon_vma_prepare - attach an anon_vma to a memory region
136	* @vma: the memory region in question
137	*
138	* This makes sure the memory mapping described by 'vma' has
139	* an 'anon_vma' attached to it, so that we can associate the
140	* anonymous pages mapped into it with that anon_vma.
141	*
142	* The common case will be that we already have one, but if
143	* not we either need to find an adjacent mapping that we
144	* can re-use the anon_vma from (very common when the only
145	* reason for splitting a vma has been mprotect()), or we
146	* allocate a new one.
147	*
148	* Anon-vma allocations are very subtle, because we may have
149	* optimistically looked up an anon_vma in page_lock_anon_vma_read()
150	* and that may actually touch the spinlock even in the newly
151	* allocated vma (it depends on RCU to make sure that the
152	* anon_vma isn't actually destroyed).
153	*
154	* As a result, we need to do proper anon_vma locking even
155	* for the new allocation. At the same time, we do not want
156	* to do any locking for the common case of already having
157	* an anon_vma.
158	*
159	* This must be called with the mmap_sem held for reading.
160	*/
161	int anon_vma_prepare(struct vm_area_struct *vma)
162	{
163	struct anon_vma *anon_vma = vma->anon_vma;
164	struct anon_vma_chain *avc;
165
166	might_sleep();
167	if (unlikely(!anon_vma)) {
168	struct mm_struct *mm = vma->vm_mm;
169	struct anon_vma *allocated;
170
171	avc = anon_vma_chain_alloc(GFP_KERNEL);
172	if (!avc)
173	goto out_enomem;
174
175	anon_vma = find_mergeable_anon_vma(vma);
176	allocated = NULL;
177	if (!anon_vma) {
178	anon_vma = anon_vma_alloc();
179	if (unlikely(!anon_vma))
180	goto out_enomem_free_avc;
181	allocated = anon_vma;
182	}
183
184	anon_vma_lock_write(anon_vma);
185	/* page_table_lock to protect against threads */
186	spin_lock(&mm->page_table_lock);
187	if (likely(!vma->anon_vma)) {
188	vma->anon_vma = anon_vma;
189	anon_vma_chain_link(vma, avc, anon_vma);
190	allocated = NULL;
191	avc = NULL;
192	}
193	spin_unlock(&mm->page_table_lock);
194	anon_vma_unlock_write(anon_vma);
195
196	if (unlikely(allocated))
197	put_anon_vma(allocated);
198	if (unlikely(avc))
199	anon_vma_chain_free(avc);
200	}
201	return 0;
202
203	out_enomem_free_avc:
204	anon_vma_chain_free(avc);
205	out_enomem:
206	return -ENOMEM;
207	}
208
209	/*
210	* This is a useful helper function for locking the anon_vma root as
211	* we traverse the vma->anon_vma_chain, looping over anon_vma's that
212	* have the same vma.
213	*
214	* Such anon_vma's should have the same root, so you'd expect to see
215	* just a single mutex_lock for the whole traversal.
216	*/
217	static inline struct anon_vma lock_anon_vma_root(struct anon_vma root, struct anon_vma *anon_vma)
218	{
219	struct anon_vma *new_root = anon_vma->root;
220	if (new_root != root) {
221	if (WARN_ON_ONCE(root))
222	up_write(&root->rwsem);
223	root = new_root;
224	down_write(&root->rwsem);
225	}
226	return root;
227	}
228
229	static inline void unlock_anon_vma_root(struct anon_vma *root)
230	{
231	if (root)
232	up_write(&root->rwsem);
233	}
234
235	/*
236	* Attach the anon_vmas from src to dst.
237	* Returns 0 on success, -ENOMEM on failure.
238	*/
239	int anon_vma_clone(struct vm_area_struct dst, struct vm_area_struct src)
240	{
241	struct anon_vma_chain avc, pavc;
242	struct anon_vma *root = NULL;
243
244	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
245	struct anon_vma *anon_vma;
246
247	avc = anon_vma_chain_alloc(GFP_NOWAIT \| __GFP_NOWARN);
248	if (unlikely(!avc)) {
249	unlock_anon_vma_root(root);
250	root = NULL;
251	avc = anon_vma_chain_alloc(GFP_KERNEL);
252	if (!avc)
253	goto enomem_failure;
254	}
255	anon_vma = pavc->anon_vma;
256	root = lock_anon_vma_root(root, anon_vma);
257	anon_vma_chain_link(dst, avc, anon_vma);
258	}
259	unlock_anon_vma_root(root);
260	return 0;
261
262	enomem_failure:
263	unlink_anon_vmas(dst);
264	return -ENOMEM;
265	}
266
267	/*
268	* Attach vma to its own anon_vma, as well as to the anon_vmas that
269	* the corresponding VMA in the parent process is attached to.
270	* Returns 0 on success, non-zero on failure.
271	*/
272	int anon_vma_fork(struct vm_area_struct vma, struct vm_area_struct pvma)
273	{
274	struct anon_vma_chain *avc;
275	struct anon_vma *anon_vma;
276
277	/* Don't bother if the parent process has no anon_vma here. */
278	if (!pvma->anon_vma)
279	return 0;
280
281	/*
282	* First, attach the new VMA to the parent VMA's anon_vmas,
283	* so rmap can find non-COWed pages in child processes.
284	*/
285	if (anon_vma_clone(vma, pvma))
286	return -ENOMEM;
287
288	/* Then add our own anon_vma. */
289	anon_vma = anon_vma_alloc();
290	if (!anon_vma)
291	goto out_error;
292	avc = anon_vma_chain_alloc(GFP_KERNEL);
293	if (!avc)
294	goto out_error_free_anon_vma;
295
296	/*
297	* The root anon_vma's spinlock is the lock actually used when we
298	* lock any of the anon_vmas in this anon_vma tree.
299	*/
300	anon_vma->root = pvma->anon_vma->root;
301	/*
302	* With refcounts, an anon_vma can stay around longer than the
303	* process it belongs to. The root anon_vma needs to be pinned until
304	* this anon_vma is freed, because the lock lives in the root.
305	*/
306	get_anon_vma(anon_vma->root);
307	/* Mark this anon_vma as the one where our new (COWed) pages go. */
308	vma->anon_vma = anon_vma;
309	anon_vma_lock_write(anon_vma);
310	anon_vma_chain_link(vma, avc, anon_vma);
311	anon_vma_unlock_write(anon_vma);
312
313	return 0;
314
315	out_error_free_anon_vma:
316	put_anon_vma(anon_vma);
317	out_error:
318	unlink_anon_vmas(vma);
319	return -ENOMEM;
320	}
321
322	void unlink_anon_vmas(struct vm_area_struct *vma)
323	{
324	struct anon_vma_chain avc, next;
325	struct anon_vma *root = NULL;
326
327	/*
328	* Unlink each anon_vma chained to the VMA. This list is ordered
329	* from newest to oldest, ensuring the root anon_vma gets freed last.
330	*/
331	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
332	struct anon_vma *anon_vma = avc->anon_vma;
333
334	root = lock_anon_vma_root(root, anon_vma);
335	anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
336
337	/*
338	* Leave empty anon_vmas on the list - we'll need
339	* to free them outside the lock.
