Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 3828 insertions, 0 deletions

diff --git a/kernel/mm/vmscan.c b/kernel/mm/vmscan.c
new file mode 100644
index 000000000..5e8eadd71
--- /dev/null
+++ b/kernel/mm/vmscan.c
@@ -0,0 +1,3828 @@
+/*
+ *  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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/gfp.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/highmem.h>
+#include <linux/vmpressure.h>
+#include <linux/vmstat.h>
+#include <linux/file.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>	/* for try_to_release_page(),
+					buffer_heads_over_limit */
+#include <linux/mm_inline.h>
+#include <linux/backing-dev.h>
+#include <linux/rmap.h>
+#include <linux/topology.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/compaction.h>
+#include <linux/notifier.h>
+#include <linux/rwsem.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/memcontrol.h>
+#include <linux/delayacct.h>
+#include <linux/sysctl.h>
+#include <linux/oom.h>
+#include <linux/prefetch.h>
+#include <linux/printk.h>
+
+#include <asm/tlbflush.h>
+#include <asm/div64.h>
+
+#include <linux/swapops.h>
+#include <linux/balloon_compaction.h>
+
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/vmscan.h>
+
+struct scan_control {
+	/* How many pages shrink_list() should reclaim */
+	unsigned long nr_to_reclaim;
+
+	/* This context's GFP mask */
+	gfp_t gfp_mask;
+
+	/* Allocation order */
+	int order;
+
+	/*
+	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
+	 * are scanned.
+	 */
+	nodemask_t	*nodemask;
+
+	/*
+	 * The memory cgroup that hit its limit and as a result is the
+	 * primary target of this reclaim invocation.
+	 */
+	struct mem_cgroup *target_mem_cgroup;
+
+	/* Scan (total_size >> priority) pages at once */
+	int priority;
+
+	unsigned int may_writepage:1;
+
+	/* Can mapped pages be reclaimed? */
+	unsigned int may_unmap:1;
+
+	/* Can pages be swapped as part of reclaim? */
+	unsigned int may_swap:1;
+
+	/* Can cgroups be reclaimed below their normal consumption range? */
+	unsigned int may_thrash:1;
+
+	unsigned int hibernation_mode:1;
+
+	/* One of the zones is ready for compaction */
+	unsigned int compaction_ready:1;
+
+	/* Incremented by the number of inactive pages that were scanned */
+	unsigned long nr_scanned;
+
+	/* Number of pages freed so far during a call to shrink_zones() */
+	unsigned long nr_reclaimed;
+};
+
+#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;
+/*
+ * The total number of pages which are beyond the high watermark within all
+ * zones.
+ */
+unsigned long vm_total_pages;
+
+static LIST_HEAD(shrinker_list);
+static DECLARE_RWSEM(shrinker_rwsem);
+
+#ifdef CONFIG_MEMCG
+static bool global_reclaim(struct scan_control *sc)
+{
+	return !sc->target_mem_cgroup;
+}
+#else
+static bool global_reclaim(struct scan_control *sc)
+{
+	return true;
+}
+#endif
+
+static unsigned long zone_reclaimable_pages(struct zone *zone)
+{
+	int nr;
+
+	nr = zone_page_state(zone, NR_ACTIVE_FILE) +
+	     zone_page_state(zone, NR_INACTIVE_FILE);
+
+	if (get_nr_swap_pages() > 0)
+		nr += zone_page_state(zone, NR_ACTIVE_ANON) +
+		      zone_page_state(zone, NR_INACTIVE_ANON);
+
+	return nr;
+}
+
+bool zone_reclaimable(struct zone *zone)
+{
+	return zone_page_state(zone, NR_PAGES_SCANNED) <
+		zone_reclaimable_pages(zone) * 6;
+}
+
+static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
+{
+	if (!mem_cgroup_disabled())
+		return mem_cgroup_get_lru_size(lruvec, lru);
+
+	return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
+}
+
+/*
+ * Add a shrinker callback to be called from the vm.
+ */
+int register_shrinker(struct shrinker *shrinker)
+{
+	size_t size = sizeof(*shrinker->nr_deferred);
+
+	/*
+	 * If we only have one possible node in the system anyway, save
+	 * ourselves the trouble and disable NUMA aware behavior. This way we
+	 * will save memory and some small loop time later.
+	 */
+	if (nr_node_ids == 1)
+		shrinker->flags &= ~SHRINKER_NUMA_AWARE;
+
+	if (shrinker->flags & SHRINKER_NUMA_AWARE)
+		size *= nr_node_ids;
+
+	shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
+	if (!shrinker->nr_deferred)
+		return -ENOMEM;
+
+	down_write(&shrinker_rwsem);
+	list_add_tail(&shrinker->list, &shrinker_list);
+	up_write(&shrinker_rwsem);
+	return 0;
+}
+EXPORT_SYMBOL(register_shrinker);
+
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+	down_write(&shrinker_rwsem);
+	list_del(&shrinker->list);
+	up_write(&shrinker_rwsem);
+	kfree(shrinker->nr_deferred);
+}
+EXPORT_SYMBOL(unregister_shrinker);
+
+#define SHRINK_BATCH 128
+
+static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+				    struct shrinker *shrinker,
+				    unsigned long nr_scanned,
+				    unsigned long nr_eligible)
+{
+	unsigned long freed = 0;
+	unsigned long long delta;
+	long total_scan;
+	long freeable;
+	long nr;
+	long new_nr;
+	int nid = shrinkctl->nid;
+	long batch_size = shrinker->batch ? shrinker->batch
+					  : SHRINK_BATCH;
+
+	freeable = shrinker->count_objects(shrinker, shrinkctl);
+	if (freeable == 0)
+		return 0;
+
+	/*
+	 * copy the current shrinker scan count into a local variable
+	 * and zero it so that other concurrent shrinker invocations
+	 * don't also do this scanning work.
+	 */
+	nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+
+	total_scan = nr;
+	delta = (4 * nr_scanned) / shrinker->seeks;
+	delta *= freeable;
+	do_div(delta, nr_eligible + 1);
+	total_scan += delta;
+	if (total_scan < 0) {
+		pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
+		       shrinker->scan_objects, total_scan);
+		total_scan = freeable;
+	}
+
+	/*
+	 * We need to avoid excessive windup on filesystem shrinkers
+	 * due to large numbers of GFP_NOFS allocations causing the
+	 * shrinkers to return -1 all the time. This results in a large
+	 * nr being built up so when a shrink that can do some work
+	 * comes along it empties the entire cache due to nr >>>
+	 * freeable. This is bad for sustaining a working set in
+	 * memory.
+	 *
+	 * Hence only allow the shrinker to scan the entire cache when
+	 * a large delta change is calculated directly.
+	 */
+	if (delta < freeable / 4)
+		total_scan = min(total_scan, freeable / 2);
+
+	/*
+	 * Avoid risking looping forever due to too large nr value:
+	 * never try to free more than twice the estimate number of
+	 * freeable entries.
