vmscan.c 98.2 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>
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#include <linux/compaction.h>
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#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 <linux/oom.h>
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#include <linux/prefetch.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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/*
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 * reclaim_mode determines how the inactive list is shrunk
 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
 * RECLAIM_MODE_ASYNC:  Do not block
 * RECLAIM_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
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 *			page from the LRU and reclaim all pages within a
 *			naturally aligned range
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 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
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 *			order-0 pages and then compact the zone
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 */
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typedef unsigned __bitwise__ reclaim_mode_t;
#define RECLAIM_MODE_SINGLE		((__force reclaim_mode_t)0x01u)
#define RECLAIM_MODE_ASYNC		((__force reclaim_mode_t)0x02u)
#define RECLAIM_MODE_SYNC		((__force reclaim_mode_t)0x04u)
#define RECLAIM_MODE_LUMPYRECLAIM	((__force reclaim_mode_t)0x08u)
#define RECLAIM_MODE_COMPACTION		((__force reclaim_mode_t)0x10u)
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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 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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	reclaim_mode_t 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_lru_pages(sc->mem_cgroup,
				zone_to_nid(zone), zone_idx(zone), BIT(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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	atomic_long_set(&shrinker->nr_in_batch, 0);
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	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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static inline int do_shrinker_shrink(struct shrinker *shrinker,
				     struct shrink_control *sc,
				     unsigned long nr_to_scan)
{
	sc->nr_to_scan = nr_to_scan;
	return (*shrinker->shrink)(shrinker, sc);
}

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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(struct shrink_control *shrink,
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			  unsigned long nr_pages_scanned,
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			  unsigned long lru_pages)
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{
	struct shrinker *shrinker;
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	unsigned long ret = 0;
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	if (nr_pages_scanned == 0)
		nr_pages_scanned = SWAP_CLUSTER_MAX;
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	if (!down_read_trylock(&shrinker_rwsem)) {
		/* Assume we'll be able to shrink next time */
		ret = 1;
		goto out;
	}
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
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		long total_scan;
		long max_pass;
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		int shrink_ret = 0;
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		long nr;
		long new_nr;
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		long batch_size = shrinker->batch ? shrinker->batch
						  : SHRINK_BATCH;
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		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
		if (max_pass <= 0)
			continue;

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		/*
		 * copy the current shrinker scan count into a local variable
		 * and zero it so that other concurrent shrinker invocations
		 * don't also do this scanning work.
		 */
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		nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
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		total_scan = nr;
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		delta = (4 * nr_pages_scanned) / shrinker->seeks;
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		delta *= max_pass;
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		do_div(delta, lru_pages + 1);
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		total_scan += delta;
		if (total_scan < 0) {
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			printk(KERN_ERR "shrink_slab: %pF negative objects to "
			       "delete nr=%ld\n",
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			       shrinker->shrink, total_scan);
			total_scan = max_pass;
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		}

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		/*
		 * We need to avoid excessive windup on filesystem shrinkers
		 * due to large numbers of GFP_NOFS allocations causing the
		 * shrinkers to return -1 all the time. This results in a large
		 * nr being built up so when a shrink that can do some work
		 * comes along it empties the entire cache due to nr >>>
		 * max_pass.  This is bad for sustaining a working set in
		 * memory.
		 *
		 * Hence only allow the shrinker to scan the entire cache when
		 * a large delta change is calculated directly.
		 */
		if (delta < max_pass / 4)
			total_scan = min(total_scan, max_pass / 2);

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

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		while (total_scan >= batch_size) {
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			int nr_before;
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			nr_before = do_shrinker_shrink(shrinker, shrink, 0);
			shrink_ret = do_shrinker_shrink(shrinker, shrink,
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							batch_size);
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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, batch_size);
			total_scan -= batch_size;
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			cond_resched();
		}

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		/*
		 * move the unused scan count back into the shrinker in a
		 * manner that handles concurrent updates. If we exhausted the
		 * scan, there is no need to do an update.
		 */
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		if (total_scan > 0)
			new_nr = atomic_long_add_return(total_scan,
					&shrinker->nr_in_batch);
		else
			new_nr = atomic_long_read(&shrinker->nr_in_batch);
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		trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
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	}
	up_read(&shrinker_rwsem);
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out:
	cond_resched();
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	return ret;
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}

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static void set_reclaim_mode(int priority, struct scan_control *sc,
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				   bool sync)
{
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	reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
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	/*
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	 * Initially assume we are entering either lumpy reclaim or
	 * reclaim/compaction.Depending on the order, we will either set the
	 * sync mode or just reclaim order-0 pages later.
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	 */
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	if (COMPACTION_BUILD)
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		sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
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	else
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		sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
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	/*
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	 * Avoid using lumpy reclaim or reclaim/compaction if possible by
	 * restricting when its set to either costly allocations or when
	 * under memory pressure
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	 */
	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
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		sc->reclaim_mode |= syncmode;
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	else if (sc->order && priority < DEF_PRIORITY - 2)
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		sc->reclaim_mode |= syncmode;
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	else
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		sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
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}

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static void reset_reclaim_mode(struct scan_control *sc)
372
{
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	sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
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}

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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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{
389
	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(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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 */
439
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.
	 *
449
	 * 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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		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->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)
516
{
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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.
545
	 */
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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 {
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		void (*freepage)(struct page *);

		freepage = mapping->a_ops->freepage;

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		__delete_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		mem_cgroup_uncharge_cache_page(page);
567 568 569

		if (freepage != NULL)
			freepage(page);
570 571 572 573 574
	}

	return 1;

cannot_free:
N
Nick Piggin 已提交
575
	spin_unlock_irq(&mapping->tree_lock);
576 577 578
	return 0;
}

N
Nick Piggin 已提交
579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598
/*
 * 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;
}

L
Lee Schermerhorn 已提交
599 600 601 602 603 604 605 606 607 608 609 610 611
/**
 * 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);
612
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
613 614 615 616 617 618 619 620 621 622 623 624 625

	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.
		 */
626
		lru = active + page_lru_base_type(page);
L
Lee Schermerhorn 已提交
627 628 629 630 631 632 633 634
		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);
635
		/*
636 637 638 639 640
		 * When racing with an mlock or AS_UNEVICTABLE clearing
		 * (page is unlocked) make sure that if the other thread
		 * does not observe our setting of PG_lru and fails
		 * isolation/check_move_unevictable_page,
		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
641 642
		 * the page back to the evictable list.
		 *
643
		 * The other side is TestClearPageMlocked() or shmem_lock().
644 645
		 */
		smp_mb();
L
Lee Schermerhorn 已提交
646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663
	}

	/*
	 * 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.
		 */
	}

664 665 666 667 668
	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
669 670 671
	put_page(page);		/* drop ref from isolate */
}

672 673 674
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
675
	PAGEREF_KEEP,
676 677 678 679 680 681
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
682
	int referenced_ptes, referenced_page;
683 684
	unsigned long vm_flags;

685 686
	referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
	referenced_page = TestClearPageReferenced(page);
687 688

	/* Lumpy reclaim - ignore references */
689
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
690 691 692 693 694 695 696 697 698
		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;

699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717
	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);

718
		if (referenced_page || referenced_ptes > 1)
719 720
			return PAGEREF_ACTIVATE;

721 722 723 724 725 726
		/*
		 * Activate file-backed executable pages after first usage.
		 */
		if (vm_flags & VM_EXEC)
			return PAGEREF_ACTIVATE;

727 728
		return PAGEREF_KEEP;
	}
729 730

	/* Reclaim if clean, defer dirty pages to writeback */
731
	if (referenced_page && !PageSwapBacked(page))
732 733 734
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
735 736
}

