vmscan.c 106.7 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/vmpressure.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/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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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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	/* Scan (total_size >> priority) pages at once */
	int priority;

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	/*
	 * The memory cgroup that hit its limit and as a result is the
	 * primary target of this reclaim invocation.
	 */
	struct mem_cgroup *target_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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unsigned 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_MEMCG
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static bool global_reclaim(struct scan_control *sc)
{
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	return !sc->target_mem_cgroup;
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}
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#else
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static bool global_reclaim(struct scan_control *sc)
{
	return true;
}
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#endif

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

	return nr;
}

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

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static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
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{
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	if (!mem_cgroup_disabled())
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		return mem_cgroup_get_lru_size(lruvec, lru);
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	return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
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}

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/*
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 * Add a shrinker callback to be called from the vm.
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 */
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int register_shrinker(struct shrinker *shrinker)
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{
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	size_t size = sizeof(*shrinker->nr_deferred);

	/*
	 * If we only have one possible node in the system anyway, save
	 * ourselves the trouble and disable NUMA aware behavior. This way we
	 * will save memory and some small loop time later.
	 */
	if (nr_node_ids == 1)
		shrinker->flags &= ~SHRINKER_NUMA_AWARE;

	if (shrinker->flags & SHRINKER_NUMA_AWARE)
		size *= nr_node_ids;

	shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
	if (!shrinker->nr_deferred)
		return -ENOMEM;

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	down_write(&shrinker_rwsem);
	list_add_tail(&shrinker->list, &shrinker_list);
	up_write(&shrinker_rwsem);
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	return 0;
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}
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EXPORT_SYMBOL(register_shrinker);
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/*
 * Remove one
 */
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void unregister_shrinker(struct shrinker *shrinker)
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{
	down_write(&shrinker_rwsem);
	list_del(&shrinker->list);
	up_write(&shrinker_rwsem);
}
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EXPORT_SYMBOL(unregister_shrinker);
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#define SHRINK_BATCH 128
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static unsigned long
shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
		 unsigned long nr_pages_scanned, unsigned long lru_pages)
{
	unsigned long freed = 0;
	unsigned long long delta;
	long total_scan;
	long max_pass;
	long nr;
	long new_nr;
	int nid = shrinkctl->nid;
	long batch_size = shrinker->batch ? shrinker->batch
					  : SHRINK_BATCH;

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	max_pass = shrinker->count_objects(shrinker, shrinkctl);
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	if (max_pass == 0)
		return 0;

	/*
	 * 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.
	 */
	nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);

	total_scan = nr;
	delta = (4 * nr_pages_scanned) / shrinker->seeks;
	delta *= max_pass;
	do_div(delta, lru_pages + 1);
	total_scan += delta;
	if (total_scan < 0) {
		printk(KERN_ERR
		"shrink_slab: %pF negative objects to delete nr=%ld\n",
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		       shrinker->scan_objects, total_scan);
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		total_scan = max_pass;
	}

	/*
	 * 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);

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

	trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
				nr_pages_scanned, lru_pages,
				max_pass, delta, total_scan);

	while (total_scan >= batch_size) {
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		unsigned long ret;
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		shrinkctl->nr_to_scan = batch_size;
		ret = shrinker->scan_objects(shrinker, shrinkctl);
		if (ret == SHRINK_STOP)
			break;
		freed += ret;
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		count_vm_events(SLABS_SCANNED, batch_size);
		total_scan -= batch_size;

		cond_resched();
	}

	/*
	 * 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.
	 */
	if (total_scan > 0)
		new_nr = atomic_long_add_return(total_scan,
						&shrinker->nr_deferred[nid]);
	else
		new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);

	trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr);
	return freed;
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}

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/*
 * 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 *shrinkctl,
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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 freed = 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)) {
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		/*
		 * If we would return 0, our callers would understand that we
		 * have nothing else to shrink and give up trying. By returning
		 * 1 we keep it going and assume we'll be able to shrink next
		 * time.
		 */
		freed = 1;
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		goto out;
	}
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	list_for_each_entry(shrinker, &shrinker_list, list) {
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		for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
			if (!node_online(shrinkctl->nid))
				continue;
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			if (!(shrinker->flags & SHRINKER_NUMA_AWARE) &&
			    (shrinkctl->nid != 0))
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				break;

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			freed += shrink_slab_node(shrinkctl, shrinker,
				 nr_pages_scanned, lru_pages);
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		}
	}
	up_read(&shrinker_rwsem);
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out:
	cond_resched();
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	return freed;
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}

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

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static int may_write_to_queue(struct backing_dev_info *bdi,
			      struct scan_control *sc)
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{
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	if (current->flags & PF_SWAPWRITE)
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		return 1;
	if (!bdi_write_congested(bdi))
		return 1;
	if (bdi == current->backing_dev_info)
		return 1;
	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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 */
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static pageout_t pageout(struct page *page, struct address_space *mapping,
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			 struct scan_control *sc)
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{
	/*
	 * If the page is dirty, only perform writeback if that write
	 * will be non-blocking.  To prevent this allocation from being
	 * stalled by pagecache activity.  But note that there may be
	 * stalls if we need to run get_block().  We could test
	 * PagePrivate for that.
	 *
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	 * If this process is currently in __generic_file_aio_write() against
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	 * this page's queue, we can perform writeback even if that
	 * will block.
	 *
	 * If the page is swapcache, write it back even if that would
	 * block, for some throttling. This happens by accident, because
	 * swap_backing_dev_info is bust: it doesn't reflect the
	 * congestion state of the swapdevs.  Easy to fix, if needed.
	 */
	if (!is_page_cache_freeable(page))
		return PAGE_KEEP;
	if (!mapping) {
		/*
		 * Some data journaling orphaned pages can have
		 * page->mapping == NULL while being dirty with clean buffers.
		 */
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		if (page_has_private(page)) {
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			if (try_to_free_buffers(page)) {
				ClearPageDirty(page);
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				printk("%s: orphaned page\n", __func__);
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				return PAGE_CLEAN;
			}
		}
		return PAGE_KEEP;
	}
	if (mapping->a_ops->writepage == NULL)
		return PAGE_ACTIVATE;
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	if (!may_write_to_queue(mapping->backing_dev_info, sc))
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		return PAGE_KEEP;

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

		SetPageReclaim(page);
		res = mapping->a_ops->writepage(page, &wbc);
		if (res < 0)
			handle_write_error(mapping, page, res);
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		if (res == AOP_WRITEPAGE_ACTIVATE) {
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			ClearPageReclaim(page);
			return PAGE_ACTIVATE;
		}
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		if (!PageWriteback(page)) {
			/* synchronous write or broken a_ops? */
			ClearPageReclaim(page);
		}
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		trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
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		inc_zone_page_state(page, NR_VMSCAN_WRITE);
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		return PAGE_SUCCESS;
	}

	return PAGE_CLEAN;
}

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

	return 1;

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

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

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Lee Schermerhorn 已提交
590 591 592 593 594 595 596 597 598 599 600
/**
 * 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)
{
601
	bool is_unevictable;
602
	int was_unevictable = PageUnevictable(page);
L
Lee Schermerhorn 已提交
603 604 605 606 607 608

	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

609
	if (page_evictable(page)) {
L
Lee Schermerhorn 已提交
610 611 612 613 614 615
		/*
		 * 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.
		 */
616
		is_unevictable = false;
617
		lru_cache_add(page);
L
Lee Schermerhorn 已提交
618 619 620 621 622
	} else {
		/*
		 * Put unevictable pages directly on zone's unevictable
		 * list.
		 */
623
		is_unevictable = true;
L
Lee Schermerhorn 已提交
624
		add_page_to_unevictable_list(page);
625
		/*
626 627 628
		 * 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
629
		 * isolation/check_move_unevictable_pages,
630
		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
631 632
		 * the page back to the evictable list.
		 *
633
		 * The other side is TestClearPageMlocked() or shmem_lock().
634 635
		 */
		smp_mb();
L
Lee Schermerhorn 已提交
636 637 638 639 640 641 642
	}

	/*
	 * 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.
	 */
643
	if (is_unevictable && page_evictable(page)) {
L
Lee Schermerhorn 已提交
644 645 646 647 648 649 650 651 652 653
		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.
		 */
	}

654
	if (was_unevictable && !is_unevictable)
655
		count_vm_event(UNEVICTABLE_PGRESCUED);
656
	else if (!was_unevictable && is_unevictable)
657 658
		count_vm_event(UNEVICTABLE_PGCULLED);

L
Lee Schermerhorn 已提交
659 660 661
	put_page(page);		/* drop ref from isolate */
}

662 663 664
enum page_references {
	PAGEREF_RECLAIM,
	PAGEREF_RECLAIM_CLEAN,
665
	PAGEREF_KEEP,
666 667 668 669 670 671
	PAGEREF_ACTIVATE,
};

static enum page_references page_check_references(struct page *page,
						  struct scan_control *sc)
{
672
	int referenced_ptes, referenced_page;
673 674
	unsigned long vm_flags;

675 676
	referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
					  &vm_flags);
677
	referenced_page = TestClearPageReferenced(page);
678 679 680 681 682 683 684 685

	/*
	 * 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;

686
	if (referenced_ptes) {
687
		if (PageSwapBacked(page))
688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704
			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);

705
		if (referenced_page || referenced_ptes > 1)
706 707
			return PAGEREF_ACTIVATE;

708 709 710 711 712 713
		/*
		 * Activate file-backed executable pages after first usage.
		 */
		if (vm_flags & VM_EXEC)
			return PAGEREF_ACTIVATE;

714 715
		return PAGEREF_KEEP;
	}
716 717

	/* Reclaim if clean, defer dirty pages to writeback */
718
	if (referenced_page && !PageSwapBacked(page))
719 720 721
		return PAGEREF_RECLAIM_CLEAN;

	return PAGEREF_RECLAIM;
722 723
}

724 725 726 727
/* Check if a page is dirty or under writeback */
static void page_check_dirty_writeback(struct page *page,
				       bool *dirty, bool *writeback)
{
728 729
	struct address_space *mapping;

730 731 732 733 734 735 736 737 738 739 740 741 742
	/*
	 * Anonymous pages are not handled by flushers and must be written
	 * from reclaim context. Do not stall reclaim based on them
	 */
	if (!page_is_file_cache(page)) {
		*dirty = false;
		*writeback = false;
		return;
	}

	/* By default assume that the page flags are accurate */
	*dirty = PageDirty(page);
	*writeback = PageWriteback(page);
743 744 745 746 747 748 749 750

	/* Verify dirty/writeback state if the filesystem supports it */
	if (!page_has_private(page))
		return;

	mapping = page_mapping(page);
	if (mapping && mapping->a_ops->is_dirty_writeback)
		mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
751 752
}

L
Linus Torvalds 已提交
753
/*
A
Andrew Morton 已提交
754
 * shrink_page_list() returns the number of reclaimed pages
L
Linus Torvalds 已提交
755
 */
A
Andrew Morton 已提交
756
static unsigned long shrink_page_list(struct list_head *page_list,
757
				      struct zone *zone,
758
				      struct scan_control *sc,
759
				      enum ttu_flags ttu_flags,
760
				      unsigned long *ret_nr_dirty,
761
				      unsigned long *ret_nr_unqueued_dirty,
762
				      unsigned long *ret_nr_congested,
763
				      unsigned long *ret_nr_writeback,
764
				      unsigned long *ret_nr_immediate,
765
				      bool force_reclaim)
L
Linus Torvalds 已提交
766 767
{
	LIST_HEAD(ret_pages);
768
	LIST_HEAD(free_pages);
L
Linus Torvalds 已提交
769
	int pgactivate = 0;
770
	unsigned long nr_unqueued_dirty = 0;
771 772
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
773
	unsigned long nr_reclaimed = 0;
774
	unsigned long nr_writeback = 0;
775
	unsigned long nr_immediate = 0;
L
Linus Torvalds 已提交
776 777 778

	cond_resched();