+	 */
+	if (total_scan > freeable * 2)
+		total_scan = freeable * 2;
+
+	trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
+				   nr_scanned, nr_eligible,
+				   freeable, delta, total_scan);
+
+	/*
+	 * Normally, we should not scan less than batch_size objects in one
+	 * pass to avoid too frequent shrinker calls, but if the slab has less
+	 * than batch_size objects in total and we are really tight on memory,
+	 * we will try to reclaim all available objects, otherwise we can end
+	 * up failing allocations although there are plenty of reclaimable
+	 * objects spread over several slabs with usage less than the
+	 * batch_size.
+	 *
+	 * We detect the "tight on memory" situations by looking at the total
+	 * number of objects we want to scan (total_scan). If it is greater
+	 * than the total number of objects on slab (freeable), we must be
+	 * scanning at high prio and therefore should try to reclaim as much as
+	 * possible.
+	 */
+	while (total_scan >= batch_size ||
+	       total_scan >= freeable) {
+		unsigned long ret;
+		unsigned long nr_to_scan = min(batch_size, total_scan);
+
+		shrinkctl->nr_to_scan = nr_to_scan;
+		ret = shrinker->scan_objects(shrinker, shrinkctl);
+		if (ret == SHRINK_STOP)
+			break;
+		freed += ret;
+
+		count_vm_events(SLABS_SCANNED, nr_to_scan);
+		total_scan -= nr_to_scan;
+
+		cond_resched();
+	}
+
+	/*
+	 * move the unused scan count back into the shrinker in a
+	 * manner that handles concurrent updates. If we exhausted the
+	 * scan, there is no need to do an update.
+	 */
+	if (total_scan > 0)
+		new_nr = atomic_long_add_return(total_scan,
+						&shrinker->nr_deferred[nid]);
+	else
+		new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+
+	trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
+	return freed;
+}
+
+/**
+ * shrink_slab - shrink slab caches
+ * @gfp_mask: allocation context
+ * @nid: node whose slab caches to target
+ * @memcg: memory cgroup whose slab caches to target
+ * @nr_scanned: pressure numerator
+ * @nr_eligible: pressure denominator
+ *
+ * Call the shrink functions to age shrinkable caches.
+ *
+ * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
+ * unaware shrinkers will receive a node id of 0 instead.
+ *
+ * @memcg specifies the memory cgroup to target. If it is not NULL,
+ * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
+ * objects from the memory cgroup specified. Otherwise all shrinkers
+ * are called, and memcg aware shrinkers are supposed to scan the
+ * global list then.
+ *
+ * @nr_scanned and @nr_eligible form a ratio that indicate how much of
+ * the available objects should be scanned.  Page reclaim for example
+ * passes the number of pages scanned and the number of pages on the
+ * LRU lists that it considered on @nid, plus a bias in @nr_scanned
+ * when it encountered mapped pages.  The ratio is further biased by
+ * the ->seeks setting of the shrink function, which indicates the
+ * cost to recreate an object relative to that of an LRU page.
+ *
+ * Returns the number of reclaimed slab objects.
+ */
+static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
+				 struct mem_cgroup *memcg,
+				 unsigned long nr_scanned,
+				 unsigned long nr_eligible)
+{
+	struct shrinker *shrinker;
+	unsigned long freed = 0;
+
+	if (memcg && !memcg_kmem_is_active(memcg))
+		return 0;
+
+	if (nr_scanned == 0)
+		nr_scanned = SWAP_CLUSTER_MAX;
+
+	if (!down_read_trylock(&shrinker_rwsem)) {
+		/*
+		 * If we would return 0, our callers would understand that we
+		 * have nothing else to shrink and give up trying. By returning
+		 * 1 we keep it going and assume we'll be able to shrink next
+		 * time.
+		 */
+		freed = 1;
+		goto out;
+	}
+
+	list_for_each_entry(shrinker, &shrinker_list, list) {
+		struct shrink_control sc = {
+			.gfp_mask = gfp_mask,
+			.nid = nid,
+			.memcg = memcg,
+		};
+
+		if (memcg && !(shrinker->flags & SHRINKER_MEMCG_AWARE))
+			continue;
+
+		if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+			sc.nid = 0;
+
+		freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible);
+	}
+
+	up_read(&shrinker_rwsem);
+out:
+	cond_resched();
+	return freed;
+}
+
+void drop_slab_node(int nid)
+{
+	unsigned long freed;
+
+	do {
+		struct mem_cgroup *memcg = NULL;
+
+		freed = 0;
+		do {
+			freed += shrink_slab(GFP_KERNEL, nid, memcg,
+					     1000, 1000);
+		} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+	} while (freed > 10);
+}
+
+void drop_slab(void)
+{
+	int nid;
+
+	for_each_online_node(nid)
+		drop_slab_node(nid);
+}
+
+static inline int is_page_cache_freeable(struct page *page)
+{
+	/*
+	 * 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.
+	 */
+	return page_count(page) - page_has_private(page) == 2;
+}
+
+static int may_write_to_queue(struct backing_dev_info *bdi,
+			      struct scan_control *sc)
+{
+	if (current->flags & PF_SWAPWRITE)
+		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);
+	if (page_mapping(page) == mapping)
+		mapping_set_error(mapping, error);
+	unlock_page(page);
+}
+
+/* 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;
+
+/*
+ * pageout is called by shrink_page_list() for each dirty page.
+ * Calls ->writepage().
+ */
+static pageout_t pageout(struct page *page, struct address_space *mapping,
+			 struct scan_control *sc)
+{
+	/*
+	 * 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_iter() 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.
+		 */
+		if (page_has_private(page)) {
+			if (try_to_free_buffers(page)) {
+				ClearPageDirty(page);
+				pr_info("%s: orphaned page\n", __func__);
+				return PAGE_CLEAN;
+			}
+		}
+		return PAGE_KEEP;
+	}
+	if (mapping->a_ops->writepage == NULL)
+		return PAGE_ACTIVATE;
+	if (!may_write_to_queue(inode_to_bdi(mapping->host), sc))
+		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,
+			.range_start = 0,
+			.range_end = LLONG_MAX,
+			.for_reclaim = 1,
+		};
+
+		SetPageReclaim(page);
+		res = mapping->a_ops->writepage(page, &wbc);
+		if (res < 0)
+			handle_write_error(mapping, page, res);
+		if (res == AOP_WRITEPAGE_ACTIVATE) {
+			ClearPageReclaim(page);
+			return PAGE_ACTIVATE;
+		}
+
+		if (!PageWriteback(page)) {
+			/* synchronous write or broken a_ops? */
+			ClearPageReclaim(page);
+		}
+		trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
+		inc_zone_page_state(page, NR_VMSCAN_WRITE);
+		return PAGE_SUCCESS;
+	}
+
+	return PAGE_CLEAN;
+}
+
+/*
+ * Same as remove_mapping, but if the page is removed from the mapping, it
+ * gets returned with a refcount of 0.
