vmscan.c 73.3 KB
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/*
 *  linux/mm/vmscan.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

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

	return 1;

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

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

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/**
 * putback_lru_page - put previously isolated page onto appropriate LRU list
 * @page: page to be put back to appropriate lru list
 *
 * Add previously isolated @page to appropriate LRU list.
 * Page may still be unevictable for other reasons.
 *
 * lru_lock must not be held, interrupts must be enabled.
 */
#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);

N
Nick Piggin 已提交
611
		if (!trylock_page(page))
L
Linus Torvalds 已提交
612 613
			goto keep;

N
Nick Piggin 已提交
614
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
615 616

		sc->nr_scanned++;
617

N
Nick Piggin 已提交
618 619
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
620

621
		if (!sc->may_unmap && page_mapped(page))
622 623
			goto keep_locked;

L
Linus Torvalds 已提交
624 625 626 627
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

628 629 630 631 632 633 634 635 636 637 638 639 640 641
		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);
642
			else
643 644
				goto keep_locked;
		}
L
Linus Torvalds 已提交
645

646
		referenced = page_referenced(page, 1, sc->mem_cgroup);
L
Linus Torvalds 已提交
647
		/* In active use or really unfreeable?  Activate it. */
A
Andy Whitcroft 已提交
648 649
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
					referenced && page_mapping_inuse(page))
L
Linus Torvalds 已提交
650 651 652 653 654 655
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
656
		if (PageAnon(page) && !PageSwapCache(page)) {
657 658
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
659
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
660
				goto activate_locked;
661
			may_enter_fs = 1;
N
Nick Piggin 已提交
662
		}
L
Linus Torvalds 已提交
663 664 665 666 667 668 669 670

		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) {
671
			switch (try_to_unmap(page, 0)) {
L
Linus Torvalds 已提交
672 673 674 675
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
676 677
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
678 679 680 681 682 683
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
684
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
685
				goto keep_locked;
686
			if (!may_enter_fs)
L
Linus Torvalds 已提交
687
				goto keep_locked;
688
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
689 690 691
				goto keep_locked;

			/* Page is dirty, try to write it out here */
692
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
693 694 695 696 697
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
698
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
699 700 701 702 703
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
704
				if (!trylock_page(page))
L
Linus Torvalds 已提交
705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723
					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
724
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
725 726 727 728 729 730 731 732 733 734
		 * 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.
		 */
735
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
736 737
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753
			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
754 755
		}

N
Nick Piggin 已提交
756
		if (!mapping || !__remove_mapping(mapping, page))
757
			goto keep_locked;
L
Linus Torvalds 已提交
758

N
Nick Piggin 已提交
759 760 761 762 763 764 765 766
		/*
		 * 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
767
free_it:
768
		nr_reclaimed++;
N
Nick Piggin 已提交
769 770 771 772
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
773 774
		continue;

N
Nick Piggin 已提交
775
cull_mlocked:
776 777
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
778 779 780 781
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
782
activate_locked:
783 784
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
785
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
786
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
787 788 789 790 791 792
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
793
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
794 795 796
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
797
		__pagevec_free(&freed_pvec);
798
	count_vm_events(PGACTIVATE, pgactivate);
799
	return nr_reclaimed;
L
Linus Torvalds 已提交
800 801
}

A
Andy Whitcroft 已提交
802 803 804 805 806 807 808 809 810 811 812 813 814 815 816
/* 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.
 */
817
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
818 819 820 821 822 823 824 825 826 827 828 829 830 831 832
{
	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;

833 834 835
	if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
		return ret;

L
Lee Schermerhorn 已提交
836 837 838 839 840 841 842 843
	/*
	 * 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
844
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
845

