Commit message: mm: try_to_unmap_cluster() should lock_page() before mlocking

A BUG_ON(!PageLocked) was triggered in mlock_vma_page() by Sasha Levin
fuzzing with trinity.  The call site try_to_unmap_cluster() does not lock
the pages other than its check_page parameter (which is already locked).

The BUG_ON in mlock_vma_page() is not documented and its purpose is
somewhat unclear, but apparently it serializes against page migration,
which could otherwise fail to transfer the PG_mlocked flag.  This would
not be fatal, as the page would be eventually encountered again, but
NR_MLOCK accounting would become distorted nevertheless.  This patch adds
a comment to the BUG_ON in mlock_vma_page() and munlock_vma_page() to that
effect.

The call site try_to_unmap_cluster() is fixed so that for page !=
check_page, trylock_page() is attempted (to avoid possible deadlocks as we
already have check_page locked) and mlock_vma_page() is performed only
upon success.  If the page lock cannot be obtained, the page is left
without PG_mlocked, which is again not a problem in the whole unevictable
memory design.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2014-3122
CWE: CWE-264
Vulnerability description: The try_to_unmap_cluster function in mm/rmap.c in the Linux kernel before 3.14.3 does not properly consider which pages must be locked, which allows local users to cause a denial of service (system crash) by triggering a memory-usage pattern that requires removal of page-table mappings.

Project: linux
File: mlock.c

SYSCALL_DEFINE0(munlockall)
{
	int ret;

	down_write(&current->mm->mmap_sem);
	ret = do_mlockall(0);
	up_write(&current->mm->mmap_sem);
	return ret;
}

Project: linux
File: mlock.c

SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
{
	unsigned long locked;
	unsigned long lock_limit;
	int error = -ENOMEM;

	if (!can_do_mlock())
		return -EPERM;

	lru_add_drain_all();	/* flush pagevec */

	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
	start &= PAGE_MASK;

	lock_limit = rlimit(RLIMIT_MEMLOCK);
	lock_limit >>= PAGE_SHIFT;
	locked = len >> PAGE_SHIFT;

	down_write(&current->mm->mmap_sem);

	locked += current->mm->locked_vm;

	/* check against resource limits */
	if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
		error = do_mlock(start, len, 1);

	up_write(&current->mm->mmap_sem);
	if (!error)
		error = __mm_populate(start, len, 0);
	return error;
}

Project: linux
File: mlock.c

SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
	int ret;

	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
	start &= PAGE_MASK;

	down_write(&current->mm->mmap_sem);
	ret = do_mlock(start, len, 0);
	up_write(&current->mm->mmap_sem);

	return ret;
}

Project: linux
File: mlock.c

static int __mlock_posix_error_return(long retval)
{
	if (retval == -EFAULT)
		retval = -ENOMEM;
	else if (retval == -ENOMEM)
		retval = -EAGAIN;
	return retval;
}

Project: linux
File: mlock.c

long __mlock_vma_pages_range(struct vm_area_struct *vma,
		unsigned long start, unsigned long end, int *nonblocking)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long nr_pages = (end - start) / PAGE_SIZE;
	int gup_flags;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(end   & ~PAGE_MASK);
	VM_BUG_ON(start < vma->vm_start);
	VM_BUG_ON(end   > vma->vm_end);
	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));

	gup_flags = FOLL_TOUCH | FOLL_MLOCK;
	/*
	 * We want to touch writable mappings with a write fault in order
	 * to break COW, except for shared mappings because these don't COW
	 * and we would not want to dirty them for nothing.
	 */
	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
		gup_flags |= FOLL_WRITE;

	/*
	 * We want mlock to succeed for regions that have any permissions
	 * other than PROT_NONE.
	 */
	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
		gup_flags |= FOLL_FORCE;

	/*
	 * We made sure addr is within a VMA, so the following will
	 * not result in a stack expansion that recurses back here.
	 */
	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
				NULL, NULL, nonblocking);
}

Project: linux
File: mlock.c

static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
{
	if (PageLRU(page)) {
		struct lruvec *lruvec;

		lruvec = mem_cgroup_page_lruvec(page, page_zone(page));
		if (getpage)
			get_page(page);
		ClearPageLRU(page);
		del_page_from_lru_list(page, lruvec, page_lru(page));
		return true;
	}

	return false;
}

Project: linux
File: mlock.c

static void __munlock_isolated_page(struct page *page)
{
	int ret = SWAP_AGAIN;

	/*
	 * Optimization: if the page was mapped just once, that's our mapping
	 * and we don't need to check all the other vmas.
	 */
	if (page_mapcount(page) > 1)
		ret = try_to_munlock(page);

	/* Did try_to_unlock() succeed or punt? */
	if (ret != SWAP_MLOCK)
		count_vm_event(UNEVICTABLE_PGMUNLOCKED);

	putback_lru_page(page);
}

Project: linux
File: mlock.c

static void __munlock_isolation_failed(struct page *page)
{
	if (PageUnevictable(page))
		__count_vm_event(UNEVICTABLE_PGSTRANDED);
	else
		__count_vm_event(UNEVICTABLE_PGMUNLOCKED);
}

Project: linux
File: mlock.c

static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
{
	int i;
	int nr = pagevec_count(pvec);
	int delta_munlocked;
	struct pagevec pvec_putback;
	int pgrescued = 0;

	pagevec_init(&pvec_putback, 0);

	/* Phase 1: page isolation */
	spin_lock_irq(&zone->lru_lock);
	for (i = 0; i < nr; i++) {
		struct page *page = pvec->pages[i];

		if (TestClearPageMlocked(page)) {
			/*
			 * We already have pin from follow_page_mask()
			 * so we can spare the get_page() here.
			 */
			if (__munlock_isolate_lru_page(page, false))
				continue;
			else
				__munlock_isolation_failed(page);
		}