779
	mem_cgroup_uncharge_start();
L
Linus Torvalds 已提交
780 781 782 783
	while (!list_empty(page_list)) {
		struct address_space *mapping;
		struct page *page;
		int may_enter_fs;
784
		enum page_references references = PAGEREF_RECLAIM_CLEAN;
785
		bool dirty, writeback;
L
Linus Torvalds 已提交
786 787 788 789 790 791

		cond_resched();

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

N
Nick Piggin 已提交
792
		if (!trylock_page(page))
L
Linus Torvalds 已提交
793 794
			goto keep;

N
Nick Piggin 已提交
795
		VM_BUG_ON(PageActive(page));
796
		VM_BUG_ON(page_zone(page) != zone);
L
Linus Torvalds 已提交
797 798

		sc->nr_scanned++;
799

800
		if (unlikely(!page_evictable(page)))
N
Nick Piggin 已提交
801
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
802

803
		if (!sc->may_unmap && page_mapped(page))
804 805
			goto keep_locked;

L
Linus Torvalds 已提交
806 807 808 809
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

810 811 812
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

813 814 815 816 817 818 819 820 821 822 823 824 825
		/*
		 * The number of dirty pages determines if a zone is marked
		 * reclaim_congested which affects wait_iff_congested. kswapd
		 * will stall and start writing pages if the tail of the LRU
		 * is all dirty unqueued pages.
		 */
		page_check_dirty_writeback(page, &dirty, &writeback);
		if (dirty || writeback)
			nr_dirty++;

		if (dirty && !writeback)
			nr_unqueued_dirty++;

826 827 828 829 830 831
		/*
		 * Treat this page as congested if the underlying BDI is or if
		 * pages are cycling through the LRU so quickly that the
		 * pages marked for immediate reclaim are making it to the
		 * end of the LRU a second time.
		 */
832
		mapping = page_mapping(page);
833 834
		if ((mapping && bdi_write_congested(mapping->backing_dev_info)) ||
		    (writeback && PageReclaim(page)))
835 836
			nr_congested++;

837 838 839 840 841 842 843 844 845 846 847
		/*
		 * If a page at the tail of the LRU is under writeback, there
		 * are three cases to consider.
		 *
		 * 1) If reclaim is encountering an excessive number of pages
		 *    under writeback and this page is both under writeback and
		 *    PageReclaim then it indicates that pages are being queued
		 *    for IO but are being recycled through the LRU before the
		 *    IO can complete. Waiting on the page itself risks an
		 *    indefinite stall if it is impossible to writeback the
		 *    page due to IO error or disconnected storage so instead
848 849
		 *    note that the LRU is being scanned too quickly and the
		 *    caller can stall after page list has been processed.
850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873
		 *
		 * 2) Global reclaim encounters a page, memcg encounters a
		 *    page that is not marked for immediate reclaim or
		 *    the caller does not have __GFP_IO. In this case mark
		 *    the page for immediate reclaim and continue scanning.
		 *
		 *    __GFP_IO is checked  because a loop driver thread might
		 *    enter reclaim, and deadlock if it waits on a page for
		 *    which it is needed to do the write (loop masks off
		 *    __GFP_IO|__GFP_FS for this reason); but more thought
		 *    would probably show more reasons.
		 *
		 *    Don't require __GFP_FS, since we're not going into the
		 *    FS, just waiting on its writeback completion. Worryingly,
		 *    ext4 gfs2 and xfs allocate pages with
		 *    grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
		 *    may_enter_fs here is liable to OOM on them.
		 *
		 * 3) memcg encounters a page that is not already marked
		 *    PageReclaim. memcg does not have any dirty pages
		 *    throttling so we could easily OOM just because too many
		 *    pages are in writeback and there is nothing else to
		 *    reclaim. Wait for the writeback to complete.
		 */
874
		if (PageWriteback(page)) {
875 876 877 878
			/* Case 1 above */
			if (current_is_kswapd() &&
			    PageReclaim(page) &&
			    zone_is_reclaim_writeback(zone)) {
879 880
				nr_immediate++;
				goto keep_locked;
881 882 883

			/* Case 2 above */
			} else if (global_reclaim(sc) ||
884 885 886 887 888 889 890 891 892 893 894 895 896
			    !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
				/*
				 * This is slightly racy - end_page_writeback()
				 * might have just cleared PageReclaim, then
				 * setting PageReclaim here end up interpreted
				 * as PageReadahead - but that does not matter
				 * enough to care.  What we do want is for this
				 * page to have PageReclaim set next time memcg
				 * reclaim reaches the tests above, so it will
				 * then wait_on_page_writeback() to avoid OOM;
				 * and it's also appropriate in global reclaim.
				 */
				SetPageReclaim(page);
897
				nr_writeback++;
898

899
				goto keep_locked;
900 901 902 903

			/* Case 3 above */
			} else {
				wait_on_page_writeback(page);
904
			}
905
		}
L
Linus Torvalds 已提交
906

907 908 909
		if (!force_reclaim)
			references = page_check_references(page, sc);

910 911
		switch (references) {
		case PAGEREF_ACTIVATE:
L
Linus Torvalds 已提交
912
			goto activate_locked;
913 914
		case PAGEREF_KEEP:
			goto keep_locked;
915 916 917 918
		case PAGEREF_RECLAIM:
		case PAGEREF_RECLAIM_CLEAN:
			; /* try to reclaim the page below */
		}
L
Linus Torvalds 已提交
919 920 921 922 923

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
924
		if (PageAnon(page) && !PageSwapCache(page)) {
925 926
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
927
			if (!add_to_swap(page, page_list))
L
Linus Torvalds 已提交
928
				goto activate_locked;
929
			may_enter_fs = 1;
L
Linus Torvalds 已提交
930

931 932 933
			/* Adding to swap updated mapping */
			mapping = page_mapping(page);
		}
L
Linus Torvalds 已提交
934 935 936 937 938 939

		/*
		 * The page is mapped into the page tables of one or more
		 * processes. Try to unmap it here.
		 */
		if (page_mapped(page) && mapping) {
940
			switch (try_to_unmap(page, ttu_flags)) {
L
Linus Torvalds 已提交
941 942 943 944
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
945 946
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
947 948 949 950 951 952
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
953 954
			/*
			 * Only kswapd can writeback filesystem pages to
955 956
			 * avoid risk of stack overflow but only writeback
			 * if many dirty pages have been encountered.
957
			 */
958
			if (page_is_file_cache(page) &&
959
					(!current_is_kswapd() ||
960
					 !zone_is_reclaim_dirty(zone))) {
961 962 963 964 965 966 967 968 969
				/*
				 * 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);

970 971 972
				goto keep_locked;
			}

973
			if (references == PAGEREF_RECLAIM_CLEAN)
L
Linus Torvalds 已提交
974
				goto keep_locked;
975
			if (!may_enter_fs)
L
Linus Torvalds 已提交
976
				goto keep_locked;
977
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
978 979 980
				goto keep_locked;

			/* Page is dirty, try to write it out here */
981
			switch (pageout(page, mapping, sc)) {
L
Linus Torvalds 已提交
982 983 984 985 986
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
987
				if (PageWriteback(page))
988
					goto keep;
989
				if (PageDirty(page))
L
Linus Torvalds 已提交
990
					goto keep;
991

L
Linus Torvalds 已提交
992 993 994 995
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
996
				if (!trylock_page(page))
L
Linus Torvalds 已提交
997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
					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
1016
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
1017 1018 1019 1020 1021 1022 1023 1024 1025 1026
		 * 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.
		 */
1027
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
1028 1029
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045
			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
1046 1047
		}

N
Nick Piggin 已提交
1048
		if (!mapping || !__remove_mapping(mapping, page))
1049
			goto keep_locked;
L
Linus Torvalds 已提交
1050

N
Nick Piggin 已提交
1051 1052 1053 1054 1055 1056 1057 1058
		/*
		 * 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
1059
free_it:
1060
		nr_reclaimed++;
1061 1062 1063 1064 1065 1066

		/*
		 * 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
1067 1068
		continue;

N
Nick Piggin 已提交
1069
cull_mlocked:
1070 1071
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
1072 1073 1074 1075
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
1076
activate_locked:
1077 1078
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
1079
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
1080
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
1081 1082 1083 1084 1085 1086
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
1087
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
1088
	}
1089

1090
	free_hot_cold_page_list(&free_pages, 1);
1091

L
Linus Torvalds 已提交
1092
	list_splice(&ret_pages, page_list);
1093
	count_vm_events(PGACTIVATE, pgactivate);
1094
	mem_cgroup_uncharge_end();
1095 1096
	*ret_nr_dirty += nr_dirty;
	*ret_nr_congested += nr_congested;
1097
	*ret_nr_unqueued_dirty += nr_unqueued_dirty;
1098
	*ret_nr_writeback += nr_writeback;
1099
	*ret_nr_immediate += nr_immediate;
1100
	return nr_reclaimed;
L
Linus Torvalds 已提交
1101 1102
}

1103 1104 1105 1106 1107 1108 1109 1110
unsigned long reclaim_clean_pages_from_list(struct zone *zone,
					    struct list_head *page_list)
{
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
		.priority = DEF_PRIORITY,
		.may_unmap = 1,
	};
1111
	unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122
	struct page *page, *next;
	LIST_HEAD(clean_pages);

	list_for_each_entry_safe(page, next, page_list, lru) {
		if (page_is_file_cache(page) && !PageDirty(page)) {
			ClearPageActive(page);
			list_move(&page->lru, &clean_pages);
		}
	}

	ret = shrink_page_list(&clean_pages, zone, &sc,
1123 1124
			TTU_UNMAP|TTU_IGNORE_ACCESS,
			&dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
1125 1126 1127 1128 1129
	list_splice(&clean_pages, page_list);
	__mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
	return ret;
}

A
Andy Whitcroft 已提交
1130 1131 1132 1133 1134 1135 1136 1137 1138 1139
/*
 * 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.
 */
1140
int __isolate_lru_page(struct page *page, isolate_mode_t mode)
A
Andy Whitcroft 已提交
1141 1142 1143 1144 1145 1146 1147
{
	int ret = -EINVAL;

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

M
Minchan Kim 已提交
1148 1149
	/* Compaction should not handle unevictable pages but CMA can do so */
	if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
L
Lee Schermerhorn 已提交
1150 1151
		return ret;

A
Andy Whitcroft 已提交
1152
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
1153

1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186
	/*
	 * To minimise LRU disruption, the caller can indicate that it only
	 * wants to isolate pages it will be able to operate on without
	 * blocking - clean pages for the most part.
	 *
	 * ISOLATE_CLEAN means that only clean pages should be isolated. This
	 * is used by reclaim when it is cannot write to backing storage
	 *
	 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
	 * that it is possible to migrate without blocking
	 */
	if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
		/* All the caller can do on PageWriteback is block */
		if (PageWriteback(page))
			return ret;

		if (PageDirty(page)) {
			struct address_space *mapping;

			/* ISOLATE_CLEAN means only clean pages */
			if (mode & ISOLATE_CLEAN)
				return ret;

			/*
			 * Only pages without mappings or that have a
			 * ->migratepage callback are possible to migrate
			 * without blocking
			 */
			mapping = page_mapping(page);
			if (mapping && !mapping->a_ops->migratepage)
				return ret;
		}
	}
1187

1188 1189 1190
	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
		return ret;

