1/*
   2 * Memory Migration functionality - linux/mm/migrate.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/backing-dev.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#include <linux/mmu_notifier.h>
  40#include <linux/page_idle.h>
  41#include <linux/page_owner.h>
  42
  43#include <asm/tlbflush.h>
  44
  45#define CREATE_TRACE_POINTS
  46#include <trace/events/migrate.h>
  47
  48#include "internal.h"
  49
  50/*
  51 * migrate_prep() needs to be called before we start compiling a list of pages
  52 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
  53 * undesirable, use migrate_prep_local()
  54 */
  55int migrate_prep(void)
  56{
  57	/*
  58	 * Clear the LRU lists so pages can be isolated.
  59	 * Note that pages may be moved off the LRU after we have
  60	 * drained them. Those pages will fail to migrate like other
  61	 * pages that may be busy.
  62	 */
  63	lru_add_drain_all();
  64
  65	return 0;
  66}
  67
  68/* Do the necessary work of migrate_prep but not if it involves other CPUs */
  69int migrate_prep_local(void)
  70{
  71	lru_add_drain();
  72
  73	return 0;
  74}
  75
  76/*
  77 * Put previously isolated pages back onto the appropriate lists
  78 * from where they were once taken off for compaction/migration.
  79 *
  80 * This function shall be used whenever the isolated pageset has been
  81 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
  82 * and isolate_huge_page().
  83 */
  84void putback_movable_pages(struct list_head *l)
  85{
  86	struct page *page;
  87	struct page *page2;
  88
  89	list_for_each_entry_safe(page, page2, l, lru) {
  90		if (unlikely(PageHuge(page))) {
  91			putback_active_hugepage(page);
  92			continue;
  93		}
  94		list_del(&page->lru);
  95		dec_zone_page_state(page, NR_ISOLATED_ANON +
  96				page_is_file_cache(page));
  97		if (unlikely(isolated_balloon_page(page)))
  98			balloon_page_putback(page);
  99		else
 100			putback_lru_page(page);
 101	}
 102}
 103
 104/*
 105 * Restore a potential migration pte to a working pte entry
 106 */
 107static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 108				 unsigned long addr, void *old)
 109{
 110	struct mm_struct *mm = vma->vm_mm;
 111	swp_entry_t entry;
 
 
 112 	pmd_t *pmd;
 113	pte_t *ptep, pte;
 114 	spinlock_t *ptl;
 115
 116	if (unlikely(PageHuge(new))) {
 117		ptep = huge_pte_offset(mm, addr);
 118		if (!ptep)
 119			goto out;
 120		ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
 121	} else {
 122		pmd = mm_find_pmd(mm, addr);
 123		if (!pmd)
 
 
 
 
 
 
 
 
 
 
 124			goto out;
 125
 126		ptep = pte_offset_map(pmd, addr);
 127
 128		/*
 129		 * Peek to check is_swap_pte() before taking ptlock?  No, we
 130		 * can race mremap's move_ptes(), which skips anon_vma lock.
 131		 */
 132
 133		ptl = pte_lockptr(mm, pmd);
 134	}
 135
 136 	spin_lock(ptl);
 137	pte = *ptep;
 138	if (!is_swap_pte(pte))
 139		goto unlock;
 140
 141	entry = pte_to_swp_entry(pte);
 142
 143	if (!is_migration_entry(entry) ||
 144	    migration_entry_to_page(entry) != old)
 145		goto unlock;
 146
 147	get_page(new);
 148	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
 149	if (pte_swp_soft_dirty(*ptep))
 150		pte = pte_mksoft_dirty(pte);
 151
 152	/* Recheck VMA as permissions can change since migration started  */
 153	if (is_write_migration_entry(entry))
 154		pte = maybe_mkwrite(pte, vma);
 155
 156#ifdef CONFIG_HUGETLB_PAGE
 157	if (PageHuge(new)) {
 158		pte = pte_mkhuge(pte);
 159		pte = arch_make_huge_pte(pte, vma, new, 0);
 160	}
 161#endif
 162	flush_dcache_page(new);
 163	set_pte_at(mm, addr, ptep, pte);
 164
 165	if (PageHuge(new)) {
 166		if (PageAnon(new))
 167			hugepage_add_anon_rmap(new, vma, addr);
 168		else
 169			page_dup_rmap(new, true);
 170	} else if (PageAnon(new))
 171		page_add_anon_rmap(new, vma, addr, false);
 172	else
 173		page_add_file_rmap(new);
 174
 175	if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
 176		mlock_vma_page(new);
 177
 178	/* No need to invalidate - it was non-present before */
 179	update_mmu_cache(vma, addr, ptep);
 180unlock:
 181	pte_unmap_unlock(ptep, ptl);
 182out:
 183	return SWAP_AGAIN;
 184}
 185
 186/*
 187 * Get rid of all migration entries and replace them by
 188 * references to the indicated page.
 189 */
 190void remove_migration_ptes(struct page *old, struct page *new, bool locked)
 191{
 192	struct rmap_walk_control rwc = {
 193		.rmap_one = remove_migration_pte,
 194		.arg = old,
 195	};
 196
 197	if (locked)
 198		rmap_walk_locked(new, &rwc);
 199	else
 200		rmap_walk(new, &rwc);
 201}
 202
 203/*
 204 * Something used the pte of a page under migration. We need to
 205 * get to the page and wait until migration is finished.
 206 * When we return from this function the fault will be retried.
 207 */
 208void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
 209				spinlock_t *ptl)
 210{
 211	pte_t pte;
 