		/*
		 * We won't be munlocking this page in the next phase
		 * but we still need to release the follow_page_mask()
		 * pin. We cannot do it under lru_lock however. If it's
		 * the last pin, __page_cache_release() would deadlock.
		 */
		pagevec_add(&pvec_putback, pvec->pages[i]);
		pvec->pages[i] = NULL;
	}
	delta_munlocked = -nr + pagevec_count(&pvec_putback);
	__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
	spin_unlock_irq(&zone->lru_lock);

	/* Now we can release pins of pages that we are not munlocking */
	pagevec_release(&pvec_putback);

	/* Phase 2: page munlock */
	for (i = 0; i < nr; i++) {
		struct page *page = pvec->pages[i];

		if (page) {
			lock_page(page);
			if (!__putback_lru_fast_prepare(page, &pvec_putback,
					&pgrescued)) {
				/*
				 * Slow path. We don't want to lose the last
				 * pin before unlock_page()
				 */
				get_page(page); /* for putback_lru_page() */
				__munlock_isolated_page(page);
				unlock_page(page);
				put_page(page); /* from follow_page_mask() */
			}
		}
	}

	/*
	 * Phase 3: page putback for pages that qualified for the fast path
	 * This will also call put_page() to return pin from follow_page_mask()
	 */
	if (pagevec_count(&pvec_putback))
		__putback_lru_fast(&pvec_putback, pgrescued);
}

Project: linux
File: mlock.c

static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
		struct vm_area_struct *vma, int zoneid,	unsigned long start,
		unsigned long end)
{
	pte_t *pte;
	spinlock_t *ptl;

	/*
	 * Initialize pte walk starting at the already pinned page where we
	 * are sure that there is a pte, as it was pinned under the same
	 * mmap_sem write op.
	 */
	pte = get_locked_pte(vma->vm_mm, start,	&ptl);
	/* Make sure we do not cross the page table boundary */
	end = pgd_addr_end(start, end);
	end = pud_addr_end(start, end);
	end = pmd_addr_end(start, end);

	/* The page next to the pinned page is the first we will try to get */
	start += PAGE_SIZE;
	while (start < end) {
		struct page *page = NULL;
		pte++;
		if (pte_present(*pte))
			page = vm_normal_page(vma, start, *pte);
		/*
		 * Break if page could not be obtained or the page's node+zone does not
		 * match
		 */
		if (!page || page_zone_id(page) != zoneid)
			break;

		get_page(page);
		/*
		 * Increase the address that will be returned *before* the
		 * eventual break due to pvec becoming full by adding the page
		 */
		start += PAGE_SIZE;
		if (pagevec_add(pvec, page) == 0)
			break;
	}
	pte_unmap_unlock(pte, ptl);
	return start;
}

Project: linux
File: mlock.c

static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
{
	count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
	/*
	 *__pagevec_lru_add() calls release_pages() so we don't call
	 * put_page() explicitly
	 */
	__pagevec_lru_add(pvec);
	count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
}

Project: linux
File: mlock.c

static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
		int *pgrescued)
{
	VM_BUG_ON_PAGE(PageLRU(page), page);
	VM_BUG_ON_PAGE(!PageLocked(page), page);

	if (page_mapcount(page) <= 1 && page_evictable(page)) {
		pagevec_add(pvec, page);
		if (TestClearPageUnevictable(page))
			(*pgrescued)++;
		unlock_page(page);
		return true;
	}

	return false;
}

Project: linux
File: mlock.c

int can_do_mlock(void)
{
	if (capable(CAP_IPC_LOCK))
		return 1;
	if (rlimit(RLIMIT_MEMLOCK) != 0)
		return 1;
	return 0;
}

Project: linux
File: mlock.c

void clear_page_mlock(struct page *page)
{
	if (!TestClearPageMlocked(page))
		return;

	mod_zone_page_state(page_zone(page), NR_MLOCK,
			    -hpage_nr_pages(page));
	count_vm_event(UNEVICTABLE_PGCLEARED);
	if (!isolate_lru_page(page)) {
		putback_lru_page(page);
	} else {
		/*
		 * We lost the race. the page already moved to evictable list.
		 */
		if (PageUnevictable(page))
			count_vm_event(UNEVICTABLE_PGSTRANDED);
	}
}

Project: linux
File: mlock.c

static int do_mlockall(int flags)
{
	struct vm_area_struct * vma, * prev = NULL;

	if (flags & MCL_FUTURE)
		current->mm->def_flags |= VM_LOCKED;
	else
		current->mm->def_flags &= ~VM_LOCKED;
	if (flags == MCL_FUTURE)
		goto out;

	for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
		vm_flags_t newflags;

		newflags = vma->vm_flags & ~VM_LOCKED;
		if (flags & MCL_CURRENT)
			newflags |= VM_LOCKED;

		/* Ignore errors */
		mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
		cond_resched();
	}
out:
	return 0;
}

Project: linux
File: mlock.c

static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
	unsigned long start, unsigned long end, vm_flags_t newflags)
{
	struct mm_struct *mm = vma->vm_mm;
	pgoff_t pgoff;
	int nr_pages;
	int ret = 0;
	int lock = !!(newflags & VM_LOCKED);

	if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
		goto out;	/* don't set VM_LOCKED,  don't count */

	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
			  vma->vm_file, pgoff, vma_policy(vma));
	if (*prev) {
		vma = *prev;
		goto success;
	}

	if (start != vma->vm_start) {
		ret = split_vma(mm, vma, start, 1);
		if (ret)
			goto out;
	}

	if (end != vma->vm_end) {
		ret = split_vma(mm, vma, end, 0);
		if (ret)
			goto out;
	}

success:
	/*
	 * Keep track of amount of locked VM.
	 */
	nr_pages = (end - start) >> PAGE_SHIFT;
	if (!lock)
		nr_pages = -nr_pages;
	mm->locked_vm += nr_pages;

