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Root/mm/migrate.c

1	/*
2	* Memory Migration functionality - linux/mm/migration.c
3	*
4	* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
5	*
6	* Page migration was first developed in the context of the memory hotplug
7	* project. The main authors of the migration code are:
8	*
9	* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10	* Hirokazu Takahashi <taka@valinux.co.jp>
11	* Dave Hansen <haveblue@us.ibm.com>
12	* Christoph Lameter
13	*/
14
15	#include <linux/migrate.h>
16	#include <linux/export.h>
17	#include <linux/swap.h>
18	#include <linux/swapops.h>
19	#include <linux/pagemap.h>
20	#include <linux/buffer_head.h>
21	#include <linux/mm_inline.h>
22	#include <linux/nsproxy.h>
23	#include <linux/pagevec.h>
24	#include <linux/ksm.h>
25	#include <linux/rmap.h>
26	#include <linux/topology.h>
27	#include <linux/cpu.h>
28	#include <linux/cpuset.h>
29	#include <linux/writeback.h>
30	#include <linux/mempolicy.h>
31	#include <linux/vmalloc.h>
32	#include <linux/security.h>
33	#include <linux/memcontrol.h>
34	#include <linux/syscalls.h>
35	#include <linux/hugetlb.h>
36	#include <linux/hugetlb_cgroup.h>
37	#include <linux/gfp.h>
38	#include <linux/balloon_compaction.h>
39
40	#include <asm/tlbflush.h>
41
42	#define CREATE_TRACE_POINTS
43	#include <trace/events/migrate.h>
44
45	#include "internal.h"
46
47	/*
48	* migrate_prep() needs to be called before we start compiling a list of pages
49	* to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
50	* undesirable, use migrate_prep_local()
51	*/
52	int migrate_prep(void)
53	{
54	/*
55	* Clear the LRU lists so pages can be isolated.
56	* Note that pages may be moved off the LRU after we have
57	* drained them. Those pages will fail to migrate like other
58	* pages that may be busy.
59	*/
60	lru_add_drain_all();
61
62	return 0;
63	}
64
65	/* Do the necessary work of migrate_prep but not if it involves other CPUs */
66	int migrate_prep_local(void)
67	{
68	lru_add_drain();
69
70	return 0;
71	}
72
73	/*
74	* Add isolated pages on the list back to the LRU under page lock
75	* to avoid leaking evictable pages back onto unevictable list.
76	*/
77	void putback_lru_pages(struct list_head *l)
78	{
79	struct page *page;
80	struct page *page2;
81
82	list_for_each_entry_safe(page, page2, l, lru) {
83	list_del(&page->lru);
84	dec_zone_page_state(page, NR_ISOLATED_ANON +
85	page_is_file_cache(page));
86	putback_lru_page(page);
87	}
88	}
89
90	/*
91	* Put previously isolated pages back onto the appropriate lists
92	* from where they were once taken off for compaction/migration.
93	*
94	* This function shall be used instead of putback_lru_pages(),
95	* whenever the isolated pageset has been built by isolate_migratepages_range()
96	*/
97	void putback_movable_pages(struct list_head *l)
98	{
99	struct page *page;
100	struct page *page2;
101
102	list_for_each_entry_safe(page, page2, l, lru) {
103	if (unlikely(PageHuge(page))) {
104	putback_active_hugepage(page);
105	continue;
106	}
107	list_del(&page->lru);
108	dec_zone_page_state(page, NR_ISOLATED_ANON +
109	page_is_file_cache(page));
110	if (unlikely(isolated_balloon_page(page)))
111	balloon_page_putback(page);
112	else
113	putback_lru_page(page);
114	}
115	}
116
117	/*
118	* Restore a potential migration pte to a working pte entry
119	*/
120	static int remove_migration_pte(struct page new, struct vm_area_struct vma,
121	unsigned long addr, void *old)
122	{
123	struct mm_struct *mm = vma->vm_mm;
124	swp_entry_t entry;
125	pmd_t *pmd;
126	pte_t *ptep, pte;
127	spinlock_t *ptl;
128
129	if (unlikely(PageHuge(new))) {
130	ptep = huge_pte_offset(mm, addr);
131	if (!ptep)
132	goto out;
133	ptl = &mm->page_table_lock;
134	} else {
135	pmd = mm_find_pmd(mm, addr);
136	if (!pmd)
137	goto out;
138	if (pmd_trans_huge(*pmd))
139	goto out;
140
141	ptep = pte_offset_map(pmd, addr);
142
143	/*
144	* Peek to check is_swap_pte() before taking ptlock? No, we
145	* can race mremap's move_ptes(), which skips anon_vma lock.
146	*/
147
148	ptl = pte_lockptr(mm, pmd);
149	}
150
151	spin_lock(ptl);
152	pte = *ptep;
153	if (!is_swap_pte(pte))
154	goto unlock;
155
156	entry = pte_to_swp_entry(pte);
157
158	if (!is_migration_entry(entry) \|\|
159	migration_entry_to_page(entry) != old)
160	goto unlock;
161
162	get_page(new);
163	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
164	if (pte_swp_soft_dirty(*ptep))
165	pte = pte_mksoft_dirty(pte);
166	if (is_write_migration_entry(entry))
167	pte = pte_mkwrite(pte);
168	#ifdef CONFIG_HUGETLB_PAGE
169	if (PageHuge(new)) {
170	pte = pte_mkhuge(pte);
171	pte = arch_make_huge_pte(pte, vma, new, 0);
172	}
173	#endif
174	flush_dcache_page(new);
175	set_pte_at(mm, addr, ptep, pte);
176
177	if (PageHuge(new)) {
178	if (PageAnon(new))
179	hugepage_add_anon_rmap(new, vma, addr);
180	else
181	page_dup_rmap(new);
182	} else if (PageAnon(new))
183	page_add_anon_rmap(new, vma, addr);
184	else
185	page_add_file_rmap(new);
186
187	/* No need to invalidate - it was non-present before */
188	update_mmu_cache(vma, addr, ptep);
189	unlock:
190	pte_unmap_unlock(ptep, ptl);
191	out:
192	return SWAP_AGAIN;
193	}
194
195	/*
196	* Get rid of all migration entries and replace them by
197	* references to the indicated page.
198	*/
199	static void remove_migration_ptes(struct page old, struct page new)
200	{
201	rmap_walk(new, remove_migration_pte, old);
202	}
203
204	/*
205	* Something used the pte of a page under migration. We need to
206	* get to the page and wait until migration is finished.
207	* When we return from this function the fault will be retried.
208	*/
209	static void __migration_entry_wait(struct mm_struct mm, pte_t ptep,
210	spinlock_t *ptl)
211	{
212	pte_t pte;
213	swp_entry_t entry;
214	struct page *page;
215
216	spin_lock(ptl);
217	pte = *ptep;
218	if (!is_swap_pte(pte))
219	goto out;
220
221	entry = pte_to_swp_entry(pte);
222	if (!is_migration_entry(entry))
223	goto out;
224
225	page = migration_entry_to_page(entry);
226
227	/*
228	* Once radix-tree replacement of page migration started, page_count
229	* must be zero. And, we don't want to call wait_on_page_locked()
230	* against a page without get_page().
