vmscan.c 84.0 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>
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#include <linux/gfp.h>
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#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 <linux/sysctl.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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#define CREATE_TRACE_POINTS
#include <trace/events/vmscan.h>

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enum lumpy_mode {
	LUMPY_MODE_NONE,
	LUMPY_MODE_ASYNC,
	LUMPY_MODE_SYNC,
};

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

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	/* Number of pages freed so far during a call to shrink_zones() */
	unsigned long nr_reclaimed;

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	/* How many pages shrink_list() should reclaim */
	unsigned long nr_to_reclaim;

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	unsigned long hibernation_mode;

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

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	int swappiness;
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	int order;
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	/*
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	 * Intend to reclaim enough continuous memory rather than reclaim
	 * enough amount of memory. i.e, mode for high order allocation.
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	 */
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	enum lumpy_mode lumpy_reclaim_mode;
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	/* Which cgroup do we reclaim from */
	struct mem_cgroup *mem_cgroup;

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	/*
	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
	 * are scanned.
	 */
	nodemask_t	*nodemask;
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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 scanning_global_lru(sc)	(!(sc)->mem_cgroup)
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#else
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#define scanning_global_lru(sc)	(1)
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#endif

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static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
						  struct scan_control *sc)
{
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	if (!scanning_global_lru(sc))
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		return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);

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	return &zone->reclaim_stat;
}

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static unsigned long zone_nr_lru_pages(struct zone *zone,
				struct scan_control *sc, enum lru_list lru)
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{
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	if (!scanning_global_lru(sc))
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		return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);

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	return zone_page_state(zone, NR_LRU_BASE + lru);
}


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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;
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		max_pass = (*shrinker->shrink)(shrinker, 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) {
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			printk(KERN_ERR "shrink_slab: %pF negative objects to "
			       "delete nr=%ld\n",
			       shrinker->shrink, 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)(shrinker, 0, gfp_mask);
			shrink_ret = (*shrinker->shrink)(shrinker, 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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}

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static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
				   bool sync)
{
	enum lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;

	/*
	 * Some reclaim have alredy been failed. No worth to try synchronous
	 * lumpy reclaim.
	 */
	if (sync && sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
		return;

	/*
	 * If we need a large contiguous chunk of memory, or have
	 * trouble getting a small set of contiguous pages, we
	 * will reclaim both active and inactive pages.
	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		sc->lumpy_reclaim_mode = mode;
	else if (sc->order && priority < DEF_PRIORITY - 2)
		sc->lumpy_reclaim_mode = mode;
	else
		sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
}

static void disable_lumpy_reclaim_mode(struct scan_control *sc)
{
	sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
}

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static inline int is_page_cache_freeable(struct page *page)
{
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	/*
	 * A freeable page cache page is referenced only by the caller
	 * that isolated the page, the page cache radix tree and
	 * optional buffer heads at page->private.
	 */
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	return page_count(page) - page_has_private(page) == 2;
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}

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static int may_write_to_queue(struct backing_dev_info *bdi,
			      struct scan_control *sc)
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{
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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;
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	/* lumpy reclaim for hugepage often need a lot of write */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		return 1;
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	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)
{
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	lock_page_nosync(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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/* 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,
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			 struct scan_control *sc)
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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.
	 *
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	 * If this process is currently in __generic_file_aio_write() against
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	 * 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.
	 */
	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 (page_has_private(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;
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	if (!may_write_to_queue(mapping->backing_dev_info, sc))
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		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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			.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.
		 */
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		if (PageWriteback(page) &&
		    sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC)
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			wait_on_page_writeback(page);

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		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
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		trace_mm_vmscan_writepage(page,
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			trace_reclaim_flags(page, sc->lumpy_reclaim_mode));
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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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		swapcache_free(swap, page);
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	} else {
		__remove_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		mem_cgroup_uncharge_cache_page(page);
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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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/**
 * putback_lru_page - put previously isolated page onto appropriate LRU list
 * @page: page to be put back to appropriate lru list
 *
 * Add previously isolated @page to appropriate LRU list.
 * Page may still be unevictable for other reasons.
 *
 * lru_lock must not be held, interrupts must be enabled.
 */
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
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	int was_unevictable = PageUnevictable(page);
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	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

	if (page_evictable(page, NULL)) {
		/*
		 * For evictable pages, we can use the cache.
		 * In event of a race, worst case is we end up with an
		 * unevictable page on [in]active list.
		 * We know how to handle that.
		 */
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		lru = active + page_lru_base_type(page);
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		lru_cache_add_lru(page, lru);
	} else {
		/*
		 * Put unevictable pages directly on zone's unevictable
		 * list.
		 */
		lru = LRU_UNEVICTABLE;
		add_page_to_unevictable_list(page);
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		/*
		 * When racing with an mlock clearing (page is
		 * unlocked), make sure that if the other thread does
		 * not observe our setting of PG_lru and fails
		 * isolation, we see PG_mlocked cleared below and move
		 * the page back to the evictable list.
		 *
		 * The other side is TestClearPageMlocked().
		 */
		smp_mb();
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	}

	/*
	 * page's status can change while we move it among lru. If an evictable
	 * page is on unevictable list, it never be freed. To avoid that,
	 * check after we added it to the list, again.
	 */
	if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
		if (!isolate_lru_page(page)) {
			put_page(page);
			goto redo;
		}
		/* This means someone else dropped this page from LRU
		 * So, it will be freed or putback to LRU again. There is
		 * nothing to do here.
		 */
	}

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	if (was_unevictable && lru != LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGRESCUED);
	else if (!was_unevictable && lru == LRU_UNEVICTABLE)
		count_vm_event(UNEVICTABLE_PGCULLED);

L
Lee Schermerhorn 已提交
598 599 600
	put_page(page);		/* drop ref from isolate */
}

601 602 603
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
604
	PAGEREF_KEEP,
605 606 607 608 609 610
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
611
	int referenced_ptes, referenced_page;
612 613
	unsigned long vm_flags;

614 615
	referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
	referenced_page = TestClearPageReferenced(page);
616 617

	/* Lumpy reclaim - ignore references */
618
	if (sc->lumpy_reclaim_mode != LUMPY_MODE_NONE)
619 620 621 622 623 624 625 626 627
		return PAGEREF_RECLAIM;

	/*
	 * Mlock lost the isolation race with us.  Let try_to_unmap()
	 * move the page to the unevictable list.
	 */
	if (vm_flags & VM_LOCKED)
		return PAGEREF_RECLAIM;

628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651
	if (referenced_ptes) {
		if (PageAnon(page))
			return PAGEREF_ACTIVATE;
		/*
		 * All mapped pages start out with page table
		 * references from the instantiating fault, so we need
		 * to look twice if a mapped file page is used more
		 * than once.
		 *
		 * Mark it and spare it for another trip around the
		 * inactive list.  Another page table reference will
		 * lead to its activation.
		 *
		 * Note: the mark is set for activated pages as well
		 * so that recently deactivated but used pages are
		 * quickly recovered.
		 */
		SetPageReferenced(page);

		if (referenced_page)
			return PAGEREF_ACTIVATE;

		return PAGEREF_KEEP;
	}
652 653

	/* Reclaim if clean, defer dirty pages to writeback */
654
	if (referenced_page && !PageSwapBacked(page))
655 656 657
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
658 659
}