	/*
	 * vm_flags is protected by the mmap_sem held in write mode.
	 * It's okay if try_to_unmap_one unmaps a page just after we
	 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
	 */

	if (lock)
		vma->vm_flags = newflags;
	else
		munlock_vma_pages_range(vma, start, end);

out:
	*prev = vma;
	return ret;
}

Project: linux
File: mlock.c

void munlock_vma_pages_range(struct vm_area_struct *vma,
			     unsigned long start, unsigned long end)
{
	vma->vm_flags &= ~VM_LOCKED;

	while (start < end) {
		struct page *page = NULL;
		unsigned int page_mask;
		unsigned long page_increm;
		struct pagevec pvec;
		struct zone *zone;
		int zoneid;

		pagevec_init(&pvec, 0);
		/*
		 * Although FOLL_DUMP is intended for get_dump_page(),
		 * it just so happens that its special treatment of the
		 * ZERO_PAGE (returning an error instead of doing get_page)
		 * suits munlock very well (and if somehow an abnormal page
		 * has sneaked into the range, we won't oops here: great).
		 */
		page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
				&page_mask);

		if (page && !IS_ERR(page)) {
			if (PageTransHuge(page)) {
				lock_page(page);
				/*
				 * Any THP page found by follow_page_mask() may
				 * have gotten split before reaching
				 * munlock_vma_page(), so we need to recompute
				 * the page_mask here.
				 */
				page_mask = munlock_vma_page(page);
				unlock_page(page);
				put_page(page); /* follow_page_mask() */
			} else {
				/*
				 * Non-huge pages are handled in batches via
				 * pagevec. The pin from follow_page_mask()
				 * prevents them from collapsing by THP.
				 */
				pagevec_add(&pvec, page);
				zone = page_zone(page);
				zoneid = page_zone_id(page);

				/*
				 * Try to fill the rest of pagevec using fast
				 * pte walk. This will also update start to
				 * the next page to process. Then munlock the
				 * pagevec.
				 */
				start = __munlock_pagevec_fill(&pvec, vma,
						zoneid, start, end);
				__munlock_pagevec(&pvec, zone);
				goto next;
			}
		}
		/* It's a bug to munlock in the middle of a THP page */
		VM_BUG_ON((start >> PAGE_SHIFT) & page_mask);
		page_increm = 1 + page_mask;
		start += page_increm * PAGE_SIZE;
next:
		cond_resched();
	}
}

Project: linux
File: mlock.c

void user_shm_unlock(size_t size, struct user_struct *user)
{
	spin_lock(&shmlock_user_lock);
	user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	spin_unlock(&shmlock_user_lock);
	free_uid(user);
}

Project: linux
File: rmap.c

static void __hugepage_set_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address, int exclusive)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	BUG_ON(!anon_vma);

	if (PageAnon(page))
		return;
	if (!exclusive)
		anon_vma = anon_vma->root;

	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	page->mapping = (struct address_space *) anon_vma;
	page->index = linear_page_index(vma, address);
}

Project: linux
File: rmap.c

static void __page_check_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
#ifdef CONFIG_DEBUG_VM
	/*
	 * The page's anon-rmap details (mapping and index) are guaranteed to
	 * be set up correctly at this point.
	 *
	 * We have exclusion against page_add_anon_rmap because the caller
	 * always holds the page locked, except if called from page_dup_rmap,
	 * in which case the page is already known to be setup.
	 *
	 * We have exclusion against page_add_new_anon_rmap because those pages
	 * are initially only visible via the pagetables, and the pte is locked
	 * over the call to page_add_new_anon_rmap.
	 */
	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
	BUG_ON(page->index != linear_page_index(vma, address));
#endif
}

Project: linux
File: rmap.c

static void __page_set_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address, int exclusive)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	BUG_ON(!anon_vma);

	if (PageAnon(page))
		return;

	/*
	 * If the page isn't exclusively mapped into this vma,
	 * we must use the _oldest_ possible anon_vma for the
	 * page mapping!
	 */
	if (!exclusive)
		anon_vma = anon_vma->root;

	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	page->mapping = (struct address_space *) anon_vma;
	page->index = linear_page_index(vma, address);
}

Project: linux
File: rmap.c

void __put_anon_vma(struct anon_vma *anon_vma)
{
	struct anon_vma *root = anon_vma->root;

	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
		anon_vma_free(root);

	anon_vma_free(anon_vma);
}

Project: linux
File: rmap.c

__vma_address(struct page *page, struct vm_area_struct *vma)
{
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

	if (unlikely(is_vm_hugetlb_page(vma)))
		pgoff = page->index << huge_page_order(page_hstate(page));

	return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
}

Project: linux
File: rmap.c

static inline struct anon_vma *anon_vma_alloc(void)
{
	struct anon_vma *anon_vma;

	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
	if (anon_vma) {
		atomic_set(&anon_vma->refcount, 1);
		/*
		 * Initialise the anon_vma root to point to itself. If called
		 * from fork, the root will be reset to the parents anon_vma.
		 */
		anon_vma->root = anon_vma;
	}

	return anon_vma;
}

Project: linux
File: rmap.c

static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
{
	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
}

Project: linux
File: rmap.c

static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
{
	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
}

Project: linux
File: rmap.c

static void anon_vma_chain_link(struct vm_area_struct *vma,
				struct anon_vma_chain *avc,
				struct anon_vma *anon_vma)
{
	avc->vma = vma;
	avc->anon_vma = anon_vma;
	list_add(&avc->same_vma, &vma->anon_vma_chain);
	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
}