231	* So, we use get_page_unless_zero(), here. Even failed, page fault
232	* will occur again.
233	*/
234	if (!get_page_unless_zero(page))
235	goto out;
236	pte_unmap_unlock(ptep, ptl);
237	wait_on_page_locked(page);
238	put_page(page);
239	return;
240	out:
241	pte_unmap_unlock(ptep, ptl);
242	}
243
244	void migration_entry_wait(struct mm_struct mm, pmd_t pmd,
245	unsigned long address)
246	{
247	spinlock_t *ptl = pte_lockptr(mm, pmd);
248	pte_t *ptep = pte_offset_map(pmd, address);
249	__migration_entry_wait(mm, ptep, ptl);
250	}
251
252	void migration_entry_wait_huge(struct mm_struct mm, pte_t pte)
253	{
254	spinlock_t *ptl = &(mm)->page_table_lock;
255	__migration_entry_wait(mm, pte, ptl);
256	}
257
258	#ifdef CONFIG_BLOCK
259	/* Returns true if all buffers are successfully locked */
260	static bool buffer_migrate_lock_buffers(struct buffer_head *head,
261	enum migrate_mode mode)
262	{
263	struct buffer_head *bh = head;
264
265	/* Simple case, sync compaction */
266	if (mode != MIGRATE_ASYNC) {
267	do {
268	get_bh(bh);
269	lock_buffer(bh);
270	bh = bh->b_this_page;
271
272	} while (bh != head);
273
274	return true;
275	}
276
277	/* async case, we cannot block on lock_buffer so use trylock_buffer */
278	do {
279	get_bh(bh);
280	if (!trylock_buffer(bh)) {
281	/*
282	* We failed to lock the buffer and cannot stall in
283	* async migration. Release the taken locks
284	*/
285	struct buffer_head *failed_bh = bh;
286	put_bh(failed_bh);
287	bh = head;
288	while (bh != failed_bh) {
289	unlock_buffer(bh);
290	put_bh(bh);
291	bh = bh->b_this_page;
292	}
293	return false;
294	}
295
296	bh = bh->b_this_page;
297	} while (bh != head);
298	return true;
299	}
300	#else
301	static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
302	enum migrate_mode mode)
303	{
304	return true;
305	}
306	#endif /* CONFIG_BLOCK */
307
308	/*
309	* Replace the page in the mapping.
310	*
311	* The number of remaining references must be:
312	* 1 for anonymous pages without a mapping
313	* 2 for pages with a mapping
314	* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
315	*/
316	int migrate_page_move_mapping(struct address_space *mapping,
317	struct page newpage, struct page page,
318	struct buffer_head *head, enum migrate_mode mode)
319	{
320	int expected_count = 0;
321	void **pslot;
322
323	if (!mapping) {
324	/* Anonymous page without mapping */
325	if (page_count(page) != 1)
326	return -EAGAIN;
327	return MIGRATEPAGE_SUCCESS;
328	}
329
330	spin_lock_irq(&mapping->tree_lock);
331
332	pslot = radix_tree_lookup_slot(&mapping->page_tree,
333	page_index(page));
334
335	expected_count = 2 + page_has_private(page);
336	if (page_count(page) != expected_count \|\|
337	radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
338	spin_unlock_irq(&mapping->tree_lock);
339	return -EAGAIN;
340	}
341
342	if (!page_freeze_refs(page, expected_count)) {
343	spin_unlock_irq(&mapping->tree_lock);
344	return -EAGAIN;
345	}
346
347	/*
348	* In the async migration case of moving a page with buffers, lock the
349	* buffers using trylock before the mapping is moved. If the mapping
350	* was moved, we later failed to lock the buffers and could not move
351	* the mapping back due to an elevated page count, we would have to
352	* block waiting on other references to be dropped.
353	*/
354	if (mode == MIGRATE_ASYNC && head &&
355	!buffer_migrate_lock_buffers(head, mode)) {
356	page_unfreeze_refs(page, expected_count);
357	spin_unlock_irq(&mapping->tree_lock);
358	return -EAGAIN;
359	}
360
361	/*
362	* Now we know that no one else is looking at the page.
363	*/
364	get_page(newpage); /* add cache reference */
365	if (PageSwapCache(page)) {
366	SetPageSwapCache(newpage);
367	set_page_private(newpage, page_private(page));
368	}
369
370	radix_tree_replace_slot(pslot, newpage);
371
372	/*
373	* Drop cache reference from old page by unfreezing
374	* to one less reference.
375	* We know this isn't the last reference.
376	*/
377	page_unfreeze_refs(page, expected_count - 1);
378
379	/*
380	* If moved to a different zone then also account
381	* the page for that zone. Other VM counters will be
382	* taken care of when we establish references to the
383	* new page and drop references to the old page.
384	*
385	* Note that anonymous pages are accounted for
386	* via NR_FILE_PAGES and NR_ANON_PAGES if they
387	* are mapped to swap space.
388	*/
389	__dec_zone_page_state(page, NR_FILE_PAGES);
390	__inc_zone_page_state(newpage, NR_FILE_PAGES);
391	if (!PageSwapCache(page) && PageSwapBacked(page)) {
392	__dec_zone_page_state(page, NR_SHMEM);
393	__inc_zone_page_state(newpage, NR_SHMEM);
394	}
395	spin_unlock_irq(&mapping->tree_lock);
396
397	return MIGRATEPAGE_SUCCESS;
398	}
399
400	/*
401	* The expected number of remaining references is the same as that
402	* of migrate_page_move_mapping().
403	*/
404	int migrate_huge_page_move_mapping(struct address_space *mapping,
405	struct page newpage, struct page page)
406	{
407	int expected_count;
408	void **pslot;
409
410	if (!mapping) {
411	if (page_count(page) != 1)
412	return -EAGAIN;
413	return MIGRATEPAGE_SUCCESS;
414	}
415
416	spin_lock_irq(&mapping->tree_lock);
417
418	pslot = radix_tree_lookup_slot(&mapping->page_tree,
419	page_index(page));
420
421	expected_count = 2 + page_has_private(page);
422	if (page_count(page) != expected_count \|\|
423	radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
424	spin_unlock_irq(&mapping->tree_lock);
425	return -EAGAIN;
426	}
427
428	if (!page_freeze_refs(page, expected_count)) {
429	spin_unlock_irq(&mapping->tree_lock);
430	return -EAGAIN;
431	}
432
433	get_page(newpage);
434
435	radix_tree_replace_slot(pslot, newpage);
436
437	page_unfreeze_refs(page, expected_count - 1);
438
439	spin_unlock_irq(&mapping->tree_lock);
440	return MIGRATEPAGE_SUCCESS;
441	}
442
443	/*
444	* Copy the page to its new location
445	*/
446	void migrate_page_copy(struct page newpage, struct page page)
447	{
448	if (PageHuge(page) \|\| PageTransHuge(page))
449	copy_huge_page(newpage, page);
450	else
451	copy_highpage(newpage, page);
452
453	if (PageError(page))
454	SetPageError(newpage);
455	if (PageReferenced(page))
456	SetPageReferenced(newpage);
457	if (PageUptodate(page))
458	SetPageUptodate(newpage);
459	if (TestClearPageActive(page)) {
460	VM_BUG_ON(PageUnevictable(page));
461	SetPageActive(newpage);
462	} else if (TestClearPageUnevictable(page))
463	SetPageUnevictable(newpage);
464	if (PageChecked(page))
465	SetPageChecked(newpage);
466	if (PageMappedToDisk(page))
467	SetPageMappedToDisk(newpage);
468
469	if (PageDirty(page)) {
470	clear_page_dirty_for_io(page);
471	/*
472	* Want to mark the page and the radix tree as dirty, and
473	* redo the accounting that clear_page_dirty_for_io undid,
474	* but we can't use set_page_dirty because that function
475	* is actually a signal that all of the page has become dirty.