A
Andy Whitcroft 已提交
1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203
	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
1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214
/*
 * 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.
1215
 * @lruvec:	The LRU vector to pull pages from.
L
Linus Torvalds 已提交
1216
 * @dst:	The temp list to put pages on to.
H
Hugh Dickins 已提交
1217
 * @nr_scanned:	The number of pages that were scanned.
1218
 * @sc:		The scan_control struct for this reclaim session
A
Andy Whitcroft 已提交
1219
 * @mode:	One of the LRU isolation modes
1220
 * @lru:	LRU list id for isolating
L
Linus Torvalds 已提交
1221 1222 1223
 *
 * returns how many pages were moved onto *@dst.
 */
1224
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1225
		struct lruvec *lruvec, struct list_head *dst,
1226
		unsigned long *nr_scanned, struct scan_control *sc,
1227
		isolate_mode_t mode, enum lru_list lru)
L
Linus Torvalds 已提交
1228
{
H
Hugh Dickins 已提交
1229
	struct list_head *src = &lruvec->lists[lru];
1230
	unsigned long nr_taken = 0;
1231
	unsigned long scan;
L
Linus Torvalds 已提交
1232

1233
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
1234
		struct page *page;
1235
		int nr_pages;
A
Andy Whitcroft 已提交
1236

L
Linus Torvalds 已提交
1237 1238 1239
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
1240
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
1241

1242
		switch (__isolate_lru_page(page, mode)) {
A
Andy Whitcroft 已提交
1243
		case 0:
1244 1245
			nr_pages = hpage_nr_pages(page);
			mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
A
Andy Whitcroft 已提交
1246
			list_move(&page->lru, dst);
1247
			nr_taken += nr_pages;
A
Andy Whitcroft 已提交
1248 1249 1250 1251 1252 1253
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
1254

A
Andy Whitcroft 已提交
1255 1256 1257
		default:
			BUG();
		}
L
Linus Torvalds 已提交
1258 1259
	}

H
Hugh Dickins 已提交
1260
	*nr_scanned = scan;
H
Hugh Dickins 已提交
1261 1262
	trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
				    nr_taken, mode, is_file_lru(lru));
L
Linus Torvalds 已提交
1263 1264 1265
	return nr_taken;
}

1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276
/**
 * 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
1277 1278 1279
 * 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.
1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294
 *
 * 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;

1295 1296
	VM_BUG_ON(!page_count(page));

1297 1298
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);
1299
		struct lruvec *lruvec;
1300 1301

		spin_lock_irq(&zone->lru_lock);
1302
		lruvec = mem_cgroup_page_lruvec(page, zone);
1303
		if (PageLRU(page)) {
L
Lee Schermerhorn 已提交
1304
			int lru = page_lru(page);
1305
			get_page(page);
1306
			ClearPageLRU(page);
1307 1308
			del_page_from_lru_list(page, lruvec, lru);
			ret = 0;
1309 1310 1311 1312 1313 1314
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1315
/*
F
Fengguang Wu 已提交
1316 1317 1318 1319 1320
 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
 * then get resheduled. When there are massive number of tasks doing page
 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
 * the LRU list will go small and be scanned faster than necessary, leading to
 * unnecessary swapping, thrashing and OOM.
1321 1322 1323 1324 1325 1326 1327 1328 1329
 */
static int too_many_isolated(struct zone *zone, int file,
		struct scan_control *sc)
{
	unsigned long inactive, isolated;

	if (current_is_kswapd())
		return 0;

1330
	if (!global_reclaim(sc))
1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
		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);
	}

1341 1342 1343 1344 1345 1346 1347 1348
	/*
	 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
	 * won't get blocked by normal direct-reclaimers, forming a circular
	 * deadlock.
	 */
	if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
		inactive >>= 3;

1349 1350 1351
	return isolated > inactive;
}

1352
static noinline_for_stack void
H
Hugh Dickins 已提交
1353
putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
1354
{
1355 1356
	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
	struct zone *zone = lruvec_zone(lruvec);
1357
	LIST_HEAD(pages_to_free);
1358 1359 1360 1361 1362

	/*
	 * Put back any unfreeable pages.
	 */
	while (!list_empty(page_list)) {
1363
		struct page *page = lru_to_page(page_list);
1364
		int lru;
1365

1366 1367
		VM_BUG_ON(PageLRU(page));
		list_del(&page->lru);
1368
		if (unlikely(!page_evictable(page))) {
1369 1370 1371 1372 1373
			spin_unlock_irq(&zone->lru_lock);
			putback_lru_page(page);
			spin_lock_irq(&zone->lru_lock);
			continue;
		}
1374 1375 1376

		lruvec = mem_cgroup_page_lruvec(page, zone);

1377
		SetPageLRU(page);
1378
		lru = page_lru(page);
1379 1380
		add_page_to_lru_list(page, lruvec, lru);

1381 1382
		if (is_active_lru(lru)) {
			int file = is_file_lru(lru);
1383 1384
			int numpages = hpage_nr_pages(page);
			reclaim_stat->recent_rotated[file] += numpages;
1385
		}
1386 1387 1388
		if (put_page_testzero(page)) {
			__ClearPageLRU(page);
			__ClearPageActive(page);
1389
			del_page_from_lru_list(page, lruvec, lru);
1390 1391 1392 1393 1394 1395 1396

			if (unlikely(PageCompound(page))) {
				spin_unlock_irq(&zone->lru_lock);
				(*get_compound_page_dtor(page))(page);
				spin_lock_irq(&zone->lru_lock);
			} else
				list_add(&page->lru, &pages_to_free);
1397 1398 1399
		}
	}

1400 1401 1402 1403
	/*
	 * To save our caller's stack, now use input list for pages to free.
	 */
	list_splice(&pages_to_free, page_list);
1404 1405
}

L
Linus Torvalds 已提交
1406
/*
A
Andrew Morton 已提交
1407 1408
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1409
 */
1410
static noinline_for_stack unsigned long
1411
shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
1412
		     struct scan_control *sc, enum lru_list lru)
L
Linus Torvalds 已提交
1413 1414
{
	LIST_HEAD(page_list);
1415
	unsigned long nr_scanned;
1416
	unsigned long nr_reclaimed = 0;
1417
	unsigned long nr_taken;
1418 1419
	unsigned long nr_dirty = 0;
	unsigned long nr_congested = 0;
1420
	unsigned long nr_unqueued_dirty = 0;
1421
	unsigned long nr_writeback = 0;
1422
	unsigned long nr_immediate = 0;
1423
	isolate_mode_t isolate_mode = 0;
1424
	int file = is_file_lru(lru);
1425 1426
	struct zone *zone = lruvec_zone(lruvec);
	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1427

1428
	while (unlikely(too_many_isolated(zone, file, sc))) {
1429
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1430 1431 1432 1433 1434 1435

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

L
Linus Torvalds 已提交
1436
	lru_add_drain();
1437 1438

	if (!sc->may_unmap)
1439
		isolate_mode |= ISOLATE_UNMAPPED;
1440
	if (!sc->may_writepage)
1441
		isolate_mode |= ISOLATE_CLEAN;
1442

L
Linus Torvalds 已提交
1443
	spin_lock_irq(&zone->lru_lock);
1444

1445 1446
	nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
				     &nr_scanned, sc, isolate_mode, lru);
1447 1448 1449 1450

	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);

1451
	if (global_reclaim(sc)) {
1452 1453
		zone->pages_scanned += nr_scanned;
		if (current_is_kswapd())
H
Hugh Dickins 已提交
1454
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
1455
		else
H
Hugh Dickins 已提交
1456
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
1457
	}
1458
	spin_unlock_irq(&zone->lru_lock);
1459

1460
	if (nr_taken == 0)
1461
		return 0;
A
Andy Whitcroft 已提交
1462

1463
	nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
1464 1465 1466
				&nr_dirty, &nr_unqueued_dirty, &nr_congested,
				&nr_writeback, &nr_immediate,
				false);
1467

1468 1469
	spin_lock_irq(&zone->lru_lock);

1470
	reclaim_stat->recent_scanned[file] += nr_taken;
1471

Y
Ying Han 已提交
1472 1473 1474 1475 1476 1477 1478 1479
	if (global_reclaim(sc)) {
		if (current_is_kswapd())
			__count_zone_vm_events(PGSTEAL_KSWAPD, zone,
					       nr_reclaimed);
		else
			__count_zone_vm_events(PGSTEAL_DIRECT, zone,
					       nr_reclaimed);
	}
N
Nick Piggin 已提交
1480

1481
	putback_inactive_pages(lruvec, &page_list);
1482

1483
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1484 1485 1486 1487

	spin_unlock_irq(&zone->lru_lock);

	free_hot_cold_page_list(&page_list, 1);
1488

1489 1490 1491 1492 1493 1494 1495 1496 1497 1498
	/*
	 * 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.
	 *
1499 1500 1501
	 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
	 * of pages under pages flagged for immediate reclaim and stall if any
	 * are encountered in the nr_immediate check below.
1502
	 */
1503
	if (nr_writeback && nr_writeback == nr_taken)
1504
		zone_set_flag(zone, ZONE_WRITEBACK);
1505

1506
	/*
1507 1508
	 * memcg will stall in page writeback so only consider forcibly
	 * stalling for global reclaim
1509
	 */
1510
	if (global_reclaim(sc)) {
1511 1512 1513 1514 1515 1516 1517
		/*
		 * Tag a zone as congested if all the dirty pages scanned were
		 * backed by a congested BDI and wait_iff_congested will stall.
		 */
		if (nr_dirty && nr_dirty == nr_congested)
			zone_set_flag(zone, ZONE_CONGESTED);

1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535
		/*
		 * If dirty pages are scanned that are not queued for IO, it
		 * implies that flushers are not keeping up. In this case, flag
		 * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
		 * pages from reclaim context. It will forcibly stall in the
		 * next check.
		 */
		if (nr_unqueued_dirty == nr_taken)
			zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);

		/*
		 * In addition, if kswapd scans pages marked marked for
		 * immediate reclaim and under writeback (nr_immediate), it
		 * implies that pages are cycling through the LRU faster than
		 * they are written so also forcibly stall.
		 */
		if (nr_unqueued_dirty == nr_taken || nr_immediate)
			congestion_wait(BLK_RW_ASYNC, HZ/10);
1536
	}
1537

1538 1539 1540 1541 1542 1543 1544 1545
	/*
	 * Stall direct reclaim for IO completions if underlying BDIs or zone
	 * is congested. Allow kswapd to continue until it starts encountering
	 * unqueued dirty pages or cycling through the LRU too quickly.
	 */
	if (!sc->hibernation_mode && !current_is_kswapd())
		wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);

1546 1547 1548
	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
		zone_idx(zone),
		nr_scanned, nr_reclaimed,
1549
		sc->priority,
M
Mel Gorman 已提交
1550
		trace_shrink_flags(file));
1551
	return nr_reclaimed;
L
Linus Torvalds 已提交
1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570
}

/*
 * 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.
 */
1571

1572
static void move_active_pages_to_lru(struct lruvec *lruvec,
1573
				     struct list_head *list,
1574
				     struct list_head *pages_to_free,
1575 1576
				     enum lru_list lru)
{
1577
	struct zone *zone = lruvec_zone(lruvec);
1578 1579
	unsigned long pgmoved = 0;
	struct page *page;
1580
	int nr_pages;
1581 1582 1583

	while (!list_empty(list)) {
		page = lru_to_page(list);
1584
		lruvec = mem_cgroup_page_lruvec(page, zone);
1585 1586 1587 1588

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

1589 1590
		nr_pages = hpage_nr_pages(page);
		mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
1591
		list_move(&page->lru, &lruvec->lists[lru]);
1592
		pgmoved += nr_pages;
1593