340	*/
341	if (RB_EMPTY_ROOT(&anon_vma->rb_root))
342	continue;
343
344	list_del(&avc->same_vma);
345	anon_vma_chain_free(avc);
346	}
347	unlock_anon_vma_root(root);
348
349	/*
350	* Iterate the list once more, it now only contains empty and unlinked
351	* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
352	* needing to write-acquire the anon_vma->root->rwsem.
353	*/
354	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
355	struct anon_vma *anon_vma = avc->anon_vma;
356
357	put_anon_vma(anon_vma);
358
359	list_del(&avc->same_vma);
360	anon_vma_chain_free(avc);
361	}
362	}
363
364	static void anon_vma_ctor(void *data)
365	{
366	struct anon_vma *anon_vma = data;
367
368	init_rwsem(&anon_vma->rwsem);
369	atomic_set(&anon_vma->refcount, 0);
370	anon_vma->rb_root = RB_ROOT;
371	}
372
373	void __init anon_vma_init(void)
374	{
375	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
376	0, SLAB_DESTROY_BY_RCU\|SLAB_PANIC, anon_vma_ctor);
377	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
378	}
379
380	/*
381	* Getting a lock on a stable anon_vma from a page off the LRU is tricky!
382	*
383	* Since there is no serialization what so ever against page_remove_rmap()
384	* the best this function can do is return a locked anon_vma that might
385	* have been relevant to this page.
386	*
387	* The page might have been remapped to a different anon_vma or the anon_vma
388	* returned may already be freed (and even reused).
389	*
390	* In case it was remapped to a different anon_vma, the new anon_vma will be a
391	* child of the old anon_vma, and the anon_vma lifetime rules will therefore
392	* ensure that any anon_vma obtained from the page will still be valid for as
393	* long as we observe page_mapped() [ hence all those page_mapped() tests ].
394	*
395	* All users of this function must be very careful when walking the anon_vma
396	* chain and verify that the page in question is indeed mapped in it
397	* [ something equivalent to page_mapped_in_vma() ].
398	*
399	* Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
400	* that the anon_vma pointer from page->mapping is valid if there is a
401	* mapcount, we can dereference the anon_vma after observing those.
402	*/
403	struct anon_vma page_get_anon_vma(struct page page)
404	{
405	struct anon_vma *anon_vma = NULL;
406	unsigned long anon_mapping;
407
408	rcu_read_lock();
409	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
410	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
411	goto out;
412	if (!page_mapped(page))
413	goto out;
414
415	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
416	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
417	anon_vma = NULL;
418	goto out;
419	}
420
421	/*
422	* If this page is still mapped, then its anon_vma cannot have been
423	* freed. But if it has been unmapped, we have no security against the
424	* anon_vma structure being freed and reused (for another anon_vma:
425	* SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
426	* above cannot corrupt).
427	*/
428	if (!page_mapped(page)) {
429	put_anon_vma(anon_vma);
430	anon_vma = NULL;
431	}
432	out:
433	rcu_read_unlock();
434
435	return anon_vma;
436	}
437
438	/*
439	* Similar to page_get_anon_vma() except it locks the anon_vma.
440	*
441	* Its a little more complex as it tries to keep the fast path to a single
442	* atomic op -- the trylock. If we fail the trylock, we fall back to getting a
443	* reference like with page_get_anon_vma() and then block on the mutex.
444	*/
445	struct anon_vma page_lock_anon_vma_read(struct page page)
446	{
447	struct anon_vma *anon_vma = NULL;
448	struct anon_vma *root_anon_vma;
449	unsigned long anon_mapping;
450
451	rcu_read_lock();
452	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
453	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
454	goto out;
455	if (!page_mapped(page))
456	goto out;
457
458	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
459	root_anon_vma = ACCESS_ONCE(anon_vma->root);
460	if (down_read_trylock(&root_anon_vma->rwsem)) {
461	/*
462	* If the page is still mapped, then this anon_vma is still
463	* its anon_vma, and holding the mutex ensures that it will
464	* not go away, see anon_vma_free().
465	*/
466	if (!page_mapped(page)) {
467	up_read(&root_anon_vma->rwsem);
468	anon_vma = NULL;
469	}
470	goto out;
471	}
472
473	/* trylock failed, we got to sleep */
474	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
475	anon_vma = NULL;
476	goto out;
477	}
478
479	if (!page_mapped(page)) {
480	put_anon_vma(anon_vma);
481	anon_vma = NULL;
482	goto out;
483	}
484
485	/* we pinned the anon_vma, its safe to sleep */
486	rcu_read_unlock();
487	anon_vma_lock_read(anon_vma);
488
489	if (atomic_dec_and_test(&anon_vma->refcount)) {
490	/*
491	* Oops, we held the last refcount, release the lock
492	* and bail -- can't simply use put_anon_vma() because
493	* we'll deadlock on the anon_vma_lock_write() recursion.
494	*/
495	anon_vma_unlock_read(anon_vma);
496	__put_anon_vma(anon_vma);
497	anon_vma = NULL;
498	}
499
500	return anon_vma;
501
502	out:
503	rcu_read_unlock();
504	return anon_vma;
505	}
506
507	void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
508	{
509	anon_vma_unlock_read(anon_vma);
510	}
511
512	/*
513	* At what user virtual address is page expected in @vma?
514	*/
515	static inline unsigned long
516	__vma_address(struct page page, struct vm_area_struct vma)
517	{
518	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
519
520	if (unlikely(is_vm_hugetlb_page(vma)))
521	pgoff = page->index << huge_page_order(page_hstate(page));
522
523	return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
524	}
525
526	inline unsigned long
527	vma_address(struct page page, struct vm_area_struct vma)
528	{
529	unsigned long address = __vma_address(page, vma);
530
531	/* page should be within @vma mapping range */
532	VM_BUG_ON(address < vma->vm_start \|\| address >= vma->vm_end);
533
534	return address;
535	}
536
537	/*
538	* At what user virtual address is page expected in vma?
539	* Caller should check the page is actually part of the vma.
540	*/
541	unsigned long page_address_in_vma(struct page page, struct vm_area_struct vma)
542	{
543	unsigned long address;
544	if (PageAnon(page)) {
545	struct anon_vma *page__anon_vma = page_anon_vma(page);
546	/*
547	* Note: swapoff's unuse_vma() is more efficient with this
548	* check, and needs it to match anon_vma when KSM is active.
549	*/
550	if (!vma->anon_vma \|\| !page__anon_vma \|\|
551	vma->anon_vma->root != page__anon_vma->root)
552	return -EFAULT;
553	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
554	if (!vma->vm_file \|\|
555	vma->vm_file->f_mapping != page->mapping)
556	return -EFAULT;
557	} else
558	return -EFAULT;
559	address = __vma_address(page, vma);
560	if (unlikely(address < vma->vm_start \|\| address >= vma->vm_end))
561	return -EFAULT;
562	return address;
563	}
564
565	pmd_t mm_find_pmd(struct mm_struct mm, unsigned long address)
566	{
567	pgd_t *pgd;
568	pud_t *pud;
569	pmd_t *pmd = NULL;
570
571	pgd = pgd_offset(mm, address);
572	if (!pgd_present(*pgd))
573	goto out;
574
575	pud = pud_offset(pgd, address);
576	if (!pud_present(*pud))
577	goto out;
578
579	pmd = pmd_offset(pud, address);
580	if (!pmd_present(*pmd))
581	pmd = NULL;
582	out:
583	return pmd;
584	}
585
586	/*
587	* Check that @page is mapped at @address into @mm.