A
Andy Whitcroft 已提交
846 847 848 849 850 851 852 853
	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
854
		mem_cgroup_del_lru(page);
A
Andy Whitcroft 已提交
855 856 857 858 859
	}

	return ret;
}

L
Linus Torvalds 已提交
860 861 862 863 864 865 866 867 868 869 870 871 872 873
/*
 * 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
874 875
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
876
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
877 878 879
 *
 * returns how many pages were moved onto *@dst.
 */
880 881
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
882
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
883
{
884
	unsigned long nr_taken = 0;
885
	unsigned long scan;
L
Linus Torvalds 已提交
886

887
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
888 889 890 891 892 893
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
894 895 896
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
897
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
898

899
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
900 901
		case 0:
			list_move(&page->lru, dst);
902
			nr_taken++;
A
Andy Whitcroft 已提交
903 904 905 906 907 908
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
			continue;
909

A
Andy Whitcroft 已提交
910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941
		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);
942

A
Andy Whitcroft 已提交
943 944 945
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
946
			switch (__isolate_lru_page(cursor_page, mode, file)) {
A
Andy Whitcroft 已提交
947 948 949 950 951 952 953 954 955 956
			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
957
				break;	/* ! on LRU or wrong list */
A
Andy Whitcroft 已提交
958 959
			}
		}
L
Linus Torvalds 已提交
960 961 962 963 964 965
	}

	*scanned = scan;
	return nr_taken;
}

966 967 968 969 970
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,
971
					int active, int file)
972
{
973
	int lru = LRU_BASE;
974
	if (active)
975 976 977 978 979
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
								mode, !!file);
980 981
}

A
Andy Whitcroft 已提交
982 983 984 985
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
986 987
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
988 989
{
	int nr_active = 0;
990
	int lru;
A
Andy Whitcroft 已提交
991 992
	struct page *page;

993 994
	list_for_each_entry(page, page_list, lru) {
		lru = page_is_file_cache(page);
A
Andy Whitcroft 已提交
995
		if (PageActive(page)) {
996
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
997 998 999
			ClearPageActive(page);
			nr_active++;
		}
1000 1001
		count[lru]++;
	}
A
Andy Whitcroft 已提交
1002 1003 1004 1005

	return nr_active;
}

1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
/**
 * 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
1017 1018 1019
 * 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.
1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039
 *
 * 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
1040
			int lru = page_lru(page);
1041 1042
			ret = 0;
			ClearPageLRU(page);
1043 1044

			del_page_from_lru_list(zone, page, lru);
1045 1046 1047 1048 1049 1050
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

L
Linus Torvalds 已提交
1051
/*
A
Andrew Morton 已提交
1052 1053
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1054
 */
A
Andrew Morton 已提交
1055
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1056 1057
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1058 1059 1060
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1061
	unsigned long nr_scanned = 0;
1062
	unsigned long nr_reclaimed = 0;
1063
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1064 1065 1066 1067 1068

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1069
	do {
L
Linus Torvalds 已提交
1070
		struct page *page;
1071 1072 1073
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1074
		unsigned long nr_active;
1075
		unsigned int count[NR_LRU_LISTS] = { 0, };
R
Rik van Riel 已提交
1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088
		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
1089

1090
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1091 1092 1093
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
		nr_active = clear_active_flags(&page_list, count);
1094
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1095

1096 1097 1098 1099 1100 1101 1102 1103 1104
		__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]);

1105
		if (scanning_global_lru(sc))
1106
			zone->pages_scanned += nr_scan;
K
KOSAKI Motohiro 已提交
1107 1108 1109 1110 1111 1112

		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
1113 1114
		spin_unlock_irq(&zone->lru_lock);

1115
		nr_scanned += nr_scan;
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131
		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.
			 */
1132
			nr_active = clear_active_flags(&page_list, count);
1133 1134 1135 1136 1137 1138
			count_vm_events(PGDEACTIVATE, nr_active);

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

1139
		nr_reclaimed += nr_freed;
N
Nick Piggin 已提交
1140 1141
		local_irq_disable();
		if (current_is_kswapd()) {
1142 1143
			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
			__count_vm_events(KSWAPD_STEAL, nr_freed);
1144
		} else if (scanning_global_lru(sc))
1145
			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1146