 212	swp_entry_t entry;
 213	struct page *page;
 214
 215	spin_lock(ptl);
 216	pte = *ptep;
 217	if (!is_swap_pte(pte))
 218		goto out;
 219
 220	entry = pte_to_swp_entry(pte);
 221	if (!is_migration_entry(entry))
 222		goto out;
 223
 224	page = migration_entry_to_page(entry);
 225
 226	/*
 227	 * Once radix-tree replacement of page migration started, page_count
 228	 * *must* be zero. And, we don't want to call wait_on_page_locked()
 229	 * against a page without get_page().
 230	 * So, we use get_page_unless_zero(), here. Even failed, page fault
 231	 * will occur again.
 232	 */
 233	if (!get_page_unless_zero(page))
 234		goto out;
 235	pte_unmap_unlock(ptep, ptl);
 236	wait_on_page_locked(page);
 237	put_page(page);
 238	return;
 239out:
 240	pte_unmap_unlock(ptep, ptl);
 241}
 242
 243void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 244				unsigned long address)
 245{
 246	spinlock_t *ptl = pte_lockptr(mm, pmd);
 247	pte_t *ptep = pte_offset_map(pmd, address);
 248	__migration_entry_wait(mm, ptep, ptl);
 249}
 250
 251void migration_entry_wait_huge(struct vm_area_struct *vma,
 252		struct mm_struct *mm, pte_t *pte)
 253{
 254	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
 255	__migration_entry_wait(mm, pte, ptl);
 256}
 257
 258#ifdef CONFIG_BLOCK
 259/* Returns true if all buffers are successfully locked */
 260static 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
 301static 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 */
 316int 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		int extra_count)
 320{
 321	struct zone *oldzone, *newzone;
 322	int dirty;
 323	int expected_count = 1 + extra_count;
 324	void **pslot;
 325
 326	if (!mapping) {
 327		/* Anonymous page without mapping */
 328		if (page_count(page) != expected_count)
 329			return -EAGAIN;
 330
 331		/* No turning back from here */
 332		newpage->index = page->index;
 333		newpage->mapping = page->mapping;
 334		if (PageSwapBacked(page))
 335			SetPageSwapBacked(newpage);
 336
 337		return MIGRATEPAGE_SUCCESS;
 338	}
 339
 340	oldzone = page_zone(page);
 341	newzone = page_zone(newpage);
 342
 343	spin_lock_irq(&mapping->tree_lock);
 344
 345	pslot = radix_tree_lookup_slot(&mapping->page_tree,
 346 					page_index(page));
 347
 348	expected_count += 1 + page_has_private(page);
 349	if (page_count(page) != expected_count ||
 350		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
 351		spin_unlock_irq(&mapping->tree_lock);
 352		return -EAGAIN;
 353	}
 354
 355	if (!page_ref_freeze(page, expected_count)) {
 356		spin_unlock_irq(&mapping->tree_lock);
 357		return -EAGAIN;
 358	}
 359
 360	/*
 361	 * In the async migration case of moving a page with buffers, lock the
 362	 * buffers using trylock before the mapping is moved. If the mapping
 363	 * was moved, we later failed to lock the buffers and could not move
 364	 * the mapping back due to an elevated page count, we would have to
 365	 * block waiting on other references to be dropped.
 366	 */
 367	if (mode == MIGRATE_ASYNC && head &&
 368			!buffer_migrate_lock_buffers(head, mode)) {
 369		page_ref_unfreeze(page, expected_count);
 370		spin_unlock_irq(&mapping->tree_lock);
 371		return -EAGAIN;
 372	}
 373
 374	/*
 375	 * Now we know that no one else is looking at the page:
 376	 * no turning back from here.
 377	 */
 378	newpage->index = page->index;
 379	newpage->mapping = page->mapping;
 380	if (PageSwapBacked(page))
 381		SetPageSwapBacked(newpage);
 382
 383	get_page(newpage);	/* add cache reference */
 384	if (PageSwapCache(page)) {
 385		SetPageSwapCache(newpage);
 386		set_page_private(newpage, page_private(page));
 387	}
 388
 389	/* Move dirty while page refs frozen and newpage not yet exposed */
 390	dirty = PageDirty(page);
 391	if (dirty) {
 392		ClearPageDirty(page);
 393		SetPageDirty(newpage);
 394	}
 395
 396	radix_tree_replace_slot(pslot, newpage);
 397
 398	/*
 399	 * Drop cache reference from old page by unfreezing
 400	 * to one less reference.
 401	 * We know this isn't the last reference.
 402	 */
 403	page_ref_unfreeze(page, expected_count - 1);
 404
 405	spin_unlock(&mapping->tree_lock);
 406	/* Leave irq disabled to prevent preemption while updating stats */
 407
 408	/*
 409	 * If moved to a different zone then also account
 410	 * the page for that zone. Other VM counters will be
 411	 * taken care of when we establish references to the
 412	 * new page and drop references to the old page.
 413	 *
 414	 * Note that anonymous pages are accounted for
 415	 * via NR_FILE_PAGES and NR_ANON_PAGES if they
 416	 * are mapped to swap space.
 417	 */
 418	if (newzone != oldzone) {
 419		__dec_zone_state(oldzone, NR_FILE_PAGES);
 420		__inc_zone_state(newzone, NR_FILE_PAGES);
 421		if (PageSwapBacked(page) && !PageSwapCache(page)) {
 422			__dec_zone_state(oldzone, NR_SHMEM);
 423			__inc_zone_state(newzone, NR_SHMEM);
 424		}
 425		if (dirty && mapping_cap_account_dirty(mapping)) {
 426			__dec_zone_state(oldzone, NR_FILE_DIRTY);
 427			__inc_zone_state(newzone, NR_FILE_DIRTY);
 428		}
 429	}
 430	local_irq_enable();
 431
 432	return MIGRATEPAGE_SUCCESS;
 433}
 434
 435/*
 436 * The expected number of remaining references is the same as that
 437 * of migrate_page_move_mapping().
 438 */
 439int migrate_huge_page_move_mapping(struct address_space *mapping,
 440				   struct page *newpage, struct page *page)
 441{
 442	int expected_count;
 443	void **pslot;
 444
 
 
 
 
 
 
 445	spin_lock_irq(&mapping->tree_lock);
 446
 447	pslot = radix_tree_lookup_slot(&mapping->page_tree,
 448					page_index(page));
 449
 450	expected_count = 2 + page_has_private(page);
 451	if (page_count(page) != expected_count ||
 452		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
 453		spin_unlock_irq(&mapping->tree_lock);
 454		return -EAGAIN;
 455	}
 456
 457	if (!page_ref_freeze(page, expected_count)) {
 458		spin_unlock_irq(&mapping->tree_lock);
 459		return -EAGAIN;
 460	}
 461
 462	newpage->index = page->index;
 463	newpage->mapping = page->mapping;
 464
 465	get_page(newpage);
 466
 467	radix_tree_replace_slot(pslot, newpage);
 468
 469	page_ref_unfreeze(page, expected_count - 1);
 470
 471	spin_unlock_irq(&mapping->tree_lock);
 472
 473	return MIGRATEPAGE_SUCCESS;
 474}
 475
 476/*
 477 * Gigantic pages are so large that we do not guarantee that page++ pointer
 478 * arithmetic will work across the entire page.  We need something more
 479 * specialized.
 480 */
 481static void __copy_gigantic_page(struct page *dst, struct page *src,
 482				int nr_pages)
 483{
 484	int i;
 485	struct page *dst_base = dst;
 486	struct page *src_base = src;
 487
 488	for (i = 0; i < nr_pages; ) {
 489		cond_resched();
 490		copy_highpage(dst, src);
 491
 492		i++;
 493		dst = mem_map_next(dst, dst_base, i);
 494		src = mem_map_next(src, src_base, i);
 495	}
 496}
 497
 498static void copy_huge_page(struct page *dst, struct page *src)
 499{
 500	int i;
 501	int nr_pages;
 502
 503	if (PageHuge(src)) {
 504		/* hugetlbfs page */
 505		struct hstate *h = page_hstate(src);
 506		nr_pages = pages_per_huge_page(h);
 507
 508		if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
 509			__copy_gigantic_page(dst, src, nr_pages);
 510			return;
 511		}
 512	} else {
 513		/* thp page */
 514		BUG_ON(!PageTransHuge(src));
 515		nr_pages = hpage_nr_pages(src);
 516	}
 517
 518	for (i = 0; i < nr_pages; i++) {
 519		cond_resched();
 520		copy_highpage(dst + i, src + i);
 521	}
 522}
 523
 524/*
 525 * Copy the page to its new location
 526 */
 527void migrate_page_copy(struct page *newpage, struct page *page)
 528{
 529	int cpupid;
 530
 531	if (PageHuge(page) || PageTransHuge(page))
 532		copy_huge_page(newpage, page);
 533	else
 534		copy_highpage(newpage, page);
 535
 536	if (PageError(page))
 537		SetPageError(newpage);
 538	if (PageReferenced(page))
 539		SetPageReferenced(newpage);
 540	if (PageUptodate(page))
 541		SetPageUptodate(newpage);
 542	if (TestClearPageActive(page)) {
 543		VM_BUG_ON_PAGE(PageUnevictable(page), page);
 544		SetPageActive(newpage);
 545	} else if (TestClearPageUnevictable(page))
 546		SetPageUnevictable(newpage);
 547	if (PageChecked(page))
 548		SetPageChecked(newpage);
 549	if (PageMappedToDisk(page))
 550		SetPageMappedToDisk(newpage);
 551
 552	/* Move dirty on pages not done by migrate_page_move_mapping() */
 553	if (PageDirty(page))
 554		SetPageDirty(newpage);
 555
 556	if (page_is_young(page))
 557		set_page_young(newpage);
 558	if (page_is_idle(page))
 559		set_page_idle(newpage);
 560
 561	/*
 562	 * Copy NUMA information to the new page, to prevent over-eager
 563	 * future migrations of this same page.
 564	 */
 565	cpupid = page_cpupid_xchg_last(page, -1);
 566	page_cpupid_xchg_last(newpage, cpupid);
 567
 
