vmscan.c 59.3 KB
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/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/highmem.h>
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#include <linux/vmstat.h>
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#include <linux/file.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>	/* for try_to_release_page(),
					buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/notifier.h>
#include <linux/rwsem.h>
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#include <linux/delay.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/memcontrol.h>
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#include <linux/delayacct.h>
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#include <asm/tlbflush.h>
#include <asm/div64.h>

#include <linux/swapops.h>

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#include "internal.h"

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struct scan_control {
	/* Incremented by the number of inactive pages that were scanned */
	unsigned long nr_scanned;

	/* This context's GFP mask */
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	gfp_t gfp_mask;
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	int may_writepage;

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	/* Can pages be swapped as part of reclaim? */
	int may_swap;

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	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
	 * In this context, it doesn't matter that we scan the
	 * whole list at once. */
	int swap_cluster_max;
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	int swappiness;
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	int all_unreclaimable;
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	int order;
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	/* Which cgroup do we reclaim from */
	struct mem_cgroup *mem_cgroup;

	/* Pluggable isolate pages callback */
	unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
			unsigned long *scanned, int order, int mode,
			struct zone *z, struct mem_cgroup *mem_cont,
			int active);
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};

#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))

#ifdef ARCH_HAS_PREFETCH
#define prefetch_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetch(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

#ifdef ARCH_HAS_PREFETCHW
#define prefetchw_prev_lru_page(_page, _base, _field)			\
	do {								\
		if ((_page)->lru.prev != _base) {			\
			struct page *prev;				\
									\
			prev = lru_to_page(&(_page->lru));		\
			prefetchw(&prev->_field);			\
		}							\
	} while (0)
#else
#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
#endif

/*
 * From 0 .. 100.  Higher means more swappy.
 */
int vm_swappiness = 60;
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long vm_total_pages;	/* The total number of pages which the VM controls */
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static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);

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#ifdef CONFIG_CGROUP_MEM_RES_CTLR
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#define scan_global_lru(sc)	(!(sc)->mem_cgroup)
#else
#define scan_global_lru(sc)	(1)
#endif

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/*
 * Add a shrinker callback to be called from the vm
 */
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void register_shrinker(struct shrinker *shrinker)
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{
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	shrinker->nr = 0;
	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
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}
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EXPORT_SYMBOL(register_shrinker);
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/*
 * Remove one
 */
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void unregister_shrinker(struct shrinker *shrinker)
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{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
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EXPORT_SYMBOL(unregister_shrinker);
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#define SHRINK_BATCH 128
/*
 * Call the shrink functions to age shrinkable caches
 *
 * Here we assume it costs one seek to replace a lru page and that it also
 * takes a seek to recreate a cache object.  With this in mind we age equal
 * percentages of the lru and ageable caches.  This should balance the seeks
 * generated by these structures.
 *
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 * If the vm encountered mapped pages on the LRU it increase the pressure on
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 * slab to avoid swapping.
 *
 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
 *
 * `lru_pages' represents the number of on-LRU pages in all the zones which
 * are eligible for the caller's allocation attempt.  It is used for balancing
 * slab reclaim versus page reclaim.
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 *
 * Returns the number of slab objects which we shrunk.
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 */
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unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
			unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (scanned == 0)
		scanned = SWAP_CLUSTER_MAX;

	if (!down_read_trylock(&shrinker_rwsem))
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		return 1;	/* Assume we'll be able to shrink next time */
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
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		unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
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		delta = (4 * scanned) / shrinker->seeks;
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		delta *= max_pass;
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		do_div(delta, lru_pages + 1);
		shrinker->nr += delta;
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		if (shrinker->nr < 0) {
			printk(KERN_ERR "%s: nr=%ld\n",
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					__func__, shrinker->nr);
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			shrinker->nr = max_pass;
		}

		/*
		 * Avoid risking looping forever due to too large nr value:
		 * never try to free more than twice the estimate number of
		 * freeable entries.
		 */
		if (shrinker->nr > max_pass * 2)
			shrinker->nr = max_pass * 2;
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		total_scan = shrinker->nr;
		shrinker->nr = 0;

		while (total_scan >= SHRINK_BATCH) {
			long this_scan = SHRINK_BATCH;
			int shrink_ret;
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			int nr_before;
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			nr_before = (*shrinker->shrink)(0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
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			if (shrink_ret == -1)
				break;
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			if (shrink_ret < nr_before)
				ret += nr_before - shrink_ret;
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			count_vm_events(SLABS_SCANNED, this_scan);
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			total_scan -= this_scan;

			cond_resched();
		}

		shrinker->nr += total_scan;
	}
	up_read(&shrinker_rwsem);
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	return ret;
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}

/* Called without lock on whether page is mapped, so answer is unstable */
static inline int page_mapping_inuse(struct page *page)
{
	struct address_space *mapping;

	/* Page is in somebody's page tables. */
	if (page_mapped(page))
		return 1;

	/* Be more reluctant to reclaim swapcache than pagecache */
	if (PageSwapCache(page))
		return 1;

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

	/* File is mmap'd by somebody? */
	return mapping_mapped(mapping);
}

static inline int is_page_cache_freeable(struct page *page)
{
	return page_count(page) - !!PagePrivate(page) == 2;
}

static int may_write_to_queue(struct backing_dev_info *bdi)
{
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	if (current->flags & PF_SWAPWRITE)
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		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
	return 0;
}

/*
 * We detected a synchronous write error writing a page out.  Probably
 * -ENOSPC.  We need to propagate that into the address_space for a subsequent
 * fsync(), msync() or close().
 *
 * The tricky part is that after writepage we cannot touch the mapping: nothing
 * prevents it from being freed up.  But we have a ref on the page and once
 * that page is locked, the mapping is pinned.
 *
 * We're allowed to run sleeping lock_page() here because we know the caller has
 * __GFP_FS.
 */
static void handle_write_error(struct address_space *mapping,
				struct page *page, int error)
{
	lock_page(page);
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	if (page_mapping(page) == mapping)
		mapping_set_error(mapping, error);
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	unlock_page(page);
}

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/* Request for sync pageout. */
enum pageout_io {
	PAGEOUT_IO_ASYNC,
	PAGEOUT_IO_SYNC,
};

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/* possible outcome of pageout() */
typedef enum {
	/* failed to write page out, page is locked */
	PAGE_KEEP,
	/* move page to the active list, page is locked */
	PAGE_ACTIVATE,
	/* page has been sent to the disk successfully, page is unlocked */
	PAGE_SUCCESS,
	/* page is clean and locked */
	PAGE_CLEAN,
} pageout_t;