L
Linus Torvalds 已提交
737
/*
A
Andrew Morton 已提交
738
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
739
 */
A
Andrew Morton 已提交
740
static unsigned long shrink_page_list(struct list_head *page_list,
741
				      struct zone *zone,
742
				      struct scan_control *sc,
743 744 745
				      int priority,
				      unsigned long *ret_nr_dirty,
				      unsigned long *ret_nr_writeback)
L
Linus Torvalds 已提交
746 747
{
	LIST_HEAD(ret_pages);
748
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
749
	int pgactivate = 0;
750 751
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
752
	unsigned long nr_reclaimed = 0;
753
	unsigned long nr_writeback = 0;
L
Linus Torvalds 已提交
754 755 756 757

	cond_resched();

	while (!list_empty(page_list)) {
758
		enum page_references references;
L
Linus Torvalds 已提交
759 760 761 762 763 764 765 766 767
		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
768
		if (!trylock_page(page))
L
Linus Torvalds 已提交
769 770
			goto keep;

N
Nick Piggin 已提交
771
		VM_BUG_ON(PageActive(page));
772
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
773 774

		sc->nr_scanned++;
775

N
Nick Piggin 已提交
776 777
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
778

779
		if (!sc->may_unmap && page_mapped(page))
780 781
			goto keep_locked;

L
Linus Torvalds 已提交
782 783 784 785
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

786 787 788 789
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
790
			nr_writeback++;
791
			/*
792 793 794 795
			 * Synchronous reclaim cannot queue pages for
			 * writeback due to the possibility of stack overflow
			 * but if it encounters a page under writeback, wait
			 * for the IO to complete.
796
			 */
797
			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
798
			    may_enter_fs)
799
				wait_on_page_writeback(page);
800 801 802 803
			else {
				unlock_page(page);
				goto keep_lumpy;
			}
804
		}
L
Linus Torvalds 已提交
805

806 807 808
		references = page_check_references(page, sc);
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
809
			goto activate_locked;
810 811
		case PAGEREF_KEEP:
			goto keep_locked;
812 813 814 815
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
816 817 818 819 820

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
821
		if (PageAnon(page) && !PageSwapCache(page)) {
822 823
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
824
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
825
				goto activate_locked;
826
			may_enter_fs = 1;
N
Nick Piggin 已提交
827
		}
L
Linus Torvalds 已提交
828 829 830 831 832 833 834 835

		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) {
836
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
837 838 839 840
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
841 842
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
843 844 845 846 847 848
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
849 850
			nr_dirty++;

851 852
			/*
			 * Only kswapd can writeback filesystem pages to
853 854
			 * avoid risk of stack overflow but do not writeback
			 * unless under significant pressure.
855
			 */
856 857
			if (page_is_file_cache(page) &&
					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
858 859 860 861 862 863 864 865 866
				/*
				 * Immediately reclaim when written back.
				 * Similar in principal to deactivate_page()
				 * except we already have the page isolated
				 * and know it's dirty
				 */
				inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
				SetPageReclaim(page);

867 868 869
				goto keep_locked;
			}

870
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
871
				goto keep_locked;
872
			if (!may_enter_fs)
L
Linus Torvalds 已提交
873
				goto keep_locked;
874
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
875 876 877
				goto keep_locked;

			/* Page is dirty, try to write it out here */
878
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
879
			case PAGE_KEEP:
880
				nr_congested++;
L
Linus Torvalds 已提交
881 882 883 884
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
885 886 887
				if (PageWriteback(page))
					goto keep_lumpy;
				if (PageDirty(page))
L
Linus Torvalds 已提交
888
					goto keep;
889

L
Linus Torvalds 已提交
890 891 892 893
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
894
				if (!trylock_page(page))
L
Linus Torvalds 已提交
895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913
					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
914
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
915 916 917 918 919 920 921 922 923 924
		 * 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.
		 */
925
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
926 927
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943
			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
944 945
		}

N
Nick Piggin 已提交
946
		if (!mapping || !__remove_mapping(mapping, page))
947
			goto keep_locked;
L
Linus Torvalds 已提交
948

N
Nick Piggin 已提交
949 950 951 952 953 954 955 956
		/*
		 * 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
957
free_it:
958
		nr_reclaimed++;
959 960 961 962 963 964

		/*
		 * 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
965 966
		continue;

N
Nick Piggin 已提交
967
cull_mlocked:
968 969
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
970 971
		unlock_page(page);
		putback_lru_page(page);
972
		reset_reclaim_mode(sc);
N
Nick Piggin 已提交
973 974
		continue;

L
Linus Torvalds 已提交
975
activate_locked:
976 977
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
978
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
979
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
980 981 982 983 984
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
985
		reset_reclaim_mode(sc);
986
keep_lumpy:
L
Linus Torvalds 已提交
987
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
988
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
989
	}
990

991 992 993 994 995 996
	/*
	 * 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
	 */
K
KAMEZAWA Hiroyuki 已提交
997
	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
998 999
		zone_set_flag(zone, ZONE_CONGESTED);

1000
	free_hot_cold_page_list(&free_pages, 1);
1001

L
Linus Torvalds 已提交
1002
	list_splice(&ret_pages, page_list);
1003
	count_vm_events(PGACTIVATE, pgactivate);
1004 1005
	*ret_nr_dirty += nr_dirty;
	*ret_nr_writeback += nr_writeback;
1006
	return nr_reclaimed;
L
Linus Torvalds 已提交
1007 1008
}

A
Andy Whitcroft 已提交
1009 1010 1011 1012 1013 1014 1015 1016 1017 1018
/*
 * 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.
 */
1019
int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
A
Andy Whitcroft 已提交
1020
{
1021
	bool all_lru_mode;
A
Andy Whitcroft 已提交
1022 1023 1024 1025 1026 1027
	int ret = -EINVAL;

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

1028 1029 1030
	all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);

A
Andy Whitcroft 已提交
1031 1032 1033 1034 1035
	/*
	 * When checking the active state, we need to be sure we are
	 * dealing with comparible boolean values.  Take the logical not
	 * of each.
	 */
1036
	if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
A
Andy Whitcroft 已提交
1037 1038
		return ret;

1039
	if (!all_lru_mode && !!page_is_file_cache(page) != file)
1040 1041
		return ret;

L
Lee Schermerhorn 已提交
1042 1043 1044 1045 1046 1047 1048 1049
	/*
	 * 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
1050
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
1051

1052 1053 1054
	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
		return ret;

1055 1056 1057
	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
		return ret;

A
Andy Whitcroft 已提交
1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070
	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
1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
/*
 * 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
1085 1086
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
1087
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
1088 1089 1090
 *
 * returns how many pages were moved onto *@dst.
 */
1091 1092
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
1093 1094
		unsigned long *scanned, int order, isolate_mode_t mode,
		int file)
L
Linus Torvalds 已提交
1095
{
1096
	unsigned long nr_taken = 0;
1097 1098 1099
	unsigned long nr_lumpy_taken = 0;
	unsigned long nr_lumpy_dirty = 0;
	unsigned long nr_lumpy_failed = 0;
1100
	unsigned long scan;
L
Linus Torvalds 已提交
1101

1102
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1103 1104 1105 1106 1107 1108
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
1109 1110 1111
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1112
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1113

1114
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
1115 1116
		case 0:
			list_move(&page->lru, dst);
1117
			mem_cgroup_del_lru(page);
1118
			nr_taken += hpage_nr_pages(page);
A
Andy Whitcroft 已提交
1119 1120 1121 1122 1123
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
1124
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
1125
			continue;
1126

