vmscan.c 80.4 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_lru_pages(struct zone *zone,
				struct scan_control *sc, enum lru_list lru)
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{
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	if (!scanning_global_lru(sc))
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		return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);

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	return zone_page_state(zone, NR_LRU_BASE + lru);
}


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

	if (!down_read_trylock(&shrinker_rwsem))
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		return 1;	/* Assume we'll be able to shrink next time */
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	list_for_each_entry(shrinker, &shrinker_list, list) {
		unsigned long long delta;
		unsigned long total_scan;
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		unsigned long max_pass = (*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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	/*
	 * A freeable page cache page is referenced only by the caller
	 * that isolated the page, the page cache radix tree and
	 * optional buffer heads at page->private.
	 */
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	return page_count(page) - page_has_private(page) == 2;
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}

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.
	 */
	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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		swapcache_free(swap, page);
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	} else {
		__remove_from_page_cache(page);
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		spin_unlock_irq(&mapping->tree_lock);
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		mem_cgroup_uncharge_cache_page(page);
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	}

	return 1;

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

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

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/**
 * putback_lru_page - put previously isolated page onto appropriate LRU list
 * @page: page to be put back to appropriate lru list
 *
 * Add previously isolated @page to appropriate LRU list.
 * Page may still be unevictable for other reasons.
 *
 * lru_lock must not be held, interrupts must be enabled.
 */
void putback_lru_page(struct page *page)
{
	int lru;
	int active = !!TestClearPageActive(page);
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	int was_unevictable = PageUnevictable(page);
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	VM_BUG_ON(PageLRU(page));

redo:
	ClearPageUnevictable(page);

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

	/*
	 * 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 */
}

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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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	unsigned long vm_flags;
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	cond_resched();

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

		cond_resched();

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

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		if (!trylock_page(page))
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			goto keep;

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		VM_BUG_ON(PageActive(page));
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		sc->nr_scanned++;
606

N
Nick Piggin 已提交
607 608
		if (unlikely(!page_evictable(page, NULL)))
			goto cull_mlocked;
L
Lee Schermerhorn 已提交
609

610
		if (!sc->may_unmap && page_mapped(page))
611 612
			goto keep_locked;

L
Linus Torvalds 已提交
613 614 615 616
		/* Double the slab pressure for mapped and swapcache pages */
		if (page_mapped(page) || PageSwapCache(page))
			sc->nr_scanned++;

617 618 619 620 621 622 623 624 625 626 627 628 629 630
		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);
631
			else
632 633
				goto keep_locked;
		}
L
Linus Torvalds 已提交
634

635 636
		referenced = page_referenced(page, 1,
						sc->mem_cgroup, &vm_flags);
637 638 639 640 641
		/*
		 * In active use or really unfreeable?  Activate it.
		 * If page which have PG_mlocked lost isoltation race,
		 * try_to_unmap moves it to unevictable list
		 */
A
Andy Whitcroft 已提交
642
		if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
643 644
					referenced && page_mapping_inuse(page)
					&& !(vm_flags & VM_LOCKED))
L
Linus Torvalds 已提交
645 646 647 648 649 650
			goto activate_locked;

		/*
		 * Anonymous process memory has backing store?
		 * Try to allocate it some swap space here.
		 */
N
Nick Piggin 已提交
651
		if (PageAnon(page) && !PageSwapCache(page)) {
652 653
			if (!(sc->gfp_mask & __GFP_IO))
				goto keep_locked;
654
			if (!add_to_swap(page))
L
Linus Torvalds 已提交
655
				goto activate_locked;
656
			may_enter_fs = 1;
N
Nick Piggin 已提交
657
		}
L
Linus Torvalds 已提交
658 659 660 661 662 663 664 665

		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) {
666
			switch (try_to_unmap(page, TTU_UNMAP)) {
L
Linus Torvalds 已提交
667 668 669 670
			case SWAP_FAIL:
				goto activate_locked;
			case SWAP_AGAIN:
				goto keep_locked;
N
Nick Piggin 已提交
671 672
			case SWAP_MLOCK:
				goto cull_mlocked;
L
Linus Torvalds 已提交
673 674 675 676 677 678
			case SWAP_SUCCESS:
				; /* try to free the page below */
			}
		}

		if (PageDirty(page)) {
A
Andy Whitcroft 已提交
679
			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
L
Linus Torvalds 已提交
680
				goto keep_locked;
681
			if (!may_enter_fs)
L
Linus Torvalds 已提交
682
				goto keep_locked;
683
			if (!sc->may_writepage)
L
Linus Torvalds 已提交
684 685 686
				goto keep_locked;

			/* Page is dirty, try to write it out here */
687
			switch (pageout(page, mapping, sync_writeback)) {
L
Linus Torvalds 已提交
688 689 690 691 692
			case PAGE_KEEP:
				goto keep_locked;
			case PAGE_ACTIVATE:
				goto activate_locked;
			case PAGE_SUCCESS:
693
				if (PageWriteback(page) || PageDirty(page))
L
Linus Torvalds 已提交
694 695 696 697 698
					goto keep;
				/*
				 * A synchronous write - probably a ramdisk.  Go
				 * ahead and try to reclaim the page.
				 */
N
Nick Piggin 已提交
699
				if (!trylock_page(page))
L
Linus Torvalds 已提交
700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718
					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
719
		 * will do this, as well as the blockdev mapping.
L
Linus Torvalds 已提交
720 721 722 723 724 725 726 727 728 729
		 * 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.
		 */
730
		if (page_has_private(page)) {
L
Linus Torvalds 已提交
731 732
			if (!try_to_release_page(page, sc->gfp_mask))
				goto activate_locked;
N
Nick Piggin 已提交
733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748
			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
749 750
		}

N
Nick Piggin 已提交
751
		if (!mapping || !__remove_mapping(mapping, page))
752
			goto keep_locked;
L
Linus Torvalds 已提交
753

N
Nick Piggin 已提交
754 755 756 757 758 759 760 761
		/*
		 * 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
762
free_it:
763
		nr_reclaimed++;
N
Nick Piggin 已提交
764 765 766 767
		if (!pagevec_add(&freed_pvec, page)) {
			__pagevec_free(&freed_pvec);
			pagevec_reinit(&freed_pvec);
		}
L
Linus Torvalds 已提交
768 769
		continue;

N
Nick Piggin 已提交
770
cull_mlocked:
771 772
		if (PageSwapCache(page))
			try_to_free_swap(page);
N
Nick Piggin 已提交
773 774 775 776
		unlock_page(page);
		putback_lru_page(page);
		continue;