476	* Whereas only part of our page may be dirty.
477	*/
478	if (PageSwapBacked(page))
479	SetPageDirty(newpage);
480	else
481	__set_page_dirty_nobuffers(newpage);
482	}
483
484	mlock_migrate_page(newpage, page);
485	ksm_migrate_page(newpage, page);
486	/*
487	* Please do not reorder this without considering how mm/ksm.c's
488	* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
489	*/
490	ClearPageSwapCache(page);
491	ClearPagePrivate(page);
492	set_page_private(page, 0);
493
494	/*
495	* If any waiters have accumulated on the new page then
496	* wake them up.
497	*/
498	if (PageWriteback(newpage))
499	end_page_writeback(newpage);
500	}
501
502	/************************************************************
503	* Migration functions
504	***********************************************************/
505
506	/* Always fail migration. Used for mappings that are not movable */
507	int fail_migrate_page(struct address_space *mapping,
508	struct page newpage, struct page page)
509	{
510	return -EIO;
511	}
512	EXPORT_SYMBOL(fail_migrate_page);
513
514	/*
515	* Common logic to directly migrate a single page suitable for
516	* pages that do not use PagePrivate/PagePrivate2.
517	*
518	* Pages are locked upon entry and exit.
519	*/
520	int migrate_page(struct address_space *mapping,
521	struct page newpage, struct page page,
522	enum migrate_mode mode)
523	{
524	int rc;
525
526	BUG_ON(PageWriteback(page)); /* Writeback must be complete */
527
528	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
529
530	if (rc != MIGRATEPAGE_SUCCESS)
531	return rc;
532
533	migrate_page_copy(newpage, page);
534	return MIGRATEPAGE_SUCCESS;
535	}
536	EXPORT_SYMBOL(migrate_page);
537
538	#ifdef CONFIG_BLOCK
539	/*
540	* Migration function for pages with buffers. This function can only be used
541	* if the underlying filesystem guarantees that no other references to "page"
542	* exist.
543	*/
544	int buffer_migrate_page(struct address_space *mapping,
545	struct page newpage, struct page page, enum migrate_mode mode)
546	{
547	struct buffer_head bh, head;
548	int rc;
549
550	if (!page_has_buffers(page))
551	return migrate_page(mapping, newpage, page, mode);
552
553	head = page_buffers(page);
554
555	rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
556
557	if (rc != MIGRATEPAGE_SUCCESS)
558	return rc;
559
560	/*
561	* In the async case, migrate_page_move_mapping locked the buffers
562	* with an IRQ-safe spinlock held. In the sync case, the buffers
563	* need to be locked now
564	*/
565	if (mode != MIGRATE_ASYNC)
566	BUG_ON(!buffer_migrate_lock_buffers(head, mode));
567
568	ClearPagePrivate(page);
569	set_page_private(newpage, page_private(page));
570	set_page_private(page, 0);
571	put_page(page);
572	get_page(newpage);
573
574	bh = head;
575	do {
576	set_bh_page(bh, newpage, bh_offset(bh));
577	bh = bh->b_this_page;
578
579	} while (bh != head);
580
581	SetPagePrivate(newpage);
582
583	migrate_page_copy(newpage, page);
584
585	bh = head;
586	do {
587	unlock_buffer(bh);
588	put_bh(bh);
589	bh = bh->b_this_page;
590
591	} while (bh != head);
592
593	return MIGRATEPAGE_SUCCESS;
594	}
595	EXPORT_SYMBOL(buffer_migrate_page);
596	#endif
597
598	/*
599	* Writeback a page to clean the dirty state
600	*/
601	static int writeout(struct address_space mapping, struct page page)
602	{
603	struct writeback_control wbc = {
604	.sync_mode = WB_SYNC_NONE,
605	.nr_to_write = 1,
606	.range_start = 0,
607	.range_end = LLONG_MAX,
608	.for_reclaim = 1
609	};
610	int rc;
611
612	if (!mapping->a_ops->writepage)
613	/* No write method for the address space */
614	return -EINVAL;
615
616	if (!clear_page_dirty_for_io(page))
617	/* Someone else already triggered a write */
618	return -EAGAIN;
619
620	/*
621	* A dirty page may imply that the underlying filesystem has
622	* the page on some queue. So the page must be clean for
623	* migration. Writeout may mean we loose the lock and the
624	* page state is no longer what we checked for earlier.
625	* At this point we know that the migration attempt cannot
626	* be successful.
627	*/
628	remove_migration_ptes(page, page);
629
630	rc = mapping->a_ops->writepage(page, &wbc);
631
632	if (rc != AOP_WRITEPAGE_ACTIVATE)
633	/* unlocked. Relock */
634	lock_page(page);
635
636	return (rc < 0) ? -EIO : -EAGAIN;
637	}
638
639	/*
640	* Default handling if a filesystem does not provide a migration function.
641	*/
642	static int fallback_migrate_page(struct address_space *mapping,
643	struct page newpage, struct page page, enum migrate_mode mode)
644	{
645	if (PageDirty(page)) {
646	/* Only writeback pages in full synchronous migration */
647	if (mode != MIGRATE_SYNC)
648	return -EBUSY;
649	return writeout(mapping, page);
650	}
651
652	/*
653	* Buffers may be managed in a filesystem specific way.
654	* We must have no buffers or drop them.
655	*/
656	if (page_has_private(page) &&
657	!try_to_release_page(page, GFP_KERNEL))
658	return -EAGAIN;
659
660	return migrate_page(mapping, newpage, page, mode);
661	}
662
663	/*
664	* Move a page to a newly allocated page
665	* The page is locked and all ptes have been successfully removed.
666	*
667	* The new page will have replaced the old page if this function
668	* is successful.
669	*
670	* Return value:
671	* < 0 - error code
672	* MIGRATEPAGE_SUCCESS - success
673	*/
674	static int move_to_new_page(struct page newpage, struct page page,
675	int remap_swapcache, enum migrate_mode mode)
676	{
677	struct address_space *mapping;
678	int rc;
679
680	/*
681	* Block others from accessing the page when we get around to
682	* establishing additional references. We are the only one
683	* holding a reference to the new page at this point.