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/*
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 * pageout is called by shrink_page_list() for each dirty page.
 * Calls ->writepage().
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 */
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static pageout_t pageout(struct page *page, struct address_space *mapping,
						enum pageout_io sync_writeback)
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{
	/*
	 * If the page is dirty, only perform writeback if that write
	 * will be non-blocking.  To prevent this allocation from being
	 * stalled by pagecache activity.  But note that there may be
	 * stalls if we need to run get_block().  We could test
	 * PagePrivate for that.
	 *
	 * If this process is currently in generic_file_write() against
	 * this page's queue, we can perform writeback even if that
	 * will block.
	 *
	 * If the page is swapcache, write it back even if that would
	 * block, for some throttling. This happens by accident, because
	 * swap_backing_dev_info is bust: it doesn't reflect the
	 * congestion state of the swapdevs.  Easy to fix, if needed.
	 * See swapfile.c:page_queue_congested().
	 */
	if (!is_page_cache_freeable(page))
		return PAGE_KEEP;
	if (!mapping) {
		/*
		 * Some data journaling orphaned pages can have
		 * page->mapping == NULL while being dirty with clean buffers.
		 */
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		if (PagePrivate(page)) {
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			if (try_to_free_buffers(page)) {
				ClearPageDirty(page);
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				printk("%s: orphaned page\n", __func__);
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				return PAGE_CLEAN;
			}
		}
		return PAGE_KEEP;
	}
	if (mapping->a_ops->writepage == NULL)
		return PAGE_ACTIVATE;
	if (!may_write_to_queue(mapping->backing_dev_info))
		return PAGE_KEEP;

	if (clear_page_dirty_for_io(page)) {
		int res;
		struct writeback_control wbc = {
			.sync_mode = WB_SYNC_NONE,
			.nr_to_write = SWAP_CLUSTER_MAX,
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			.range_start = 0,
			.range_end = LLONG_MAX,
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			.nonblocking = 1,
			.for_reclaim = 1,
		};

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
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		if (res == AOP_WRITEPAGE_ACTIVATE) {
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			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
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		/*
		 * Wait on writeback if requested to. This happens when
		 * direct reclaiming a large contiguous area and the
		 * first attempt to free a range of pages fails.
		 */
		if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
			wait_on_page_writeback(page);

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		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
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		inc_zone_page_state(page, NR_VMSCAN_WRITE);
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		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

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/*
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 * Same as remove_mapping, but if the page is removed from the mapping, it
 * gets returned with a refcount of 0.
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 */
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static int __remove_mapping(struct address_space *mapping, struct page *page)
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{
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	BUG_ON(!PageLocked(page));
	BUG_ON(mapping != page_mapping(page));
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	spin_lock_irq(&mapping->tree_lock);
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	/*
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	 * The non racy check for a busy page.
	 *
	 * Must be careful with the order of the tests. When someone has
	 * a ref to the page, it may be possible that they dirty it then
	 * drop the reference. So if PageDirty is tested before page_count
	 * here, then the following race may occur:
	 *
	 * get_user_pages(&page);
	 * [user mapping goes away]
	 * write_to(page);
	 *				!PageDirty(page)    [good]
	 * SetPageDirty(page);
	 * put_page(page);
	 *				!page_count(page)   [good, discard it]
	 *
	 * [oops, our write_to data is lost]
	 *
	 * Reversing the order of the tests ensures such a situation cannot
	 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
	 * load is not satisfied before that of page->_count.
	 *
	 * Note that if SetPageDirty is always performed via set_page_dirty,
	 * and thus under tree_lock, then this ordering is not required.
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	 */
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	if (!page_freeze_refs(page, 2))
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		goto cannot_free;
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	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
	if (unlikely(PageDirty(page))) {
		page_unfreeze_refs(page, 2);
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		goto cannot_free;
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	}
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	if (PageSwapCache(page)) {
		swp_entry_t swap = { .val = page_private(page) };
		__delete_from_swap_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		swap_free(swap);
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	} else {
		__remove_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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	}

	return 1;

cannot_free:
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	spin_unlock_irq(&mapping->tree_lock);
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	return 0;
}

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/*
 * Attempt to detach a locked page from its ->mapping.  If it is dirty or if
 * someone else has a ref on the page, abort and return 0.  If it was
 * successfully detached, return 1.  Assumes the caller has a single ref on
 * this page.
 */
int remove_mapping(struct address_space *mapping, struct page *page)
{
	if (__remove_mapping(mapping, page)) {
		/*
		 * Unfreezing the refcount with 1 rather than 2 effectively
		 * drops the pagecache ref for us without requiring another
		 * atomic operation.
		 */
		page_unfreeze_refs(page, 1);
		return 1;
	}
	return 0;
}

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/*
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 * shrink_page_list() returns the number of reclaimed pages
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 */
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static unsigned long shrink_page_list(struct list_head *page_list,
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					struct scan_control *sc,
					enum pageout_io sync_writeback)
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{
	LIST_HEAD(ret_pages);
	struct pagevec freed_pvec;
	int pgactivate = 0;
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	unsigned long nr_reclaimed = 0;
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	cond_resched();

	pagevec_init(&freed_pvec, 1);
	while (!list_empty(page_list)) {
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;
		int referenced;

		cond_resched();

		page = lru_to_page(page_list);
		list_del(&page->lru);

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		if (!trylock_page(page))
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			goto keep;

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		VM_BUG_ON(PageActive(page));
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		sc->nr_scanned++;
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		if (!sc->may_swap && page_mapped(page))
			goto keep_locked;

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		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

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		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
			/*
			 * Synchronous reclaim is performed in two passes,
			 * first an asynchronous pass over the list to
			 * start parallel writeback, and a second synchronous
			 * pass to wait for the IO to complete.  Wait here
			 * for any page for which writeback has already
			 * started.
			 */
			if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
				wait_on_page_writeback(page);
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			else
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				goto keep_locked;
		}
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		referenced = page_referenced(page, 1, sc->mem_cgroup);
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		/* In active use or really unfreeable?  Activate it. */
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		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
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			goto activate_locked;

#ifdef CONFIG_SWAP
		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
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		if (PageAnon(page) && !PageSwapCache(page))
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			if (!add_to_swap(page, GFP_ATOMIC))
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				goto activate_locked;
#endif /* CONFIG_SWAP */

		mapping = page_mapping(page);

		/*
		 * The page is mapped into the page tables of one or more
		 * processes. Try to unmap it here.
		 */
		if (page_mapped(page) && mapping) {
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			switch (try_to_unmap(page, 0)) {
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			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
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			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
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				goto keep_locked;
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			if (!may_enter_fs)
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				goto keep_locked;
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			if (!sc->may_writepage)
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				goto keep_locked;

			/* Page is dirty, try to write it out here */
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			switch (pageout(page, mapping, sync_writeback)) {
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			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
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				if (PageWriteback(page) || PageDirty(page))
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					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
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				if (!trylock_page(page))
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					goto keep;
				if (PageDirty(page) || PageWriteback(page))
					goto keep_locked;
				mapping = page_mapping(page);
			case PAGE_CLEAN:
				; /* try to free the page below */
			}
		}

		/*
		 * If the page has buffers, try to free the buffer mappings
		 * associated with this page. If we succeed we try to free
		 * the page as well.
		 *
		 * We do this even if the page is PageDirty().
		 * try_to_release_page() does not perform I/O, but it is
		 * possible for a page to have PageDirty set, but it is actually
		 * clean (all its buffers are clean).  This happens if the
		 * buffers were written out directly, with submit_bh(). ext3
		 * will do this, as well as the blockdev mapping. 
		 * try_to_release_page() will discover that cleanness and will
		 * drop the buffers and mark the page clean - it can be freed.
		 *
		 * Rarely, pages can have buffers and no ->mapping.  These are
		 * the pages which were not successfully invalidated in
		 * truncate_complete_page().  We try to drop those buffers here
		 * and if that worked, and the page is no longer mapped into
		 * process address space (page_count == 1) it can be freed.
		 * Otherwise, leave the page on the LRU so it is swappable.
		 */
		if (PagePrivate(page)) {
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634
			if (!mapping && page_count(page) == 1) {
				unlock_page(page);
				if (put_page_testzero(page))
					goto free_it;
				else {
					/*
					 * rare race with speculative reference.
					 * the speculative reference will free
					 * this page shortly, so we may
					 * increment nr_reclaimed here (and
					 * leave it off the LRU).
					 */
					nr_reclaimed++;
					continue;
				}
			}
L
Linus Torvalds 已提交
635 636
		}