1594 1595 1596
		if (put_page_testzero(page)) {
			__ClearPageLRU(page);
			__ClearPageActive(page);
1597
			del_page_from_lru_list(page, lruvec, lru);
1598 1599 1600 1601 1602 1603 1604

			if (unlikely(PageCompound(page))) {
				spin_unlock_irq(&zone->lru_lock);
				(*get_compound_page_dtor(page))(page);
				spin_lock_irq(&zone->lru_lock);
			} else
				list_add(&page->lru, pages_to_free);
1605 1606 1607 1608 1609 1610
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	if (!is_active_lru(lru))
		__count_vm_events(PGDEACTIVATE, pgmoved);
}
1611

H
Hugh Dickins 已提交
1612
static void shrink_active_list(unsigned long nr_to_scan,
1613
			       struct lruvec *lruvec,
1614
			       struct scan_control *sc,
1615
			       enum lru_list lru)
L
Linus Torvalds 已提交
1616
{
1617
	unsigned long nr_taken;
H
Hugh Dickins 已提交
1618
	unsigned long nr_scanned;
1619
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1620
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1621
	LIST_HEAD(l_active);
1622
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1623
	struct page *page;
1624
	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1625
	unsigned long nr_rotated = 0;
1626
	isolate_mode_t isolate_mode = 0;
1627
	int file = is_file_lru(lru);
1628
	struct zone *zone = lruvec_zone(lruvec);
L
Linus Torvalds 已提交
1629 1630

	lru_add_drain();
1631 1632

	if (!sc->may_unmap)
1633
		isolate_mode |= ISOLATE_UNMAPPED;
1634
	if (!sc->may_writepage)
1635
		isolate_mode |= ISOLATE_CLEAN;
1636

L
Linus Torvalds 已提交
1637
	spin_lock_irq(&zone->lru_lock);
1638

1639 1640
	nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
				     &nr_scanned, sc, isolate_mode, lru);
1641
	if (global_reclaim(sc))
H
Hugh Dickins 已提交
1642
		zone->pages_scanned += nr_scanned;
1643

1644
	reclaim_stat->recent_scanned[file] += nr_taken;
1645

H
Hugh Dickins 已提交
1646
	__count_zone_vm_events(PGREFILL, zone, nr_scanned);
1647
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
K
KOSAKI Motohiro 已提交
1648
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1649 1650 1651 1652 1653 1654
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1655

1656
		if (unlikely(!page_evictable(page))) {
L
Lee Schermerhorn 已提交
1657 1658 1659 1660
			putback_lru_page(page);
			continue;
		}

1661 1662 1663 1664 1665 1666 1667 1668
		if (unlikely(buffer_heads_over_limit)) {
			if (page_has_private(page) && trylock_page(page)) {
				if (page_has_private(page))
					try_to_release_page(page, 0);
				unlock_page(page);
			}
		}

1669 1670
		if (page_referenced(page, 0, sc->target_mem_cgroup,
				    &vm_flags)) {
1671
			nr_rotated += hpage_nr_pages(page);
1672 1673 1674 1675 1676 1677 1678 1679 1680
			/*
			 * 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.
			 */
1681
			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1682 1683 1684 1685
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1686

1687
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1688 1689 1690
		list_add(&page->lru, &l_inactive);
	}

1691
	/*
1692
	 * Move pages back to the lru list.
1693
	 */
1694
	spin_lock_irq(&zone->lru_lock);
1695
	/*
1696 1697 1698 1699
	 * 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.
1700
	 */
1701
	reclaim_stat->recent_rotated[file] += nr_rotated;
1702

1703 1704
	move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
	move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
K
KOSAKI Motohiro 已提交
1705
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1706
	spin_unlock_irq(&zone->lru_lock);
1707 1708

	free_hot_cold_page_list(&l_hold, 1);
L
Linus Torvalds 已提交
1709 1710
}

1711
#ifdef CONFIG_SWAP
1712
static int inactive_anon_is_low_global(struct zone *zone)
1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724
{
	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;
}

1725 1726
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1727
 * @lruvec: LRU vector to check
1728 1729 1730 1731
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
1732
static int inactive_anon_is_low(struct lruvec *lruvec)
1733
{
1734 1735 1736 1737 1738 1739 1740
	/*
	 * If we don't have swap space, anonymous page deactivation
	 * is pointless.
	 */
	if (!total_swap_pages)
		return 0;

1741
	if (!mem_cgroup_disabled())
1742
		return mem_cgroup_inactive_anon_is_low(lruvec);
1743

1744
	return inactive_anon_is_low_global(lruvec_zone(lruvec));
1745
}
1746
#else
1747
static inline int inactive_anon_is_low(struct lruvec *lruvec)
1748 1749 1750 1751
{
	return 0;
}
#endif
1752

1753 1754
/**
 * inactive_file_is_low - check if file pages need to be deactivated
1755
 * @lruvec: LRU vector to check
1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766
 *
 * 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.
 */
1767
static int inactive_file_is_low(struct lruvec *lruvec)
1768
{
1769 1770 1771 1772 1773
	unsigned long inactive;
	unsigned long active;

	inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
	active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
1774

1775
	return active > inactive;
1776 1777
}

H
Hugh Dickins 已提交
1778
static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
1779
{
H
Hugh Dickins 已提交
1780
	if (is_file_lru(lru))
1781
		return inactive_file_is_low(lruvec);
1782
	else
1783
		return inactive_anon_is_low(lruvec);
1784 1785
}

1786
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1787
				 struct lruvec *lruvec, struct scan_control *sc)
1788
{
1789
	if (is_active_lru(lru)) {
H
Hugh Dickins 已提交
1790
		if (inactive_list_is_low(lruvec, lru))
1791
			shrink_active_list(nr_to_scan, lruvec, sc, lru);
1792 1793 1794
		return 0;
	}

1795
	return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
1796 1797
}

1798
static int vmscan_swappiness(struct scan_control *sc)
1799
{
1800
	if (global_reclaim(sc))
1801
		return vm_swappiness;
1802
	return mem_cgroup_swappiness(sc->target_mem_cgroup);
1803 1804
}

1805 1806 1807 1808 1809 1810 1811
enum scan_balance {
	SCAN_EQUAL,
	SCAN_FRACT,
	SCAN_ANON,
	SCAN_FILE,
};

1812 1813 1814 1815 1816 1817
/*
 * 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.
 *
W
Wanpeng Li 已提交
1818 1819
 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1820
 */
1821
static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
1822
			   unsigned long *nr)
1823
{
1824 1825 1826 1827
	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
	u64 fraction[2];
	u64 denominator = 0;	/* gcc */
	struct zone *zone = lruvec_zone(lruvec);
1828
	unsigned long anon_prio, file_prio;
1829 1830 1831
	enum scan_balance scan_balance;
	unsigned long anon, file, free;
	bool force_scan = false;
1832
	unsigned long ap, fp;
H
Hugh Dickins 已提交
1833
	enum lru_list lru;
1834

1835 1836 1837 1838 1839 1840 1841 1842 1843 1844
	/*
	 * 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.
	 */
1845
	if (current_is_kswapd() && !zone_reclaimable(zone))
1846
		force_scan = true;
1847
	if (!global_reclaim(sc))
1848
		force_scan = true;
1849 1850

	/* If we have no swap space, do not bother scanning anon pages. */
1851
	if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
1852
		scan_balance = SCAN_FILE;
1853 1854
		goto out;
	}
1855

1856 1857 1858 1859 1860 1861 1862 1863
	/*
	 * Global reclaim will swap to prevent OOM even with no
	 * swappiness, but memcg users want to use this knob to
	 * disable swapping for individual groups completely when
	 * using the memory controller's swap limit feature would be
	 * too expensive.
	 */
	if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {
1864
		scan_balance = SCAN_FILE;
1865 1866 1867 1868 1869 1870 1871 1872 1873
		goto out;
	}

	/*
	 * Do not apply any pressure balancing cleverness when the
	 * system is close to OOM, scan both anon and file equally
	 * (unless the swappiness setting disagrees with swapping).
	 */
	if (!sc->priority && vmscan_swappiness(sc)) {
1874
		scan_balance = SCAN_EQUAL;
1875 1876 1877
		goto out;
	}

1878 1879 1880 1881
	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
		get_lru_size(lruvec, LRU_INACTIVE_ANON);
	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
		get_lru_size(lruvec, LRU_INACTIVE_FILE);
1882

1883 1884 1885 1886 1887 1888
	/*
	 * If it's foreseeable that reclaiming the file cache won't be
	 * enough to get the zone back into a desirable shape, we have
	 * to swap.  Better start now and leave the - probably heavily
	 * thrashing - remaining file pages alone.
	 */
1889
	if (global_reclaim(sc)) {
1890
		free = zone_page_state(zone, NR_FREE_PAGES);
1891
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1892
			scan_balance = SCAN_ANON;
1893
			goto out;
1894
		}
1895 1896
	}

1897 1898 1899 1900 1901
	/*
	 * There is enough inactive page cache, do not reclaim
	 * anything from the anonymous working set right now.
	 */
	if (!inactive_file_is_low(lruvec)) {
1902
		scan_balance = SCAN_FILE;
1903 1904 1905
		goto out;
	}

1906 1907
	scan_balance = SCAN_FRACT;

1908 1909 1910 1911
	/*
	 * With swappiness at 100, anonymous and file have the same priority.
	 * This scanning priority is essentially the inverse of IO cost.
	 */
1912
	anon_prio = vmscan_swappiness(sc);
H
Hugh Dickins 已提交
1913
	file_prio = 200 - anon_prio;
1914

1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925
	/*
	 * 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]
	 */
1926
	spin_lock_irq(&zone->lru_lock);
1927 1928 1929
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1930 1931
	}

1932 1933 1934
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1935 1936 1937
	}

	/*
1938 1939 1940
	 * 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.
1941
	 */
1942
	ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
1943
	ap /= reclaim_stat->recent_rotated[0] + 1;
1944

1945
	fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
1946
	fp /= reclaim_stat->recent_rotated[1] + 1;
1947
	spin_unlock_irq(&zone->lru_lock);
1948

1949 1950 1951 1952
	fraction[0] = ap;
	fraction[1] = fp;
	denominator = ap + fp + 1;
out:
H
Hugh Dickins 已提交
1953 1954
	for_each_evictable_lru(lru) {
		int file = is_file_lru(lru);
1955
		unsigned long size;
1956
		unsigned long scan;
1957

1958
		size = get_lru_size(lruvec, lru);
1959
		scan = size >> sc->priority;
1960

1961 1962
		if (!scan && force_scan)
			scan = min(size, SWAP_CLUSTER_MAX);
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984

		switch (scan_balance) {
		case SCAN_EQUAL:
			/* Scan lists relative to size */
			break;
		case SCAN_FRACT:
			/*
			 * Scan types proportional to swappiness and
			 * their relative recent reclaim efficiency.
			 */
			scan = div64_u64(scan * fraction[file], denominator);
			break;
		case SCAN_FILE:
		case SCAN_ANON:
			/* Scan one type exclusively */
			if ((scan_balance == SCAN_FILE) != file)
				scan = 0;
			break;
		default:
			/* Look ma, no brain */
			BUG();
		}
H
Hugh Dickins 已提交
1985
		nr[lru] = scan;
1986
	}
1987
}
1988

1989 1990 1991 1992 1993 1994
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
{
	unsigned long nr[NR_LRU_LISTS];
1995
	unsigned long targets[NR_LRU_LISTS];
1996 1997 1998 1999 2000
	unsigned long nr_to_scan;
	enum lru_list lru;
	unsigned long nr_reclaimed = 0;
	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
	struct blk_plug plug;
2001
	bool scan_adjusted = false;
2002 2003 2004

	get_scan_count(lruvec, sc, nr);

2005 2006 2007
	/* Record the original scan target for proportional adjustments later */
	memcpy(targets, nr, sizeof(nr));

