rmap.c 45.9 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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 *   inode->i_alloc_sem (vmtruncate_range)
 *   mm->mmap_sem
 *     page->flags PG_locked (lock_page)
 *       mapping->i_mmap_lock
 *         anon_vma->lock
 *           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)
 *               inode_lock (in set_page_dirty's __mark_inode_dirty)
 *                 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,
 *                           within inode_lock in __sync_single_inode)
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 *
 * (code doesn't rely on that order so it could be switched around)
 * ->tasklist_lock
 *   anon_vma->lock      (memory_failure, collect_procs_anon)
 *     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/module.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 <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)
{
	return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
}

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void anon_vma_free(struct anon_vma *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(void)
{
	return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL);
}

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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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/**
 * 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
 * optimistically looked up an anon_vma in page_lock_anon_vma()
 * 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();
		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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			/*
			 * This VMA had no anon_vma yet.  This anon_vma is
			 * the root of any anon_vma tree that might form.
			 */
			anon_vma->root = anon_vma;
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		}

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		anon_vma_lock(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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			avc->anon_vma = anon_vma;
			avc->vma = vma;
			list_add(&avc->same_vma, &vma->anon_vma_chain);
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			list_add_tail(&avc->same_anon_vma, &anon_vma->head);
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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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			anon_vma_free(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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static void anon_vma_chain_link(struct vm_area_struct *vma,
				struct anon_vma_chain *avc,
				struct anon_vma *anon_vma)
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{
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	avc->vma = vma;
	avc->anon_vma = anon_vma;
	list_add(&avc->same_vma, &vma->anon_vma_chain);

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	anon_vma_lock(anon_vma);
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	/*
	 * It's critical to add new vmas to the tail of the anon_vma,
	 * see comment in huge_memory.c:__split_huge_page().
	 */
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	list_add_tail(&avc->same_anon_vma, &anon_vma->head);
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	anon_vma_unlock(anon_vma);
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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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	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
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		avc = anon_vma_chain_alloc();
		if (!avc)
			goto enomem_failure;
		anon_vma_chain_link(dst, avc, pavc->anon_vma);
	}
	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;
	avc = anon_vma_chain_alloc();
	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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	/*
	 * With KSM 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);
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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_chain_link(vma, avc, anon_vma);
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	return 0;

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

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static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
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{
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	struct anon_vma *anon_vma = anon_vma_chain->anon_vma;
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	int empty;

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	/* If anon_vma_fork fails, we can get an empty anon_vma_chain. */
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	if (!anon_vma)
		return;

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	anon_vma_lock(anon_vma);
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	list_del(&anon_vma_chain->same_anon_vma);
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	/* We must garbage collect the anon_vma if it's empty */
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	empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
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	anon_vma_unlock(anon_vma);
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	if (empty) {
		/* We no longer need the root anon_vma */
		if (anon_vma->root != anon_vma)
			drop_anon_vma(anon_vma->root);
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		anon_vma_free(anon_vma);
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	}
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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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	/*
	 * 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) {
		anon_vma_unlink(avc);
		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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	spin_lock_init(&anon_vma->lock);
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	anonvma_external_refcount_init(anon_vma);
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	INIT_LIST_HEAD(&anon_vma->head);
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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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}

/*
 * Getting a lock on a stable anon_vma from a page off the LRU is
 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
 */
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struct anon_vma *__page_lock_anon_vma(struct page *page)
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{
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	struct anon_vma *anon_vma, *root_anon_vma;
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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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	root_anon_vma = ACCESS_ONCE(anon_vma->root);
	spin_lock(&root_anon_vma->lock);

	/*
	 * 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 spin_lock above cannot
	 * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting
	 * anon_vma->root before page_unlock_anon_vma() is called to unlock.
	 */
	if (page_mapped(page))
		return anon_vma;

	spin_unlock(&root_anon_vma->lock);
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out:
	rcu_read_unlock();
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	return NULL;
}

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void page_unlock_anon_vma(struct anon_vma *anon_vma)
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	__releases(&anon_vma->root->lock)
	__releases(RCU)
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{
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	anon_vma_unlock(anon_vma);
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	rcu_read_unlock();
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}

/*
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 * At what user virtual address is page expected in @vma?
 * Returns virtual address or -EFAULT if page's index/offset is not
 * within the range mapped the @vma.
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 */
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inline unsigned long
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vma_address(struct page *page, struct vm_area_struct *vma)
{
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	unsigned long address;

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	if (unlikely(is_vm_hugetlb_page(vma)))
		pgoff = page->index << huge_page_order(page_hstate(page));
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	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
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		/* page should be within @vma mapping range */
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		return -EFAULT;
	}
	return address;
}