+ */
+static int __remove_mapping(struct address_space *mapping, struct page *page,
+			    bool reclaimed)
+{
+	BUG_ON(!PageLocked(page));
+	BUG_ON(mapping != page_mapping(page));
+
+	spin_lock_irq(&mapping->tree_lock);
+	/*
+	 * 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.
+	 */
+	if (!page_freeze_refs(page, 2))
+		goto cannot_free;
+	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
+	if (unlikely(PageDirty(page))) {
+		page_unfreeze_refs(page, 2);
+		goto cannot_free;
+	}
+
+	if (PageSwapCache(page)) {
+		swp_entry_t swap = { .val = page_private(page) };
+		mem_cgroup_swapout(page, swap);
+		__delete_from_swap_cache(page);
+		spin_unlock_irq(&mapping->tree_lock);
+		swapcache_free(swap);
+	} else {
+		void (*freepage)(struct page *);
+		void *shadow = NULL;
+
+		freepage = mapping->a_ops->freepage;
+		/*
+		 * Remember a shadow entry for reclaimed file cache in
+		 * order to detect refaults, thus thrashing, later on.
+		 *
+		 * But don't store shadows in an address space that is
+		 * already exiting.  This is not just an optizimation,
+		 * inode reclaim needs to empty out the radix tree or
+		 * the nodes are lost.  Don't plant shadows behind its
+		 * back.
+		 */
+		if (reclaimed && page_is_file_cache(page) &&
+		    !mapping_exiting(mapping))
+			shadow = workingset_eviction(mapping, page);
+		__delete_from_page_cache(page, shadow);
+		spin_unlock_irq(&mapping->tree_lock);
+
+		if (freepage != NULL)
+			freepage(page);
+	}
+
+	return 1;
+
+cannot_free:
+	spin_unlock_irq(&mapping->tree_lock);
+	return 0;
+}
+
+/*
+ * 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, false)) {
+		/*
+		 * 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;
+}
+
+/**
+ * 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)
+{
+	bool is_unevictable;
+	int was_unevictable = PageUnevictable(page);
+
+	VM_BUG_ON_PAGE(PageLRU(page), page);
+
+redo:
+	ClearPageUnevictable(page);
+
+	if (page_evictable(page)) {
+		/*
+		 * 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.
+		 */
+		is_unevictable = false;
+		lru_cache_add(page);
+	} else {
+		/*
+		 * Put unevictable pages directly on zone's unevictable
+		 * list.
+		 */
+		is_unevictable = true;
+		add_page_to_unevictable_list(page);
+		/*
+		 * When racing with an mlock or AS_UNEVICTABLE clearing
+		 * (page is unlocked) make sure that if the other thread
+		 * does not observe our setting of PG_lru and fails
+		 * isolation/check_move_unevictable_pages,
+		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
+		 * the page back to the evictable list.
+		 *
+		 * The other side is TestClearPageMlocked() or shmem_lock().
+		 */
+		smp_mb();
+	}
+
+	/*
+	 * 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 (is_unevictable && page_evictable(page)) {
+		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.
+		 */
+	}
+
+	if (was_unevictable && !is_unevictable)
+		count_vm_event(UNEVICTABLE_PGRESCUED);
+	else if (!was_unevictable && is_unevictable)
+		count_vm_event(UNEVICTABLE_PGCULLED);
+
+	put_page(page);		/* drop ref from isolate */
+}
+
+enum page_references {
+	PAGEREF_RECLAIM,
+	PAGEREF_RECLAIM_CLEAN,
+	PAGEREF_KEEP,
+	PAGEREF_ACTIVATE,
+};
+
+static enum page_references page_check_references(struct page *page,
+						  struct scan_control *sc)
+{
+	int referenced_ptes, referenced_page;
+	unsigned long vm_flags;
+
+	referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
+					  &vm_flags);
+	referenced_page = TestClearPageReferenced(page);
+
+	/*
+	 * Mlock lost the isolation race with us.  Let try_to_unmap()
+	 * move the page to the unevictable list.
+	 */
+	if (vm_flags & VM_LOCKED)
+		return PAGEREF_RECLAIM;
+
+	if (referenced_ptes) {
+		if (PageSwapBacked(page))
+			return PAGEREF_ACTIVATE;
+		/*
+		 * All mapped pages start out with page table
+		 * references from the instantiating fault, so we need
+		 * to look twice if a mapped file page is used more
+		 * than once.
+		 *
+		 * Mark it and spare it for another trip around the
+		 * inactive list.  Another page table reference will
+		 * lead to its activation.
+		 *
+		 * Note: the mark is set for activated pages as well
+		 * so that recently deactivated but used pages are
+		 * quickly recovered.
+		 */
+		SetPageReferenced(page);
+
+		if (referenced_page || referenced_ptes > 1)
+			return PAGEREF_ACTIVATE;
+
+		/*
+		 * Activate file-backed executable pages after first usage.
+		 */
+		if (vm_flags & VM_EXEC)
+			return PAGEREF_ACTIVATE;
+
+		return PAGEREF_KEEP;
+	}
+
+	/* Reclaim if clean, defer dirty pages to writeback */
+	if (referenced_page && !PageSwapBacked(page))
+		return PAGEREF_RECLAIM_CLEAN;
+
+	return PAGEREF_RECLAIM;
+}
+
+/* Check if a page is dirty or under writeback */
+static void page_check_dirty_writeback(struct page *page,
+				       bool *dirty, bool *writeback)
+{
+	struct address_space *mapping;
+
+	/*
+	 * Anonymous pages are not handled by flushers and must be written
+	 * from reclaim context. Do not stall reclaim based on them
+	 */
+	if (!page_is_file_cache(page)) {
+		*dirty = false;
+		*writeback = false;
+		return;
+	}
+
+	/* By default assume that the page flags are accurate */
+	*dirty = PageDirty(page);
+	*writeback = PageWriteback(page);
+
+	/* Verify dirty/writeback state if the filesystem supports it */
+	if (!page_has_private(page))
+		return;
+
+	mapping = page_mapping(page);
+	if (mapping && mapping->a_ops->is_dirty_writeback)
+		mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
+}
+
+/*
+ * shrink_page_list() returns the number of reclaimed pages
+ */
+static unsigned long shrink_page_list(struct list_head *page_list,
+				      struct zone *zone,
+				      struct scan_control *sc,
+				      enum ttu_flags ttu_flags,
+				      unsigned long *ret_nr_dirty,
+				      unsigned long *ret_nr_unqueued_dirty,
+				      unsigned long *ret_nr_congested,
+				      unsigned long *ret_nr_writeback,
+				      unsigned long *ret_nr_immediate,
+				      bool force_reclaim)
+{
+	LIST_HEAD(ret_pages);
+	LIST_HEAD(free_pages);
+	int pgactivate = 0;
+	unsigned long nr_unqueued_dirty = 0;
+	unsigned long nr_dirty = 0;
+	unsigned long nr_congested = 0;
+	unsigned long nr_reclaimed = 0;
+	unsigned long nr_writeback = 0;
+	unsigned long nr_immediate = 0;
+
+	cond_resched();
+
+	while (!list_empty(page_list)) {
+		struct address_space *mapping;
+		struct page *page;
+		int may_enter_fs;
+		enum page_references references = PAGEREF_RECLAIM_CLEAN;
+		bool dirty, writeback;
+
+		cond_resched();
+
+		page = lru_to_page(page_list);
+		list_del(&page->lru);
+
+		if (!trylock_page(page))
+			goto keep;
+
+		VM_BUG_ON_PAGE(PageActive(page), page);
+		VM_BUG_ON_PAGE(page_zone(page) != zone, page);
+
+		sc->nr_scanned++;
+
+		if (unlikely(!page_evictable(page)))
+			goto cull_mlocked;
+
+		if (!sc->may_unmap && page_mapped(page))
+			goto keep_locked;
+
+		/* Double the slab pressure for mapped and swapcache pages */
+		if (page_mapped(page) || PageSwapCache(page))
+			sc->nr_scanned++;
+
+		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+
+		/*
+		 * The number of dirty pages determines if a zone is marked
+		 * reclaim_congested which affects wait_iff_congested. kswapd
+		 * will stall and start writing pages if the tail of the LRU
+		 * is all dirty unqueued pages.