660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677
static noinline_for_stack void free_page_list(struct list_head *free_pages)
{
	struct pagevec freed_pvec;
	struct page *page, *tmp;

	pagevec_init(&freed_pvec, 1);

	list_for_each_entry_safe(page, tmp, free_pages, lru) {
		list_del(&page->lru);
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
	}

	pagevec_free(&freed_pvec);
}

L
Linus Torvalds 已提交
678
/*
A
Andrew Morton 已提交
679
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
680
 */
A
Andrew Morton 已提交
681
static unsigned long shrink_page_list(struct list_head *page_list,
682
				      struct zone *zone,
683
				      struct scan_control *sc)
L
Linus Torvalds 已提交
684 685
{
	LIST_HEAD(ret_pages);
686
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
687
	int pgactivate = 0;
688 689
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
690
	unsigned long nr_reclaimed = 0;
L
Linus Torvalds 已提交
691 692 693 694

	cond_resched();

	while (!list_empty(page_list)) {
695
		enum page_references references;
L
Linus Torvalds 已提交
696 697 698 699 700 701 702 703 704
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;

		cond_resched();

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

N
Nick Piggin 已提交
705
		if (!trylock_page(page))
L
Linus Torvalds 已提交
706 707
			goto keep;

N
Nick Piggin 已提交
708
		VM_BUG_ON(PageActive(page));
709
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
710 711

		sc->nr_scanned++;
712

N
Nick Piggin 已提交
713 714
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
715

716
		if (!sc->may_unmap && page_mapped(page))
717 718
			goto keep_locked;

L
Linus Torvalds 已提交
719 720 721 722
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

723 724 725 726 727 728 729 730 731 732 733 734
		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.
			 */
735 736
			if (sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC &&
			    may_enter_fs)
737
				wait_on_page_writeback(page);
738 739 740 741
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
742
		}
L
Linus Torvalds 已提交
743

744 745 746
		references = page_check_references(page, sc);
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
747
			goto activate_locked;
748 749
		case PAGEREF_KEEP:
			goto keep_locked;
750 751 752 753
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
754 755 756 757 758

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
759
		if (PageAnon(page) && !PageSwapCache(page)) {
760 761
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
762
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
763
				goto activate_locked;
764
			may_enter_fs = 1;
N
Nick Piggin 已提交
765
		}
L
Linus Torvalds 已提交
766 767 768 769 770 771 772 773

		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) {
774
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
775 776 777 778
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
779 780
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
781 782 783 784 785 786
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
787 788
			nr_dirty++;

789
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
790
				goto keep_locked;
791
			if (!may_enter_fs)
L
Linus Torvalds 已提交
792
				goto keep_locked;
793
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
794 795 796
				goto keep_locked;

			/* Page is dirty, try to write it out here */
797
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
798
			case PAGE_KEEP:
799
				nr_congested++;
L
Linus Torvalds 已提交
800 801 802 803
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
804 805 806
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
807
					goto keep;
808

L
Linus Torvalds 已提交
809 810 811 812
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
813
				if (!trylock_page(page))
L
Linus Torvalds 已提交
814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832
					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
L
Lee Schermerhorn 已提交
833
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
834 835 836 837 838 839 840 841 842 843
		 * 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.
		 */
844
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
845 846
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
			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
863 864
		}

N
Nick Piggin 已提交
865
		if (!mapping || !__remove_mapping(mapping, page))
866
			goto keep_locked;
L
Linus Torvalds 已提交
867

N
Nick Piggin 已提交
868 869 870 871 872 873 874 875
		/*
		 * At this point, we have no other references and there is
		 * no way to pick any more up (removed from LRU, removed
		 * from pagecache). Can use non-atomic bitops now (and
		 * we obviously don't have to worry about waking up a process
		 * waiting on the page lock, because there are no references.
		 */
		__clear_page_locked(page);
N
Nick Piggin 已提交
876
free_it:
877
		nr_reclaimed++;
878 879 880 881 882 883

		/*
		 * Is there need to periodically free_page_list? It would
		 * appear not as the counts should be low
		 */
		list_add(&page->lru, &free_pages);
L
Linus Torvalds 已提交
884 885
		continue;

N
Nick Piggin 已提交
886
cull_mlocked:
887 888
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
889 890
		unlock_page(page);
		putback_lru_page(page);
891
		disable_lumpy_reclaim_mode(sc);
N
Nick Piggin 已提交
892 893
		continue;

L
Linus Torvalds 已提交
894
activate_locked:
895 896
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
897
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
898
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
899 900 901 902 903
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
904 905
		disable_lumpy_reclaim_mode(sc);
keep_lumpy:
L
Linus Torvalds 已提交
906
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
907
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
908
	}
909

910 911 912 913 914 915 916 917 918
	/*
	 * Tag a zone as congested if all the dirty pages encountered were
	 * backed by a congested BDI. In this case, reclaimers should just
	 * back off and wait for congestion to clear because further reclaim
	 * will encounter the same problem
	 */
	if (nr_dirty == nr_congested)
		zone_set_flag(zone, ZONE_CONGESTED);

919 920
	free_page_list(&free_pages);

L
Linus Torvalds 已提交
921
	list_splice(&ret_pages, page_list);
922
	count_vm_events(PGACTIVATE, pgactivate);
923
	return nr_reclaimed;
L
Linus Torvalds 已提交
924 925
}

A
Andy Whitcroft 已提交
926 927 928 929 930 931 932 933 934 935
/*
 * 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.
 */
936
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
937 938 939 940 941 942 943 944 945 946 947 948 949 950 951
{
	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;

952
	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
953 954
		return ret;

L
Lee Schermerhorn 已提交
955 956 957 958 959 960 961 962
	/*
	 * When this function is being called for lumpy reclaim, we
	 * initially look into all LRU pages, active, inactive and
	 * unevictable; only give shrink_page_list evictable pages.
	 */
	if (PageUnevictable(page))
		return ret;

A
Andy Whitcroft 已提交
963
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
964

A
Andy Whitcroft 已提交
965 966 967 968 969 970 971 972 973 974 975 976 977
	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
978 979 980 981 982 983 984 985 986 987 988 989 990 991
/*
 * 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
992 993
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
994
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
995 996 997
 *
 * returns how many pages were moved onto *@dst.
 */
998 999
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1000
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
1001
{
1002
	unsigned long nr_taken = 0;
1003 1004 1005
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1006
	unsigned long scan;
L
Linus Torvalds 已提交
1007

1008
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1009 1010 1011 1012 1013 1014
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1015 1016 1017
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1018
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1019

1020
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1021 1022
		case 0:
			list_move(&page->lru, dst);
1023
			mem_cgroup_del_lru(page);
1024
			nr_taken++;
A
Andy Whitcroft 已提交
1025 1026 1027 1028 1029
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
1030
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
1031
			continue;
1032

A
Andy Whitcroft 已提交
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
		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);
1065

A
Andy Whitcroft 已提交
1066 1067
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1068
				break;
1069 1070 1071 1072 1073 1074 1075

			/*
			 * If we don't have enough swap space, reclaiming of
			 * anon page which don't already have a swap slot is
			 * pointless.
			 */
			if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1076 1077
			    !PageSwapCache(cursor_page))
				break;
1078