684	*/
685	if (!trylock_page(newpage))
686	BUG();
687
688	/* Prepare mapping for the new page.*/
689	newpage->index = page->index;
690	newpage->mapping = page->mapping;
691	if (PageSwapBacked(page))
692	SetPageSwapBacked(newpage);
693
694	mapping = page_mapping(page);
695	if (!mapping)
696	rc = migrate_page(mapping, newpage, page, mode);
697	else if (mapping->a_ops->migratepage)
698	/*
699	* Most pages have a mapping and most filesystems provide a
700	* migratepage callback. Anonymous pages are part of swap
701	* space which also has its own migratepage callback. This
702	* is the most common path for page migration.
703	*/
704	rc = mapping->a_ops->migratepage(mapping,
705	newpage, page, mode);
706	else
707	rc = fallback_migrate_page(mapping, newpage, page, mode);
708
709	if (rc != MIGRATEPAGE_SUCCESS) {
710	newpage->mapping = NULL;
711	} else {
712	if (remap_swapcache)
713	remove_migration_ptes(page, newpage);
714	page->mapping = NULL;
715	}
716
717	unlock_page(newpage);
718
719	return rc;
720	}
721
722	static int __unmap_and_move(struct page page, struct page newpage,
723	int force, enum migrate_mode mode)
724	{
725	int rc = -EAGAIN;
726	int remap_swapcache = 1;
727	struct mem_cgroup *mem;
728	struct anon_vma *anon_vma = NULL;
729
730	if (!trylock_page(page)) {
731	if (!force \|\| mode == MIGRATE_ASYNC)
732	goto out;
733
734	/*
735	* It's not safe for direct compaction to call lock_page.
736	* For example, during page readahead pages are added locked
737	* to the LRU. Later, when the IO completes the pages are
738	* marked uptodate and unlocked. However, the queueing
739	* could be merging multiple pages for one bio (e.g.
740	* mpage_readpages). If an allocation happens for the
741	* second or third page, the process can end up locking
742	* the same page twice and deadlocking. Rather than
743	* trying to be clever about what pages can be locked,
744	* avoid the use of lock_page for direct compaction
745	* altogether.
746	*/
747	if (current->flags & PF_MEMALLOC)
748	goto out;
749
750	lock_page(page);
751	}
752
753	/* charge against new page */
754	mem_cgroup_prepare_migration(page, newpage, &mem);
755
756	if (PageWriteback(page)) {
757	/*
758	* Only in the case of a full synchronous migration is it
759	* necessary to wait for PageWriteback. In the async case,
760	* the retry loop is too short and in the sync-light case,
761	* the overhead of stalling is too much
762	*/
763	if (mode != MIGRATE_SYNC) {
764	rc = -EBUSY;
765	goto uncharge;
766	}
767	if (!force)
768	goto uncharge;
769	wait_on_page_writeback(page);
770	}
771	/*
772	* By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
773	* we cannot notice that anon_vma is freed while we migrates a page.
774	* This get_anon_vma() delays freeing anon_vma pointer until the end
775	* of migration. File cache pages are no problem because of page_lock()
776	* File Caches may use write_page() or lock_page() in migration, then,
777	* just care Anon page here.
778	*/
779	if (PageAnon(page) && !PageKsm(page)) {
780	/*
781	* Only page_lock_anon_vma_read() understands the subtleties of
782	* getting a hold on an anon_vma from outside one of its mms.
783	*/
784	anon_vma = page_get_anon_vma(page);
785	if (anon_vma) {
786	/*
787	* Anon page
788	*/
789	} else if (PageSwapCache(page)) {
790	/*
791	* We cannot be sure that the anon_vma of an unmapped
792	* swapcache page is safe to use because we don't
793	* know in advance if the VMA that this page belonged
794	* to still exists. If the VMA and others sharing the
795	* data have been freed, then the anon_vma could
796	* already be invalid.
797	*
798	* To avoid this possibility, swapcache pages get
799	* migrated but are not remapped when migration
800	* completes
801	*/
802	remap_swapcache = 0;
803	} else {
804	goto uncharge;
805	}
806	}
807
808	if (unlikely(balloon_page_movable(page))) {
809	/*
810	* A ballooned page does not need any special attention from
811	* physical to virtual reverse mapping procedures.
812	* Skip any attempt to unmap PTEs or to remap swap cache,
813	* in order to avoid burning cycles at rmap level, and perform
814	* the page migration right away (proteced by page lock).
815	*/
816	rc = balloon_page_migrate(newpage, page, mode);
817	goto uncharge;
818	}
819
820	/*
821	* Corner case handling:
822	* 1. When a new swap-cache page is read into, it is added to the LRU
823	* and treated as swapcache but it has no rmap yet.
824	* Calling try_to_unmap() against a page->mapping==NULL page will
825	* trigger a BUG. So handle it here.
826	* 2. An orphaned page (see truncate_complete_page) might have
827	* fs-private metadata. The page can be picked up due to memory
828	* offlining. Everywhere else except page reclaim, the page is
829	* invisible to the vm, so the page can not be migrated. So try to
830	* free the metadata, so the page can be freed.
831	*/
832	if (!page->mapping) {
833	VM_BUG_ON(PageAnon(page));
834	if (page_has_private(page)) {
835	try_to_free_buffers(page);
836	goto uncharge;
837	}
838	goto skip_unmap;
839	}
840
841	/* Establish migration ptes or remove ptes */
842	try_to_unmap(page, TTU_MIGRATION\|TTU_IGNORE_MLOCK\|TTU_IGNORE_ACCESS);
843
844	skip_unmap:
845	if (!page_mapped(page))
846	rc = move_to_new_page(newpage, page, remap_swapcache, mode);
847
848	if (rc && remap_swapcache)
849	remove_migration_ptes(page, page);
850
851	/* Drop an anon_vma reference if we took one */
852	if (anon_vma)
853	put_anon_vma(anon_vma);
854
855	uncharge:
856	mem_cgroup_end_migration(mem, page, newpage,
857	(rc == MIGRATEPAGE_SUCCESS \|\|
858	rc == MIGRATEPAGE_BALLOON_SUCCESS));
859	unlock_page(page);
860	out:
861	return rc;
862	}
863
864	/*
865	* Obtain the lock on page, remove all ptes and migrate the page
866	* to the newly allocated page in newpage.
867	*/
868	static int unmap_and_move(new_page_t get_new_page, unsigned long private,
869	struct page *page, int force, enum migrate_mode mode)
870	{
871	int rc = 0;
872	int *result = NULL;
873	struct page *newpage = get_new_page(page, private, &result);
874
875	if (!newpage)
876	return -ENOMEM;
877
878	if (page_count(page) == 1) {
879	/* page was freed from under us. So we are done. */
880	goto out;
881	}
882
883	if (unlikely(PageTransHuge(page)))
884	if (unlikely(split_huge_page(page)))
885	goto out;
886
887	rc = __unmap_and_move(page, newpage, force, mode);
888
889	if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
890	/*
891	* A ballooned page has been migrated already.
