vmscan.c 73.2 KB
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/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

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

#include <linux/swapops.h>

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#include "internal.h"

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

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	/*
	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
	 * are scanned.
	 */
	nodemask_t	*nodemask;

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

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

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

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

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

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

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

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	return &zone->reclaim_stat;
}

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

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	return zone_page_state(zone, NR_LRU_BASE + lru);
}


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

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

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

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

			cond_resched();
		}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	return PAGE_CLEAN;
}

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

	return 1;

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

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

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/**
 * 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.
 */
#ifdef CONFIG_UNEVICTABLE_LRU
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
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	int was_unevictable = PageUnevictable(page);
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	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

	if (page_evictable(page, NULL)) {
		/*
		 * For evictable pages, we can use the cache.
		 * In event of a race, worst case is we end up with an
		 * unevictable page on [in]active list.
		 * We know how to handle that.
		 */
		lru = active + page_is_file_cache(page);
		lru_cache_add_lru(page, lru);
	} else {
		/*
		 * Put unevictable pages directly on zone's unevictable
		 * list.
		 */
		lru = LRU_UNEVICTABLE;
		add_page_to_unevictable_list(page);
	}

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

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

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	put_page(page);		/* drop ref from isolate */
}

#else /* CONFIG_UNEVICTABLE_LRU */

void putback_lru_page(struct page *page)
{
	int lru;
	VM_BUG_ON(PageLRU(page));

	lru = !!TestClearPageActive(page) + page_is_file_cache(page);
	lru_cache_add_lru(page, lru);
	put_page(page);
}
#endif /* CONFIG_UNEVICTABLE_LRU */


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

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

		cond_resched();

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

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		if (!trylock_page(page))
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610 611
			goto keep;

N
Nick Piggin 已提交
612
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
613 614

		sc->nr_scanned++;
615

N
Nick Piggin 已提交
616 617
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
618

619
		if (!sc->may_unmap && page_mapped(page))
620 621
			goto keep_locked;

L
Linus Torvalds 已提交
622 623 624 625
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

626 627 628 629 630 631 632 633 634 635 636 637 638 639
		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));

		if (PageWriteback(page)) {
			/*
			 * Synchronous reclaim is performed in two passes,
			 * first an asynchronous pass over the list to
			 * start parallel writeback, and a second synchronous
			 * pass to wait for the IO to complete.  Wait here
			 * for any page for which writeback has already
			 * started.
			 */
			if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
				wait_on_page_writeback(page);
640
			else
641 642
				goto keep_locked;
		}
L
Linus Torvalds 已提交
643

644
		referenced = page_referenced(page, 1, sc->mem_cgroup);
L
Linus Torvalds 已提交
645
		/* In active use or really unfreeable?  Activate it. */
A
Andy Whitcroft 已提交
646 647
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
L
Linus Torvalds 已提交
648 649 650 651 652 653
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
654
		if (PageAnon(page) && !PageSwapCache(page)) {
655 656
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
657
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
658
				goto activate_locked;
659
			may_enter_fs = 1;
N
Nick Piggin 已提交
660
		}
L
Linus Torvalds 已提交
661 662 663 664 665 666 667 668

		mapping = page_mapping(page);

		/*
		 * The page is mapped into the page tables of one or more
		 * processes. Try to unmap it here.
		 */
		if (page_mapped(page) && mapping) {
669
			switch (try_to_unmap(page, 0)) {
L
Linus Torvalds 已提交
670 671 672 673
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
674 675
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
676 677 678 679 680 681
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
682
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
683
				goto keep_locked;
684
			if (!may_enter_fs)
L
Linus Torvalds 已提交
685
				goto keep_locked;
686
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
687 688 689
				goto keep_locked;

			/* Page is dirty, try to write it out here */
690
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
691 692 693 694 695
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
696
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
697 698 699 700 701
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
702
				if (!trylock_page(page))
L
Linus Torvalds 已提交
703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721
					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
722
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
723 724 725 726 727 728 729 730 731 732
		 * 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.
		 */
733
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
734 735
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751
			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
752 753
		}

N
Nick Piggin 已提交
754
		if (!mapping || !__remove_mapping(mapping, page))
755
			goto keep_locked;
L
Linus Torvalds 已提交
756

N
Nick Piggin 已提交
757 758 759 760 761 762 763 764
		/*
		 * 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
765
free_it:
766
		nr_reclaimed++;
N
Nick Piggin 已提交
767 768 769 770
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
771 772
		continue;

N
Nick Piggin 已提交
773
cull_mlocked:
774 775
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
776 777 778 779
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
780
activate_locked:
781 782
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
783
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
784
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
785 786 787 788 789 790
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
791
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
792 793 794
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
795
		__pagevec_free(&freed_pvec);
796
	count_vm_events(PGACTIVATE, pgactivate);
797
	return nr_reclaimed;
L
Linus Torvalds 已提交
798 799
}

A
Andy Whitcroft 已提交
800 801 802 803 804 805 806 807 808 809 810 811 812 813 814
/* LRU Isolation modes. */
#define ISOLATE_INACTIVE 0	/* Isolate inactive pages. */
#define ISOLATE_ACTIVE 1	/* Isolate active pages. */
#define ISOLATE_BOTH 2		/* Isolate both active and inactive pages. */

/*
 * Attempt to remove the specified page from its LRU.  Only take this page
 * if it is of the appropriate PageActive status.  Pages which are being
 * freed elsewhere are also ignored.
 *
 * page:	page to consider
 * mode:	one of the LRU isolation modes defined above
 *
 * returns 0 on success, -ve errno on failure.
 */
815
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
816 817 818 819 820 821 822 823 824 825 826 827 828 829 830
{
	int ret = -EINVAL;

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

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

831 832 833
	if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
		return ret;