+		 */
+		page_check_dirty_writeback(page, &dirty, &writeback);
+		if (dirty || writeback)
+			nr_dirty++;
+
+		if (dirty && !writeback)
+			nr_unqueued_dirty++;
+
+		/*
+		 * Treat this page as congested if the underlying BDI is or if
+		 * pages are cycling through the LRU so quickly that the
+		 * pages marked for immediate reclaim are making it to the
+		 * end of the LRU a second time.
+		 */
+		mapping = page_mapping(page);
+		if (((dirty || writeback) && mapping &&
+		     bdi_write_congested(inode_to_bdi(mapping->host))) ||
+		    (writeback && PageReclaim(page)))
+			nr_congested++;
+
+		/*
+		 * If a page at the tail of the LRU is under writeback, there
+		 * are three cases to consider.
+		 *
+		 * 1) If reclaim is encountering an excessive number of pages
+		 *    under writeback and this page is both under writeback and
+		 *    PageReclaim then it indicates that pages are being queued
+		 *    for IO but are being recycled through the LRU before the
+		 *    IO can complete. Waiting on the page itself risks an
+		 *    indefinite stall if it is impossible to writeback the
+		 *    page due to IO error or disconnected storage so instead
+		 *    note that the LRU is being scanned too quickly and the
+		 *    caller can stall after page list has been processed.
+		 *
+		 * 2) Global reclaim encounters a page, memcg encounters a
+		 *    page that is not marked for immediate reclaim or
+		 *    the caller does not have __GFP_IO. In this case mark
+		 *    the page for immediate reclaim and continue scanning.
+		 *
+		 *    __GFP_IO is checked  because a loop driver thread might
+		 *    enter reclaim, and deadlock if it waits on a page for
+		 *    which it is needed to do the write (loop masks off
+		 *    __GFP_IO|__GFP_FS for this reason); but more thought
+		 *    would probably show more reasons.
+		 *
+		 *    Don't require __GFP_FS, since we're not going into the
+		 *    FS, just waiting on its writeback completion. Worryingly,
+		 *    ext4 gfs2 and xfs allocate pages with
+		 *    grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
+		 *    may_enter_fs here is liable to OOM on them.
+		 *
+		 * 3) memcg encounters a page that is not already marked
+		 *    PageReclaim. memcg does not have any dirty pages
+		 *    throttling so we could easily OOM just because too many
+		 *    pages are in writeback and there is nothing else to
+		 *    reclaim. Wait for the writeback to complete.
+		 */
+		if (PageWriteback(page)) {
+			/* Case 1 above */
+			if (current_is_kswapd() &&
+			    PageReclaim(page) &&
+			    test_bit(ZONE_WRITEBACK, &zone->flags)) {
+				nr_immediate++;
+				goto keep_locked;
+
+			/* Case 2 above */
+			} else if (global_reclaim(sc) ||
+			    !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
+				/*
+				 * This is slightly racy - end_page_writeback()
+				 * might have just cleared PageReclaim, then
+				 * setting PageReclaim here end up interpreted
+				 * as PageReadahead - but that does not matter
+				 * enough to care.  What we do want is for this
+				 * page to have PageReclaim set next time memcg
+				 * reclaim reaches the tests above, so it will
+				 * then wait_on_page_writeback() to avoid OOM;
+				 * and it's also appropriate in global reclaim.
+				 */
+				SetPageReclaim(page);
+				nr_writeback++;
+
+				goto keep_locked;
+
+			/* Case 3 above */
+			} else {
+				wait_on_page_writeback(page);
+			}
+		}
+
+		if (!force_reclaim)
+			references = page_check_references(page, sc);
+
+		switch (references) {
+		case PAGEREF_ACTIVATE:
+			goto activate_locked;
+		case PAGEREF_KEEP:
+			goto keep_locked;
+		case PAGEREF_RECLAIM:
+		case PAGEREF_RECLAIM_CLEAN:
+			; /* try to reclaim the page below */
+		}
+
+		/*
+		 * Anonymous process memory has backing store?
+		 * Try to allocate it some swap space here.
+		 */
+		if (PageAnon(page) && !PageSwapCache(page)) {
+			if (!(sc->gfp_mask & __GFP_IO))
+				goto keep_locked;
+			if (!add_to_swap(page, page_list))
+				goto activate_locked;
+			may_enter_fs = 1;
+
+			/* Adding to swap updated mapping */
+			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) {
+			switch (try_to_unmap(page, ttu_flags)) {
+			case SWAP_FAIL:
+				goto activate_locked;
+			case SWAP_AGAIN:
+				goto keep_locked;
+			case SWAP_MLOCK:
+				goto cull_mlocked;
+			case SWAP_SUCCESS:
+				; /* try to free the page below */
+			}
+		}
+
+		if (PageDirty(page)) {
+			/*
+			 * Only kswapd can writeback filesystem pages to
+			 * avoid risk of stack overflow but only writeback
+			 * if many dirty pages have been encountered.
+			 */
+			if (page_is_file_cache(page) &&
+					(!current_is_kswapd() ||
+					 !test_bit(ZONE_DIRTY, &zone->flags))) {
+				/*
+				 * Immediately reclaim when written back.
+				 * Similar in principal to deactivate_page()
+				 * except we already have the page isolated
+				 * and know it's dirty
+				 */
+				inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+				SetPageReclaim(page);
+
+				goto keep_locked;
+			}
+
+			if (references == PAGEREF_RECLAIM_CLEAN)
+				goto keep_locked;
+			if (!may_enter_fs)
+				goto keep_locked;
+			if (!sc->may_writepage)
+				goto keep_locked;
+
+			/* Page is dirty, try to write it out here */
+			switch (pageout(page, mapping, sc)) {
+			case PAGE_KEEP:
+				goto keep_locked;
+			case PAGE_ACTIVATE:
+				goto activate_locked;
+			case PAGE_SUCCESS:
+				if (PageWriteback(page))
+					goto keep;
+				if (PageDirty(page))
+					goto keep;
+
+				/*
+				 * A synchronous write - probably a ramdisk.  Go
+				 * ahead and try to reclaim the page.