/*
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 * At what user virtual address is page expected in vma?
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 * Caller should check the page is actually part of the vma.
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 */
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
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	if (PageAnon(page)) {
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		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)
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			return -EFAULT;
	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
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		if (!vma->vm_file ||
		    vma->vm_file->f_mapping != page->mapping)
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			return -EFAULT;
	} else
		return -EFAULT;
	return vma_address(page, vma);
}

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/*
 * Check that @page is mapped at @address into @mm.
 *
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 * 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).
 *
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 * On success returns with pte mapped and locked.
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 */
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pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
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			  unsigned long address, spinlock_t **ptlp, int sync)
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{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
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	spinlock_t *ptl;
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	if (unlikely(PageHuge(page))) {
		pte = huge_pte_offset(mm, address);
		ptl = &mm->page_table_lock;
		goto check;
	}

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	pgd = pgd_offset(mm, address);
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	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;
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	if (pmd_trans_huge(*pmd))
		return NULL;
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	pte = pte_offset_map(pmd, address);
	/* Make a quick check before getting the lock */
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	if (!sync && !pte_present(*pte)) {
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		pte_unmap(pte);
		return NULL;
	}

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	ptl = pte_lockptr(mm, pmd);
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check:
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	spin_lock(ptl);
	if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
		*ptlp = ptl;
		return pte;
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	}
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	pte_unmap_unlock(pte, ptl);
	return NULL;
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}

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

	address = vma_address(page, vma);
	if (address == -EFAULT)		/* out of vma range */
		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;
}

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/*
 * Subfunctions of page_referenced: page_referenced_one called
 * repeatedly from either page_referenced_anon or page_referenced_file.
 */
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int page_referenced_one(struct page *page, struct vm_area_struct *vma,
			unsigned long address, unsigned int *mapcount,
			unsigned long *vm_flags)
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{
	struct mm_struct *mm = vma->vm_mm;
	int referenced = 0;

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	/*
	 * Don't want to elevate referenced for mlocked page that gets this far,
	 * in order that it progresses to try_to_unmap and is moved to the
	 * unevictable list.
	 */
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	if (vma->vm_flags & VM_LOCKED) {
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		*mapcount = 0;	/* break early from loop */
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		*vm_flags |= VM_LOCKED;
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		goto out;
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	}
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	/* Pretend the page is referenced if the task has the
	   swap token and is in the middle of a page fault. */
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	if (mm != current->mm && has_swap_token(mm) &&
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			rwsem_is_locked(&mm->mmap_sem))
		referenced++;

517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548
	if (unlikely(PageTransHuge(page))) {
		pmd_t *pmd;

		spin_lock(&mm->page_table_lock);
		pmd = page_check_address_pmd(page, mm, address,
					     PAGE_CHECK_ADDRESS_PMD_FLAG);
		if (pmd && !pmd_trans_splitting(*pmd) &&
		    pmdp_clear_flush_young_notify(vma, address, pmd))
			referenced++;
		spin_unlock(&mm->page_table_lock);
	} else {
		pte_t *pte;
		spinlock_t *ptl;

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

		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
549
	(*mapcount)--;
550

551 552
	if (referenced)
		*vm_flags |= vma->vm_flags;
553
out:
L
Linus Torvalds 已提交
554 555 556
	return referenced;
}

557
static int page_referenced_anon(struct page *page,
558 559
				struct mem_cgroup *mem_cont,
				unsigned long *vm_flags)
L
Linus Torvalds 已提交
560 561 562
{
	unsigned int mapcount;
	struct anon_vma *anon_vma;
563
	struct anon_vma_chain *avc;
L
Linus Torvalds 已提交
564 565 566 567 568 569 570
	int referenced = 0;

	anon_vma = page_lock_anon_vma(page);
	if (!anon_vma)
		return referenced;

	mapcount = page_mapcount(page);
571 572
	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
		struct vm_area_struct *vma = avc->vma;
H
Hugh Dickins 已提交
573 574 575
		unsigned long address = vma_address(page, vma);
		if (address == -EFAULT)
			continue;
576 577 578 579 580
		/*
		 * If we are reclaiming on behalf of a cgroup, skip
		 * counting on behalf of references from different
		 * cgroups
		 */
581
		if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
582
			continue;
H
Hugh Dickins 已提交
583
		referenced += page_referenced_one(page, vma, address,
584
						  &mapcount, vm_flags);
L
Linus Torvalds 已提交
585 586 587
		if (!mapcount)
			break;
	}
588 589

	page_unlock_anon_vma(anon_vma);
L
Linus Torvalds 已提交
590 591 592 593 594 595
	return referenced;
}