892	* Now, it's the time to wrap-up counters,
893	* handle the page back to Buddy and return.
894	*/
895	dec_zone_page_state(page, NR_ISOLATED_ANON +
896	page_is_file_cache(page));
897	balloon_page_free(page);
898	return MIGRATEPAGE_SUCCESS;
899	}
900	out:
901	if (rc != -EAGAIN) {
902	/*
903	* A page that has been migrated has all references
904	* removed and will be freed. A page that has not been
905	* migrated will have kepts its references and be
906	* restored.
907	*/
908	list_del(&page->lru);
909	dec_zone_page_state(page, NR_ISOLATED_ANON +
910	page_is_file_cache(page));
911	putback_lru_page(page);
912	}
913	/*
914	* Move the new page to the LRU. If migration was not successful
915	* then this will free the page.
916	*/
917	putback_lru_page(newpage);
918	if (result) {
919	if (rc)
920	*result = rc;
921	else
922	*result = page_to_nid(newpage);
923	}
924	return rc;
925	}
926
927	/*
928	* Counterpart of unmap_and_move_page() for hugepage migration.
929	*
930	* This function doesn't wait the completion of hugepage I/O
931	* because there is no race between I/O and migration for hugepage.
932	* Note that currently hugepage I/O occurs only in direct I/O
933	* where no lock is held and PG_writeback is irrelevant,
934	* and writeback status of all subpages are counted in the reference
935	* count of the head page (i.e. if all subpages of a 2MB hugepage are
936	* under direct I/O, the reference of the head page is 512 and a bit more.)
937	* This means that when we try to migrate hugepage whose subpages are
938	* doing direct I/O, some references remain after try_to_unmap() and
939	* hugepage migration fails without data corruption.
940	*
941	* There is also no race when direct I/O is issued on the page under migration,
942	* because then pte is replaced with migration swap entry and direct I/O code
943	* will wait in the page fault for migration to complete.
944	*/
945	static int unmap_and_move_huge_page(new_page_t get_new_page,
946	unsigned long private, struct page *hpage,
947	int force, enum migrate_mode mode)
948	{
949	int rc = 0;
950	int *result = NULL;
951	struct page *new_hpage = get_new_page(hpage, private, &result);
952	struct anon_vma *anon_vma = NULL;
953
954	/*
955	* Movability of hugepages depends on architectures and hugepage size.
956	* This check is necessary because some callers of hugepage migration
957	* like soft offline and memory hotremove don't walk through page
958	* tables or check whether the hugepage is pmd-based or not before
959	* kicking migration.
960	*/
961	if (!hugepage_migration_support(page_hstate(hpage)))
962	return -ENOSYS;
963
964	if (!new_hpage)
965	return -ENOMEM;
966
967	rc = -EAGAIN;
968
969	if (!trylock_page(hpage)) {
970	if (!force \|\| mode != MIGRATE_SYNC)
971	goto out;
972	lock_page(hpage);
973	}
974
975	if (PageAnon(hpage))
976	anon_vma = page_get_anon_vma(hpage);
977
978	try_to_unmap(hpage, TTU_MIGRATION\|TTU_IGNORE_MLOCK\|TTU_IGNORE_ACCESS);
979
980	if (!page_mapped(hpage))
981	rc = move_to_new_page(new_hpage, hpage, 1, mode);
982
983	if (rc)
984	remove_migration_ptes(hpage, hpage);
985
986	if (anon_vma)
987	put_anon_vma(anon_vma);
988
989	if (!rc)
990	hugetlb_cgroup_migrate(hpage, new_hpage);
991
992	unlock_page(hpage);
993	out:
994	if (rc != -EAGAIN)
995	putback_active_hugepage(hpage);
996	put_page(new_hpage);
997	if (result) {
998	if (rc)
999	*result = rc;
1000	else
1001	*result = page_to_nid(new_hpage);
1002	}
1003	return rc;
1004	}
1005
1006	/*
1007	* migrate_pages - migrate the pages specified in a list, to the free pages
1008	* supplied as the target for the page migration
1009	*
1010	* @from: The list of pages to be migrated.
1011	* @get_new_page: The function used to allocate free pages to be used
1012	* as the target of the page migration.
1013	* @private: Private data to be passed on to get_new_page()
1014	* @mode: The migration mode that specifies the constraints for
1015	* page migration, if any.
1016	* @reason: The reason for page migration.
1017	*
1018	* The function returns after 10 attempts or if no pages are movable any more
1019	* because the list has become empty or no retryable pages exist any more.
1020	* The caller should call putback_lru_pages() to return pages to the LRU
1021	* or free list only if ret != 0.
1022	*
1023	* Returns the number of pages that were not migrated, or an error code.
1024	*/
1025	int migrate_pages(struct list_head *from, new_page_t get_new_page,
1026	unsigned long private, enum migrate_mode mode, int reason)
1027	{
1028	int retry = 1;
1029	int nr_failed = 0;
1030	int nr_succeeded = 0;
1031	int pass = 0;
1032	struct page *page;
1033	struct page *page2;
1034	int swapwrite = current->flags & PF_SWAPWRITE;
1035	int rc;
1036
1037	if (!swapwrite)
1038	current->flags \|= PF_SWAPWRITE;
1039
1040	for(pass = 0; pass < 10 && retry; pass++) {
1041	retry = 0;
1042
1043	list_for_each_entry_safe(page, page2, from, lru) {
1044	cond_resched();
1045
1046	if (PageHuge(page))
1047	rc = unmap_and_move_huge_page(get_new_page,
1048	private, page, pass > 2, mode);
1049	else
1050	rc = unmap_and_move(get_new_page, private,
1051	page, pass > 2, mode);
1052
1053	switch(rc) {
1054	case -ENOMEM:
1055	goto out;
1056	case -EAGAIN:
1057	retry++;
1058	break;
1059	case MIGRATEPAGE_SUCCESS:
1060	nr_succeeded++;
1061	break;
1062	default:
1063	/* Permanent failure */
1064	nr_failed++;
1065	break;
1066	}
1067	}
1068	}
1069	rc = nr_failed + retry;
1070	out:
1071	if (nr_succeeded)
1072	count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1073	if (nr_failed)
1074	count_vm_events(PGMIGRATE_FAIL, nr_failed);
1075	trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1076
1077	if (!swapwrite)
1078	current->flags &= ~PF_SWAPWRITE;
1079
1080	return rc;
1081	}
1082
1083	#ifdef CONFIG_NUMA
1084	/*
1085	* Move a list of individual pages
1086	*/
1087	struct page_to_node {
1088	unsigned long addr;
1089	struct page *page;
1090	int node;
1091	int status;
1092	};
1093
1094	static struct page new_page_node(struct page p, unsigned long private,
1095	int **result)
1096	{
1097	struct page_to_node pm = (struct page_to_node )private;
1098
1099	while (pm->node != MAX_NUMNODES && pm->page != p)
1100	pm++;
1101
1102	if (pm->node == MAX_NUMNODES)
1103	return NULL;
1104
1105	*result = &pm->status;
1106
1107	if (PageHuge(p))
1108	return alloc_huge_page_node(page_hstate(compound_head(p)),
1109	pm->node);
1110	else
1111	return alloc_pages_exact_node(pm->node,
1112	GFP_HIGHUSER_MOVABLE \| GFP_THISNODE, 0);
1113	}
1114
1115	/*
1116	* Move a set of pages as indicated in the pm array. The addr
1117	* field must be set to the virtual address of the page to be moved
1118	* and the node number must contain a valid target node.