L
Lee Schermerhorn 已提交
834 835 836 837 838 839 840 841
	/*
	 * When this function is being called for lumpy reclaim, we
	 * initially look into all LRU pages, active, inactive and
	 * unevictable; only give shrink_page_list evictable pages.
	 */
	if (PageUnevictable(page))
		return ret;

A
Andy Whitcroft 已提交
842
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
843

A
Andy Whitcroft 已提交
844 845 846 847 848 849 850 851
	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;
K
KAMEZAWA Hiroyuki 已提交
852
		mem_cgroup_del_lru(page);
A
Andy Whitcroft 已提交
853 854 855 856 857
	}

	return ret;
}

L
Linus Torvalds 已提交
858 859 860 861 862 863 864 865 866 867 868 869 870 871
/*
 * zone->lru_lock is heavily contended.  Some of the functions that
 * shrink the lists perform better by taking out a batch of pages
 * and working on them outside the LRU lock.
 *
 * For pagecache intensive workloads, this function is the hottest
 * spot in the kernel (apart from copy_*_user functions).
 *
 * Appropriate locks must be held before calling this function.
 *
 * @nr_to_scan:	The number of pages to look through on the list.
 * @src:	The LRU list to pull pages off.
 * @dst:	The temp list to put pages on to.
 * @scanned:	The number of pages that were scanned.
A
Andy Whitcroft 已提交
872 873
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
874
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
875 876 877
 *
 * returns how many pages were moved onto *@dst.
 */
878 879
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
880
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
881
{
882
	unsigned long nr_taken = 0;
883
	unsigned long scan;
L
Linus Torvalds 已提交
884

885
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
886 887 888 889 890 891
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
892 893 894
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
895
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
896

897
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
898 899
		case 0:
			list_move(&page->lru, dst);
900
			nr_taken++;
A
Andy Whitcroft 已提交
901 902 903 904 905 906
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
907

A
Andy Whitcroft 已提交
908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939
		default:
			BUG();
		}

		if (!order)
			continue;

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

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

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

			cursor_page = pfn_to_page(pfn);
940

A
Andy Whitcroft 已提交
941 942 943
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
944
			switch (__isolate_lru_page(cursor_page, mode, file)) {
A
Andy Whitcroft 已提交
945 946 947 948 949 950 951 952 953 954
			case 0:
				list_move(&cursor_page->lru, dst);
				nr_taken++;
				scan++;
				break;

			case -EBUSY:
				/* else it is being freed elsewhere */
				list_move(&cursor_page->lru, src);
			default:
L
Lee Schermerhorn 已提交
955
				break;	/* ! on LRU or wrong list */
A
Andy Whitcroft 已提交
956 957
			}
		}
L
Linus Torvalds 已提交
958 959 960 961 962 963
	}

	*scanned = scan;
	return nr_taken;
}

964 965 966 967 968
static unsigned long isolate_pages_global(unsigned long nr,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
969
					int active, int file)
970
{
971
	int lru = LRU_BASE;
972
	if (active)
973 974 975 976 977
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
								mode, !!file);
978 979
}

A
Andy Whitcroft 已提交
980 981 982 983
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
984 985
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
986 987
{
	int nr_active = 0;
988
	int lru;
A
Andy Whitcroft 已提交
989 990
	struct page *page;

991 992
	list_for_each_entry(page, page_list, lru) {
		lru = page_is_file_cache(page);
A
Andy Whitcroft 已提交
993
		if (PageActive(page)) {
994
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
995 996 997
			ClearPageActive(page);
			nr_active++;
		}
998 999
		count[lru]++;
	}
A
Andy Whitcroft 已提交
1000 1001 1002 1003

	return nr_active;
}

1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
/**
 * 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
1015 1016 1017
 * 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.
1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037
 *
 * The vmstat statistic corresponding to the list on which the page was
 * found will be decremented.
 *
 * Restrictions:
 * (1) Must be called with an elevated refcount on the page. This is a
 *     fundamentnal difference from isolate_lru_pages (which is called
 *     without a stable reference).
 * (2) the lru_lock must not be held.
 * (3) interrupts must be enabled.
 */
int isolate_lru_page(struct page *page)
{
	int ret = -EBUSY;

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

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
L
Lee Schermerhorn 已提交
1038
			int lru = page_lru(page);
1039 1040
			ret = 0;
			ClearPageLRU(page);
1041 1042

			del_page_from_lru_list(zone, page, lru);
1043 1044 1045 1046 1047 1048
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
1049
/*
A
Andrew Morton 已提交
1050 1051
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1052
 */
A
Andrew Morton 已提交
1053
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1054 1055
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1056 1057 1058
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1059
	unsigned long nr_scanned = 0;
1060
	unsigned long nr_reclaimed = 0;
1061
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1062 1063 1064 1065 1066

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1067
	do {
L
Linus Torvalds 已提交
1068
		struct page *page;
1069 1070 1071
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1072
		unsigned long nr_active;
1073
		unsigned int count[NR_LRU_LISTS] = { 0, };
R
Rik van Riel 已提交
1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086
		int mode = ISOLATE_INACTIVE;

		/*
		 * If we need a large contiguous chunk of memory, or have
		 * trouble getting a small set of contiguous pages, we
		 * will reclaim both active and inactive pages.
		 *
		 * We use the same threshold as pageout congestion_wait below.
		 */
		if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
			mode = ISOLATE_BOTH;
		else if (sc->order && priority < DEF_PRIORITY - 2)
			mode = ISOLATE_BOTH;
L
Linus Torvalds 已提交
1087

1088
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1089 1090 1091
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
		nr_active = clear_active_flags(&page_list, count);
1092
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1093