A
Andy Whitcroft 已提交
1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138
		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
L
Lucas De Marchi 已提交
1139
		 * as the mem_map is guaranteed valid out to MAX_ORDER,
A
Andy Whitcroft 已提交
1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158
		 * 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);
1159

A
Andy Whitcroft 已提交
1160 1161
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
1162
				break;
1163 1164 1165 1166 1167 1168 1169

			/*
			 * 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) &&
1170 1171
			    !PageSwapCache(cursor_page))
				break;
1172

1173
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
1174
				list_move(&cursor_page->lru, dst);
1175
				mem_cgroup_del_lru(cursor_page);
1176
				nr_taken += hpage_nr_pages(page);
1177 1178 1179
				nr_lumpy_taken++;
				if (PageDirty(cursor_page))
					nr_lumpy_dirty++;
A
Andy Whitcroft 已提交
1180
				scan++;
1181
			} else {
1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195
				/*
				 * Check if the page is freed already.
				 *
				 * We can't use page_count() as that
				 * requires compound_head and we don't
				 * have a pin on the page here. If a
				 * page is tail, we may or may not
				 * have isolated the head, so assume
				 * it's not free, it'd be tricky to
				 * track the head status without a
				 * page pin.
				 */
				if (!PageTail(cursor_page) &&
				    !atomic_read(&cursor_page->_count))
1196 1197
					continue;
				break;
A
Andy Whitcroft 已提交
1198 1199
			}
		}
1200 1201 1202 1203

		/* If we break out of the loop above, lumpy reclaim failed */
		if (pfn < end_pfn)
			nr_lumpy_failed++;
L
Linus Torvalds 已提交
1204 1205 1206
	}

	*scanned = scan;
1207 1208 1209 1210 1211 1212

	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
1213 1214 1215
	return nr_taken;
}

1216 1217 1218
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
1219 1220
					isolate_mode_t mode,
					struct zone *z,	int active, int file)
1221
{
1222
	int lru = LRU_BASE;
1223
	if (active)
1224 1225 1226 1227
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1228
								mode, file);
1229 1230
}

A
Andy Whitcroft 已提交
1231 1232 1233 1234
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
1235 1236
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
1237 1238
{
	int nr_active = 0;
1239
	int lru;
A
Andy Whitcroft 已提交
1240 1241
	struct page *page;

1242
	list_for_each_entry(page, page_list, lru) {
1243
		int numpages = hpage_nr_pages(page);
1244
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
1245
		if (PageActive(page)) {
1246
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
1247
			ClearPageActive(page);
1248
			nr_active += numpages;
A
Andy Whitcroft 已提交
1249
		}
1250
		if (count)
1251
			count[lru] += numpages;
1252
	}
A
Andy Whitcroft 已提交
1253 1254 1255 1256

	return nr_active;
}

1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267
/**
 * 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
1268 1269 1270
 * 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.
1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285
 *
 * 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;

1286 1287
	VM_BUG_ON(!page_count(page));

1288 1289 1290 1291
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
1292
		if (PageLRU(page)) {
L
Lee Schermerhorn 已提交
1293
			int lru = page_lru(page);
1294
			ret = 0;
1295
			get_page(page);
1296
			ClearPageLRU(page);
1297 1298

			del_page_from_lru_list(zone, page, lru);
1299 1300 1301 1302 1303 1304
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
/*
 * 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;
}

1330 1331 1332 1333
/*
 * TODO: Try merging with migrations version of putback_lru_pages
 */
static noinline_for_stack void
1334
putback_lru_pages(struct zone *zone, struct scan_control *sc,
1335 1336 1337 1338 1339
				unsigned long nr_anon, unsigned long nr_file,
				struct list_head *page_list)
{
	struct page *page;
	struct pagevec pvec;
1340
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358

	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;
		}
1359
		SetPageLRU(page);
1360
		lru = page_lru(page);
1361
		add_page_to_lru_list(zone, page, lru);
1362 1363
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1364 1365
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379
		}
		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);
}

1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410
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;
}

1411
/*
1412
 * Returns true if a direct reclaim should wait on pages under writeback.
1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
 *
 * 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 */
1431
	if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1432 1433
		return false;

1434
	/* If we have reclaimed everything on the isolated list, no stall */
1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451
	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
1452
/*
A
Andrew Morton 已提交
1453 1454
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1455
 */
1456 1457 1458
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
1459 1460
{
	LIST_HEAD(page_list);
1461
	unsigned long nr_scanned;
1462
	unsigned long nr_reclaimed = 0;
1463 1464 1465
	unsigned long nr_taken;
	unsigned long nr_anon;
	unsigned long nr_file;
1466 1467
	unsigned long nr_dirty = 0;
	unsigned long nr_writeback = 0;
1468
	isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1469

1470
	while (unlikely(too_many_isolated(zone, file, sc))) {
1471
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1472 1473 1474 1475 1476 1477

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

1478
	set_reclaim_mode(priority, sc, false);
1479 1480 1481
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
		reclaim_mode |= ISOLATE_ACTIVE;

L
Linus Torvalds 已提交
1482
	lru_add_drain();
1483 1484 1485 1486 1487 1488

	if (!sc->may_unmap)
		reclaim_mode |= ISOLATE_UNMAPPED;
	if (!sc->may_writepage)
		reclaim_mode |= ISOLATE_CLEAN;

L
Linus Torvalds 已提交
1489
	spin_lock_irq(&zone->lru_lock);
1490

1491
	if (scanning_global_lru(sc)) {
1492 1493
		nr_taken = isolate_pages_global(nr_to_scan, &page_list,
			&nr_scanned, sc->order, reclaim_mode, zone, 0, file);
1494 1495 1496 1497 1498 1499 1500 1501
		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 {
1502 1503 1504
		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
			&nr_scanned, sc->order, reclaim_mode, zone,
			sc->mem_cgroup, 0, file);
1505 1506 1507 1508 1509
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
	}
1510

1511 1512 1513 1514
	if (nr_taken == 0) {
		spin_unlock_irq(&zone->lru_lock);
		return 0;
	}
A
Andy Whitcroft 已提交
1515

1516
	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
L
Linus Torvalds 已提交
1517

1518
	spin_unlock_irq(&zone->lru_lock);
1519

1520 1521
	nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority,
						&nr_dirty, &nr_writeback);
1522

1523 1524
	/* Check if we should syncronously wait for writeback */
	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1525
		set_reclaim_mode(priority, sc, true);
1526 1527
		nr_reclaimed += shrink_page_list(&page_list, zone, sc,
					priority, &nr_dirty, &nr_writeback);
1528
	}
1529

1530 1531 1532 1533
	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
1534

1535
	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1536

1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562
	/*
	 * If reclaim is isolating dirty pages under writeback, it implies
	 * that the long-lived page allocation rate is exceeding the page
	 * laundering rate. Either the global limits are not being effective
	 * at throttling processes due to the page distribution throughout
	 * zones or there is heavy usage of a slow backing device. The
	 * only option is to throttle from reclaim context which is not ideal
	 * as there is no guarantee the dirtying process is throttled in the
	 * same way balance_dirty_pages() manages.
	 *
	 * This scales the number of dirty pages that must be under writeback
	 * before throttling depending on priority. It is a simple backoff
	 * function that has the most effect in the range DEF_PRIORITY to
	 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
	 * in trouble and reclaim is considered to be in trouble.
	 *
	 * DEF_PRIORITY   100% isolated pages must be PageWriteback to throttle
	 * DEF_PRIORITY-1  50% must be PageWriteback
	 * DEF_PRIORITY-2  25% must be PageWriteback, kswapd in trouble
	 * ...
	 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
	 *                     isolated page is PageWriteback
	 */
	if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
		wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);