 568	ksm_migrate_page(newpage, page);
 569	/*
 570	 * Please do not reorder this without considering how mm/ksm.c's
 571	 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
 572	 */
 573	if (PageSwapCache(page))
 574		ClearPageSwapCache(page);
 575	ClearPagePrivate(page);
 576	set_page_private(page, 0);
 577
 578	/*
 579	 * If any waiters have accumulated on the new page then
 580	 * wake them up.
 581	 */
 582	if (PageWriteback(newpage))
 583		end_page_writeback(newpage);
 584
 585	copy_page_owner(page, newpage);
 586
 587	mem_cgroup_migrate(page, newpage);
 588}
 589
 590/************************************************************
 591 *                    Migration functions
 592 ***********************************************************/
 593
 
 
 
 
 
 
 
 
 594/*
 595 * Common logic to directly migrate a single page suitable for
 596 * pages that do not use PagePrivate/PagePrivate2.
 597 *
 598 * Pages are locked upon entry and exit.
 599 */
 600int migrate_page(struct address_space *mapping,
 601		struct page *newpage, struct page *page,
 602		enum migrate_mode mode)
 603{
 604	int rc;
 605
 606	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
 607
 608	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
 609
 610	if (rc != MIGRATEPAGE_SUCCESS)
 611		return rc;
 612
 613	migrate_page_copy(newpage, page);
 614	return MIGRATEPAGE_SUCCESS;
 615}
 616EXPORT_SYMBOL(migrate_page);
 617
 618#ifdef CONFIG_BLOCK
 619/*
 620 * Migration function for pages with buffers. This function can only be used
 621 * if the underlying filesystem guarantees that no other references to "page"
 622 * exist.
 623 */
 624int buffer_migrate_page(struct address_space *mapping,
 625		struct page *newpage, struct page *page, enum migrate_mode mode)
 626{
 627	struct buffer_head *bh, *head;
 628	int rc;
 629
 630	if (!page_has_buffers(page))
 631		return migrate_page(mapping, newpage, page, mode);
 632
 633	head = page_buffers(page);
 634
 635	rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
 636
 637	if (rc != MIGRATEPAGE_SUCCESS)
 638		return rc;
 639
 640	/*
 641	 * In the async case, migrate_page_move_mapping locked the buffers
 642	 * with an IRQ-safe spinlock held. In the sync case, the buffers
 643	 * need to be locked now
 644	 */
 645	if (mode != MIGRATE_ASYNC)
 646		BUG_ON(!buffer_migrate_lock_buffers(head, mode));
 647
 648	ClearPagePrivate(page);
 649	set_page_private(newpage, page_private(page));
 650	set_page_private(page, 0);
 651	put_page(page);
 652	get_page(newpage);
 653
 654	bh = head;
 655	do {
 656		set_bh_page(bh, newpage, bh_offset(bh));
 657		bh = bh->b_this_page;
 658
 659	} while (bh != head);
 660
 661	SetPagePrivate(newpage);
 662
 663	migrate_page_copy(newpage, page);
 664
 665	bh = head;
 666	do {
 667		unlock_buffer(bh);
 668 		put_bh(bh);
 669		bh = bh->b_this_page;
 670
 671	} while (bh != head);
 672
 673	return MIGRATEPAGE_SUCCESS;
 674}
 675EXPORT_SYMBOL(buffer_migrate_page);
 676#endif
 677
 678/*
 679 * Writeback a page to clean the dirty state
 680 */
 681static int writeout(struct address_space *mapping, struct page *page)
 682{
 683	struct writeback_control wbc = {
 684		.sync_mode = WB_SYNC_NONE,
 685		.nr_to_write = 1,
 686		.range_start = 0,
 687		.range_end = LLONG_MAX,
 688		.for_reclaim = 1
 689	};
 690	int rc;
 691
 692	if (!mapping->a_ops->writepage)
 693		/* No write method for the address space */
 694		return -EINVAL;
 695
 696	if (!clear_page_dirty_for_io(page))
 697		/* Someone else already triggered a write */
 698		return -EAGAIN;
 699
 700	/*
 701	 * A dirty page may imply that the underlying filesystem has
 702	 * the page on some queue. So the page must be clean for
 703	 * migration. Writeout may mean we loose the lock and the
 704	 * page state is no longer what we checked for earlier.
 705	 * At this point we know that the migration attempt cannot
 706	 * be successful.
 707	 */
 708	remove_migration_ptes(page, page, false);
 709
 710	rc = mapping->a_ops->writepage(page, &wbc);
 711
 712	if (rc != AOP_WRITEPAGE_ACTIVATE)
 713		/* unlocked. Relock */
 714		lock_page(page);
 715
 716	return (rc < 0) ? -EIO : -EAGAIN;
 717}
 718
 719/*
 720 * Default handling if a filesystem does not provide a migration function.
 721 */
 722static int fallback_migrate_page(struct address_space *mapping,
 723	struct page *newpage, struct page *page, enum migrate_mode mode)
 724{
 725	if (PageDirty(page)) {
 726		/* Only writeback pages in full synchronous migration */
 727		if (mode != MIGRATE_SYNC)
 728			return -EBUSY;
 729		return writeout(mapping, page);
 730	}
 731
 732	/*
 733	 * Buffers may be managed in a filesystem specific way.
 734	 * We must have no buffers or drop them.
 735	 */
 736	if (page_has_private(page) &&
 737	    !try_to_release_page(page, GFP_KERNEL))
 738		return -EAGAIN;
 739
 740	return migrate_page(mapping, newpage, page, mode);
 741}
 742
 743/*
 744 * Move a page to a newly allocated page
 745 * The page is locked and all ptes have been successfully removed.
 746 *
 747 * The new page will have replaced the old page if this function
 748 * is successful.
 749 *
 750 * Return value:
 751 *   < 0 - error code
 752 *  MIGRATEPAGE_SUCCESS - success
 753 */
 754static int move_to_new_page(struct page *newpage, struct page *page,
 755				enum migrate_mode mode)
 756{
 757	struct address_space *mapping;
 758	int rc;
 759
 760	VM_BUG_ON_PAGE(!PageLocked(page), page);
 761	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
 
 
 
 
 
 
 
 
 
 
 
 762
 763	mapping = page_mapping(page);
 764	if (!mapping)
 765		rc = migrate_page(mapping, newpage, page, mode);
 766	else if (mapping->a_ops->migratepage)
 767		/*
 768		 * Most pages have a mapping and most filesystems provide a
 769		 * migratepage callback. Anonymous pages are part of swap
 770		 * space which also has its own migratepage callback. This
 771		 * is the most common path for page migration.
 772		 */
 773		rc = mapping->a_ops->migratepage(mapping, newpage, page, mode);
 