Project: linux
File: rmap.c

int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
{
	struct anon_vma_chain *avc, *pavc;
	struct anon_vma *root = NULL;

	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
		struct anon_vma *anon_vma;

		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
		if (unlikely(!avc)) {
			unlock_anon_vma_root(root);
			root = NULL;
			avc = anon_vma_chain_alloc(GFP_KERNEL);
			if (!avc)
				goto enomem_failure;
		}
		anon_vma = pavc->anon_vma;
		root = lock_anon_vma_root(root, anon_vma);
		anon_vma_chain_link(dst, avc, anon_vma);
	}
	unlock_anon_vma_root(root);
	return 0;

 enomem_failure:
	unlink_anon_vmas(dst);
	return -ENOMEM;
}

Project: linux
File: rmap.c

static void anon_vma_ctor(void *data)
{
	struct anon_vma *anon_vma = data;

	init_rwsem(&anon_vma->rwsem);
	atomic_set(&anon_vma->refcount, 0);
	anon_vma->rb_root = RB_ROOT;
}

Project: linux
File: rmap.c

int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
{
	struct anon_vma_chain *avc;
	struct anon_vma *anon_vma;

	/* Don't bother if the parent process has no anon_vma here. */
	if (!pvma->anon_vma)
		return 0;

	/*
	 * First, attach the new VMA to the parent VMA's anon_vmas,
	 * so rmap can find non-COWed pages in child processes.
	 */
	if (anon_vma_clone(vma, pvma))
		return -ENOMEM;

	/* Then add our own anon_vma. */
	anon_vma = anon_vma_alloc();
	if (!anon_vma)
		goto out_error;
	avc = anon_vma_chain_alloc(GFP_KERNEL);
	if (!avc)
		goto out_error_free_anon_vma;

	/*
	 * The root anon_vma's spinlock is the lock actually used when we
	 * lock any of the anon_vmas in this anon_vma tree.
	 */
	anon_vma->root = pvma->anon_vma->root;
	/*
	 * With refcounts, an anon_vma can stay around longer than the
	 * process it belongs to. The root anon_vma needs to be pinned until
	 * this anon_vma is freed, because the lock lives in the root.
	 */
	get_anon_vma(anon_vma->root);
	/* Mark this anon_vma as the one where our new (COWed) pages go. */
	vma->anon_vma = anon_vma;
	anon_vma_lock_write(anon_vma);
	anon_vma_chain_link(vma, avc, anon_vma);
	anon_vma_unlock_write(anon_vma);

	return 0;

 out_error_free_anon_vma:
	put_anon_vma(anon_vma);
 out_error:
	unlink_anon_vmas(vma);
	return -ENOMEM;
}

Project: linux
File: rmap.c

static inline void anon_vma_free(struct anon_vma *anon_vma)
{
	VM_BUG_ON(atomic_read(&anon_vma->refcount));

	/*
	 * Synchronize against page_lock_anon_vma_read() such that
	 * we can safely hold the lock without the anon_vma getting
	 * freed.
	 *
	 * Relies on the full mb implied by the atomic_dec_and_test() from
	 * put_anon_vma() against the acquire barrier implied by
	 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
	 *
	 * page_lock_anon_vma_read()	VS	put_anon_vma()
	 *   down_read_trylock()		  atomic_dec_and_test()
	 *   LOCK				  MB
	 *   atomic_read()			  rwsem_is_locked()
	 *
	 * LOCK should suffice since the actual taking of the lock must
	 * happen _before_ what follows.
	 */
	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
		anon_vma_lock_write(anon_vma);
		anon_vma_unlock_write(anon_vma);
	}

	kmem_cache_free(anon_vma_cachep, anon_vma);
}

Project: linux
File: rmap.c

void __init anon_vma_init(void)
{
	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
			0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
}

Project: linux
File: rmap.c

int anon_vma_prepare(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	struct anon_vma_chain *avc;

	might_sleep();
	if (unlikely(!anon_vma)) {
		struct mm_struct *mm = vma->vm_mm;
		struct anon_vma *allocated;

		avc = anon_vma_chain_alloc(GFP_KERNEL);
		if (!avc)
			goto out_enomem;

		anon_vma = find_mergeable_anon_vma(vma);
		allocated = NULL;
		if (!anon_vma) {
			anon_vma = anon_vma_alloc();
			if (unlikely(!anon_vma))
				goto out_enomem_free_avc;
			allocated = anon_vma;
		}

		anon_vma_lock_write(anon_vma);
		/* page_table_lock to protect against threads */
		spin_lock(&mm->page_table_lock);
		if (likely(!vma->anon_vma)) {
			vma->anon_vma = anon_vma;
			anon_vma_chain_link(vma, avc, anon_vma);
			allocated = NULL;
			avc = NULL;
		}
		spin_unlock(&mm->page_table_lock);
		anon_vma_unlock_write(anon_vma);

		if (unlikely(allocated))
			put_anon_vma(allocated);
		if (unlikely(avc))
			anon_vma_chain_free(avc);
	}
	return 0;

 out_enomem_free_avc:
	anon_vma_chain_free(avc);
 out_enomem:
	return -ENOMEM;
}

Project: linux
File: rmap.c

void do_page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address, int exclusive)
{
	int first = atomic_inc_and_test(&page->_mapcount);
	if (first) {
		if (PageTransHuge(page))
			__inc_zone_page_state(page,
					      NR_ANON_TRANSPARENT_HUGEPAGES);
		__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
				hpage_nr_pages(page));
	}
	if (unlikely(PageKsm(page)))
		return;

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	/* address might be in next vma when migration races vma_adjust */
	if (first)
		__page_set_anon_rmap(page, vma, address, exclusive);
	else
		__page_check_anon_rmap(page, vma, address);
}