1094 1095 1096 1097 1098 1099 1100 1101 1102
		__mod_zone_page_state(zone, NR_ACTIVE_FILE,
						-count[LRU_ACTIVE_FILE]);
		__mod_zone_page_state(zone, NR_INACTIVE_FILE,
						-count[LRU_INACTIVE_FILE]);
		__mod_zone_page_state(zone, NR_ACTIVE_ANON,
						-count[LRU_ACTIVE_ANON]);
		__mod_zone_page_state(zone, NR_INACTIVE_ANON,
						-count[LRU_INACTIVE_ANON]);

1103
		if (scanning_global_lru(sc))
1104
			zone->pages_scanned += nr_scan;
K
KOSAKI Motohiro 已提交
1105 1106 1107 1108 1109 1110

		reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
		reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
		reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
		reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];

L
Linus Torvalds 已提交
1111 1112
		spin_unlock_irq(&zone->lru_lock);

1113
		nr_scanned += nr_scan;
1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
		nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);

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

			/*
			 * The attempt at page out may have made some
			 * of the pages active, mark them inactive again.
			 */
1130
			nr_active = clear_active_flags(&page_list, count);
1131 1132 1133 1134 1135 1136
			count_vm_events(PGDEACTIVATE, nr_active);

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

1137
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
1138 1139
		local_irq_disable();
		if (current_is_kswapd()) {
1140 1141
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
1142
		} else if (scanning_global_lru(sc))
1143
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1144

S
Shantanu Goel 已提交
1145
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1146

1147 1148 1149
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
1150
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1151 1152 1153 1154
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1155
			int lru;
L
Linus Torvalds 已提交
1156
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1157
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1158
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1159 1160 1161 1162 1163 1164 1165 1166 1167
			if (unlikely(!page_evictable(page, NULL))) {
				spin_unlock_irq(&zone->lru_lock);
				putback_lru_page(page);
				spin_lock_irq(&zone->lru_lock);
				continue;
			}
			SetPageLRU(page);
			lru = page_lru(page);
			add_page_to_lru_list(zone, page, lru);
K
KOSAKI Motohiro 已提交
1168
			if (PageActive(page)) {
1169
				int file = !!page_is_file_cache(page);
1170
				reclaim_stat->recent_rotated[file]++;
1171
			}
L
Linus Torvalds 已提交
1172 1173 1174 1175 1176 1177
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
1178
  	} while (nr_scanned < max_scan);
1179
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
1180
done:
1181
	local_irq_enable();
L
Linus Torvalds 已提交
1182
	pagevec_release(&pvec);
1183
	return nr_reclaimed;
L
Linus Torvalds 已提交
1184 1185
}

1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199
/*
 * We are about to scan this zone at a certain priority level.  If that priority
 * level is smaller (ie: more urgent) than the previous priority, then note
 * that priority level within the zone.  This is done so that when the next
 * process comes in to scan this zone, it will immediately start out at this
 * priority level rather than having to build up its own scanning priority.
 * Here, this priority affects only the reclaim-mapped threshold.
 */
static inline void note_zone_scanning_priority(struct zone *zone, int priority)
{
	if (priority < zone->prev_priority)
		zone->prev_priority = priority;
}

L
Linus Torvalds 已提交
1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
/*
 * 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.
 */
1217 1218


A
Andrew Morton 已提交
1219
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1220
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1221
{
1222
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1223
	int pgdeactivate = 0;
1224
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1225
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1226
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1227 1228
	struct page *page;
	struct pagevec pvec;
1229
	enum lru_list lru;
1230
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1231 1232 1233

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1234 1235
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
1236
					sc->mem_cgroup, 1, file);
1237 1238 1239 1240
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1241
	if (scanning_global_lru(sc)) {
1242
		zone->pages_scanned += pgscanned;
1243
	}
K
KOSAKI Motohiro 已提交
1244
	reclaim_stat->recent_scanned[!!file] += pgmoved;
1245

1246 1247 1248 1249
	if (file)
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
	else
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
L
Linus Torvalds 已提交
1250 1251
	spin_unlock_irq(&zone->lru_lock);

1252
	pgmoved = 0;
L
Linus Torvalds 已提交
1253 1254 1255 1256
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1257

L
Lee Schermerhorn 已提交
1258 1259 1260 1261 1262
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1263 1264 1265 1266 1267
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
		    page_referenced(page, 0, sc->mem_cgroup))
			pgmoved++;

L
Linus Torvalds 已提交
1268 1269 1270
		list_add(&page->lru, &l_inactive);
	}

1271 1272 1273 1274 1275 1276
	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);
	lru = LRU_BASE + file * LRU_FILE;

1277
	spin_lock_irq(&zone->lru_lock);
1278
	/*
1279 1280 1281 1282 1283
	 * Count referenced pages from currently used mappings as
	 * rotated, even though they are moved to the inactive list.
	 * This helps balance scan pressure between file and anonymous
	 * pages in get_scan_ratio.
	 */
K
KOSAKI Motohiro 已提交
1284
	reclaim_stat->recent_rotated[!!file] += pgmoved;
1285

1286
	pgmoved = 0;
L
Linus Torvalds 已提交
1287 1288 1289
	while (!list_empty(&l_inactive)) {
		page = lru_to_page(&l_inactive);
		prefetchw_prev_lru_page(page, &l_inactive, flags);
N
Nick Piggin 已提交
1290
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1291
		SetPageLRU(page);
N
Nick Piggin 已提交
1292
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1293 1294
		ClearPageActive(page);

1295
		list_move(&page->lru, &zone->lru[lru].list);
K
KAMEZAWA Hiroyuki 已提交
1296
		mem_cgroup_add_lru_list(page, lru);
L
Linus Torvalds 已提交
1297 1298
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1299
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1300 1301 1302 1303 1304 1305 1306 1307 1308
			spin_unlock_irq(&zone->lru_lock);
			pgdeactivate += pgmoved;
			pgmoved = 0;
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
1309
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1310
	pgdeactivate += pgmoved;
1311 1312 1313
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
1314 1315
	if (buffer_heads_over_limit)
		pagevec_strip(&pvec);
N
Nick Piggin 已提交
1316
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1317 1318
}