1079
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
1080
				list_move(&cursor_page->lru, dst);
1081
				mem_cgroup_del_lru(cursor_page);
A
Andy Whitcroft 已提交
1082
				nr_taken++;
1083 1084 1085
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1086
				scan++;
1087
			} else {
1088 1089 1090 1091
				/* the page is freed already. */
				if (!page_count(cursor_page))
					continue;
				break;
A
Andy Whitcroft 已提交
1092 1093
			}
		}
1094 1095 1096 1097

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1098 1099 1100
	}

	*scanned = scan;
1101 1102 1103 1104 1105 1106

	trace_mm_vmscan_lru_isolate(order,
			nr_to_scan, scan,
			nr_taken,
			nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
			mode);
L
Linus Torvalds 已提交
1107 1108 1109
	return nr_taken;
}

1110 1111 1112 1113
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
1114
					int active, int file)
1115
{
1116
	int lru = LRU_BASE;
1117
	if (active)
1118 1119 1120 1121
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1122
								mode, file);
1123 1124
}

A
Andy Whitcroft 已提交
1125 1126 1127 1128
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1129 1130
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1131 1132
{
	int nr_active = 0;
1133
	int lru;
A
Andy Whitcroft 已提交
1134 1135
	struct page *page;

1136
	list_for_each_entry(page, page_list, lru) {
1137
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1138
		if (PageActive(page)) {
1139
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1140 1141 1142
			ClearPageActive(page);
			nr_active++;
		}
1143 1144
		if (count)
			count[lru]++;
1145
	}
A
Andy Whitcroft 已提交
1146 1147 1148 1149

	return nr_active;
}

1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160
/**
 * 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
L
Lee Schermerhorn 已提交
1161 1162 1163
 * the active list, it will have PageActive set.  If it was found on
 * the unevictable list, it will have the PageUnevictable bit set. That flag
 * may need to be cleared by the caller before letting the page go.
1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183
 *
 * 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)) {
L
Lee Schermerhorn 已提交
1184
			int lru = page_lru(page);
1185 1186
			ret = 0;
			ClearPageLRU(page);
1187 1188

			del_page_from_lru_list(zone, page, lru);
1189 1190 1191 1192 1193 1194
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219
/*
 * Are there way too many processes in the direct reclaim path already?
 */
static int too_many_isolated(struct zone *zone, int file,
		struct scan_control *sc)
{
	unsigned long inactive, isolated;

	if (current_is_kswapd())
		return 0;

	if (!scanning_global_lru(sc))
		return 0;

	if (file) {
		inactive = zone_page_state(zone, NR_INACTIVE_FILE);
		isolated = zone_page_state(zone, NR_ISOLATED_FILE);
	} else {
		inactive = zone_page_state(zone, NR_INACTIVE_ANON);
		isolated = zone_page_state(zone, NR_ISOLATED_ANON);
	}

	return isolated > inactive;
}

1220 1221 1222 1223
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1224
putback_lru_pages(struct zone *zone, struct scan_control *sc,
1225 1226 1227 1228 1229
				unsigned long nr_anon, unsigned long nr_file,
				struct list_head *page_list)
{
	struct page *page;
	struct pagevec pvec;
1230
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268

	pagevec_init(&pvec, 1);

	/*
	 * Put back any unfreeable pages.
	 */
	spin_lock(&zone->lru_lock);
	while (!list_empty(page_list)) {
		int lru;
		page = lru_to_page(page_list);
		VM_BUG_ON(PageLRU(page));
		list_del(&page->lru);
		if (unlikely(!page_evictable(page, NULL))) {
			spin_unlock_irq(&zone->lru_lock);
			putback_lru_page(page);
			spin_lock_irq(&zone->lru_lock);
			continue;
		}
		SetPageLRU(page);
		lru = page_lru(page);
		add_page_to_lru_list(zone, page, lru);
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
			reclaim_stat->recent_rotated[file]++;
		}
		if (!pagevec_add(&pvec, page)) {
			spin_unlock_irq(&zone->lru_lock);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);

	spin_unlock_irq(&zone->lru_lock);
	pagevec_release(&pvec);
}

1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299
static noinline_for_stack void update_isolated_counts(struct zone *zone,
					struct scan_control *sc,
					unsigned long *nr_anon,
					unsigned long *nr_file,
					struct list_head *isolated_list)
{
	unsigned long nr_active;
	unsigned int count[NR_LRU_LISTS] = { 0, };
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);

	nr_active = clear_active_flags(isolated_list, count);
	__count_vm_events(PGDEACTIVATE, nr_active);

	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
			      -count[LRU_ACTIVE_FILE]);
	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
			      -count[LRU_INACTIVE_FILE]);
	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
			      -count[LRU_ACTIVE_ANON]);
	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
			      -count[LRU_INACTIVE_ANON]);

	*nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
	*nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
	__mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);

	reclaim_stat->recent_scanned[0] += *nr_anon;
	reclaim_stat->recent_scanned[1] += *nr_file;
}

1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319
/*
 * Returns true if the caller should wait to clean dirty/writeback pages.
 *
 * If we are direct reclaiming for contiguous pages and we do not reclaim
 * everything in the list, try again and wait for writeback IO to complete.
 * This will stall high-order allocations noticeably. Only do that when really
 * need to free the pages under high memory pressure.
 */
static inline bool should_reclaim_stall(unsigned long nr_taken,
					unsigned long nr_freed,
					int priority,
					struct scan_control *sc)
{
	int lumpy_stall_priority;

	/* kswapd should not stall on sync IO */
	if (current_is_kswapd())
		return false;

	/* Only stall on lumpy reclaim */
1320
	if (sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
		return false;

	/* If we have relaimed everything on the isolated list, no stall */
	if (nr_freed == nr_taken)
		return false;

	/*
	 * For high-order allocations, there are two stall thresholds.
	 * High-cost allocations stall immediately where as lower
	 * order allocations such as stacks require the scanning
	 * priority to be much higher before stalling.
	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
		lumpy_stall_priority = DEF_PRIORITY;
	else
		lumpy_stall_priority = DEF_PRIORITY / 3;

	return priority <= lumpy_stall_priority;
}

L
Linus Torvalds 已提交
1341
/*
A
Andrew Morton 已提交
1342 1343
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1344
 */
1345 1346 1347
static noinline_for_stack unsigned long
shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1348 1349
{
	LIST_HEAD(page_list);
1350
	unsigned long nr_scanned;
1351
	unsigned long nr_reclaimed = 0;
1352 1353 1354
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1355

1356
	while (unlikely(too_many_isolated(zone, file, sc))) {
1357
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1358 1359 1360 1361 1362 1363

		/* We are about to die and free our memory. Return now. */
		if (fatal_signal_pending(current))
			return SWAP_CLUSTER_MAX;
	}

1364
	set_lumpy_reclaim_mode(priority, sc, false);
L
Linus Torvalds 已提交
1365 1366
	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1367

1368 1369 1370
	if (scanning_global_lru(sc)) {
		nr_taken = isolate_pages_global(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1371 1372
			sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
					ISOLATE_INACTIVE : ISOLATE_BOTH,
1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383
			zone, 0, file);
		zone->pages_scanned += nr_scanned;
		if (current_is_kswapd())
			__count_zone_vm_events(PGSCAN_KSWAPD, zone,
					       nr_scanned);
		else
			__count_zone_vm_events(PGSCAN_DIRECT, zone,
					       nr_scanned);
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
			&page_list, &nr_scanned, sc->order,
1384 1385
			sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
					ISOLATE_INACTIVE : ISOLATE_BOTH,
1386 1387 1388 1389 1390 1391 1392
			zone, sc->mem_cgroup,
			0, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
	}
1393