Project: linux
File: rmap.c

void hugepage_add_anon_rmap(struct page *page,
			    struct vm_area_struct *vma, unsigned long address)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	int first;

	BUG_ON(!PageLocked(page));
	BUG_ON(!anon_vma);
	/* address might be in next vma when migration races vma_adjust */
	first = atomic_inc_and_test(&page->_mapcount);
	if (first)
		__hugepage_set_anon_rmap(page, vma, address, 0);
}

Project: linux
File: rmap.c

void hugepage_add_new_anon_rmap(struct page *page,
			struct vm_area_struct *vma, unsigned long address)
{
	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
	atomic_set(&page->_mapcount, 0);
	__hugepage_set_anon_rmap(page, vma, address, 1);
}

Project: linux
File: rmap.c

static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
{
	return is_vma_temporary_stack(vma);
}

Project: linux
File: rmap.c

static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
{
	if (vma->vm_flags & VM_SHARED)
		return false;

	return true;
}

Project: linux
File: rmap.c

static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
{
	struct page_referenced_arg *pra = arg;
	struct mem_cgroup *memcg = pra->memcg;

	if (!mm_match_cgroup(vma->vm_mm, memcg))
		return true;

	return false;
}

Project: linux
File: rmap.c

bool is_vma_temporary_stack(struct vm_area_struct *vma)
{
	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);

	if (!maybe_stack)
		return false;

	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
						VM_STACK_INCOMPLETE_SETUP)
		return true;

	return false;
}

Project: linux
File: rmap.c

static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
{
	struct anon_vma *new_root = anon_vma->root;
	if (new_root != root) {
		if (WARN_ON_ONCE(root))
			up_write(&root->rwsem);
		root = new_root;
		down_write(&root->rwsem);
	}
	return root;
}

Project: linux
File: rmap.c

pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd = NULL;

	pgd = pgd_offset(mm, address);
	if (!pgd_present(*pgd))
		goto out;

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		goto out;

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		pmd = NULL;
out:
	return pmd;
}

Project: linux
File: rmap.c

void page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
	do_page_add_anon_rmap(page, vma, address, 0);
}

Project: linux
File: rmap.c

void page_add_file_rmap(struct page *page)
{
	bool locked;
	unsigned long flags;

	mem_cgroup_begin_update_page_stat(page, &locked, &flags);
	if (atomic_inc_and_test(&page->_mapcount)) {
		__inc_zone_page_state(page, NR_FILE_MAPPED);
		mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
	}
	mem_cgroup_end_update_page_stat(page, &locked, &flags);
}

Project: linux
File: rmap.c

void page_add_new_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
	SetPageSwapBacked(page);
	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
	if (PageTransHuge(page))
		__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
	__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
			hpage_nr_pages(page));
	__page_set_anon_rmap(page, vma, address, 1);
	if (!mlocked_vma_newpage(vma, page)) {
		SetPageActive(page);
		lru_cache_add(page);
	} else
		add_page_to_unevictable_list(page);
}

Project: linux
File: rmap.c

unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
	unsigned long address;
	if (PageAnon(page)) {
		struct anon_vma *page__anon_vma = page_anon_vma(page);
		/*
		 * Note: swapoff's unuse_vma() is more efficient with this
		 * check, and needs it to match anon_vma when KSM is active.
		 */
		if (!vma->anon_vma || !page__anon_vma ||
		    vma->anon_vma->root != page__anon_vma->root)
			return -EFAULT;
	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
		if (!vma->vm_file ||
		    vma->vm_file->f_mapping != page->mapping)
			return -EFAULT;
	} else
		return -EFAULT;
	address = __vma_address(page, vma);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
		return -EFAULT;
	return address;
}

Project: linux
File: rmap.c

struct anon_vma *page_get_anon_vma(struct page *page)
{
	struct anon_vma *anon_vma = NULL;
	unsigned long anon_mapping;

	rcu_read_lock();
	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
		goto out;
	if (!page_mapped(page))
		goto out;

	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
		anon_vma = NULL;
		goto out;
	}

	/*
	 * If this page is still mapped, then its anon_vma cannot have been
	 * freed.  But if it has been unmapped, we have no security against the
	 * anon_vma structure being freed and reused (for another anon_vma:
	 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
	 * above cannot corrupt).
	 */
	if (!page_mapped(page)) {
		put_anon_vma(anon_vma);
		anon_vma = NULL;
	}
out:
	rcu_read_unlock();

	return anon_vma;
}

Project: linux
File: rmap.c

struct anon_vma *page_lock_anon_vma_read(struct page *page)
{
	struct anon_vma *anon_vma = NULL;
	struct anon_vma *root_anon_vma;
	unsigned long anon_mapping;

	rcu_read_lock();
	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
		goto out;
	if (!page_mapped(page))
		goto out;

	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
	root_anon_vma = ACCESS_ONCE(anon_vma->root);
	if (down_read_trylock(&root_anon_vma->rwsem)) {
		/*
		 * If the page is still mapped, then this anon_vma is still
		 * its anon_vma, and holding the mutex ensures that it will
		 * not go away, see anon_vma_free().
		 */
		if (!page_mapped(page)) {
			up_read(&root_anon_vma->rwsem);
			anon_vma = NULL;
		}
		goto out;
	}

	/* trylock failed, we got to sleep */
	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
		anon_vma = NULL;
		goto out;
	}

	if (!page_mapped(page)) {
		put_anon_vma(anon_vma);
		anon_vma = NULL;
		goto out;
	}