/**
 * page_referenced_file - referenced check for object-based rmap
 * @page: the page we're checking references on.
R
Randy Dunlap 已提交
596
 * @mem_cont: target memory controller
597
 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
L
Linus Torvalds 已提交
598 599 600 601 602 603 604 605
 *
 * 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.
 */
606
static int page_referenced_file(struct page *page,
607 608
				struct mem_cgroup *mem_cont,
				unsigned long *vm_flags)
L
Linus Torvalds 已提交
609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640
{
	unsigned int mapcount;
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	struct prio_tree_iter iter;
	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,
	 * so we can safely take mapping->i_mmap_lock.
	 */
	BUG_ON(!PageLocked(page));

	spin_lock(&mapping->i_mmap_lock);

	/*
	 * i_mmap_lock does not stabilize mapcount at all, but mapcount
	 * is more likely to be accurate if we note it after spinning.
	 */
	mapcount = page_mapcount(page);

	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
641 642 643
		unsigned long address = vma_address(page, vma);
		if (address == -EFAULT)
			continue;
644 645 646 647 648
		/*
		 * If we are reclaiming on behalf of a cgroup, skip
		 * counting on behalf of references from different
		 * cgroups
		 */
649
		if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
650
			continue;
H
Hugh Dickins 已提交
651
		referenced += page_referenced_one(page, vma, address,
652
						  &mapcount, vm_flags);
L
Linus Torvalds 已提交
653 654 655 656 657 658 659 660 661 662 663 664
		if (!mapcount)
			break;
	}

	spin_unlock(&mapping->i_mmap_lock);
	return referenced;
}

/**
 * page_referenced - test if the page was referenced
 * @page: the page to test
 * @is_locked: caller holds lock on the page
R
Randy Dunlap 已提交
665
 * @mem_cont: target memory controller
666
 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
L
Linus Torvalds 已提交
667 668 669 670
 *
 * Quick test_and_clear_referenced for all mappings to a page,
 * returns the number of ptes which referenced the page.
 */
671 672 673 674
int page_referenced(struct page *page,
		    int is_locked,
		    struct mem_cgroup *mem_cont,
		    unsigned long *vm_flags)
L
Linus Torvalds 已提交
675 676
{
	int referenced = 0;
H
Hugh Dickins 已提交
677
	int we_locked = 0;
L
Linus Torvalds 已提交
678

679
	*vm_flags = 0;
H
Hugh Dickins 已提交
680
	if (page_mapped(page) && page_rmapping(page)) {
H
Hugh Dickins 已提交
681 682 683 684 685 686 687 688 689 690 691
		if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
			we_locked = trylock_page(page);
			if (!we_locked) {
				referenced++;
				goto out;
			}
		}
		if (unlikely(PageKsm(page)))
			referenced += page_referenced_ksm(page, mem_cont,
								vm_flags);
		else if (PageAnon(page))
692 693
			referenced += page_referenced_anon(page, mem_cont,
								vm_flags);
H
Hugh Dickins 已提交
694
		else if (page->mapping)
695 696
			referenced += page_referenced_file(page, mem_cont,
								vm_flags);
H
Hugh Dickins 已提交
697
		if (we_locked)
L
Linus Torvalds 已提交
698 699
			unlock_page(page);
	}
H
Hugh Dickins 已提交
700
out:
701 702 703
	if (page_test_and_clear_young(page))
		referenced++;

L
Linus Torvalds 已提交
704 705 706
	return referenced;
}

H
Hugh Dickins 已提交
707 708
static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
			    unsigned long address)
709 710
{
	struct mm_struct *mm = vma->vm_mm;
711
	pte_t *pte;
712 713 714
	spinlock_t *ptl;
	int ret = 0;

N
Nick Piggin 已提交
715
	pte = page_check_address(page, mm, address, &ptl, 1);
716 717 718
	if (!pte)
		goto out;

719 720
	if (pte_dirty(*pte) || pte_write(*pte)) {
		pte_t entry;
721

722
		flush_cache_page(vma, address, pte_pfn(*pte));
A
Andrea Arcangeli 已提交
723
		entry = ptep_clear_flush_notify(vma, address, pte);
724 725
		entry = pte_wrprotect(entry);
		entry = pte_mkclean(entry);
726
		set_pte_at(mm, address, pte, entry);
727 728
		ret = 1;
	}
729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745

	pte_unmap_unlock(pte, ptl);
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;
	struct prio_tree_iter iter;
	int ret = 0;