S
Shantanu Goel 已提交
1147
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1148

1149 1150 1151
		if (nr_taken == 0)
			goto done;

N
Nick Piggin 已提交
1152
		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1153 1154 1155 1156
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1157
			int lru;
L
Linus Torvalds 已提交
1158
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1159
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1160
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1161 1162 1163 1164 1165 1166 1167 1168 1169
			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
1170
			if (PageActive(page)) {
1171
				int file = !!page_is_file_cache(page);
1172
				reclaim_stat->recent_rotated[file]++;
1173
			}
L
Linus Torvalds 已提交
1174 1175 1176 1177 1178 1179
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
1180
  	} while (nr_scanned < max_scan);
1181
	spin_unlock(&zone->lru_lock);
L
Linus Torvalds 已提交
1182
done:
1183
	local_irq_enable();
L
Linus Torvalds 已提交
1184
	pagevec_release(&pvec);
1185
	return nr_reclaimed;
L
Linus Torvalds 已提交
1186 1187
}

1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201
/*
 * 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
1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218
/*
 * 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.
 */
1219 1220


A
Andrew Morton 已提交
1221
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1222
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1223
{
1224
	unsigned long pgmoved;
L
Linus Torvalds 已提交
1225
	int pgdeactivate = 0;
1226
	unsigned long pgscanned;
L
Linus Torvalds 已提交
1227
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1228
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1229 1230
	struct page *page;
	struct pagevec pvec;
1231
	enum lru_list lru;
1232
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
L
Linus Torvalds 已提交
1233 1234 1235

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1236 1237
	pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
					ISOLATE_ACTIVE, zone,
1238
					sc->mem_cgroup, 1, file);
1239 1240 1241 1242
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1243
	if (scanning_global_lru(sc)) {
1244
		zone->pages_scanned += pgscanned;
1245
	}
K
KOSAKI Motohiro 已提交
1246
	reclaim_stat->recent_scanned[!!file] += pgmoved;
1247

1248 1249 1250 1251
	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
1252 1253
	spin_unlock_irq(&zone->lru_lock);

1254
	pgmoved = 0;
L
Linus Torvalds 已提交
1255 1256 1257 1258
	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1259

L
Lee Schermerhorn 已提交
1260 1261 1262 1263 1264
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1265 1266 1267 1268 1269
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
		    page_referenced(page, 0, sc->mem_cgroup))
			pgmoved++;

L
Linus Torvalds 已提交
1270 1271 1272
		list_add(&page->lru, &l_inactive);
	}

1273 1274 1275 1276 1277 1278
	/*
	 * Move the pages to the [file or anon] inactive list.
	 */
	pagevec_init(&pvec, 1);
	lru = LRU_BASE + file * LRU_FILE;

1279
	spin_lock_irq(&zone->lru_lock);
1280
	/*
1281 1282 1283 1284 1285
	 * 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
1286
	reclaim_stat->recent_rotated[!!file] += pgmoved;
1287

1288
	pgmoved = 0;
L
Linus Torvalds 已提交
1289 1290 1291
	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
1292
		VM_BUG_ON(PageLRU(page));
N
Nick Piggin 已提交
1293
		SetPageLRU(page);
N
Nick Piggin 已提交
1294
		VM_BUG_ON(!PageActive(page));
N
Nick Piggin 已提交
1295 1296
		ClearPageActive(page);

1297
		list_move(&page->lru, &zone->lru[lru].list);
K
KAMEZAWA Hiroyuki 已提交
1298
		mem_cgroup_add_lru_list(page, lru);
L
Linus Torvalds 已提交
1299 1300
		pgmoved++;
		if (!pagevec_add(&pvec, page)) {
1301
			__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1302 1303 1304 1305 1306 1307 1308 1309 1310
			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);
		}
	}
1311
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
L
Linus Torvalds 已提交
1312
	pgdeactivate += pgmoved;
1313 1314 1315
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
	__count_vm_events(PGDEACTIVATE, pgdeactivate);
	spin_unlock_irq(&zone->lru_lock);
1316 1317
	if (buffer_heads_over_limit)
		pagevec_strip(&pvec);
N
Nick Piggin 已提交
1318
	pagevec_release(&pvec);
L
Linus Torvalds 已提交
1319 1320
}