1319
static int inactive_anon_is_low_global(struct zone *zone)
1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331
{
	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;
}

1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343
/**
 * inactive_anon_is_low - check if anonymous pages need to be deactivated
 * @zone: zone to check
 * @sc:   scan control of this context
 *
 * Returns true if the zone does not have enough inactive anon pages,
 * meaning some active anon pages need to be deactivated.
 */
static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
{
	int low;

1344
	if (scanning_global_lru(sc))
1345 1346
		low = inactive_anon_is_low_global(zone);
	else
1347
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1348 1349 1350
	return low;
}

1351
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1352 1353
	struct zone *zone, struct scan_control *sc, int priority)
{
1354 1355
	int file = is_file_lru(lru);

1356 1357 1358 1359 1360
	if (lru == LRU_ACTIVE_FILE) {
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
		return 0;
	}

1361
	if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1362
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1363 1364
		return 0;
	}
R
Rik van Riel 已提交
1365
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382
}

/*
 * 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.
 *
 * percent[0] specifies how much pressure to put on ram/swap backed
 * memory, while percent[1] determines pressure on the file LRUs.
 */
static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
					unsigned long *percent)
{
	unsigned long anon, file, free;
	unsigned long anon_prio, file_prio;
	unsigned long ap, fp;
1383
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1384 1385

	/* If we have no swap space, do not bother scanning anon pages. */
1386
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
1387 1388 1389 1390 1391
		percent[0] = 0;
		percent[1] = 100;
		return;
	}

1392 1393 1394 1395
	anon  = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1396

1397
	if (scanning_global_lru(sc)) {
1398 1399 1400 1401 1402 1403 1404 1405
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
		if (unlikely(file + free <= zone->pages_high)) {
			percent[0] = 100;
			percent[1] = 0;
			return;
		}
1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418
	}

	/*
	 * 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]
	 */
1419
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1420
		spin_lock_irq(&zone->lru_lock);
1421 1422
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1423 1424 1425
		spin_unlock_irq(&zone->lru_lock);
	}

1426
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1427
		spin_lock_irq(&zone->lru_lock);
1428 1429
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440
		spin_unlock_irq(&zone->lru_lock);
	}

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

	/*
1441 1442 1443
	 * 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.
1444
	 */
1445 1446
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1447

1448 1449
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1450 1451 1452 1453

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1454 1455
}

1456

L
Linus Torvalds 已提交
1457 1458 1459
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1460
static void shrink_zone(int priority, struct zone *zone,
1461
				struct scan_control *sc)
L
Linus Torvalds 已提交
1462
{
1463
	unsigned long nr[NR_LRU_LISTS];
1464
	unsigned long nr_to_scan;
1465
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1466
	enum lru_list l;
1467 1468
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
L
Linus Torvalds 已提交
1469

1470 1471
	get_scan_ratio(zone, sc, percent);

L
Lee Schermerhorn 已提交
1472
	for_each_evictable_lru(l) {
1473
		int file = is_file_lru(l);
1474
		unsigned long scan;
1475

1476
		scan = zone_nr_pages(zone, sc, l);
1477 1478 1479 1480
		if (priority) {
			scan >>= priority;
			scan = (scan * percent[file]) / 100;
		}
1481
		if (scanning_global_lru(sc)) {
1482
			zone->lru[l].nr_scan += scan;
1483
			nr[l] = zone->lru[l].nr_scan;
1484
			if (nr[l] >= swap_cluster_max)
1485 1486 1487
				zone->lru[l].nr_scan = 0;
			else
				nr[l] = 0;
1488 1489
		} else
			nr[l] = scan;
1490
	}
L
Linus Torvalds 已提交
1491

1492 1493
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1494
		for_each_evictable_lru(l) {
1495
			if (nr[l]) {
1496
				nr_to_scan = min(nr[l], swap_cluster_max);
1497
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1498

1499 1500
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1501
			}
L
Linus Torvalds 已提交
1502
		}
1503 1504 1505 1506 1507 1508 1509 1510
		/*
		 * On large memory systems, scan >> priority can become
		 * really large. This is fine for the starting priority;
		 * we want to put equal scanning pressure on each zone.
		 * However, if the VM has a harder time of freeing pages,
		 * with multiple processes reclaiming pages, the total
		 * freeing target can get unreasonably large.
		 */
1511
		if (nr_reclaimed > swap_cluster_max &&
1512 1513
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1514 1515
	}

1516 1517
	sc->nr_reclaimed = nr_reclaimed;

1518 1519 1520 1521
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1522
	if (inactive_anon_is_low(zone, sc))
1523 1524
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1525
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541
}

/*
 * This is the direct reclaim path, for page-allocating processes.  We only
 * try to reclaim pages from zones which will satisfy the caller's allocation
 * request.
 *
 * We reclaim from a zone even if that zone is over pages_high.  Because:
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
 * b) The zones may be over pages_high but they must go *over* pages_high to
 *    satisfy the `incremental min' zone defense algorithm.
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1542
static void shrink_zones(int priority, struct zonelist *zonelist,
1543
					struct scan_control *sc)
L
Linus Torvalds 已提交
1544
{
1545
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1546
	struct zoneref *z;
1547
	struct zone *zone;
1548

1549
	sc->all_unreclaimable = 1;
1550 1551
	for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
					sc->nodemask) {
1552
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1553
			continue;
1554 1555 1556 1557
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1558
		if (scanning_global_lru(sc)) {
1559 1560 1561
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1562

