rmap.c 51.4 KB
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/*
 * mm/rmap.c - physical to virtual reverse mappings
 *
 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
 * Released under the General Public License (GPL).
 *
 * Simple, low overhead reverse mapping scheme.
 * Please try to keep this thing as modular as possible.
 *
 * Provides methods for unmapping each kind of mapped page:
 * the anon methods track anonymous pages, and
 * the file methods track pages belonging to an inode.
 *
 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
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 * Contributions by Hugh Dickins 2003, 2004
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 */

/*
 * Lock ordering in mm:
 *
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 * inode->i_mutex	(while writing or truncating, not reading or faulting)
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 *   mm->mmap_sem
 *     page->flags PG_locked (lock_page)
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 *       mapping->i_mmap_mutex
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 *         anon_vma->rwsem
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 *           mm->page_table_lock or pte_lock
 *             zone->lru_lock (in mark_page_accessed, isolate_lru_page)
 *             swap_lock (in swap_duplicate, swap_info_get)
 *               mmlist_lock (in mmput, drain_mmlist and others)
 *               mapping->private_lock (in __set_page_dirty_buffers)
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 *               inode->i_lock (in set_page_dirty's __mark_inode_dirty)
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 *               bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
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 *                 sb_lock (within inode_lock in fs/fs-writeback.c)
 *                 mapping->tree_lock (widely used, in set_page_dirty,
 *                           in arch-dependent flush_dcache_mmap_lock,
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 *                           within bdi.wb->list_lock in __sync_single_inode)
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 *
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 * anon_vma->rwsem,mapping->i_mutex      (memory_failure, collect_procs_anon)
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 *   ->tasklist_lock
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 *     pte map lock
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 */

#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/slab.h>
#include <linux/init.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
#include <linux/rcupdate.h>
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#include <linux/export.h>
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#include <linux/memcontrol.h>
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#include <linux/mmu_notifier.h>
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#include <linux/migrate.h>
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#include <linux/hugetlb.h>
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#include <linux/backing-dev.h>
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#include <asm/tlbflush.h>

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#include "internal.h"

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static struct kmem_cache *anon_vma_cachep;
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static struct kmem_cache *anon_vma_chain_cachep;
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static inline struct anon_vma *anon_vma_alloc(void)
{
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	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;
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}

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static inline void anon_vma_free(struct anon_vma *anon_vma)
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{
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	VM_BUG_ON(atomic_read(&anon_vma->refcount));
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	/*
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	 * Synchronize against page_lock_anon_vma_read() such that
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	 * 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
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	 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
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	 *
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	 * page_lock_anon_vma_read()	VS	put_anon_vma()
	 *   down_read_trylock()		  atomic_dec_and_test()
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	 *   LOCK				  MB
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	 *   atomic_read()			  rwsem_is_locked()
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	 *
	 * LOCK should suffice since the actual taking of the lock must
	 * happen _before_ what follows.
	 */
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	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
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		anon_vma_lock_write(anon_vma);
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		anon_vma_unlock(anon_vma);
	}

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

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

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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);
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	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
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}

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/**
 * anon_vma_prepare - attach an anon_vma to a memory region
 * @vma: the memory region in question
 *
 * This makes sure the memory mapping described by 'vma' has
 * an 'anon_vma' attached to it, so that we can associate the
 * anonymous pages mapped into it with that anon_vma.
 *
 * The common case will be that we already have one, but if
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 * not we either need to find an adjacent mapping that we
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 * can re-use the anon_vma from (very common when the only
 * reason for splitting a vma has been mprotect()), or we
 * allocate a new one.
 *
 * Anon-vma allocations are very subtle, because we may have
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 * optimistically looked up an anon_vma in page_lock_anon_vma_read()
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 * and that may actually touch the spinlock even in the newly
 * allocated vma (it depends on RCU to make sure that the
 * anon_vma isn't actually destroyed).
 *
 * As a result, we need to do proper anon_vma locking even
 * for the new allocation. At the same time, we do not want
 * to do any locking for the common case of already having
 * an anon_vma.
 *
 * This must be called with the mmap_sem held for reading.
 */
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int anon_vma_prepare(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
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	struct anon_vma_chain *avc;
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	might_sleep();
	if (unlikely(!anon_vma)) {
		struct mm_struct *mm = vma->vm_mm;
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		struct anon_vma *allocated;
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		avc = anon_vma_chain_alloc(GFP_KERNEL);
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		if (!avc)
			goto out_enomem;

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

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		anon_vma_lock_write(anon_vma);
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		/* page_table_lock to protect against threads */
		spin_lock(&mm->page_table_lock);
		if (likely(!vma->anon_vma)) {
			vma->anon_vma = anon_vma;
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			anon_vma_chain_link(vma, avc, anon_vma);
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			allocated = NULL;
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			avc = NULL;
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		}
		spin_unlock(&mm->page_table_lock);
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		anon_vma_unlock(anon_vma);
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		if (unlikely(allocated))
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			put_anon_vma(allocated);
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		if (unlikely(avc))
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			anon_vma_chain_free(avc);
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	}
	return 0;
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 out_enomem_free_avc:
	anon_vma_chain_free(avc);
 out_enomem:
	return -ENOMEM;
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}

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/*
 * This is a useful helper function for locking the anon_vma root as
 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
 * have the same vma.
 *
 * Such anon_vma's should have the same root, so you'd expect to see
 * just a single mutex_lock for the whole traversal.
 */
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))
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			up_write(&root->rwsem);
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		root = new_root;
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		down_write(&root->rwsem);
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	}
	return root;
}

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

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/*
 * Attach the anon_vmas from src to dst.
 * Returns 0 on success, -ENOMEM on failure.
 */
int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
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{
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	struct anon_vma_chain *avc, *pavc;
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	struct anon_vma *root = NULL;
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	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
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		struct anon_vma *anon_vma;

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		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;
		}
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		anon_vma = pavc->anon_vma;
		root = lock_anon_vma_root(root, anon_vma);
		anon_vma_chain_link(dst, avc, anon_vma);
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	}
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	unlock_anon_vma_root(root);
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	return 0;
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 enomem_failure:
	unlink_anon_vmas(dst);
	return -ENOMEM;
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}

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/*
 * Attach vma to its own anon_vma, as well as to the anon_vmas that
 * the corresponding VMA in the parent process is attached to.
 * Returns 0 on success, non-zero on failure.
 */
int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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{
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	struct anon_vma_chain *avc;
	struct anon_vma *anon_vma;
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	/* 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;
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	avc = anon_vma_chain_alloc(GFP_KERNEL);
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	if (!avc)
		goto out_error_free_anon_vma;
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	/*
	 * 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;
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	/*
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	 * 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.
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	 */
	get_anon_vma(anon_vma->root);
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	/* Mark this anon_vma as the one where our new (COWed) pages go. */
	vma->anon_vma = anon_vma;
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	anon_vma_lock_write(anon_vma);
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	anon_vma_chain_link(vma, avc, anon_vma);
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	anon_vma_unlock(anon_vma);
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	return 0;