L
Linus Torvalds 已提交
777
activate_locked:
778 779
		/* Not a candidate for swapping, so reclaim swap space. */
		if (PageSwapCache(page) && vm_swap_full())
780
			try_to_free_swap(page);
L
Lee Schermerhorn 已提交
781
		VM_BUG_ON(PageActive(page));
L
Linus Torvalds 已提交
782 783 784 785 786 787
		SetPageActive(page);
		pgactivate++;
keep_locked:
		unlock_page(page);
keep:
		list_add(&page->lru, &ret_pages);
N
Nick Piggin 已提交
788
		VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
L
Linus Torvalds 已提交
789 790 791
	}
	list_splice(&ret_pages, page_list);
	if (pagevec_count(&freed_pvec))
N
Nick Piggin 已提交
792
		__pagevec_free(&freed_pvec);
793
	count_vm_events(PGACTIVATE, pgactivate);
794
	return nr_reclaimed;
L
Linus Torvalds 已提交
795 796
}

A
Andy Whitcroft 已提交
797 798 799 800 801 802 803 804 805 806 807 808 809 810 811
/* 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.
 */
812
int __isolate_lru_page(struct page *page, int mode, int file)
A
Andy Whitcroft 已提交
813 814 815 816 817 818 819 820 821 822 823 824 825 826 827
{
	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;

828
	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
829 830
		return ret;

L
Lee Schermerhorn 已提交
831 832 833 834 835 836 837 838
	/*
	 * 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
839
	ret = -EBUSY;
K
KAMEZAWA Hiroyuki 已提交
840

A
Andy Whitcroft 已提交
841 842 843 844 845 846 847 848 849 850 851 852 853
	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;
	}

	return ret;
}

L
Linus Torvalds 已提交
854 855 856 857 858 859 860 861 862 863 864 865 866 867
/*
 * 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
868 869
 * @order:	The caller's attempted allocation order
 * @mode:	One of the LRU isolation modes
870
 * @file:	True [1] if isolating file [!anon] pages
L
Linus Torvalds 已提交
871 872 873
 *
 * returns how many pages were moved onto *@dst.
 */
874 875
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
		struct list_head *src, struct list_head *dst,
876
		unsigned long *scanned, int order, int mode, int file)
L
Linus Torvalds 已提交
877
{
878
	unsigned long nr_taken = 0;
879
	unsigned long scan;
L
Linus Torvalds 已提交
880

881
	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
A
Andy Whitcroft 已提交
882 883 884 885 886 887
		struct page *page;
		unsigned long pfn;
		unsigned long end_pfn;
		unsigned long page_pfn;
		int zone_id;

L
Linus Torvalds 已提交
888 889 890
		page = lru_to_page(src);
		prefetchw_prev_lru_page(page, src, flags);

N
Nick Piggin 已提交
891
		VM_BUG_ON(!PageLRU(page));
N
Nick Piggin 已提交
892

893
		switch (__isolate_lru_page(page, mode, file)) {
A
Andy Whitcroft 已提交
894 895
		case 0:
			list_move(&page->lru, dst);
896
			mem_cgroup_del_lru(page);
897
			nr_taken++;
A
Andy Whitcroft 已提交
898 899 900 901 902
			break;

		case -EBUSY:
			/* else it is being freed elsewhere */
			list_move(&page->lru, src);
903
			mem_cgroup_rotate_lru_list(page, page_lru(page));
A
Andy Whitcroft 已提交
904
			continue;
905

A
Andy Whitcroft 已提交
906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937
		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);
938

A
Andy Whitcroft 已提交
939 940 941
			/* Check that we have not crossed a zone boundary. */
			if (unlikely(page_zone_id(cursor_page) != zone_id))
				continue;
942 943 944 945 946 947 948 949 950 951

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

952
			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
A
Andy Whitcroft 已提交
953
				list_move(&cursor_page->lru, dst);
954
				mem_cgroup_del_lru(cursor_page);
A
Andy Whitcroft 已提交
955 956 957 958
				nr_taken++;
				scan++;
			}
		}
L
Linus Torvalds 已提交
959 960 961 962 963 964
	}

	*scanned = scan;
	return nr_taken;
}

965 966 967 968 969
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,
970
					int active, int file)
971
{
972
	int lru = LRU_BASE;
973
	if (active)
974 975 976 977
		lru += LRU_ACTIVE;
	if (file)
		lru += LRU_FILE;
	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
978
								mode, file);
979 980
}

A
Andy Whitcroft 已提交
981 982 983 984
/*
 * clear_active_flags() is a helper for shrink_active_list(), clearing
 * any active bits from the pages in the list.
 */
985 986
static unsigned long clear_active_flags(struct list_head *page_list,
					unsigned int *count)
A
Andy Whitcroft 已提交
987 988
{
	int nr_active = 0;
989
	int lru;
A
Andy Whitcroft 已提交
990 991
	struct page *page;

992
	list_for_each_entry(page, page_list, lru) {
993
		lru = page_lru_base_type(page);
A
Andy Whitcroft 已提交
994
		if (PageActive(page)) {
995
			lru += LRU_ACTIVE;
A
Andy Whitcroft 已提交
996 997 998
			ClearPageActive(page);
			nr_active++;
		}
999 1000
		count[lru]++;
	}
A
Andy Whitcroft 已提交
1001 1002 1003 1004

	return nr_active;
}

1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
/**
 * 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
1016 1017 1018
 * 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.
1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038
 *
 * 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
1039
			int lru = page_lru(page);
1040 1041
			ret = 0;
			ClearPageLRU(page);
1042 1043

			del_page_from_lru_list(zone, page, lru);
1044 1045 1046 1047 1048 1049
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074
/*
 * Are there way too many processes in the direct reclaim path already?
 */
static int too_many_isolated(struct zone *zone, int file,
		struct scan_control *sc)
{
	unsigned long inactive, isolated;

	if (current_is_kswapd())
		return 0;

	if (!scanning_global_lru(sc))
		return 0;

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

	return isolated > inactive;
}

L
Linus Torvalds 已提交
1075
/*
A
Andrew Morton 已提交
1076 1077
 * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
 * of reclaimed pages
L
Linus Torvalds 已提交
1078
 */
A
Andrew Morton 已提交
1079
static unsigned long shrink_inactive_list(unsigned long max_scan,
R
Rik van Riel 已提交
1080 1081
			struct zone *zone, struct scan_control *sc,
			int priority, int file)
L
Linus Torvalds 已提交
1082 1083 1084
{
	LIST_HEAD(page_list);
	struct pagevec pvec;
1085
	unsigned long nr_scanned = 0;
1086
	unsigned long nr_reclaimed = 0;
1087
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1088 1089
	int lumpy_reclaim = 0;

1090
	while (unlikely(too_many_isolated(zone, file, sc))) {
1091
		congestion_wait(BLK_RW_ASYNC, HZ/10);
1092 1093 1094 1095 1096 1097

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

1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108
	/*
	 * 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)
		lumpy_reclaim = 1;
	else if (sc->order && priority < DEF_PRIORITY - 2)
		lumpy_reclaim = 1;
L
Linus Torvalds 已提交
1109 1110 1111 1112 1113

	pagevec_init(&pvec, 1);