1563 1564 1565 1566
	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
		priority,
1567
		trace_shrink_flags(file, sc->reclaim_mode));
1568
	return nr_reclaimed;
L
Linus Torvalds 已提交
1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587
}

/*
 * 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.
 */
1588

1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606
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);
1607
		pgmoved += hpage_nr_pages(page);
1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620

		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);
}
1621

A
Andrew Morton 已提交
1622
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1623
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1624
{
1625
	unsigned long nr_taken;
1626
	unsigned long pgscanned;
1627
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1628
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1629
	LIST_HEAD(l_active);
1630
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1631
	struct page *page;
1632
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1633
	unsigned long nr_rotated = 0;
1634
	isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
L
Linus Torvalds 已提交
1635 1636

	lru_add_drain();
1637 1638 1639 1640 1641 1642

	if (!sc->may_unmap)
		reclaim_mode |= ISOLATE_UNMAPPED;
	if (!sc->may_writepage)
		reclaim_mode |= ISOLATE_CLEAN;

L
Linus Torvalds 已提交
1643
	spin_lock_irq(&zone->lru_lock);
1644
	if (scanning_global_lru(sc)) {
1645 1646
		nr_taken = isolate_pages_global(nr_pages, &l_hold,
						&pgscanned, sc->order,
1647
						reclaim_mode, zone,
1648
						1, file);
1649
		zone->pages_scanned += pgscanned;
1650 1651 1652
	} else {
		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
						&pgscanned, sc->order,
1653
						reclaim_mode, zone,
1654 1655 1656 1657 1658
						sc->mem_cgroup, 1, file);
		/*
		 * mem_cgroup_isolate_pages() keeps track of
		 * scanned pages on its own.
		 */
1659
	}
1660

1661
	reclaim_stat->recent_scanned[file] += nr_taken;
1662

1663
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1664
	if (file)
1665
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1666
	else
1667
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1668
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1669 1670 1671 1672 1673 1674
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1675

L
Lee Schermerhorn 已提交
1676 1677 1678 1679 1680
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1681
		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1682
			nr_rotated += hpage_nr_pages(page);
1683 1684 1685 1686 1687 1688 1689 1690 1691
			/*
			 * 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.
			 */
1692
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1693 1694 1695 1696
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1697

1698
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1699 1700 1701
		list_add(&page->lru, &l_inactive);
	}

1702
	/*
1703
	 * Move pages back to the lru list.
1704
	 */
1705
	spin_lock_irq(&zone->lru_lock);
1706
	/*
1707 1708 1709 1710
	 * 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.
1711
	 */
1712
	reclaim_stat->recent_rotated[file] += nr_rotated;
1713

1714 1715 1716 1717
	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
1718
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1719
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1720 1721
}

1722
#ifdef CONFIG_SWAP
1723
static int inactive_anon_is_low_global(struct zone *zone)
1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735
{
	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;
}

1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
/**
 * 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;

1748 1749 1750 1751 1752 1753 1754
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1755
	if (scanning_global_lru(sc))
1756 1757
		low = inactive_anon_is_low_global(zone);
	else
1758
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup, zone);
1759 1760
	return low;
}
1761 1762 1763 1764 1765 1766 1767
#else
static inline int inactive_anon_is_low(struct zone *zone,
					struct scan_control *sc)
{
	return 0;
}
#endif
1768

1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800
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
1801
		low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup, zone);
1802 1803 1804
	return low;
}

1805 1806 1807 1808 1809 1810 1811 1812 1813
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);
}

1814
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1815 1816
	struct zone *zone, struct scan_control *sc, int priority)
{
1817 1818
	int file = is_file_lru(lru);

1819 1820 1821
	if (is_active_lru(lru)) {
		if (inactive_list_is_low(zone, sc, file))
		    shrink_active_list(nr_to_scan, zone, sc, priority, file);
1822 1823 1824
		return 0;
	}

R
Rik van Riel 已提交
1825
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1826 1827
}

1828 1829 1830 1831 1832 1833 1834
static int vmscan_swappiness(struct scan_control *sc)
{
	if (scanning_global_lru(sc))
		return vm_swappiness;
	return mem_cgroup_swappiness(sc->mem_cgroup);
}

1835 1836 1837 1838 1839 1840
/*
 * 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.
 *
1841
 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1842
 */
1843 1844
static void get_scan_count(struct zone *zone, struct scan_control *sc,
					unsigned long *nr, int priority)
1845 1846 1847 1848
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1849
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1850 1851 1852
	u64 fraction[2], denominator;
	enum lru_list l;
	int noswap = 0;
1853
	bool force_scan = false;
1854

1855 1856 1857 1858 1859 1860 1861 1862 1863 1864
	/*
	 * If the zone or memcg is small, nr[l] can be 0.  This
	 * results in no scanning on this priority and a potential
	 * priority drop.  Global direct reclaim can go to the next
	 * zone and tends to have no problems. Global kswapd is for
	 * zone balancing and it needs to scan a minimum amount. When
	 * reclaiming for a memcg, a priority drop can cause high
	 * latencies, so it's better to scan a minimum amount there as
	 * well.
	 */
1865 1866 1867 1868
	if (scanning_global_lru(sc) && current_is_kswapd())
		force_scan = true;
	if (!scanning_global_lru(sc))
		force_scan = true;
1869 1870 1871 1872 1873 1874 1875 1876 1877

	/* 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;
	}
1878

1879 1880 1881 1882 1883
	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);

1884
	if (scanning_global_lru(sc)) {
1885 1886 1887
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1888
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1889 1890 1891 1892
			fraction[0] = 1;
			fraction[1] = 0;
			denominator = 1;
			goto out;
1893
		}
1894 1895
	}

1896 1897 1898 1899
	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
1900 1901
	anon_prio = vmscan_swappiness(sc);
	file_prio = 200 - vmscan_swappiness(sc);
1902

1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913
	/*
	 * 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]
	 */
1914
	spin_lock_irq(&zone->lru_lock);
1915 1916 1917
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1918 1919
	}

1920 1921 1922
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1923 1924 1925
	}

	/*
1926 1927 1928
	 * 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.
1929
	 */
1930 1931
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1932

1933 1934
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1935
	spin_unlock_irq(&zone->lru_lock);
1936

1937 1938 1939 1940 1941 1942 1943
	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;
1944

1945 1946 1947
		scan = zone_nr_lru_pages(zone, sc, l);
		if (priority || noswap) {
			scan >>= priority;
1948 1949
			if (!scan && force_scan)
				scan = SWAP_CLUSTER_MAX;
1950 1951
			scan = div64_u64(scan * fraction[file], denominator);
		}
1952
		nr[l] = scan;
1953
	}
1954
}
1955

1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
/*
 * Reclaim/compaction depends on a number of pages being freed. To avoid
 * disruption to the system, a small number of order-0 pages continue to be
 * rotated and reclaimed in the normal fashion. However, by the time we get
 * back to the allocator and call try_to_compact_zone(), we ensure that
 * there are enough free pages for it to be likely successful
 */
static inline bool should_continue_reclaim(struct zone *zone,
					unsigned long nr_reclaimed,
					unsigned long nr_scanned,
					struct scan_control *sc)
{
	unsigned long pages_for_compaction;
	unsigned long inactive_lru_pages;

	/* If not in reclaim/compaction mode, stop */
1972
	if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1973 1974
		return false;