1321
static int inactive_anon_is_low_global(struct zone *zone)
1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333
{
	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;
}

1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345
/**
 * 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;

1346
	if (scanning_global_lru(sc))
1347 1348
		low = inactive_anon_is_low_global(zone);
	else
1349
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1350 1351 1352
	return low;
}

1353
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1354 1355
	struct zone *zone, struct scan_control *sc, int priority)
{
1356 1357
	int file = is_file_lru(lru);

1358 1359 1360 1361 1362
	if (lru == LRU_ACTIVE_FILE) {
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
		return 0;
	}

1363
	if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1364
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1365 1366
		return 0;
	}
R
Rik van Riel 已提交
1367
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384
}

/*
 * 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;
1385
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1386 1387

	/* If we have no swap space, do not bother scanning anon pages. */
1388
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
1389 1390 1391 1392 1393
		percent[0] = 0;
		percent[1] = 100;
		return;
	}

1394 1395 1396 1397
	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);
1398

1399
	if (scanning_global_lru(sc)) {
1400 1401 1402 1403 1404 1405 1406 1407
		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;
		}
1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420
	}

	/*
	 * 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]
	 */
1421
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1422
		spin_lock_irq(&zone->lru_lock);
1423 1424
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1425 1426 1427
		spin_unlock_irq(&zone->lru_lock);
	}

1428
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1429
		spin_lock_irq(&zone->lru_lock);
1430 1431
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442
		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;

	/*
1443 1444 1445
	 * 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.
1446
	 */
1447 1448
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1449

1450 1451
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1452 1453 1454 1455

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1456 1457
}

1458

L
Linus Torvalds 已提交
1459 1460 1461
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1462
static void shrink_zone(int priority, struct zone *zone,
1463
				struct scan_control *sc)
L
Linus Torvalds 已提交
1464
{
1465
	unsigned long nr[NR_LRU_LISTS];
1466
	unsigned long nr_to_scan;
1467
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1468
	enum lru_list l;
1469 1470
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
L
Linus Torvalds 已提交
1471

1472 1473
	get_scan_ratio(zone, sc, percent);

L
Lee Schermerhorn 已提交
1474
	for_each_evictable_lru(l) {
1475
		int file = is_file_lru(l);
1476
		unsigned long scan;
1477

1478
		scan = zone_nr_pages(zone, sc, l);
1479 1480 1481 1482
		if (priority) {
			scan >>= priority;
			scan = (scan * percent[file]) / 100;
		}
1483
		if (scanning_global_lru(sc)) {
1484
			zone->lru[l].nr_scan += scan;
1485
			nr[l] = zone->lru[l].nr_scan;
1486
			if (nr[l] >= swap_cluster_max)
1487 1488 1489
				zone->lru[l].nr_scan = 0;
			else
				nr[l] = 0;
1490 1491
		} else
			nr[l] = scan;
1492
	}
L
Linus Torvalds 已提交
1493

1494 1495
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1496
		for_each_evictable_lru(l) {
1497
			if (nr[l]) {
1498
				nr_to_scan = min(nr[l], swap_cluster_max);
1499
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1500

1501 1502
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1503
			}
L
Linus Torvalds 已提交
1504
		}
1505 1506 1507 1508 1509 1510 1511 1512
		/*
		 * 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.
		 */
1513
		if (nr_reclaimed > swap_cluster_max &&
1514 1515
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1516 1517
	}

1518 1519
	sc->nr_reclaimed = nr_reclaimed;