+				 */
+				if (!trylock_page(page))
+					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
+		 * will do this, as well as the blockdev mapping.
+		 * 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.
+		 */
+		if (page_has_private(page)) {
+			if (!try_to_release_page(page, sc->gfp_mask))
+				goto activate_locked;
+			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;
+				}
+			}
+		}
+
+		if (!mapping || !__remove_mapping(mapping, page, true))
+			goto keep_locked;
+
+		/*
+		 * 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);
+free_it:
+		nr_reclaimed++;
+
+		/*
+		 * Is there need to periodically free_page_list? It would
+		 * appear not as the counts should be low
+		 */
+		list_add(&page->lru, &free_pages);
+		continue;
+
+cull_mlocked:
+		if (PageSwapCache(page))
+			try_to_free_swap(page);
+		unlock_page(page);
+		putback_lru_page(page);
+		continue;
+
+activate_locked:
+		/* Not a candidate for swapping, so reclaim swap space. */
+		if (PageSwapCache(page) && vm_swap_full())
+			try_to_free_swap(page);
+		VM_BUG_ON_PAGE(PageActive(page), page);
+		SetPageActive(page);
+		pgactivate++;
+keep_locked:
+		unlock_page(page);
+keep:
+		list_add(&page->lru, &ret_pages);
+		VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
+	}
+
+	mem_cgroup_uncharge_list(&free_pages);
+	free_hot_cold_page_list(&free_pages, true);
+
+	list_splice(&ret_pages, page_list);
+	count_vm_events(PGACTIVATE, pgactivate);
+
+	*ret_nr_dirty += nr_dirty;
+	*ret_nr_congested += nr_congested;
+	*ret_nr_unqueued_dirty += nr_unqueued_dirty;
+	*ret_nr_writeback += nr_writeback;
+	*ret_nr_immediate += nr_immediate;
+	return nr_reclaimed;
+}
+
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+					    struct list_head *page_list)
+{
+	struct scan_control sc = {
+		.gfp_mask = GFP_KERNEL,
+		.priority = DEF_PRIORITY,
+		.may_unmap = 1,
+	};
+	unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
+	struct page *page, *next;
+	LIST_HEAD(clean_pages);
+
+	list_for_each_entry_safe(page, next, page_list, lru) {
+		if (page_is_file_cache(page) && !PageDirty(page) &&
+		    !isolated_balloon_page(page)) {
+			ClearPageActive(page);
+			list_move(&page->lru, &clean_pages);
+		}
+	}
+
+	ret = shrink_page_list(&clean_pages, zone, &sc,
+			TTU_UNMAP|TTU_IGNORE_ACCESS,
+			&dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
+	list_splice(&clean_pages, page_list);
+	mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
+	return ret;
+}
+
+/*
+ * 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.
+ */
+int __isolate_lru_page(struct page *page, isolate_mode_t mode)
+{
+	int ret = -EINVAL;
+
+	/* Only take pages on the LRU. */
+	if (!PageLRU(page))
+		return ret;
+
+	/* Compaction should not handle unevictable pages but CMA can do so */
+	if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
+		return ret;
+
+	ret = -EBUSY;
+
+	/*
+	 * To minimise LRU disruption, the caller can indicate that it only
+	 * wants to isolate pages it will be able to operate on without
+	 * blocking - clean pages for the most part.
+	 *
+	 * ISOLATE_CLEAN means that only clean pages should be isolated. This
+	 * is used by reclaim when it is cannot write to backing storage
+	 *
+	 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
+	 * that it is possible to migrate without blocking
+	 */
+	if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
+		/* All the caller can do on PageWriteback is block */
+		if (PageWriteback(page))
+			return ret;
+
+		if (PageDirty(page)) {
+			struct address_space *mapping;
+
+			/* ISOLATE_CLEAN means only clean pages */
+			if (mode & ISOLATE_CLEAN)
+				return ret;
+
+			/*
+			 * Only pages without mappings or that have a
+			 * ->migratepage callback are possible to migrate
+			 * without blocking
+			 */
+			mapping = page_mapping(page);
+			if (mapping && !mapping->a_ops->migratepage)
+				return ret;
+		}
+	}
+
+	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
+		return ret;
+
+	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;
+}
+
+/*
+ * 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.
+ * @lruvec:	The LRU vector to pull pages from.
+ * @dst:	The temp list to put pages on to.
+ * @nr_scanned:	The number of pages that were scanned.
+ * @sc:		The scan_control struct for this reclaim session
+ * @mode:	One of the LRU isolation modes
+ * @lru:	LRU list id for isolating
+ *
+ * returns how many pages were moved onto *@dst.
+ */
+static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
+		struct lruvec *lruvec, struct list_head *dst,
+		unsigned long *nr_scanned, struct scan_control *sc,
+		isolate_mode_t mode, enum lru_list lru)
+{
+	struct list_head *src = &lruvec->lists[lru];
+	unsigned long nr_taken = 0;
+	unsigned long scan;
+
+	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
+		struct page *page;
+		int nr_pages;
+
+		page = lru_to_page(src);
+		prefetchw_prev_lru_page(page, src, flags);
+
+		VM_BUG_ON_PAGE(!PageLRU(page), page);
+
+		switch (__isolate_lru_page(page, mode)) {
+		case 0:
+			nr_pages = hpage_nr_pages(page);
+			mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
+			list_move(&page->lru, dst);
+			nr_taken += nr_pages;
+			break;
+
+		case -EBUSY:
+			/* else it is being freed elsewhere */
+			list_move(&page->lru, src);
+			continue;
+
+		default:
+			BUG();
+		}
+	}
+
+	*nr_scanned = scan;
+	trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
+				    nr_taken, mode, is_file_lru(lru));
+	return nr_taken;
+}
+
+/**
+ * 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
+ * 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.
+ *
+ * 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;
+
+	VM_BUG_ON_PAGE(!page_count(page), page);
+
+	if (PageLRU(page)) {
+		struct zone *zone = page_zone(page);
+		struct lruvec *lruvec;
+
+		spin_lock_irq(&zone->lru_lock);
+		lruvec = mem_cgroup_page_lruvec(page, zone);
+		if (PageLRU(page)) {
+			int lru = page_lru(page);
+			get_page(page);
+			ClearPageLRU(page);
+			del_page_from_lru_list(page, lruvec, lru);
+			ret = 0;
+		}
+		spin_unlock_irq(&zone->lru_lock);
+	}
+	return ret;
+}
+
+/*
+ * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
+ * then get resheduled. When there are massive number of tasks doing page
+ * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
+ * the LRU list will go small and be scanned faster than necessary, leading to
+ * unnecessary swapping, thrashing and OOM.