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

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

		root = lock_anon_vma_root(root, anon_vma);
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		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
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		/*
		 * Leave empty anon_vmas on the list - we'll need
		 * to free them outside the lock.
		 */
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		if (RB_EMPTY_ROOT(&anon_vma->rb_root))
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			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()
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	 * needing to write-acquire the anon_vma->root->rwsem.
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	 */
	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);

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

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static void anon_vma_ctor(void *data)
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{
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	struct anon_vma *anon_vma = data;
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	init_rwsem(&anon_vma->rwsem);
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	atomic_set(&anon_vma->refcount, 0);
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	anon_vma->rb_root = RB_ROOT;
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}

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

/*
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 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
 *
 * Since there is no serialization what so ever against page_remove_rmap()
 * the best this function can do is return a locked anon_vma that might
 * have been relevant to this page.
 *
 * The page might have been remapped to a different anon_vma or the anon_vma
 * returned may already be freed (and even reused).
 *
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 * In case it was remapped to a different anon_vma, the new anon_vma will be a
 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
 * ensure that any anon_vma obtained from the page will still be valid for as
 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
 *
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 * All users of this function must be very careful when walking the anon_vma
 * chain and verify that the page in question is indeed mapped in it
 * [ something equivalent to page_mapped_in_vma() ].
 *
 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
 * that the anon_vma pointer from page->mapping is valid if there is a
 * mapcount, we can dereference the anon_vma after observing those.
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 */
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struct anon_vma *page_get_anon_vma(struct page *page)
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{
405
	struct anon_vma *anon_vma = NULL;
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	unsigned long anon_mapping;

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

	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
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	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
		anon_vma = NULL;
		goto out;
	}
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	/*
	 * If this page is still mapped, then its anon_vma cannot have been
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	 * 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).
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	 */
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	if (!page_mapped(page)) {
		put_anon_vma(anon_vma);
		anon_vma = NULL;
	}
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out:
	rcu_read_unlock();
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	return anon_vma;
}

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/*
 * Similar to page_get_anon_vma() except it locks the anon_vma.
 *
 * Its a little more complex as it tries to keep the fast path to a single
 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
 * reference like with page_get_anon_vma() and then block on the mutex.
 */
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struct anon_vma *page_lock_anon_vma_read(struct page *page)
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{
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	struct anon_vma *anon_vma = NULL;
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	struct anon_vma *root_anon_vma;
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	unsigned long anon_mapping;
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	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);
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	root_anon_vma = ACCESS_ONCE(anon_vma->root);
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	if (down_read_trylock(&root_anon_vma->rwsem)) {
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		/*
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		 * If the page is still mapped, then this anon_vma is still
		 * its anon_vma, and holding the mutex ensures that it will
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		 * not go away, see anon_vma_free().
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		 */
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		if (!page_mapped(page)) {
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			up_read(&root_anon_vma->rwsem);
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			anon_vma = NULL;
		}
		goto out;
	}
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	/* 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();
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	anon_vma_lock_read(anon_vma);
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	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
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		 * we'll deadlock on the anon_vma_lock_write() recursion.
494
		 */
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		anon_vma_unlock_read(anon_vma);
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		__put_anon_vma(anon_vma);
		anon_vma = NULL;
	}

	return anon_vma;

out:
	rcu_read_unlock();
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	return anon_vma;
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}

507
void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
508
{
509
	anon_vma_unlock_read(anon_vma);
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}

/*
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 * At what user virtual address is page expected in @vma?
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 */
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static inline unsigned long
__vma_address(struct page *page, struct vm_area_struct *vma)
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{
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

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	if (unlikely(is_vm_hugetlb_page(vma)))
		pgoff = page->index << huge_page_order(page_hstate(page));
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	return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
}

inline unsigned long
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);

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	return address;
}

/*
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 * At what user virtual address is page expected in vma?
539
 * Caller should check the page is actually part of the vma.
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540 541 542
 */
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
543
	unsigned long address;
544
	if (PageAnon(page)) {
545 546 547 548 549 550 551
		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)
552 553
			return -EFAULT;
	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
H
Hugh Dickins 已提交
554 555
		if (!vma->vm_file ||
		    vma->vm_file->f_mapping != page->mapping)
L
Linus Torvalds 已提交
556 557 558
			return -EFAULT;
	} else
		return -EFAULT;
559 560 561 562
	address = __vma_address(page, vma);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
		return -EFAULT;
	return address;
L
Linus Torvalds 已提交
563 564
}

N
Nikita Danilov 已提交
565 566 567
/*
 * Check that @page is mapped at @address into @mm.
 *
N
Nick Piggin 已提交
568 569 570 571
 * If @sync is false, page_check_address may perform a racy check to avoid
 * the page table lock when the pte is not present (helpful when reclaiming
 * highly shared pages).
 *
572
 * On success returns with pte mapped and locked.
N
Nikita Danilov 已提交
573
 */
574
pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
N
Nick Piggin 已提交
575
			  unsigned long address, spinlock_t **ptlp, int sync)
N
Nikita Danilov 已提交
576 577 578 579 580
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
H
Hugh Dickins 已提交
581
	spinlock_t *ptl;
N
Nikita Danilov 已提交
582

583 584 585 586 587 588
	if (unlikely(PageHuge(page))) {
		pte = huge_pte_offset(mm, address);
		ptl = &mm->page_table_lock;
		goto check;
	}

N
Nikita Danilov 已提交
589
	pgd = pgd_offset(mm, address);
H
Hugh Dickins 已提交
590 591 592 593 594 595 596 597 598 599
	if (!pgd_present(*pgd))
		return NULL;

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		return NULL;

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return NULL;
600 601
	if (pmd_trans_huge(*pmd))
		return NULL;
H
Hugh Dickins 已提交
602 603 604

	pte = pte_offset_map(pmd, address);
	/* Make a quick check before getting the lock */
N
Nick Piggin 已提交
605
	if (!sync && !pte_present(*pte)) {
H
Hugh Dickins 已提交
606 607 608 609
		pte_unmap(pte);
		return NULL;
	}

H
Hugh Dickins 已提交
610
	ptl = pte_lockptr(mm, pmd);
611
check:
H
Hugh Dickins 已提交
612 613 614 615
	spin_lock(ptl);
	if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
		*ptlp = ptl;
		return pte;
N
Nikita Danilov 已提交
616
	}
H
Hugh Dickins 已提交
617 618
	pte_unmap_unlock(pte, ptl);
	return NULL;
N
Nikita Danilov 已提交
619 620
}

N
Nick Piggin 已提交
621 622 623 624 625 626 627 628 629
/**
 * page_mapped_in_vma - check whether a page is really mapped in a VMA
 * @page: the page to test
 * @vma: the VMA to test
 *
 * Returns 1 if the page is mapped into the page tables of the VMA, 0
 * if the page is not mapped into the page tables of this VMA.  Only
 * valid for normal file or anonymous VMAs.
 */
630
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
N
Nick Piggin 已提交
631 632 633 634 635
{
	unsigned long address;
	pte_t *pte;
	spinlock_t *ptl;