	BUG_ON(PageAnon(page));

	spin_lock(&mapping->i_mmap_lock);
	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
746 747 748 749 750 751
		if (vma->vm_flags & VM_SHARED) {
			unsigned long address = vma_address(page, vma);
			if (address == -EFAULT)
				continue;
			ret += page_mkclean_one(page, vma, address);
		}
752 753 754 755 756 757 758 759 760 761 762 763 764
	}
	spin_unlock(&mapping->i_mmap_lock);
	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);
765
		if (mapping) {
766
			ret = page_mkclean_file(mapping, page);
767
			if (page_test_dirty(page)) {
768
				page_clear_dirty(page, 1);
769 770
				ret = 1;
			}
771
		}
772 773 774 775
	}

	return ret;
}
J
Jaya Kumar 已提交
776
EXPORT_SYMBOL_GPL(page_mkclean);
777

778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801
/**
 * 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
802
/**
A
Andi Kleen 已提交
803 804 805 806
 * __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	
807
 * @exclusive:	the page is exclusively owned by the current process
N
Nick Piggin 已提交
808 809
 */
static void __page_set_anon_rmap(struct page *page,
810
	struct vm_area_struct *vma, unsigned long address, int exclusive)
N
Nick Piggin 已提交
811
{
812
	struct anon_vma *anon_vma = vma->anon_vma;
813

814
	BUG_ON(!anon_vma);
815

A
Andi Kleen 已提交
816 817 818
	if (PageAnon(page))
		return;

819
	/*
820 821 822
	 * If the page isn't exclusively mapped into this vma,
	 * we must use the _oldest_ possible anon_vma for the
	 * page mapping!
823
	 */
A
Andi Kleen 已提交
824
	if (!exclusive)
825
		anon_vma = anon_vma->root;
N
Nick Piggin 已提交
826 827 828 829 830 831

	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
832
/**
R
Randy Dunlap 已提交
833
 * __page_check_anon_rmap - sanity check anonymous rmap addition
N
Nick Piggin 已提交
834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853
 * @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
854
	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
N
Nick Piggin 已提交
855 856 857 858
	BUG_ON(page->index != linear_page_index(vma, address));
#endif
}

L
Linus Torvalds 已提交
859 860 861 862 863 864
/**
 * 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
865
 * The caller needs to hold the pte lock, and the page must be locked in
866 867 868
 * 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
869 870 871
 */
void page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
872 873 874 875 876 877 878 879 880 881 882
{
	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
883
{
H
Hugh Dickins 已提交
884 885 886 887 888 889
	int first = atomic_inc_and_test(&page->_mapcount);
	if (first)
		__inc_zone_page_state(page, NR_ANON_PAGES);
	if (unlikely(PageKsm(page)))
		return;

N
Nick Piggin 已提交
890 891
	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
H
Hugh Dickins 已提交
892
	if (first)
893
		__page_set_anon_rmap(page, vma, address, exclusive);
894
	else
N
Nick Piggin 已提交
895
		__page_check_anon_rmap(page, vma, address);
L
Linus Torvalds 已提交
896 897
}

R
Randy Dunlap 已提交
898
/**
N
Nick Piggin 已提交
899 900 901 902 903 904 905
 * 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
906
 * Page does not have to be locked.
N
Nick Piggin 已提交
907 908 909 910
 */
void page_add_new_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
911
	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
912 913
	SetPageSwapBacked(page);
	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
H
Hugh Dickins 已提交
914
	__inc_zone_page_state(page, NR_ANON_PAGES);
915
	__page_set_anon_rmap(page, vma, address, 1);
916
	if (page_evictable(page, vma))
917
		lru_cache_add_lru(page, LRU_ACTIVE_ANON);
918 919
	else
		add_page_to_unevictable_list(page);
N
Nick Piggin 已提交
920 921
}

L
Linus Torvalds 已提交
922 923 924 925
/**
 * page_add_file_rmap - add pte mapping to a file page
 * @page: the page to add the mapping to
 *
926
 * The caller needs to hold the pte lock.
L
Linus Torvalds 已提交
927 928 929
 */
void page_add_file_rmap(struct page *page)
{
930
	if (atomic_inc_and_test(&page->_mapcount)) {
931
		__inc_zone_page_state(page, NR_FILE_MAPPED);
932
		mem_cgroup_update_file_mapped(page, 1);
933
	}
L
Linus Torvalds 已提交
934 935 936 937 938 939
}