N
Nick Piggin 已提交
637
		if (!mapping || !__remove_mapping(mapping, page))
638
			goto keep_locked;
L
Linus Torvalds 已提交
639 640

		unlock_page(page);
N
Nick Piggin 已提交
641
free_it:
642
		nr_reclaimed++;
N
Nick Piggin 已提交
643 644 645 646
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
647 648 649 650 651 652 653 654 655
		continue;

activate_locked:
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
656
		VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
657 658 659
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
660
		__pagevec_free(&freed_pvec);
661
	count_vm_events(PGACTIVATE, pgactivate);
662
	return nr_reclaimed;
L
Linus Torvalds 已提交
663 664
}

A
Andy Whitcroft 已提交
665 666 667 668 669 670 671 672 673 674 675 676 677 678 679
/* LRU Isolation modes. */
#define ISOLATE_INACTIVE 0	/* Isolate inactive pages. */
#define ISOLATE_ACTIVE 1	/* Isolate active pages. */
#define ISOLATE_BOTH 2		/* Isolate both active and inactive pages. */

/*
 * Attempt to remove the specified page from its LRU.  Only take this page
 * if it is of the appropriate PageActive status.  Pages which are being
 * freed elsewhere are also ignored.
 *
 * page:	page to consider
 * mode:	one of the LRU isolation modes defined above
 *
 * returns 0 on success, -ve errno on failure.
 */
680
int __isolate_lru_page(struct page *page, int mode)
A
Andy Whitcroft 已提交
681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709
{
	int ret = -EINVAL;

	/* Only take pages on the LRU. */
	if (!PageLRU(page))
		return ret;

	/*
	 * When checking the active state, we need to be sure we are
	 * dealing with comparible boolean values.  Take the logical not
	 * of each.
	 */
	if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
		return ret;

	ret = -EBUSY;
	if (likely(get_page_unless_zero(page))) {
		/*
		 * Be careful not to clear PageLRU until after we're
		 * sure the page is not being freed elsewhere -- the
		 * page release code relies on it.
		 */
		ClearPageLRU(page);
		ret = 0;
	}

	return ret;
}

L
Linus Torvalds 已提交
710 711 712 713 714 715 716 717 718 719 720 721 722 723
/*
 * zone->lru_lock is heavily contended.  Some of the functions that
 * shrink the lists perform better by taking out a batch of pages
 * and working on them outside the LRU lock.
 *
 * For pagecache intensive workloads, this function is the hottest
 * spot in the kernel (apart from copy_*_user functions).
 *
 * Appropriate locks must be held before calling this function.
 *
 * @nr_to_scan:	The number of pages to look through on the list.
 * @src:	The LRU list to pull pages off.
 * @dst:	The temp list to put pages on to.
 * @scanned:	The number of pages that were scanned.
A
Andy Whitcroft 已提交
724 725
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
L
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726 727 728
 *
 * returns how many pages were moved onto *@dst.
 */
729 730
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
A
Andy Whitcroft 已提交
731
		unsigned long *scanned, int order, int mode)
L
Linus Torvalds 已提交
732
{
733
	unsigned long nr_taken = 0;
734
	unsigned long scan;
L
Linus Torvalds 已提交
735

736
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
737 738 739 740 741 742
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
743 744 745
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
746
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
747

A
Andy Whitcroft 已提交
748 749 750
		switch (__isolate_lru_page(page, mode)) {
		case 0:
			list_move(&page->lru, dst);
751
			nr_taken++;
A
Andy Whitcroft 已提交
752 753 754 755 756 757
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
758

A
Andy Whitcroft 已提交
759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807
		default:
			BUG();
		}

		if (!order)
			continue;

		/*
		 * Attempt to take all pages in the order aligned region
		 * surrounding the tag page.  Only take those pages of
		 * the same active state as that tag page.  We may safely
		 * round the target page pfn down to the requested order
		 * as the mem_map is guarenteed valid out to MAX_ORDER,
		 * where that page is in a different zone we will detect
		 * it from its zone id and abort this block scan.
		 */
		zone_id = page_zone_id(page);
		page_pfn = page_to_pfn(page);
		pfn = page_pfn & ~((1 << order) - 1);
		end_pfn = pfn + (1 << order);
		for (; pfn < end_pfn; pfn++) {
			struct page *cursor_page;

			/* The target page is in the block, ignore it. */
			if (unlikely(pfn == page_pfn))
				continue;

			/* Avoid holes within the zone. */
			if (unlikely(!pfn_valid_within(pfn)))
				break;

			cursor_page = pfn_to_page(pfn);
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
			switch (__isolate_lru_page(cursor_page, mode)) {
			case 0:
				list_move(&cursor_page->lru, dst);
				nr_taken++;
				scan++;
				break;

			case -EBUSY:
				/* else it is being freed elsewhere */
				list_move(&cursor_page->lru, src);
			default:
				break;
			}
		}
L
Linus Torvalds 已提交
808 809 810 811 812 813
	}

	*scanned = scan;
	return nr_taken;
}

814 815 816 817 818 819 820 821 822 823 824 825 826 827 828
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
					int active)
{
	if (active)
		return isolate_lru_pages(nr, &z->active_list, dst,
						scanned, order, mode);
	else
		return isolate_lru_pages(nr, &z->inactive_list, dst,
						scanned, order, mode);
}

A
Andy Whitcroft 已提交
829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
static unsigned long clear_active_flags(struct list_head *page_list)
{
	int nr_active = 0;
	struct page *page;

	list_for_each_entry(page, page_list, lru)
		if (PageActive(page)) {
			ClearPageActive(page);
			nr_active++;
		}

	return nr_active;
}

847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891
/**
 * isolate_lru_page - tries to isolate a page from its LRU list
 * @page: page to isolate from its LRU list
 *
 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
 * vmstat statistic corresponding to whatever LRU list the page was on.
 *
 * Returns 0 if the page was removed from an LRU list.
 * Returns -EBUSY if the page was not on an LRU list.
 *
 * The returned page will have PageLRU() cleared.  If it was found on
 * the active list, it will have PageActive set.  That flag may need
 * to be cleared by the caller before letting the page go.
 *
 * The vmstat statistic corresponding to the list on which the page was
 * found will be decremented.
 *
 * Restrictions:
 * (1) Must be called with an elevated refcount on the page. This is a
 *     fundamentnal difference from isolate_lru_pages (which is called
 *     without a stable reference).
 * (2) the lru_lock must not be held.
 * (3) interrupts must be enabled.
 */
int isolate_lru_page(struct page *page)
{
	int ret = -EBUSY;

	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
			ret = 0;
			ClearPageLRU(page);
			if (PageActive(page))
				del_page_from_active_list(zone, page);
			else
				del_page_from_inactive_list(zone, page);
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
892
/*
A
Andrew Morton 已提交
893 894
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
895
 */
A
Andrew Morton 已提交
896 897
static unsigned long shrink_inactive_list(unsigned long max_scan,
				struct zone *zone, struct scan_control *sc)
L
Linus Torvalds 已提交
898 899 900
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
901
	unsigned long nr_scanned = 0;
902
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
903 904 905 906 907