588	*
589	* If @sync is false, page_check_address may perform a racy check to avoid
590	* the page table lock when the pte is not present (helpful when reclaiming
591	* highly shared pages).
592	*
593	* On success returns with pte mapped and locked.
594	*/
595	pte_t __page_check_address(struct page page, struct mm_struct *mm,
596	unsigned long address, spinlock_t **ptlp, int sync)
597	{
598	pmd_t *pmd;
599	pte_t *pte;
600	spinlock_t *ptl;
601
602	if (unlikely(PageHuge(page))) {
603	pte = huge_pte_offset(mm, address);
604	ptl = &mm->page_table_lock;
605	goto check;
606	}
607
608	pmd = mm_find_pmd(mm, address);
609	if (!pmd)
610	return NULL;
611
612	if (pmd_trans_huge(*pmd))
613	return NULL;
614
615	pte = pte_offset_map(pmd, address);
616	/* Make a quick check before getting the lock */
617	if (!sync && !pte_present(*pte)) {
618	pte_unmap(pte);
619	return NULL;
620	}
621
622	ptl = pte_lockptr(mm, pmd);
623	check:
624	spin_lock(ptl);
625	if (pte_present(pte) && page_to_pfn(page) == pte_pfn(pte)) {
626	*ptlp = ptl;
627	return pte;
628	}
629	pte_unmap_unlock(pte, ptl);
630	return NULL;
631	}
632
633	/**
634	* page_mapped_in_vma - check whether a page is really mapped in a VMA
635	* @page: the page to test
636	* @vma: the VMA to test
637	*
638	* Returns 1 if the page is mapped into the page tables of the VMA, 0
639	* if the page is not mapped into the page tables of this VMA. Only
640	* valid for normal file or anonymous VMAs.
641	*/
642	int page_mapped_in_vma(struct page page, struct vm_area_struct vma)
643	{
644	unsigned long address;
645	pte_t *pte;
646	spinlock_t *ptl;
647
648	address = __vma_address(page, vma);
649	if (unlikely(address < vma->vm_start \|\| address >= vma->vm_end))
650	return 0;
651	pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
652	if (!pte) /* the page is not in this mm */
653	return 0;
654	pte_unmap_unlock(pte, ptl);
655
656	return 1;
657	}
658
659	/*
660	* Subfunctions of page_referenced: page_referenced_one called
661	* repeatedly from either page_referenced_anon or page_referenced_file.
662	*/
663	int page_referenced_one(struct page page, struct vm_area_struct vma,
664	unsigned long address, unsigned int *mapcount,
665	unsigned long *vm_flags)
666	{
667	struct mm_struct *mm = vma->vm_mm;
668	int referenced = 0;
669
670	if (unlikely(PageTransHuge(page))) {
671	pmd_t *pmd;
672
673	spin_lock(&mm->page_table_lock);
674	/*
675	* rmap might return false positives; we must filter
676	* these out using page_check_address_pmd().
677	*/
678	pmd = page_check_address_pmd(page, mm, address,
679	PAGE_CHECK_ADDRESS_PMD_FLAG);
680	if (!pmd) {
681	spin_unlock(&mm->page_table_lock);
682	goto out;
683	}
684
685	if (vma->vm_flags & VM_LOCKED) {
686	spin_unlock(&mm->page_table_lock);
687	mapcount = 0; / break early from loop */
688	*vm_flags \|= VM_LOCKED;
689	goto out;
690	}
691
692	/* go ahead even if the pmd is pmd_trans_splitting() */
693	if (pmdp_clear_flush_young_notify(vma, address, pmd))
694	referenced++;
695	spin_unlock(&mm->page_table_lock);
696	} else {
697	pte_t *pte;
698	spinlock_t *ptl;
699
700	/*
701	* rmap might return false positives; we must filter
702	* these out using page_check_address().
703	*/
704	pte = page_check_address(page, mm, address, &ptl, 0);
705	if (!pte)
706	goto out;
707
708	if (vma->vm_flags & VM_LOCKED) {
709	pte_unmap_unlock(pte, ptl);
710	mapcount = 0; / break early from loop */
711	*vm_flags \|= VM_LOCKED;
712	goto out;
713	}
714
715	if (ptep_clear_flush_young_notify(vma, address, pte)) {
716	/*
717	* Don't treat a reference through a sequentially read
718	* mapping as such. If the page has been used in
719	* another mapping, we will catch it; if this other
720	* mapping is already gone, the unmap path will have
721	* set PG_referenced or activated the page.
722	*/
723	if (likely(!(vma->vm_flags & VM_SEQ_READ)))
724	referenced++;
725	}
726	pte_unmap_unlock(pte, ptl);
727	}
728
729	(*mapcount)--;
730
731	if (referenced)
732	*vm_flags \|= vma->vm_flags;
733	out:
734	return referenced;
735	}
736
737	static int page_referenced_anon(struct page *page,
738	struct mem_cgroup *memcg,
739	unsigned long *vm_flags)
740	{
741	unsigned int mapcount;
742	struct anon_vma *anon_vma;
743	pgoff_t pgoff;
744	struct anon_vma_chain *avc;
745	int referenced = 0;
746
747	anon_vma = page_lock_anon_vma_read(page);
748	if (!anon_vma)
749	return referenced;
750
751	mapcount = page_mapcount(page);
752	pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
753	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
754	struct vm_area_struct *vma = avc->vma;
755	unsigned long address = vma_address(page, vma);
756	/*
757	* If we are reclaiming on behalf of a cgroup, skip
758	* counting on behalf of references from different
759	* cgroups
760	*/
761	if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
762	continue;
763	referenced += page_referenced_one(page, vma, address,
764	&mapcount, vm_flags);
765	if (!mapcount)
766	break;
767	}
768
769	page_unlock_anon_vma_read(anon_vma);
770	return referenced;
771	}
772
773	/**
774	* page_referenced_file - referenced check for object-based rmap
775	* @page: the page we're checking references on.
776	* @memcg: target memory control group
777	* @vm_flags: collect encountered vma->vm_flags who actually referenced the page
778	*
779	* For an object-based mapped page, find all the places it is mapped and
780	* check/clear the referenced flag. This is done by following the page->mapping
781	* pointer, then walking the chain of vmas it holds. It returns the number
782	* of references it found.
783	*
784	* This function is only called from page_referenced for object-based pages.
785	*/
786	static int page_referenced_file(struct page *page,
787	struct mem_cgroup *memcg,
788	unsigned long *vm_flags)
789	{
790	unsigned int mapcount;
791	struct address_space *mapping = page->mapping;
792	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
793	struct vm_area_struct *vma;
794	int referenced = 0;
795
796	/*
797	* The caller's checks on page->mapping and !PageAnon have made
798	* sure that this is a file page: the check for page->mapping
799	* excludes the case just before it gets set on an anon page.