1520 1521 1522 1523
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1524
	if (inactive_anon_is_low(zone, sc))
1525 1526
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1527
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543
}

/*
 * 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.
 */
1544
static void shrink_zones(int priority, struct zonelist *zonelist,
1545
					struct scan_control *sc)
L
Linus Torvalds 已提交
1546
{
1547
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1548
	struct zoneref *z;
1549
	struct zone *zone;
1550

1551
	sc->all_unreclaimable = 1;
1552 1553
	for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
					sc->nodemask) {
1554
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1555
			continue;
1556 1557 1558 1559
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1560
		if (scanning_global_lru(sc)) {
1561 1562 1563
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1564

1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
			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);
		}
1578

1579
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1580 1581
	}
}
1582

L
Linus Torvalds 已提交
1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594
/*
 * 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.
1595 1596 1597
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1598
 */
1599
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1600
					struct scan_control *sc)
L
Linus Torvalds 已提交
1601 1602
{
	int priority;
1603
	unsigned long ret = 0;
1604
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1605 1606
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1607
	struct zoneref *z;
1608
	struct zone *zone;
1609
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1610

1611 1612
	delayacct_freepages_start();

1613
	if (scanning_global_lru(sc))
1614 1615 1616 1617
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
1618
	if (scanning_global_lru(sc)) {
1619
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1620

1621 1622
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1623

1624
			lru_pages += zone_lru_pages(zone);
1625
		}
L
Linus Torvalds 已提交
1626 1627 1628
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1629
		sc->nr_scanned = 0;
1630 1631
		if (!priority)
			disable_swap_token();
1632
		shrink_zones(priority, zonelist, sc);
1633 1634 1635 1636
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1637
		if (scanning_global_lru(sc)) {
1638
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1639
			if (reclaim_state) {
1640
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1641 1642
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1643
		}
1644
		total_scanned += sc->nr_scanned;
1645 1646
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1647 1648 1649 1650 1651 1652 1653 1654 1655 1656
			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.
		 */
1657 1658
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1659
			wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1660
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1661 1662 1663
		}

		/* Take a nap, wait for some writeback to complete */
1664
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1665
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1666
	}
1667
	/* top priority shrink_zones still had more to do? don't OOM, then */
1668
	if (!sc->all_unreclaimable && scanning_global_lru(sc))
1669
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1670
out:
1671 1672 1673 1674 1675 1676 1677 1678 1679
	/*
	 * 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
1680

1681
	if (scanning_global_lru(sc)) {
1682
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1683 1684 1685 1686 1687 1688 1689 1690

			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
1691

1692 1693
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1694 1695 1696
	return ret;
}

1697
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1698
				gfp_t gfp_mask, nodemask_t *nodemask)
1699 1700 1701 1702 1703
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
1704
		.may_unmap = 1,
1705
		.may_swap = 1,
1706 1707 1708 1709
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1710
		.nodemask = nodemask,
1711 1712
	};

1713
	return do_try_to_free_pages(zonelist, &sc);
1714 1715
}

1716
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1717

1718
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
1719 1720 1721
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
1722 1723 1724
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
1725
		.may_unmap = 1,
1726
		.may_swap = !noswap,
1727
		.swap_cluster_max = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
1728
		.swappiness = swappiness,
1729 1730 1731
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
1732
		.nodemask = NULL, /* we don't care the placement */
1733
	};
1734
	struct zonelist *zonelist;
1735

1736 1737 1738 1739
	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);
1740 1741 1742
}
#endif

L
Linus Torvalds 已提交
1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763
/*
 * 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.
 */
1764
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1765 1766 1767 1768
{
	int all_zones_ok;
	int priority;
	int i;
1769
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1770
	struct reclaim_state *reclaim_state = current->reclaim_state;
1771 1772
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
1773
		.may_unmap = 1,
1774
		.may_swap = 1,
1775 1776
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1777
		.order = order,
1778 1779
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1780
	};
1781 1782 1783 1784 1785
	/*
	 * 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
1786 1787 1788

loop_again:
	total_scanned = 0;
1789
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1790
	sc.may_writepage = !laptop_mode;
1791
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1792