	/* we pinned the anon_vma, its safe to sleep */
	rcu_read_unlock();
	anon_vma_lock_read(anon_vma);

	if (atomic_dec_and_test(&anon_vma->refcount)) {
		/*
		 * Oops, we held the last refcount, release the lock
		 * and bail -- can't simply use put_anon_vma() because
		 * we'll deadlock on the anon_vma_lock_write() recursion.
		 */
		anon_vma_unlock_read(anon_vma);
		__put_anon_vma(anon_vma);
		anon_vma = NULL;
	}

	return anon_vma;

out:
	rcu_read_unlock();
	return anon_vma;
}

Project: linux
File: rmap.c

int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
{
	unsigned long address;
	pte_t *pte;
	spinlock_t *ptl;

	address = __vma_address(page, vma);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
		return 0;
	pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
	if (!pte)			/* the page is not in this mm */
		return 0;
	pte_unmap_unlock(pte, ptl);

	return 1;
}

Project: linux
File: rmap.c

int page_mkclean(struct page *page)
{
	int cleaned = 0;
	struct address_space *mapping;
	struct rmap_walk_control rwc = {
		.arg = (void *)&cleaned,
		.rmap_one = page_mkclean_one,
		.invalid_vma = invalid_mkclean_vma,
	};

	BUG_ON(!PageLocked(page));

	if (!page_mapped(page))
		return 0;

	mapping = page_mapping(page);
	if (!mapping)
		return 0;

	rmap_walk(page, &rwc);

	return cleaned;
}

Project: linux
File: rmap.c

static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
			    unsigned long address, void *arg)
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte;
	spinlock_t *ptl;
	int ret = 0;
	int *cleaned = arg;

	pte = page_check_address(page, mm, address, &ptl, 1);
	if (!pte)
		goto out;

	if (pte_dirty(*pte) || pte_write(*pte)) {
		pte_t entry;

		flush_cache_page(vma, address, pte_pfn(*pte));
		entry = ptep_clear_flush(vma, address, pte);
		entry = pte_wrprotect(entry);
		entry = pte_mkclean(entry);
		set_pte_at(mm, address, pte, entry);
		ret = 1;
	}

	pte_unmap_unlock(pte, ptl);

	if (ret) {
		mmu_notifier_invalidate_page(mm, address);
		(*cleaned)++;
	}
out:
	return SWAP_AGAIN;
}

Project: linux
File: rmap.c

void page_move_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON(!anon_vma);
	VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);

	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	page->mapping = (struct address_space *) anon_vma;
}

Project: linux
File: rmap.c

static int page_not_mapped(struct page *page)
{
	return !page_mapped(page);
};

Project: linux
File: rmap.c

int page_referenced(struct page *page,
		    int is_locked,
		    struct mem_cgroup *memcg,
		    unsigned long *vm_flags)
{
	int ret;
	int we_locked = 0;
	struct page_referenced_arg pra = {
		.mapcount = page_mapcount(page),
		.memcg = memcg,
	};
	struct rmap_walk_control rwc = {
		.rmap_one = page_referenced_one,
		.arg = (void *)&pra,
		.anon_lock = page_lock_anon_vma_read,
	};

	*vm_flags = 0;
	if (!page_mapped(page))
		return 0;

	if (!page_rmapping(page))
		return 0;

	if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
		we_locked = trylock_page(page);
		if (!we_locked)
			return 1;
	}

	/*
	 * If we are reclaiming on behalf of a cgroup, skip
	 * counting on behalf of references from different
	 * cgroups
	 */
	if (memcg) {
		rwc.invalid_vma = invalid_page_referenced_vma;
	}

	ret = rmap_walk(page, &rwc);
	*vm_flags = pra.vm_flags;

	if (we_locked)
		unlock_page(page);

	return pra.referenced;
}

Project: linux
File: rmap.c

void page_remove_rmap(struct page *page)
{
	bool anon = PageAnon(page);
	bool locked;
	unsigned long flags;

	/*
	 * The anon case has no mem_cgroup page_stat to update; but may
	 * uncharge_page() below, where the lock ordering can deadlock if
	 * we hold the lock against page_stat move: so avoid it on anon.
	 */
	if (!anon)
		mem_cgroup_begin_update_page_stat(page, &locked, &flags);

	/* page still mapped by someone else? */
	if (!atomic_add_negative(-1, &page->_mapcount))
		goto out;

	/*
	 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
	 * and not charged by memcg for now.
	 */
	if (unlikely(PageHuge(page)))
		goto out;
	if (anon) {
		mem_cgroup_uncharge_page(page);
		if (PageTransHuge(page))
			__dec_zone_page_state(page,
					      NR_ANON_TRANSPARENT_HUGEPAGES);
		__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
				-hpage_nr_pages(page));
	} else {
		__dec_zone_page_state(page, NR_FILE_MAPPED);
		mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
		mem_cgroup_end_update_page_stat(page, &locked, &flags);
	}
	if (unlikely(PageMlocked(page)))
		clear_page_mlock(page);
	/*
	 * It would be tidy to reset the PageAnon mapping here,
	 * but that might overwrite a racing page_add_anon_rmap
	 * which increments mapcount after us but sets mapping
	 * before us: so leave the reset to free_hot_cold_page,
	 * and remember that it's only reliable while mapped.
	 * Leaving it set also helps swapoff to reinstate ptes
	 * faster for those pages still in swapcache.
	 */
	return;
out:
	if (!anon)
		mem_cgroup_end_update_page_stat(page, &locked, &flags);
}

Project: linux
File: rmap.c

void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
{
	anon_vma_unlock_read(anon_vma);
}

Project: linux
File: rmap.c

int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
{
	if (unlikely(PageKsm(page)))
		return rmap_walk_ksm(page, rwc);
	else if (PageAnon(page))
		return rmap_walk_anon(page, rwc);
	else
		return rmap_walk_file(page, rwc);
}