1394 1395 1396 1397
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1398

1399
	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1400

1401
	spin_unlock_irq(&zone->lru_lock);
1402

1403
	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1404

1405 1406
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1407
		set_lumpy_reclaim_mode(priority, sc, true);
1408
		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1409
	}
1410

1411 1412 1413 1414
	local_irq_disable();
	if (current_is_kswapd())
		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
N
Nick Piggin 已提交
1415

1416
	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1417 1418 1419 1420 1421 1422

	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
		trace_shrink_flags(file, sc->lumpy_reclaim_mode));
1423
	return nr_reclaimed;
L
Linus Torvalds 已提交
1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442
}

/*
 * 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.
 */
1443

1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475
static void move_active_pages_to_lru(struct zone *zone,
				     struct list_head *list,
				     enum lru_list lru)
{
	unsigned long pgmoved = 0;
	struct pagevec pvec;
	struct page *page;

	pagevec_init(&pvec, 1);

	while (!list_empty(list)) {
		page = lru_to_page(list);

		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);

		list_move(&page->lru, &zone->lru[lru].list);
		mem_cgroup_add_lru_list(page, lru);
		pgmoved++;

		if (!pagevec_add(&pvec, page) || list_empty(list)) {
			spin_unlock_irq(&zone->lru_lock);
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	if (!is_active_lru(lru))
		__count_vm_events(PGDEACTIVATE, pgmoved);
}
1476

A
Andrew Morton 已提交
1477
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1478
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1479
{
1480
	unsigned long nr_taken;
1481
	unsigned long pgscanned;
1482
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1483
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1484
	LIST_HEAD(l_active);
1485
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1486
	struct page *page;
1487
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1488
	unsigned long nr_rotated = 0;
L
Linus Torvalds 已提交
1489 1490 1491

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1492
	if (scanning_global_lru(sc)) {
1493 1494 1495 1496
		nr_taken = isolate_pages_global(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						1, file);
1497
		zone->pages_scanned += pgscanned;
1498 1499 1500 1501 1502 1503 1504 1505 1506
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
						&pgscanned, sc->order,
						ISOLATE_ACTIVE, zone,
						sc->mem_cgroup, 1, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
1507
	}
1508

1509
	reclaim_stat->recent_scanned[file] += nr_taken;
1510

1511
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1512
	if (file)
1513
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1514
	else
1515
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1516
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1517 1518 1519 1520 1521 1522
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1523

L
Lee Schermerhorn 已提交
1524 1525 1526 1527 1528
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1529
		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1530
			nr_rotated++;
1531 1532 1533 1534 1535 1536 1537 1538 1539
			/*
			 * Identify referenced, file-backed active pages and
			 * give them one more trip around the active list. So
			 * that executable code get better chances to stay in
			 * memory under moderate memory pressure.  Anon pages
			 * are not likely to be evicted by use-once streaming
			 * IO, plus JVM can create lots of anon VM_EXEC pages,
			 * so we ignore them here.
			 */
1540
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1541 1542 1543 1544
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1545

1546
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1547 1548 1549
		list_add(&page->lru, &l_inactive);
	}

1550
	/*
1551
	 * Move pages back to the lru list.
1552
	 */
1553
	spin_lock_irq(&zone->lru_lock);
1554
	/*
1555 1556 1557 1558
	 * Count referenced pages from currently used mappings as rotated,
	 * even though only some of them are actually re-activated.  This
	 * helps balance scan pressure between file and anonymous pages in
	 * get_scan_ratio.
1559
	 */
1560
	reclaim_stat->recent_rotated[file] += nr_rotated;
1561

1562 1563 1564 1565
	move_active_pages_to_lru(zone, &l_active,
						LRU_ACTIVE + file * LRU_FILE);
	move_active_pages_to_lru(zone, &l_inactive,
						LRU_BASE   + file * LRU_FILE);
K
KOSAKI Motohiro 已提交
1566
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1567
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1568 1569
}

1570
#ifdef CONFIG_SWAP
1571
static int inactive_anon_is_low_global(struct zone *zone)
1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_ANON);
	inactive = zone_page_state(zone, NR_INACTIVE_ANON);

	if (inactive * zone->inactive_ratio < active)
		return 1;

	return 0;
}

1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

1596 1597 1598 1599 1600 1601 1602
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1603
	if (scanning_global_lru(sc))
1604 1605
		low = inactive_anon_is_low_global(zone);
	else
1606
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1607 1608
	return low;
}
1609 1610 1611 1612 1613 1614 1615
#else
static inline int inactive_anon_is_low(struct zone *zone,
					struct scan_control *sc)
{
	return 0;
}
#endif
1616

1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652
static int inactive_file_is_low_global(struct zone *zone)
{
	unsigned long active, inactive;

	active = zone_page_state(zone, NR_ACTIVE_FILE);
	inactive = zone_page_state(zone, NR_INACTIVE_FILE);

	return (active > inactive);
}

/**
 * inactive_file_is_low - check if file pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * When the system is doing streaming IO, memory pressure here
 * ensures that active file pages get deactivated, until more
 * than half of the file pages are on the inactive list.
 *
 * Once we get to that situation, protect the system's working
 * set from being evicted by disabling active file page aging.
 *
 * This uses a different ratio than the anonymous pages, because
 * the page cache uses a use-once replacement algorithm.
 */
static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

	if (scanning_global_lru(sc))
		low = inactive_file_is_low_global(zone);
	else
		low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
	return low;
}

1653 1654 1655 1656 1657 1658 1659 1660 1661
static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
				int file)
{
	if (file)
		return inactive_file_is_low(zone, sc);
	else
		return inactive_anon_is_low(zone, sc);
}

1662
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1663 1664
	struct zone *zone, struct scan_control *sc, int priority)
{
1665 1666
	int file = is_file_lru(lru);

1667 1668 1669
	if (is_active_lru(lru)) {
		if (inactive_list_is_low(zone, sc, file))
		    shrink_active_list(nr_to_scan, zone, sc, priority, file);
1670 1671 1672
		return 0;
	}

R
Rik van Riel 已提交
1673
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1674 1675
}

1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695
/*
 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
 * until we collected @swap_cluster_max pages to scan.
 */
static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
				       unsigned long *nr_saved_scan)
{
	unsigned long nr;

	*nr_saved_scan += nr_to_scan;
	nr = *nr_saved_scan;

	if (nr >= SWAP_CLUSTER_MAX)
		*nr_saved_scan = 0;
	else
		nr = 0;

	return nr;
}

1696 1697 1698 1699 1700 1701
/*
 * Determine how aggressively the anon and file LRU lists should be
 * scanned.  The relative value of each set of LRU lists is determined
 * by looking at the fraction of the pages scanned we did rotate back
 * onto the active list instead of evict.
 *
1702
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1703
 */
1704 1705
static void get_scan_count(struct zone *zone, struct scan_control *sc,
					unsigned long *nr, int priority)
1706 1707 1708 1709
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1710
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722
	u64 fraction[2], denominator;
	enum lru_list l;
	int noswap = 0;

	/* If we have no swap space, do not bother scanning anon pages. */
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
		noswap = 1;
		fraction[0] = 0;
		fraction[1] = 1;
		denominator = 1;
		goto out;
	}
1723