800	*/
801	BUG_ON(PageAnon(page));
802
803	/*
804	* The page lock not only makes sure that page->mapping cannot
805	* suddenly be NULLified by truncation, it makes sure that the
806	* structure at mapping cannot be freed and reused yet,
807	* so we can safely take mapping->i_mmap_mutex.
808	*/
809	BUG_ON(!PageLocked(page));
810
811	mutex_lock(&mapping->i_mmap_mutex);
812
813	/*
814	* i_mmap_mutex does not stabilize mapcount at all, but mapcount
815	* is more likely to be accurate if we note it after spinning.
816	*/
817	mapcount = page_mapcount(page);
818
819	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
820	unsigned long address = vma_address(page, vma);
821	/*
822	* If we are reclaiming on behalf of a cgroup, skip
823	* counting on behalf of references from different
824	* cgroups
825	*/
826	if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
827	continue;
828	referenced += page_referenced_one(page, vma, address,
829	&mapcount, vm_flags);
830	if (!mapcount)
831	break;
832	}
833
834	mutex_unlock(&mapping->i_mmap_mutex);
835	return referenced;
836	}
837
838	/**
839	* page_referenced - test if the page was referenced
840	* @page: the page to test
841	* @is_locked: caller holds lock on the page
842	* @memcg: target memory cgroup
843	* @vm_flags: collect encountered vma->vm_flags who actually referenced the page
844	*
845	* Quick test_and_clear_referenced for all mappings to a page,
846	* returns the number of ptes which referenced the page.
847	*/
848	int page_referenced(struct page *page,
849	int is_locked,
850	struct mem_cgroup *memcg,
851	unsigned long *vm_flags)
852	{
853	int referenced = 0;
854	int we_locked = 0;
855
856	*vm_flags = 0;
857	if (page_mapped(page) && page_rmapping(page)) {
858	if (!is_locked && (!PageAnon(page) \|\| PageKsm(page))) {
859	we_locked = trylock_page(page);
860	if (!we_locked) {
861	referenced++;
862	goto out;
863	}
864	}
865	if (unlikely(PageKsm(page)))
866	referenced += page_referenced_ksm(page, memcg,
867	vm_flags);
868	else if (PageAnon(page))
869	referenced += page_referenced_anon(page, memcg,
870	vm_flags);
871	else if (page->mapping)
872	referenced += page_referenced_file(page, memcg,
873	vm_flags);
874	if (we_locked)
875	unlock_page(page);
876	}
877	out:
878	return referenced;
879	}
880
881	static int page_mkclean_one(struct page page, struct vm_area_struct vma,
882	unsigned long address)
883	{
884	struct mm_struct *mm = vma->vm_mm;
885	pte_t *pte;
886	spinlock_t *ptl;
887	int ret = 0;
888
889	pte = page_check_address(page, mm, address, &ptl, 1);
890	if (!pte)
891	goto out;
892
893	if (pte_dirty(pte) \|\| pte_write(pte)) {
894	pte_t entry;
895
896	flush_cache_page(vma, address, pte_pfn(*pte));
897	entry = ptep_clear_flush(vma, address, pte);
898	entry = pte_wrprotect(entry);
899	entry = pte_mkclean(entry);
900	set_pte_at(mm, address, pte, entry);
901	ret = 1;
902	}
903
904	pte_unmap_unlock(pte, ptl);
905
906	if (ret)
907	mmu_notifier_invalidate_page(mm, address);
908	out:
909	return ret;
910	}
911
912	static int page_mkclean_file(struct address_space mapping, struct page page)
913	{
914	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
915	struct vm_area_struct *vma;
916	int ret = 0;
917
918	BUG_ON(PageAnon(page));
919
920	mutex_lock(&mapping->i_mmap_mutex);
921	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
922	if (vma->vm_flags & VM_SHARED) {
923	unsigned long address = vma_address(page, vma);
924	ret += page_mkclean_one(page, vma, address);
925	}
926	}
927	mutex_unlock(&mapping->i_mmap_mutex);
928	return ret;
929	}
930
931	int page_mkclean(struct page *page)
932	{
933	int ret = 0;
934
935	BUG_ON(!PageLocked(page));
936
937	if (page_mapped(page)) {
938	struct address_space *mapping = page_mapping(page);
939	if (mapping)
940	ret = page_mkclean_file(mapping, page);
941	}
942
943	return ret;
944	}
945	EXPORT_SYMBOL_GPL(page_mkclean);
946
947	/**
948	* page_move_anon_rmap - move a page to our anon_vma
949	* @page: the page to move to our anon_vma
950	* @vma: the vma the page belongs to
951	* @address: the user virtual address mapped
952	*
953	* When a page belongs exclusively to one process after a COW event,
954	* that page can be moved into the anon_vma that belongs to just that
955	* process, so the rmap code will not search the parent or sibling
956	* processes.
957	*/
958	void page_move_anon_rmap(struct page *page,
959	struct vm_area_struct *vma, unsigned long address)
960	{
961	struct anon_vma *anon_vma = vma->anon_vma;
962
963	VM_BUG_ON(!PageLocked(page));
964	VM_BUG_ON(!anon_vma);
965	VM_BUG_ON(page->index != linear_page_index(vma, address));
966
967	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
968	page->mapping = (struct address_space *) anon_vma;
969	}
970
971	/**
972	* __page_set_anon_rmap - set up new anonymous rmap
973	* @page: Page to add to rmap
974	* @vma: VM area to add page to.
975	* @address: User virtual address of the mapping
976	* @exclusive: the page is exclusively owned by the current process
977	*/
978	static void __page_set_anon_rmap(struct page *page,
979	struct vm_area_struct *vma, unsigned long address, int exclusive)
980	{
981	struct anon_vma *anon_vma = vma->anon_vma;
982
983	BUG_ON(!anon_vma);
984
985	if (PageAnon(page))
986	return;
987
988	/*
989	* If the page isn't exclusively mapped into this vma,
990	* we must use the _oldest_ possible anon_vma for the
991	* page mapping!
992	*/
993	if (!exclusive)
994	anon_vma = anon_vma->root;
995
996	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
997	page->mapping = (struct address_space *) anon_vma;
998	page->index = linear_page_index(vma, address);
999	}
1000
1001	/**
1002	* __page_check_anon_rmap - sanity check anonymous rmap addition
1003	* @page: the page to add the mapping to
1004	* @vma: the vm area in which the mapping is added
1005	* @address: the user virtual address mapped
1006	*/
1007	static void __page_check_anon_rmap(struct page *page,
1008	struct vm_area_struct *vma, unsigned long address)
1009	{
1010	#ifdef CONFIG_DEBUG_VM
1011	/*
1012	* The page's anon-rmap details (mapping and index) are guaranteed to
1013	* be set up correctly at this point.
1014	*
1015	* We have exclusion against page_add_anon_rmap because the caller
1016	* always holds the page locked, except if called from page_dup_rmap,
1017	* in which case the page is already known to be setup.