Project: linux
File: rmap.c

static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
{
	struct anon_vma *anon_vma;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct anon_vma_chain *avc;
	int ret = SWAP_AGAIN;

	anon_vma = rmap_walk_anon_lock(page, rwc);
	if (!anon_vma)
		return ret;

	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
		struct vm_area_struct *vma = avc->vma;
		unsigned long address = vma_address(page, vma);

		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
			continue;

		ret = rwc->rmap_one(page, vma, address, rwc->arg);
		if (ret != SWAP_AGAIN)
			break;
		if (rwc->done && rwc->done(page))
			break;
	}
	anon_vma_unlock_read(anon_vma);
	return ret;
}

Project: linux
File: rmap.c

static struct anon_vma *rmap_walk_anon_lock(struct page *page,
					struct rmap_walk_control *rwc)
{
	struct anon_vma *anon_vma;

	if (rwc->anon_lock)
		return rwc->anon_lock(page);

	/*
	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
	 * because that depends on page_mapped(); but not all its usages
	 * are holding mmap_sem. Users without mmap_sem are required to
	 * take a reference count to prevent the anon_vma disappearing
	 */
	anon_vma = page_anon_vma(page);
	if (!anon_vma)
		return NULL;

	anon_vma_lock_read(anon_vma);
	return anon_vma;
}

Project: linux
File: rmap.c

int try_to_munlock(struct page *page)
{
	int ret;
	struct rmap_walk_control rwc = {
		.rmap_one = try_to_unmap_one,
		.arg = (void *)TTU_MUNLOCK,
		.done = page_not_mapped,
		/*
		 * We don't bother to try to find the munlocked page in
		 * nonlinears. It's costly. Instead, later, page reclaim logic
		 * may call try_to_unmap() and recover PG_mlocked lazily.
		 */
		.file_nonlinear = NULL,
		.anon_lock = page_lock_anon_vma_read,

	};

	VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);

	ret = rmap_walk(page, &rwc);
	return ret;
}

Project: linux
File: rmap.c

int try_to_unmap(struct page *page, enum ttu_flags flags)
{
	int ret;
	struct rmap_walk_control rwc = {
		.rmap_one = try_to_unmap_one,
		.arg = (void *)flags,
		.done = page_not_mapped,
		.file_nonlinear = try_to_unmap_nonlinear,
		.anon_lock = page_lock_anon_vma_read,
	};

	VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page);

	/*
	 * During exec, a temporary VMA is setup and later moved.
	 * The VMA is moved under the anon_vma lock but not the
	 * page tables leading to a race where migration cannot
	 * find the migration ptes. Rather than increasing the
	 * locking requirements of exec(), migration skips
	 * temporary VMAs until after exec() completes.
	 */
	if (flags & TTU_MIGRATION && !PageKsm(page) && PageAnon(page))
		rwc.invalid_vma = invalid_migration_vma;

	ret = rmap_walk(page, &rwc);

	if (ret != SWAP_MLOCK && !page_mapped(page))
		ret = SWAP_SUCCESS;
	return ret;
}

Project: linux
File: rmap.c

static int try_to_unmap_nonlinear(struct page *page,
		struct address_space *mapping, void *arg)
{
	struct vm_area_struct *vma;
	int ret = SWAP_AGAIN;
	unsigned long cursor;
	unsigned long max_nl_cursor = 0;
	unsigned long max_nl_size = 0;
	unsigned int mapcount;

	list_for_each_entry(vma,
		&mapping->i_mmap_nonlinear, shared.nonlinear) {

		cursor = (unsigned long) vma->vm_private_data;
		if (cursor > max_nl_cursor)
			max_nl_cursor = cursor;
		cursor = vma->vm_end - vma->vm_start;
		if (cursor > max_nl_size)
			max_nl_size = cursor;
	}

	if (max_nl_size == 0) {	/* all nonlinears locked or reserved ? */
		return SWAP_FAIL;
	}

	/*
	 * We don't try to search for this page in the nonlinear vmas,
	 * and page_referenced wouldn't have found it anyway.  Instead
	 * just walk the nonlinear vmas trying to age and unmap some.
	 * The mapcount of the page we came in with is irrelevant,
	 * but even so use it as a guide to how hard we should try?
	 */
	mapcount = page_mapcount(page);
	if (!mapcount)
		return ret;

	cond_resched();

	max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
	if (max_nl_cursor == 0)
		max_nl_cursor = CLUSTER_SIZE;

	do {
		list_for_each_entry(vma,
			&mapping->i_mmap_nonlinear, shared.nonlinear) {

			cursor = (unsigned long) vma->vm_private_data;
			while (cursor < max_nl_cursor &&
				cursor < vma->vm_end - vma->vm_start) {
				if (try_to_unmap_cluster(cursor, &mapcount,
						vma, page) == SWAP_MLOCK)
					ret = SWAP_MLOCK;
				cursor += CLUSTER_SIZE;
				vma->vm_private_data = (void *) cursor;
				if ((int)mapcount <= 0)
					return ret;
			}
			vma->vm_private_data = (void *) max_nl_cursor;
		}
		cond_resched();
		max_nl_cursor += CLUSTER_SIZE;
	} while (max_nl_cursor <= max_nl_size);

	/*
	 * Don't loop forever (perhaps all the remaining pages are
	 * in locked vmas).  Reset cursor on all unreserved nonlinear
	 * vmas, now forgetting on which ones it had fallen behind.
	 */
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
		vma->vm_private_data = NULL;

	return ret;
}

Project: linux
File: rmap.c

int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
		     unsigned long address, void *arg)
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte;
	pte_t pteval;
	spinlock_t *ptl;
	int ret = SWAP_AGAIN;
	enum ttu_flags flags = (enum ttu_flags)arg;

	pte = page_check_address(page, mm, address, &ptl, 0);
	if (!pte)
		goto out;