1793 1794
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1795 1796 1797 1798 1799

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

1800 1801 1802 1803
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1804 1805
		all_zones_ok = 1;

1806 1807 1808 1809 1810 1811
		/*
		 * 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
1812

1813 1814
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1815

1816 1817
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1818
				continue;
L
Linus Torvalds 已提交
1819

1820 1821 1822 1823
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
1824
			if (inactive_anon_is_low(zone, &sc))
1825 1826 1827
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

1828 1829 1830
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       0, 0)) {
				end_zone = i;
A
Andrew Morton 已提交
1831
				break;
L
Linus Torvalds 已提交
1832 1833
			}
		}
A
Andrew Morton 已提交
1834 1835 1836
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1837 1838 1839
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1840
			lru_pages += zone_lru_pages(zone);
L
Linus Torvalds 已提交
1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853
		}

		/*
		 * 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;
1854
			int nr_slab;
L
Linus Torvalds 已提交
1855

1856
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
1857 1858
				continue;

1859 1860
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
1861 1862
				continue;

1863 1864 1865
			if (!zone_watermark_ok(zone, order, zone->pages_high,
					       end_zone, 0))
				all_zones_ok = 0;
1866
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
1867
			sc.nr_scanned = 0;
1868
			note_zone_scanning_priority(zone, priority);
1869 1870 1871 1872 1873 1874
			/*
			 * 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))
1875
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
1876
			reclaim_state->reclaimed_slab = 0;
1877 1878
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
1879
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
1880
			total_scanned += sc.nr_scanned;
1881
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
1882
				continue;
1883
			if (nr_slab == 0 && zone->pages_scanned >=
1884
						(zone_lru_pages(zone) * 6))
1885 1886
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
1887 1888 1889 1890 1891 1892
			/*
			 * 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 &&
1893
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
1894 1895 1896 1897 1898 1899 1900 1901
				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.
		 */
1902
		if (total_scanned && priority < DEF_PRIORITY - 2)
1903
			congestion_wait(WRITE, HZ/10);
L
Linus Torvalds 已提交
1904 1905 1906 1907 1908 1909 1910

		/*
		 * 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.
		 */
1911
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
1912 1913 1914
			break;
	}
out:
1915 1916 1917 1918 1919
	/*
	 * 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
1920 1921 1922
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

1923
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
1924 1925 1926
	}
	if (!all_zones_ok) {
		cond_resched();
1927 1928 1929

		try_to_freeze();

1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946
		/*
		 * 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
1947 1948 1949
		goto loop_again;
	}

1950
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
1951 1952 1953 1954
}

/*
 * The background pageout daemon, started as a kernel thread
1955
 * from the init process.
L
Linus Torvalds 已提交
1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974
 *
 * 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,
	};
1975
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
1976

1977 1978
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
1979
	if (!cpumask_empty(cpumask))
1980
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
	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).
	 */
1995
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1996
	set_freezable();
L
Linus Torvalds 已提交
1997 1998 1999 2000

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
2001

L
Linus Torvalds 已提交
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
		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 {
2012 2013 2014
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
2015 2016 2017 2018
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2019 2020 2021 2022 2023 2024
		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
2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
	}
	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;

2036
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2037 2038 2039
		return;

	pgdat = zone->zone_pgdat;
R
Rohit Seth 已提交
2040
	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
L
Linus Torvalds 已提交
2041 2042 2043
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2044
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2045
		return;
2046
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2047
		return;
2048
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2049 2050
}

2051 2052 2053 2054 2055 2056 2057 2058
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
2059 2060
#ifdef CONFIG_PM
/*
2061
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
2062
 * from LRU lists system-wide, for given pass and priority.
2063 2064 2065
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
2066
static void shrink_all_zones(unsigned long nr_pages, int prio,
2067
				      int pass, struct scan_control *sc)
2068 2069
{
	struct zone *zone;
2070
	unsigned long nr_reclaimed = 0;
2071