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1114
	do {
L
Linus Torvalds 已提交
1115
		struct page *page;
1116 1117 1118
		unsigned long nr_taken;
		unsigned long nr_scan;
		unsigned long nr_freed;
A
Andy Whitcroft 已提交
1119
		unsigned long nr_active;
1120
		unsigned int count[NR_LRU_LISTS] = { 0, };
1121
		int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
K
KOSAKI Motohiro 已提交
1122 1123
		unsigned long nr_anon;
		unsigned long nr_file;
L
Linus Torvalds 已提交
1124

1125
		nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1126 1127
			     &page_list, &nr_scan, sc->order, mode,
				zone, sc->mem_cgroup, 0, file);
1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141

		if (scanning_global_lru(sc)) {
			zone->pages_scanned += nr_scan;
			if (current_is_kswapd())
				__count_zone_vm_events(PGSCAN_KSWAPD, zone,
						       nr_scan);
			else
				__count_zone_vm_events(PGSCAN_DIRECT, zone,
						       nr_scan);
		}

		if (nr_taken == 0)
			goto done;

1142
		nr_active = clear_active_flags(&page_list, count);
1143
		__count_vm_events(PGDEACTIVATE, nr_active);
A
Andy Whitcroft 已提交
1144

1145 1146 1147 1148 1149 1150 1151 1152 1153
		__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]);

K
KOSAKI Motohiro 已提交
1154 1155 1156 1157
		nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
		nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
		__mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
		__mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
K
KOSAKI Motohiro 已提交
1158 1159 1160 1161 1162 1163

		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
1164 1165
		spin_unlock_irq(&zone->lru_lock);

1166
		nr_scanned += nr_scan;
1167 1168 1169 1170 1171 1172 1173 1174 1175
		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() &&
1176
		    lumpy_reclaim) {
1177
			congestion_wait(BLK_RW_ASYNC, HZ/10);
1178 1179 1180 1181 1182

			/*
			 * The attempt at page out may have made some
			 * of the pages active, mark them inactive again.
			 */
1183
			nr_active = clear_active_flags(&page_list, count);
1184 1185 1186 1187 1188 1189
			count_vm_events(PGDEACTIVATE, nr_active);

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

1190
		nr_reclaimed += nr_freed;
1191

N
Nick Piggin 已提交
1192
		local_irq_disable();
1193
		if (current_is_kswapd())
1194
			__count_vm_events(KSWAPD_STEAL, nr_freed);
S
Shantanu Goel 已提交
1195
		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
N
Nick Piggin 已提交
1196 1197

		spin_lock(&zone->lru_lock);
L
Linus Torvalds 已提交
1198 1199 1200 1201
		/*
		 * Put back any unfreeable pages.
		 */
		while (!list_empty(&page_list)) {
L
Lee Schermerhorn 已提交
1202
			int lru;
L
Linus Torvalds 已提交
1203
			page = lru_to_page(&page_list);
N
Nick Piggin 已提交
1204
			VM_BUG_ON(PageLRU(page));
L
Linus Torvalds 已提交
1205
			list_del(&page->lru);
L
Lee Schermerhorn 已提交
1206 1207 1208 1209 1210 1211 1212 1213 1214
			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);
1215
			if (is_active_lru(lru)) {
1216
				int file = is_file_lru(lru);
1217
				reclaim_stat->recent_rotated[file]++;
1218
			}
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223 1224
			if (!pagevec_add(&pvec, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_release(&pvec);
				spin_lock_irq(&zone->lru_lock);
			}
		}
K
KOSAKI Motohiro 已提交
1225 1226 1227
		__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
		__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);

1228
  	} while (nr_scanned < max_scan);
1229

L
Linus Torvalds 已提交
1230
done:
1231
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1232
	pagevec_release(&pvec);
1233
	return nr_reclaimed;
L
Linus Torvalds 已提交
1234 1235
}

1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249
/*
 * 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
1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266
/*
 * 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.
 */
1267

1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299
static void move_active_pages_to_lru(struct zone *zone,
				     struct list_head *list,
				     enum lru_list lru)
{
	unsigned long pgmoved = 0;
	struct pagevec pvec;
	struct page *page;

	pagevec_init(&pvec, 1);

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

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

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

		if (!pagevec_add(&pvec, page) || list_empty(list)) {
			spin_unlock_irq(&zone->lru_lock);
			if (buffer_heads_over_limit)
				pagevec_strip(&pvec);
			__pagevec_release(&pvec);
			spin_lock_irq(&zone->lru_lock);
		}
	}
	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
	if (!is_active_lru(lru))
		__count_vm_events(PGDEACTIVATE, pgmoved);
}
1300

A
Andrew Morton 已提交
1301
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1302
			struct scan_control *sc, int priority, int file)
L
Linus Torvalds 已提交
1303
{
1304
	unsigned long nr_taken;
1305
	unsigned long pgscanned;
1306
	unsigned long vm_flags;
L
Linus Torvalds 已提交
1307
	LIST_HEAD(l_hold);	/* The pages which were snipped off */
1308
	LIST_HEAD(l_active);
1309
	LIST_HEAD(l_inactive);
L
Linus Torvalds 已提交
1310
	struct page *page;
1311
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1312
	unsigned long nr_rotated = 0;
L
Linus Torvalds 已提交
1313 1314 1315

	lru_add_drain();
	spin_lock_irq(&zone->lru_lock);
1316
	nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1317
					ISOLATE_ACTIVE, zone,
1318
					sc->mem_cgroup, 1, file);
1319 1320 1321 1322
	/*
	 * zone->pages_scanned is used for detect zone's oom
	 * mem_cgroup remembers nr_scan by itself.
	 */
1323
	if (scanning_global_lru(sc)) {
1324
		zone->pages_scanned += pgscanned;
1325
	}
1326
	reclaim_stat->recent_scanned[file] += nr_taken;
1327

1328
	__count_zone_vm_events(PGREFILL, zone, pgscanned);
1329
	if (file)
1330
		__mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1331
	else
1332
		__mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
K
KOSAKI Motohiro 已提交
1333
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
L
Linus Torvalds 已提交
1334 1335 1336 1337 1338 1339
	spin_unlock_irq(&zone->lru_lock);

	while (!list_empty(&l_hold)) {
		cond_resched();
		page = lru_to_page(&l_hold);
		list_del(&page->lru);
1340

L
Lee Schermerhorn 已提交
1341 1342 1343 1344 1345
		if (unlikely(!page_evictable(page, NULL))) {
			putback_lru_page(page);
			continue;
		}

1346 1347
		/* page_referenced clears PageReferenced */
		if (page_mapping_inuse(page) &&
1348
		    page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1349
			nr_rotated++;
1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363
			/*
			 * Identify referenced, file-backed active pages and
			 * give them one more trip around the active list. So
			 * that executable code get better chances to stay in
			 * memory under moderate memory pressure.  Anon pages
			 * are not likely to be evicted by use-once streaming
			 * IO, plus JVM can create lots of anon VM_EXEC pages,
			 * so we ignore them here.
			 */
			if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
				list_add(&page->lru, &l_active);
				continue;
			}
		}
1364