1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996
	/* Consider stopping depending on scan and reclaim activity */
	if (sc->gfp_mask & __GFP_REPEAT) {
		/*
		 * For __GFP_REPEAT allocations, stop reclaiming if the
		 * full LRU list has been scanned and we are still failing
		 * to reclaim pages. This full LRU scan is potentially
		 * expensive but a __GFP_REPEAT caller really wants to succeed
		 */
		if (!nr_reclaimed && !nr_scanned)
			return false;
	} else {
		/*
		 * For non-__GFP_REPEAT allocations which can presumably
		 * fail without consequence, stop if we failed to reclaim
		 * any pages from the last SWAP_CLUSTER_MAX number of
		 * pages that were scanned. This will return to the
		 * caller faster at the risk reclaim/compaction and
		 * the resulting allocation attempt fails
		 */
		if (!nr_reclaimed)
			return false;
	}
1997 1998 1999 2000 2001 2002

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = (2UL << sc->order);
2003 2004 2005
	inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
	if (nr_swap_pages > 0)
		inactive_lru_pages += zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
	if (sc->nr_reclaimed < pages_for_compaction &&
			inactive_lru_pages > pages_for_compaction)
		return true;

	/* If compaction would go ahead or the allocation would succeed, stop */
	switch (compaction_suitable(zone, sc->order)) {
	case COMPACT_PARTIAL:
	case COMPACT_CONTINUE:
		return false;
	default:
		return true;
	}
}

L
Linus Torvalds 已提交
2020 2021 2022
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
2023
static void shrink_zone(int priority, struct zone *zone,
2024
				struct scan_control *sc)
L
Linus Torvalds 已提交
2025
{
2026
	unsigned long nr[NR_LRU_LISTS];
2027
	unsigned long nr_to_scan;
2028
	enum lru_list l;
2029
	unsigned long nr_reclaimed, nr_scanned;
2030
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2031
	struct blk_plug plug;
2032

2033 2034
restart:
	nr_reclaimed = 0;
2035
	nr_scanned = sc->nr_scanned;
2036
	get_scan_count(zone, sc, nr, priority);
L
Linus Torvalds 已提交
2037

2038
	blk_start_plug(&plug);
2039 2040
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
2041
		for_each_evictable_lru(l) {
2042
			if (nr[l]) {
K
KOSAKI Motohiro 已提交
2043 2044
				nr_to_scan = min_t(unsigned long,
						   nr[l], SWAP_CLUSTER_MAX);
2045
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
2046

2047 2048
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
2049
			}
L
Linus Torvalds 已提交
2050
		}
2051 2052 2053 2054 2055 2056 2057 2058
		/*
		 * 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.
		 */
2059
		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2060
			break;
L
Linus Torvalds 已提交
2061
	}
2062
	blk_finish_plug(&plug);
2063
	sc->nr_reclaimed += nr_reclaimed;
2064

2065 2066 2067 2068
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
2069
	if (inactive_anon_is_low(zone, sc))
2070 2071
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

2072 2073 2074 2075 2076
	/* reclaim/compaction might need reclaim to continue */
	if (should_continue_reclaim(zone, nr_reclaimed,
					sc->nr_scanned - nr_scanned, sc))
		goto restart;

2077
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
2078 2079 2080 2081 2082 2083 2084
}

/*
 * 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.
 *
2085 2086
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
2087 2088
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
2089 2090 2091
 * 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
2092 2093 2094
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
2095 2096 2097 2098
 *
 * This function returns true if a zone is being reclaimed for a costly
 * high-order allocation and compaction is either ready to begin or deferred.
 * This indicates to the caller that it should retry the allocation or fail.
L
Linus Torvalds 已提交
2099
 */
2100
static bool shrink_zones(int priority, struct zonelist *zonelist,
2101
					struct scan_control *sc)
L
Linus Torvalds 已提交
2102
{
2103
	struct zoneref *z;
2104
	struct zone *zone;
2105 2106
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2107
	bool should_abort_reclaim = false;
2108

2109 2110
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
2111
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
2112
			continue;
2113 2114 2115 2116
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
2117
		if (scanning_global_lru(sc)) {
2118 2119
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
2120
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2121
				continue;	/* Let kswapd poll it */
2122 2123
			if (COMPACTION_BUILD) {
				/*
2124 2125 2126 2127 2128 2129 2130
				 * If we already have plenty of memory free for
				 * compaction in this zone, don't free any more.
				 * Even though compaction is invoked for any
				 * non-zero order, only frequent costly order
				 * reclamation is disruptive enough to become a
				 * noticable problem, like transparent huge page
				 * allocations.
2131 2132 2133
				 */
				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
					(compaction_suitable(zone, sc->order) ||
2134 2135
					 compaction_deferred(zone))) {
					should_abort_reclaim = true;
2136
					continue;
2137
				}
2138
			}
2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151
			/*
			 * This steals pages from memory cgroups over softlimit
			 * and returns the number of reclaimed pages and
			 * scanned pages. This works for global memory pressure
			 * and balancing, not for a memcg's limit.
			 */
			nr_soft_scanned = 0;
			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
						sc->order, sc->gfp_mask,
						&nr_soft_scanned);
			sc->nr_reclaimed += nr_soft_reclaimed;
			sc->nr_scanned += nr_soft_scanned;
			/* need some check for avoid more shrink_zone() */
2152
		}
2153

2154
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
2155
	}
2156 2157

	return should_abort_reclaim;
2158 2159 2160 2161 2162 2163 2164
}

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

2165
/* All zones in zonelist are unreclaimable? */
2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177
static bool all_unreclaimable(struct zonelist *zonelist,
		struct scan_control *sc)
{
	struct zoneref *z;
	struct zone *zone;

	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;
2178 2179
		if (!zone->all_unreclaimable)
			return false;
2180 2181
	}

2182
	return true;
L
Linus Torvalds 已提交
2183
}
2184

L
Linus Torvalds 已提交
2185 2186 2187 2188 2189 2190 2191 2192
/*
 * 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
2193 2194 2195 2196
 * 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.
2197 2198 2199
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2200
 */
2201
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2202 2203
					struct scan_control *sc,
					struct shrink_control *shrink)
L
Linus Torvalds 已提交
2204 2205
{
	int priority;
2206
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2207
	struct reclaim_state *reclaim_state = current->reclaim_state;
2208
	struct zoneref *z;
2209
	struct zone *zone;
2210
	unsigned long writeback_threshold;
L
Linus Torvalds 已提交
2211

2212
	get_mems_allowed();
2213 2214
	delayacct_freepages_start();

2215
	if (scanning_global_lru(sc))
2216
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2217 2218

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2219
		sc->nr_scanned = 0;
2220
		if (!priority)
2221
			disable_swap_token(sc->mem_cgroup);
2222 2223 2224
		if (shrink_zones(priority, zonelist, sc))
			break;

2225 2226 2227 2228
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
2229
		if (scanning_global_lru(sc)) {
2230
			unsigned long lru_pages = 0;
2231 2232
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2233 2234 2235 2236 2237 2238
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
			}

2239
			shrink_slab(shrink, sc->nr_scanned, lru_pages);
2240
			if (reclaim_state) {
2241
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2242 2243
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2244
		}
2245
		total_scanned += sc->nr_scanned;
2246
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2247 2248 2249 2250 2251 2252 2253 2254 2255
			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.
		 */
2256 2257
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2258 2259
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
						WB_REASON_TRY_TO_FREE_PAGES);
2260
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2261 2262 2263
		}

		/* Take a nap, wait for some writeback to complete */
2264
		if (!sc->hibernation_mode && sc->nr_scanned &&
2265 2266 2267 2268
		    priority < DEF_PRIORITY - 2) {
			struct zone *preferred_zone;

			first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2269 2270
						&cpuset_current_mems_allowed,
						&preferred_zone);
2271 2272
			wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
		}
L
Linus Torvalds 已提交
2273
	}
2274

L
Linus Torvalds 已提交
2275
out:
2276
	delayacct_freepages_end();
2277
	put_mems_allowed();
2278