636 637
	address = __vma_address(page, vma);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
N
Nick Piggin 已提交
638 639 640 641 642 643 644 645 646
		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;
}

L
Linus Torvalds 已提交
647 648 649 650
/*
 * Subfunctions of page_referenced: page_referenced_one called
 * repeatedly from either page_referenced_anon or page_referenced_file.
 */
H
Hugh Dickins 已提交
651 652 653
int page_referenced_one(struct page *page, struct vm_area_struct *vma,
			unsigned long address, unsigned int *mapcount,
			unsigned long *vm_flags)
L
Linus Torvalds 已提交
654 655 656 657
{
	struct mm_struct *mm = vma->vm_mm;
	int referenced = 0;

658 659 660 661
	if (unlikely(PageTransHuge(page))) {
		pmd_t *pmd;

		spin_lock(&mm->page_table_lock);
662 663 664 665
		/*
		 * rmap might return false positives; we must filter
		 * these out using page_check_address_pmd().
		 */
666 667
		pmd = page_check_address_pmd(page, mm, address,
					     PAGE_CHECK_ADDRESS_PMD_FLAG);
668 669 670 671 672 673 674 675 676 677 678 679 680 681
		if (!pmd) {
			spin_unlock(&mm->page_table_lock);
			goto out;
		}

		if (vma->vm_flags & VM_LOCKED) {
			spin_unlock(&mm->page_table_lock);
			*mapcount = 0;	/* break early from loop */
			*vm_flags |= VM_LOCKED;
			goto out;
		}

		/* go ahead even if the pmd is pmd_trans_splitting() */
		if (pmdp_clear_flush_young_notify(vma, address, pmd))
682 683 684 685 686 687
			referenced++;
		spin_unlock(&mm->page_table_lock);
	} else {
		pte_t *pte;
		spinlock_t *ptl;

688 689 690 691
		/*
		 * rmap might return false positives; we must filter
		 * these out using page_check_address().
		 */
692 693 694 695
		pte = page_check_address(page, mm, address, &ptl, 0);
		if (!pte)
			goto out;

696 697 698 699 700 701 702
		if (vma->vm_flags & VM_LOCKED) {
			pte_unmap_unlock(pte, ptl);
			*mapcount = 0;	/* break early from loop */
			*vm_flags |= VM_LOCKED;
			goto out;
		}

703 704 705 706 707 708 709 710 711 712 713 714 715 716
		if (ptep_clear_flush_young_notify(vma, address, pte)) {
			/*
			 * Don't treat a reference through a sequentially read
			 * mapping as such.  If the page has been used in
			 * another mapping, we will catch it; if this other
			 * mapping is already gone, the unmap path will have
			 * set PG_referenced or activated the page.
			 */
			if (likely(!VM_SequentialReadHint(vma)))
				referenced++;
		}
		pte_unmap_unlock(pte, ptl);
	}

H
Hugh Dickins 已提交
717
	(*mapcount)--;
718

719 720
	if (referenced)
		*vm_flags |= vma->vm_flags;
721
out:
L
Linus Torvalds 已提交
722 723 724
	return referenced;
}

725
static int page_referenced_anon(struct page *page,
726
				struct mem_cgroup *memcg,
727
				unsigned long *vm_flags)
L
Linus Torvalds 已提交
728 729 730
{
	unsigned int mapcount;
	struct anon_vma *anon_vma;
731
	pgoff_t pgoff;
732
	struct anon_vma_chain *avc;
L
Linus Torvalds 已提交
733 734
	int referenced = 0;

735
	anon_vma = page_lock_anon_vma_read(page);
L
Linus Torvalds 已提交
736 737 738 739
	if (!anon_vma)
		return referenced;

	mapcount = page_mapcount(page);
740 741
	pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
742
		struct vm_area_struct *vma = avc->vma;
H
Hugh Dickins 已提交
743
		unsigned long address = vma_address(page, vma);
744 745 746 747 748
		/*
		 * If we are reclaiming on behalf of a cgroup, skip
		 * counting on behalf of references from different
		 * cgroups
		 */
749
		if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
750
			continue;
H
Hugh Dickins 已提交
751
		referenced += page_referenced_one(page, vma, address,
752
						  &mapcount, vm_flags);
L
Linus Torvalds 已提交
753 754 755
		if (!mapcount)
			break;
	}
756

757
	page_unlock_anon_vma_read(anon_vma);
L
Linus Torvalds 已提交
758 759 760 761 762 763
	return referenced;
}

/**
 * page_referenced_file - referenced check for object-based rmap
 * @page: the page we're checking references on.
764
 * @memcg: target memory control group
765
 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
L
Linus Torvalds 已提交
766 767 768 769 770 771 772 773
 *
 * For an object-based mapped page, find all the places it is mapped and
 * check/clear the referenced flag.  This is done by following the page->mapping
 * pointer, then walking the chain of vmas it holds.  It returns the number
 * of references it found.
 *
 * This function is only called from page_referenced for object-based pages.
 */
774
static int page_referenced_file(struct page *page,
775
				struct mem_cgroup *memcg,
776
				unsigned long *vm_flags)
L
Linus Torvalds 已提交
777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794
{
	unsigned int mapcount;
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	int referenced = 0;

	/*
	 * The caller's checks on page->mapping and !PageAnon have made
	 * sure that this is a file page: the check for page->mapping
	 * excludes the case just before it gets set on an anon page.
	 */
	BUG_ON(PageAnon(page));

	/*
	 * The page lock not only makes sure that page->mapping cannot
	 * suddenly be NULLified by truncation, it makes sure that the
	 * structure at mapping cannot be freed and reused yet,
795
	 * so we can safely take mapping->i_mmap_mutex.
L
Linus Torvalds 已提交
796 797 798
	 */
	BUG_ON(!PageLocked(page));

799
	mutex_lock(&mapping->i_mmap_mutex);
L
Linus Torvalds 已提交
800 801

	/*
802
	 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
L
Linus Torvalds 已提交
803 804 805 806
	 * is more likely to be accurate if we note it after spinning.
	 */
	mapcount = page_mapcount(page);

807
	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
808
		unsigned long address = vma_address(page, vma);
809 810 811 812 813
		/*
		 * If we are reclaiming on behalf of a cgroup, skip
		 * counting on behalf of references from different
		 * cgroups
		 */
814
		if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
815
			continue;
H
Hugh Dickins 已提交
816
		referenced += page_referenced_one(page, vma, address,
817
						  &mapcount, vm_flags);
L
Linus Torvalds 已提交
818 819 820 821
		if (!mapcount)
			break;
	}

822
	mutex_unlock(&mapping->i_mmap_mutex);
L
Linus Torvalds 已提交
823 824 825 826 827 828 829
	return referenced;
}

/**
 * page_referenced - test if the page was referenced
 * @page: the page to test
 * @is_locked: caller holds lock on the page
830
 * @memcg: target memory cgroup
831
 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
L
Linus Torvalds 已提交
832 833 834 835
 *
 * Quick test_and_clear_referenced for all mappings to a page,
 * returns the number of ptes which referenced the page.
 */
836 837
int page_referenced(struct page *page,
		    int is_locked,
838
		    struct mem_cgroup *memcg,
839
		    unsigned long *vm_flags)
L
Linus Torvalds 已提交
840 841
{
	int referenced = 0;
H
Hugh Dickins 已提交
842
	int we_locked = 0;
L
Linus Torvalds 已提交
843