1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
			if (zone_is_all_unreclaimable(zone) &&
						priority != DEF_PRIORITY)
				continue;	/* Let kswapd poll it */
			sc->all_unreclaimable = 0;
		} else {
			/*
			 * Ignore cpuset limitation here. We just want to reduce
			 * # of used pages by us regardless of memory shortage.
			 */
			sc->all_unreclaimable = 0;
			mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
							priority);
		}
1576

1577
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1578 1579
	}
}
1580

L
Linus Torvalds 已提交
1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592
/*
 * This is the main entry point to direct page reclaim.
 *
 * If a full scan of the inactive list fails to free enough memory then we
 * are "out of memory" and something needs to be killed.
 *
 * If the caller is !__GFP_FS then the probability of a failure is reasonably
 * high - the zone may be full of dirty or under-writeback pages, which this
 * caller can't do much about.  We kick pdflush and take explicit naps in the
 * hope that some of these pages can be written.  But if the allocating task
 * holds filesystem locks which prevent writeout this might not work, and the
 * allocation attempt will fail.
1593 1594 1595
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1596
 */
1597
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1598
					struct scan_control *sc)
L
Linus Torvalds 已提交
1599 1600
{
	int priority;
1601
	unsigned long ret = 0;
1602
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1603 1604
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1605
	struct zoneref *z;
1606
	struct zone *zone;
1607
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1608

1609 1610
	delayacct_freepages_start();

1611
	if (scanning_global_lru(sc))
1612 1613 1614 1615
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
1616
	if (scanning_global_lru(sc)) {
1617
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1618

1619 1620
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1621

1622
			lru_pages += zone_lru_pages(zone);
1623
		}
L
Linus Torvalds 已提交
1624 1625 1626
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1627
		sc->nr_scanned = 0;
1628 1629
		if (!priority)
			disable_swap_token();
1630
		shrink_zones(priority, zonelist, sc);
1631 1632 1633 1634
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1635
		if (scanning_global_lru(sc)) {
1636
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1637
			if (reclaim_state) {
1638
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1639 1640
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1641
		}
1642
		total_scanned += sc->nr_scanned;
1643 1644
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1645 1646 1647 1648 1649 1650 1651 1652 1653 1654
			goto out;
		}

		/*
		 * Try to write back as many pages as we just scanned.  This
		 * tends to cause slow streaming writers to write data to the
		 * disk smoothly, at the dirtying rate, which is nice.   But
		 * that's undesirable in laptop mode, where we *want* lumpy
		 * writeout.  So in laptop mode, write out the whole world.
		 */
1655 1656
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1657
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1658
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1659 1660 1661
		}

		/* Take a nap, wait for some writeback to complete */
1662
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1663
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1664
	}
1665
	/* top priority shrink_zones still had more to do? don't OOM, then */
1666
	if (!sc->all_unreclaimable && scanning_global_lru(sc))
1667
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1668
out:
1669 1670 1671 1672 1673 1674 1675 1676 1677
	/*
	 * Now that we've scanned all the zones at this priority level, note
	 * that level within the zone so that the next thread which performs
	 * scanning of this zone will immediately start out at this priority
	 * level.  This affects only the decision whether or not to bring
	 * mapped pages onto the inactive list.
	 */
	if (priority < 0)
		priority = 0;
L
Linus Torvalds 已提交
1678

1679
	if (scanning_global_lru(sc)) {
1680
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1681 1682 1683 1684 1685 1686 1687 1688

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

			zone->prev_priority = priority;
		}
	} else
		mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
L
Linus Torvalds 已提交
1689

1690 1691
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1692 1693 1694
	return ret;
}

1695
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1696
				gfp_t gfp_mask, nodemask_t *nodemask)
1697 1698 1699 1700 1701
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
1702
		.may_unmap = 1,
1703
		.may_swap = 1,
1704 1705 1706 1707
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1708
		.nodemask = nodemask,
1709 1710
	};

1711
	return do_try_to_free_pages(zonelist, &sc);
1712 1713
}

1714
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1715

1716
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
1717 1718 1719
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
1720 1721 1722
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
1723
		.may_unmap = 1,
1724
		.may_swap = !noswap,
1725
		.swap_cluster_max = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
1726
		.swappiness = swappiness,
1727 1728 1729
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
1730
		.nodemask = NULL, /* we don't care the placement */
1731
	};
1732
	struct zonelist *zonelist;
1733

1734 1735 1736 1737
	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
	return do_try_to_free_pages(zonelist, &sc);
1738 1739 1740
}
#endif

L
Linus Torvalds 已提交
1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
 * they are all at pages_high.
 *
 * Returns the number of pages which were actually freed.
 *
 * There is special handling here for zones which are full of pinned pages.
 * This can happen if the pages are all mlocked, or if they are all used by
 * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
 * What we do is to detect the case where all pages in the zone have been
 * scanned twice and there has been zero successful reclaim.  Mark the zone as
 * dead and from now on, only perform a short scan.  Basically we're polling
 * the zone for when the problem goes away.
 *
 * kswapd scans the zones in the highmem->normal->dma direction.  It skips
 * zones which have free_pages > pages_high, but once a zone is found to have
 * free_pages <= pages_high, we scan that zone and the lower zones regardless
 * of the number of free pages in the lower zones.  This interoperates with
 * the page allocator fallback scheme to ensure that aging of pages is balanced
 * across the zones.
 */
1762
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1763 1764 1765 1766
{
	int all_zones_ok;
	int priority;
	int i;
1767
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1768
	struct reclaim_state *reclaim_state = current->reclaim_state;
1769 1770
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
1771
		.may_unmap = 1,
1772
		.may_swap = 1,
1773 1774
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1775
		.order = order,
1776 1777
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1778
	};
1779 1780 1781 1782 1783
	/*
	 * temp_priority is used to remember the scanning priority at which
	 * this zone was successfully refilled to free_pages == pages_high.
	 */
	int temp_priority[MAX_NR_ZONES];
L
Linus Torvalds 已提交
1784 1785 1786

loop_again:
	total_scanned = 0;
1787
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1788
	sc.may_writepage = !laptop_mode;
1789
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1790