+ */
+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 (!global_reclaim(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);
+	}
+
+	/*
+	 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
+	 * won't get blocked by normal direct-reclaimers, forming a circular
+	 * deadlock.
+	 */
+	if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
+		inactive >>= 3;
+
+	return isolated > inactive;
+}
+
+static noinline_for_stack void
+putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
+{
+	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+	struct zone *zone = lruvec_zone(lruvec);
+	LIST_HEAD(pages_to_free);
+
+	/*
+	 * Put back any unfreeable pages.
+	 */
+	while (!list_empty(page_list)) {
+		struct page *page = lru_to_page(page_list);
+		int lru;
+
+		VM_BUG_ON_PAGE(PageLRU(page), page);
+		list_del(&page->lru);
+		if (unlikely(!page_evictable(page))) {
+			spin_unlock_irq(&zone->lru_lock);
+			putback_lru_page(page);
+			spin_lock_irq(&zone->lru_lock);
+			continue;
+		}
+
+		lruvec = mem_cgroup_page_lruvec(page, zone);
+
+		SetPageLRU(page);
+		lru = page_lru(page);
+		add_page_to_lru_list(page, lruvec, lru);
+
+		if (is_active_lru(lru)) {
+			int file = is_file_lru(lru);
+			int numpages = hpage_nr_pages(page);
+			reclaim_stat->recent_rotated[file] += numpages;
+		}
+		if (put_page_testzero(page)) {
+			__ClearPageLRU(page);
+			__ClearPageActive(page);
+			del_page_from_lru_list(page, lruvec, lru);
+
+			if (unlikely(PageCompound(page))) {
+				spin_unlock_irq(&zone->lru_lock);
+				mem_cgroup_uncharge(page);
+				(*get_compound_page_dtor(page))(page);
+				spin_lock_irq(&zone->lru_lock);
+			} else
+				list_add(&page->lru, &pages_to_free);
+		}
+	}
+
+	/*
+	 * To save our caller's stack, now use input list for pages to free.
+	 */
+	list_splice(&pages_to_free, page_list);
+}
+
+/*
+ * If a kernel thread (such as nfsd for loop-back mounts) services
+ * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
+ * In that case we should only throttle if the backing device it is
+ * writing to is congested.  In other cases it is safe to throttle.
+ */
+static int current_may_throttle(void)
+{
+	return !(current->flags & PF_LESS_THROTTLE) ||
+		current->backing_dev_info == NULL ||
+		bdi_write_congested(current->backing_dev_info);
+}
+
+/*
+ * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
+ * of reclaimed pages
+ */
+static noinline_for_stack unsigned long
+shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
+		     struct scan_control *sc, enum lru_list lru)
+{
+	LIST_HEAD(page_list);
+	unsigned long nr_scanned;
+	unsigned long nr_reclaimed = 0;
+	unsigned long nr_taken;
+	unsigned long nr_dirty = 0;
+	unsigned long nr_congested = 0;
+	unsigned long nr_unqueued_dirty = 0;
+	unsigned long nr_writeback = 0;
+	unsigned long nr_immediate = 0;
+	isolate_mode_t isolate_mode = 0;
+	int file = is_file_lru(lru);
+	struct zone *zone = lruvec_zone(lruvec);
+	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+
+	while (unlikely(too_many_isolated(zone, file, sc))) {
+		congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+		/* We are about to die and free our memory. Return now. */
+		if (fatal_signal_pending(current))
+			return SWAP_CLUSTER_MAX;
+	}
+
+	lru_add_drain();
+
+	if (!sc->may_unmap)
+		isolate_mode |= ISOLATE_UNMAPPED;
+	if (!sc->may_writepage)
+		isolate_mode |= ISOLATE_CLEAN;
+
+	spin_lock_irq(&zone->lru_lock);
+
+	nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
+				     &nr_scanned, sc, isolate_mode, lru);
+
+	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
+	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
+
+	if (global_reclaim(sc)) {
+		__mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
+		if (current_is_kswapd())
+			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
+		else
+			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
+	}
+	spin_unlock_irq(&zone->lru_lock);
+
+	if (nr_taken == 0)
+		return 0;
+
+	nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
+				&nr_dirty, &nr_unqueued_dirty, &nr_congested,
+				&nr_writeback, &nr_immediate,
+				false);
+
+	spin_lock_irq(&zone->lru_lock);
+
+	reclaim_stat->recent_scanned[file] += nr_taken;
+
+	if (global_reclaim(sc)) {
+		if (current_is_kswapd())
+			__count_zone_vm_events(PGSTEAL_KSWAPD, zone,
+					       nr_reclaimed);
+		else
+			__count_zone_vm_events(PGSTEAL_DIRECT, zone,
+					       nr_reclaimed);
+	}
+
+	putback_inactive_pages(lruvec, &page_list);
+
+	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
+
+	spin_unlock_irq(&zone->lru_lock);
+
+	mem_cgroup_uncharge_list(&page_list);
+	free_hot_cold_page_list(&page_list, true);
+
+	/*
+	 * If reclaim is isolating dirty pages under writeback, it implies
+	 * that the long-lived page allocation rate is exceeding the page
+	 * laundering rate. Either the global limits are not being effective
+	 * at throttling processes due to the page distribution throughout
+	 * zones or there is heavy usage of a slow backing device. The
+	 * only option is to throttle from reclaim context which is not ideal
+	 * as there is no guarantee the dirtying process is throttled in the
+	 * same way balance_dirty_pages() manages.
+	 *
+	 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
+	 * of pages under pages flagged for immediate reclaim and stall if any
+	 * are encountered in the nr_immediate check below.
+	 */
+	if (nr_writeback && nr_writeback == nr_taken)
+		set_bit(ZONE_WRITEBACK, &zone->flags);
+
+	/*
+	 * memcg will stall in page writeback so only consider forcibly
+	 * stalling for global reclaim
+	 */
+	if (global_reclaim(sc)) {
+		/*
+		 * Tag a zone as congested if all the dirty pages scanned were
+		 * backed by a congested BDI and wait_iff_congested will stall.
+		 */
+		if (nr_dirty && nr_dirty == nr_congested)
+			set_bit(ZONE_CONGESTED, &zone->flags);
+
+		/*
+		 * If dirty pages are scanned that are not queued for IO, it
+		 * implies that flushers are not keeping up. In this case, flag
+		 * the zone ZONE_DIRTY and kswapd will start writing pages from
+		 * reclaim context.
+		 */
+		if (nr_unqueued_dirty == nr_taken)
+			set_bit(ZONE_DIRTY, &zone->flags);
+
+		/*
+		 * If kswapd scans pages marked marked for immediate
+		 * reclaim and under writeback (nr_immediate), it implies
+		 * that pages are cycling through the LRU faster than
+		 * they are written so also forcibly stall.
+		 */
+		if (nr_immediate && current_may_throttle())
+			congestion_wait(BLK_RW_ASYNC, HZ/10);
+	}
+
+	/*
+	 * Stall direct reclaim for IO completions if underlying BDIs or zone
+	 * is congested. Allow kswapd to continue until it starts encountering
+	 * unqueued dirty pages or cycling through the LRU too quickly.