1119	* The pm array ends with node = MAX_NUMNODES.
1120	*/
1121	static int do_move_page_to_node_array(struct mm_struct *mm,
1122	struct page_to_node *pm,
1123	int migrate_all)
1124	{
1125	int err;
1126	struct page_to_node *pp;
1127	LIST_HEAD(pagelist);
1128
1129	down_read(&mm->mmap_sem);
1130
1131	/*
1132	* Build a list of pages to migrate
1133	*/
1134	for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1135	struct vm_area_struct *vma;
1136	struct page *page;
1137
1138	err = -EFAULT;
1139	vma = find_vma(mm, pp->addr);
1140	if (!vma \|\| pp->addr < vma->vm_start \|\| !vma_migratable(vma))
1141	goto set_status;
1142
1143	page = follow_page(vma, pp->addr, FOLL_GET\|FOLL_SPLIT);
1144
1145	err = PTR_ERR(page);
1146	if (IS_ERR(page))
1147	goto set_status;
1148
1149	err = -ENOENT;
1150	if (!page)
1151	goto set_status;
1152
1153	/* Use PageReserved to check for zero page */
1154	if (PageReserved(page))
1155	goto put_and_set;
1156
1157	pp->page = page;
1158	err = page_to_nid(page);
1159
1160	if (err == pp->node)
1161	/*
1162	* Node already in the right place
1163	*/
1164	goto put_and_set;
1165
1166	err = -EACCES;
1167	if (page_mapcount(page) > 1 &&
1168	!migrate_all)
1169	goto put_and_set;
1170
1171	if (PageHuge(page)) {
1172	isolate_huge_page(page, &pagelist);
1173	goto put_and_set;
1174	}
1175
1176	err = isolate_lru_page(page);
1177	if (!err) {
1178	list_add_tail(&page->lru, &pagelist);
1179	inc_zone_page_state(page, NR_ISOLATED_ANON +
1180	page_is_file_cache(page));
1181	}
1182	put_and_set:
1183	/*
1184	* Either remove the duplicate refcount from
1185	* isolate_lru_page() or drop the page ref if it was
1186	* not isolated.
1187	*/
1188	put_page(page);
1189	set_status:
1190	pp->status = err;
1191	}
1192
1193	err = 0;
1194	if (!list_empty(&pagelist)) {
1195	err = migrate_pages(&pagelist, new_page_node,
1196	(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1197	if (err)
1198	putback_movable_pages(&pagelist);
1199	}
1200
1201	up_read(&mm->mmap_sem);
1202	return err;
1203	}
1204
1205	/*
1206	* Migrate an array of page address onto an array of nodes and fill
1207	* the corresponding array of status.
1208	*/
1209	static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1210	unsigned long nr_pages,
1211	const void __user * __user *pages,
1212	const int __user *nodes,
1213	int __user *status, int flags)
1214	{
1215	struct page_to_node *pm;
1216	unsigned long chunk_nr_pages;
1217	unsigned long chunk_start;
1218	int err;
1219
1220	err = -ENOMEM;
1221	pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1222	if (!pm)
1223	goto out;
1224
1225	migrate_prep();
1226
1227	/*
1228	* Store a chunk of page_to_node array in a page,
1229	* but keep the last one as a marker
1230	*/
1231	chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1232
1233	for (chunk_start = 0;
1234	chunk_start < nr_pages;
1235	chunk_start += chunk_nr_pages) {
1236	int j;
1237
1238	if (chunk_start + chunk_nr_pages > nr_pages)
1239	chunk_nr_pages = nr_pages - chunk_start;
1240
1241	/* fill the chunk pm with addrs and nodes from user-space */
1242	for (j = 0; j < chunk_nr_pages; j++) {
1243	const void __user *p;
1244	int node;
1245
1246	err = -EFAULT;
1247	if (get_user(p, pages + j + chunk_start))
1248	goto out_pm;
1249	pm[j].addr = (unsigned long) p;
1250
1251	if (get_user(node, nodes + j + chunk_start))
1252	goto out_pm;
1253
1254	err = -ENODEV;
1255	if (node < 0 \|\| node >= MAX_NUMNODES)
1256	goto out_pm;
1257
1258	if (!node_state(node, N_MEMORY))
1259	goto out_pm;
1260
1261	err = -EACCES;
1262	if (!node_isset(node, task_nodes))
1263	goto out_pm;
1264
1265	pm[j].node = node;
1266	}
1267
1268	/* End marker for this chunk */
1269	pm[chunk_nr_pages].node = MAX_NUMNODES;
1270
1271	/* Migrate this chunk */
1272	err = do_move_page_to_node_array(mm, pm,
1273	flags & MPOL_MF_MOVE_ALL);
1274	if (err < 0)
1275	goto out_pm;
1276
1277	/* Return status information */
1278	for (j = 0; j < chunk_nr_pages; j++)
1279	if (put_user(pm[j].status, status + j + chunk_start)) {
1280	err = -EFAULT;
1281	goto out_pm;
1282	}
1283	}
1284	err = 0;
1285
1286	out_pm:
1287	free_page((unsigned long)pm);
1288	out:
1289	return err;
1290	}
1291
1292	/*
1293	* Determine the nodes of an array of pages and store it in an array of status.
1294	*/
1295	static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1296	const void __user *pages, int status)
1297	{
1298	unsigned long i;
1299
1300	down_read(&mm->mmap_sem);
1301
1302	for (i = 0; i < nr_pages; i++) {
1303	unsigned long addr = (unsigned long)(*pages);
1304	struct vm_area_struct *vma;
1305	struct page *page;
1306	int err = -EFAULT;
1307
1308	vma = find_vma(mm, addr);
1309	if (!vma \|\| addr < vma->vm_start)
1310	goto set_status;
1311
1312	page = follow_page(vma, addr, 0);
1313
1314	err = PTR_ERR(page);
1315	if (IS_ERR(page))
1316	goto set_status;
1317
1318	err = -ENOENT;
1319	/* Use PageReserved to check for zero page */
1320	if (!page \|\| PageReserved(page))
1321	goto set_status;
1322
1323	err = page_to_nid(page);
1324	set_status:
1325	*status = err;
1326
1327	pages++;
1328	status++;
1329	}
1330
1331	up_read(&mm->mmap_sem);
1332	}
1333
1334	/*
1335	* Determine the nodes of a user array of pages and store it in
1336	* a user array of status.