1724 1725 1726 1727
	anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1728

1729
	if (scanning_global_lru(sc)) {
1730 1731 1732
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1733
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1734 1735 1736 1737
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1738
		}
1739 1740
	}

1741 1742 1743 1744 1745 1746 1747
	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
	anon_prio = sc->swappiness;
	file_prio = 200 - sc->swappiness;

1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758
	/*
	 * OK, so we have swap space and a fair amount of page cache
	 * pages.  We use the recently rotated / recently scanned
	 * ratios to determine how valuable each cache is.
	 *
	 * Because workloads change over time (and to avoid overflow)
	 * we keep these statistics as a floating average, which ends
	 * up weighing recent references more than old ones.
	 *
	 * anon in [0], file in [1]
	 */
1759
	spin_lock_irq(&zone->lru_lock);
1760 1761 1762
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1763 1764
	}

1765 1766 1767
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1768 1769 1770
	}

	/*
1771 1772 1773
	 * The amount of pressure on anon vs file pages is inversely
	 * proportional to the fraction of recently scanned pages on
	 * each list that were recently referenced and in active use.
1774
	 */
1775 1776
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1777

1778 1779
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1780
	spin_unlock_irq(&zone->lru_lock);
1781

1782 1783 1784 1785 1786 1787 1788
	fraction[0] = ap;
	fraction[1] = fp;
	denominator = ap + fp + 1;
out:
	for_each_evictable_lru(l) {
		int file = is_file_lru(l);
		unsigned long scan;
1789

1790 1791 1792 1793 1794 1795 1796 1797
		scan = zone_nr_lru_pages(zone, sc, l);
		if (priority || noswap) {
			scan >>= priority;
			scan = div64_u64(scan * fraction[file], denominator);
		}
		nr[l] = nr_scan_try_batch(scan,
					  &reclaim_stat->nr_saved_scan[l]);
	}
1798
}
1799

L
Linus Torvalds 已提交
1800 1801 1802
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1803
static void shrink_zone(int priority, struct zone *zone,
1804
				struct scan_control *sc)
L
Linus Torvalds 已提交
1805
{
1806
	unsigned long nr[NR_LRU_LISTS];
1807
	unsigned long nr_to_scan;
1808
	enum lru_list l;
1809
	unsigned long nr_reclaimed = sc->nr_reclaimed;
1810
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1811

1812
	get_scan_count(zone, sc, nr, priority);
L
Linus Torvalds 已提交
1813

1814 1815
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1816
		for_each_evictable_lru(l) {
1817
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
1818 1819
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
1820
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1821

1822 1823
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1824
			}
L
Linus Torvalds 已提交
1825
		}
1826 1827 1828 1829 1830 1831 1832 1833
		/*
		 * On large memory systems, scan >> priority can become
		 * really large. This is fine for the starting priority;
		 * we want to put equal scanning pressure on each zone.
		 * However, if the VM has a harder time of freeing pages,
		 * with multiple processes reclaiming pages, the total
		 * freeing target can get unreasonably large.
		 */
1834
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1835
			break;
L
Linus Torvalds 已提交
1836 1837
	}

1838 1839
	sc->nr_reclaimed = nr_reclaimed;

1840 1841 1842 1843
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1844
	if (inactive_anon_is_low(zone, sc))
1845 1846
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1847
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1848 1849 1850 1851 1852 1853 1854
}

/*
 * 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.
 *
1855 1856
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
1857 1858
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
1859 1860 1861
 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
 *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
 *    zone defense algorithm.
L
Linus Torvalds 已提交
1862 1863 1864 1865
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1866
static void shrink_zones(int priority, struct zonelist *zonelist,
1867
					struct scan_control *sc)
L
Linus Torvalds 已提交
1868
{
1869
	struct zoneref *z;
1870
	struct zone *zone;
1871

1872 1873
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
1874
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1875
			continue;
1876 1877 1878 1879
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1880
		if (scanning_global_lru(sc)) {
1881 1882
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
1883
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1884 1885
				continue;	/* Let kswapd poll it */
		}
1886

1887
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1888
	}
1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919
}

static bool zone_reclaimable(struct zone *zone)
{
	return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
}

/*
 * As hibernation is going on, kswapd is freezed so that it can't mark
 * the zone into all_unreclaimable. It can't handle OOM during hibernation.
 * So let's check zone's unreclaimable in direct reclaim as well as kswapd.
 */
static bool all_unreclaimable(struct zonelist *zonelist,
		struct scan_control *sc)
{
	struct zoneref *z;
	struct zone *zone;
	bool all_unreclaimable = true;

	for_each_zone_zonelist_nodemask(zone, z, zonelist,
			gfp_zone(sc->gfp_mask), sc->nodemask) {
		if (!populated_zone(zone))
			continue;
		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
			continue;
		if (zone_reclaimable(zone)) {
			all_unreclaimable = false;
			break;
		}
	}

1920
	return all_unreclaimable;
L
Linus Torvalds 已提交
1921
}
1922

L
Linus Torvalds 已提交
1923 1924 1925 1926 1927 1928 1929 1930
/*
 * 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
1931 1932 1933 1934
 * caller can't do much about.  We kick the writeback threads 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.
1935 1936 1937
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1938
 */
1939
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1940
					struct scan_control *sc)
L
Linus Torvalds 已提交
1941 1942
{
	int priority;
1943
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1944
	struct reclaim_state *reclaim_state = current->reclaim_state;
1945
	struct zoneref *z;
1946
	struct zone *zone;
1947
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
1948

1949
	get_mems_allowed();
1950 1951
	delayacct_freepages_start();

1952
	if (scanning_global_lru(sc))
1953
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
1954 1955

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1956
		sc->nr_scanned = 0;
1957 1958
		if (!priority)
			disable_swap_token();
1959
		shrink_zones(priority, zonelist, sc);
1960 1961 1962 1963
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1964
		if (scanning_global_lru(sc)) {
1965
			unsigned long lru_pages = 0;
1966 1967
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
1968 1969 1970 1971 1972 1973
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

1974
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1975
			if (reclaim_state) {
1976
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1977 1978
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1979
		}
1980
		total_scanned += sc->nr_scanned;
1981
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
1982 1983 1984 1985 1986 1987 1988 1989 1990
			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.
		 */
1991 1992
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
1993
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1994
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1995 1996 1997
		}

		/* Take a nap, wait for some writeback to complete */
1998
		if (!sc->hibernation_mode && sc->nr_scanned &&
1999 2000 2001 2002 2003 2004 2005
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
							NULL, &preferred_zone);
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2006
	}
2007

L
Linus Torvalds 已提交
2008
out:
2009
	delayacct_freepages_end();
2010
	put_mems_allowed();
2011

2012 2013 2014 2015
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

	/* top priority shrink_zones still had more to do? don't OOM, then */
2016
	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2017 2018 2019
		return 1;

	return 0;
L
Linus Torvalds 已提交
2020 2021
}

2022
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2023
				gfp_t gfp_mask, nodemask_t *nodemask)
2024
{
2025
	unsigned long nr_reclaimed;
2026 2027 2028
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2029
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2030
		.may_unmap = 1,
2031
		.may_swap = 1,
2032 2033 2034
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
2035
		.nodemask = nodemask,
2036 2037
	};

2038 2039 2040 2041 2042 2043 2044 2045 2046
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2047 2048
}