2008 2009 2010
	blk_start_plug(&plug);
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
2011 2012 2013
		unsigned long nr_anon, nr_file, percentage;
		unsigned long nr_scanned;

2014 2015 2016 2017 2018 2019 2020 2021 2022
		for_each_evictable_lru(lru) {
			if (nr[lru]) {
				nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
				nr[lru] -= nr_to_scan;

				nr_reclaimed += shrink_list(lru, nr_to_scan,
							    lruvec, sc);
			}
		}
2023 2024 2025 2026

		if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
			continue;

2027
		/*
2028 2029 2030 2031
		 * For global direct reclaim, reclaim only the number of pages
		 * requested. Less care is taken to scan proportionally as it
		 * is more important to minimise direct reclaim stall latency
		 * than it is to properly age the LRU lists.
2032
		 */
2033
		if (global_reclaim(sc) && !current_is_kswapd())
2034
			break;
2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076

		/*
		 * For kswapd and memcg, reclaim at least the number of pages
		 * requested. Ensure that the anon and file LRUs shrink
		 * proportionally what was requested by get_scan_count(). We
		 * stop reclaiming one LRU and reduce the amount scanning
		 * proportional to the original scan target.
		 */
		nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
		nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];

		if (nr_file > nr_anon) {
			unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
						targets[LRU_ACTIVE_ANON] + 1;
			lru = LRU_BASE;
			percentage = nr_anon * 100 / scan_target;
		} else {
			unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
						targets[LRU_ACTIVE_FILE] + 1;
			lru = LRU_FILE;
			percentage = nr_file * 100 / scan_target;
		}

		/* Stop scanning the smaller of the LRU */
		nr[lru] = 0;
		nr[lru + LRU_ACTIVE] = 0;

		/*
		 * Recalculate the other LRU scan count based on its original
		 * scan target and the percentage scanning already complete
		 */
		lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
		nr_scanned = targets[lru] - nr[lru];
		nr[lru] = targets[lru] * (100 - percentage) / 100;
		nr[lru] -= min(nr[lru], nr_scanned);

		lru += LRU_ACTIVE;
		nr_scanned = targets[lru] - nr[lru];
		nr[lru] = targets[lru] * (100 - percentage) / 100;
		nr[lru] -= min(nr[lru], nr_scanned);

		scan_adjusted = true;
2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091
	}
	blk_finish_plug(&plug);
	sc->nr_reclaimed += nr_reclaimed;

	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
	if (inactive_anon_is_low(lruvec))
		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
				   sc, LRU_ACTIVE_ANON);

	throttle_vm_writeout(sc->gfp_mask);
}

M
Mel Gorman 已提交
2092
/* Use reclaim/compaction for costly allocs or under memory pressure */
2093
static bool in_reclaim_compaction(struct scan_control *sc)
M
Mel Gorman 已提交
2094
{
2095
	if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
M
Mel Gorman 已提交
2096
			(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
2097
			 sc->priority < DEF_PRIORITY - 2))
M
Mel Gorman 已提交
2098 2099 2100 2101 2102
		return true;

	return false;
}

2103
/*
M
Mel Gorman 已提交
2104 2105 2106 2107 2108
 * Reclaim/compaction is used for high-order allocation requests. It reclaims
 * order-0 pages before compacting the zone. should_continue_reclaim() returns
 * true if more pages should be reclaimed such that when the page allocator
 * calls try_to_compact_zone() that it will have enough free pages to succeed.
 * It will give up earlier than that if there is difficulty reclaiming pages.
2109
 */
2110
static inline bool should_continue_reclaim(struct zone *zone,
2111 2112 2113 2114 2115 2116 2117 2118
					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 */
2119
	if (!in_reclaim_compaction(sc))
2120 2121
		return false;

2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143
	/* 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;
	}
2144 2145 2146 2147 2148 2149

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = (2UL << sc->order);
2150
	inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
2151
	if (get_nr_swap_pages() > 0)
2152
		inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
2153 2154 2155 2156 2157
	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 */
2158
	switch (compaction_suitable(zone, sc->order)) {
2159 2160 2161 2162 2163 2164 2165 2166
	case COMPACT_PARTIAL:
	case COMPACT_CONTINUE:
		return false;
	default:
		return true;
	}
}

2167
static void shrink_zone(struct zone *zone, struct scan_control *sc)
L
Linus Torvalds 已提交
2168
{
2169
	unsigned long nr_reclaimed, nr_scanned;
L
Linus Torvalds 已提交
2170

2171 2172 2173 2174 2175 2176
	do {
		struct mem_cgroup *root = sc->target_mem_cgroup;
		struct mem_cgroup_reclaim_cookie reclaim = {
			.zone = zone,
			.priority = sc->priority,
		};
2177
		struct mem_cgroup *memcg;
2178

2179 2180
		nr_reclaimed = sc->nr_reclaimed;
		nr_scanned = sc->nr_scanned;
L
Linus Torvalds 已提交
2181

2182 2183
		memcg = mem_cgroup_iter(root, NULL, &reclaim);
		do {
2184
			struct lruvec *lruvec;
2185

2186
			lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2187

2188
			shrink_lruvec(lruvec, sc);
2189

2190
			/*
2191 2192
			 * Direct reclaim and kswapd have to scan all memory
			 * cgroups to fulfill the overall scan target for the
2193
			 * zone.
2194 2195 2196 2197 2198
			 *
			 * Limit reclaim, on the other hand, only cares about
			 * nr_to_reclaim pages to be reclaimed and it will
			 * retry with decreasing priority if one round over the
			 * whole hierarchy is not sufficient.
2199
			 */
2200 2201
			if (!global_reclaim(sc) &&
					sc->nr_reclaimed >= sc->nr_to_reclaim) {
2202 2203 2204
				mem_cgroup_iter_break(root, memcg);
				break;
			}
2205 2206
			memcg = mem_cgroup_iter(root, memcg, &reclaim);
		} while (memcg);
2207 2208 2209 2210 2211

		vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
			   sc->nr_scanned - nr_scanned,
			   sc->nr_reclaimed - nr_reclaimed);

2212 2213
	} while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
					 sc->nr_scanned - nr_scanned, sc));
2214 2215
}

2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232
/* Returns true if compaction should go ahead for a high-order request */
static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
{
	unsigned long balance_gap, watermark;
	bool watermark_ok;

	/* Do not consider compaction for orders reclaim is meant to satisfy */
	if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
		return false;

	/*
	 * Compaction takes time to run and there are potentially other
	 * callers using the pages just freed. Continue reclaiming until
	 * there is a buffer of free pages available to give compaction
	 * a reasonable chance of completing and allocating the page
	 */
	balance_gap = min(low_wmark_pages(zone),
2233
		(zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2234 2235 2236 2237 2238 2239 2240 2241
			KSWAPD_ZONE_BALANCE_GAP_RATIO);
	watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
	watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);

	/*
	 * If compaction is deferred, reclaim up to a point where
	 * compaction will have a chance of success when re-enabled
	 */
2242
	if (compaction_deferred(zone, sc->order))
2243 2244 2245 2246 2247 2248 2249 2250 2251
		return watermark_ok;

	/* If compaction is not ready to start, keep reclaiming */
	if (!compaction_suitable(zone, sc->order))
		return false;

	return watermark_ok;
}

L
Linus Torvalds 已提交
2252 2253 2254 2255 2256
/*
 * 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.
 *
2257 2258
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
2259 2260
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
2261 2262 2263
 * 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
2264 2265 2266
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
2267 2268
 *
 * This function returns true if a zone is being reclaimed for a costly
2269
 * high-order allocation and compaction is ready to begin. This indicates to
2270 2271
 * the caller that it should consider retrying the allocation instead of
 * further reclaim.
L
Linus Torvalds 已提交
2272
 */
2273
static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
L
Linus Torvalds 已提交
2274
{
2275
	struct zoneref *z;
2276
	struct zone *zone;
2277 2278
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2279
	bool aborted_reclaim = false;
2280

2281 2282 2283 2284 2285 2286 2287 2288
	/*
	 * If the number of buffer_heads in the machine exceeds the maximum
	 * allowed level, force direct reclaim to scan the highmem zone as
	 * highmem pages could be pinning lowmem pages storing buffer_heads
	 */
	if (buffer_heads_over_limit)
		sc->gfp_mask |= __GFP_HIGHMEM;

2289 2290
	for_each_zone_zonelist_nodemask(zone, z, zonelist,
					gfp_zone(sc->gfp_mask), sc->nodemask) {
2291
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
2292
			continue;
2293 2294 2295 2296
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
2297
		if (global_reclaim(sc)) {
2298 2299
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
2300 2301
			if (sc->priority != DEF_PRIORITY &&
			    !zone_reclaimable(zone))
2302
				continue;	/* Let kswapd poll it */
2303
			if (IS_ENABLED(CONFIG_COMPACTION)) {
2304
				/*
2305 2306 2307 2308 2309
				 * 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
2310 2311
				 * noticeable problem, like transparent huge
				 * page allocations.
2312
				 */
2313
				if (compaction_ready(zone, sc)) {
2314
					aborted_reclaim = true;
2315
					continue;
2316
				}
2317
			}
2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329
			/*
			 * 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;
2330
			/* need some check for avoid more shrink_zone() */
2331
		}
2332

2333
		shrink_zone(zone, sc);
L
Linus Torvalds 已提交
2334
	}
2335

2336
	return aborted_reclaim;
2337 2338
}

2339
/* All zones in zonelist are unreclaimable? */
2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351
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;
2352
		if (zone_reclaimable(zone))
2353
			return false;
2354 2355
	}

2356
	return true;
L
Linus Torvalds 已提交
2357
}
2358

L
Linus Torvalds 已提交
2359 2360 2361 2362 2363 2364 2365 2366
/*
 * 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
2367 2368 2369 2370
 * 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.
2371 2372 2373
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
2374
 */
2375
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2376 2377
					struct scan_control *sc,
					struct shrink_control *shrink)
L
Linus Torvalds 已提交
2378
{
2379
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
2380
	struct reclaim_state *reclaim_state = current->reclaim_state;
2381
	struct zoneref *z;
2382
	struct zone *zone;
2383
	unsigned long writeback_threshold;
2384
	bool aborted_reclaim;
L
Linus Torvalds 已提交
2385

2386 2387
	delayacct_freepages_start();

2388
	if (global_reclaim(sc))
2389
		count_vm_event(ALLOCSTALL);
L
Linus Torvalds 已提交
2390

2391
	do {
2392 2393
		vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
				sc->priority);
2394
		sc->nr_scanned = 0;
2395
		aborted_reclaim = shrink_zones(zonelist, sc);
2396

2397
		/*
2398 2399 2400 2401
		 * Don't shrink slabs when reclaiming memory from over limit
		 * cgroups but do shrink slab at least once when aborting
		 * reclaim for compaction to avoid unevenly scanning file/anon
		 * LRU pages over slab pages.
2402
		 */
2403
		if (global_reclaim(sc)) {
2404
			unsigned long lru_pages = 0;
D
Dave Chinner 已提交
2405 2406

			nodes_clear(shrink->nodes_to_scan);
2407 2408
			for_each_zone_zonelist(zone, z, zonelist,
					gfp_zone(sc->gfp_mask)) {
2409 2410 2411 2412
				if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
					continue;

				lru_pages += zone_reclaimable_pages(zone);
D
Dave Chinner 已提交
2413 2414
				node_set(zone_to_nid(zone),
					 shrink->nodes_to_scan);
2415 2416
			}

2417
			shrink_slab(shrink, sc->nr_scanned, lru_pages);
2418
			if (reclaim_state) {
2419
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2420 2421
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
2422
		}
2423
		total_scanned += sc->nr_scanned;
2424
		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
L
Linus Torvalds 已提交
2425 2426
			goto out;