+	 */
+	if (!sc->hibernation_mode && !current_is_kswapd() &&
+	    current_may_throttle())
+		wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
+
+	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
+		zone_idx(zone),
+		nr_scanned, nr_reclaimed,
+		sc->priority,
+		trace_shrink_flags(file));
+	return nr_reclaimed;
+}
+
+/*
+ * 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.
+ */
+
+static void move_active_pages_to_lru(struct lruvec *lruvec,
+				     struct list_head *list,
+				     struct list_head *pages_to_free,
+				     enum lru_list lru)
+{
+	struct zone *zone = lruvec_zone(lruvec);
+	unsigned long pgmoved = 0;
+	struct page *page;
+	int nr_pages;
+
+	while (!list_empty(list)) {
+		page = lru_to_page(list);
+		lruvec = mem_cgroup_page_lruvec(page, zone);
+
+		VM_BUG_ON_PAGE(PageLRU(page), page);
+		SetPageLRU(page);
+
+		nr_pages = hpage_nr_pages(page);
+		mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
+		list_move(&page->lru, &lruvec->lists[lru]);
+		pgmoved += nr_pages;
+
+		if (put_page_testzero(page)) {
+			__ClearPageLRU(page);
+			__ClearPageActive(page);
+			del_page_from_lru_list(page, lruvec, lru);
+
+			if (unlikely(PageCompound(page))) {
+				spin_unlock_irq(&zone->lru_lock);
+				mem_cgroup_uncharge(page);
+				(*get_compound_page_dtor(page))(page);
+				spin_lock_irq(&zone->lru_lock);
+			} else
+				list_add(&page->lru, pages_to_free);
+		}
+	}
+	__mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
+	if (!is_active_lru(lru))
+		__count_vm_events(PGDEACTIVATE, pgmoved);
+}
+
+static void shrink_active_list(unsigned long nr_to_scan,
+			       struct lruvec *lruvec,
+			       struct scan_control *sc,
+			       enum lru_list lru)
+{
+	unsigned long nr_taken;
+	unsigned long nr_scanned;
+	unsigned long vm_flags;
+	LIST_HEAD(l_hold);	/* The pages which were snipped off */
+	LIST_HEAD(l_active);
+	LIST_HEAD(l_inactive);
+	struct page *page;
+	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+	unsigned long nr_rotated = 0;
+	isolate_mode_t isolate_mode = 0;
+	int file = is_file_lru(lru);
+	struct zone *zone = lruvec_zone(lruvec);
+
+	lru_add_drain();
+
+	if (!sc->may_unmap)
+		isolate_mode |= ISOLATE_UNMAPPED;
+	if (!sc->may_writepage)
+		isolate_mode |= ISOLATE_CLEAN;
+
+	spin_lock_irq(&zone->lru_lock);
+
+	nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
+				     &nr_scanned, sc, isolate_mode, lru);
+	if (global_reclaim(sc))
+		__mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
+
+	reclaim_stat->recent_scanned[file] += nr_taken;
+
+	__count_zone_vm_events(PGREFILL, zone, nr_scanned);
+	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
+	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
+	spin_unlock_irq(&zone->lru_lock);
+
+	while (!list_empty(&l_hold)) {
+		cond_resched();
+		page = lru_to_page(&l_hold);
+		list_del(&page->lru);
+
+		if (unlikely(!page_evictable(page))) {
+			putback_lru_page(page);
+			continue;
+		}
+
+		if (unlikely(buffer_heads_over_limit)) {
+			if (page_has_private(page) && trylock_page(page)) {
+				if (page_has_private(page))
+					try_to_release_page(page, 0);
+				unlock_page(page);
+			}
+		}
+
+		if (page_referenced(page, 0, sc->target_mem_cgroup,
+				    &vm_flags)) {
+			nr_rotated += hpage_nr_pages(page);
+			/*
+			 * 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) && page_is_file_cache(page)) {
+				list_add(&page->lru, &l_active);
+				continue;
+			}
+		}
+
+		ClearPageActive(page);	/* we are de-activating */
+		list_add(&page->lru, &l_inactive);
+	}
+
+	/*
+	 * Move pages back to the lru list.
+	 */
+	spin_lock_irq(&zone->lru_lock);
+	/*
+	 * 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_count.
+	 */
+	reclaim_stat->recent_rotated[file] += nr_rotated;
+
+	move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
+	move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
+	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
+	spin_unlock_irq(&zone->lru_lock);
+
+	mem_cgroup_uncharge_list(&l_hold);
+	free_hot_cold_page_list(&l_hold, true);
+}
+
+#ifdef CONFIG_SWAP
+static int inactive_anon_is_low_global(struct zone *zone)
+{
+	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;
+}
+
+/**
+ * inactive_anon_is_low - check if anonymous pages need to be deactivated
+ * @lruvec: LRU vector to check
+ *
+ * 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 lruvec *lruvec)
+{
+	/*
+	 * If we don't have swap space, anonymous page deactivation
+	 * is pointless.
+	 */
+	if (!total_swap_pages)
+		return 0;
+
+	if (!mem_cgroup_disabled())
+		return mem_cgroup_inactive_anon_is_low(lruvec);
+
+	return inactive_anon_is_low_global(lruvec_zone(lruvec));
+}
+#else
+static inline int inactive_anon_is_low(struct lruvec *lruvec)
+{
+	return 0;
+}
+#endif
+
+/**
+ * inactive_file_is_low - check if file pages need to be deactivated
+ * @lruvec: LRU vector to check
+ *
+ * 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 lruvec *lruvec)
+{
+	unsigned long inactive;
+	unsigned long active;
+
+	inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
+	active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
+
+	return active > inactive;
+}
+
+static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
+{
+	if (is_file_lru(lru))
+		return inactive_file_is_low(lruvec);
+	else
+		return inactive_anon_is_low(lruvec);
+}
+
+static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
+				 struct lruvec *lruvec, struct scan_control *sc)
+{
+	if (is_active_lru(lru)) {
+		if (inactive_list_is_low(lruvec, lru))
+			shrink_active_list(nr_to_scan, lruvec, sc, lru);
+		return 0;
+	}
+
+	return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
+}
+
+enum scan_balance {
+	SCAN_EQUAL,
+	SCAN_FRACT,
+	SCAN_ANON,
+	SCAN_FILE,
+};
+
+/*
+ * 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.
+ *
+ * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
+ * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
+ */
+static void get_scan_count(struct lruvec *lruvec, int swappiness,
+			   struct scan_control *sc, unsigned long *nr,
+			   unsigned long *lru_pages)
+{
+	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+	u64 fraction[2];
+	u64 denominator = 0;	/* gcc */
+	struct zone *zone = lruvec_zone(lruvec);
+	unsigned long anon_prio, file_prio;
+	enum scan_balance scan_balance;
+	unsigned long anon, file;
+	bool force_scan = false;
+	unsigned long ap, fp;
+	enum lru_list lru;
+	bool some_scanned;
+	int pass;
+
+	/*
+	 * If the zone or memcg is small, nr[l] can be 0.  This
+	 * results in no scanning on this priority and a potential
+	 * priority drop.  Global direct reclaim can go to the next
+	 * zone and tends to have no problems. Global kswapd is for
+	 * zone balancing and it needs to scan a minimum amount. When
+	 * reclaiming for a memcg, a priority drop can cause high
+	 * latencies, so it's better to scan a minimum amount there as
+	 * well.