/**
 * page_remove_rmap - take down pte mapping from a page
 * @page: page to remove mapping from
 *
940
 * The caller needs to hold the pte lock.
L
Linus Torvalds 已提交
941
 */
942
void page_remove_rmap(struct page *page)
L
Linus Torvalds 已提交
943
{
944 945 946 947 948 949 950 951 952 953 954 955
	/* page still mapped by someone else? */
	if (!atomic_add_negative(-1, &page->_mapcount))
		return;

	/*
	 * 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.
	 */
	if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) {
956
		page_clear_dirty(page, 1);
957
		set_page_dirty(page);
L
Linus Torvalds 已提交
958
	}
959 960 961 962 963 964
	/*
	 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
	 * and not charged by memcg for now.
	 */
	if (unlikely(PageHuge(page)))
		return;
965 966 967 968 969
	if (PageAnon(page)) {
		mem_cgroup_uncharge_page(page);
		__dec_zone_page_state(page, NR_ANON_PAGES);
	} else {
		__dec_zone_page_state(page, NR_FILE_MAPPED);
970
		mem_cgroup_update_file_mapped(page, -1);
971 972 973 974 975 976 977 978 979 980
	}
	/*
	 * 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.
	 */
L
Linus Torvalds 已提交
981 982 983 984 985 986
}

/*
 * Subfunctions of try_to_unmap: try_to_unmap_one called
 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
 */
H
Hugh Dickins 已提交
987 988
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
989 990 991 992
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte;
	pte_t pteval;
H
Hugh Dickins 已提交
993
	spinlock_t *ptl;
L
Linus Torvalds 已提交
994 995
	int ret = SWAP_AGAIN;

N
Nick Piggin 已提交
996
	pte = page_check_address(page, mm, address, &ptl, 0);
H
Hugh Dickins 已提交
997
	if (!pte)
N
Nikita Danilov 已提交
998
		goto out;
L
Linus Torvalds 已提交
999 1000 1001 1002 1003 1004

	/*
	 * 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.
	 */
1005
	if (!(flags & TTU_IGNORE_MLOCK)) {
K
KOSAKI Motohiro 已提交
1006 1007 1008
		if (vma->vm_flags & VM_LOCKED)
			goto out_mlock;

H
Hugh Dickins 已提交
1009
		if (TTU_ACTION(flags) == TTU_MUNLOCK)
H
Hugh Dickins 已提交
1010
			goto out_unmap;
1011 1012
	}
	if (!(flags & TTU_IGNORE_ACCESS)) {
N
Nick Piggin 已提交
1013 1014 1015 1016 1017
		if (ptep_clear_flush_young_notify(vma, address, pte)) {
			ret = SWAP_FAIL;
			goto out_unmap;
		}
  	}
L
Linus Torvalds 已提交
1018 1019 1020

	/* Nuke the page table entry. */
	flush_cache_page(vma, address, page_to_pfn(page));
A
Andrea Arcangeli 已提交
1021
	pteval = ptep_clear_flush_notify(vma, address, pte);
L
Linus Torvalds 已提交
1022 1023 1024 1025 1026

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

1027 1028 1029
	/* Update high watermark before we lower rss */
	update_hiwater_rss(mm);

1030 1031
	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
		if (PageAnon(page))
K
KAMEZAWA Hiroyuki 已提交
1032
			dec_mm_counter(mm, MM_ANONPAGES);
1033
		else
K
KAMEZAWA Hiroyuki 已提交
1034
			dec_mm_counter(mm, MM_FILEPAGES);
1035 1036 1037
		set_pte_at(mm, address, pte,
				swp_entry_to_pte(make_hwpoison_entry(page)));
	} else if (PageAnon(page)) {
H
Hugh Dickins 已提交
1038
		swp_entry_t entry = { .val = page_private(page) };
1039 1040 1041 1042 1043 1044

		if (PageSwapCache(page)) {
			/*
			 * Store the swap location in the pte.
			 * See handle_pte_fault() ...
			 */
H
Hugh Dickins 已提交
1045 1046 1047 1048 1049
			if (swap_duplicate(entry) < 0) {
				set_pte_at(mm, address, pte, pteval);
				ret = SWAP_FAIL;
				goto out_unmap;
			}
1050 1051 1052 1053 1054 1055
			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
1056
			dec_mm_counter(mm, MM_ANONPAGES);
K
KAMEZAWA Hiroyuki 已提交
1057
			inc_mm_counter(mm, MM_SWAPENTS);
1058
		} else if (PAGE_MIGRATION) {
1059 1060 1061 1062 1063
			/*
			 * 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.
			 */
1064
			BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1065
			entry = make_migration_entry(page, pte_write(pteval));
L
Linus Torvalds 已提交
1066 1067 1068
		}
		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
		BUG_ON(pte_file(*pte));
1069
	} else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
1070 1071 1072 1073 1074
		/* 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
1075
		dec_mm_counter(mm, MM_FILEPAGES);
L
Linus Torvalds 已提交
1076