1018	*
1019	* We have exclusion against page_add_new_anon_rmap because those pages
1020	* are initially only visible via the pagetables, and the pte is locked
1021	* over the call to page_add_new_anon_rmap.
1022	*/
1023	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1024	BUG_ON(page->index != linear_page_index(vma, address));
1025	#endif
1026	}
1027
1028	/**
1029	* page_add_anon_rmap - add pte mapping to an anonymous page
1030	* @page: the page to add the mapping to
1031	* @vma: the vm area in which the mapping is added
1032	* @address: the user virtual address mapped
1033	*
1034	* The caller needs to hold the pte lock, and the page must be locked in
1035	* the anon_vma case: to serialize mapping,index checking after setting,
1036	* and to ensure that PageAnon is not being upgraded racily to PageKsm
1037	* (but PageKsm is never downgraded to PageAnon).
1038	*/
1039	void page_add_anon_rmap(struct page *page,
1040	struct vm_area_struct *vma, unsigned long address)
1041	{
1042	do_page_add_anon_rmap(page, vma, address, 0);
1043	}
1044
1045	/*
1046	* Special version of the above for do_swap_page, which often runs
1047	* into pages that are exclusively owned by the current process.
1048	* Everybody else should continue to use page_add_anon_rmap above.
1049	*/
1050	void do_page_add_anon_rmap(struct page *page,
1051	struct vm_area_struct *vma, unsigned long address, int exclusive)
1052	{
1053	int first = atomic_inc_and_test(&page->_mapcount);
1054	if (first) {
1055	if (PageTransHuge(page))
1056	__inc_zone_page_state(page,
1057	NR_ANON_TRANSPARENT_HUGEPAGES);
1058	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1059	hpage_nr_pages(page));
1060	}
1061	if (unlikely(PageKsm(page)))
1062	return;
1063
1064	VM_BUG_ON(!PageLocked(page));
1065	/* address might be in next vma when migration races vma_adjust */
1066	if (first)
1067	__page_set_anon_rmap(page, vma, address, exclusive);
1068	else
1069	__page_check_anon_rmap(page, vma, address);
1070	}
1071
1072	/**
1073	* page_add_new_anon_rmap - add pte mapping to a new anonymous page
1074	* @page: the page to add the mapping to
1075	* @vma: the vm area in which the mapping is added
1076	* @address: the user virtual address mapped
1077	*
1078	* Same as page_add_anon_rmap but must only be called on new pages.
1079	* This means the inc-and-test can be bypassed.
1080	* Page does not have to be locked.
1081	*/
1082	void page_add_new_anon_rmap(struct page *page,
1083	struct vm_area_struct *vma, unsigned long address)
1084	{
1085	VM_BUG_ON(address < vma->vm_start \|\| address >= vma->vm_end);
1086	SetPageSwapBacked(page);
1087	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1088	if (PageTransHuge(page))
1089	__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1090	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1091	hpage_nr_pages(page));
1092	__page_set_anon_rmap(page, vma, address, 1);
1093	if (!mlocked_vma_newpage(vma, page)) {
1094	SetPageActive(page);
1095	lru_cache_add(page);
1096	} else
1097	add_page_to_unevictable_list(page);
1098	}
1099
1100	/**
1101	* page_add_file_rmap - add pte mapping to a file page
1102	* @page: the page to add the mapping to
1103	*
1104	* The caller needs to hold the pte lock.
1105	*/
1106	void page_add_file_rmap(struct page *page)
1107	{
1108	bool locked;
1109	unsigned long flags;
1110
1111	mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1112	if (atomic_inc_and_test(&page->_mapcount)) {
1113	__inc_zone_page_state(page, NR_FILE_MAPPED);
1114	mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1115	}
1116	mem_cgroup_end_update_page_stat(page, &locked, &flags);
1117	}
1118
1119	/**
1120	* page_remove_rmap - take down pte mapping from a page
1121	* @page: page to remove mapping from
1122	*
1123	* The caller needs to hold the pte lock.
1124	*/
1125	void page_remove_rmap(struct page *page)
1126	{
1127	bool anon = PageAnon(page);
1128	bool locked;
1129	unsigned long flags;
1130
1131	/*
1132	* The anon case has no mem_cgroup page_stat to update; but may
1133	* uncharge_page() below, where the lock ordering can deadlock if
1134	* we hold the lock against page_stat move: so avoid it on anon.
1135	*/
1136	if (!anon)
1137	mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1138
1139	/* page still mapped by someone else? */
1140	if (!atomic_add_negative(-1, &page->_mapcount))
1141	goto out;
1142
1143	/*
1144	* Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1145	* and not charged by memcg for now.
1146	*/
1147	if (unlikely(PageHuge(page)))
1148	goto out;
1149	if (anon) {
1150	mem_cgroup_uncharge_page(page);
1151	if (PageTransHuge(page))
1152	__dec_zone_page_state(page,
1153	NR_ANON_TRANSPARENT_HUGEPAGES);
1154	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1155	-hpage_nr_pages(page));
1156	} else {
1157	__dec_zone_page_state(page, NR_FILE_MAPPED);
1158	mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1159	mem_cgroup_end_update_page_stat(page, &locked, &flags);
1160	}
1161	if (unlikely(PageMlocked(page)))
1162	clear_page_mlock(page);
1163	/*
1164	* It would be tidy to reset the PageAnon mapping here,
1165	* but that might overwrite a racing page_add_anon_rmap
1166	* which increments mapcount after us but sets mapping
1167	* before us: so leave the reset to free_hot_cold_page,
1168	* and remember that it's only reliable while mapped.
1169	* Leaving it set also helps swapoff to reinstate ptes
1170	* faster for those pages still in swapcache.
1171	*/
1172	return;
1173	out:
1174	if (!anon)
1175	mem_cgroup_end_update_page_stat(page, &locked, &flags);
1176	}
1177
1178	/*
1179	* Subfunctions of try_to_unmap: try_to_unmap_one called
1180	* repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
1181	*/
1182	int try_to_unmap_one(struct page page, struct vm_area_struct vma,
1183	unsigned long address, enum ttu_flags flags)
1184	{
1185	struct mm_struct *mm = vma->vm_mm;
1186	pte_t *pte;
1187	pte_t pteval;
1188	spinlock_t *ptl;
1189	int ret = SWAP_AGAIN;
1190
1191	pte = page_check_address(page, mm, address, &ptl, 0);
1192	if (!pte)
1193	goto out;
1194
1195	/*
1196	* If the page is mlock()d, we cannot swap it out.
1197	* If it's recently referenced (perhaps page_referenced
1198	* skipped over this mm) then we should reactivate it.