844
	*vm_flags = 0;
H
Hugh Dickins 已提交
845
	if (page_mapped(page) && page_rmapping(page)) {
H
Hugh Dickins 已提交
846 847 848 849 850 851 852 853
		if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
			we_locked = trylock_page(page);
			if (!we_locked) {
				referenced++;
				goto out;
			}
		}
		if (unlikely(PageKsm(page)))
854
			referenced += page_referenced_ksm(page, memcg,
H
Hugh Dickins 已提交
855 856
								vm_flags);
		else if (PageAnon(page))
857
			referenced += page_referenced_anon(page, memcg,
858
								vm_flags);
H
Hugh Dickins 已提交
859
		else if (page->mapping)
860
			referenced += page_referenced_file(page, memcg,
861
								vm_flags);
H
Hugh Dickins 已提交
862
		if (we_locked)
L
Linus Torvalds 已提交
863
			unlock_page(page);
864 865 866

		if (page_test_and_clear_young(page_to_pfn(page)))
			referenced++;
L
Linus Torvalds 已提交
867
	}
H
Hugh Dickins 已提交
868
out:
L
Linus Torvalds 已提交
869 870 871
	return referenced;
}

H
Hugh Dickins 已提交
872 873
static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
			    unsigned long address)
874 875
{
	struct mm_struct *mm = vma->vm_mm;
876
	pte_t *pte;
877 878 879
	spinlock_t *ptl;
	int ret = 0;

N
Nick Piggin 已提交
880
	pte = page_check_address(page, mm, address, &ptl, 1);
881 882 883
	if (!pte)
		goto out;

884 885
	if (pte_dirty(*pte) || pte_write(*pte)) {
		pte_t entry;
886

887
		flush_cache_page(vma, address, pte_pfn(*pte));
888
		entry = ptep_clear_flush(vma, address, pte);
889 890
		entry = pte_wrprotect(entry);
		entry = pte_mkclean(entry);
891
		set_pte_at(mm, address, pte, entry);
892 893
		ret = 1;
	}
894 895

	pte_unmap_unlock(pte, ptl);
896 897 898

	if (ret)
		mmu_notifier_invalidate_page(mm, address);
899 900 901 902 903 904 905 906 907 908 909 910
out:
	return ret;
}

static int page_mkclean_file(struct address_space *mapping, struct page *page)
{
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	int ret = 0;

	BUG_ON(PageAnon(page));

911
	mutex_lock(&mapping->i_mmap_mutex);
912
	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
913 914 915 916
		if (vma->vm_flags & VM_SHARED) {
			unsigned long address = vma_address(page, vma);
			ret += page_mkclean_one(page, vma, address);
		}
917
	}
918
	mutex_unlock(&mapping->i_mmap_mutex);
919 920 921 922 923 924 925 926 927 928 929
	return ret;
}

int page_mkclean(struct page *page)
{
	int ret = 0;

	BUG_ON(!PageLocked(page));

	if (page_mapped(page)) {
		struct address_space *mapping = page_mapping(page);
930
		if (mapping)
931 932 933 934 935
			ret = page_mkclean_file(mapping, page);
	}

	return ret;
}
J
Jaya Kumar 已提交
936
EXPORT_SYMBOL_GPL(page_mkclean);
937

938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961
/**
 * page_move_anon_rmap - move a page to our anon_vma
 * @page:	the page to move to our anon_vma
 * @vma:	the vma the page belongs to
 * @address:	the user virtual address mapped
 *
 * When a page belongs exclusively to one process after a COW event,
 * that page can be moved into the anon_vma that belongs to just that
 * process, so the rmap code will not search the parent or sibling
 * processes.
 */
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(!PageLocked(page));
	VM_BUG_ON(!anon_vma);
	VM_BUG_ON(page->index != linear_page_index(vma, address));

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

N
Nick Piggin 已提交
962
/**
A
Andi Kleen 已提交
963 964 965 966
 * __page_set_anon_rmap - set up new anonymous rmap
 * @page:	Page to add to rmap	
 * @vma:	VM area to add page to.
 * @address:	User virtual address of the mapping	
967
 * @exclusive:	the page is exclusively owned by the current process
N
Nick Piggin 已提交
968 969
 */
static void __page_set_anon_rmap(struct page *page,
970
	struct vm_area_struct *vma, unsigned long address, int exclusive)
N
Nick Piggin 已提交
971
{
972
	struct anon_vma *anon_vma = vma->anon_vma;
973

974
	BUG_ON(!anon_vma);
975

A
Andi Kleen 已提交
976 977 978
	if (PageAnon(page))
		return;

979
	/*
980 981 982
	 * If the page isn't exclusively mapped into this vma,
	 * we must use the _oldest_ possible anon_vma for the
	 * page mapping!
983
	 */
A
Andi Kleen 已提交
984
	if (!exclusive)
985
		anon_vma = anon_vma->root;
N
Nick Piggin 已提交
986 987 988 989 990 991

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

N
Nick Piggin 已提交
992
/**
R
Randy Dunlap 已提交
993
 * __page_check_anon_rmap - sanity check anonymous rmap addition
N
Nick Piggin 已提交
994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013
 * @page:	the page to add the mapping to
 * @vma:	the vm area in which the mapping is added
 * @address:	the user virtual address mapped
 */
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.
	 */
A
Andrea Arcangeli 已提交
1014
	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
N
Nick Piggin 已提交
1015 1016 1017 1018
	BUG_ON(page->index != linear_page_index(vma, address));
#endif
}

L
Linus Torvalds 已提交
1019 1020 1021 1022 1023 1024
/**
 * page_add_anon_rmap - add pte mapping to an anonymous page
 * @page:	the page to add the mapping to
 * @vma:	the vm area in which the mapping is added
 * @address:	the user virtual address mapped
 *
H
Hugh Dickins 已提交
1025
 * The caller needs to hold the pte lock, and the page must be locked in
1026 1027 1028
 * the anon_vma case: to serialize mapping,index checking after setting,
 * and to ensure that PageAnon is not being upgraded racily to PageKsm
 * (but PageKsm is never downgraded to PageAnon).
L
Linus Torvalds 已提交
1029 1030 1031
 */
void page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042
{
	do_page_add_anon_rmap(page, vma, address, 0);
}

/*
 * Special version of the above for do_swap_page, which often runs
 * into pages that are exclusively owned by the current process.
 * Everybody else should continue to use page_add_anon_rmap above.
 */
void do_page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address, int exclusive)
L
Linus Torvalds 已提交
1043
{
H
Hugh Dickins 已提交
1044
	int first = atomic_inc_and_test(&page->_mapcount);
1045 1046 1047 1048 1049 1050 1051
	if (first) {
		if (!PageTransHuge(page))
			__inc_zone_page_state(page, NR_ANON_PAGES);
		else
			__inc_zone_page_state(page,
					      NR_ANON_TRANSPARENT_HUGEPAGES);
	}
H
Hugh Dickins 已提交
1052 1053 1054
	if (unlikely(PageKsm(page)))
		return;