1337	*/
1338	static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1339	const void __user * __user *pages,
1340	int __user *status)
1341	{
1342	#define DO_PAGES_STAT_CHUNK_NR 16
1343	const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1344	int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1345
1346	while (nr_pages) {
1347	unsigned long chunk_nr;
1348
1349	chunk_nr = nr_pages;
1350	if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1351	chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1352
1353	if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1354	break;
1355
1356	do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1357
1358	if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1359	break;
1360
1361	pages += chunk_nr;
1362	status += chunk_nr;
1363	nr_pages -= chunk_nr;
1364	}
1365	return nr_pages ? -EFAULT : 0;
1366	}
1367
1368	/*
1369	* Move a list of pages in the address space of the currently executing
1370	* process.
1371	*/
1372	SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1373	const void __user * __user *, pages,
1374	const int __user *, nodes,
1375	int __user *, status, int, flags)
1376	{
1377	const struct cred cred = current_cred(), tcred;
1378	struct task_struct *task;
1379	struct mm_struct *mm;
1380	int err;
1381	nodemask_t task_nodes;
1382
1383	/* Check flags */
1384	if (flags & ~(MPOL_MF_MOVE\|MPOL_MF_MOVE_ALL))
1385	return -EINVAL;
1386
1387	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1388	return -EPERM;
1389
1390	/* Find the mm_struct */
1391	rcu_read_lock();
1392	task = pid ? find_task_by_vpid(pid) : current;
1393	if (!task) {
1394	rcu_read_unlock();
1395	return -ESRCH;
1396	}
1397	get_task_struct(task);
1398
1399	/*
1400	* Check if this process has the right to modify the specified
1401	* process. The right exists if the process has administrative
1402	* capabilities, superuser privileges or the same
1403	* userid as the target process.
1404	*/
1405	tcred = __task_cred(task);
1406	if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1407	!uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
1408	!capable(CAP_SYS_NICE)) {
1409	rcu_read_unlock();
1410	err = -EPERM;
1411	goto out;
1412	}
1413	rcu_read_unlock();
1414
1415	err = security_task_movememory(task);
1416	if (err)
1417	goto out;
1418
1419	task_nodes = cpuset_mems_allowed(task);
1420	mm = get_task_mm(task);
1421	put_task_struct(task);
1422
1423	if (!mm)
1424	return -EINVAL;
1425
1426	if (nodes)
1427	err = do_pages_move(mm, task_nodes, nr_pages, pages,
1428	nodes, status, flags);
1429	else
1430	err = do_pages_stat(mm, nr_pages, pages, status);
1431
1432	mmput(mm);
1433	return err;
1434
1435	out:
1436	put_task_struct(task);
1437	return err;
1438	}
1439
1440	/*
1441	* Call migration functions in the vma_ops that may prepare
1442	* memory in a vm for migration. migration functions may perform
1443	* the migration for vmas that do not have an underlying page struct.
1444	*/
1445	int migrate_vmas(struct mm_struct mm, const nodemask_t to,
1446	const nodemask_t *from, unsigned long flags)
1447	{
1448	struct vm_area_struct *vma;
1449	int err = 0;
1450
1451	for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1452	if (vma->vm_ops && vma->vm_ops->migrate) {
1453	err = vma->vm_ops->migrate(vma, to, from, flags);
1454	if (err)
1455	break;
1456	}
1457	}
1458	return err;
1459	}
1460
1461	#ifdef CONFIG_NUMA_BALANCING
1462	/*
1463	* Returns true if this is a safe migration target node for misplaced NUMA
1464	* pages. Currently it only checks the watermarks which crude
1465	*/
1466	static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1467	unsigned long nr_migrate_pages)
1468	{
1469	int z;
1470	for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1471	struct zone *zone = pgdat->node_zones + z;
1472
1473	if (!populated_zone(zone))
1474	continue;
1475
1476	if (!zone_reclaimable(zone))
1477	continue;
1478
1479	/* Avoid waking kswapd by allocating pages_to_migrate pages. */
1480	if (!zone_watermark_ok(zone, 0,
1481	high_wmark_pages(zone) +
1482	nr_migrate_pages,
1483	0, 0))
1484	continue;
1485	return true;
1486	}
1487	return false;
1488	}
1489
1490	static struct page alloc_misplaced_dst_page(struct page page,
1491	unsigned long data,
1492	int **result)
1493	{
1494	int nid = (int) data;
1495	struct page *newpage;
1496
1497	newpage = alloc_pages_exact_node(nid,
1498	(GFP_HIGHUSER_MOVABLE \| GFP_THISNODE \|
1499	__GFP_NOMEMALLOC \| __GFP_NORETRY \|
1500	__GFP_NOWARN) &
1501	~GFP_IOFS, 0);
1502	if (newpage)
1503	page_nid_xchg_last(newpage, page_nid_last(page));
1504
1505	return newpage;
1506	}
1507
1508	/*
1509	* page migration rate limiting control.
1510	* Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1511	* window of time. Default here says do not migrate more than 1280M per second.
1512	* If a node is rate-limited then PTE NUMA updates are also rate-limited. However
1513	* as it is faults that reset the window, pte updates will happen unconditionally
1514	* if there has not been a fault since @pteupdate_interval_millisecs after the
1515	* throttle window closed.
1516	*/
1517	static unsigned int migrate_interval_millisecs __read_mostly = 100;
1518	static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
1519	static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1520
1521	/* Returns true if NUMA migration is currently rate limited */
1522	bool migrate_ratelimited(int node)
1523	{
1524	pg_data_t *pgdat = NODE_DATA(node);
1525
1526	if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
1527	msecs_to_jiffies(pteupdate_interval_millisecs)))
1528	return false;
1529
1530	if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
1531	return false;
1532
1533	return true;
1534	}
1535
1536	/* Returns true if the node is migrate rate-limited after the update */
1537	bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages)
1538	{
1539	bool rate_limited = false;
1540
1541	/*
1542	* Rate-limit the amount of data that is being migrated to a node.
1543	* Optimal placement is no good if the memory bus is saturated and
1544	* all the time is being spent migrating!
1545	*/
1546	spin_lock(&pgdat->numabalancing_migrate_lock);
1547	if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1548	pgdat->numabalancing_migrate_nr_pages = 0;
1549	pgdat->numabalancing_migrate_next_window = jiffies +
1550	msecs_to_jiffies(migrate_interval_millisecs);
1551	}
1552	if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
1553	rate_limited = true;
1554	else
1555	pgdat->numabalancing_migrate_nr_pages += nr_pages;
1556	spin_unlock(&pgdat->numabalancing_migrate_lock);
1557
1558	return rate_limited;
1559	}
1560
1561	int numamigrate_isolate_page(pg_data_t pgdat, struct page page)
1562	{
1563	int page_lru;
1564
1565	VM_BUG_ON(compound_order(page) && !PageTransHuge(page));
1566
1567	/* Avoid migrating to a node that is nearly full */
1568	if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1569	return 0;
1570
1571	if (isolate_lru_page(page))
1572	return 0;
1573
1574	/*
1575	* migrate_misplaced_transhuge_page() skips page migration's usual
1576	* check on page_count(), so we must do it here, now that the page
1577	* has been isolated: a GUP pin, or any other pin, prevents migration.