1791 1792
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1793 1794 1795 1796 1797

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

1798 1799 1800 1801
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1802 1803
		all_zones_ok = 1;

1804 1805 1806 1807 1808 1809
		/*
		 * 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
1810

1811 1812
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1813

1814 1815
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1816
				continue;
L
Linus Torvalds 已提交
1817

1818 1819 1820 1821
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
1822
			if (inactive_anon_is_low(zone, &sc))
1823 1824 1825
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

1826 1827 1828
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1829
				break;
L
Linus Torvalds 已提交
1830 1831
			}
		}
A
Andrew Morton 已提交
1832 1833 1834
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1835 1836 1837
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1838
			lru_pages += zone_lru_pages(zone);
L
Linus Torvalds 已提交
1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851
		}

		/*
		 * 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;
1852
			int nr_slab;
L
Linus Torvalds 已提交
1853

1854
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1855 1856
				continue;

1857 1858
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1859 1860
				continue;

1861 1862 1863
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1864
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1865
			sc.nr_scanned = 0;
1866
			note_zone_scanning_priority(zone, priority);
1867 1868 1869 1870 1871 1872
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
			if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
						end_zone, 0))
1873
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1874
			reclaim_state->reclaimed_slab = 0;
1875 1876
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1877
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1878
			total_scanned += sc.nr_scanned;
1879
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1880
				continue;
1881
			if (nr_slab == 0 && zone->pages_scanned >=
1882
						(zone_lru_pages(zone) * 6))
1883 1884
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1885 1886 1887 1888 1889 1890
			/*
			 * If we've done a decent amount of scanning and
			 * the reclaim ratio is low, start doing writepage
			 * even in laptop mode
			 */
			if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1891
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
1892 1893 1894 1895 1896 1897 1898 1899
				sc.may_writepage = 1;
		}
		if (all_zones_ok)
			break;		/* kswapd: all done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
1900
		if (total_scanned && priority < DEF_PRIORITY - 2)
1901
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1902 1903 1904 1905 1906 1907 1908

		/*
		 * We do this so kswapd doesn't build up large priorities for
		 * example when it is freeing in parallel with allocators. It
		 * matches the direct reclaim path behaviour in terms of impact
		 * on zone->*_priority.
		 */
1909
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1910 1911 1912
			break;
	}
out:
1913 1914 1915 1916 1917
	/*
	 * Note within each zone the priority level at which this zone was
	 * brought into a happy state.  So that the next thread which scans this
	 * zone will start out at that priority level.
	 */
L
Linus Torvalds 已提交
1918 1919 1920
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1921
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
1922 1923 1924
	}
	if (!all_zones_ok) {
		cond_resched();
1925 1926 1927

		try_to_freeze();

1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944
		/*
		 * Fragmentation may mean that the system cannot be
		 * rebalanced for high-order allocations in all zones.
		 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
		 * it means the zones have been fully scanned and are still
		 * not balanced. For high-order allocations, there is
		 * little point trying all over again as kswapd may
		 * infinite loop.
		 *
		 * Instead, recheck all watermarks at order-0 as they
		 * are the most important. If watermarks are ok, kswapd will go
		 * back to sleep. High-order users can still perform direct
		 * reclaim if they wish.
		 */
		if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
			order = sc.order = 0;

L
Linus Torvalds 已提交
1945 1946 1947
		goto loop_again;
	}

1948
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
1949 1950 1951 1952
}

/*
 * The background pageout daemon, started as a kernel thread
1953
 * from the init process.
L
Linus Torvalds 已提交
1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
 *
 * This basically trickles out pages so that we have _some_
 * free memory available even if there is no other activity
 * that frees anything up. This is needed for things like routing
 * etc, where we otherwise might have all activity going on in
 * asynchronous contexts that cannot page things out.
 *
 * If there are applications that are active memory-allocators
 * (most normal use), this basically shouldn't matter.
 */
static int kswapd(void *p)
{
	unsigned long order;
	pg_data_t *pgdat = (pg_data_t*)p;
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	struct reclaim_state reclaim_state = {
		.reclaimed_slab = 0,
	};
1973
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
1974

1975 1976
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
1977
	if (!cpumask_empty(cpumask))
1978
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992
	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).
	 */
1993
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1994
	set_freezable();
L
Linus Torvalds 已提交
1995 1996 1997 1998

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
1999

L
Linus Torvalds 已提交
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
		new_order = pgdat->kswapd_max_order;
		pgdat->kswapd_max_order = 0;
		if (order < new_order) {
			/*
			 * Don't sleep if someone wants a larger 'order'
			 * allocation
			 */
			order = new_order;
		} else {
2010 2011 2012
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
2013 2014 2015 2016
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2017 2018 2019 2020 2021 2022
		if (!try_to_freeze()) {
			/* We can speed up thawing tasks if we don't call
			 * balance_pgdat after returning from the refrigerator
			 */
			balance_pgdat(pgdat, order);
		}
L
Linus Torvalds 已提交
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
	}
	return 0;
}

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

2034
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2035 2036 2037
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
2038
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
2039 2040 2041
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2042
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2043
		return;
2044
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2045
		return;
2046
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2047 2048
}

2049 2050 2051 2052 2053 2054 2055 2056
unsigned long global_lru_pages(void)
{
	return global_page_state(NR_ACTIVE_ANON)
		+ global_page_state(NR_ACTIVE_FILE)
		+ global_page_state(NR_INACTIVE_ANON)
		+ global_page_state(NR_INACTIVE_FILE);
}