2427 2428 2429 2430 2431 2432 2433
		/*
		 * If we're getting trouble reclaiming, start doing
		 * writepage even in laptop mode.
		 */
		if (sc->priority < DEF_PRIORITY - 2)
			sc->may_writepage = 1;

L
Linus Torvalds 已提交
2434 2435 2436 2437 2438 2439 2440
		/*
		 * 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.
		 */
2441 2442
		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
		if (total_scanned > writeback_threshold) {
2443 2444
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
						WB_REASON_TRY_TO_FREE_PAGES);
2445
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
2446
		}
2447
	} while (--sc->priority >= 0 && !aborted_reclaim);
2448

L
Linus Torvalds 已提交
2449
out:
2450 2451
	delayacct_freepages_end();

2452 2453 2454
	if (sc->nr_reclaimed)
		return sc->nr_reclaimed;

2455 2456 2457 2458 2459 2460 2461 2462
	/*
	 * 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;

2463 2464
	/* Aborted reclaim to try compaction? don't OOM, then */
	if (aborted_reclaim)
2465 2466
		return 1;

2467
	/* top priority shrink_zones still had more to do? don't OOM, then */
2468
	if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2469 2470 2471
		return 1;

	return 0;
L
Linus Torvalds 已提交
2472 2473
}

2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503
static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
{
	struct zone *zone;
	unsigned long pfmemalloc_reserve = 0;
	unsigned long free_pages = 0;
	int i;
	bool wmark_ok;

	for (i = 0; i <= ZONE_NORMAL; i++) {
		zone = &pgdat->node_zones[i];
		pfmemalloc_reserve += min_wmark_pages(zone);
		free_pages += zone_page_state(zone, NR_FREE_PAGES);
	}

	wmark_ok = free_pages > pfmemalloc_reserve / 2;

	/* kswapd must be awake if processes are being throttled */
	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
		pgdat->classzone_idx = min(pgdat->classzone_idx,
						(enum zone_type)ZONE_NORMAL);
		wake_up_interruptible(&pgdat->kswapd_wait);
	}

	return wmark_ok;
}

/*
 * Throttle direct reclaimers if backing storage is backed by the network
 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
 * depleted. kswapd will continue to make progress and wake the processes
2504 2505 2506 2507
 * when the low watermark is reached.
 *
 * Returns true if a fatal signal was delivered during throttling. If this
 * happens, the page allocator should not consider triggering the OOM killer.
2508
 */
2509
static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523
					nodemask_t *nodemask)
{
	struct zone *zone;
	int high_zoneidx = gfp_zone(gfp_mask);
	pg_data_t *pgdat;

	/*
	 * Kernel threads should not be throttled as they may be indirectly
	 * responsible for cleaning pages necessary for reclaim to make forward
	 * progress. kjournald for example may enter direct reclaim while
	 * committing a transaction where throttling it could forcing other
	 * processes to block on log_wait_commit().
	 */
	if (current->flags & PF_KTHREAD)
2524 2525 2526 2527 2528 2529 2530 2531
		goto out;

	/*
	 * If a fatal signal is pending, this process should not throttle.
	 * It should return quickly so it can exit and free its memory
	 */
	if (fatal_signal_pending(current))
		goto out;
2532 2533 2534 2535 2536

	/* Check if the pfmemalloc reserves are ok */
	first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone);
	pgdat = zone->zone_pgdat;
	if (pfmemalloc_watermark_ok(pgdat))
2537
		goto out;
2538

2539 2540 2541
	/* Account for the throttling */
	count_vm_event(PGSCAN_DIRECT_THROTTLE);

2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552
	/*
	 * If the caller cannot enter the filesystem, it's possible that it
	 * is due to the caller holding an FS lock or performing a journal
	 * transaction in the case of a filesystem like ext[3|4]. In this case,
	 * it is not safe to block on pfmemalloc_wait as kswapd could be
	 * blocked waiting on the same lock. Instead, throttle for up to a
	 * second before continuing.
	 */
	if (!(gfp_mask & __GFP_FS)) {
		wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
			pfmemalloc_watermark_ok(pgdat), HZ);
2553 2554

		goto check_pending;
2555 2556 2557 2558 2559
	}

	/* Throttle until kswapd wakes the process */
	wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
		pfmemalloc_watermark_ok(pgdat));
2560 2561 2562 2563 2564 2565 2566

check_pending:
	if (fatal_signal_pending(current))
		return true;

out:
	return false;
2567 2568
}

2569
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2570
				gfp_t gfp_mask, nodemask_t *nodemask)
2571
{
2572
	unsigned long nr_reclaimed;
2573
	struct scan_control sc = {
2574
		.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
2575
		.may_writepage = !laptop_mode,
2576
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2577
		.may_unmap = 1,
2578
		.may_swap = 1,
2579
		.order = order,
2580
		.priority = DEF_PRIORITY,
2581
		.target_mem_cgroup = NULL,
2582
		.nodemask = nodemask,
2583
	};
2584 2585 2586
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
2587

2588
	/*
2589 2590 2591
	 * Do not enter reclaim if fatal signal was delivered while throttled.
	 * 1 is returned so that the page allocator does not OOM kill at this
	 * point.
2592
	 */
2593
	if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
2594 2595
		return 1;

2596 2597 2598 2599
	trace_mm_vmscan_direct_reclaim_begin(order,
				sc.may_writepage,
				gfp_mask);

2600
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2601 2602 2603 2604

	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2605 2606
}

A
Andrew Morton 已提交
2607
#ifdef CONFIG_MEMCG
2608

2609
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2610
						gfp_t gfp_mask, bool noswap,
2611 2612
						struct zone *zone,
						unsigned long *nr_scanned)
2613 2614
{
	struct scan_control sc = {
2615
		.nr_scanned = 0,
2616
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2617 2618 2619 2620
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.order = 0,
2621
		.priority = 0,
2622
		.target_mem_cgroup = memcg,
2623
	};
2624
	struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2625

2626 2627
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2628

2629
	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
2630 2631 2632
						      sc.may_writepage,
						      sc.gfp_mask);

2633 2634 2635 2636 2637 2638 2639
	/*
	 * 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.
	 */
2640
	shrink_lruvec(lruvec, &sc);
2641 2642 2643

	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);

2644
	*nr_scanned = sc.nr_scanned;
2645 2646 2647
	return sc.nr_reclaimed;
}

2648
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
K
KOSAKI Motohiro 已提交
2649
					   gfp_t gfp_mask,
2650
					   bool noswap)
2651
{
2652
	struct zonelist *zonelist;
2653
	unsigned long nr_reclaimed;
2654
	int nid;
2655 2656
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
2657
		.may_unmap = 1,
2658
		.may_swap = !noswap,
2659
		.nr_to_reclaim = SWAP_CLUSTER_MAX,
2660
		.order = 0,
2661
		.priority = DEF_PRIORITY,
2662
		.target_mem_cgroup = memcg,
2663
		.nodemask = NULL, /* we don't care the placement */
2664 2665 2666 2667 2668
		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
	};
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
2669 2670
	};

2671 2672 2673 2674 2675
	/*
	 * 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.
	 */
2676
	nid = mem_cgroup_select_victim_node(memcg);
2677 2678

	zonelist = NODE_DATA(nid)->node_zonelists;
2679 2680 2681 2682 2683

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

2684
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2685 2686 2687 2688

	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);

	return nr_reclaimed;
2689 2690 2691
}
#endif

2692
static void age_active_anon(struct zone *zone, struct scan_control *sc)
2693
{
2694
	struct mem_cgroup *memcg;
2695

2696 2697 2698 2699 2700
	if (!total_swap_pages)
		return;

	memcg = mem_cgroup_iter(NULL, NULL, NULL);
	do {
2701
		struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2702

2703
		if (inactive_anon_is_low(lruvec))
2704
			shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2705
					   sc, LRU_ACTIVE_ANON);
2706 2707 2708

		memcg = mem_cgroup_iter(NULL, memcg, NULL);
	} while (memcg);
2709 2710
}

2711 2712 2713 2714 2715 2716 2717
static bool zone_balanced(struct zone *zone, int order,
			  unsigned long balance_gap, int classzone_idx)
{
	if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
				    balance_gap, classzone_idx, 0))
		return false;

2718 2719
	if (IS_ENABLED(CONFIG_COMPACTION) && order &&
	    !compaction_suitable(zone, order))
2720 2721 2722 2723 2724
		return false;

	return true;
}

2725
/*
2726 2727 2728 2729 2730 2731 2732 2733 2734 2735
 * pgdat_balanced() is used when checking if a node is balanced.
 *
 * For order-0, all zones must be 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.
2736 2737 2738 2739
 * 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
2740
 *     percentage of the middle zones. For example, on 32-bit x86, highmem
2741 2742 2743 2744
 *     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.
 */
2745
static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
2746
{
2747
	unsigned long managed_pages = 0;
2748
	unsigned long balanced_pages = 0;
2749 2750
	int i;

2751 2752 2753
	/* Check the watermark levels */
	for (i = 0; i <= classzone_idx; i++) {
		struct zone *zone = pgdat->node_zones + i;
2754

2755 2756 2757
		if (!populated_zone(zone))
			continue;

2758
		managed_pages += zone->managed_pages;
2759 2760 2761 2762 2763 2764 2765 2766

		/*
		 * A special case here:
		 *
		 * balance_pgdat() skips over all_unreclaimable after
		 * DEF_PRIORITY. Effectively, it considers them balanced so
		 * they must be considered balanced here as well!
		 */
2767
		if (!zone_reclaimable(zone)) {
2768
			balanced_pages += zone->managed_pages;
2769 2770 2771 2772
			continue;
		}

		if (zone_balanced(zone, order, 0, i))
2773
			balanced_pages += zone->managed_pages;
2774 2775 2776 2777 2778
		else if (!order)
			return false;
	}

	if (order)
2779
		return balanced_pages >= (managed_pages >> 2);
2780 2781
	else
		return true;
2782 2783
}

2784 2785 2786 2787 2788 2789 2790
/*
 * Prepare kswapd for sleeping. This verifies that there are no processes
 * waiting in throttle_direct_reclaim() and that watermarks have been met.
 *
 * Returns true if kswapd is ready to sleep
 */
static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
2791
					int classzone_idx)
2792 2793 2794
{
	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
	if (remaining)
2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809
		return false;

	/*
	 * There is a potential race between when kswapd checks its watermarks
	 * and a process gets throttled. There is also a potential race if
	 * processes get throttled, kswapd wakes, a large process exits therby
	 * balancing the zones that causes kswapd to miss a wakeup. If kswapd
	 * is going to sleep, no process should be sleeping on pfmemalloc_wait
	 * so wake them now if necessary. If necessary, processes will wake
	 * kswapd and get throttled again
	 */
	if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
		wake_up(&pgdat->pfmemalloc_wait);
		return false;
	}
2810

2811
	return pgdat_balanced(pgdat, order, classzone_idx);
2812 2813
}

2814 2815 2816
/*
 * kswapd shrinks the zone by the number of pages required to reach
 * the high watermark.
2817 2818
 *
 * Returns true if kswapd scanned at least the requested number of pages to
2819 2820
 * reclaim or if the lack of progress was due to pages under writeback.
 * This is used to determine if the scanning priority needs to be raised.
2821
 */
2822
static bool kswapd_shrink_zone(struct zone *zone,
2823
			       int classzone_idx,
2824
			       struct scan_control *sc,
2825 2826
			       unsigned long lru_pages,
			       unsigned long *nr_attempted)
2827
{
2828 2829
	int testorder = sc->order;
	unsigned long balance_gap;
2830 2831 2832 2833
	struct reclaim_state *reclaim_state = current->reclaim_state;
	struct shrink_control shrink = {
		.gfp_mask = sc->gfp_mask,
	};
2834
	bool lowmem_pressure;
2835 2836 2837