1365
		ClearPageActive(page);	/* we are de-activating */
L
Linus Torvalds 已提交
1366 1367 1368
		list_add(&page->lru, &l_inactive);
	}

1369
	/*
1370
	 * Move pages back to the lru list.
1371
	 */
1372
	spin_lock_irq(&zone->lru_lock);
1373
	/*
1374 1375 1376 1377
	 * Count referenced pages from currently used mappings as rotated,
	 * even though only some of them are actually re-activated.  This
	 * helps balance scan pressure between file and anonymous pages in
	 * get_scan_ratio.
1378
	 */
1379
	reclaim_stat->recent_rotated[file] += nr_rotated;
1380

1381 1382 1383 1384
	move_active_pages_to_lru(zone, &l_active,
						LRU_ACTIVE + file * LRU_FILE);
	move_active_pages_to_lru(zone, &l_inactive,
						LRU_BASE   + file * LRU_FILE);
K
KOSAKI Motohiro 已提交
1385
	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1386
	spin_unlock_irq(&zone->lru_lock);
L
Linus Torvalds 已提交
1387 1388
}

1389
static int inactive_anon_is_low_global(struct zone *zone)
1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401
{
	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;
}

1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413
/**
 * 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;

1414
	if (scanning_global_lru(sc))
1415 1416
		low = inactive_anon_is_low_global(zone);
	else
1417
		low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1418 1419 1420
	return low;
}

1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456
static int inactive_file_is_low_global(struct zone *zone)
{
	unsigned long active, inactive;

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

	return (active > inactive);
}

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

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

1457
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1458 1459
	struct zone *zone, struct scan_control *sc, int priority)
{
1460 1461
	int file = is_file_lru(lru);

1462
	if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
1463 1464 1465 1466
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
		return 0;
	}

1467
	if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1468
		shrink_active_list(nr_to_scan, zone, sc, priority, file);
1469 1470
		return 0;
	}
R
Rik van Riel 已提交
1471
	return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488
}

/*
 * 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;
1489
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1490

1491 1492 1493 1494
	anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1495

1496
	if (scanning_global_lru(sc)) {
1497 1498 1499
		free  = zone_page_state(zone, NR_FREE_PAGES);
		/* If we have very few page cache pages,
		   force-scan anon pages. */
1500
		if (unlikely(file + free <= high_wmark_pages(zone))) {
1501 1502 1503 1504
			percent[0] = 100;
			percent[1] = 0;
			return;
		}
1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517
	}

	/*
	 * 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]
	 */
1518
	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1519
		spin_lock_irq(&zone->lru_lock);
1520 1521
		reclaim_stat->recent_scanned[0] /= 2;
		reclaim_stat->recent_rotated[0] /= 2;
1522 1523 1524
		spin_unlock_irq(&zone->lru_lock);
	}

1525
	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1526
		spin_lock_irq(&zone->lru_lock);
1527 1528
		reclaim_stat->recent_scanned[1] /= 2;
		reclaim_stat->recent_rotated[1] /= 2;
1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539
		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;

	/*
1540 1541 1542
	 * 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.
1543
	 */
1544 1545
	ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
	ap /= reclaim_stat->recent_rotated[0] + 1;
1546

1547 1548
	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
	fp /= reclaim_stat->recent_rotated[1] + 1;
1549 1550 1551 1552

	/* Normalize to percentages */
	percent[0] = 100 * ap / (ap + fp + 1);
	percent[1] = 100 - percent[0];
1553 1554
}

1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574
/*
 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
 * until we collected @swap_cluster_max pages to scan.
 */
static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
				       unsigned long *nr_saved_scan,
				       unsigned long swap_cluster_max)
{
	unsigned long nr;

	*nr_saved_scan += nr_to_scan;
	nr = *nr_saved_scan;

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

	return nr;
}
1575

L
Linus Torvalds 已提交
1576 1577 1578
/*
 * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
 */
1579
static void shrink_zone(int priority, struct zone *zone,
1580
				struct scan_control *sc)
L
Linus Torvalds 已提交
1581
{
1582
	unsigned long nr[NR_LRU_LISTS];
1583
	unsigned long nr_to_scan;
1584
	unsigned long percent[2];	/* anon @ 0; file @ 1 */
1585
	enum lru_list l;
1586 1587
	unsigned long nr_reclaimed = sc->nr_reclaimed;
	unsigned long swap_cluster_max = sc->swap_cluster_max;
1588
	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1589
	int noswap = 0;
L
Linus Torvalds 已提交
1590

1591 1592 1593 1594 1595 1596 1597
	/* If we have no swap space, do not bother scanning anon pages. */
	if (!sc->may_swap || (nr_swap_pages <= 0)) {
		noswap = 1;
		percent[0] = 0;
		percent[1] = 100;
	} else
		get_scan_ratio(zone, sc, percent);
1598

L
Lee Schermerhorn 已提交
1599
	for_each_evictable_lru(l) {
1600
		int file = is_file_lru(l);
1601
		unsigned long scan;
1602

1603
		scan = zone_nr_lru_pages(zone, sc, l);
1604
		if (priority || noswap) {
1605 1606 1607
			scan >>= priority;
			scan = (scan * percent[file]) / 100;
		}
1608 1609 1610
		nr[l] = nr_scan_try_batch(scan,
					  &reclaim_stat->nr_saved_scan[l],
					  swap_cluster_max);
1611
	}
L
Linus Torvalds 已提交
1612

1613 1614
	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
					nr[LRU_INACTIVE_FILE]) {
L
Lee Schermerhorn 已提交
1615
		for_each_evictable_lru(l) {
1616
			if (nr[l]) {
1617
				nr_to_scan = min(nr[l], swap_cluster_max);
1618
				nr[l] -= nr_to_scan;
L
Linus Torvalds 已提交
1619

1620 1621
				nr_reclaimed += shrink_list(l, nr_to_scan,
							    zone, sc, priority);
1622
			}
L
Linus Torvalds 已提交
1623
		}
1624 1625 1626 1627 1628 1629 1630 1631
		/*
		 * 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.
		 */
1632
		if (nr_reclaimed > swap_cluster_max &&
1633 1634
			priority < DEF_PRIORITY && !current_is_kswapd())
			break;
L
Linus Torvalds 已提交
1635 1636
	}

1637 1638
	sc->nr_reclaimed = nr_reclaimed;

1639 1640 1641 1642
	/*
	 * Even if we did not try to evict anon pages at all, we want to
	 * rebalance the anon lru active/inactive ratio.
	 */
1643
	if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1644 1645
		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);

1646
	throttle_vm_writeout(sc->gfp_mask);
L
Linus Torvalds 已提交
1647 1648 1649 1650 1651 1652 1653
}