N
Nick Piggin 已提交
1055
	VM_BUG_ON(!PageLocked(page));
1056
	/* address might be in next vma when migration races vma_adjust */
H
Hugh Dickins 已提交
1057
	if (first)
1058
		__page_set_anon_rmap(page, vma, address, exclusive);
1059
	else
N
Nick Piggin 已提交
1060
		__page_check_anon_rmap(page, vma, address);
L
Linus Torvalds 已提交
1061 1062
}

R
Randy Dunlap 已提交
1063
/**
N
Nick Piggin 已提交
1064 1065 1066 1067 1068 1069 1070
 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
 * @page:	the page to add the mapping to
 * @vma:	the vm area in which the mapping is added
 * @address:	the user virtual address mapped
 *
 * Same as page_add_anon_rmap but must only be called on *new* pages.
 * This means the inc-and-test can be bypassed.
N
Nick Piggin 已提交
1071
 * Page does not have to be locked.
N
Nick Piggin 已提交
1072 1073 1074 1075
 */
void page_add_new_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
1076
	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1077 1078
	SetPageSwapBacked(page);
	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1079 1080 1081 1082
	if (!PageTransHuge(page))
		__inc_zone_page_state(page, NR_ANON_PAGES);
	else
		__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1083
	__page_set_anon_rmap(page, vma, address, 1);
1084
	if (!mlocked_vma_newpage(vma, page))
1085
		lru_cache_add_lru(page, LRU_ACTIVE_ANON);
1086 1087
	else
		add_page_to_unevictable_list(page);
N
Nick Piggin 已提交
1088 1089
}

L
Linus Torvalds 已提交
1090 1091 1092 1093
/**
 * page_add_file_rmap - add pte mapping to a file page
 * @page: the page to add the mapping to
 *
1094
 * The caller needs to hold the pte lock.
L
Linus Torvalds 已提交
1095 1096 1097
 */
void page_add_file_rmap(struct page *page)
{
1098 1099 1100 1101
	bool locked;
	unsigned long flags;

	mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1102
	if (atomic_inc_and_test(&page->_mapcount)) {
1103
		__inc_zone_page_state(page, NR_FILE_MAPPED);
1104
		mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
1105
	}
1106
	mem_cgroup_end_update_page_stat(page, &locked, &flags);
L
Linus Torvalds 已提交
1107 1108 1109 1110 1111 1112
}

/**
 * page_remove_rmap - take down pte mapping from a page
 * @page: page to remove mapping from
 *
1113
 * The caller needs to hold the pte lock.
L
Linus Torvalds 已提交
1114
 */
1115
void page_remove_rmap(struct page *page)
L
Linus Torvalds 已提交
1116
{
1117
	struct address_space *mapping = page_mapping(page);
1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
	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);

1130 1131
	/* page still mapped by someone else? */
	if (!atomic_add_negative(-1, &page->_mapcount))
1132
		goto out;
1133 1134 1135 1136 1137 1138 1139

	/*
	 * Now that the last pte has gone, s390 must transfer dirty
	 * flag from storage key to struct page.  We can usually skip
	 * this if the page is anon, so about to be freed; but perhaps
	 * not if it's in swapcache - there might be another pte slot
	 * containing the swap entry, but page not yet written to swap.
1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150
	 *
	 * And we can skip it on file pages, so long as the filesystem
	 * participates in dirty tracking; but need to catch shm and tmpfs
	 * and ramfs pages which have been modified since creation by read
	 * fault.
	 *
	 * Note that mapping must be decided above, before decrementing
	 * mapcount (which luckily provides a barrier): once page is unmapped,
	 * it could be truncated and page->mapping reset to NULL at any moment.
	 * Note also that we are relying on page_mapping(page) to set mapping
	 * to &swapper_space when PageSwapCache(page).
1151
	 */
1152
	if (mapping && !mapping_cap_account_dirty(mapping) &&
1153
	    page_test_and_clear_dirty(page_to_pfn(page), 1))
1154
		set_page_dirty(page);
1155 1156 1157 1158 1159
	/*
	 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
	 * and not charged by memcg for now.
	 */
	if (unlikely(PageHuge(page)))
1160 1161
		goto out;
	if (anon) {
1162
		mem_cgroup_uncharge_page(page);
1163 1164 1165 1166 1167
		if (!PageTransHuge(page))
			__dec_zone_page_state(page, NR_ANON_PAGES);
		else
			__dec_zone_page_state(page,
					      NR_ANON_TRANSPARENT_HUGEPAGES);
1168 1169
	} else {
		__dec_zone_page_state(page, NR_FILE_MAPPED);
1170
		mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
1171
		mem_cgroup_end_update_page_stat(page, &locked, &flags);
1172
	}
1173 1174
	if (unlikely(PageMlocked(page)))
		clear_page_mlock(page);
1175 1176 1177 1178 1179 1180 1181 1182 1183
	/*
	 * 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.
	 */
1184
	return;
1185 1186 1187
out:
	if (!anon)
		mem_cgroup_end_update_page_stat(page, &locked, &flags);
L
Linus Torvalds 已提交
1188 1189 1190 1191
}

/*
 * Subfunctions of try_to_unmap: try_to_unmap_one called
1192
 * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
L
Linus Torvalds 已提交
1193
 */
H
Hugh Dickins 已提交
1194 1195
int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
		     unsigned long address, enum ttu_flags flags)
L
Linus Torvalds 已提交
1196 1197 1198 1199
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte;
	pte_t pteval;
H
Hugh Dickins 已提交
1200
	spinlock_t *ptl;
L
Linus Torvalds 已提交
1201 1202
	int ret = SWAP_AGAIN;

N
Nick Piggin 已提交
1203
	pte = page_check_address(page, mm, address, &ptl, 0);
H
Hugh Dickins 已提交
1204
	if (!pte)
N
Nikita Danilov 已提交
1205
		goto out;
L
Linus Torvalds 已提交
1206 1207 1208 1209 1210 1211

	/*
	 * 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.
	 */
1212
	if (!(flags & TTU_IGNORE_MLOCK)) {
K
KOSAKI Motohiro 已提交
1213 1214 1215
		if (vma->vm_flags & VM_LOCKED)
			goto out_mlock;

H
Hugh Dickins 已提交
1216
		if (TTU_ACTION(flags) == TTU_MUNLOCK)
H
Hugh Dickins 已提交
1217
			goto out_unmap;
1218 1219
	}
	if (!(flags & TTU_IGNORE_ACCESS)) {
N
Nick Piggin 已提交
1220 1221 1222 1223 1224
		if (ptep_clear_flush_young_notify(vma, address, pte)) {
			ret = SWAP_FAIL;
			goto out_unmap;
		}
  	}
L
Linus Torvalds 已提交
1225 1226 1227