1077
	page_remove_rmap(page);
L
Linus Torvalds 已提交
1078 1079 1080
	page_cache_release(page);

out_unmap:
H
Hugh Dickins 已提交
1081
	pte_unmap_unlock(pte, ptl);
K
KOSAKI Motohiro 已提交
1082 1083
out:
	return ret;
H
Hugh Dickins 已提交
1084

K
KOSAKI Motohiro 已提交
1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100
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->lock or mapping->i_mmap_lock.
	 * 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
1101
		}
K
KOSAKI Motohiro 已提交
1102
		up_read(&vma->vm_mm->mmap_sem);
H
Hugh Dickins 已提交
1103
	}
L
Linus Torvalds 已提交
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124
	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
1125 1126 1127 1128 1129
 *
 * 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
1130 1131 1132 1133
 */
#define CLUSTER_SIZE	min(32*PAGE_SIZE, PMD_SIZE)
#define CLUSTER_MASK	(~(CLUSTER_SIZE - 1))

N
Nick Piggin 已提交
1134 1135
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
1136 1137 1138 1139 1140
{
	struct mm_struct *mm = vma->vm_mm;
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
H
Hugh Dickins 已提交
1141
	pte_t *pte;
L
Linus Torvalds 已提交
1142
	pte_t pteval;
H
Hugh Dickins 已提交
1143
	spinlock_t *ptl;
L
Linus Torvalds 已提交
1144 1145 1146
	struct page *page;
	unsigned long address;
	unsigned long end;
N
Nick Piggin 已提交
1147 1148
	int ret = SWAP_AGAIN;
	int locked_vma = 0;
L
Linus Torvalds 已提交
1149 1150 1151 1152 1153 1154 1155 1156 1157 1158

	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
1159
		return ret;
L
Linus Torvalds 已提交
1160 1161 1162

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
N
Nick Piggin 已提交
1163
		return ret;
L
Linus Torvalds 已提交
1164 1165 1166

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
N
Nick Piggin 已提交
1167 1168 1169
		return ret;

	/*
H
Hugh Dickins 已提交
1170
	 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
N
Nick Piggin 已提交
1171 1172
	 * keep the sem while scanning the cluster for mlocking pages.
	 */
H
Hugh Dickins 已提交
1173
	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
N
Nick Piggin 已提交
1174 1175 1176 1177
		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
1178 1179

	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
L
Linus Torvalds 已提交
1180

1181 1182 1183
	/* Update high watermark before we lower rss */
	update_hiwater_rss(mm);

H
Hugh Dickins 已提交
1184
	for (; address < end; pte++, address += PAGE_SIZE) {
L
Linus Torvalds 已提交
1185 1186
		if (!pte_present(*pte))
			continue;
1187 1188
		page = vm_normal_page(vma, address, *pte);
		BUG_ON(!page || PageAnon(page));
L
Linus Torvalds 已提交
1189

N
Nick Piggin 已提交
1190 1191 1192 1193 1194 1195 1196
		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
1197
		if (ptep_clear_flush_young_notify(vma, address, pte))
L
Linus Torvalds 已提交
1198 1199 1200
			continue;

		/* Nuke the page table entry. */
1201
		flush_cache_page(vma, address, pte_pfn(*pte));
A
Andrea Arcangeli 已提交
1202
		pteval = ptep_clear_flush_notify(vma, address, pte);
L
Linus Torvalds 已提交
1203 1204 1205 1206 1207 1208 1209 1210 1211

		/* 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);

1212
		page_remove_rmap(page);
L
Linus Torvalds 已提交
1213
		page_cache_release(page);
K
KAMEZAWA Hiroyuki 已提交
1214
		dec_mm_counter(mm, MM_FILEPAGES);
L
Linus Torvalds 已提交
1215 1216
		(*mapcount)--;
	}
H
Hugh Dickins 已提交
1217
	pte_unmap_unlock(pte - 1, ptl);
N
Nick Piggin 已提交
1218 1219 1220
	if (locked_vma)
		up_read(&vma->vm_mm->mmap_sem);
	return ret;
L
Linus Torvalds 已提交
1221 1222
}