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
908
	do {
L
Linus Torvalds 已提交
909
		struct page *page;
910 911 912
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
913
		unsigned long nr_active;
L
Linus Torvalds 已提交
914

915
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
A
Andy Whitcroft 已提交
916 917
			     &page_list, &nr_scan, sc->order,
			     (sc->order > PAGE_ALLOC_COSTLY_ORDER)?
918 919
					     ISOLATE_BOTH : ISOLATE_INACTIVE,
				zone, sc->mem_cgroup, 0);
A
Andy Whitcroft 已提交
920
		nr_active = clear_active_flags(&page_list);
921
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
922 923 924 925

		__mod_zone_page_state(zone, NR_ACTIVE, -nr_active);
		__mod_zone_page_state(zone, NR_INACTIVE,
						-(nr_taken - nr_active));
926 927
		if (scan_global_lru(sc))
			zone->pages_scanned += nr_scan;
L
Linus Torvalds 已提交
928 929
		spin_unlock_irq(&zone->lru_lock);

930
		nr_scanned += nr_scan;
931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953
		nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);

		/*
		 * If we are direct reclaiming for contiguous pages and we do
		 * not reclaim everything in the list, try again and wait
		 * for IO to complete. This will stall high-order allocations
		 * but that should be acceptable to the caller
		 */
		if (nr_freed < nr_taken && !current_is_kswapd() &&
					sc->order > PAGE_ALLOC_COSTLY_ORDER) {
			congestion_wait(WRITE, HZ/10);

			/*
			 * The attempt at page out may have made some
			 * of the pages active, mark them inactive again.
			 */
			nr_active = clear_active_flags(&page_list);
			count_vm_events(PGDEACTIVATE, nr_active);

			nr_freed += shrink_page_list(&page_list, sc,
							PAGEOUT_IO_SYNC);
		}

954
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
955 956
		local_irq_disable();
		if (current_is_kswapd()) {
957 958
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
959
		} else if (scan_global_lru(sc))
960
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
961

S
Shantanu Goel 已提交
962
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
963

964 965 966
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
967
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
968 969 970 971 972
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
973
			VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
974
			SetPageLRU(page);
L
Linus Torvalds 已提交
975 976 977 978 979 980 981 982 983 984 985
			list_del(&page->lru);
			if (PageActive(page))
				add_page_to_active_list(zone, page);
			else
				add_page_to_inactive_list(zone, page);
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
986
  	} while (nr_scanned < max_scan);
987
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
988
done:
989
	local_irq_enable();
L
Linus Torvalds 已提交
990
	pagevec_release(&pvec);
991
	return nr_reclaimed;
L
Linus Torvalds 已提交
992 993
}

994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007
/*
 * We are about to scan this zone at a certain priority level.  If that priority
 * level is smaller (ie: more urgent) than the previous priority, then note
 * that priority level within the zone.  This is done so that when the next
 * process comes in to scan this zone, it will immediately start out at this
 * priority level rather than having to build up its own scanning priority.
 * Here, this priority affects only the reclaim-mapped threshold.
 */
static inline void note_zone_scanning_priority(struct zone *zone, int priority)
{
	if (priority < zone->prev_priority)
		zone->prev_priority = priority;
}

N
Nick Piggin 已提交
1008 1009
static inline int zone_is_near_oom(struct zone *zone)
{
1010 1011
	return zone->pages_scanned >= (zone_page_state(zone, NR_ACTIVE)
				+ zone_page_state(zone, NR_INACTIVE))*3;
N
Nick Piggin 已提交
1012 1013
}

1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120
/*
 * Determine we should try to reclaim mapped pages.
 * This is called only when sc->mem_cgroup is NULL.
 */
static int calc_reclaim_mapped(struct scan_control *sc, struct zone *zone,
				int priority)
{
	long mapped_ratio;
	long distress;
	long swap_tendency;
	long imbalance;
	int reclaim_mapped = 0;
	int prev_priority;

	if (scan_global_lru(sc) && zone_is_near_oom(zone))
		return 1;
	/*
	 * `distress' is a measure of how much trouble we're having
	 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
	 */
	if (scan_global_lru(sc))
		prev_priority = zone->prev_priority;
	else
		prev_priority = mem_cgroup_get_reclaim_priority(sc->mem_cgroup);

	distress = 100 >> min(prev_priority, priority);

	/*
	 * The point of this algorithm is to decide when to start
	 * reclaiming mapped memory instead of just pagecache.  Work out
	 * how much memory
	 * is mapped.
	 */
	if (scan_global_lru(sc))
		mapped_ratio = ((global_page_state(NR_FILE_MAPPED) +
				global_page_state(NR_ANON_PAGES)) * 100) /
					vm_total_pages;
	else
		mapped_ratio = mem_cgroup_calc_mapped_ratio(sc->mem_cgroup);

	/*
	 * Now decide how much we really want to unmap some pages.  The
	 * mapped ratio is downgraded - just because there's a lot of
	 * mapped memory doesn't necessarily mean that page reclaim
	 * isn't succeeding.
	 *
	 * The distress ratio is important - we don't want to start
	 * going oom.
	 *
	 * A 100% value of vm_swappiness overrides this algorithm
	 * altogether.
	 */
	swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;

	/*
	 * If there's huge imbalance between active and inactive
	 * (think active 100 times larger than inactive) we should
	 * become more permissive, or the system will take too much
	 * cpu before it start swapping during memory pressure.
	 * Distress is about avoiding early-oom, this is about
	 * making swappiness graceful despite setting it to low
	 * values.
	 *
	 * Avoid div by zero with nr_inactive+1, and max resulting
	 * value is vm_total_pages.
	 */
	if (scan_global_lru(sc)) {
		imbalance  = zone_page_state(zone, NR_ACTIVE);
		imbalance /= zone_page_state(zone, NR_INACTIVE) + 1;
	} else
		imbalance = mem_cgroup_reclaim_imbalance(sc->mem_cgroup);

	/*
	 * Reduce the effect of imbalance if swappiness is low,
	 * this means for a swappiness very low, the imbalance
	 * must be much higher than 100 for this logic to make
	 * the difference.
	 *
	 * Max temporary value is vm_total_pages*100.
	 */
	imbalance *= (vm_swappiness + 1);
	imbalance /= 100;

	/*
	 * If not much of the ram is mapped, makes the imbalance
	 * less relevant, it's high priority we refill the inactive
	 * list with mapped pages only in presence of high ratio of
	 * mapped pages.
	 *
	 * Max temporary value is vm_total_pages*100.
	 */
	imbalance *= mapped_ratio;
	imbalance /= 100;

	/* apply imbalance feedback to swap_tendency */
	swap_tendency += imbalance;

	/*
	 * Now use this metric to decide whether to start moving mapped
	 * memory onto the inactive list.
	 */
	if (swap_tendency >= 100)
		reclaim_mapped = 1;

	return reclaim_mapped;
}

L
Linus Torvalds 已提交
1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137
/*
 * This moves pages from the active list to the inactive list.
 *
 * We move them the other way if the page is referenced by one or more
 * processes, from rmap.
 *
 * If the pages are mostly unmapped, the processing is fast and it is
 * appropriate to hold zone->lru_lock across the whole operation.  But if
 * the pages are mapped, the processing is slow (page_referenced()) so we
 * should drop zone->lru_lock around each page.  It's impossible to balance
 * this, so instead we remove the pages from the LRU while processing them.
 * It is safe to rely on PG_active against the non-LRU pages in here because
 * nobody will play with that bit on a non-LRU page.
 *
 * The downside is that we have to touch page->_count against each page.
 * But we had to alter page->flags anyway.
 */
1138 1139