1578	* The expected page count is 3: 1 for page's mapcount and 1 for the
1579	* caller's pin and 1 for the reference taken by isolate_lru_page().
1580	*/
1581	if (PageTransHuge(page) && page_count(page) != 3) {
1582	putback_lru_page(page);
1583	return 0;
1584	}
1585
1586	page_lru = page_is_file_cache(page);
1587	mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
1588	hpage_nr_pages(page));
1589
1590	/*
1591	* Isolating the page has taken another reference, so the
1592	* caller's reference can be safely dropped without the page
1593	* disappearing underneath us during migration.
1594	*/
1595	put_page(page);
1596	return 1;
1597	}
1598
1599	/*
1600	* Attempt to migrate a misplaced page to the specified destination
1601	* node. Caller is expected to have an elevated reference count on
1602	* the page that will be dropped by this function before returning.
1603	*/
1604	int migrate_misplaced_page(struct page *page, int node)
1605	{
1606	pg_data_t *pgdat = NODE_DATA(node);
1607	int isolated;
1608	int nr_remaining;
1609	LIST_HEAD(migratepages);
1610
1611	/*
1612	* Don't migrate pages that are mapped in multiple processes.
1613	* TODO: Handle false sharing detection instead of this hammer
1614	*/
1615	if (page_mapcount(page) != 1)
1616	goto out;
1617
1618	/*
1619	* Rate-limit the amount of data that is being migrated to a node.
1620	* Optimal placement is no good if the memory bus is saturated and
1621	* all the time is being spent migrating!
1622	*/
1623	if (numamigrate_update_ratelimit(pgdat, 1))
1624	goto out;
1625
1626	isolated = numamigrate_isolate_page(pgdat, page);
1627	if (!isolated)
1628	goto out;
1629
1630	list_add(&page->lru, &migratepages);
1631	nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1632	node, MIGRATE_ASYNC, MR_NUMA_MISPLACED);
1633	if (nr_remaining) {
1634	putback_lru_pages(&migratepages);
1635	isolated = 0;
1636	} else
1637	count_vm_numa_event(NUMA_PAGE_MIGRATE);
1638	BUG_ON(!list_empty(&migratepages));
1639	return isolated;
1640
1641	out:
1642	put_page(page);
1643	return 0;
1644	}
1645	#endif /* CONFIG_NUMA_BALANCING */
1646
1647	#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1648	/*
1649	* Migrates a THP to a given target node. page must be locked and is unlocked
1650	* before returning.
1651	*/
1652	int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1653	struct vm_area_struct *vma,
1654	pmd_t *pmd, pmd_t entry,
1655	unsigned long address,
1656	struct page *page, int node)
1657	{
1658	unsigned long haddr = address & HPAGE_PMD_MASK;
1659	pg_data_t *pgdat = NODE_DATA(node);
1660	int isolated = 0;
1661	struct page *new_page = NULL;
1662	struct mem_cgroup *memcg = NULL;
1663	int page_lru = page_is_file_cache(page);
1664
1665	/*
1666	* Don't migrate pages that are mapped in multiple processes.
1667	* TODO: Handle false sharing detection instead of this hammer
1668	*/
1669	if (page_mapcount(page) != 1)
1670	goto out_dropref;
1671
1672	/*
1673	* Rate-limit the amount of data that is being migrated to a node.
1674	* Optimal placement is no good if the memory bus is saturated and
1675	* all the time is being spent migrating!
1676	*/
1677	if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1678	goto out_dropref;
1679
1680	new_page = alloc_pages_node(node,
1681	(GFP_TRANSHUGE \| GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
1682	if (!new_page)
1683	goto out_fail;
1684
1685	page_nid_xchg_last(new_page, page_nid_last(page));
1686
1687	isolated = numamigrate_isolate_page(pgdat, page);
1688	if (!isolated) {
1689	put_page(new_page);
1690	goto out_fail;
1691	}
1692
1693	/* Prepare a page as a migration target */
1694	__set_page_locked(new_page);
1695	SetPageSwapBacked(new_page);
1696
1697	/* anon mapping, we can simply copy page->mapping to the new page: */
1698	new_page->mapping = page->mapping;
1699	new_page->index = page->index;
1700	migrate_page_copy(new_page, page);
1701	WARN_ON(PageLRU(new_page));
1702
1703	/* Recheck the target PMD */
1704	spin_lock(&mm->page_table_lock);
1705	if (unlikely(!pmd_same(*pmd, entry))) {
1706	spin_unlock(&mm->page_table_lock);
1707
1708	/* Reverse changes made by migrate_page_copy() */
1709	if (TestClearPageActive(new_page))
1710	SetPageActive(page);
1711	if (TestClearPageUnevictable(new_page))
1712	SetPageUnevictable(page);
1713	mlock_migrate_page(page, new_page);
1714
1715	unlock_page(new_page);
1716	put_page(new_page); /* Free it */
1717
1718	/* Retake the callers reference and putback on LRU */
1719	get_page(page);
1720	putback_lru_page(page);
1721	mod_zone_page_state(page_zone(page),
1722	NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
1723	goto out_fail;
1724	}
1725
1726	/*
1727	* Traditional migration needs to prepare the memcg charge
1728	* transaction early to prevent the old page from being
1729	* uncharged when installing migration entries. Here we can
1730	* save the potential rollback and start the charge transfer
1731	* only when migration is already known to end successfully.
1732	*/
1733	mem_cgroup_prepare_migration(page, new_page, &memcg);
1734
1735	entry = mk_pmd(new_page, vma->vm_page_prot);
1736	entry = pmd_mknonnuma(entry);
1737	entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1738	entry = pmd_mkhuge(entry);
1739
1740	pmdp_clear_flush(vma, haddr, pmd);
1741	set_pmd_at(mm, haddr, pmd, entry);
1742	page_add_new_anon_rmap(new_page, vma, haddr);
1743	update_mmu_cache_pmd(vma, address, &entry);
1744	page_remove_rmap(page);
1745	/*
1746	* Finish the charge transaction under the page table lock to
1747	* prevent split_huge_page() from dividing up the charge
1748	* before it's fully transferred to the new page.
1749	*/
1750	mem_cgroup_end_migration(memcg, page, new_page, true);
1751	spin_unlock(&mm->page_table_lock);
1752
1753	unlock_page(new_page);
1754	unlock_page(page);
1755	put_page(page); /* Drop the rmap reference */
1756	put_page(page); /* Drop the LRU isolation reference */
1757
1758	count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
1759	count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
1760
1761	mod_zone_page_state(page_zone(page),
1762	NR_ISOLATED_ANON + page_lru,
1763	-HPAGE_PMD_NR);
1764	return isolated;
1765
1766	out_fail:
1767	count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1768	out_dropref:
1769	entry = pmd_mknonnuma(entry);
1770	set_pmd_at(mm, haddr, pmd, entry);
1771	update_mmu_cache_pmd(vma, address, &entry);
1772
1773	unlock_page(page);
1774	put_page(page);
1775	return 0;
1776	}
1777	#endif /* CONFIG_NUMA_BALANCING */
1778
1779	#endif /* CONFIG_NUMA */
1780

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