1223
bool is_vma_temporary_stack(struct vm_area_struct *vma)
1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236
{
	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
1237 1238 1239 1240
/**
 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
 * rmap method
 * @page: the page to unmap/unlock
1241
 * @flags: action and flags
N
Nick Piggin 已提交
1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252
 *
 * 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.
 */
1253
static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1254 1255
{
	struct anon_vma *anon_vma;
1256
	struct anon_vma_chain *avc;
L
Linus Torvalds 已提交
1257
	int ret = SWAP_AGAIN;
N
Nick Piggin 已提交
1258

L
Linus Torvalds 已提交
1259 1260 1261 1262
	anon_vma = page_lock_anon_vma(page);
	if (!anon_vma)
		return ret;

1263 1264
	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
		struct vm_area_struct *vma = avc->vma;
1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279
		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.
		 */
		if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
				is_vma_temporary_stack(vma))
			continue;

		address = vma_address(page, vma);
H
Hugh Dickins 已提交
1280 1281 1282
		if (address == -EFAULT)
			continue;
		ret = try_to_unmap_one(page, vma, address, flags);
H
Hugh Dickins 已提交
1283 1284
		if (ret != SWAP_AGAIN || !page_mapped(page))
			break;
L
Linus Torvalds 已提交
1285
	}
1286 1287

	page_unlock_anon_vma(anon_vma);
L
Linus Torvalds 已提交
1288 1289 1290 1291
	return ret;
}

/**
N
Nick Piggin 已提交
1292 1293
 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
 * @page: the page to unmap/unlock
1294
 * @flags: action and flags
L
Linus Torvalds 已提交
1295 1296 1297 1298
 *
 * 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
1299 1300 1301 1302 1303 1304
 * 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
1305
 */
1306
static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319
{
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	struct prio_tree_iter iter;
	int ret = SWAP_AGAIN;
	unsigned long cursor;
	unsigned long max_nl_cursor = 0;
	unsigned long max_nl_size = 0;
	unsigned int mapcount;

	spin_lock(&mapping->i_mmap_lock);
	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
H
Hugh Dickins 已提交
1320 1321 1322 1323
		unsigned long address = vma_address(page, vma);
		if (address == -EFAULT)
			continue;
		ret = try_to_unmap_one(page, vma, address, flags);
H
Hugh Dickins 已提交
1324 1325
		if (ret != SWAP_AGAIN || !page_mapped(page))
			goto out;
L
Linus Torvalds 已提交
1326 1327 1328 1329 1330
	}

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

H
Hugh Dickins 已提交
1331 1332 1333 1334 1335 1336 1337 1338
	/*
	 * 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
1339 1340 1341 1342 1343 1344 1345 1346 1347 1348
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
						shared.vm_set.list) {
		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
1349
	if (max_nl_size == 0) {	/* all nonlinears locked or reserved ? */
L
Linus Torvalds 已提交
1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373
		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;
	cond_resched_lock(&mapping->i_mmap_lock);

	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.vm_set.list) {
			cursor = (unsigned long) vma->vm_private_data;
H
Hugh Dickins 已提交
1374
			while ( cursor < max_nl_cursor &&
L
Linus Torvalds 已提交
1375
				cursor < vma->vm_end - vma->vm_start) {
H
Hugh Dickins 已提交
1376 1377 1378
				if (try_to_unmap_cluster(cursor, &mapcount,
						vma, page) == SWAP_MLOCK)
					ret = SWAP_MLOCK;
L
Linus Torvalds 已提交
1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394
				cursor += CLUSTER_SIZE;
				vma->vm_private_data = (void *) cursor;
				if ((int)mapcount <= 0)
					goto out;
			}
			vma->vm_private_data = (void *) max_nl_cursor;
		}
		cond_resched_lock(&mapping->i_mmap_lock);
		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.
	 */
1395 1396
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
		vma->vm_private_data = NULL;
L
Linus Torvalds 已提交
1397 1398 1399 1400 1401 1402 1403 1404
out:
	spin_unlock(&mapping->i_mmap_lock);
	return ret;
}

/**
 * try_to_unmap - try to remove all page table mappings to a page
 * @page: the page to get unmapped
1405
 * @flags: action and flags
L
Linus Torvalds 已提交
1406 1407 1408 1409 1410 1411 1412 1413
 *
 * 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
1414
 * SWAP_MLOCK	- page is mlocked.
L
Linus Torvalds 已提交
1415
 */
1416
int try_to_unmap(struct page *page, enum ttu_flags flags)
L
Linus Torvalds 已提交
1417 1418 1419 1420
{
	int ret;