 774	else
 775		rc = fallback_migrate_page(mapping, newpage, page, mode);
 776
 777	/*
 778	 * When successful, old pagecache page->mapping must be cleared before
 779	 * page is freed; but stats require that PageAnon be left as PageAnon.
 780	 */
 781	if (rc == MIGRATEPAGE_SUCCESS) {
 782		if (!PageAnon(page))
 783			page->mapping = NULL;
 784	}
 
 
 
 785	return rc;
 786}
 787
 788static int __unmap_and_move(struct page *page, struct page *newpage,
 789				int force, enum migrate_mode mode)
 790{
 791	int rc = -EAGAIN;
 792	int page_was_mapped = 0;
 
 
 793	struct anon_vma *anon_vma = NULL;
 794
 795	if (!trylock_page(page)) {
 796		if (!force || mode == MIGRATE_ASYNC)
 797			goto out;
 798
 799		/*
 800		 * It's not safe for direct compaction to call lock_page.
 801		 * For example, during page readahead pages are added locked
 802		 * to the LRU. Later, when the IO completes the pages are
 803		 * marked uptodate and unlocked. However, the queueing
 804		 * could be merging multiple pages for one bio (e.g.
 805		 * mpage_readpages). If an allocation happens for the
 806		 * second or third page, the process can end up locking
 807		 * the same page twice and deadlocking. Rather than
 808		 * trying to be clever about what pages can be locked,
 809		 * avoid the use of lock_page for direct compaction
 810		 * altogether.
 811		 */
 812		if (current->flags & PF_MEMALLOC)
 813			goto out;
 814
 815		lock_page(page);
 816	}
 817
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 818	if (PageWriteback(page)) {
 819		/*
 820		 * Only in the case of a full synchronous migration is it
 821		 * necessary to wait for PageWriteback. In the async case,
 822		 * the retry loop is too short and in the sync-light case,
 823		 * the overhead of stalling is too much
 824		 */
 825		if (mode != MIGRATE_SYNC) {
 826			rc = -EBUSY;
 827			goto out_unlock;
 828		}
 829		if (!force)
 830			goto out_unlock;
 831		wait_on_page_writeback(page);
 832	}
 833
 834	/*
 835	 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
 836	 * we cannot notice that anon_vma is freed while we migrates a page.
 837	 * This get_anon_vma() delays freeing anon_vma pointer until the end
 838	 * of migration. File cache pages are no problem because of page_lock()
 839	 * File Caches may use write_page() or lock_page() in migration, then,
 840	 * just care Anon page here.
 841	 *
 842	 * Only page_get_anon_vma() understands the subtleties of
 843	 * getting a hold on an anon_vma from outside one of its mms.
 844	 * But if we cannot get anon_vma, then we won't need it anyway,
 845	 * because that implies that the anon page is no longer mapped
 846	 * (and cannot be remapped so long as we hold the page lock).
 847	 */
 848	if (PageAnon(page) && !PageKsm(page))
 849		anon_vma = page_get_anon_vma(page);
 850
 851	/*
 852	 * Block others from accessing the new page when we get around to
 853	 * establishing additional references. We are usually the only one
 854	 * holding a reference to newpage at this point. We used to have a BUG
 855	 * here if trylock_page(newpage) fails, but would like to allow for
 856	 * cases where there might be a race with the previous use of newpage.
 857	 * This is much like races on refcount of oldpage: just don't BUG().
 858	 */
 859	if (unlikely(!trylock_page(newpage)))
 860		goto out_unlock;
 861
 862	if (unlikely(isolated_balloon_page(page))) {
 863		/*
 864		 * A ballooned page does not need any special attention from
 865		 * physical to virtual reverse mapping procedures.
 866		 * Skip any attempt to unmap PTEs or to remap swap cache,
 867		 * in order to avoid burning cycles at rmap level, and perform
 868		 * the page migration right away (proteced by page lock).
 869		 */
 870		rc = balloon_page_migrate(newpage, page, mode);
 871		goto out_unlock_both;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 872	}
 873
 874	/*
 875	 * Corner case handling:
 876	 * 1. When a new swap-cache page is read into, it is added to the LRU
 877	 * and treated as swapcache but it has no rmap yet.
 878	 * Calling try_to_unmap() against a page->mapping==NULL page will
 879	 * trigger a BUG.  So handle it here.
 880	 * 2. An orphaned page (see truncate_complete_page) might have
 881	 * fs-private metadata. The page can be picked up due to memory
 882	 * offlining.  Everywhere else except page reclaim, the page is
 883	 * invisible to the vm, so the page can not be migrated.  So try to
 884	 * free the metadata, so the page can be freed.
 885	 */
 886	if (!page->mapping) {
 887		VM_BUG_ON_PAGE(PageAnon(page), page);
 888		if (page_has_private(page)) {
 889			try_to_free_buffers(page);
 890			goto out_unlock_both;
 891		}
 892	} else if (page_mapped(page)) {
 893		/* Establish migration ptes */
 894		VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
 895				page);
 896		try_to_unmap(page,
 897			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
 898		page_was_mapped = 1;
 899	}
 900
 
 
 
 
 901	if (!page_mapped(page))
 902		rc = move_to_new_page(newpage, page, mode);
 903
 904	if (page_was_mapped)
 905		remove_migration_ptes(page,
 906			rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
 907
 908out_unlock_both:
 909	unlock_page(newpage);
 910out_unlock:
 911	/* Drop an anon_vma reference if we took one */
 912	if (anon_vma)
 913		put_anon_vma(anon_vma);
 
 
 
 
 
 914	unlock_page(page);
 915out:
 916	return rc;
 917}
 918
 919/*
 920 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move().  Work
 921 * around it.
 922 */
 923#if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
 924#define ICE_noinline noinline
 925#else
 926#define ICE_noinline
 927#endif
 928
 929/*
 930 * Obtain the lock on page, remove all ptes and migrate the page
 931 * to the newly allocated page in newpage.
 932 */
 933static ICE_noinline int unmap_and_move(new_page_t get_new_page,
 934				   free_page_t put_new_page,
 935				   unsigned long private, struct page *page,
 936				   int force, enum migrate_mode mode,
 937				   enum migrate_reason reason)
 938{
 939	int rc = MIGRATEPAGE_SUCCESS;
 940	int *result = NULL;
 941	struct page *newpage;
 942
 943	newpage = get_new_page(page, private, &result);
 944	if (!newpage)
 945		return -ENOMEM;
 946
 947	if (page_count(page) == 1) {
 948		/* page was freed from under us. So we are done. */
 949		goto out;
 950	}
 951
 952	if (unlikely(PageTransHuge(page))) {
 953		lock_page(page);
 954		rc = split_huge_page(page);
 955		unlock_page(page);
 956		if (rc)
 957			goto out;
 958	}
 959
 960	rc = __unmap_and_move(page, newpage, force, mode);
 961	if (rc == MIGRATEPAGE_SUCCESS) {
 962		put_new_page = NULL;
 963		set_page_owner_migrate_reason(newpage, reason);
 964	}
 965
 