/*
 * 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.
 *
1654 1655
 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
 * Because:
L
Linus Torvalds 已提交
1656 1657
 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
 *    allocation or
1658 1659 1660
 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
 *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
 *    zone defense algorithm.
L
Linus Torvalds 已提交
1661 1662 1663 1664
 *
 * If a zone is deemed to be full of pinned pages then just give it a light
 * scan then give up on it.
 */
1665
static void shrink_zones(int priority, struct zonelist *zonelist,
1666
					struct scan_control *sc)
L
Linus Torvalds 已提交
1667
{
1668
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1669
	struct zoneref *z;
1670
	struct zone *zone;
1671

1672
	sc->all_unreclaimable = 1;
1673 1674
	for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
					sc->nodemask) {
1675
		if (!populated_zone(zone))
L
Linus Torvalds 已提交
1676
			continue;
1677 1678 1679 1680
		/*
		 * Take care memory controller reclaiming has small influence
		 * to global LRU.
		 */
1681
		if (scanning_global_lru(sc)) {
1682 1683 1684
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
			note_zone_scanning_priority(zone, priority);
L
Linus Torvalds 已提交
1685

1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698
			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);
		}
1699

1700
		shrink_zone(priority, zone, sc);
L
Linus Torvalds 已提交
1701 1702
	}
}
1703

L
Linus Torvalds 已提交
1704 1705 1706 1707 1708 1709 1710 1711
/*
 * 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
1712 1713 1714 1715
 * caller can't do much about.  We kick the writeback threads and take explicit
 * naps in the hope that some of these pages can be written.  But if the
 * allocating task holds filesystem locks which prevent writeout this might not
 * work, and the allocation attempt will fail.
1716 1717 1718
 *
 * returns:	0, if no pages reclaimed
 * 		else, the number of pages reclaimed
L
Linus Torvalds 已提交
1719
 */
1720
static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1721
					struct scan_control *sc)
L
Linus Torvalds 已提交
1722 1723
{
	int priority;
1724
	unsigned long ret = 0;
1725
	unsigned long total_scanned = 0;
L
Linus Torvalds 已提交
1726 1727
	struct reclaim_state *reclaim_state = current->reclaim_state;
	unsigned long lru_pages = 0;
1728
	struct zoneref *z;
1729
	struct zone *zone;
1730
	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
L
Linus Torvalds 已提交
1731

1732 1733
	delayacct_freepages_start();

1734
	if (scanning_global_lru(sc))
1735 1736 1737 1738
		count_vm_event(ALLOCSTALL);
	/*
	 * mem_cgroup will not do shrink_slab.
	 */
1739
	if (scanning_global_lru(sc)) {
1740
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
L
Linus Torvalds 已提交
1741

1742 1743
			if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
				continue;
L
Linus Torvalds 已提交
1744

1745
			lru_pages += zone_reclaimable_pages(zone);
1746
		}
L
Linus Torvalds 已提交
1747 1748 1749
	}

	for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1750
		sc->nr_scanned = 0;
1751 1752
		if (!priority)
			disable_swap_token();
1753
		shrink_zones(priority, zonelist, sc);
1754 1755 1756 1757
		/*
		 * Don't shrink slabs when reclaiming memory from
		 * over limit cgroups
		 */
1758
		if (scanning_global_lru(sc)) {
1759
			shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1760
			if (reclaim_state) {
1761
				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1762 1763
				reclaim_state->reclaimed_slab = 0;
			}
L
Linus Torvalds 已提交
1764
		}
1765
		total_scanned += sc->nr_scanned;
1766 1767
		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
			ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1768 1769 1770 1771 1772 1773 1774 1775 1776 1777
			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.
		 */
1778 1779
		if (total_scanned > sc->swap_cluster_max +
					sc->swap_cluster_max / 2) {
1780
			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1781
			sc->may_writepage = 1;
L
Linus Torvalds 已提交
1782 1783 1784
		}

		/* Take a nap, wait for some writeback to complete */
1785
		if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1786
			congestion_wait(BLK_RW_ASYNC, HZ/10);
L
Linus Torvalds 已提交
1787
	}
1788
	/* top priority shrink_zones still had more to do? don't OOM, then */
1789
	if (!sc->all_unreclaimable && scanning_global_lru(sc))
1790
		ret = sc->nr_reclaimed;
L
Linus Torvalds 已提交
1791
out:
1792 1793 1794 1795 1796 1797 1798 1799 1800
	/*
	 * 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
1801

1802
	if (scanning_global_lru(sc)) {
1803
		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1804 1805 1806 1807 1808 1809 1810 1811

			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
1812

1813 1814
	delayacct_freepages_end();

L
Linus Torvalds 已提交
1815 1816 1817
	return ret;
}

1818
unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1819
				gfp_t gfp_mask, nodemask_t *nodemask)
1820 1821 1822 1823 1824
{
	struct scan_control sc = {
		.gfp_mask = gfp_mask,
		.may_writepage = !laptop_mode,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
1825
		.may_unmap = 1,
1826
		.may_swap = 1,
1827 1828 1829 1830
		.swappiness = vm_swappiness,
		.order = order,
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1831
		.nodemask = nodemask,
1832 1833
	};

1834
	return do_try_to_free_pages(zonelist, &sc);
1835 1836
}

1837
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1838

1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						unsigned int swappiness,
						struct zone *zone, int nid)
{
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
		.may_unmap = 1,
		.may_swap = !noswap,
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = swappiness,
		.order = 0,
		.mem_cgroup = mem,
		.isolate_pages = mem_cgroup_isolate_pages,
	};
	nodemask_t nm  = nodemask_of_node(nid);

	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
	sc.nodemask = &nm;
	sc.nr_reclaimed = 0;
	sc.nr_scanned = 0;
	/*
	 * NOTE: Although we can get the priority field, using it
	 * here is not a good idea, since it limits the pages we can scan.
	 * if we don't reclaim here, the shrink_zone from balance_pgdat
	 * will pick up pages from other mem cgroup's as well. We hack
	 * the priority and make it zero.
	 */
	shrink_zone(0, zone, &sc);
	return sc.nr_reclaimed;
}

1872
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
K
KOSAKI Motohiro 已提交
1873 1874 1875
					   gfp_t gfp_mask,
					   bool noswap,
					   unsigned int swappiness)
1876
{
1877
	struct zonelist *zonelist;
1878 1879
	struct scan_control sc = {
		.may_writepage = !laptop_mode,
1880
		.may_unmap = 1,
1881
		.may_swap = !noswap,
1882
		.swap_cluster_max = SWAP_CLUSTER_MAX,
K
KOSAKI Motohiro 已提交
1883
		.swappiness = swappiness,
1884 1885 1886
		.order = 0,
		.mem_cgroup = mem_cont,
		.isolate_pages = mem_cgroup_isolate_pages,
1887
		.nodemask = NULL, /* we don't care the placement */
1888 1889
	};

1890 1891 1892 1893
	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);
1894 1895 1896
}
#endif