A
Andrew Morton 已提交
1140
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1141
				struct scan_control *sc, int priority)
L
Linus Torvalds 已提交
1142
{
1143
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1144
	int pgdeactivate = 0;
1145
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1146 1147 1148 1149 1150 1151
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
	LIST_HEAD(l_inactive);	/* Pages to go onto the inactive_list */
	LIST_HEAD(l_active);	/* Pages to go onto the active_list */
	struct page *page;
	struct pagevec pvec;
	int reclaim_mapped = 0;
1152

1153 1154
	if (sc->may_swap)
		reclaim_mapped = calc_reclaim_mapped(sc, zone, priority);
L
Linus Torvalds 已提交
1155 1156 1157

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1158 1159 1160
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
					sc->mem_cgroup, 1);
1161 1162 1163 1164 1165 1166 1167
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
	if (scan_global_lru(sc))
		zone->pages_scanned += pgscanned;

1168
	__mod_zone_page_state(zone, NR_ACTIVE, -pgmoved);
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1169 1170 1171 1172 1173 1174 1175 1176 1177
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
		if (page_mapped(page)) {
			if (!reclaim_mapped ||
			    (total_swap_pages == 0 && PageAnon(page)) ||
1178
			    page_referenced(page, 0, sc->mem_cgroup)) {
L
Linus Torvalds 已提交
1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
				list_add(&page->lru, &l_active);
				continue;
			}
		}
		list_add(&page->lru, &l_inactive);
	}

	pagevec_init(&pvec, 1);
	pgmoved = 0;
	spin_lock_irq(&zone->lru_lock);
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
N
Nick Piggin 已提交
1192
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1193
		SetPageLRU(page);
N
Nick Piggin 已提交
1194
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1195 1196
		ClearPageActive(page);

L
Linus Torvalds 已提交
1197
		list_move(&page->lru, &zone->inactive_list);
1198
		mem_cgroup_move_lists(page, false);
L
Linus Torvalds 已提交
1199 1200
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1201
			__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
L
Linus Torvalds 已提交
1202 1203 1204 1205 1206 1207 1208 1209 1210
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1211
	__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
L
Linus Torvalds 已提交
1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222
	pgdeactivate += pgmoved;
	if (buffer_heads_over_limit) {
		spin_unlock_irq(&zone->lru_lock);
		pagevec_strip(&pvec);
		spin_lock_irq(&zone->lru_lock);
	}

	pgmoved = 0;
	while (!list_empty(&l_active)) {
		page = lru_to_page(&l_active);
		prefetchw_prev_lru_page(page, &l_active, flags);
N
Nick Piggin 已提交
1223
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1224
		SetPageLRU(page);
N
Nick Piggin 已提交
1225
		VM_BUG_ON(!PageActive(page));
1226

L
Linus Torvalds 已提交
1227
		list_move(&page->lru, &zone->active_list);
1228
		mem_cgroup_move_lists(page, true);
L
Linus Torvalds 已提交
1229 1230
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1231
			__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
L
Linus Torvalds 已提交
1232 1233 1234 1235 1236 1237
			pgmoved = 0;
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1238
	__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
N
Nick Piggin 已提交
1239

1240 1241 1242
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1243

N
Nick Piggin 已提交
1244
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1245 1246 1247 1248 1249
}

/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1250 1251
static unsigned long shrink_zone(int priority, struct zone *zone,
				struct scan_control *sc)
L
Linus Torvalds 已提交
1252 1253 1254
{
	unsigned long nr_active;
	unsigned long nr_inactive;
1255
	unsigned long nr_to_scan;
1256
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
1257

1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
	if (scan_global_lru(sc)) {
		/*
		 * Add one to nr_to_scan just to make sure that the kernel
		 * will slowly sift through the active list.
		 */
		zone->nr_scan_active +=
			(zone_page_state(zone, NR_ACTIVE) >> priority) + 1;
		nr_active = zone->nr_scan_active;
		zone->nr_scan_inactive +=
			(zone_page_state(zone, NR_INACTIVE) >> priority) + 1;
		nr_inactive = zone->nr_scan_inactive;
		if (nr_inactive >= sc->swap_cluster_max)
			zone->nr_scan_inactive = 0;
		else
			nr_inactive = 0;

		if (nr_active >= sc->swap_cluster_max)
			zone->nr_scan_active = 0;
		else
			nr_active = 0;
	} else {
		/*
		 * This reclaim occurs not because zone memory shortage but
		 * because memory controller hits its limit.
		 * Then, don't modify zone reclaim related data.
		 */
		nr_active = mem_cgroup_calc_reclaim_active(sc->mem_cgroup,
					zone, priority);

		nr_inactive = mem_cgroup_calc_reclaim_inactive(sc->mem_cgroup,
					zone, priority);
	}
L
Linus Torvalds 已提交
1290 1291 1292 1293


	while (nr_active || nr_inactive) {
		if (nr_active) {
1294
			nr_to_scan = min(nr_active,
L
Linus Torvalds 已提交
1295
					(unsigned long)sc->swap_cluster_max);
1296
			nr_active -= nr_to_scan;
1297
			shrink_active_list(nr_to_scan, zone, sc, priority);
L
Linus Torvalds 已提交
1298 1299 1300
		}

		if (nr_inactive) {
1301
			nr_to_scan = min(nr_inactive,
L
Linus Torvalds 已提交
1302
					(unsigned long)sc->swap_cluster_max);
1303
			nr_inactive -= nr_to_scan;
A
Andrew Morton 已提交
1304 1305
			nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
								sc);
L
Linus Torvalds 已提交
1306 1307 1308
		}
	}

1309
	throttle_vm_writeout(sc->gfp_mask);
1310
	return nr_reclaimed;
L
Linus Torvalds 已提交
1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328
}

/*
 * This is the direct reclaim path, for page-allocating processes.  We only
 * try to reclaim pages from zones which will satisfy the caller's allocation
 * request.
 *
 * We reclaim from a zone even if that zone is over pages_high.  Because:
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
 * b) The zones may be over pages_high but they must go *over* pages_high to
 *    satisfy the `incremental min' zone defense algorithm.
 *
 * Returns the number of reclaimed pages.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1329
static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1330
					struct scan_control *sc)
L
Linus Torvalds 已提交
1331
{
1332
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1333
	unsigned long nr_reclaimed = 0;
1334
	struct zoneref *z;
1335
	struct zone *zone;
1336

1337
	sc->all_unreclaimable = 1;
1338
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1339
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1340
			continue;
1341 1342 1343 1344 1345 1346 1347 1348
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
		if (scan_global_lru(sc)) {
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1349

1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362
			if (zone_is_all_unreclaimable(zone) &&
						priority != DEF_PRIORITY)
				continue;	/* Let kswapd poll it */
			sc->all_unreclaimable = 0;
		} else {
			/*
			 * Ignore cpuset limitation here. We just want to reduce
			 * # of used pages by us regardless of memory shortage.
			 */
			sc->all_unreclaimable = 0;
			mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
							priority);
		}
1363

1364
		nr_reclaimed += shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1365
	}
1366

1367
	return nr_reclaimed;
L
Linus Torvalds 已提交
1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381
}
 