L
Linus Torvalds 已提交
2057 2058
#ifdef CONFIG_PM
/*
2059
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
2060
 * from LRU lists system-wide, for given pass and priority.
2061 2062 2063
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
2064
static void shrink_all_zones(unsigned long nr_pages, int prio,
2065
				      int pass, struct scan_control *sc)
2066 2067
{
	struct zone *zone;
2068
	unsigned long nr_reclaimed = 0;
2069

2070
	for_each_populated_zone(zone) {
2071
		enum lru_list l;
2072

2073
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2074 2075
			continue;

L
Lee Schermerhorn 已提交
2076
		for_each_evictable_lru(l) {
2077 2078 2079
			enum zone_stat_item ls = NR_LRU_BASE + l;
			unsigned long lru_pages = zone_page_state(zone, ls);

L
Lee Schermerhorn 已提交
2080
			/* For pass = 0, we don't shrink the active list */
2081 2082
			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
						l == LRU_ACTIVE_FILE))
2083 2084
				continue;

2085
			zone->lru[l].nr_scan += (lru_pages >> prio) + 1;
2086
			if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2087 2088
				unsigned long nr_to_scan;

2089
				zone->lru[l].nr_scan = 0;
2090
				nr_to_scan = min(nr_pages, lru_pages);
2091
				nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2092
								sc, prio);
2093
				if (nr_reclaimed >= nr_pages) {
2094
					sc->nr_reclaimed += nr_reclaimed;
2095 2096
					return;
				}
2097 2098 2099
			}
		}
	}
2100
	sc->nr_reclaimed += nr_reclaimed;
2101 2102 2103 2104 2105 2106 2107 2108 2109
}

/*
 * Try to free `nr_pages' of memory, system-wide, and return the number of
 * freed pages.
 *
 * Rather than trying to age LRUs the aim is to preserve the overall
 * LRU order by reclaiming preferentially
 * inactive > active > active referenced > active mapped
L
Linus Torvalds 已提交
2110
 */
2111
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2112
{
2113 2114 2115 2116 2117
	unsigned long lru_pages, nr_slab;
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2118
		.may_unmap = 0,
2119
		.may_writepage = 1,
2120
		.isolate_pages = isolate_pages_global,
2121
		.nr_reclaimed = 0,
L
Linus Torvalds 已提交
2122 2123 2124
	};

	current->reclaim_state = &reclaim_state;
2125

2126
	lru_pages = global_lru_pages();
2127
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2128 2129 2130 2131 2132
	/* If slab caches are huge, it's better to hit them first */
	while (nr_slab >= lru_pages) {
		reclaim_state.reclaimed_slab = 0;
		shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
		if (!reclaim_state.reclaimed_slab)
L
Linus Torvalds 已提交
2133
			break;
2134

2135 2136
		sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		if (sc.nr_reclaimed >= nr_pages)
2137 2138 2139
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2140
	}
2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153

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

		/* Force reclaiming mapped pages in the passes #3 and #4 */
2154
		if (pass > 2)
2155
			sc.may_unmap = 1;
2156 2157

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2158
			unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2159 2160

			sc.nr_scanned = 0;
2161
			sc.swap_cluster_max = nr_to_scan;
2162 2163
			shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (sc.nr_reclaimed >= nr_pages)
2164 2165 2166
				goto out;

			reclaim_state.reclaimed_slab = 0;
2167
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2168
					global_lru_pages());
2169 2170
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
			if (sc.nr_reclaimed >= nr_pages)
2171 2172 2173
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2174
				congestion_wait(WRITE, HZ / 10);
2175
		}
2176
	}
2177 2178

	/*
2179 2180
	 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
	 * something in slab caches
2181
	 */
2182
	if (!sc.nr_reclaimed) {
2183 2184
		do {
			reclaim_state.reclaimed_slab = 0;
2185
			shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2186 2187 2188
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		} while (sc.nr_reclaimed < nr_pages &&
				reclaim_state.reclaimed_slab > 0);
2189
	}
2190

2191

2192
out:
L
Linus Torvalds 已提交
2193
	current->reclaim_state = NULL;
2194

2195
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
2196 2197 2198 2199 2200 2201 2202
}
#endif

/* It's optimal to keep kswapds on the same CPUs as their memory, but
   not required for correctness.  So if the last cpu in a node goes
   away, we get changed to run anywhere: as the first one comes back,
   restore their cpu bindings. */
2203
static int __devinit cpu_callback(struct notifier_block *nfb,
2204
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2205
{
2206
	int nid;
L
Linus Torvalds 已提交
2207

2208
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2209
		for_each_node_state(nid, N_HIGH_MEMORY) {
2210
			pg_data_t *pgdat = NODE_DATA(nid);
2211 2212 2213
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2214

2215
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2216
				/* One of our CPUs online: restore mask */
2217
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2218 2219 2220 2221 2222
		}
	}
	return NOTIFY_OK;
}

2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244
/*
 * This kswapd start function will be called by init and node-hot-add.
 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
 */
int kswapd_run(int nid)
{
	pg_data_t *pgdat = NODE_DATA(nid);
	int ret = 0;

	if (pgdat->kswapd)
		return 0;

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

L
Linus Torvalds 已提交
2245 2246
static int __init kswapd_init(void)
{
2247
	int nid;
2248

L
Linus Torvalds 已提交
2249
	swap_setup();
2250
	for_each_node_state(nid, N_HIGH_MEMORY)
2251
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2252 2253 2254 2255 2256
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2257 2258 2259 2260 2261 2262 2263 2264 2265 2266

#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;

2267
#define RECLAIM_OFF 0
2268
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2269 2270 2271
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2272 2273 2274 2275 2276 2277 2278
/*
 * 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

2279 2280 2281 2282 2283 2284
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2285 2286 2287 2288 2289 2290
/*
 * 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;