2049
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2050

2051 2052 2053
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						unsigned int swappiness,
2054
						struct zone *zone)
2055 2056
{
	struct scan_control sc = {
2057
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2058 2059 2060 2061 2062 2063 2064 2065 2066
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.swappiness = swappiness,
		.order = 0,
		.mem_cgroup = mem,
	};
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2067 2068 2069 2070 2071

	trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
						      sc.may_writepage,
						      sc.gfp_mask);

2072 2073 2074 2075 2076 2077 2078 2079
	/*
	 * NOTE: Although we can get the priority field, using it
	 * here is not a good idea, since it limits the pages we can scan.
	 * if we don't reclaim here, the shrink_zone from balance_pgdat
	 * will pick up pages from other mem cgroup's as well. We hack
	 * the priority and make it zero.
	 */
	shrink_zone(0, zone, &sc);
2080 2081 2082

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2083 2084 2085
	return sc.nr_reclaimed;
}

2086
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
2087 2088 2089
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
2090
{
2091
	struct zonelist *zonelist;
2092
	unsigned long nr_reclaimed;
2093 2094
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2095
		.may_unmap = 1,
2096
		.may_swap = !noswap,
2097
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
2098
		.swappiness = swappiness,
2099 2100
		.order = 0,
		.mem_cgroup = mem_cont,
2101
		.nodemask = NULL, /* we don't care the placement */
2102 2103
	};

2104 2105 2106
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2107 2108 2109 2110 2111 2112 2113 2114 2115 2116

	trace_mm_vmscan_memcg_reclaim_begin(0,
					    sc.may_writepage,
					    sc.gfp_mask);

	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2117 2118 2119
}
#endif

2120
/* is kswapd sleeping prematurely? */
2121
static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
2122
{
2123
	int i;
2124 2125 2126 2127 2128 2129

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
		return 1;

	/* If after HZ/10, a zone is below the high mark, it's premature */
2130 2131 2132 2133 2134 2135
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2136
		if (zone->all_unreclaimable)
2137 2138
			continue;

2139 2140 2141
		if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
								0, 0))
			return 1;
2142
	}
2143 2144 2145 2146

	return 0;
}

L
Linus Torvalds 已提交
2147 2148
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2149
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161
 *
 * 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
2162 2163 2164 2165 2166
 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
 * found to have free_pages <= high_wmark_pages(zone), 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.
L
Linus Torvalds 已提交
2167
 */
2168
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
2169 2170 2171 2172
{
	int all_zones_ok;
	int priority;
	int i;
2173
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2174
	struct reclaim_state *reclaim_state = current->reclaim_state;
2175 2176
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2177
		.may_unmap = 1,
2178
		.may_swap = 1,
2179 2180 2181 2182 2183
		/*
		 * kswapd doesn't want to be bailed out while reclaim. because
		 * we want to put equal scanning pressure on each zone.
		 */
		.nr_to_reclaim = ULONG_MAX,
2184
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
2185
		.order = order,
2186
		.mem_cgroup = NULL,
2187
	};
L
Linus Torvalds 已提交
2188 2189
loop_again:
	total_scanned = 0;
2190
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2191
	sc.may_writepage = !laptop_mode;
2192
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2193 2194 2195 2196

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
		unsigned long lru_pages = 0;
2197
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2198

2199 2200 2201 2202
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
2203 2204
		all_zones_ok = 1;

2205 2206 2207 2208 2209 2210
		/*
		 * 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
2211

2212 2213
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2214

2215
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2216
				continue;
L
Linus Torvalds 已提交
2217

2218 2219 2220 2221
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2222
			if (inactive_anon_is_low(zone, &sc))
2223 2224 2225
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

2226 2227
			if (!zone_watermark_ok(zone, order,
					high_wmark_pages(zone), 0, 0)) {
2228
				end_zone = i;
A
Andrew Morton 已提交
2229
				break;
L
Linus Torvalds 已提交
2230 2231
			}
		}
A
Andrew Morton 已提交
2232 2233 2234
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2235 2236 2237
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2238
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251
		}

		/*
		 * 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;
2252
			int nr_slab;
L
Linus Torvalds 已提交
2253

2254
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2255 2256
				continue;

2257
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2258 2259 2260
				continue;

			sc.nr_scanned = 0;
2261 2262 2263 2264 2265

			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 * For now we ignore the return value
			 */
2266 2267
			mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);

2268 2269 2270 2271
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
2272 2273
			if (!zone_watermark_ok(zone, order,
					8*high_wmark_pages(zone), end_zone, 0))
2274
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
2275
			reclaim_state->reclaimed_slab = 0;
2276 2277
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
2278
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
2279
			total_scanned += sc.nr_scanned;
2280
			if (zone->all_unreclaimable)
L
Linus Torvalds 已提交
2281
				continue;
2282
			if (nr_slab == 0 && !zone_reclaimable(zone))
2283
				zone->all_unreclaimable = 1;
L
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2284 2285 2286 2287 2288 2289
			/*
			 * 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 &&
2290
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2291
				sc.may_writepage = 1;
2292

2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303
			if (!zone_watermark_ok(zone, order,
					high_wmark_pages(zone), end_zone, 0)) {
				all_zones_ok = 0;
				/*
				 * We are still under min water mark.  This
				 * means that we have a GFP_ATOMIC allocation
				 * failure risk. Hurry up!
				 */
				if (!zone_watermark_ok(zone, order,
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2304 2305 2306 2307 2308 2309 2310 2311 2312
			} else {
				/*
				 * If a zone reaches its high watermark,
				 * consider it to be no longer congested. It's
				 * possible there are dirty pages backed by
				 * congested BDIs but as pressure is relieved,
				 * spectulatively avoid congestion waits
				 */
				zone_clear_flag(zone, ZONE_CONGESTED);
2313
			}
2314

L
Linus Torvalds 已提交
2315 2316 2317 2318 2319 2320 2321
		}
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2322 2323 2324 2325 2326 2327
		if (total_scanned && (priority < DEF_PRIORITY - 2)) {
			if (has_under_min_watermark_zone)
				count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
			else
				congestion_wait(BLK_RW_ASYNC, HZ/10);
		}
L
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2328 2329 2330 2331 2332 2333 2334

		/*
		 * 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.
		 */
2335
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2336 2337 2338 2339 2340
			break;
	}
out:
	if (!all_zones_ok) {
		cond_resched();
2341 2342 2343

		try_to_freeze();

2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360
		/*
		 * Fragmentation may mean that the system cannot be
		 * rebalanced for high-order allocations in all zones.
		 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
		 * it means the zones have been fully scanned and are still
		 * not balanced. For high-order allocations, there is
		 * little point trying all over again as kswapd may
		 * infinite loop.
		 *
		 * Instead, recheck all watermarks at order-0 as they
		 * are the most important. If watermarks are ok, kswapd will go
		 * back to sleep. High-order users can still perform direct
		 * reclaim if they wish.
		 */
		if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
			order = sc.order = 0;

L
Linus Torvalds 已提交
2361 2362 2363
		goto loop_again;
	}

2364
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
2365 2366 2367 2368
}

/*
 * The background pageout daemon, started as a kernel thread
2369
 * from the init process.
L
Linus Torvalds 已提交
2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388
 *
 * 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,
	};
2389
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2390

2391 2392
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2393
	if (!cpumask_empty(cpumask))
2394
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408
	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).
	 */
2409
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2410
	set_freezable();
L
Linus Torvalds 已提交
2411 2412 2413 2414