	/* Reclaim above the high watermark. */
	sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868

	/*
	 * Kswapd reclaims only single pages with compaction enabled. Trying
	 * too hard to reclaim until contiguous free pages have become
	 * available can hurt performance by evicting too much useful data
	 * from memory. Do not reclaim more than needed for compaction.
	 */
	if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
			compaction_suitable(zone, sc->order) !=
				COMPACT_SKIPPED)
		testorder = 0;

	/*
	 * 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.
	 */
	balance_gap = min(low_wmark_pages(zone),
		(zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
		KSWAPD_ZONE_BALANCE_GAP_RATIO);

	/*
	 * If there is no low memory pressure or the zone is balanced then no
	 * reclaim is necessary
	 */
	lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
	if (!lowmem_pressure && zone_balanced(zone, testorder,
						balance_gap, classzone_idx))
		return true;

2869
	shrink_zone(zone, sc);
D
Dave Chinner 已提交
2870 2871
	nodes_clear(shrink.nodes_to_scan);
	node_set(zone_to_nid(zone), shrink.nodes_to_scan);
2872 2873

	reclaim_state->reclaimed_slab = 0;
2874
	shrink_slab(&shrink, sc->nr_scanned, lru_pages);
2875 2876
	sc->nr_reclaimed += reclaim_state->reclaimed_slab;

2877 2878 2879
	/* Account for the number of pages attempted to reclaim */
	*nr_attempted += sc->nr_to_reclaim;

2880 2881
	zone_clear_flag(zone, ZONE_WRITEBACK);

2882 2883 2884 2885 2886 2887
	/*
	 * 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, speculatively avoid congestion
	 * waits.
	 */
2888
	if (zone_reclaimable(zone) &&
2889 2890 2891 2892 2893
	    zone_balanced(zone, testorder, 0, classzone_idx)) {
		zone_clear_flag(zone, ZONE_CONGESTED);
		zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
	}

2894
	return sc->nr_scanned >= sc->nr_to_reclaim;
2895 2896
}

L
Linus Torvalds 已提交
2897 2898
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
2899
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
2900
 *
2901
 * Returns the final order kswapd was reclaiming at
L
Linus Torvalds 已提交
2902 2903 2904 2905 2906 2907 2908 2909 2910 2911
 *
 * 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
2912 2913 2914 2915 2916
 * 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
2917
 */
2918
static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2919
							int *classzone_idx)
L
Linus Torvalds 已提交
2920 2921
{
	int i;
2922
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
2923 2924
	unsigned long nr_soft_reclaimed;
	unsigned long nr_soft_scanned;
2925 2926
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2927
		.priority = DEF_PRIORITY,
2928
		.may_unmap = 1,
2929
		.may_swap = 1,
2930
		.may_writepage = !laptop_mode,
A
Andy Whitcroft 已提交
2931
		.order = order,
2932
		.target_mem_cgroup = NULL,
2933
	};
2934
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
2935

2936
	do {
L
Linus Torvalds 已提交
2937
		unsigned long lru_pages = 0;
2938
		unsigned long nr_attempted = 0;
2939
		bool raise_priority = true;
2940
		bool pgdat_needs_compaction = (order > 0);
2941 2942

		sc.nr_reclaimed = 0;
L
Linus Torvalds 已提交
2943

2944 2945 2946 2947 2948 2949
		/*
		 * 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
2950

2951 2952
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
2953

2954 2955
			if (sc.priority != DEF_PRIORITY &&
			    !zone_reclaimable(zone))
2956
				continue;
L
Linus Torvalds 已提交
2957

2958 2959 2960 2961
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
2962
			age_active_anon(zone, &sc);
2963

2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974
			/*
			 * If the number of buffer_heads in the machine
			 * exceeds the maximum allowed level and this node
			 * has a highmem zone, force kswapd to reclaim from
			 * it to relieve lowmem pressure.
			 */
			if (buffer_heads_over_limit && is_highmem_idx(i)) {
				end_zone = i;
				break;
			}

2975
			if (!zone_balanced(zone, order, 0, 0)) {
2976
				end_zone = i;
A
Andrew Morton 已提交
2977
				break;
2978
			} else {
2979 2980 2981 2982
				/*
				 * If balanced, clear the dirty and congested
				 * flags
				 */
2983
				zone_clear_flag(zone, ZONE_CONGESTED);
2984
				zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
L
Linus Torvalds 已提交
2985 2986
			}
		}
2987

2988
		if (i < 0)
A
Andrew Morton 已提交
2989 2990
			goto out;

L
Linus Torvalds 已提交
2991 2992 2993
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

2994 2995 2996
			if (!populated_zone(zone))
				continue;

2997
			lru_pages += zone_reclaimable_pages(zone);
2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008

			/*
			 * If any zone is currently balanced then kswapd will
			 * not call compaction as it is expected that the
			 * necessary pages are already available.
			 */
			if (pgdat_needs_compaction &&
					zone_watermark_ok(zone, order,
						low_wmark_pages(zone),
						*classzone_idx, 0))
				pgdat_needs_compaction = false;
L
Linus Torvalds 已提交
3009 3010
		}

3011 3012 3013 3014 3015 3016 3017
		/*
		 * If we're getting trouble reclaiming, start doing writepage
		 * even in laptop mode.
		 */
		if (sc.priority < DEF_PRIORITY - 2)
			sc.may_writepage = 1;

L
Linus Torvalds 已提交
3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029
		/*
		 * 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;

3030
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
3031 3032
				continue;

3033 3034
			if (sc.priority != DEF_PRIORITY &&
			    !zone_reclaimable(zone))
L
Linus Torvalds 已提交
3035 3036 3037
				continue;

			sc.nr_scanned = 0;
3038

3039 3040 3041 3042 3043 3044 3045 3046 3047
			nr_soft_scanned = 0;
			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 */
			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
							order, sc.gfp_mask,
							&nr_soft_scanned);
			sc.nr_reclaimed += nr_soft_reclaimed;

3048
			/*
3049 3050 3051 3052
			 * There should be no need to raise the scanning
			 * priority if enough pages are already being scanned
			 * that that high watermark would be met at 100%
			 * efficiency.
3053
			 */
3054 3055 3056
			if (kswapd_shrink_zone(zone, end_zone, &sc,
					lru_pages, &nr_attempted))
				raise_priority = false;
L
Linus Torvalds 已提交
3057
		}
3058 3059 3060 3061 3062 3063 3064 3065 3066 3067

		/*
		 * If the low watermark is met there is no need for processes
		 * to be throttled on pfmemalloc_wait as they should not be
		 * able to safely make forward progress. Wake them
		 */
		if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
				pfmemalloc_watermark_ok(pgdat))
			wake_up(&pgdat->pfmemalloc_wait);

L
Linus Torvalds 已提交
3068
		/*
3069 3070 3071 3072 3073 3074
		 * Fragmentation may mean that the system cannot be rebalanced
		 * for high-order allocations in all zones. If twice the
		 * allocation size has been reclaimed and the zones are still
		 * not balanced then recheck the watermarks at order-0 to
		 * prevent kswapd reclaiming excessively. Assume that a
		 * process requested a high-order can direct reclaim/compact.
L
Linus Torvalds 已提交
3075
		 */
3076 3077
		if (order && sc.nr_reclaimed >= 2UL << order)
			order = sc.order = 0;
3078

3079 3080 3081
		/* Check if kswapd should be suspending */
		if (try_to_freeze() || kthread_should_stop())
			break;
3082

3083 3084 3085 3086 3087 3088 3089
		/*
		 * Compact if necessary and kswapd is reclaiming at least the
		 * high watermark number of pages as requsted
		 */
		if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
			compact_pgdat(pgdat, order);

3090
		/*
3091 3092
		 * Raise priority if scanning rate is too low or there was no
		 * progress in reclaiming pages
3093
		 */
3094 3095
		if (raise_priority || !sc.nr_reclaimed)
			sc.priority--;
3096
	} while (sc.priority >= 1 &&
3097
		 !pgdat_balanced(pgdat, order, *classzone_idx));
L
Linus Torvalds 已提交
3098

3099
out:
3100
	/*
3101
	 * Return the order we were reclaiming at so prepare_kswapd_sleep()
3102 3103 3104 3105
	 * 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
	 */
3106
	*classzone_idx = end_zone;
3107
	return order;
L
Linus Torvalds 已提交
3108 3109
}

3110
static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
3111 3112 3113 3114 3115 3116 3117 3118 3119 3120
{
	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 */
3121
	if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3122 3123 3124 3125 3126 3127 3128 3129 3130
		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.
	 */
3131
	if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142
		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);
3143

3144 3145 3146 3147 3148 3149 3150 3151
		/*
		 * Compaction records what page blocks it recently failed to
		 * isolate pages from and skips them in the future scanning.
		 * When kswapd is going to sleep, it is reasonable to assume
		 * that pages and compaction may succeed so reset the cache.
		 */
		reset_isolation_suitable(pgdat);

3152 3153 3154
		if (!kthread_should_stop())
			schedule();

3155 3156 3157 3158 3159 3160 3161 3162 3163 3164
		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
3165 3166
/*
 * The background pageout daemon, started as a kernel thread
3167
 * from the init process.
L
Linus Torvalds 已提交
3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179
 *
 * 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)
{
3180
	unsigned long order, new_order;
3181
	unsigned balanced_order;
3182
	int classzone_idx, new_classzone_idx;
3183
	int balanced_classzone_idx;
L
Linus Torvalds 已提交
3184 3185
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
3186

L
Linus Torvalds 已提交
3187 3188 3189
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
3190
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
3191

3192 3193
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
3194
	if (!cpumask_empty(cpumask))
3195
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209
	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).
	 */
3210
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
3211
	set_freezable();
L
Linus Torvalds 已提交
3212

3213
	order = new_order = 0;
3214
	balanced_order = 0;
3215
	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
3216
	balanced_classzone_idx = classzone_idx;
L
Linus Torvalds 已提交
3217
	for ( ; ; ) {
3218
		bool ret;
3219

3220 3221 3222 3223 3224
		/*
		 * 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
		 */
3225 3226
		if (balanced_classzone_idx >= new_classzone_idx &&
					balanced_order == new_order) {
3227 3228 3229 3230 3231 3232
			new_order = pgdat->kswapd_max_order;
			new_classzone_idx = pgdat->classzone_idx;
			pgdat->kswapd_max_order =  0;
			pgdat->classzone_idx = pgdat->nr_zones - 1;
		}

3233
		if (order < new_order || classzone_idx > new_classzone_idx) {
L
Linus Torvalds 已提交
3234 3235
			/*
			 * Don't sleep if someone wants a larger 'order'
3236
			 * allocation or has tigher zone constraints
L
Linus Torvalds 已提交
3237 3238
			 */
			order = new_order;
3239
			classzone_idx = new_classzone_idx;
L
Linus Torvalds 已提交
3240
		} else {
3241 3242
			kswapd_try_to_sleep(pgdat, balanced_order,
						balanced_classzone_idx);
L
Linus Torvalds 已提交
3243
			order = pgdat->kswapd_max_order;
3244
			classzone_idx = pgdat->classzone_idx;
3245 3246
			new_order = order;
			new_classzone_idx = classzone_idx;
3247
			pgdat->kswapd_max_order = 0;
3248
			pgdat->classzone_idx = pgdat->nr_zones - 1;
L
Linus Torvalds 已提交
3249 3250
		}