 966out:
 967	if (rc != -EAGAIN) {
 968		/*
 969		 * A page that has been migrated has all references
 970		 * removed and will be freed. A page that has not been
 971		 * migrated will have kepts its references and be
 972		 * restored.
 973		 */
 974		list_del(&page->lru);
 975		dec_zone_page_state(page, NR_ISOLATED_ANON +
 976				page_is_file_cache(page));
 977		/* Soft-offlined page shouldn't go through lru cache list */
 978		if (reason == MR_MEMORY_FAILURE && rc == MIGRATEPAGE_SUCCESS) {
 979			/*
 980			 * With this release, we free successfully migrated
 981			 * page and set PG_HWPoison on just freed page
 982			 * intentionally. Although it's rather weird, it's how
 983			 * HWPoison flag works at the moment.
 984			 */
 985			put_page(page);
 986			if (!test_set_page_hwpoison(page))
 987				num_poisoned_pages_inc();
 988		} else
 989			putback_lru_page(page);
 990	}
 991
 992	/*
 993	 * If migration was not successful and there's a freeing callback, use
 994	 * it.  Otherwise, putback_lru_page() will drop the reference grabbed
 995	 * during isolation.
 996	 */
 997	if (put_new_page)
 998		put_new_page(newpage, private);
 999	else if (unlikely(__is_movable_balloon_page(newpage))) {
1000		/* drop our reference, page already in the balloon */
1001		put_page(newpage);
1002	} else
1003		putback_lru_page(newpage);
1004
1005	if (result) {
1006		if (rc)
1007			*result = rc;
1008		else
1009			*result = page_to_nid(newpage);
1010	}
1011	return rc;
1012}
1013
1014/*
1015 * Counterpart of unmap_and_move_page() for hugepage migration.
1016 *
1017 * This function doesn't wait the completion of hugepage I/O
1018 * because there is no race between I/O and migration for hugepage.
1019 * Note that currently hugepage I/O occurs only in direct I/O
1020 * where no lock is held and PG_writeback is irrelevant,
1021 * and writeback status of all subpages are counted in the reference
1022 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1023 * under direct I/O, the reference of the head page is 512 and a bit more.)
1024 * This means that when we try to migrate hugepage whose subpages are
1025 * doing direct I/O, some references remain after try_to_unmap() and
1026 * hugepage migration fails without data corruption.
1027 *
1028 * There is also no race when direct I/O is issued on the page under migration,
1029 * because then pte is replaced with migration swap entry and direct I/O code
1030 * will wait in the page fault for migration to complete.
1031 */
1032static int unmap_and_move_huge_page(new_page_t get_new_page,
1033				free_page_t put_new_page, unsigned long private,
1034				struct page *hpage, int force,
1035				enum migrate_mode mode, int reason)
1036{
1037	int rc = -EAGAIN;
1038	int *result = NULL;
1039	int page_was_mapped = 0;
1040	struct page *new_hpage;
1041	struct anon_vma *anon_vma = NULL;
1042
1043	/*
1044	 * Movability of hugepages depends on architectures and hugepage size.
1045	 * This check is necessary because some callers of hugepage migration
1046	 * like soft offline and memory hotremove don't walk through page
1047	 * tables or check whether the hugepage is pmd-based or not before
1048	 * kicking migration.
1049	 */
1050	if (!hugepage_migration_supported(page_hstate(hpage))) {
1051		putback_active_hugepage(hpage);
1052		return -ENOSYS;
1053	}
1054
1055	new_hpage = get_new_page(hpage, private, &result);
1056	if (!new_hpage)
1057		return -ENOMEM;
1058
 
 
1059	if (!trylock_page(hpage)) {
1060		if (!force || mode != MIGRATE_SYNC)
1061			goto out;
1062		lock_page(hpage);
1063	}
1064
1065	if (PageAnon(hpage))
1066		anon_vma = page_get_anon_vma(hpage);
1067
1068	if (unlikely(!trylock_page(new_hpage)))
1069		goto put_anon;
1070
1071	if (page_mapped(hpage)) {
1072		try_to_unmap(hpage,
1073			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1074		page_was_mapped = 1;
1075	}
1076
1077	if (!page_mapped(hpage))
1078		rc = move_to_new_page(new_hpage, hpage, mode);
1079
1080	if (page_was_mapped)
1081		remove_migration_ptes(hpage,
1082			rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1083
1084	unlock_page(new_hpage);
 
1085
1086put_anon:
1087	if (anon_vma)
1088		put_anon_vma(anon_vma);
1089
1090	if (rc == MIGRATEPAGE_SUCCESS) {
1091		hugetlb_cgroup_migrate(hpage, new_hpage);
1092		put_new_page = NULL;
1093		set_page_owner_migrate_reason(new_hpage, reason);
1094	}
1095
1096	unlock_page(hpage);
 
1097out:
1098	if (rc != -EAGAIN)
1099		putback_active_hugepage(hpage);
 
 
1100
1101	/*
1102	 * If migration was not successful and there's a freeing callback, use
1103	 * it.  Otherwise, put_page() will drop the reference grabbed during
1104	 * isolation.
1105	 */
1106	if (put_new_page)
1107		put_new_page(new_hpage, private);
1108	else
1109		putback_active_hugepage(new_hpage);
1110
1111	if (result) {
1112		if (rc)
1113			*result = rc;
1114		else
1115			*result = page_to_nid(new_hpage);
1116	}
1117	return rc;
1118}
1119
1120/*
1121 * migrate_pages - migrate the pages specified in a list, to the free pages
1122 *		   supplied as the target for the page migration
1123 *
1124 * @from:		The list of pages to be migrated.
1125 * @get_new_page:	The function used to allocate free pages to be used
1126 *			as the target of the page migration.
1127 * @put_new_page:	The function used to free target pages if migration
1128 *			fails, or NULL if no special handling is necessary.
1129 * @private:		Private data to be passed on to get_new_page()
1130 * @mode:		The migration mode that specifies the constraints for
1131 *			page migration, if any.
1132 * @reason:		The reason for page migration.
1133 *
1134 * The function returns after 10 attempts or if no pages are movable any more
1135 * because the list has become empty or no retryable pages exist any more.
1136 * The caller should call putback_movable_pages() to return pages to the LRU
 