2279 2280 2281
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

2282 2283 2284 2285 2286 2287 2288 2289
	/*
	 * As hibernation is going on, kswapd is freezed so that it can't mark
	 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
	 * check.
	 */
	if (oom_killer_disabled)
		return 0;

2290
	/* top priority shrink_zones still had more to do? don't OOM, then */
2291
	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2292 2293 2294
		return 1;

	return 0;
L
Linus Torvalds 已提交
2295 2296
}

2297
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2298
				gfp_t gfp_mask, nodemask_t *nodemask)
2299
{
2300
	unsigned long nr_reclaimed;
2301 2302 2303
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
2304
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2305
		.may_unmap = 1,
2306
		.may_swap = 1,
2307 2308
		.order = order,
		.mem_cgroup = NULL,
2309
		.nodemask = nodemask,
2310
	};
2311 2312 2313
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
2314

2315 2316 2317 2318
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

2319
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2320 2321 2322 2323

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2324 2325
}

2326
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2327

2328 2329
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
2330 2331
						struct zone *zone,
						unsigned long *nr_scanned)
2332 2333
{
	struct scan_control sc = {
2334
		.nr_scanned = 0,
2335
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2336 2337 2338 2339 2340 2341
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.order = 0,
		.mem_cgroup = mem,
	};
2342

2343 2344
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2345 2346 2347 2348 2349

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

2350 2351 2352 2353 2354 2355 2356 2357
	/*
	 * 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);
2358 2359 2360

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2361
	*nr_scanned = sc.nr_scanned;
2362 2363 2364
	return sc.nr_reclaimed;
}

2365
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
2366
					   gfp_t gfp_mask,
2367
					   bool noswap)
2368
{
2369
	struct zonelist *zonelist;
2370
	unsigned long nr_reclaimed;
2371
	int nid;
2372 2373
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2374
		.may_unmap = 1,
2375
		.may_swap = !noswap,
2376
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2377 2378
		.order = 0,
		.mem_cgroup = mem_cont,
2379
		.nodemask = NULL, /* we don't care the placement */
2380 2381 2382 2383 2384
		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
	};
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
2385 2386
	};

2387 2388 2389 2390 2391 2392 2393 2394
	/*
	 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
	 * take care of from where we get pages. So the node where we start the
	 * scan does not need to be the current node.
	 */
	nid = mem_cgroup_select_victim_node(mem_cont);

	zonelist = NODE_DATA(nid)->node_zonelists;
2395 2396 2397 2398 2399

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

2400
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2401 2402 2403 2404

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2405 2406 2407
}
#endif

2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418
/*
 * pgdat_balanced is used when checking if a node is balanced for high-order
 * allocations. Only zones that meet watermarks and are in a zone allowed
 * by the callers classzone_idx are added to balanced_pages. The total of
 * balanced pages must be at least 25% of the zones allowed by classzone_idx
 * for the node to be considered balanced. Forcing all zones to be balanced
 * for high orders can cause excessive reclaim when there are imbalanced zones.
 * The choice of 25% is due to
 *   o a 16M DMA zone that is balanced will not balance a zone on any
 *     reasonable sized machine
 *   o On all other machines, the top zone must be at least a reasonable
L
Lucas De Marchi 已提交
2419
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432
 *     would need to be at least 256M for it to be balance a whole node.
 *     Similarly, on x86-64 the Normal zone would need to be at least 1G
 *     to balance a node on its own. These seemed like reasonable ratios.
 */
static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
						int classzone_idx)
{
	unsigned long present_pages = 0;
	int i;

	for (i = 0; i <= classzone_idx; i++)
		present_pages += pgdat->node_zones[i].present_pages;

S
Shaohua Li 已提交
2433 2434
	/* A special case here: if zone has no page, we think it's balanced */
	return balanced_pages >= (present_pages >> 2);
2435 2436
}

2437
/* is kswapd sleeping prematurely? */
2438 2439
static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
					int classzone_idx)
2440
{
2441
	int i;
2442 2443
	unsigned long balanced = 0;
	bool all_zones_ok = true;
2444 2445 2446

	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2447
		return true;
2448

2449
	/* Check the watermark levels */
2450
	for (i = 0; i <= classzone_idx; i++) {
2451 2452 2453 2454 2455
		struct zone *zone = pgdat->node_zones + i;

		if (!populated_zone(zone))
			continue;

2456 2457 2458 2459 2460 2461 2462 2463
		/*
		 * balance_pgdat() skips over all_unreclaimable after
		 * DEF_PRIORITY. Effectively, it considers them balanced so
		 * they must be considered balanced here as well if kswapd
		 * is to sleep
		 */
		if (zone->all_unreclaimable) {
			balanced += zone->present_pages;
2464
			continue;
2465
		}
2466

2467
		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2468
							i, 0))
2469 2470 2471
			all_zones_ok = false;
		else
			balanced += zone->present_pages;
2472
	}
2473

2474 2475 2476 2477 2478 2479
	/*
	 * For high-order requests, the balanced zones must contain at least
	 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
	 * must be balanced
	 */
	if (order)
2480
		return !pgdat_balanced(pgdat, balanced, classzone_idx);
2481 2482
	else
		return !all_zones_ok;
2483 2484
}

L
Linus Torvalds 已提交
2485 2486
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2487
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2488
 *
2489
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2490 2491 2492 2493 2494 2495 2496 2497 2498 2499
 *
 * 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
2500 2501 2502 2503 2504
 * 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
2505
 */
2506
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2507
							int *classzone_idx)
L
Linus Torvalds 已提交
2508 2509
{
	int all_zones_ok;
2510
	unsigned long balanced;
L
Linus Torvalds 已提交
2511 2512
	int priority;
	int i;
2513
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2514
	unsigned long total_scanned;
L
Linus Torvalds 已提交
2515
	struct reclaim_state *reclaim_state = current->reclaim_state;
2516 2517
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2518 2519
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2520
		.may_unmap = 1,
2521
		.may_swap = 1,
2522 2523 2524 2525 2526
		/*
		 * 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,
A
Andy Whitcroft 已提交
2527
		.order = order,
2528
		.mem_cgroup = NULL,
2529
	};
2530 2531 2532
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
L
Linus Torvalds 已提交
2533 2534
loop_again:
	total_scanned = 0;
2535
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
2536
	sc.may_writepage = !laptop_mode;
2537
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2538 2539 2540

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
		unsigned long lru_pages = 0;
2541
		int has_under_min_watermark_zone = 0;
L
Linus Torvalds 已提交
2542

2543 2544
		/* The swap token gets in the way of swapout... */
		if (!priority)
2545
			disable_swap_token(NULL);
2546

L
Linus Torvalds 已提交
2547
		all_zones_ok = 1;
2548
		balanced = 0;
L
Linus Torvalds 已提交
2549

2550 2551 2552 2553 2554 2555
		/*
		 * 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
2556

2557 2558
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2559

2560
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2561
				continue;
L
Linus Torvalds 已提交
2562

2563 2564 2565 2566
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2567
			if (inactive_anon_is_low(zone, &sc))
2568 2569 2570
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

2571
			if (!zone_watermark_ok_safe(zone, order,
2572
					high_wmark_pages(zone), 0, 0)) {
2573
				end_zone = i;
A
Andrew Morton 已提交
2574
				break;
2575 2576 2577
			} else {
				/* If balanced, clear the congested flag */
				zone_clear_flag(zone, ZONE_CONGESTED);
L
Linus Torvalds 已提交
2578 2579
			}
		}
A
Andrew Morton 已提交
2580 2581 2582
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
2583 2584 2585
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2586
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599
		}

		/*
		 * 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;
2600
			int nr_slab;
2601
			unsigned long balance_gap;
L
Linus Torvalds 已提交
2602