2072
	for_each_populated_zone(zone) {
2073
		enum lru_list l;
2074

2075
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2076 2077
			continue;

L
Lee Schermerhorn 已提交
2078
		for_each_evictable_lru(l) {
2079 2080 2081
			enum zone_stat_item ls = NR_LRU_BASE + l;
			unsigned long lru_pages = zone_page_state(zone, ls);

L
Lee Schermerhorn 已提交
2082
			/* For pass = 0, we don't shrink the active list */
2083 2084
			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
						l == LRU_ACTIVE_FILE))
2085 2086
				continue;

2087
			zone->lru[l].nr_scan += (lru_pages >> prio) + 1;
2088
			if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2089 2090
				unsigned long nr_to_scan;

2091
				zone->lru[l].nr_scan = 0;
2092
				nr_to_scan = min(nr_pages, lru_pages);
2093
				nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2094
								sc, prio);
2095
				if (nr_reclaimed >= nr_pages) {
2096
					sc->nr_reclaimed += nr_reclaimed;
2097 2098
					return;
				}
2099 2100 2101
			}
		}
	}
2102
	sc->nr_reclaimed += nr_reclaimed;
2103 2104 2105 2106 2107 2108 2109 2110 2111
}

/*
 * 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
2112
 */
2113
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2114
{
2115 2116 2117 2118 2119
	unsigned long lru_pages, nr_slab;
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2120
		.may_unmap = 0,
2121
		.may_writepage = 1,
2122
		.isolate_pages = isolate_pages_global,
2123
		.nr_reclaimed = 0,
L
Linus Torvalds 已提交
2124 2125 2126
	};

	current->reclaim_state = &reclaim_state;
2127

2128
	lru_pages = global_lru_pages();
2129
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2130 2131 2132 2133 2134
	/* 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
2135
			break;
2136

2137 2138
		sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		if (sc.nr_reclaimed >= nr_pages)
2139 2140 2141
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2142
	}
2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155

	/*
	 * 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 */
2156
		if (pass > 2)
2157
			sc.may_unmap = 1;
2158 2159

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2160
			unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2161 2162

			sc.nr_scanned = 0;
2163
			sc.swap_cluster_max = nr_to_scan;
2164 2165
			shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (sc.nr_reclaimed >= nr_pages)
2166 2167 2168
				goto out;

			reclaim_state.reclaimed_slab = 0;
2169
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2170
					global_lru_pages());
2171 2172
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
			if (sc.nr_reclaimed >= nr_pages)
2173 2174 2175
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2176
				congestion_wait(WRITE, HZ / 10);
2177
		}
2178
	}
2179 2180

	/*
2181 2182
	 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
	 * something in slab caches
2183
	 */
2184
	if (!sc.nr_reclaimed) {
2185 2186
		do {
			reclaim_state.reclaimed_slab = 0;
2187
			shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2188 2189 2190
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		} while (sc.nr_reclaimed < nr_pages &&
				reclaim_state.reclaimed_slab > 0);
2191
	}
2192

2193

2194
out:
L
Linus Torvalds 已提交
2195
	current->reclaim_state = NULL;
2196

2197
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
2198 2199 2200 2201 2202 2203 2204
}
#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. */
2205
static int __devinit cpu_callback(struct notifier_block *nfb,
2206
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2207
{
2208
	int nid;
L
Linus Torvalds 已提交
2209

2210
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2211
		for_each_node_state(nid, N_HIGH_MEMORY) {
2212
			pg_data_t *pgdat = NODE_DATA(nid);
2213 2214 2215
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2216

2217
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2218
				/* One of our CPUs online: restore mask */
2219
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2220 2221 2222 2223 2224
		}
	}
	return NOTIFY_OK;
}