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
2415
		int ret;
2416

L
Linus Torvalds 已提交
2417 2418 2419 2420 2421 2422 2423 2424 2425 2426
		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 {
2427 2428 2429 2430
			if (!freezing(current) && !kthread_should_stop()) {
				long remaining = 0;

				/* Try to sleep for a short interval */
2431
				if (!sleeping_prematurely(pgdat, order, remaining)) {
2432 2433 2434 2435 2436 2437 2438 2439 2440 2441
					remaining = schedule_timeout(HZ/10);
					finish_wait(&pgdat->kswapd_wait, &wait);
					prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
				}

				/*
				 * After a short sleep, check if it was a
				 * premature sleep. If not, then go fully
				 * to sleep until explicitly woken up
				 */
2442 2443
				if (!sleeping_prematurely(pgdat, order, remaining)) {
					trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2444
					schedule();
2445
				} else {
2446
					if (remaining)
2447
						count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2448
					else
2449
						count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2450 2451
				}
			}
2452

L
Linus Torvalds 已提交
2453 2454 2455 2456
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2457 2458 2459 2460 2461 2462 2463 2464
		ret = try_to_freeze();
		if (kthread_should_stop())
			break;

		/*
		 * We can speed up thawing tasks if we don't call balance_pgdat
		 * after returning from the refrigerator
		 */
2465 2466
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2467
			balance_pgdat(pgdat, order);
2468
		}
L
Linus Torvalds 已提交
2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479
	}
	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;

2480
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2481 2482 2483
		return;

	pgdat = zone->zone_pgdat;
2484
	if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
L
Linus Torvalds 已提交
2485 2486 2487
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2488
	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2489
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2490
		return;
2491
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2492
		return;
2493
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2494 2495
}

2496 2497 2498 2499 2500 2501 2502 2503
/*
 * The reclaimable count would be mostly accurate.
 * The less reclaimable pages may be
 * - mlocked pages, which will be moved to unevictable list when encountered
 * - mapped pages, which may require several travels to be reclaimed
 * - dirty pages, which is not "instantly" reclaimable
 */
unsigned long global_reclaimable_pages(void)
2504
{
2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528
	int nr;

	nr = global_page_state(NR_ACTIVE_FILE) +
	     global_page_state(NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += global_page_state(NR_ACTIVE_ANON) +
		      global_page_state(NR_INACTIVE_ANON);

	return nr;
}

unsigned long zone_reclaimable_pages(struct zone *zone)
{
	int nr;

	nr = zone_page_state(zone, NR_ACTIVE_FILE) +
	     zone_page_state(zone, NR_INACTIVE_FILE);

	if (nr_swap_pages > 0)
		nr += zone_page_state(zone, NR_ACTIVE_ANON) +
		      zone_page_state(zone, NR_INACTIVE_ANON);

	return nr;
2529 2530
}

2531
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2532
/*
2533
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2534 2535 2536 2537 2538
 * 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
2539
 */
2540
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
2541
{
2542 2543
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
2544 2545 2546
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
2547
		.may_writepage = 1,
2548 2549 2550 2551
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.swappiness = vm_swappiness,
		.order = 0,
L
Linus Torvalds 已提交
2552
	};
2553 2554 2555
	struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
2556

2557 2558 2559 2560
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2561

2562
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2563

2564 2565 2566
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
2567

2568
	return nr_reclaimed;
L
Linus Torvalds 已提交
2569
}
2570
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
2571 2572 2573 2574 2575

/* 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. */
2576
static int __devinit cpu_callback(struct notifier_block *nfb,
2577
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2578
{
2579
	int nid;
L
Linus Torvalds 已提交
2580

2581
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2582
		for_each_node_state(nid, N_HIGH_MEMORY) {
2583
			pg_data_t *pgdat = NODE_DATA(nid);
2584 2585 2586
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2587

2588
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2589
				/* One of our CPUs online: restore mask */
2590
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2591 2592 2593 2594 2595
		}
	}
	return NOTIFY_OK;
}

2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617
/*
 * 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;
}

2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628
/*
 * Called by memory hotplug when all memory in a node is offlined.
 */
void kswapd_stop(int nid)
{
	struct task_struct *kswapd = NODE_DATA(nid)->kswapd;

	if (kswapd)
		kthread_stop(kswapd);
}

L
Linus Torvalds 已提交
2629 2630
static int __init kswapd_init(void)
{
2631
	int nid;
2632

L
Linus Torvalds 已提交
2633
	swap_setup();
2634
	for_each_node_state(nid, N_HIGH_MEMORY)
2635
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2636 2637 2638 2639 2640
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2641 2642 2643 2644 2645 2646 2647 2648 2649 2650

#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;

2651
#define RECLAIM_OFF 0
2652
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2653 2654 2655
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2656 2657 2658 2659 2660 2661 2662
/*
 * 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

2663 2664 2665 2666 2667 2668
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2669 2670 2671 2672 2673 2674
/*
 * 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;

2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716
static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
{
	unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
	unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
		zone_page_state(zone, NR_ACTIVE_FILE);

	/*
	 * It's possible for there to be more file mapped pages than
	 * accounted for by the pages on the file LRU lists because
	 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
	 */
	return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
}

/* Work out how many page cache pages we can reclaim in this reclaim_mode */
static long zone_pagecache_reclaimable(struct zone *zone)
{
	long nr_pagecache_reclaimable;
	long delta = 0;

	/*
	 * If RECLAIM_SWAP is set, then all file pages are considered
	 * potentially reclaimable. Otherwise, we have to worry about
	 * pages like swapcache and zone_unmapped_file_pages() provides
	 * a better estimate
	 */
	if (zone_reclaim_mode & RECLAIM_SWAP)
		nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
	else
		nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);

	/* If we can't clean pages, remove dirty pages from consideration */
	if (!(zone_reclaim_mode & RECLAIM_WRITE))
		delta += zone_page_state(zone, NR_FILE_DIRTY);

	/* Watch for any possible underflows due to delta */
	if (unlikely(delta > nr_pagecache_reclaimable))
		delta = nr_pagecache_reclaimable;

	return nr_pagecache_reclaimable - delta;
}

2717 2718 2719
/*
 * Try to free up some pages from this zone through reclaim.
 */
2720
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2721
{
2722
	/* Minimum pages needed in order to stay on node */
2723
	const unsigned long nr_pages = 1 << order;
2724 2725
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2726
	int priority;
2727 2728
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2729
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2730
		.may_swap = 1,
2731 2732
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
2733
		.gfp_mask = gfp_mask,
2734
		.swappiness = vm_swappiness,
2735
		.order = order,
2736
	};
2737
	unsigned long nr_slab_pages0, nr_slab_pages1;
2738 2739

	cond_resched();
2740 2741 2742 2743 2744 2745
	/*
	 * 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;
2746
	lockdep_set_current_reclaim_state(gfp_mask);
2747 2748
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2749

2750
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2751 2752 2753 2754 2755 2756
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2757
			shrink_zone(priority, zone, &sc);
2758
			priority--;
2759
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2760
	}
2761

2762 2763
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
2764
		/*
2765
		 * shrink_slab() does not currently allow us to determine how
2766 2767 2768 2769
		 * 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.
2770
		 *
2771 2772
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2773
		 */
2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
			if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages))
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
2787 2788 2789 2790 2791