L
Linus Torvalds 已提交
1897 1898
/*
 * For kswapd, balance_pgdat() will work across all this node's zones until
1899
 * they are all at high_wmark_pages(zone).
L
Linus Torvalds 已提交
1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911
 *
 * 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
1912 1913 1914 1915 1916
 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
 * lower zones regardless of the number of free pages in the lower zones. This
 * interoperates with the page allocator fallback scheme to ensure that aging
 * of pages is balanced across the zones.
L
Linus Torvalds 已提交
1917
 */
1918
static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
L
Linus Torvalds 已提交
1919 1920 1921 1922
{
	int all_zones_ok;
	int priority;
	int i;
1923
	unsigned long total_scanned;
L
Linus Torvalds 已提交
1924
	struct reclaim_state *reclaim_state = current->reclaim_state;
1925 1926
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
1927
		.may_unmap = 1,
1928
		.may_swap = 1,
1929 1930
		.swap_cluster_max = SWAP_CLUSTER_MAX,
		.swappiness = vm_swappiness,
A
Andy Whitcroft 已提交
1931
		.order = order,
1932 1933
		.mem_cgroup = NULL,
		.isolate_pages = isolate_pages_global,
1934
	};
1935 1936
	/*
	 * temp_priority is used to remember the scanning priority at which
1937 1938
	 * this zone was successfully refilled to
	 * free_pages == high_wmark_pages(zone).
1939 1940
	 */
	int temp_priority[MAX_NR_ZONES];
L
Linus Torvalds 已提交
1941 1942 1943

loop_again:
	total_scanned = 0;
1944
	sc.nr_reclaimed = 0;
C
Christoph Lameter 已提交
1945
	sc.may_writepage = !laptop_mode;
1946
	count_vm_event(PAGEOUTRUN);
L
Linus Torvalds 已提交
1947

1948 1949
	for (i = 0; i < pgdat->nr_zones; i++)
		temp_priority[i] = DEF_PRIORITY;
L
Linus Torvalds 已提交
1950 1951 1952 1953 1954

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

1955 1956 1957 1958
		/* The swap token gets in the way of swapout... */
		if (!priority)
			disable_swap_token();

L
Linus Torvalds 已提交
1959 1960
		all_zones_ok = 1;

1961 1962 1963 1964 1965 1966
		/*
		 * 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
1967

1968 1969
			if (!populated_zone(zone))
				continue;
L
Linus Torvalds 已提交
1970

1971 1972
			if (zone_is_all_unreclaimable(zone) &&
			    priority != DEF_PRIORITY)
1973
				continue;
L
Linus Torvalds 已提交
1974

1975 1976 1977 1978
			/*
			 * Do some background aging of the anon list, to give
			 * pages a chance to be referenced before reclaiming.
			 */
1979
			if (inactive_anon_is_low(zone, &sc))
1980 1981 1982
				shrink_active_list(SWAP_CLUSTER_MAX, zone,
							&sc, priority, 0);

1983 1984
			if (!zone_watermark_ok(zone, order,
					high_wmark_pages(zone), 0, 0)) {
1985
				end_zone = i;
A
Andrew Morton 已提交
1986
				break;
L
Linus Torvalds 已提交
1987 1988
			}
		}
A
Andrew Morton 已提交
1989 1990 1991
		if (i < 0)
			goto out;

L
Linus Torvalds 已提交
1992 1993 1994
		for (i = 0; i <= end_zone; i++) {
			struct zone *zone = pgdat->node_zones + i;

1995
			lru_pages += zone_reclaimable_pages(zone);
L
Linus Torvalds 已提交
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
		}

		/*
		 * 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;
2009
			int nr_slab;
2010
			int nid, zid;
L
Linus Torvalds 已提交
2011

2012
			if (!populated_zone(zone))
L
Linus Torvalds 已提交
2013 2014
				continue;

2015 2016
			if (zone_is_all_unreclaimable(zone) &&
					priority != DEF_PRIORITY)
L
Linus Torvalds 已提交
2017 2018
				continue;

2019 2020
			if (!zone_watermark_ok(zone, order,
					high_wmark_pages(zone), end_zone, 0))
2021
				all_zones_ok = 0;
2022
			temp_priority[i] = priority;
L
Linus Torvalds 已提交
2023
			sc.nr_scanned = 0;
2024
			note_zone_scanning_priority(zone, priority);
2025 2026 2027 2028 2029 2030 2031 2032 2033

			nid = pgdat->node_id;
			zid = zone_idx(zone);
			/*
			 * Call soft limit reclaim before calling shrink_zone.
			 * For now we ignore the return value
			 */
			mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
							nid, zid);
2034 2035 2036 2037
			/*
			 * We put equal pressure on every zone, unless one
			 * zone has way too many pages free already.
			 */
2038 2039
			if (!zone_watermark_ok(zone, order,
					8*high_wmark_pages(zone), end_zone, 0))
2040
				shrink_zone(priority, zone, &sc);
L
Linus Torvalds 已提交
2041
			reclaim_state->reclaimed_slab = 0;
2042 2043
			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
						lru_pages);
2044
			sc.nr_reclaimed += reclaim_state->reclaimed_slab;
L
Linus Torvalds 已提交
2045
			total_scanned += sc.nr_scanned;
2046
			if (zone_is_all_unreclaimable(zone))
L
Linus Torvalds 已提交
2047
				continue;
2048
			if (nr_slab == 0 && zone->pages_scanned >=
2049
					(zone_reclaimable_pages(zone) * 6))
2050 2051
					zone_set_flag(zone,
						      ZONE_ALL_UNRECLAIMABLE);
L
Linus Torvalds 已提交
2052 2053 2054 2055 2056 2057
			/*
			 * 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 &&
2058
			    total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
L
Linus Torvalds 已提交
2059 2060 2061 2062 2063 2064 2065 2066
				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.
		 */
2067
		if (total_scanned && priority < DEF_PRIORITY - 2)
2068
			congestion_wait(BLK_RW_ASYNC, HZ/10);
L
Linus Torvalds 已提交
2069 2070 2071 2072 2073 2074 2075

		/*
		 * 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.
		 */
2076
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
L
Linus Torvalds 已提交
2077 2078 2079
			break;
	}
out:
2080 2081 2082 2083 2084
	/*
	 * 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
2085 2086 2087
	for (i = 0; i < pgdat->nr_zones; i++) {
		struct zone *zone = pgdat->node_zones + i;

2088
		zone->prev_priority = temp_priority[i];
L
Linus Torvalds 已提交
2089 2090 2091
	}
	if (!all_zones_ok) {
		cond_resched();
2092 2093 2094

		try_to_freeze();

2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111
		/*
		 * 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
2112 2113 2114
		goto loop_again;
	}

2115
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
2116 2117 2118 2119
}

/*
 * The background pageout daemon, started as a kernel thread
2120
 * from the init process.
L
Linus Torvalds 已提交
2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139
 *
 * 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,
	};
2140
	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
L
Linus Torvalds 已提交
2141