	/*
	 * If the page is mlock()d, we cannot swap it out.
	 * If it's recently referenced (perhaps page_referenced
	 * skipped over this mm) then we should reactivate it.
	 */
	if (!(flags & TTU_IGNORE_MLOCK)) {
		if (vma->vm_flags & VM_LOCKED)
			goto out_mlock;

		if (TTU_ACTION(flags) == TTU_MUNLOCK)
			goto out_unmap;
	}
	if (!(flags & TTU_IGNORE_ACCESS)) {
		if (ptep_clear_flush_young_notify(vma, address, pte)) {
			ret = SWAP_FAIL;
			goto out_unmap;
		}
  	}

	/* Nuke the page table entry. */
	flush_cache_page(vma, address, page_to_pfn(page));
	pteval = ptep_clear_flush(vma, address, pte);

	/* Move the dirty bit to the physical page now the pte is gone. */
	if (pte_dirty(pteval))
		set_page_dirty(page);

	/* Update high watermark before we lower rss */
	update_hiwater_rss(mm);

	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
		if (!PageHuge(page)) {
			if (PageAnon(page))
				dec_mm_counter(mm, MM_ANONPAGES);
			else
				dec_mm_counter(mm, MM_FILEPAGES);
		}
		set_pte_at(mm, address, pte,
			   swp_entry_to_pte(make_hwpoison_entry(page)));
	} else if (pte_unused(pteval)) {
		/*
		 * The guest indicated that the page content is of no
		 * interest anymore. Simply discard the pte, vmscan
		 * will take care of the rest.
		 */
		if (PageAnon(page))
			dec_mm_counter(mm, MM_ANONPAGES);
		else
			dec_mm_counter(mm, MM_FILEPAGES);
	} else if (PageAnon(page)) {
		swp_entry_t entry = { .val = page_private(page) };
		pte_t swp_pte;

		if (PageSwapCache(page)) {
			/*
			 * Store the swap location in the pte.
			 * See handle_pte_fault() ...
			 */
			if (swap_duplicate(entry) < 0) {
				set_pte_at(mm, address, pte, pteval);
				ret = SWAP_FAIL;
				goto out_unmap;
			}
			if (list_empty(&mm->mmlist)) {
				spin_lock(&mmlist_lock);
				if (list_empty(&mm->mmlist))
					list_add(&mm->mmlist, &init_mm.mmlist);
				spin_unlock(&mmlist_lock);
			}
			dec_mm_counter(mm, MM_ANONPAGES);
			inc_mm_counter(mm, MM_SWAPENTS);
		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
			/*
			 * Store the pfn of the page in a special migration
			 * pte. do_swap_page() will wait until the migration
			 * pte is removed and then restart fault handling.
			 */
			BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
			entry = make_migration_entry(page, pte_write(pteval));
		}
		swp_pte = swp_entry_to_pte(entry);
		if (pte_soft_dirty(pteval))
			swp_pte = pte_swp_mksoft_dirty(swp_pte);
		set_pte_at(mm, address, pte, swp_pte);
		BUG_ON(pte_file(*pte));
	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
		   (TTU_ACTION(flags) == TTU_MIGRATION)) {
		/* Establish migration entry for a file page */
		swp_entry_t entry;
		entry = make_migration_entry(page, pte_write(pteval));
		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
	} else
		dec_mm_counter(mm, MM_FILEPAGES);

	page_remove_rmap(page);
	page_cache_release(page);

out_unmap:
	pte_unmap_unlock(pte, ptl);
	if (ret != SWAP_FAIL)
		mmu_notifier_invalidate_page(mm, address);
out:
	return ret;

out_mlock:
	pte_unmap_unlock(pte, ptl);


	/*
	 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
	 * unstable result and race. Plus, We can't wait here because
	 * we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
	 * if trylock failed, the page remain in evictable lru and later
	 * vmscan could retry to move the page to unevictable lru if the
	 * page is actually mlocked.
	 */
	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
		if (vma->vm_flags & VM_LOCKED) {
			mlock_vma_page(page);
			ret = SWAP_MLOCK;
		}
		up_read(&vma->vm_mm->mmap_sem);
	}
	return ret;
}

Project: linux
File: rmap.c

void unlink_anon_vmas(struct vm_area_struct *vma)
{
	struct anon_vma_chain *avc, *next;
	struct anon_vma *root = NULL;

	/*
	 * Unlink each anon_vma chained to the VMA.  This list is ordered
	 * from newest to oldest, ensuring the root anon_vma gets freed last.
	 */
	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
		struct anon_vma *anon_vma = avc->anon_vma;

		root = lock_anon_vma_root(root, anon_vma);
		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);

		/*
		 * Leave empty anon_vmas on the list - we'll need
		 * to free them outside the lock.
		 */
		if (RB_EMPTY_ROOT(&anon_vma->rb_root))
			continue;

		list_del(&avc->same_vma);
		anon_vma_chain_free(avc);
	}
	unlock_anon_vma_root(root);

	/*
	 * Iterate the list once more, it now only contains empty and unlinked
	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
	 * needing to write-acquire the anon_vma->root->rwsem.
	 */
	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
		struct anon_vma *anon_vma = avc->anon_vma;

		put_anon_vma(anon_vma);

		list_del(&avc->same_vma);
		anon_vma_chain_free(avc);
	}
}

Project: linux
File: rmap.c

static inline void unlock_anon_vma_root(struct anon_vma *root)
{
	if (root)
		up_write(&root->rwsem);
}

Project: linux
File: rmap.c

vma_address(struct page *page, struct vm_area_struct *vma)
{
	unsigned long address = __vma_address(page, vma);

	/* page should be within @vma mapping range */
	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);

	return address;
}