1199	*/
1200	if (!(flags & TTU_IGNORE_MLOCK)) {
1201	if (vma->vm_flags & VM_LOCKED)
1202	goto out_mlock;
1203
1204	if (TTU_ACTION(flags) == TTU_MUNLOCK)
1205	goto out_unmap;
1206	}
1207	if (!(flags & TTU_IGNORE_ACCESS)) {
1208	if (ptep_clear_flush_young_notify(vma, address, pte)) {
1209	ret = SWAP_FAIL;
1210	goto out_unmap;
1211	}
1212	}
1213
1214	/* Nuke the page table entry. */
1215	flush_cache_page(vma, address, page_to_pfn(page));
1216	pteval = ptep_clear_flush(vma, address, pte);
1217
1218	/* Move the dirty bit to the physical page now the pte is gone. */
1219	if (pte_dirty(pteval))
1220	set_page_dirty(page);
1221
1222	/* Update high watermark before we lower rss */
1223	update_hiwater_rss(mm);
1224
1225	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1226	if (!PageHuge(page)) {
1227	if (PageAnon(page))
1228	dec_mm_counter(mm, MM_ANONPAGES);
1229	else
1230	dec_mm_counter(mm, MM_FILEPAGES);
1231	}
1232	set_pte_at(mm, address, pte,
1233	swp_entry_to_pte(make_hwpoison_entry(page)));
1234	} else if (PageAnon(page)) {
1235	swp_entry_t entry = { .val = page_private(page) };
1236	pte_t swp_pte;
1237
1238	if (PageSwapCache(page)) {
1239	/*
1240	* Store the swap location in the pte.
1241	* See handle_pte_fault() ...
1242	*/
1243	if (swap_duplicate(entry) < 0) {
1244	set_pte_at(mm, address, pte, pteval);
1245	ret = SWAP_FAIL;
1246	goto out_unmap;
1247	}
1248	if (list_empty(&mm->mmlist)) {
1249	spin_lock(&mmlist_lock);
1250	if (list_empty(&mm->mmlist))
1251	list_add(&mm->mmlist, &init_mm.mmlist);
1252	spin_unlock(&mmlist_lock);
1253	}
1254	dec_mm_counter(mm, MM_ANONPAGES);
1255	inc_mm_counter(mm, MM_SWAPENTS);
1256	} else if (IS_ENABLED(CONFIG_MIGRATION)) {
1257	/*
1258	* Store the pfn of the page in a special migration
1259	* pte. do_swap_page() will wait until the migration
1260	* pte is removed and then restart fault handling.
1261	*/
1262	BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1263	entry = make_migration_entry(page, pte_write(pteval));
1264	}
1265	swp_pte = swp_entry_to_pte(entry);
1266	if (pte_soft_dirty(pteval))
1267	swp_pte = pte_swp_mksoft_dirty(swp_pte);
1268	set_pte_at(mm, address, pte, swp_pte);
1269	BUG_ON(pte_file(*pte));
1270	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
1271	(TTU_ACTION(flags) == TTU_MIGRATION)) {
1272	/* Establish migration entry for a file page */
1273	swp_entry_t entry;
1274	entry = make_migration_entry(page, pte_write(pteval));
1275	set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1276	} else
1277	dec_mm_counter(mm, MM_FILEPAGES);
1278
1279	page_remove_rmap(page);
1280	page_cache_release(page);
1281
1282	out_unmap:
1283	pte_unmap_unlock(pte, ptl);
1284	if (ret != SWAP_FAIL)
1285	mmu_notifier_invalidate_page(mm, address);
1286	out:
1287	return ret;
1288
1289	out_mlock:
1290	pte_unmap_unlock(pte, ptl);
1291
1292
1293	/*
1294	* We need mmap_sem locking, Otherwise VM_LOCKED check makes
1295	* unstable result and race. Plus, We can't wait here because
1296	* we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
1297	* if trylock failed, the page remain in evictable lru and later
1298	* vmscan could retry to move the page to unevictable lru if the
1299	* page is actually mlocked.
1300	*/
1301	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1302	if (vma->vm_flags & VM_LOCKED) {
1303	mlock_vma_page(page);
1304	ret = SWAP_MLOCK;
1305	}
1306	up_read(&vma->vm_mm->mmap_sem);
1307	}
1308	return ret;
1309	}
1310
1311	/*
1312	* objrmap doesn't work for nonlinear VMAs because the assumption that
1313	* offset-into-file correlates with offset-into-virtual-addresses does not hold.
1314	* Consequently, given a particular page and its ->index, we cannot locate the
1315	* ptes which are mapping that page without an exhaustive linear search.
1316	*
1317	* So what this code does is a mini "virtual scan" of each nonlinear VMA which
1318	* maps the file to which the target page belongs. The ->vm_private_data field
1319	* holds the current cursor into that scan. Successive searches will circulate
1320	* around the vma's virtual address space.
1321	*
1322	* So as more replacement pressure is applied to the pages in a nonlinear VMA,
1323	* more scanning pressure is placed against them as well. Eventually pages
1324	* will become fully unmapped and are eligible for eviction.
1325	*
1326	* For very sparsely populated VMAs this is a little inefficient - chances are
1327	* there there won't be many ptes located within the scan cluster. In this case
1328	* maybe we could scan further - to the end of the pte page, perhaps.
1329	*
1330	* Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1331	* acquire it without blocking. If vma locked, mlock the pages in the cluster,
1332	* rather than unmapping them. If we encounter the "check_page" that vmscan is
1333	* trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1334	*/
1335	#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1336	#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1337
1338	static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1339	struct vm_area_struct vma, struct page check_page)
1340	{
1341	struct mm_struct *mm = vma->vm_mm;
1342	pmd_t *pmd;
1343	pte_t *pte;
1344	pte_t pteval;
1345	spinlock_t *ptl;
1346	struct page *page;
1347	unsigned long address;
1348	unsigned long mmun_start; /* For mmu_notifiers */
1349	unsigned long mmun_end; /* For mmu_notifiers */
1350	unsigned long end;
1351	int ret = SWAP_AGAIN;
1352	int locked_vma = 0;
1353
1354	address = (vma->vm_start + cursor) & CLUSTER_MASK;
1355	end = address + CLUSTER_SIZE;
1356	if (address < vma->vm_start)
1357	address = vma->vm_start;
1358	if (end > vma->vm_end)
1359	end = vma->vm_end;
1360
1361	pmd = mm_find_pmd(mm, address);
1362	if (!pmd)
1363	return ret;
1364
1365	mmun_start = address;
1366	mmun_end = end;
1367	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1368
1369	/*
1370	* If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1371	* keep the sem while scanning the cluster for mlocking pages.