1137 * or free list only if ret != 0.
1138 *
1139 * Returns the number of pages that were not migrated, or an error code.
1140 */
1141int migrate_pages(struct list_head *from, new_page_t get_new_page,
1142		free_page_t put_new_page, unsigned long private,
1143		enum migrate_mode mode, int reason)
1144{
1145	int retry = 1;
1146	int nr_failed = 0;
1147	int nr_succeeded = 0;
1148	int pass = 0;
1149	struct page *page;
1150	struct page *page2;
1151	int swapwrite = current->flags & PF_SWAPWRITE;
1152	int rc;
1153
1154	if (!swapwrite)
1155		current->flags |= PF_SWAPWRITE;
1156
1157	for(pass = 0; pass < 10 && retry; pass++) {
1158		retry = 0;
1159
1160		list_for_each_entry_safe(page, page2, from, lru) {
1161			cond_resched();
1162
1163			if (PageHuge(page))
1164				rc = unmap_and_move_huge_page(get_new_page,
1165						put_new_page, private, page,
1166						pass > 2, mode, reason);
1167			else
1168				rc = unmap_and_move(get_new_page, put_new_page,
1169						private, page, pass > 2, mode,
1170						reason);
1171
1172			switch(rc) {
1173			case -ENOMEM:
1174				goto out;
1175			case -EAGAIN:
1176				retry++;
1177				break;
1178			case MIGRATEPAGE_SUCCESS:
1179				nr_succeeded++;
1180				break;
1181			default:
1182				/*
1183				 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1184				 * unlike -EAGAIN case, the failed page is
1185				 * removed from migration page list and not
1186				 * retried in the next outer loop.
1187				 */
1188				nr_failed++;
1189				break;
1190			}
1191		}
1192	}
1193	nr_failed += retry;
1194	rc = nr_failed;
1195out:
1196	if (nr_succeeded)
1197		count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1198	if (nr_failed)
1199		count_vm_events(PGMIGRATE_FAIL, nr_failed);
1200	trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1201
1202	if (!swapwrite)
1203		current->flags &= ~PF_SWAPWRITE;
1204
1205	return rc;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1206}
1207
1208#ifdef CONFIG_NUMA
1209/*
1210 * Move a list of individual pages
1211 */
1212struct page_to_node {
1213	unsigned long addr;
1214	struct page *page;
1215	int node;
1216	int status;
1217};
1218
1219static struct page *new_page_node(struct page *p, unsigned long private,
1220		int **result)
1221{
1222	struct page_to_node *pm = (struct page_to_node *)private;
1223
1224	while (pm->node != MAX_NUMNODES && pm->page != p)
1225		pm++;
1226
1227	if (pm->node == MAX_NUMNODES)
1228		return NULL;
1229
1230	*result = &pm->status;
1231
1232	if (PageHuge(p))
1233		return alloc_huge_page_node(page_hstate(compound_head(p)),
1234					pm->node);
1235	else
1236		return __alloc_pages_node(pm->node,
1237				GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
1238}
1239
1240/*
1241 * Move a set of pages as indicated in the pm array. The addr
1242 * field must be set to the virtual address of the page to be moved
1243 * and the node number must contain a valid target node.
1244 * The pm array ends with node = MAX_NUMNODES.
1245 */
1246static int do_move_page_to_node_array(struct mm_struct *mm,
1247				      struct page_to_node *pm,
1248				      int migrate_all)
1249{
1250	int err;
1251	struct page_to_node *pp;
1252	LIST_HEAD(pagelist);
1253
1254	down_read(&mm->mmap_sem);
1255
1256	/*
1257	 * Build a list of pages to migrate
1258	 */
1259	for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1260		struct vm_area_struct *vma;
1261		struct page *page;
1262
1263		err = -EFAULT;
1264		vma = find_vma(mm, pp->addr);
1265		if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1266			goto set_status;
1267
1268		/* FOLL_DUMP to ignore special (like zero) pages */
1269		page = follow_page(vma, pp->addr,
1270				FOLL_GET | FOLL_SPLIT | FOLL_DUMP);
1271
1272		err = PTR_ERR(page);
1273		if (IS_ERR(page))
1274			goto set_status;
1275
1276		err = -ENOENT;
1277		if (!page)
1278			goto set_status;
1279
 
 
 
 
1280		pp->page = page;
1281		err = page_to_nid(page);
1282
1283		if (err == pp->node)
1284			/*
1285			 * Node already in the right place
1286			 */
1287			goto put_and_set;
1288
1289		err = -EACCES;
1290		if (page_mapcount(page) > 1 &&
1291				!migrate_all)
1292			goto put_and_set;
1293
1294		if (PageHuge(page)) {
1295			if (PageHead(page))
1296				isolate_huge_page(page, &pagelist);
1297			goto put_and_set;
1298		}
1299
1300		err = isolate_lru_page(page);
1301		if (!err) {
1302			list_add_tail(&page->lru, &pagelist);
1303			inc_zone_page_state(page, NR_ISOLATED_ANON +
1304					    page_is_file_cache(page));
1305		}
1306put_and_set:
1307		/*
1308		 * Either remove the duplicate refcount from
1309		 * isolate_lru_page() or drop the page ref if it was
1310		 * not isolated.
1311		 */
1312		put_page(page);
1313set_status:
1314		pp->status = err;
1315	}
1316
1317	err = 0;
1318	if (!list_empty(&pagelist)) {
1319		err = migrate_pages(&pagelist, new_page_node, NULL,
1320				(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1321		if (err)
1322			putback_movable_pages(&pagelist);
1323	}
1324
1325	up_read(&mm->mmap_sem);
1326	return err;
1327}
1328
1329/*
1330 * Migrate an array of page address onto an array of nodes and fill
1331 * the corresponding array of status.
1332 */
1333static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1334			 unsigned long nr_pages,
1335			 const void __user * __user *pages,
1336			 const int __user *nodes,
1337			 int __user *status, int flags)
1338{
1339	struct page_to_node *pm;
1340	unsigned long chunk_nr_pages;
1341	unsigned long chunk_start;
1342	int err;
1343
1344	err = -ENOMEM;
1345	pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1346	if (!pm)
1347		goto out;
1348
1349	migrate_prep();
1350
1351	/*
1352	 * Store a chunk of page_to_node array in a page,
1353	 * but keep the last one as a marker
1354	 */
1355	chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1356
1357	for (chunk_start = 0;
1358	     chunk_start < nr_pages;
1359	     chunk_start += chunk_nr_pages) {
1360		int j;
1361
1362		if (chunk_start + chunk_nr_pages > nr_pages)
1363			chunk_nr_pages = nr_pages - chunk_start;
1364
1365		/* fill the chunk pm with addrs and nodes from user-space */
1366		for (j = 0; j < chunk_nr_pages; j++) {
1367			const void __user *p;
1368			int node;
1369
1370			err = -EFAULT;
1371			if (get_user(p, pages + j + chunk_start))
1372				goto out_pm;
1373			pm[j].addr = (unsigned long) p;
1374
1375			if (get_user(node, nodes + j + chunk_start))
1376				goto out_pm;
1377
1378			err = -ENODEV;
1379			if (node < 0 || node >= MAX_NUMNODES)
1380				goto out_pm;
1381
1382			if (!node_state(node, N_MEMORY))
1383				goto out_pm;
1384
1385			err = -EACCES;
1386			if (!node_isset(node, task_nodes))
1387				goto out_pm;
1388
1389			pm[j].node = node;
1390		}
1391
1392		/* End marker for this chunk */
1393		pm[chunk_nr_pages].node = MAX_NUMNODES;
1394
1395		/* Migrate this chunk */
1396		err = do_move_page_to_node_array(mm, pm,
1397						 flags & MPOL_MF_MOVE_ALL);
1398		if (err < 0)
1399			goto out_pm;
1400
1401		/* Return status information */
1402		for (j = 0; j < chunk_nr_pages; j++)
1403			if (put_user(pm[j].status, status + j + chunk_start)) {
1404				err = -EFAULT;
1405				goto out_pm;
1406			}
1407	}
1408	err = 0;
1409
1410out_pm:
1411	free_page((unsigned long)pm);
1412out:
1413	return err;
1414}
1415
1416/*
1417 * Determine the nodes of an array of pages and store it in an array of status.
1418 */
1419static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1420				const void __user **pages, int *status)
1421{
1422	unsigned long i;
1423
1424	down_read(&mm->mmap_sem);
1425
1426	for (i = 0; i < nr_pages; i++) {
1427		unsigned long addr = (unsigned long)(*pages);
1428		struct vm_area_struct *vma;
1429		struct page *page;
1430		int err = -EFAULT;
1431
1432		vma = find_vma(mm, addr);
1433		if (!vma || addr < vma->vm_start)
1434			goto set_status;
1435
1436		/* FOLL_DUMP to ignore special (like zero) pages */
1437		page = follow_page(vma, addr, FOLL_DUMP);
1438
1439		err = PTR_ERR(page);
1440		if (IS_ERR(page))
1441			goto set_status;
1442
1443		err = page ? page_to_nid(page) : -ENOENT;
 