2603
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2604 2605
				continue;

2606
			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2607 2608 2609
				continue;

			sc.nr_scanned = 0;
2610

2611
			nr_soft_scanned = 0;
2612 2613 2614
			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 */
2615 2616 2617 2618 2619
			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
							order, sc.gfp_mask,
							&nr_soft_scanned);
			sc.nr_reclaimed += nr_soft_reclaimed;
			total_scanned += nr_soft_scanned;
2620

2621
			/*
2622 2623 2624 2625 2626 2627
			 * We put equal pressure on every zone, unless
			 * one zone has way too many pages free
			 * already. The "too many pages" is defined
			 * as the high wmark plus a "gap" where the
			 * gap is either the low watermark or 1%
			 * of the zone, whichever is smaller.
2628
			 */
2629 2630 2631 2632
			balance_gap = min(low_wmark_pages(zone),
				(zone->present_pages +
					KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
				KSWAPD_ZONE_BALANCE_GAP_RATIO);
2633
			if (!zone_watermark_ok_safe(zone, order,
2634
					high_wmark_pages(zone) + balance_gap,
2635
					end_zone, 0)) {
2636
				shrink_zone(priority, zone, &sc);
2637

2638 2639 2640 2641 2642 2643 2644 2645 2646
				reclaim_state->reclaimed_slab = 0;
				nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
				sc.nr_reclaimed += reclaim_state->reclaimed_slab;
				total_scanned += sc.nr_scanned;

				if (nr_slab == 0 && !zone_reclaimable(zone))
					zone->all_unreclaimable = 1;
			}

L
Linus Torvalds 已提交
2647 2648 2649 2650 2651 2652
			/*
			 * 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 &&
2653
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2654
				sc.may_writepage = 1;
2655

2656 2657 2658
			if (zone->all_unreclaimable) {
				if (end_zone && end_zone == i)
					end_zone--;
2659
				continue;
2660
			}
2661

2662
			if (!zone_watermark_ok_safe(zone, order,
2663 2664 2665 2666 2667 2668 2669
					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!
				 */
2670
				if (!zone_watermark_ok_safe(zone, order,
2671 2672
					    min_wmark_pages(zone), end_zone, 0))
					has_under_min_watermark_zone = 1;
2673 2674 2675 2676 2677 2678 2679 2680 2681
			} 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);
2682
				if (i <= *classzone_idx)
2683
					balanced += zone->present_pages;
2684
			}
2685

L
Linus Torvalds 已提交
2686
		}
2687
		if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
L
Linus Torvalds 已提交
2688 2689 2690 2691 2692
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
2693 2694 2695 2696 2697 2698
		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
Linus Torvalds 已提交
2699 2700 2701 2702 2703 2704 2705

		/*
		 * 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.
		 */
2706
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2707 2708 2709
			break;
	}
out:
2710 2711 2712

	/*
	 * order-0: All zones must meet high watermark for a balanced node
2713 2714
	 * high-order: Balanced zones must make up at least 25% of the node
	 *             for the node to be balanced
2715
	 */
2716
	if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
L
Linus Torvalds 已提交
2717
		cond_resched();
2718 2719 2720

		try_to_freeze();

2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737
		/*
		 * 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
2738 2739 2740
		goto loop_again;
	}

2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767
	/*
	 * If kswapd was reclaiming at a higher order, it has the option of
	 * sleeping without all zones being balanced. Before it does, it must
	 * ensure that the watermarks for order-0 on *all* zones are met and
	 * that the congestion flags are cleared. The congestion flag must
	 * be cleared as kswapd is the only mechanism that clears the flag
	 * and it is potentially going to sleep here.
	 */
	if (order) {
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

			if (!populated_zone(zone))
				continue;

			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
				continue;

			/* Confirm the zone is balanced for order-0 */
			if (!zone_watermark_ok(zone, 0,
					high_wmark_pages(zone), 0, 0)) {
				order = sc.order = 0;
				goto loop_again;
			}

			/* If balanced, clear the congested flag */
			zone_clear_flag(zone, ZONE_CONGESTED);
2768 2769
			if (i <= *classzone_idx)
				balanced += zone->present_pages;
2770 2771 2772
		}
	}

2773 2774 2775 2776 2777 2778
	/*
	 * Return the order we were reclaiming at so sleeping_prematurely()
	 * makes a decision on the order we were last reclaiming at. However,
	 * if another caller entered the allocator slow path while kswapd
	 * was awake, order will remain at the higher level
	 */
2779
	*classzone_idx = end_zone;
2780
	return order;
L
Linus Torvalds 已提交
2781 2782
}

2783
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2784 2785 2786 2787 2788 2789 2790 2791 2792 2793
{
	long remaining = 0;
	DEFINE_WAIT(wait);

	if (freezing(current) || kthread_should_stop())
		return;

	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

	/* Try to sleep for a short interval */
2794
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2795 2796 2797 2798 2799 2800 2801 2802 2803
		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.
	 */
2804
	if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826
		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);

		/*
		 * vmstat counters are not perfectly accurate and the estimated
		 * value for counters such as NR_FREE_PAGES can deviate from the
		 * true value by nr_online_cpus * threshold. To avoid the zone
		 * watermarks being breached while under pressure, we reduce the
		 * per-cpu vmstat threshold while kswapd is awake and restore
		 * them before going back to sleep.
		 */
		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
		schedule();
		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
	} else {
		if (remaining)
			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
		else
			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
	}
	finish_wait(&pgdat->kswapd_wait, &wait);
}

L
Linus Torvalds 已提交
2827 2828
/*
 * The background pageout daemon, started as a kernel thread
2829
 * from the init process.
L
Linus Torvalds 已提交
2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841
 *
 * 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)
{
2842
	unsigned long order, new_order;
2843
	unsigned balanced_order;
2844
	int classzone_idx, new_classzone_idx;
2845
	int balanced_classzone_idx;
L
Linus Torvalds 已提交
2846 2847
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
2848

L
Linus Torvalds 已提交
2849 2850 2851
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
2852
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2853

2854 2855
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2856
	if (!cpumask_empty(cpumask))
2857
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871
	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).
	 */
2872
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2873
	set_freezable();
L
Linus Torvalds 已提交
2874

2875
	order = new_order = 0;
2876
	balanced_order = 0;
2877
	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2878
	balanced_classzone_idx = classzone_idx;
L
Linus Torvalds 已提交
2879
	for ( ; ; ) {
2880
		int ret;
2881

2882 2883 2884 2885 2886
		/*
		 * If the last balance_pgdat was unsuccessful it's unlikely a
		 * new request of a similar or harder type will succeed soon
		 * so consider going to sleep on the basis we reclaimed at
		 */
2887 2888
		if (balanced_classzone_idx >= new_classzone_idx &&
					balanced_order == new_order) {
2889 2890 2891 2892 2893 2894
			new_order = pgdat->kswapd_max_order;
			new_classzone_idx = pgdat->classzone_idx;
			pgdat->kswapd_max_order =  0;
			pgdat->classzone_idx = pgdat->nr_zones - 1;
		}

2895
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
2896 2897
			/*
			 * Don't sleep if someone wants a larger 'order'
2898
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
2899 2900
			 */
			order = new_order;
2901
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
2902
		} else {
2903 2904
			kswapd_try_to_sleep(pgdat, balanced_order,
						balanced_classzone_idx);
L
Linus Torvalds 已提交
2905
			order = pgdat->kswapd_max_order;
2906
			classzone_idx = pgdat->classzone_idx;
2907 2908
			new_order = order;
			new_classzone_idx = classzone_idx;
2909
			pgdat->kswapd_max_order = 0;
2910
			pgdat->classzone_idx = pgdat->nr_zones - 1;
L
Linus Torvalds 已提交
2911 2912
		}