2142 2143
	lockdep_set_current_reclaim_state(GFP_KERNEL);

R
Rusty Russell 已提交
2144
	if (!cpumask_empty(cpumask))
2145
		set_cpus_allowed_ptr(tsk, cpumask);
L
Linus Torvalds 已提交
2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159
	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).
	 */
2160
	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2161
	set_freezable();
L
Linus Torvalds 已提交
2162 2163 2164 2165

	order = 0;
	for ( ; ; ) {
		unsigned long new_order;
2166

L
Linus Torvalds 已提交
2167 2168 2169 2170 2171 2172 2173 2174 2175 2176
		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 {
2177 2178 2179
			if (!freezing(current))
				schedule();

L
Linus Torvalds 已提交
2180 2181 2182 2183
			order = pgdat->kswapd_max_order;
		}
		finish_wait(&pgdat->kswapd_wait, &wait);

2184 2185 2186 2187 2188 2189
		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
2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200
	}
	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;

2201
	if (!populated_zone(zone))
L
Linus Torvalds 已提交
2202 2203 2204
		return;

	pgdat = zone->zone_pgdat;
2205
	if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
L
Linus Torvalds 已提交
2206 2207 2208
		return;
	if (pgdat->kswapd_max_order < order)
		pgdat->kswapd_max_order = order;
2209
	if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
L
Linus Torvalds 已提交
2210
		return;
2211
	if (!waitqueue_active(&pgdat->kswapd_wait))
L
Linus Torvalds 已提交
2212
		return;
2213
	wake_up_interruptible(&pgdat->kswapd_wait);
L
Linus Torvalds 已提交
2214 2215
}

2216 2217 2218 2219 2220 2221 2222 2223
/*
 * The reclaimable count would be mostly accurate.
 * The less reclaimable pages may be
 * - mlocked pages, which will be moved to unevictable list when encountered
 * - mapped pages, which may require several travels to be reclaimed
 * - dirty pages, which is not "instantly" reclaimable
 */
unsigned long global_reclaimable_pages(void)
2224
{
2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248
	int nr;

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

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

	return nr;
}

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

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

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

	return nr;
2249 2250
}

2251
#ifdef CONFIG_HIBERNATION
L
Linus Torvalds 已提交
2252
/*
2253
 * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
2254
 * from LRU lists system-wide, for given pass and priority.
2255 2256 2257
 *
 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
 */
2258
static void shrink_all_zones(unsigned long nr_pages, int prio,
2259
				      int pass, struct scan_control *sc)
2260 2261
{
	struct zone *zone;
2262
	unsigned long nr_reclaimed = 0;
2263
	struct zone_reclaim_stat *reclaim_stat;
2264

2265
	for_each_populated_zone(zone) {
2266
		enum lru_list l;
2267

2268
		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2269 2270
			continue;

L
Lee Schermerhorn 已提交
2271
		for_each_evictable_lru(l) {
2272 2273 2274
			enum zone_stat_item ls = NR_LRU_BASE + l;
			unsigned long lru_pages = zone_page_state(zone, ls);

L
Lee Schermerhorn 已提交
2275
			/* For pass = 0, we don't shrink the active list */
2276 2277
			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
						l == LRU_ACTIVE_FILE))
2278 2279
				continue;

2280 2281 2282 2283 2284
			reclaim_stat = get_reclaim_stat(zone, sc);
			reclaim_stat->nr_saved_scan[l] +=
						(lru_pages >> prio) + 1;
			if (reclaim_stat->nr_saved_scan[l]
						>= nr_pages || pass > 3) {
2285 2286
				unsigned long nr_to_scan;

2287
				reclaim_stat->nr_saved_scan[l] = 0;
2288
				nr_to_scan = min(nr_pages, lru_pages);
2289
				nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2290
								sc, prio);
2291
				if (nr_reclaimed >= nr_pages) {
2292
					sc->nr_reclaimed += nr_reclaimed;
2293 2294
					return;
				}
2295 2296 2297
			}
		}
	}
2298
	sc->nr_reclaimed += nr_reclaimed;
2299 2300 2301 2302 2303 2304 2305 2306 2307
}

/*
 * 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
2308
 */
2309
unsigned long shrink_all_memory(unsigned long nr_pages)
L
Linus Torvalds 已提交
2310
{
2311 2312 2313 2314 2315
	unsigned long lru_pages, nr_slab;
	int pass;
	struct reclaim_state reclaim_state;
	struct scan_control sc = {
		.gfp_mask = GFP_KERNEL,
2316
		.may_unmap = 0,
2317
		.may_writepage = 1,
2318
		.isolate_pages = isolate_pages_global,
2319
		.nr_reclaimed = 0,
L
Linus Torvalds 已提交
2320 2321 2322
	};

	current->reclaim_state = &reclaim_state;
2323

2324
	lru_pages = global_reclaimable_pages();
2325
	nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2326 2327 2328 2329 2330
	/* 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
2331
			break;
2332

2333 2334
		sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		if (sc.nr_reclaimed >= nr_pages)
2335 2336 2337
			goto out;

		nr_slab -= reclaim_state.reclaimed_slab;
L
Linus Torvalds 已提交
2338
	}
2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351

	/*
	 * 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 */
2352
		if (pass > 2)
2353
			sc.may_unmap = 1;
2354 2355

		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2356
			unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2357 2358

			sc.nr_scanned = 0;
2359
			sc.swap_cluster_max = nr_to_scan;
2360 2361
			shrink_all_zones(nr_to_scan, prio, pass, &sc);
			if (sc.nr_reclaimed >= nr_pages)
2362 2363 2364
				goto out;

			reclaim_state.reclaimed_slab = 0;
2365
			shrink_slab(sc.nr_scanned, sc.gfp_mask,
2366
				    global_reclaimable_pages());
2367 2368
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
			if (sc.nr_reclaimed >= nr_pages)
2369 2370 2371
				goto out;

			if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2372
				congestion_wait(BLK_RW_ASYNC, HZ / 10);
2373
		}
2374
	}
2375 2376

	/*
2377 2378
	 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
	 * something in slab caches
2379
	 */
2380
	if (!sc.nr_reclaimed) {
2381 2382
		do {
			reclaim_state.reclaimed_slab = 0;
2383 2384
			shrink_slab(nr_pages, sc.gfp_mask,
				    global_reclaimable_pages());
2385 2386 2387
			sc.nr_reclaimed += reclaim_state.reclaimed_slab;
		} while (sc.nr_reclaimed < nr_pages &&
				reclaim_state.reclaimed_slab > 0);
2388
	}
2389

2390

2391
out:
L
Linus Torvalds 已提交
2392
	current->reclaim_state = NULL;
2393

2394
	return sc.nr_reclaimed;
L
Linus Torvalds 已提交
2395
}
2396
#endif /* CONFIG_HIBERNATION */
L
Linus Torvalds 已提交
2397 2398 2399 2400 2401