	/* Nuke the page table entry. */
	flush_cache_page(vma, address, page_to_pfn(page));
1228
	pteval = ptep_clear_flush(vma, address, pte);
L
Linus Torvalds 已提交
1229 1230 1231 1232 1233

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

1234 1235 1236
	/* Update high watermark before we lower rss */
	update_hiwater_rss(mm);

1237 1238
	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
		if (PageAnon(page))
K
KAMEZAWA Hiroyuki 已提交
1239
			dec_mm_counter(mm, MM_ANONPAGES);
1240
		else
K
KAMEZAWA Hiroyuki 已提交
1241
			dec_mm_counter(mm, MM_FILEPAGES);
1242 1243 1244
		set_pte_at(mm, address, pte,
				swp_entry_to_pte(make_hwpoison_entry(page)));
	} else if (PageAnon(page)) {
H
Hugh Dickins 已提交
1245
		swp_entry_t entry = { .val = page_private(page) };
1246 1247 1248 1249 1250 1251

		if (PageSwapCache(page)) {
			/*
			 * Store the swap location in the pte.
			 * See handle_pte_fault() ...
			 */
H
Hugh Dickins 已提交
1252 1253 1254 1255 1256
			if (swap_duplicate(entry) < 0) {
				set_pte_at(mm, address, pte, pteval);
				ret = SWAP_FAIL;
				goto out_unmap;
			}
1257 1258 1259 1260 1261 1262
			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);
			}
K
KAMEZAWA Hiroyuki 已提交
1263
			dec_mm_counter(mm, MM_ANONPAGES);
K
KAMEZAWA Hiroyuki 已提交
1264
			inc_mm_counter(mm, MM_SWAPENTS);
1265
		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
1266 1267 1268 1269 1270
			/*
			 * 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.
			 */
1271
			BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1272
			entry = make_migration_entry(page, pte_write(pteval));
L
Linus Torvalds 已提交
1273 1274 1275
		}
		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
		BUG_ON(pte_file(*pte));
1276 1277
	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
		   (TTU_ACTION(flags) == TTU_MIGRATION)) {
1278 1279 1280 1281 1282
		/* 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
K
KAMEZAWA Hiroyuki 已提交
1283
		dec_mm_counter(mm, MM_FILEPAGES);
L
Linus Torvalds 已提交
1284

1285
	page_remove_rmap(page);
L
Linus Torvalds 已提交
1286 1287 1288
	page_cache_release(page);

out_unmap:
H
Hugh Dickins 已提交
1289
	pte_unmap_unlock(pte, ptl);
1290 1291
	if (ret != SWAP_FAIL)
		mmu_notifier_invalidate_page(mm, address);
K
KOSAKI Motohiro 已提交
1292 1293
out:
	return ret;
H
Hugh Dickins 已提交
1294

K
KOSAKI Motohiro 已提交
1295 1296 1297 1298 1299 1300 1301
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
1302
	 * we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
K
KOSAKI Motohiro 已提交
1303 1304 1305 1306 1307 1308 1309 1310
	 * 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;
H
Hugh Dickins 已提交
1311
		}
K
KOSAKI Motohiro 已提交
1312
		up_read(&vma->vm_mm->mmap_sem);
H
Hugh Dickins 已提交
1313
	}
L
Linus Torvalds 已提交
1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334
	return ret;
}

/*
 * objrmap doesn't work for nonlinear VMAs because the assumption that
 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
 * Consequently, given a particular page and its ->index, we cannot locate the
 * ptes which are mapping that page without an exhaustive linear search.
 *
 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
 * maps the file to which the target page belongs.  The ->vm_private_data field
 * holds the current cursor into that scan.  Successive searches will circulate
 * around the vma's virtual address space.
 *
 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
 * more scanning pressure is placed against them as well.   Eventually pages
 * will become fully unmapped and are eligible for eviction.
 *
 * For very sparsely populated VMAs this is a little inefficient - chances are
 * there there won't be many ptes located within the scan cluster.  In this case
 * maybe we could scan further - to the end of the pte page, perhaps.
N
Nick Piggin 已提交
1335 1336 1337 1338 1339
 *
 * Mlocked pages:  check VM_LOCKED under mmap_sem held for read, if we can
 * acquire it without blocking.  If vma locked, mlock the pages in the cluster,
 * rather than unmapping them.  If we encounter the "check_page" that vmscan is
 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
L
Linus Torvalds 已提交
1340 1341 1342 1343
 */
#define CLUSTER_SIZE	min(32*PAGE_SIZE, PMD_SIZE)
#define CLUSTER_MASK	(~(CLUSTER_SIZE - 1))

N
Nick Piggin 已提交
1344 1345
static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
		struct vm_area_struct *vma, struct page *check_page)
L
Linus Torvalds 已提交
1346 1347 1348 1349 1350
{
	struct mm_struct *mm = vma->vm_mm;
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
H
Hugh Dickins 已提交
1351
	pte_t *pte;
L
Linus Torvalds 已提交
1352
	pte_t pteval;
H
Hugh Dickins 已提交
1353
	spinlock_t *ptl;
L
Linus Torvalds 已提交
1354 1355
	struct page *page;
	unsigned long address;
1356 1357
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */
L
Linus Torvalds 已提交
1358
	unsigned long end;
N
Nick Piggin 已提交
1359 1360
	int ret = SWAP_AGAIN;
	int locked_vma = 0;
L
Linus Torvalds 已提交
1361 1362 1363 1364 1365 1366 1367 1368 1369 1370

	address = (vma->vm_start + cursor) & CLUSTER_MASK;
	end = address + CLUSTER_SIZE;
	if (address < vma->vm_start)
		address = vma->vm_start;
	if (end > vma->vm_end)
		end = vma->vm_end;

	pgd = pgd_offset(mm, address);
	if (!pgd_present(*pgd))
N
Nick Piggin 已提交
1371
		return ret;
L
Linus Torvalds 已提交
1372 1373 1374

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
N
Nick Piggin 已提交
1375
		return ret;
L
Linus Torvalds 已提交
1376 1377 1378

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
N
Nick Piggin 已提交
1379 1380
		return ret;

1381 1382 1383 1384
	mmun_start = address;
	mmun_end   = end;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

N
Nick Piggin 已提交
1385
	/*
H
Hugh Dickins 已提交
1386
	 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
N
Nick Piggin 已提交
1387 1388
	 * keep the sem while scanning the cluster for mlocking pages.
	 */
H
Hugh Dickins 已提交
1389
	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
N
Nick Piggin 已提交
1390 1391 1392 1393
		locked_vma = (vma->vm_flags & VM_LOCKED);
		if (!locked_vma)
			up_read(&vma->vm_mm->mmap_sem); /* don't need it */
	}
H
Hugh Dickins 已提交
1394 1395

	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
L
Linus Torvalds 已提交
1396

1397 1398 1399
	/* Update high watermark before we lower rss */
	update_hiwater_rss(mm);

H
Hugh Dickins 已提交
1400
	for (; address < end; pte++, address += PAGE_SIZE) {
L
Linus Torvalds 已提交
1401 1402
		if (!pte_present(*pte))
			continue;
1403 1404
		page = vm_normal_page(vma, address, *pte);
		BUG_ON(!page || PageAnon(page));
L
Linus Torvalds 已提交
1405