 
 
 
 
1444set_status:
1445		*status = err;
1446
1447		pages++;
1448		status++;
1449	}
1450
1451	up_read(&mm->mmap_sem);
1452}
1453
1454/*
1455 * Determine the nodes of a user array of pages and store it in
1456 * a user array of status.
1457 */
1458static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1459			 const void __user * __user *pages,
1460			 int __user *status)
1461{
1462#define DO_PAGES_STAT_CHUNK_NR 16
1463	const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1464	int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1465
1466	while (nr_pages) {
1467		unsigned long chunk_nr;
1468
1469		chunk_nr = nr_pages;
1470		if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1471			chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1472
1473		if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1474			break;
1475
1476		do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1477
1478		if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1479			break;
1480
1481		pages += chunk_nr;
1482		status += chunk_nr;
1483		nr_pages -= chunk_nr;
1484	}
1485	return nr_pages ? -EFAULT : 0;
1486}
1487
1488/*
1489 * Move a list of pages in the address space of the currently executing
1490 * process.
1491 */
1492SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1493		const void __user * __user *, pages,
1494		const int __user *, nodes,
1495		int __user *, status, int, flags)
1496{
1497	const struct cred *cred = current_cred(), *tcred;
1498	struct task_struct *task;
1499	struct mm_struct *mm;
1500	int err;
1501	nodemask_t task_nodes;
1502
1503	/* Check flags */
1504	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1505		return -EINVAL;
1506
1507	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1508		return -EPERM;
1509
1510	/* Find the mm_struct */
1511	rcu_read_lock();
1512	task = pid ? find_task_by_vpid(pid) : current;
1513	if (!task) {
1514		rcu_read_unlock();
1515		return -ESRCH;
1516	}
1517	get_task_struct(task);
1518
1519	/*
1520	 * Check if this process has the right to modify the specified
1521	 * process. The right exists if the process has administrative
1522	 * capabilities, superuser privileges or the same
1523	 * userid as the target process.
1524	 */
1525	tcred = __task_cred(task);
1526	if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1527	    !uid_eq(cred->uid,  tcred->suid) && !uid_eq(cred->uid,  tcred->uid) &&
1528	    !capable(CAP_SYS_NICE)) {
1529		rcu_read_unlock();
1530		err = -EPERM;
1531		goto out;
1532	}
1533	rcu_read_unlock();
1534
1535 	err = security_task_movememory(task);
1536 	if (err)
1537		goto out;
1538
1539	task_nodes = cpuset_mems_allowed(task);
1540	mm = get_task_mm(task);
1541	put_task_struct(task);
1542
1543	if (!mm)
1544		return -EINVAL;
1545
1546	if (nodes)
1547		err = do_pages_move(mm, task_nodes, nr_pages, pages,
1548				    nodes, status, flags);
1549	else
1550		err = do_pages_stat(mm, nr_pages, pages, status);
1551
1552	mmput(mm);
1553	return err;
1554
1555out:
1556	put_task_struct(task);
1557	return err;
1558}
1559
1560#ifdef CONFIG_NUMA_BALANCING
1561/*
1562 * Returns true if this is a safe migration target node for misplaced NUMA
1563 * pages. Currently it only checks the watermarks which crude
1564 */
1565static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1566				   unsigned long nr_migrate_pages)
1567{
1568	int z;
1569	for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1570		struct zone *zone = pgdat->node_zones + z;
1571
1572		if (!populated_zone(zone))
1573			continue;
1574
1575		if (!zone_reclaimable(zone))
1576			continue;
1577
1578		/* Avoid waking kswapd by allocating pages_to_migrate pages. */
1579		if (!zone_watermark_ok(zone, 0,
1580				       high_wmark_pages(zone) +
1581				       nr_migrate_pages,
1582				       0, 0))
1583			continue;
1584		return true;
1585	}
1586	return false;
1587}
1588
1589static struct page *alloc_misplaced_dst_page(struct page *page,
1590					   unsigned long data,
1591					   int **result)
1592{
1593	int nid = (int) data;
1594	struct page *newpage;
1595
1596	newpage = __alloc_pages_node(nid,
1597					 (GFP_HIGHUSER_MOVABLE |
1598					  __GFP_THISNODE | __GFP_NOMEMALLOC |
1599					  __GFP_NORETRY | __GFP_NOWARN) &
1600					 ~__GFP_RECLAIM, 0);
1601
1602	return newpage;
1603}
1604
1605/*
1606 * page migration rate limiting control.
1607 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1608 * window of time. Default here says do not migrate more than 1280M per second.
1609 */
1610static unsigned int migrate_interval_millisecs __read_mostly = 100;
1611static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1612
1613/* Returns true if the node is migrate rate-limited after the update */
1614static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1615					unsigned long nr_pages)
1616{
1617	/*
1618	 * Rate-limit the amount of data that is being migrated to a node.
1619	 * Optimal placement is no good if the memory bus is saturated and
1620	 * all the time is being spent migrating!
1621	 */
1622	if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1623		spin_lock(&pgdat->numabalancing_migrate_lock);
1624		pgdat->numabalancing_migrate_nr_pages = 0;
1625		pgdat->numabalancing_migrate_next_window = jiffies +
1626			msecs_to_jiffies(migrate_interval_millisecs);
1627		spin_unlock(&pgdat->numabalancing_migrate_lock);
1628	}
1629	if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1630		trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1631								nr_pages);
1632		return true;
1633	}
1634
1635	/*
1636	 * This is an unlocked non-atomic update so errors are possible.
1637	 * The consequences are failing to migrate when we potentiall should
1638	 * have which is not severe enough to warrant locking. If it is ever
1639	 * a problem, it can be converted to a per-cpu counter.
1640	 */
1641	pgdat->numabalancing_migrate_nr_pages += nr_pages;
1642	return false;
1643}
1644
1645static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1646{
1647	int page_lru;
1648
1649	VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1650
1651	/* Avoid migrating to a node that is nearly full */
1652	if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1653		return 0;
1654
1655	if (isolate_lru_page(page))
1656		return 0;
1657
1658	/*
1659	 * migrate_misplaced_transhuge_page() skips page migration's usual
1660	 * check on page_count(), so we must do it here, now that the page
1661	 * has been isolated: a GUP pin, or any other pin, prevents migration.
1662	 * The expected page count is 3: 1 for page's mapcount and 1 for the
1663	 * caller's pin and 1 for the reference taken by isolate_lru_page().
1664	 */
1665	if (PageTransHuge(page) && page_count(page) != 3) {
1666		putback_lru_page(page);
1667		return 0;
1668	}
1669
1670	page_lru = page_is_file_cache(page);
1671	mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
1672				hpage_nr_pages(page));
1673
1674	/*
1675	 * Isolating the page has taken another reference, so the
1676	 * caller's reference can be safely dropped without the page
1677	 * disappearing underneath us during migration.
1678	 */