/*
 * This is the main entry point to direct page reclaim.
 *
 * If a full scan of the inactive list fails to free enough memory then we
 * are "out of memory" and something needs to be killed.
 *
 * If the caller is !__GFP_FS then the probability of a failure is reasonably
 * high - the zone may be full of dirty or under-writeback pages, which this
 * caller can't do much about.  We kick pdflush and take explicit naps in the
 * hope that some of these pages can be written.  But if the allocating task
 * holds filesystem locks which prevent writeout this might not work, and the
 * allocation attempt will fail.
1382 1383 1384
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1385
 */
1386
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1387
					struct scan_control *sc)
L
Linus Torvalds 已提交
1388 1389
{
	int priority;
1390
	unsigned long ret = 0;
1391
	unsigned long total_scanned = 0;
1392
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
1393 1394
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1395
	struct zoneref *z;
1396
	struct zone *zone;
1397
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1398

1399 1400
	delayacct_freepages_start();

1401 1402 1403 1404 1405 1406
	if (scan_global_lru(sc))
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
	if (scan_global_lru(sc)) {
1407
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1408

1409 1410
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1411

1412 1413 1414
			lru_pages += zone_page_state(zone, NR_ACTIVE)
					+ zone_page_state(zone, NR_INACTIVE);
		}
L
Linus Torvalds 已提交
1415 1416 1417
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1418
		sc->nr_scanned = 0;
1419 1420
		if (!priority)
			disable_swap_token();
1421
		nr_reclaimed += shrink_zones(priority, zonelist, sc);
1422 1423 1424 1425
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1426
		if (scan_global_lru(sc)) {
1427
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1428 1429 1430 1431
			if (reclaim_state) {
				nr_reclaimed += reclaim_state->reclaimed_slab;
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1432
		}
1433 1434
		total_scanned += sc->nr_scanned;
		if (nr_reclaimed >= sc->swap_cluster_max) {
1435
			ret = nr_reclaimed;
L
Linus Torvalds 已提交
1436 1437 1438 1439 1440 1441 1442 1443 1444 1445
			goto out;
		}

		/*
		 * Try to write back as many pages as we just scanned.  This
		 * tends to cause slow streaming writers to write data to the
		 * disk smoothly, at the dirtying rate, which is nice.   But
		 * that's undesirable in laptop mode, where we *want* lumpy
		 * writeout.  So in laptop mode, write out the whole world.
		 */
1446 1447
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1448
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1449
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1450 1451 1452
		}

		/* Take a nap, wait for some writeback to complete */
1453
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1454
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1455
	}
1456
	/* top priority shrink_zones still had more to do? don't OOM, then */
1457
	if (!sc->all_unreclaimable && scan_global_lru(sc))
1458
		ret = nr_reclaimed;
L
Linus Torvalds 已提交
1459
out:
1460 1461 1462 1463 1464 1465 1466 1467 1468
	/*
	 * Now that we've scanned all the zones at this priority level, note
	 * that level within the zone so that the next thread which performs
	 * scanning of this zone will immediately start out at this priority
	 * level.  This affects only the decision whether or not to bring
	 * mapped pages onto the inactive list.
	 */
	if (priority < 0)
		priority = 0;
L
Linus Torvalds 已提交
1469

1470
	if (scan_global_lru(sc)) {
1471
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1472 1473 1474 1475 1476 1477 1478 1479

			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;

			zone->prev_priority = priority;
		}
	} else
		mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
L
Linus Torvalds 已提交
1480

1481 1482
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1483 1484 1485
	return ret;
}

1486 1487
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
								gfp_t gfp_mask)
1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.may_swap = 1,
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
	};

1500
	return do_try_to_free_pages(zonelist, &sc);
1501 1502
}

1503
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1504

1505 1506
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
						gfp_t gfp_mask)
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
		.may_swap = 1,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
	};
1517
	struct zonelist *zonelist;
1518

1519 1520 1521 1522
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
	return do_try_to_free_pages(zonelist, &sc);
1523 1524 1525
}
#endif

L
Linus Torvalds 已提交
1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
 * they are all at pages_high.
 *
 * Returns the number of pages which were actually freed.
 *
 * There is special handling here for zones which are full of pinned pages.
 * This can happen if the pages are all mlocked, or if they are all used by
 * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
 * What we do is to detect the case where all pages in the zone have been
 * scanned twice and there has been zero successful reclaim.  Mark the zone as
 * dead and from now on, only perform a short scan.  Basically we're polling
 * the zone for when the problem goes away.
 *
 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
 * zones which have free_pages > pages_high, but once a zone is found to have
 * free_pages <= pages_high, we scan that zone and the lower zones regardless
 * of the number of free pages in the lower zones.  This interoperates with
 * the page allocator fallback scheme to ensure that aging of pages is balanced
 * across the zones.
 */
1547
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1548 1549 1550 1551
{
	int all_zones_ok;
	int priority;
	int i;
1552
	unsigned long total_scanned;
1553
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
1554
	struct reclaim_state *reclaim_state = current->reclaim_state;
1555 1556 1557
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 1,
1558 1559
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1560
		.order = order,
1561 1562
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1563
	};
1564 1565 1566 1567 1568
	/*
	 * temp_priority is used to remember the scanning priority at which
	 * this zone was successfully refilled to free_pages == pages_high.
	 */
	int temp_priority[MAX_NR_ZONES];
L
Linus Torvalds 已提交
1569 1570 1571

loop_again:
	total_scanned = 0;
1572
	nr_reclaimed = 0;
C
Christoph Lameter 已提交
1573
	sc.may_writepage = !laptop_mode;
1574
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1575

1576 1577
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1578 1579 1580 1581 1582

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
		unsigned long lru_pages = 0;

1583 1584 1585 1586
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1587 1588
		all_zones_ok = 1;

1589 1590 1591 1592 1593 1594
		/*
		 * Scan in the highmem->dma direction for the highest
		 * zone which needs scanning
		 */
		for (i = pgdat->nr_zones - 1; i >= 0; i--) {
			struct zone *zone = pgdat->node_zones + i;
L
Linus Torvalds 已提交
1595

1596 1597
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1598

1599 1600
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1601
				continue;
L
Linus Torvalds 已提交
1602

1603 1604 1605
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1606
				break;
L
Linus Torvalds 已提交
1607 1608
			}
		}
A
Andrew Morton 已提交
1609 1610 1611
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1612 1613 1614
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1615 1616
			lru_pages += zone_page_state(zone, NR_ACTIVE)
					+ zone_page_state(zone, NR_INACTIVE);
L
Linus Torvalds 已提交
1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629
		}

		/*
		 * Now scan the zone in the dma->highmem direction, stopping
		 * at the last zone which needs scanning.
		 *
		 * We do this because the page allocator works in the opposite
		 * direction.  This prevents the page allocator from allocating
		 * pages behind kswapd's direction of progress, which would
		 * cause too much scanning of the lower zones.
		 */
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;
1630
			int nr_slab;
L
Linus Torvalds 已提交
1631

1632
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1633 1634
				continue;

1635 1636
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1637 1638
				continue;