N
Nick Piggin 已提交
1406 1407 1408 1409 1410 1411 1412
		if (locked_vma) {
			mlock_vma_page(page);   /* no-op if already mlocked */
			if (page == check_page)
				ret = SWAP_MLOCK;
			continue;	/* don't unmap */
		}

A
Andrea Arcangeli 已提交
1413
		if (ptep_clear_flush_young_notify(vma, address, pte))
L
Linus Torvalds 已提交
1414 1415 1416
			continue;

		/* Nuke the page table entry. */
1417
		flush_cache_page(vma, address, pte_pfn(*pte));
1418
		pteval = ptep_clear_flush(vma, address, pte);
L
Linus Torvalds 已提交
1419 1420 1421 1422 1423 1424 1425 1426 1427

		/* If nonlinear, store the file page offset in the pte. */
		if (page->index != linear_page_index(vma, address))
			set_pte_at(mm, address, pte, pgoff_to_pte(page->index));

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

1428
		page_remove_rmap(page);
L
Linus Torvalds 已提交
1429
		page_cache_release(page);
K
KAMEZAWA Hiroyuki 已提交
1430
		dec_mm_counter(mm, MM_FILEPAGES);
L
Linus Torvalds 已提交
1431 1432
		(*mapcount)--;
	}
H
Hugh Dickins 已提交
1433
	pte_unmap_unlock(pte - 1, ptl);
1434
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
N
Nick Piggin 已提交
1435 1436 1437
	if (locked_vma)
		up_read(&vma->vm_mm->mmap_sem);
	return ret;
L
Linus Torvalds 已提交
1438 1439
}

1440
bool is_vma_temporary_stack(struct vm_area_struct *vma)
1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453
{
	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;
}

N
Nick Piggin 已提交
1454 1455 1456 1457
/**
 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
 * rmap method
 * @page: the page to unmap/unlock
1458
 * @flags: action and flags
N
Nick Piggin 已提交
1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469
 *
 * Find all the mappings of a page using the mapping pointer and the vma chains
 * contained in the anon_vma struct it points to.
 *
 * This function is only called from try_to_unmap/try_to_munlock for
 * anonymous pages.
 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
 * where the page was found will be held for write.  So, we won't recheck
 * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
 * 'LOCKED.
 */
1470
static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1471 1472
{
	struct anon_vma *anon_vma;
1473
	pgoff_t pgoff;
1474
	struct anon_vma_chain *avc;
L
Linus Torvalds 已提交
1475
	int ret = SWAP_AGAIN;
N
Nick Piggin 已提交
1476

1477
	anon_vma = page_lock_anon_vma_read(page);
L
Linus Torvalds 已提交
1478 1479 1480
	if (!anon_vma)
		return ret;

1481 1482
	pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1483
		struct vm_area_struct *vma = avc->vma;
1484 1485 1486 1487 1488 1489 1490 1491 1492 1493
		unsigned long address;

		/*
		 * 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.
		 */
1494
		if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1495 1496 1497 1498
				is_vma_temporary_stack(vma))
			continue;

		address = vma_address(page, vma);
H
Hugh Dickins 已提交
1499
		ret = try_to_unmap_one(page, vma, address, flags);
H
Hugh Dickins 已提交
1500 1501
		if (ret != SWAP_AGAIN || !page_mapped(page))
			break;
L
Linus Torvalds 已提交
1502
	}
1503

1504
	page_unlock_anon_vma_read(anon_vma);
L
Linus Torvalds 已提交
1505 1506 1507 1508
	return ret;
}

/**
N
Nick Piggin 已提交
1509 1510
 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
 * @page: the page to unmap/unlock
1511
 * @flags: action and flags
L
Linus Torvalds 已提交
1512 1513 1514 1515
 *
 * Find all the mappings of a page using the mapping pointer and the vma chains
 * contained in the address_space struct it points to.
 *
N
Nick Piggin 已提交
1516 1517 1518 1519 1520 1521
 * This function is only called from try_to_unmap/try_to_munlock for
 * object-based pages.
 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
 * where the page was found will be held for write.  So, we won't recheck
 * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
 * 'LOCKED.
L
Linus Torvalds 已提交
1522
 */
1523
static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1524 1525 1526 1527 1528 1529 1530 1531 1532 1533
{
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	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;

1534
	mutex_lock(&mapping->i_mmap_mutex);
1535
	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
1536 1537
		unsigned long address = vma_address(page, vma);
		ret = try_to_unmap_one(page, vma, address, flags);
H
Hugh Dickins 已提交
1538 1539
		if (ret != SWAP_AGAIN || !page_mapped(page))
			goto out;
L
Linus Torvalds 已提交
1540 1541 1542 1543 1544
	}

	if (list_empty(&mapping->i_mmap_nonlinear))
		goto out;

H
Hugh Dickins 已提交
1545 1546 1547 1548 1549 1550 1551 1552
	/*
	 * 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(TTU_MUNLOCK) and recover PG_mlocked lazily.
	 */
	if (TTU_ACTION(flags) == TTU_MUNLOCK)
		goto out;

L
Linus Torvalds 已提交
1553
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1554
							shared.nonlinear) {
L
Linus Torvalds 已提交
1555 1556 1557 1558 1559 1560 1561 1562
		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;
	}

N
Nick Piggin 已提交
1563
	if (max_nl_size == 0) {	/* all nonlinears locked or reserved ? */
L
Linus Torvalds 已提交
1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
		ret = SWAP_FAIL;
		goto out;
	}

	/*
	 * 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)
		goto out;
1578
	cond_resched();
L
Linus Torvalds 已提交
1579 1580 1581 1582 1583 1584 1585

	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,
1586
							shared.nonlinear) {
L
Linus Torvalds 已提交
1587
			cursor = (unsigned long) vma->vm_private_data;
H
Hugh Dickins 已提交
1588
			while ( cursor < max_nl_cursor &&
L
Linus Torvalds 已提交
1589
				cursor < vma->vm_end - vma->vm_start) {
H
Hugh Dickins 已提交
1590 1591 1592
				if (try_to_unmap_cluster(cursor, &mapcount,
						vma, page) == SWAP_MLOCK)
					ret = SWAP_MLOCK;
L
Linus Torvalds 已提交
1593 1594 1595 1596 1597 1598 1599
				cursor += CLUSTER_SIZE;
				vma->vm_private_data = (void *) cursor;
				if ((int)mapcount <= 0)
					goto out;
			}
			vma->vm_private_data = (void *) max_nl_cursor;
		}
1600
		cond_resched();
L
Linus Torvalds 已提交
1601 1602 1603 1604 1605 1606 1607 1608
		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.
	 */
1609
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
1610
		vma->vm_private_data = NULL;
L
Linus Torvalds 已提交
1611
out:
1612
	mutex_unlock(&mapping->i_mmap_mutex);
L
Linus Torvalds 已提交
1613 1614 1615 1616 1617 1618
	return ret;
}