1372	*/
1373	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1374	locked_vma = (vma->vm_flags & VM_LOCKED);
1375	if (!locked_vma)
1376	up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1377	}
1378
1379	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1380
1381	/* Update high watermark before we lower rss */
1382	update_hiwater_rss(mm);
1383
1384	for (; address < end; pte++, address += PAGE_SIZE) {
1385	if (!pte_present(*pte))
1386	continue;
1387	page = vm_normal_page(vma, address, *pte);
1388	BUG_ON(!page \|\| PageAnon(page));
1389
1390	if (locked_vma) {
1391	mlock_vma_page(page); /* no-op if already mlocked */
1392	if (page == check_page)
1393	ret = SWAP_MLOCK;
1394	continue; /* don't unmap */
1395	}
1396
1397	if (ptep_clear_flush_young_notify(vma, address, pte))
1398	continue;
1399
1400	/* Nuke the page table entry. */
1401	flush_cache_page(vma, address, pte_pfn(*pte));
1402	pteval = ptep_clear_flush(vma, address, pte);
1403
1404	/* If nonlinear, store the file page offset in the pte. */
1405	if (page->index != linear_page_index(vma, address)) {
1406	pte_t ptfile = pgoff_to_pte(page->index);
1407	if (pte_soft_dirty(pteval))
1408	pte_file_mksoft_dirty(ptfile);
1409	set_pte_at(mm, address, pte, ptfile);
1410	}
1411
1412	/* Move the dirty bit to the physical page now the pte is gone. */
1413	if (pte_dirty(pteval))
1414	set_page_dirty(page);
1415
1416	page_remove_rmap(page);
1417	page_cache_release(page);
1418	dec_mm_counter(mm, MM_FILEPAGES);
1419	(*mapcount)--;
1420	}
1421	pte_unmap_unlock(pte - 1, ptl);
1422	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1423	if (locked_vma)
1424	up_read(&vma->vm_mm->mmap_sem);
1425	return ret;
1426	}
1427
1428	bool is_vma_temporary_stack(struct vm_area_struct *vma)
1429	{
1430	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN \| VM_GROWSUP);
1431
1432	if (!maybe_stack)
1433	return false;
1434
1435	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1436	VM_STACK_INCOMPLETE_SETUP)
1437	return true;
1438
1439	return false;
1440	}
1441
1442	/**
1443	* try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1444	* rmap method
1445	* @page: the page to unmap/unlock
1446	* @flags: action and flags
1447	*
1448	* Find all the mappings of a page using the mapping pointer and the vma chains
1449	* contained in the anon_vma struct it points to.
1450	*
1451	* This function is only called from try_to_unmap/try_to_munlock for
1452	* anonymous pages.
1453	* When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1454	* where the page was found will be held for write. So, we won't recheck
1455	* vm_flags for that VMA. That should be OK, because that vma shouldn't be
1456	* 'LOCKED.
1457	*/
1458	static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1459	{
1460	struct anon_vma *anon_vma;
1461	pgoff_t pgoff;
1462	struct anon_vma_chain *avc;
1463	int ret = SWAP_AGAIN;
1464
1465	anon_vma = page_lock_anon_vma_read(page);
1466	if (!anon_vma)
1467	return ret;
1468
1469	pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1470	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1471	struct vm_area_struct *vma = avc->vma;
1472	unsigned long address;
1473
1474	/*
1475	* During exec, a temporary VMA is setup and later moved.
1476	* The VMA is moved under the anon_vma lock but not the
1477	* page tables leading to a race where migration cannot
1478	* find the migration ptes. Rather than increasing the
1479	* locking requirements of exec(), migration skips
1480	* temporary VMAs until after exec() completes.
1481	*/
1482	if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1483	is_vma_temporary_stack(vma))
1484	continue;
1485
1486	address = vma_address(page, vma);
1487	ret = try_to_unmap_one(page, vma, address, flags);
1488	if (ret != SWAP_AGAIN \|\| !page_mapped(page))
1489	break;
1490	}
1491
1492	page_unlock_anon_vma_read(anon_vma);
1493	return ret;
1494	}
1495
1496	/**
1497	* try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1498	* @page: the page to unmap/unlock
1499	* @flags: action and flags
1500	*
1501	* Find all the mappings of a page using the mapping pointer and the vma chains
1502	* contained in the address_space struct it points to.
1503	*
1504	* This function is only called from try_to_unmap/try_to_munlock for
1505	* object-based pages.
1506	* When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1507	* where the page was found will be held for write. So, we won't recheck
1508	* vm_flags for that VMA. That should be OK, because that vma shouldn't be
1509	* 'LOCKED.
1510	*/
1511	static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1512	{
1513	struct address_space *mapping = page->mapping;
1514	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1515	struct vm_area_struct *vma;
1516	int ret = SWAP_AGAIN;
1517	unsigned long cursor;
1518	unsigned long max_nl_cursor = 0;
1519	unsigned long max_nl_size = 0;
1520	unsigned int mapcount;
1521
1522	if (PageHuge(page))
1523	pgoff = page->index << compound_order(page);
1524
1525	mutex_lock(&mapping->i_mmap_mutex);
1526	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1527	unsigned long address = vma_address(page, vma);
1528	ret = try_to_unmap_one(page, vma, address, flags);
1529	if (ret != SWAP_AGAIN \|\| !page_mapped(page))
1530	goto out;
1531	}
1532
1533	if (list_empty(&mapping->i_mmap_nonlinear))
1534	goto out;
1535
1536	/*
1537	* We don't bother to try to find the munlocked page in nonlinears.
1538	* It's costly. Instead, later, page reclaim logic may call
1539	* try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1540	*/
1541	if (TTU_ACTION(flags) == TTU_MUNLOCK)
1542	goto out;
1543
1544	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1545	shared.nonlinear) {
1546	cursor = (unsigned long) vma->vm_private_data;
1547	if (cursor > max_nl_cursor)
1548	max_nl_cursor = cursor;
1549	cursor = vma->vm_end - vma->vm_start;
1550	if (cursor > max_nl_size)
1551	max_nl_size = cursor;
1552	}
1553
1554	if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1555	ret = SWAP_FAIL;
1556	goto out;
1557	}
1558
1559	/*
1560	* We don't try to search for this page in the nonlinear vmas,
1561	* and page_referenced wouldn't have found it anyway. Instead
1562	* just walk the nonlinear vmas trying to age and unmap some.
1563	* The mapcount of the page we came in with is irrelevant,
1564	* but even so use it as a guide to how hard we should try?
1565	*/
1566	mapcount = page_mapcount(page);
1567	if (!mapcount)
1568	goto out;
1569	cond_resched();
1570
1571	max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1572	if (max_nl_cursor == 0)
1573	max_nl_cursor = CLUSTER_SIZE;
1574
1575	do {
1576	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1577	shared.nonlinear) {
1578	cursor = (unsigned long) vma->vm_private_data;
1579	while ( cursor < max_nl_cursor &&
1580	cursor < vma->vm_end - vma->vm_start) {
1581	if (try_to_unmap_cluster(cursor, &mapcount,
1582	vma, page) == SWAP_MLOCK)
1583	ret = SWAP_MLOCK;
1584	cursor += CLUSTER_SIZE;
1585	vma->vm_private_data = (void *) cursor;
1586	if ((int)mapcount <= 0)
1587	goto out;
1588	}
1589	vma->vm_private_data = (void *) max_nl_cursor;
1590	}
1591	cond_resched();
1592	max_nl_cursor += CLUSTER_SIZE;
1593	} while (max_nl_cursor <= max_nl_size);
1594
1595	/*
1596	* Don't loop forever (perhaps all the remaining pages are
1597	* in locked vmas). Reset cursor on all unreserved nonlinear
1598	* vmas, now forgetting on which ones it had fallen behind.
1599	*/
1600	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
1601	vma->vm_private_data = NULL;
1602	out:
1603	mutex_unlock(&mapping->i_mmap_mutex);
1604	return ret;
1605	}
1606
1607	/**
1608	* try_to_unmap - try to remove all page table mappings to a page
1609	* @page: the page to get unmapped
1610	* @flags: action and flags
1611	*
1612	* Tries to remove all the page table entries which are mapping this
1613	* page, used in the pageout path. Caller must hold the page lock.