	BUG_ON(!PageLocked(page));
A
Andrea Arcangeli 已提交
1421
	BUG_ON(PageTransHuge(page));
L
Linus Torvalds 已提交
1422

H
Hugh Dickins 已提交
1423 1424 1425
	if (unlikely(PageKsm(page)))
		ret = try_to_unmap_ksm(page, flags);
	else if (PageAnon(page))
1426
		ret = try_to_unmap_anon(page, flags);
L
Linus Torvalds 已提交
1427
	else
1428
		ret = try_to_unmap_file(page, flags);
N
Nick Piggin 已提交
1429
	if (ret != SWAP_MLOCK && !page_mapped(page))
L
Linus Torvalds 已提交
1430 1431 1432
		ret = SWAP_SUCCESS;
	return ret;
}
N
Nikita Danilov 已提交
1433

N
Nick Piggin 已提交
1434 1435 1436 1437 1438 1439 1440 1441 1442 1443
/**
 * 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
1444
 * SWAP_AGAIN	- no vma is holding page mlocked, or,
N
Nick Piggin 已提交
1445
 * SWAP_AGAIN	- page mapped in mlocked vma -- couldn't acquire mmap sem
H
Hugh Dickins 已提交
1446
 * SWAP_FAIL	- page cannot be located at present
N
Nick Piggin 已提交
1447 1448 1449 1450 1451 1452
 * 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
1453 1454 1455
	if (unlikely(PageKsm(page)))
		return try_to_unmap_ksm(page, TTU_MUNLOCK);
	else if (PageAnon(page))
1456
		return try_to_unmap_anon(page, TTU_MUNLOCK);
N
Nick Piggin 已提交
1457
	else
1458
		return try_to_unmap_file(page, TTU_MUNLOCK);
N
Nick Piggin 已提交
1459
}
1460

1461 1462 1463 1464 1465 1466 1467 1468 1469
#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
/*
 * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
 * if necessary.  Be careful to do all the tests under the lock.  Once
 * we know we are the last user, nobody else can get a reference and we
 * can do the freeing without the lock.
 */
void drop_anon_vma(struct anon_vma *anon_vma)
{
A
Andrea Arcangeli 已提交
1470
	BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481
	if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
		struct anon_vma *root = anon_vma->root;
		int empty = list_empty(&anon_vma->head);
		int last_root_user = 0;
		int root_empty = 0;

		/*
		 * The refcount on a non-root anon_vma got dropped.  Drop
		 * the refcount on the root and check if we need to free it.
		 */
		if (empty && anon_vma != root) {
A
Andrea Arcangeli 已提交
1482
			BUG_ON(atomic_read(&root->external_refcount) <= 0);
1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496
			last_root_user = atomic_dec_and_test(&root->external_refcount);
			root_empty = list_empty(&root->head);
		}
		anon_vma_unlock(anon_vma);

		if (empty) {
			anon_vma_free(anon_vma);
			if (root_empty && last_root_user)
				anon_vma_free(root);
		}
	}
}
#endif

1497 1498 1499 1500 1501 1502 1503 1504 1505
#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;
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	struct anon_vma_chain *avc;
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	int ret = SWAP_AGAIN;

	/*
	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
	 * because that depends on page_mapped(); but not all its usages
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	 * are holding mmap_sem. Users without mmap_sem are required to
	 * take a reference count to prevent the anon_vma disappearing
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	 */
	anon_vma = page_anon_vma(page);
	if (!anon_vma)
		return ret;
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	anon_vma_lock(anon_vma);
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	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
		struct vm_area_struct *vma = avc->vma;
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		unsigned long address = vma_address(page, vma);
		if (address == -EFAULT)
			continue;
		ret = rmap_one(page, vma, address, arg);
		if (ret != SWAP_AGAIN)
			break;
	}
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	anon_vma_unlock(anon_vma);
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	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;
	struct prio_tree_iter iter;
	int ret = SWAP_AGAIN;

	if (!mapping)
		return ret;
	spin_lock(&mapping->i_mmap_lock);
	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
		unsigned long address = vma_address(page, vma);
		if (address == -EFAULT)
			continue;
		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.
	 */
	spin_unlock(&mapping->i_mmap_lock);
	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 */
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#ifdef CONFIG_HUGETLB_PAGE
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/*
 * 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;
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	BUG_ON(!anon_vma);
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	if (PageAnon(page))
		return;
	if (!exclusive)
		anon_vma = anon_vma->root;

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	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;
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	BUG_ON(!PageLocked(page));
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	BUG_ON(!anon_vma);
	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
	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);
}
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#endif /* CONFIG_HUGETLB_PAGE */