2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246
/*
 * 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
2247 2248
static int __init kswapd_init(void)
{
2249
	int nid;
2250

L
Linus Torvalds 已提交
2251
	swap_setup();
2252
	for_each_node_state(nid, N_HIGH_MEMORY)
2253
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2254 2255 2256 2257 2258
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2259 2260 2261 2262 2263 2264 2265 2266 2267 2268

#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;

2269
#define RECLAIM_OFF 0
2270
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2271 2272 2273
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2274 2275 2276 2277 2278 2279 2280
/*
 * 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

2281 2282 2283 2284 2285 2286
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2287 2288 2289 2290 2291 2292
/*
 * 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;

2293 2294 2295
/*
 * Try to free up some pages from this zone through reclaim.
 */
2296
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2297
{
2298
	/* Minimum pages needed in order to stay on node */
2299
	const unsigned long nr_pages = 1 << order;
2300 2301
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2302
	int priority;
2303 2304
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2305
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2306
		.may_swap = 1,
2307 2308
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2309
		.gfp_mask = gfp_mask,
2310
		.swappiness = vm_swappiness,
2311
		.order = order,
2312
		.isolate_pages = isolate_pages_global,
2313
	};
2314
	unsigned long slab_reclaimable;
2315 2316 2317

	disable_swap_token();
	cond_resched();
2318 2319 2320 2321 2322 2323
	/*
	 * 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;
2324 2325
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2326

2327 2328 2329 2330 2331 2332 2333 2334 2335
	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 {
2336
			note_zone_scanning_priority(zone, priority);
2337
			shrink_zone(priority, zone, &sc);
2338
			priority--;
2339
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2340
	}
2341

2342 2343
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2344
		/*
2345
		 * shrink_slab() does not currently allow us to determine how
2346 2347 2348 2349
		 * 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.
2350
		 *
2351 2352
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2353
		 */
2354
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2355 2356
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2357
			;
2358 2359 2360 2361 2362

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2363
		sc.nr_reclaimed += slab_reclaimable -
2364
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2365 2366
	}

2367
	p->reclaim_state = NULL;
2368
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2369
	return sc.nr_reclaimed >= nr_pages;
2370
}
2371 2372 2373 2374

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2375
	int ret;
2376 2377

	/*
2378 2379
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2380
	 *
2381 2382 2383 2384 2385
	 * 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.
2386
	 */
2387
	if (zone_page_state(zone, NR_FILE_PAGES) -
2388 2389 2390
	    zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
	    && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
			<= zone->min_slab_pages)
2391
		return 0;
2392

2393 2394 2395
	if (zone_is_all_unreclaimable(zone))
		return 0;

2396
	/*
2397
	 * Do not scan if the allocation should not be delayed.
2398
	 */
2399
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2400 2401 2402 2403 2404 2405 2406 2407
			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.
	 */
2408
	node_id = zone_to_nid(zone);
2409
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2410
		return 0;
2411 2412 2413 2414 2415 2416 2417

	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;
2418
}
2419
#endif
L
Lee Schermerhorn 已提交
2420 2421 2422 2423 2424 2425 2426 2427

#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
2428 2429
 * 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
2430 2431
 *
 * Reasons page might not be evictable:
2432
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2433
 * (2) page is part of an mlocked VMA
2434
 *
L
Lee Schermerhorn 已提交
2435 2436 2437 2438
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2439 2440 2441
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2442 2443
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2444 2445 2446

	return 1;
}
2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466

/**
 * 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);
2467

2468 2469
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2470
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2471 2472 2473 2474 2475 2476 2477 2478
		__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
2479
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
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 2537 2538
		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);
	}

}
2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550

/**
 * 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 */
2551
static void scan_zone_unevictable_pages(struct zone *zone)
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 2591 2592
{
	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.
 */
2593
static void scan_all_zones_unevictable_pages(void)
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 2666 2667
{
	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
2668
#endif