1614	* Return values are:
1615	*
1616	* SWAP_SUCCESS - we succeeded in removing all mappings
1617	* SWAP_AGAIN - we missed a mapping, try again later
1618	* SWAP_FAIL - the page is unswappable
1619	* SWAP_MLOCK - page is mlocked.
1620	*/
1621	int try_to_unmap(struct page *page, enum ttu_flags flags)
1622	{
1623	int ret;
1624
1625	BUG_ON(!PageLocked(page));
1626	VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1627
1628	if (unlikely(PageKsm(page)))
1629	ret = try_to_unmap_ksm(page, flags);
1630	else if (PageAnon(page))
1631	ret = try_to_unmap_anon(page, flags);
1632	else
1633	ret = try_to_unmap_file(page, flags);
1634	if (ret != SWAP_MLOCK && !page_mapped(page))
1635	ret = SWAP_SUCCESS;
1636	return ret;
1637	}
1638
1639	/**
1640	* try_to_munlock - try to munlock a page
1641	* @page: the page to be munlocked
1642	*
1643	* Called from munlock code. Checks all of the VMAs mapping the page
1644	* to make sure nobody else has this page mlocked. The page will be
1645	* returned with PG_mlocked cleared if no other vmas have it mlocked.
1646	*
1647	* Return values are:
1648	*
1649	* SWAP_AGAIN - no vma is holding page mlocked, or,
1650	* SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1651	* SWAP_FAIL - page cannot be located at present
1652	* SWAP_MLOCK - page is now mlocked.
1653	*/
1654	int try_to_munlock(struct page *page)
1655	{
1656	VM_BUG_ON(!PageLocked(page) \|\| PageLRU(page));
1657
1658	if (unlikely(PageKsm(page)))
1659	return try_to_unmap_ksm(page, TTU_MUNLOCK);
1660	else if (PageAnon(page))
1661	return try_to_unmap_anon(page, TTU_MUNLOCK);
1662	else
1663	return try_to_unmap_file(page, TTU_MUNLOCK);
1664	}
1665
1666	void __put_anon_vma(struct anon_vma *anon_vma)
1667	{
1668	struct anon_vma *root = anon_vma->root;
1669
1670	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1671	anon_vma_free(root);
1672
1673	anon_vma_free(anon_vma);
1674	}
1675
1676	#ifdef CONFIG_MIGRATION
1677	/*
1678	* rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1679	* Called by migrate.c to remove migration ptes, but might be used more later.
1680	*/
1681	static int rmap_walk_anon(struct page page, int (rmap_one)(struct page *,
1682	struct vm_area_struct , unsigned long, void ), void *arg)
1683	{
1684	struct anon_vma *anon_vma;
1685	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1686	struct anon_vma_chain *avc;
1687	int ret = SWAP_AGAIN;
1688
1689	/*
1690	* Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1691	* because that depends on page_mapped(); but not all its usages
1692	* are holding mmap_sem. Users without mmap_sem are required to
1693	* take a reference count to prevent the anon_vma disappearing
1694	*/
1695	anon_vma = page_anon_vma(page);
1696	if (!anon_vma)
1697	return ret;
1698	anon_vma_lock_read(anon_vma);
1699	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1700	struct vm_area_struct *vma = avc->vma;
1701	unsigned long address = vma_address(page, vma);
1702	ret = rmap_one(page, vma, address, arg);
1703	if (ret != SWAP_AGAIN)
1704	break;
1705	}
1706	anon_vma_unlock_read(anon_vma);
1707	return ret;
1708	}
1709
1710	static int rmap_walk_file(struct page page, int (rmap_one)(struct page *,
1711	struct vm_area_struct , unsigned long, void ), void *arg)
1712	{
1713	struct address_space *mapping = page->mapping;
1714	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1715	struct vm_area_struct *vma;
1716	int ret = SWAP_AGAIN;
1717
1718	if (!mapping)
1719	return ret;
1720	mutex_lock(&mapping->i_mmap_mutex);
1721	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1722	unsigned long address = vma_address(page, vma);
1723	ret = rmap_one(page, vma, address, arg);
1724	if (ret != SWAP_AGAIN)
1725	break;
1726	}
1727	/*
1728	* No nonlinear handling: being always shared, nonlinear vmas
1729	* never contain migration ptes. Decide what to do about this
1730	* limitation to linear when we need rmap_walk() on nonlinear.
1731	*/
1732	mutex_unlock(&mapping->i_mmap_mutex);
1733	return ret;
1734	}
1735
1736	int rmap_walk(struct page page, int (rmap_one)(struct page *,
1737	struct vm_area_struct , unsigned long, void ), void *arg)
1738	{
1739	VM_BUG_ON(!PageLocked(page));
1740
1741	if (unlikely(PageKsm(page)))
1742	return rmap_walk_ksm(page, rmap_one, arg);
1743	else if (PageAnon(page))
1744	return rmap_walk_anon(page, rmap_one, arg);
1745	else
1746	return rmap_walk_file(page, rmap_one, arg);
1747	}
1748	#endif /* CONFIG_MIGRATION */
1749
1750	#ifdef CONFIG_HUGETLB_PAGE
1751	/*
1752	* The following three functions are for anonymous (private mapped) hugepages.
1753	* Unlike common anonymous pages, anonymous hugepages have no accounting code
1754	* and no lru code, because we handle hugepages differently from common pages.
1755	*/
1756	static void __hugepage_set_anon_rmap(struct page *page,
1757	struct vm_area_struct *vma, unsigned long address, int exclusive)
1758	{
1759	struct anon_vma *anon_vma = vma->anon_vma;
1760
1761	BUG_ON(!anon_vma);
1762
1763	if (PageAnon(page))
1764	return;
1765	if (!exclusive)
1766	anon_vma = anon_vma->root;
1767
1768	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1769	page->mapping = (struct address_space *) anon_vma;
1770	page->index = linear_page_index(vma, address);
1771	}
1772
1773	void hugepage_add_anon_rmap(struct page *page,
1774	struct vm_area_struct *vma, unsigned long address)
1775	{
1776	struct anon_vma *anon_vma = vma->anon_vma;
1777	int first;
1778
1779	BUG_ON(!PageLocked(page));
1780	BUG_ON(!anon_vma);
1781	/* address might be in next vma when migration races vma_adjust */
1782	first = atomic_inc_and_test(&page->_mapcount);
1783	if (first)
1784	__hugepage_set_anon_rmap(page, vma, address, 0);
1785	}
1786
1787	void hugepage_add_new_anon_rmap(struct page *page,
1788	struct vm_area_struct *vma, unsigned long address)
1789	{
1790	BUG_ON(address < vma->vm_start \|\| address >= vma->vm_end);
1791	atomic_set(&page->_mapcount, 0);
1792	__hugepage_set_anon_rmap(page, vma, address, 1);
1793	}
1794	#endif /* CONFIG_HUGETLB_PAGE */
1795

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jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9

Kernel

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Root/mm/rmap.c

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