/* 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. */
2402
static int __devinit cpu_callback(struct notifier_block *nfb,
2403
				  unsigned long action, void *hcpu)
L
Linus Torvalds 已提交
2404
{
2405
	int nid;
L
Linus Torvalds 已提交
2406

2407
	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2408
		for_each_node_state(nid, N_HIGH_MEMORY) {
2409
			pg_data_t *pgdat = NODE_DATA(nid);
2410 2411 2412
			const struct cpumask *mask;

			mask = cpumask_of_node(pgdat->node_id);
2413

2414
			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
L
Linus Torvalds 已提交
2415
				/* One of our CPUs online: restore mask */
2416
				set_cpus_allowed_ptr(pgdat->kswapd, mask);
L
Linus Torvalds 已提交
2417 2418 2419 2420 2421
		}
	}
	return NOTIFY_OK;
}

2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443
/*
 * 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
2444 2445
static int __init kswapd_init(void)
{
2446
	int nid;
2447

L
Linus Torvalds 已提交
2448
	swap_setup();
2449
	for_each_node_state(nid, N_HIGH_MEMORY)
2450
 		kswapd_run(nid);
L
Linus Torvalds 已提交
2451 2452 2453 2454 2455
	hotcpu_notifier(cpu_callback, 0);
	return 0;
}

module_init(kswapd_init)
2456 2457 2458 2459 2460 2461 2462 2463 2464 2465

#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;

2466
#define RECLAIM_OFF 0
2467
#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
2468 2469 2470
#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */

2471 2472 2473 2474 2475 2476 2477
/*
 * 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

2478 2479 2480 2481 2482 2483
/*
 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
 * occur.
 */
int sysctl_min_unmapped_ratio = 1;

2484 2485 2486 2487 2488 2489
/*
 * 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;

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
static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
{
	unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
	unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
		zone_page_state(zone, NR_ACTIVE_FILE);

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

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

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

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

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

	return nr_pagecache_reclaimable - delta;
}

2532 2533 2534
/*
 * Try to free up some pages from this zone through reclaim.
 */
2535
static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2536
{
2537
	/* Minimum pages needed in order to stay on node */
2538
	const unsigned long nr_pages = 1 << order;
2539 2540
	struct task_struct *p = current;
	struct reclaim_state reclaim_state;
2541
	int priority;
2542 2543
	struct scan_control sc = {
		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2544
		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2545
		.may_swap = 1,
2546 2547
		.swap_cluster_max = max_t(unsigned long, nr_pages,
					SWAP_CLUSTER_MAX),
2548
		.gfp_mask = gfp_mask,
2549
		.swappiness = vm_swappiness,
2550
		.order = order,
2551
		.isolate_pages = isolate_pages_global,
2552
	};
2553
	unsigned long slab_reclaimable;
2554 2555 2556

	disable_swap_token();
	cond_resched();
2557 2558 2559 2560 2561 2562
	/*
	 * 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;
2563 2564
	reclaim_state.reclaimed_slab = 0;
	p->reclaim_state = &reclaim_state;
2565

2566
	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2567 2568 2569 2570 2571 2572
		/*
		 * Free memory by calling shrink zone with increasing
		 * priorities until we have enough memory freed.
		 */
		priority = ZONE_RECLAIM_PRIORITY;
		do {
2573
			note_zone_scanning_priority(zone, priority);
2574
			shrink_zone(priority, zone, &sc);
2575
			priority--;
2576
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2577
	}
2578

2579 2580
	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
	if (slab_reclaimable > zone->min_slab_pages) {
2581
		/*
2582
		 * shrink_slab() does not currently allow us to determine how
2583 2584 2585 2586
		 * 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.
2587
		 *
2588 2589
		 * Note that shrink_slab will free memory on all zones and may
		 * take a long time.
2590
		 */
2591
		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2592 2593
			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
				slab_reclaimable - nr_pages)
2594
			;
2595 2596 2597 2598 2599

		/*
		 * Update nr_reclaimed by the number of slab pages we
		 * reclaimed from this zone.
		 */
2600
		sc.nr_reclaimed += slab_reclaimable -
2601
			zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2602 2603
	}

2604
	p->reclaim_state = NULL;
2605
	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2606
	return sc.nr_reclaimed >= nr_pages;
2607
}
2608 2609 2610 2611

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
	int node_id;
2612
	int ret;
2613 2614

	/*
2615 2616
	 * Zone reclaim reclaims unmapped file backed pages and
	 * slab pages if we are over the defined limits.
2617
	 *
2618 2619 2620 2621 2622
	 * 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.
2623
	 */
2624 2625
	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2626
		return ZONE_RECLAIM_FULL;
2627

2628
	if (zone_is_all_unreclaimable(zone))
2629
		return ZONE_RECLAIM_FULL;
2630

2631
	/*
2632
	 * Do not scan if the allocation should not be delayed.
2633
	 */
2634
	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2635
		return ZONE_RECLAIM_NOSCAN;
2636 2637 2638 2639 2640 2641 2642

	/*
	 * 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.
	 */
2643
	node_id = zone_to_nid(zone);
2644
	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2645
		return ZONE_RECLAIM_NOSCAN;
2646 2647

	if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2648 2649
		return ZONE_RECLAIM_NOSCAN;

2650 2651 2652
	ret = __zone_reclaim(zone, gfp_mask, order);
	zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);

2653 2654 2655
	if (!ret)
		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);

2656
	return ret;
2657
}
2658
#endif
L
Lee Schermerhorn 已提交
2659 2660 2661 2662 2663 2664 2665

/*
 * 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
2666 2667
 * 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
2668 2669
 *
 * Reasons page might not be evictable:
2670
 * (1) page's mapping marked unevictable
N
Nick Piggin 已提交
2671
 * (2) page is part of an mlocked VMA
2672
 *
L
Lee Schermerhorn 已提交
2673 2674 2675 2676
 */
int page_evictable(struct page *page, struct vm_area_struct *vma)
{

2677 2678 2679
	if (mapping_unevictable(page_mapping(page)))
		return 0;

N
Nick Piggin 已提交
2680 2681
	if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
		return 0;
L
Lee Schermerhorn 已提交
2682 2683 2684

	return 1;
}
2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703

/**
 * 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)) {
2704
		enum lru_list l = page_lru_base_type(page);
2705

2706 2707
		__dec_zone_state(zone, NR_UNEVICTABLE);
		list_move(&page->lru, &zone->lru[l].list);
K
KAMEZAWA Hiroyuki 已提交
2708
		mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2709 2710 2711 2712 2713 2714 2715 2716
		__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
2717
		mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
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		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);
	}

}
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/**
 * 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 */
2789
static void scan_zone_unevictable_pages(struct zone *zone)
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{
	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.
 */
2831
static void scan_all_zones_unevictable_pages(void)
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{
	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,
2847
			   void __user *buffer,
2848 2849
			   size_t *length, loff_t *ppos)
{
2850
	proc_doulongvec_minmax(table, write, buffer, length, ppos);
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	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);
}