/**
 * try_to_unmap - try to remove all page table mappings to a page
 * @page: the page to get unmapped
1619
 * @flags: action and flags
L
Linus Torvalds 已提交
1620 1621 1622 1623 1624 1625 1626 1627
 *
 * Tries to remove all the page table entries which are mapping this
 * page, used in the pageout path.  Caller must hold the page lock.
 * Return values are:
 *
 * SWAP_SUCCESS	- we succeeded in removing all mappings
 * SWAP_AGAIN	- we missed a mapping, try again later
 * SWAP_FAIL	- the page is unswappable
N
Nick Piggin 已提交
1628
 * SWAP_MLOCK	- page is mlocked.
L
Linus Torvalds 已提交
1629
 */
1630
int try_to_unmap(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1631 1632 1633 1634
{
	int ret;

	BUG_ON(!PageLocked(page));
1635
	VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
L
Linus Torvalds 已提交
1636

H
Hugh Dickins 已提交
1637 1638 1639
	if (unlikely(PageKsm(page)))
		ret = try_to_unmap_ksm(page, flags);
	else if (PageAnon(page))
1640
		ret = try_to_unmap_anon(page, flags);
L
Linus Torvalds 已提交
1641
	else
1642
		ret = try_to_unmap_file(page, flags);
N
Nick Piggin 已提交
1643
	if (ret != SWAP_MLOCK && !page_mapped(page))
L
Linus Torvalds 已提交
1644 1645 1646
		ret = SWAP_SUCCESS;
	return ret;
}
N
Nikita Danilov 已提交
1647

N
Nick Piggin 已提交
1648 1649 1650 1651 1652 1653 1654 1655 1656 1657
/**
 * try_to_munlock - try to munlock a page
 * @page: the page to be munlocked
 *
 * Called from munlock code.  Checks all of the VMAs mapping the page
 * to make sure nobody else has this page mlocked. The page will be
 * returned with PG_mlocked cleared if no other vmas have it mlocked.
 *
 * Return values are:
 *
H
Hugh Dickins 已提交
1658
 * SWAP_AGAIN	- no vma is holding page mlocked, or,
N
Nick Piggin 已提交
1659
 * SWAP_AGAIN	- page mapped in mlocked vma -- couldn't acquire mmap sem
H
Hugh Dickins 已提交
1660
 * SWAP_FAIL	- page cannot be located at present
N
Nick Piggin 已提交
1661 1662 1663 1664 1665 1666
 * SWAP_MLOCK	- page is now mlocked.
 */
int try_to_munlock(struct page *page)
{
	VM_BUG_ON(!PageLocked(page) || PageLRU(page));

H
Hugh Dickins 已提交
1667 1668 1669
	if (unlikely(PageKsm(page)))
		return try_to_unmap_ksm(page, TTU_MUNLOCK);
	else if (PageAnon(page))
1670
		return try_to_unmap_anon(page, TTU_MUNLOCK);
N
Nick Piggin 已提交
1671
	else
1672
		return try_to_unmap_file(page, TTU_MUNLOCK);
N
Nick Piggin 已提交
1673
}
1674

P
Peter Zijlstra 已提交
1675
void __put_anon_vma(struct anon_vma *anon_vma)
1676
{
P
Peter Zijlstra 已提交
1677
	struct anon_vma *root = anon_vma->root;
1678

P
Peter Zijlstra 已提交
1679 1680
	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
		anon_vma_free(root);
1681

P
Peter Zijlstra 已提交
1682
	anon_vma_free(anon_vma);
1683 1684
}

1685 1686 1687 1688 1689 1690 1691 1692 1693
#ifdef CONFIG_MIGRATION
/*
 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
 * Called by migrate.c to remove migration ptes, but might be used more later.
 */
static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
		struct vm_area_struct *, unsigned long, void *), void *arg)
{
	struct anon_vma *anon_vma;
1694
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1695
	struct anon_vma_chain *avc;
1696 1697 1698
	int ret = SWAP_AGAIN;

	/*
1699
	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1700
	 * because that depends on page_mapped(); but not all its usages
1701 1702
	 * are holding mmap_sem. Users without mmap_sem are required to
	 * take a reference count to prevent the anon_vma disappearing
1703 1704 1705 1706
	 */
	anon_vma = page_anon_vma(page);
	if (!anon_vma)
		return ret;
1707
	anon_vma_lock_read(anon_vma);
1708
	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1709
		struct vm_area_struct *vma = avc->vma;
1710 1711 1712 1713 1714
		unsigned long address = vma_address(page, vma);
		ret = rmap_one(page, vma, address, arg);
		if (ret != SWAP_AGAIN)
			break;
	}
1715
	anon_vma_unlock_read(anon_vma);
1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728
	return ret;
}

static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
		struct vm_area_struct *, unsigned long, void *), void *arg)
{
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	int ret = SWAP_AGAIN;

	if (!mapping)
		return ret;
1729
	mutex_lock(&mapping->i_mmap_mutex);
1730
	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1731 1732 1733 1734 1735 1736 1737 1738 1739 1740
		unsigned long address = vma_address(page, vma);
		ret = rmap_one(page, vma, address, arg);
		if (ret != SWAP_AGAIN)
			break;
	}
	/*
	 * No nonlinear handling: being always shared, nonlinear vmas
	 * never contain migration ptes.  Decide what to do about this
	 * limitation to linear when we need rmap_walk() on nonlinear.
	 */
1741
	mutex_unlock(&mapping->i_mmap_mutex);
1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757
	return ret;
}

int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
		struct vm_area_struct *, unsigned long, void *), void *arg)
{
	VM_BUG_ON(!PageLocked(page));

	if (unlikely(PageKsm(page)))
		return rmap_walk_ksm(page, rmap_one, arg);
	else if (PageAnon(page))
		return rmap_walk_anon(page, rmap_one, arg);
	else
		return rmap_walk_file(page, rmap_one, arg);
}
#endif /* CONFIG_MIGRATION */
1758

N
Naoya Horiguchi 已提交
1759
#ifdef CONFIG_HUGETLB_PAGE
1760 1761 1762 1763 1764 1765 1766 1767 1768
/*
 * The following three functions are for anonymous (private mapped) hugepages.
 * Unlike common anonymous pages, anonymous hugepages have no accounting code
 * and no lru code, because we handle hugepages differently from common pages.
 */
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;
1769

1770
	BUG_ON(!anon_vma);
1771 1772 1773 1774 1775 1776

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

1777 1778 1779 1780 1781 1782 1783 1784 1785 1786
	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	page->mapping = (struct address_space *) anon_vma;
	page->index = linear_page_index(vma, address);
}

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;
1787 1788

	BUG_ON(!PageLocked(page));
1789
	BUG_ON(!anon_vma);
1790
	/* address might be in next vma when migration races vma_adjust */
1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802
	first = atomic_inc_and_test(&page->_mapcount);
	if (first)
		__hugepage_set_anon_rmap(page, vma, address, 0);
}

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);
}
N
Naoya Horiguchi 已提交
1803
#endif /* CONFIG_HUGETLB_PAGE */