2291 2292 2293
/*
 * Try to free up some pages from this zone through reclaim.
 */
2294
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2295
{
2296
	/* Minimum pages needed in order to stay on node */
2297
	const unsigned long nr_pages = 1 << order;
2298 2299
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2300
	int priority;
2301 2302
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2303
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2304
		.may_swap = 1,
2305 2306
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2307
		.gfp_mask = gfp_mask,
2308
		.swappiness = vm_swappiness,
2309
		.order = order,
2310
		.isolate_pages = isolate_pages_global,
2311
	};
2312
	unsigned long slab_reclaimable;
2313 2314 2315

	disable_swap_token();
	cond_resched();
2316 2317 2318 2319 2320 2321
	/*
	 * 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;
2322 2323
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2324

2325 2326 2327 2328 2329 2330 2331 2332 2333
	if (zone_page_state(zone, NR_FILE_PAGES) -
		zone_page_state(zone, NR_FILE_MAPPED) >
		zone->min_unmapped_pages) {
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2334
			note_zone_scanning_priority(zone, priority);
2335
			shrink_zone(priority, zone, &sc);
2336
			priority--;
2337
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2338
	}
2339

2340 2341
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2342
		/*
2343
		 * shrink_slab() does not currently allow us to determine how
2344 2345 2346 2347
		 * 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.
2348
		 *
2349 2350
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2351
		 */
2352
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2353 2354
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2355
			;
2356 2357 2358 2359 2360

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2361
		sc.nr_reclaimed += slab_reclaimable -
2362
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2363 2364
	}

2365
	p->reclaim_state = NULL;
2366
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2367
	return sc.nr_reclaimed >= nr_pages;
2368
}
2369 2370 2371 2372

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2373
	int ret;
2374 2375

	/*
2376 2377
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2378
	 *
2379 2380 2381 2382 2383
	 * 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.
2384
	 */
2385
	if (zone_page_state(zone, NR_FILE_PAGES) -
2386 2387 2388
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2389
		return 0;
2390

2391 2392 2393
	if (zone_is_all_unreclaimable(zone))
		return 0;

2394
	/*
2395
	 * Do not scan if the allocation should not be delayed.
2396
	 */
2397
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2398 2399 2400 2401 2402 2403 2404 2405
			return 0;

	/*
	 * Only run zone reclaim on the local zone or on zones that do not
	 * have associated processors. This will favor the local processor
	 * over remote processors and spread off node memory allocations
	 * as wide as possible.
	 */
2406
	node_id = zone_to_nid(zone);
2407
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2408
		return 0;
2409 2410 2411 2412 2413 2414 2415

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

	return ret;
2416
}
2417
#endif
L
Lee Schermerhorn 已提交
2418 2419 2420 2421 2422 2423 2424 2425

#ifdef CONFIG_UNEVICTABLE_LRU
/*
 * page_evictable - test whether a page is evictable
 * @page: the page to test
 * @vma: the VMA in which the page is or will be mapped, may be NULL
 *
 * Test whether page is evictable--i.e., should be placed on active/inactive
N
Nick Piggin 已提交
2426 2427
 * lists vs unevictable list.  The vma argument is !NULL when called from the
 * fault path to determine how to instantate a new page.
L
Lee Schermerhorn 已提交
2428 2429
 *
 * Reasons page might not be evictable:
2430
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2431
 * (2) page is part of an mlocked VMA
2432
 *
L
Lee Schermerhorn 已提交
2433 2434 2435 2436
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2437 2438 2439
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2440 2441
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2442 2443 2444

	return 1;
}
2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464

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

retry:
	ClearPageUnevictable(page);
	if (page_evictable(page, NULL)) {
		enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2465

2466 2467
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2468
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2469 2470 2471 2472 2473 2474 2475 2476
		__inc_zone_state(zone, NR_INACTIVE_ANON + l);
		__count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		/*
		 * rotate unevictable list
		 */
		SetPageUnevictable(page);
		list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
K
KAMEZAWA Hiroyuki 已提交
2477
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
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 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536
		if (page_evictable(page, NULL))
			goto retry;
	}
}

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

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

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

		zone = NULL;

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

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

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

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

		count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
	}

}
2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548

/**
 * scan_zone_unevictable_pages - check unevictable list for evictable pages
 * @zone - zone of which to scan the unevictable list
 *
 * Scan @zone's unevictable LRU lists to check for pages that have become
 * evictable.  Move those that have to @zone's inactive list where they
 * become candidates for reclaim, unless shrink_inactive_zone() decides
 * to reactivate them.  Pages that are still unevictable are rotated
 * back onto @zone's unevictable list.
 */
#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2549
static void scan_zone_unevictable_pages(struct zone *zone)
2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590
{
	struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
	unsigned long scan;
	unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);

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

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

			if (!trylock_page(page))
				continue;

			prefetchw_prev_lru_page(page, l_unevictable, flags);

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

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

		nr_to_scan -= batch_size;
	}
}


/**
 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
 *
 * A really big hammer:  scan all zones' unevictable LRU lists to check for
 * pages that have become evictable.  Move those back to the zones'
 * inactive list where they become candidates for reclaim.
 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
 * and we add swap to the system.  As such, it runs in the context of a task
 * that has possibly/probably made some previously unevictable pages
 * evictable.
 */
2591
static void scan_all_zones_unevictable_pages(void)
2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665
{
	struct zone *zone;

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

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

int scan_unevictable_handler(struct ctl_table *table, int write,
			   struct file *file, void __user *buffer,
			   size_t *length, loff_t *ppos)
{
	proc_doulongvec_minmax(table, write, file, buffer, length, ppos);

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

	scan_unevictable_pages = 0;
	return 0;
}

/*
 * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
 * a specified node's per zone unevictable lists for evictable pages.
 */

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

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

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

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


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

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

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

L
Lee Schermerhorn 已提交
2666
#endif