2913 2914 2915 2916 2917 2918 2919 2920
		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
		 */
2921 2922
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2923 2924 2925
			balanced_classzone_idx = classzone_idx;
			balanced_order = balance_pgdat(pgdat, order,
						&balanced_classzone_idx);
2926
		}
L
Linus Torvalds 已提交
2927 2928 2929 2930 2931 2932 2933
	}
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
2934
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
2935 2936 2937
{
	pg_data_t *pgdat;

2938
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2939 2940
		return;

2941
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2942
		return;
2943
	pgdat = zone->zone_pgdat;
2944
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
2945
		pgdat->kswapd_max_order = order;
2946 2947
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
2948
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2949
		return;
2950 2951 2952 2953
	if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
		return;

	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2954
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2955 2956
}

2957 2958 2959 2960 2961 2962 2963 2964
/*
 * 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)
2965
{
2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989
	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;
2990 2991
}

2992
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2993
/*
2994
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2995 2996 2997 2998 2999
 * 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
3000
 */
3001
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
3002
{
3003 3004
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
3005 3006 3007
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
3008
		.may_writepage = 1,
3009 3010 3011
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.order = 0,
L
Linus Torvalds 已提交
3012
	};
3013 3014 3015 3016
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3017 3018
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
3019

3020 3021 3022 3023
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3024

3025
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3026

3027 3028 3029
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
3030

3031
	return nr_reclaimed;
L
Linus Torvalds 已提交
3032
}
3033
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
3034 3035 3036 3037 3038

/* 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. */
3039
static int __devinit cpu_callback(struct notifier_block *nfb,
3040
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
3041
{
3042
	int nid;
L
Linus Torvalds 已提交
3043

3044
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3045
		for_each_node_state(nid, N_HIGH_MEMORY) {
3046
			pg_data_t *pgdat = NODE_DATA(nid);
3047 3048 3049
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
3050

3051
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
3052
				/* One of our CPUs online: restore mask */
3053
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
3054 3055 3056 3057 3058
		}
	}
	return NOTIFY_OK;
}

3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080
/*
 * 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;
}

3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091
/*
 * 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
3092 3093
static int __init kswapd_init(void)
{
3094
	int nid;
3095

L
Linus Torvalds 已提交
3096
	swap_setup();
3097
	for_each_node_state(nid, N_HIGH_MEMORY)
3098
 		kswapd_run(nid);
L
Linus Torvalds 已提交
3099 3100 3101 3102 3103
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
3104 3105 3106 3107 3108 3109 3110 3111 3112 3113

#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;

3114
#define RECLAIM_OFF 0
3115
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
3116 3117 3118
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

3119 3120 3121 3122 3123 3124 3125
/*
 * 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

3126 3127 3128 3129 3130 3131
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

3132 3133 3134 3135 3136 3137
/*
 * 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;

3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179
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;
}

3180 3181 3182
/*
 * Try to free up some pages from this zone through reclaim.
 */
3183
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3184
{
3185
	/* Minimum pages needed in order to stay on node */
3186
	const unsigned long nr_pages = 1 << order;
3187 3188
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
3189
	int priority;
3190 3191
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3192
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3193
		.may_swap = 1,
3194 3195
		.nr_to_reclaim = max_t(unsigned long, nr_pages,
				       SWAP_CLUSTER_MAX),
3196
		.gfp_mask = gfp_mask,
3197
		.order = order,
3198
	};
3199 3200 3201
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
3202
	unsigned long nr_slab_pages0, nr_slab_pages1;
3203 3204

	cond_resched();
3205 3206 3207 3208 3209 3210
	/*
	 * 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;
3211
	lockdep_set_current_reclaim_state(gfp_mask);
3212 3213
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3214

3215
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3216 3217 3218 3219 3220 3221
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
3222
			shrink_zone(priority, zone, &sc);
3223
			priority--;
3224
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3225
	}
3226

3227 3228
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
3229
		/*
3230
		 * shrink_slab() does not currently allow us to determine how
3231 3232 3233 3234
		 * 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.
3235
		 *
3236 3237
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
3238
		 */
3239 3240 3241 3242
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
3243
			if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3244 3245 3246 3247 3248 3249 3250 3251
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3252 3253 3254 3255 3256

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3257 3258 3259
		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;
3260 3261
	}

3262
	p->reclaim_state = NULL;
3263
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3264
	lockdep_clear_current_reclaim_state();
3265
	return sc.nr_reclaimed >= nr_pages;
3266
}
3267 3268 3269 3270

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3271
	int ret;
3272 3273

	/*
3274 3275
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3276
	 *
3277 3278 3279 3280 3281
	 * 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.
3282
	 */
3283 3284
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3285
		return ZONE_RECLAIM_FULL;
3286

3287
	if (zone->all_unreclaimable)
3288
		return ZONE_RECLAIM_FULL;
3289

3290
	/*
3291
	 * Do not scan if the allocation should not be delayed.
3292
	 */
3293
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3294
		return ZONE_RECLAIM_NOSCAN;
3295 3296 3297 3298 3299 3300 3301

	/*
	 * 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.
	 */
3302
	node_id = zone_to_nid(zone);
3303
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3304
		return ZONE_RECLAIM_NOSCAN;
3305 3306

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3307 3308
		return ZONE_RECLAIM_NOSCAN;

3309 3310 3311
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3312 3313 3314
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3315
	return ret;
3316
}
3317
#endif
L
Lee Schermerhorn 已提交
3318 3319 3320 3321 3322 3323 3324

/*
 * 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
3325 3326
 * 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
3327 3328
 *
 * Reasons page might not be evictable:
3329
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3330
 * (2) page is part of an mlocked VMA
3331
 *
L
Lee Schermerhorn 已提交
3332 3333 3334 3335
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

3336 3337 3338
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
3339 3340
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
3341 3342 3343

	return 1;
}
3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362

/**
 * 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)) {
3363
		enum lru_list l = page_lru_base_type(page);
3364

3365 3366
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
3367
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3368 3369 3370 3371 3372 3373 3374 3375
		__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
3376
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435
		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);
	}

}
3436

3437
static void warn_scan_unevictable_pages(void)
3438
{
3439
	printk_once(KERN_WARNING
3440
		    "%s: The scan_unevictable_pages sysctl/node-interface has been "
3441
		    "disabled for lack of a legitimate use case.  If you have "
3442 3443
		    "one, please send an email to linux-mm@kvack.org.\n",
		    current->comm);
3444 3445 3446 3447 3448 3449 3450 3451 3452
}

/*
 * 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,
3453
			   void __user *buffer,
3454 3455
			   size_t *length, loff_t *ppos)
{
3456
	warn_scan_unevictable_pages();
3457
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3458 3459 3460 3461
	scan_unevictable_pages = 0;
	return 0;
}

3462
#ifdef CONFIG_NUMA
3463 3464 3465 3466 3467
/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

3468 3469
static ssize_t read_scan_unevictable_node(struct device *dev,
					  struct device_attribute *attr,
3470 3471
					  char *buf)
{
3472
	warn_scan_unevictable_pages();
3473 3474 3475
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

3476 3477
static ssize_t write_scan_unevictable_node(struct device *dev,
					   struct device_attribute *attr,
3478 3479
					const char *buf, size_t count)
{
3480
	warn_scan_unevictable_pages();
3481 3482 3483 3484
	return 1;
}


3485
static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3486 3487 3488 3489 3490
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
3491
	return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3492 3493 3494 3495
}

void scan_unevictable_unregister_node(struct node *node)
{
3496
	device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
3497
}
3498
#endif