1679	put_page(page);
1680	return 1;
1681}
1682
1683bool pmd_trans_migrating(pmd_t pmd)
1684{
1685	struct page *page = pmd_page(pmd);
1686	return PageLocked(page);
1687}
1688
1689/*
1690 * Attempt to migrate a misplaced page to the specified destination
1691 * node. Caller is expected to have an elevated reference count on
1692 * the page that will be dropped by this function before returning.
1693 */
1694int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1695			   int node)
1696{
1697	pg_data_t *pgdat = NODE_DATA(node);
1698	int isolated;
1699	int nr_remaining;
1700	LIST_HEAD(migratepages);
1701
1702	/*
1703	 * Don't migrate file pages that are mapped in multiple processes
1704	 * with execute permissions as they are probably shared libraries.
1705	 */
1706	if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1707	    (vma->vm_flags & VM_EXEC))
1708		goto out;
1709
1710	/*
1711	 * Rate-limit the amount of data that is being migrated to a node.
1712	 * Optimal placement is no good if the memory bus is saturated and
1713	 * all the time is being spent migrating!
1714	 */
1715	if (numamigrate_update_ratelimit(pgdat, 1))
1716		goto out;
1717
1718	isolated = numamigrate_isolate_page(pgdat, page);
1719	if (!isolated)
1720		goto out;
1721
1722	list_add(&page->lru, &migratepages);
1723	nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1724				     NULL, node, MIGRATE_ASYNC,
1725				     MR_NUMA_MISPLACED);
1726	if (nr_remaining) {
1727		if (!list_empty(&migratepages)) {
1728			list_del(&page->lru);
1729			dec_zone_page_state(page, NR_ISOLATED_ANON +
1730					page_is_file_cache(page));
1731			putback_lru_page(page);
1732		}
1733		isolated = 0;
1734	} else
1735		count_vm_numa_event(NUMA_PAGE_MIGRATE);
1736	BUG_ON(!list_empty(&migratepages));
1737	return isolated;
1738
1739out:
1740	put_page(page);
1741	return 0;
1742}
1743#endif /* CONFIG_NUMA_BALANCING */
1744
1745#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1746/*
1747 * Migrates a THP to a given target node. page must be locked and is unlocked
1748 * before returning.
1749 */
1750int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1751				struct vm_area_struct *vma,
1752				pmd_t *pmd, pmd_t entry,
1753				unsigned long address,
1754				struct page *page, int node)
1755{
1756	spinlock_t *ptl;
1757	pg_data_t *pgdat = NODE_DATA(node);
1758	int isolated = 0;
1759	struct page *new_page = NULL;
1760	int page_lru = page_is_file_cache(page);
1761	unsigned long mmun_start = address & HPAGE_PMD_MASK;
1762	unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
1763	pmd_t orig_entry;
1764
1765	/*
1766	 * Rate-limit the amount of data that is being migrated to a node.
1767	 * Optimal placement is no good if the memory bus is saturated and
1768	 * all the time is being spent migrating!
1769	 */
1770	if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1771		goto out_dropref;
1772
1773	new_page = alloc_pages_node(node,
1774		(GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM,
1775		HPAGE_PMD_ORDER);
1776	if (!new_page)
1777		goto out_fail;
1778	prep_transhuge_page(new_page);
1779
1780	isolated = numamigrate_isolate_page(pgdat, page);
1781	if (!isolated) {
1782		put_page(new_page);
1783		goto out_fail;
1784	}
1785	/*
1786	 * We are not sure a pending tlb flush here is for a huge page
1787	 * mapping or not. Hence use the tlb range variant
1788	 */
1789	if (mm_tlb_flush_pending(mm))
1790		flush_tlb_range(vma, mmun_start, mmun_end);
1791
1792	/* Prepare a page as a migration target */
1793	__SetPageLocked(new_page);
1794	SetPageSwapBacked(new_page);
1795
1796	/* anon mapping, we can simply copy page->mapping to the new page: */
1797	new_page->mapping = page->mapping;
1798	new_page->index = page->index;
1799	migrate_page_copy(new_page, page);
1800	WARN_ON(PageLRU(new_page));
1801
1802	/* Recheck the target PMD */
1803	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1804	ptl = pmd_lock(mm, pmd);
1805	if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) {
1806fail_putback:
1807		spin_unlock(ptl);
1808		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1809
1810		/* Reverse changes made by migrate_page_copy() */
1811		if (TestClearPageActive(new_page))
1812			SetPageActive(page);
1813		if (TestClearPageUnevictable(new_page))
1814			SetPageUnevictable(page);
1815
1816		unlock_page(new_page);
1817		put_page(new_page);		/* Free it */
1818
1819		/* Retake the callers reference and putback on LRU */
1820		get_page(page);
1821		putback_lru_page(page);
1822		mod_zone_page_state(page_zone(page),
1823			 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
1824
1825		goto out_unlock;
1826	}
1827
1828	orig_entry = *pmd;
1829	entry = mk_pmd(new_page, vma->vm_page_prot);
1830	entry = pmd_mkhuge(entry);
1831	entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1832
1833	/*
1834	 * Clear the old entry under pagetable lock and establish the new PTE.
1835	 * Any parallel GUP will either observe the old page blocking on the
1836	 * page lock, block on the page table lock or observe the new page.
1837	 * The SetPageUptodate on the new page and page_add_new_anon_rmap
1838	 * guarantee the copy is visible before the pagetable update.
1839	 */
1840	flush_cache_range(vma, mmun_start, mmun_end);
1841	page_add_anon_rmap(new_page, vma, mmun_start, true);
1842	pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
1843	set_pmd_at(mm, mmun_start, pmd, entry);
1844	update_mmu_cache_pmd(vma, address, &entry);
1845
1846	if (page_count(page) != 2) {
1847		set_pmd_at(mm, mmun_start, pmd, orig_entry);
1848		flush_pmd_tlb_range(vma, mmun_start, mmun_end);
1849		mmu_notifier_invalidate_range(mm, mmun_start, mmun_end);
1850		update_mmu_cache_pmd(vma, address, &entry);
1851		page_remove_rmap(new_page, true);
1852		goto fail_putback;
1853	}
1854
1855	mlock_migrate_page(new_page, page);
1856	page_remove_rmap(page, true);
1857	set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
1858
1859	spin_unlock(ptl);
1860	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1861
1862	/* Take an "isolate" reference and put new page on the LRU. */
1863	get_page(new_page);
1864	putback_lru_page(new_page);
1865
1866	unlock_page(new_page);
1867	unlock_page(page);
1868	put_page(page);			/* Drop the rmap reference */
1869	put_page(page);			/* Drop the LRU isolation reference */
1870
1871	count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
1872	count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
1873
1874	mod_zone_page_state(page_zone(page),
1875			NR_ISOLATED_ANON + page_lru,
1876			-HPAGE_PMD_NR);
1877	return isolated;
1878
1879out_fail:
1880	count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1881out_dropref:
1882	ptl = pmd_lock(mm, pmd);
1883	if (pmd_same(*pmd, entry)) {
1884		entry = pmd_modify(entry, vma->vm_page_prot);
1885		set_pmd_at(mm, mmun_start, pmd, entry);
1886		update_mmu_cache_pmd(vma, address, &entry);
1887	}
1888	spin_unlock(ptl);
1889
1890out_unlock:
1891	unlock_page(page);
1892	put_page(page);
1893	return 0;
1894}
1895#endif /* CONFIG_NUMA_BALANCING */
1896
1897#endif /* CONFIG_NUMA */