3251 3252 3253 3254 3255 3256 3257 3258
		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
		 */
3259 3260
		if (!ret) {
			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
3261 3262 3263
			balanced_classzone_idx = classzone_idx;
			balanced_order = balance_pgdat(pgdat, order,
						&balanced_classzone_idx);
3264
		}
L
Linus Torvalds 已提交
3265
	}
3266 3267

	current->reclaim_state = NULL;
L
Linus Torvalds 已提交
3268 3269 3270 3271 3272 3273
	return 0;
}

/*
 * A zone is low on free memory, so wake its kswapd task to service it.
 */
3274
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
L
Linus Torvalds 已提交
3275 3276 3277
{
	pg_data_t *pgdat;

3278
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
3279 3280
		return;

3281
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
3282
		return;
3283
	pgdat = zone->zone_pgdat;
3284
	if (pgdat->kswapd_max_order < order) {
L
Linus Torvalds 已提交
3285
		pgdat->kswapd_max_order = order;
3286 3287
		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
	}
3288
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
3289
		return;
3290
	if (zone_balanced(zone, order, 0, 0))
3291 3292 3293
		return;

	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3294
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
3295 3296
}

3297 3298 3299 3300 3301 3302 3303 3304
/*
 * 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)
3305
{
3306 3307 3308 3309 3310
	int nr;

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

3311
	if (get_nr_swap_pages() > 0)
3312 3313 3314 3315 3316 3317
		nr += global_page_state(NR_ACTIVE_ANON) +
		      global_page_state(NR_INACTIVE_ANON);

	return nr;
}

3318
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
3319
/*
3320
 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3321 3322 3323 3324 3325
 * 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
3326
 */
3327
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
L
Linus Torvalds 已提交
3328
{
3329 3330
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
3331 3332 3333
		.gfp_mask = GFP_HIGHUSER_MOVABLE,
		.may_swap = 1,
		.may_unmap = 1,
3334
		.may_writepage = 1,
3335 3336 3337
		.nr_to_reclaim = nr_to_reclaim,
		.hibernation_mode = 1,
		.order = 0,
3338
		.priority = DEF_PRIORITY,
L
Linus Torvalds 已提交
3339
	};
3340 3341 3342 3343
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3344 3345
	struct task_struct *p = current;
	unsigned long nr_reclaimed;
L
Linus Torvalds 已提交
3346

3347 3348 3349 3350
	p->flags |= PF_MEMALLOC;
	lockdep_set_current_reclaim_state(sc.gfp_mask);
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3351

3352
	nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3353

3354 3355 3356
	p->reclaim_state = NULL;
	lockdep_clear_current_reclaim_state();
	p->flags &= ~PF_MEMALLOC;
3357

3358
	return nr_reclaimed;
L
Linus Torvalds 已提交
3359
}
3360
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
3361 3362 3363 3364 3365

/* 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. */
3366 3367
static int cpu_callback(struct notifier_block *nfb, unsigned long action,
			void *hcpu)
L
Linus Torvalds 已提交
3368
{
3369
	int nid;
L
Linus Torvalds 已提交
3370

3371
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3372
		for_each_node_state(nid, N_MEMORY) {
3373
			pg_data_t *pgdat = NODE_DATA(nid);
3374 3375 3376
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
3377

3378
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
3379
				/* One of our CPUs online: restore mask */
3380
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
3381 3382 3383 3384 3385
		}
	}
	return NOTIFY_OK;
}

3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401
/*
 * 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);
3402 3403
		pr_err("Failed to start kswapd on node %d\n", nid);
		ret = PTR_ERR(pgdat->kswapd);
3404
		pgdat->kswapd = NULL;
3405 3406 3407 3408
	}
	return ret;
}

3409
/*
3410 3411
 * Called by memory hotplug when all memory in a node is offlined.  Caller must
 * hold lock_memory_hotplug().
3412 3413 3414 3415 3416
 */
void kswapd_stop(int nid)
{
	struct task_struct *kswapd = NODE_DATA(nid)->kswapd;

3417
	if (kswapd) {
3418
		kthread_stop(kswapd);
3419 3420
		NODE_DATA(nid)->kswapd = NULL;
	}
3421 3422
}

L
Linus Torvalds 已提交
3423 3424
static int __init kswapd_init(void)
{
3425
	int nid;
3426

L
Linus Torvalds 已提交
3427
	swap_setup();
3428
	for_each_node_state(nid, N_MEMORY)
3429
 		kswapd_run(nid);
L
Linus Torvalds 已提交
3430 3431 3432 3433 3434
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
3435 3436 3437 3438 3439 3440 3441 3442 3443 3444

#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;

3445
#define RECLAIM_OFF 0
3446
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
3447 3448 3449
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

3450 3451 3452 3453 3454 3455 3456
/*
 * 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

3457 3458 3459 3460 3461 3462
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

3463 3464 3465 3466 3467 3468
/*
 * 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;

3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510
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;
}

3511 3512 3513
/*
 * Try to free up some pages from this zone through reclaim.
 */
3514
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3515
{
3516
	/* Minimum pages needed in order to stay on node */
3517
	const unsigned long nr_pages = 1 << order;
3518 3519
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
3520 3521
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3522
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3523
		.may_swap = 1,
3524
		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
3525
		.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
3526
		.order = order,
3527
		.priority = ZONE_RECLAIM_PRIORITY,
3528
	};
3529 3530 3531
	struct shrink_control shrink = {
		.gfp_mask = sc.gfp_mask,
	};
3532
	unsigned long nr_slab_pages0, nr_slab_pages1;
3533 3534

	cond_resched();
3535 3536 3537 3538 3539 3540
	/*
	 * 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;
3541
	lockdep_set_current_reclaim_state(gfp_mask);
3542 3543
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
3544

3545
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3546 3547 3548 3549 3550
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		do {
3551 3552
			shrink_zone(zone, &sc);
		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
3553
	}
3554

3555 3556
	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (nr_slab_pages0 > zone->min_slab_pages) {
3557
		/*
3558
		 * shrink_slab() does not currently allow us to determine how
3559 3560 3561 3562
		 * 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.
3563
		 */
D
Dave Chinner 已提交
3564 3565
		nodes_clear(shrink.nodes_to_scan);
		node_set(zone_to_nid(zone), shrink.nodes_to_scan);
3566 3567 3568 3569
		for (;;) {
			unsigned long lru_pages = zone_reclaimable_pages(zone);

			/* No reclaimable slab or very low memory pressure */
3570
			if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3571 3572 3573 3574 3575 3576 3577 3578
				break;

			/* Freed enough memory */
			nr_slab_pages1 = zone_page_state(zone,
							NR_SLAB_RECLAIMABLE);
			if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
				break;
		}
3579 3580 3581 3582 3583

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
3584 3585 3586
		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;
3587 3588
	}

3589
	p->reclaim_state = NULL;
3590
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3591
	lockdep_clear_current_reclaim_state();
3592
	return sc.nr_reclaimed >= nr_pages;
3593
}
3594 3595 3596 3597

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
3598
	int ret;
3599 3600

	/*
3601 3602
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
3603
	 *
3604 3605 3606 3607 3608
	 * 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.
3609
	 */
3610 3611
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3612
		return ZONE_RECLAIM_FULL;
3613

3614
	if (!zone_reclaimable(zone))
3615
		return ZONE_RECLAIM_FULL;
3616

3617
	/*
3618
	 * Do not scan if the allocation should not be delayed.
3619
	 */
3620
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3621
		return ZONE_RECLAIM_NOSCAN;
3622 3623 3624 3625 3626 3627 3628

	/*
	 * 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.
	 */
3629
	node_id = zone_to_nid(zone);
3630
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3631
		return ZONE_RECLAIM_NOSCAN;
3632 3633

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3634 3635
		return ZONE_RECLAIM_NOSCAN;

3636 3637 3638
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

3639 3640 3641
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

3642
	return ret;
3643
}
3644
#endif
L
Lee Schermerhorn 已提交
3645 3646 3647 3648 3649 3650

/*
 * page_evictable - test whether a page is evictable
 * @page: the page to test
 *
 * Test whether page is evictable--i.e., should be placed on active/inactive
3651
 * lists vs unevictable list.
L
Lee Schermerhorn 已提交
3652 3653
 *
 * Reasons page might not be evictable:
3654
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
3655
 * (2) page is part of an mlocked VMA
3656
 *
L
Lee Schermerhorn 已提交
3657
 */
3658
int page_evictable(struct page *page)
L
Lee Schermerhorn 已提交
3659
{
3660
	return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
L
Lee Schermerhorn 已提交
3661
}
3662

3663
#ifdef CONFIG_SHMEM
3664
/**
3665 3666 3667
 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
 * @pages:	array of pages to check
 * @nr_pages:	number of pages to check
3668
 *
3669
 * Checks pages for evictability and moves them to the appropriate lru list.
3670 3671
 *
 * This function is only used for SysV IPC SHM_UNLOCK.
3672
 */
3673
void check_move_unevictable_pages(struct page **pages, int nr_pages)
3674
{
3675
	struct lruvec *lruvec;
3676 3677 3678 3679
	struct zone *zone = NULL;
	int pgscanned = 0;
	int pgrescued = 0;
	int i;
3680

3681 3682 3683
	for (i = 0; i < nr_pages; i++) {
		struct page *page = pages[i];
		struct zone *pagezone;
3684

3685 3686 3687 3688 3689 3690 3691 3692
		pgscanned++;
		pagezone = page_zone(page);
		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
3693
		lruvec = mem_cgroup_page_lruvec(page, zone);
3694

3695 3696
		if (!PageLRU(page) || !PageUnevictable(page))
			continue;
3697

3698
		if (page_evictable(page)) {
3699 3700 3701 3702
			enum lru_list lru = page_lru_base_type(page);

			VM_BUG_ON(PageActive(page));
			ClearPageUnevictable(page);
3703 3704
			del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
			add_page_to_lru_list(page, lruvec, lru);
3705
			pgrescued++;
3706
		}
3707
	}
3708

3709 3710 3711 3712
	if (zone) {
		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
		spin_unlock_irq(&zone->lru_lock);
3713 3714
	}
}
3715
#endif /* CONFIG_SHMEM */
3716

3717
static void warn_scan_unevictable_pages(void)
3718
{
3719
	printk_once(KERN_WARNING
3720
		    "%s: The scan_unevictable_pages sysctl/node-interface has been "
3721
		    "disabled for lack of a legitimate use case.  If you have "
3722 3723
		    "one, please send an email to linux-mm@kvack.org.\n",
		    current->comm);
3724 3725 3726 3727 3728 3729 3730 3731 3732
}

/*
 * 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,
3733
			   void __user *buffer,
3734 3735
			   size_t *length, loff_t *ppos)
{
3736
	warn_scan_unevictable_pages();
3737
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
3738 3739 3740 3741
	scan_unevictable_pages = 0;
	return 0;
}

3742
#ifdef CONFIG_NUMA
3743 3744 3745 3746 3747
/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

3748 3749
static ssize_t read_scan_unevictable_node(struct device *dev,
					  struct device_attribute *attr,
3750 3751
					  char *buf)
{
3752
	warn_scan_unevictable_pages();
3753 3754 3755
	return sprintf(buf, "0\n");	/* always zero; should fit... */
}

3756 3757
static ssize_t write_scan_unevictable_node(struct device *dev,
					   struct device_attribute *attr,
3758 3759
					const char *buf, size_t count)
{
3760
	warn_scan_unevictable_pages();
3761 3762 3763 3764
	return 1;
}


3765
static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3766 3767 3768 3769 3770
			read_scan_unevictable_node,
			write_scan_unevictable_node);

int scan_unevictable_register_node(struct node *node)
{
3771
	return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3772 3773 3774 3775
}

void scan_unevictable_unregister_node(struct node *node)
{
3776
	device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
3777
}
3778
#endif