1639 1640 1641
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1642
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1643
			sc.nr_scanned = 0;
1644
			note_zone_scanning_priority(zone, priority);
1645 1646 1647 1648 1649 1650 1651
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
			if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
						end_zone, 0))
				nr_reclaimed += shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1652
			reclaim_state->reclaimed_slab = 0;
1653 1654
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1655
			nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1656
			total_scanned += sc.nr_scanned;
1657
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1658
				continue;
1659
			if (nr_slab == 0 && zone->pages_scanned >=
1660 1661
				(zone_page_state(zone, NR_ACTIVE)
				+ zone_page_state(zone, NR_INACTIVE)) * 6)
1662 1663
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
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1664 1665 1666 1667 1668 1669
			/*
			 * If we've done a decent amount of scanning and
			 * the reclaim ratio is low, start doing writepage
			 * even in laptop mode
			 */
			if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1670
			    total_scanned > nr_reclaimed + nr_reclaimed / 2)
L
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1671 1672 1673 1674 1675 1676 1677 1678
				sc.may_writepage = 1;
		}
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
1679
		if (total_scanned && priority < DEF_PRIORITY - 2)
1680
			congestion_wait(WRITE, HZ/10);
L
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1681 1682 1683 1684 1685 1686 1687

		/*
		 * We do this so kswapd doesn't build up large priorities for
		 * example when it is freeing in parallel with allocators. It
		 * matches the direct reclaim path behaviour in terms of impact
		 * on zone->*_priority.
		 */
1688
		if (nr_reclaimed >= SWAP_CLUSTER_MAX)
L
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1689 1690 1691
			break;
	}
out:
1692 1693 1694 1695 1696
	/*
	 * Note within each zone the priority level at which this zone was
	 * brought into a happy state.  So that the next thread which scans this
	 * zone will start out at that priority level.
	 */
L
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1697 1698 1699
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1700
		zone->prev_priority = temp_priority[i];
L
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1701 1702 1703
	}
	if (!all_zones_ok) {
		cond_resched();
1704 1705 1706

		try_to_freeze();

L
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1707 1708 1709
		goto loop_again;
	}

1710
	return nr_reclaimed;
L
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1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734
}

/*
 * The background pageout daemon, started as a kernel thread
 * from the init process. 
 *
 * This basically trickles out pages so that we have _some_
 * free memory available even if there is no other activity
 * that frees anything up. This is needed for things like routing
 * etc, where we otherwise might have all activity going on in
 * asynchronous contexts that cannot page things out.
 *
 * If there are applications that are active memory-allocators
 * (most normal use), this basically shouldn't matter.
 */
static int kswapd(void *p)
{
	unsigned long order;
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
1735
	node_to_cpumask_ptr(cpumask, pgdat->node_id);
L
Linus Torvalds 已提交
1736

1737 1738
	if (!cpus_empty(*cpumask))
		set_cpus_allowed_ptr(tsk, cpumask);
L
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1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752
	current->reclaim_state = &reclaim_state;

	/*
	 * Tell the memory management that we're a "memory allocator",
	 * and that if we need more memory we should get access to it
	 * regardless (see "__alloc_pages()"). "kswapd" should
	 * never get caught in the normal page freeing logic.
	 *
	 * (Kswapd normally doesn't need memory anyway, but sometimes
	 * you need a small amount of memory in order to be able to
	 * page out something else, and this flag essentially protects
	 * us from recursively trying to free more memory as we're
	 * trying to free the first piece of memory in the first place).
	 */
1753
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1754
	set_freezable();
L
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1755 1756 1757 1758

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1759

L
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1760 1761 1762 1763 1764 1765 1766 1767 1768 1769
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
		new_order = pgdat->kswapd_max_order;
		pgdat->kswapd_max_order = 0;
		if (order < new_order) {
			/*
			 * Don't sleep if someone wants a larger 'order'
			 * allocation
			 */
			order = new_order;
		} else {
1770 1771 1772
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
1773 1774 1775 1776
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

1777 1778 1779 1780 1781 1782
		if (!try_to_freeze()) {
			/* We can speed up thawing tasks if we don't call
			 * balance_pgdat after returning from the refrigerator
			 */
			balance_pgdat(pgdat, order);
		}
L
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1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
void wakeup_kswapd(struct zone *zone, int order)
{
	pg_data_t *pgdat;

1794
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
1795 1796 1797
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
1798
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
1799 1800 1801
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
1802
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
1803
		return;
1804
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
1805
		return;
1806
	wake_up_interruptible(&pgdat->kswapd_wait);
L
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1807 1808 1809 1810
}

#ifdef CONFIG_PM
/*
1811 1812 1813 1814 1815 1816
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
 * from LRU lists system-wide, for given pass and priority, and returns the
 * number of reclaimed pages
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
1817 1818
static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
				      int pass, struct scan_control *sc)
1819 1820 1821 1822 1823 1824 1825 1826 1827
{
	struct zone *zone;
	unsigned long nr_to_scan, ret = 0;

	for_each_zone(zone) {

		if (!populated_zone(zone))
			continue;

1828
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
1829 1830 1831 1832
			continue;

		/* For pass = 0 we don't shrink the active list */
		if (pass > 0) {
1833 1834
			zone->nr_scan_active +=
				(zone_page_state(zone, NR_ACTIVE) >> prio) + 1;
1835 1836
			if (zone->nr_scan_active >= nr_pages || pass > 3) {
				zone->nr_scan_active = 0;
1837 1838
				nr_to_scan = min(nr_pages,
					zone_page_state(zone, NR_ACTIVE));
1839
				shrink_active_list(nr_to_scan, zone, sc, prio);
1840 1841 1842
			}
		}

1843 1844
		zone->nr_scan_inactive +=
			(zone_page_state(zone, NR_INACTIVE) >> prio) + 1;
1845 1846
		if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
			zone->nr_scan_inactive = 0;
1847 1848
			nr_to_scan = min(nr_pages,
				zone_page_state(zone, NR_INACTIVE));
1849 1850 1851 1852 1853 1854 1855 1856 1857
			ret += shrink_inactive_list(nr_to_scan, zone, sc);
			if (ret >= nr_pages)
				return ret;
		}
	}

	return ret;
}

1858 1859
static unsigned long count_lru_pages(void)
{
1860
	return global_page_state(NR_ACTIVE) + global_page_state(NR_INACTIVE);
1861 1862
}

1863 1864 1865 1866 1867 1868 1869
/*
 * Try to free `nr_pages' of memory, system-wide, and return the number of
 * freed pages.
 *
 * Rather than trying to age LRUs the aim is to preserve the overall
 * LRU order by reclaiming preferentially
 * inactive > active > active referenced > active mapped
L
Linus Torvalds 已提交
1870
 */
1871
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
1872
{
1873
	unsigned long lru_pages, nr_slab;
1874
	unsigned long ret = 0;
1875 1876 1877 1878 1879 1880 1881 1882
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.may_swap = 0,
		.swap_cluster_max = nr_pages,
		.may_writepage = 1,
		.swappiness = vm_swappiness,
1883
		.isolate_pages = isolate_pages_global,
L
Linus Torvalds 已提交
1884 1885 1886
	};

	current->reclaim_state = &reclaim_state;
1887

1888
	lru_pages = count_lru_pages();
1889
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
1890 1891 1892 1893 1894
	/* If slab caches are huge, it's better to hit them first */
	while (nr_slab >= lru_pages) {
		reclaim_state.reclaimed_slab = 0;
		shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
		if (!reclaim_state.reclaimed_slab)
L
Linus Torvalds 已提交
1895
			break;
1896 1897 1898 1899 1900 1901

		ret += reclaim_state.reclaimed_slab;
		if (ret >= nr_pages)
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
1902
	}
1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929