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2792 2793 2794
		nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
		if (nr_slab_pages1 < nr_slab_pages0)
			sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
2795 2796
	}

2797
	p->reclaim_state = NULL;
2798
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2799
	lockdep_clear_current_reclaim_state();
2800
	return sc.nr_reclaimed >= nr_pages;
2801
}
2802 2803 2804 2805

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2806
	int ret;
2807 2808

	/*
2809 2810
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2811
	 *
2812 2813 2814 2815 2816
	 * 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.
2817
	 */
2818 2819
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2820
		return ZONE_RECLAIM_FULL;
2821

2822
	if (zone->all_unreclaimable)
2823
		return ZONE_RECLAIM_FULL;
2824

2825
	/*
2826
	 * Do not scan if the allocation should not be delayed.
2827
	 */
2828
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2829
		return ZONE_RECLAIM_NOSCAN;
2830 2831 2832 2833 2834 2835 2836

	/*
	 * 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.
	 */
2837
	node_id = zone_to_nid(zone);
2838
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2839
		return ZONE_RECLAIM_NOSCAN;
2840 2841

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2842 2843
		return ZONE_RECLAIM_NOSCAN;

2844 2845 2846
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

2847 2848 2849
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

2850
	return ret;
2851
}
2852
#endif
L
Lee Schermerhorn 已提交
2853 2854 2855 2856 2857 2858 2859

/*
 * page_evictable - test whether a page is evictable
 * @page: the page to test
 * @vma: the VMA in which the page is or will be mapped, may be NULL
 *
 * Test whether page is evictable--i.e., should be placed on active/inactive
N
Nick Piggin 已提交
2860 2861
 * lists vs unevictable list.  The vma argument is !NULL when called from the
 * fault path to determine how to instantate a new page.
L
Lee Schermerhorn 已提交
2862 2863
 *
 * Reasons page might not be evictable:
2864
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2865
 * (2) page is part of an mlocked VMA
2866
 *
L
Lee Schermerhorn 已提交
2867 2868 2869 2870
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2871 2872 2873
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2874 2875
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2876 2877 2878

	return 1;
}
2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897

/**
 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
 * @page: page to check evictability and move to appropriate lru list
 * @zone: zone page is in
 *
 * Checks a page for evictability and moves the page to the appropriate
 * zone lru list.
 *
 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
 * have PageUnevictable set.
 */
static void check_move_unevictable_page(struct page *page, struct zone *zone)
{
	VM_BUG_ON(PageActive(page));

retry:
	ClearPageUnevictable(page);
	if (page_evictable(page, NULL)) {
2898
		enum lru_list l = page_lru_base_type(page);
2899

2900 2901
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2902
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2903 2904 2905 2906 2907 2908 2909 2910
		__inc_zone_state(zone, NR_INACTIVE_ANON + l);
		__count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		/*
		 * rotate unevictable list
		 */
		SetPageUnevictable(page);
		list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
K
KAMEZAWA Hiroyuki 已提交
2911
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970
		if (page_evictable(page, NULL))
			goto retry;
	}
}

/**
 * scan_mapping_unevictable_pages - scan an address space for evictable pages
 * @mapping: struct address_space to scan for evictable pages
 *
 * Scan all pages in mapping.  Check unevictable pages for
 * evictability and move them to the appropriate zone lru list.
 */
void scan_mapping_unevictable_pages(struct address_space *mapping)
{
	pgoff_t next = 0;
	pgoff_t end   = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
			 PAGE_CACHE_SHIFT;
	struct zone *zone;
	struct pagevec pvec;

	if (mapping->nrpages == 0)
		return;

	pagevec_init(&pvec, 0);
	while (next < end &&
		pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
		int i;
		int pg_scanned = 0;

		zone = NULL;

		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];
			pgoff_t page_index = page->index;
			struct zone *pagezone = page_zone(page);

			pg_scanned++;
			if (page_index > next)
				next = page_index;
			next++;

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irq(&zone->lru_lock);
				zone = pagezone;
				spin_lock_irq(&zone->lru_lock);
			}

			if (PageLRU(page) && PageUnevictable(page))
				check_move_unevictable_page(page, zone);
		}
		if (zone)
			spin_unlock_irq(&zone->lru_lock);
		pagevec_release(&pvec);

		count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
	}

}
2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982

/**
 * scan_zone_unevictable_pages - check unevictable list for evictable pages
 * @zone - zone of which to scan the unevictable list
 *
 * Scan @zone's unevictable LRU lists to check for pages that have become
 * evictable.  Move those that have to @zone's inactive list where they
 * become candidates for reclaim, unless shrink_inactive_zone() decides
 * to reactivate them.  Pages that are still unevictable are rotated
 * back onto @zone's unevictable list.
 */
#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2983
static void scan_zone_unevictable_pages(struct zone *zone)
2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024
{
	struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
	unsigned long scan;
	unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);

	while (nr_to_scan > 0) {
		unsigned long batch_size = min(nr_to_scan,
						SCAN_UNEVICTABLE_BATCH_SIZE);

		spin_lock_irq(&zone->lru_lock);
		for (scan = 0;  scan < batch_size; scan++) {
			struct page *page = lru_to_page(l_unevictable);

			if (!trylock_page(page))
				continue;

			prefetchw_prev_lru_page(page, l_unevictable, flags);

			if (likely(PageLRU(page) && PageUnevictable(page)))
				check_move_unevictable_page(page, zone);

			unlock_page(page);
		}
		spin_unlock_irq(&zone->lru_lock);

		nr_to_scan -= batch_size;
	}
}


/**
 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
 *
 * A really big hammer:  scan all zones' unevictable LRU lists to check for
 * pages that have become evictable.  Move those back to the zones'
 * inactive list where they become candidates for reclaim.
 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
 * and we add swap to the system.  As such, it runs in the context of a task
 * that has possibly/probably made some previously unevictable pages
 * evictable.
 */
3025
static void scan_all_zones_unevictable_pages(void)
3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040
{
	struct zone *zone;

	for_each_zone(zone) {
		scan_zone_unevictable_pages(zone);
	}
}

/*
 * scan_unevictable_pages [vm] sysctl handler.  On demand re-scan of
 * all nodes' unevictable lists for evictable pages
 */
unsigned long scan_unevictable_pages;

int scan_unevictable_handler(struct ctl_table *table, int write,
3041
			   void __user *buffer,
3042 3043
			   size_t *length, loff_t *ppos)
{
3044
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3045 3046 3047 3048 3049 3050 3051 3052

	if (write && *(unsigned long *)table->data)
		scan_all_zones_unevictable_pages();

	scan_unevictable_pages = 0;
	return 0;
}

3053
#ifdef CONFIG_NUMA
3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099
/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

static ssize_t read_scan_unevictable_node(struct sys_device *dev,
					  struct sysdev_attribute *attr,
					  char *buf)
{
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

static ssize_t write_scan_unevictable_node(struct sys_device *dev,
					   struct sysdev_attribute *attr,
					const char *buf, size_t count)
{
	struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
	struct zone *zone;
	unsigned long res;
	unsigned long req = strict_strtoul(buf, 10, &res);

	if (!req)
		return 1;	/* zero is no-op */

	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
		if (!populated_zone(zone))
			continue;
		scan_zone_unevictable_pages(zone);
	}
	return 1;
}


static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
	return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
}

void scan_unevictable_unregister_node(struct node *node)
{
	sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
}
3100
#endif