	/*
	 * We try to shrink LRUs in 5 passes:
	 * 0 = Reclaim from inactive_list only
	 * 1 = Reclaim from active list but don't reclaim mapped
	 * 2 = 2nd pass of type 1
	 * 3 = Reclaim mapped (normal reclaim)
	 * 4 = 2nd pass of type 3
	 */
	for (pass = 0; pass < 5; pass++) {
		int prio;

		/* Force reclaiming mapped pages in the passes #3 and #4 */
		if (pass > 2) {
			sc.may_swap = 1;
			sc.swappiness = 100;
		}

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
			unsigned long nr_to_scan = nr_pages - ret;

			sc.nr_scanned = 0;
			ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (ret >= nr_pages)
				goto out;

			reclaim_state.reclaimed_slab = 0;
1930 1931
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
					count_lru_pages());
1932 1933 1934 1935 1936
			ret += reclaim_state.reclaimed_slab;
			if (ret >= nr_pages)
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
1937
				congestion_wait(WRITE, HZ / 10);
1938
		}
1939
	}
1940 1941 1942 1943 1944

	/*
	 * If ret = 0, we could not shrink LRUs, but there may be something
	 * in slab caches
	 */
1945
	if (!ret) {
1946 1947
		do {
			reclaim_state.reclaimed_slab = 0;
1948
			shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages());
1949 1950
			ret += reclaim_state.reclaimed_slab;
		} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
1951
	}
1952 1953

out:
L
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1954
	current->reclaim_state = NULL;
1955

L
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1956 1957 1958 1959 1960 1961 1962 1963
	return ret;
}
#endif

/* It's optimal to keep kswapds on the same CPUs as their memory, but
   not required for correctness.  So if the last cpu in a node goes
   away, we get changed to run anywhere: as the first one comes back,
   restore their cpu bindings. */
1964
static int __devinit cpu_callback(struct notifier_block *nfb,
1965
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
1966
{
1967
	int nid;
L
Linus Torvalds 已提交
1968

1969
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
1970
		for_each_node_state(nid, N_HIGH_MEMORY) {
1971 1972 1973 1974
			pg_data_t *pgdat = NODE_DATA(nid);
			node_to_cpumask_ptr(mask, pgdat->node_id);

			if (any_online_cpu(*mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
1975
				/* One of our CPUs online: restore mask */
1976
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
1977 1978 1979 1980 1981
		}
	}
	return NOTIFY_OK;
}

1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
/*
 * This kswapd start function will be called by init and node-hot-add.
 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
 */
int kswapd_run(int nid)
{
	pg_data_t *pgdat = NODE_DATA(nid);
	int ret = 0;

	if (pgdat->kswapd)
		return 0;

	pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
	if (IS_ERR(pgdat->kswapd)) {
		/* failure at boot is fatal */
		BUG_ON(system_state == SYSTEM_BOOTING);
		printk("Failed to start kswapd on node %d\n",nid);
		ret = -1;
	}
	return ret;
}

L
Linus Torvalds 已提交
2004 2005
static int __init kswapd_init(void)
{
2006
	int nid;
2007

L
Linus Torvalds 已提交
2008
	swap_setup();
2009
	for_each_node_state(nid, N_HIGH_MEMORY)
2010
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2011 2012 2013 2014 2015
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

#ifdef CONFIG_NUMA
/*
 * Zone reclaim mode
 *
 * If non-zero call zone_reclaim when the number of free pages falls below
 * the watermarks.
 */
int zone_reclaim_mode __read_mostly;

2026
#define RECLAIM_OFF 0
2027
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2028 2029 2030
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2031 2032 2033 2034 2035 2036 2037
/*
 * Priority for ZONE_RECLAIM. This determines the fraction of pages
 * of a node considered for each zone_reclaim. 4 scans 1/16th of
 * a zone.
 */
#define ZONE_RECLAIM_PRIORITY 4

2038 2039 2040 2041 2042 2043
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2044 2045 2046 2047 2048 2049
/*
 * If the number of slab pages in a zone grows beyond this percentage then
 * slab reclaim needs to occur.
 */
int sysctl_min_slab_ratio = 5;

2050 2051 2052
/*
 * Try to free up some pages from this zone through reclaim.
 */
2053
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2054
{
2055
	/* Minimum pages needed in order to stay on node */
2056
	const unsigned long nr_pages = 1 << order;
2057 2058
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2059
	int priority;
2060
	unsigned long nr_reclaimed = 0;
2061 2062 2063
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
		.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2064 2065
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2066
		.gfp_mask = gfp_mask,
2067
		.swappiness = vm_swappiness,
2068
		.isolate_pages = isolate_pages_global,
2069
	};
2070
	unsigned long slab_reclaimable;
2071 2072 2073

	disable_swap_token();
	cond_resched();
2074 2075 2076 2077 2078 2079
	/*
	 * We need to be able to allocate from the reserves for RECLAIM_SWAP
	 * and we also need to be able to write out pages for RECLAIM_WRITE
	 * and RECLAIM_SWAP.
	 */
	p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2080 2081
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2082

2083 2084 2085 2086 2087 2088 2089 2090 2091
	if (zone_page_state(zone, NR_FILE_PAGES) -
		zone_page_state(zone, NR_FILE_MAPPED) >
		zone->min_unmapped_pages) {
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2092
			note_zone_scanning_priority(zone, priority);
2093 2094 2095 2096
			nr_reclaimed += shrink_zone(priority, zone, &sc);
			priority--;
		} while (priority >= 0 && nr_reclaimed < nr_pages);
	}
2097

2098 2099
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2100
		/*
2101
		 * shrink_slab() does not currently allow us to determine how
2102 2103 2104 2105
		 * many pages were freed in this zone. So we take the current
		 * number of slab pages and shake the slab until it is reduced
		 * by the same nr_pages that we used for reclaiming unmapped
		 * pages.
2106
		 *
2107 2108
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2109
		 */
2110
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2111 2112
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2113
			;
2114 2115 2116 2117 2118 2119 2120

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
		nr_reclaimed += slab_reclaimable -
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2121 2122
	}

2123
	p->reclaim_state = NULL;
2124
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2125
	return nr_reclaimed >= nr_pages;
2126
}
2127 2128 2129 2130

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2131
	int ret;
2132 2133

	/*
2134 2135
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2136
	 *
2137 2138 2139 2140 2141
	 * A small portion of unmapped file backed pages is needed for
	 * file I/O otherwise pages read by file I/O will be immediately
	 * thrown out if the zone is overallocated. So we do not reclaim
	 * if less than a specified percentage of the zone is used by
	 * unmapped file backed pages.
2142
	 */
2143
	if (zone_page_state(zone, NR_FILE_PAGES) -
2144 2145 2146
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2147
		return 0;
2148

2149 2150 2151
	if (zone_is_all_unreclaimable(zone))
		return 0;

2152
	/*
2153
	 * Do not scan if the allocation should not be delayed.
2154
	 */
2155
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2156 2157 2158 2159 2160 2161 2162 2163
			return 0;

	/*
	 * Only run zone reclaim on the local zone or on zones that do not
	 * have associated processors. This will favor the local processor
	 * over remote processors and spread off node memory allocations
	 * as wide as possible.
	 */
2164
	node_id = zone_to_nid(zone);
2165
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2166
		return 0;
2167 2168 2169 2170 2171 2172 2173

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
		return 0;
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

	return ret;
2174
}
2175
#endif