+	 */
+	if (current_is_kswapd()) {
+		if (!zone_reclaimable(zone))
+			force_scan = true;
+		if (!mem_cgroup_lruvec_online(lruvec))
+			force_scan = true;
+	}
+	if (!global_reclaim(sc))
+		force_scan = true;
+
+	/* If we have no swap space, do not bother scanning anon pages. */
+	if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
+		scan_balance = SCAN_FILE;
+		goto out;
+	}
+
+	/*
+	 * Global reclaim will swap to prevent OOM even with no
+	 * swappiness, but memcg users want to use this knob to
+	 * disable swapping for individual groups completely when
+	 * using the memory controller's swap limit feature would be
+	 * too expensive.
+	 */
+	if (!global_reclaim(sc) && !swappiness) {
+		scan_balance = SCAN_FILE;
+		goto out;
+	}
+
+	/*
+	 * Do not apply any pressure balancing cleverness when the
+	 * system is close to OOM, scan both anon and file equally
+	 * (unless the swappiness setting disagrees with swapping).
+	 */
+	if (!sc->priority && swappiness) {
+		scan_balance = SCAN_EQUAL;
+		goto out;
+	}
+
+	/*
+	 * Prevent the reclaimer from falling into the cache trap: as
+	 * cache pages start out inactive, every cache fault will tip
+	 * the scan balance towards the file LRU.  And as the file LRU
+	 * shrinks, so does the window for rotation from references.
+	 * This means we have a runaway feedback loop where a tiny
+	 * thrashing file LRU becomes infinitely more attractive than
+	 * anon pages.  Try to detect this based on file LRU size.
+	 */
+	if (global_reclaim(sc)) {
+		unsigned long zonefile;
+		unsigned long zonefree;
+
+		zonefree = zone_page_state(zone, NR_FREE_PAGES);
+		zonefile = zone_page_state(zone, NR_ACTIVE_FILE) +
+			   zone_page_state(zone, NR_INACTIVE_FILE);
+
+		if (unlikely(zonefile + zonefree <= high_wmark_pages(zone))) {
+			scan_balance = SCAN_ANON;
+			goto out;
+		}
+	}
+
+	/*
+	 * There is enough inactive page cache, do not reclaim
+	 * anything from the anonymous working set right now.
+	 */
+	if (!inactive_file_is_low(lruvec)) {
+		scan_balance = SCAN_FILE;
+		goto out;
+	}
+
+	scan_balance = SCAN_FRACT;
+
+	/*
+	 * With swappiness at 100, anonymous and file have the same priority.
+	 * This scanning priority is essentially the inverse of IO cost.
+	 */
+	anon_prio = swappiness;
+	file_prio = 200 - anon_prio;
+
+	/*
+	 * 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]
+	 */
+
+	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
+		get_lru_size(lruvec, LRU_INACTIVE_ANON);
+	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
+		get_lru_size(lruvec, LRU_INACTIVE_FILE);
+
+	spin_lock_irq(&zone->lru_lock);
+	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
+		reclaim_stat->recent_scanned[0] /= 2;
+		reclaim_stat->recent_rotated[0] /= 2;
+	}
+
+	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
+		reclaim_stat->recent_scanned[1] /= 2;
+		reclaim_stat->recent_rotated[1] /= 2;
+	}
+
+	/*
+	 * 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.
+	 */
+	ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
+	ap /= reclaim_stat->recent_rotated[0] + 1;
+
+	fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
+	fp /= reclaim_stat->recent_rotated[1] + 1;
+	spin_unlock_irq(&zone->lru_lock);
+
+	fraction[0] = ap;
+	fraction[1] = fp;
+	denominator = ap + fp + 1;
+out:
+	some_scanned = false;
+	/* Only use force_scan on second pass. */
+	for (pass = 0; !some_scanned && pass < 2; pass++) {
+		*lru_pages = 0;
+		for_each_evictable_lru(lru) {
+			int file = is_file_lru(lru);
+			unsigned long size;
+			unsigned long scan;
+
+			size = get_lru_size(lruvec, lru);
+			scan = size >> sc->priority;
+
+			if (!scan && pass && force_scan)
+				scan = min(size, SWAP_CLUSTER_MAX);
+
+			switch (scan_balance) {
+			case SCAN_EQUAL:
+				/* Scan lists relative to size */
+				break;
+			case SCAN_FRACT:
+				/*
+				 * Scan types proportional to swappiness and
+				 * their relative recent reclaim efficiency.
+				 */
+				scan = div64_u64(scan * fraction[file],
+							denominator);
+				break;
+			case SCAN_FILE:
+			case SCAN_ANON:
+				/* Scan one type exclusively */
+				if ((scan_balance == SCAN_FILE) != file) {
+					size = 0;
+					scan = 0;
+				}
+				break;
+			default:
+				/* Look ma, no brain */
+				BUG();
+			}
+
+			*lru_pages += size;
+			nr[lru] = scan;
+
+			/*
+			 * Skip the second pass and don't force_scan,
+			 * if we found something to scan.
+			 */
+			some_scanned |= !!scan;
+		}
+	}
+}
+
+/*
+ * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
+ */
+static void shrink_lruvec(struct lruvec *lruvec, int swappiness,
+			  struct scan_control *sc, unsigned long *lru_pages)
+{
+	unsigned long nr[NR_LRU_LISTS];
+	unsigned long targets[NR_LRU_LISTS];
+	unsigned long nr_to_scan;
+	enum lru_list lru;
+	unsigned long nr_reclaimed = 0;
+	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+	struct blk_plug plug;
+	bool scan_adjusted;
+
+	get_scan_count(lruvec, swappiness, sc, nr, lru_pages);
+
+	/* Record the original scan target for proportional adjustments later */
+	memcpy(targets, nr, sizeof(nr));
+
+	/*
+	 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
+	 * event that can occur when there is little memory pressure e.g.
+	 * multiple streaming readers/writers. Hence, we do not abort scanning
+	 * when the requested number of pages are reclaimed when scanning at
+	 * DEF_PRIORITY on the assumption that the fact we are direct
+	 * reclaiming implies that kswapd is not keeping up and it is best to
+	 * do a batch of work at once. For memcg reclaim one check is made to
+	 * abort proportional reclaim if either the file or anon lru has already
+	 * dropped to zero at the first pass.
+	 */
+	scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() &&
+			 sc->priority == DEF_PRIORITY);
+
+	blk_start_plug(&plug);
+	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
+					nr[LRU_INACTIVE_FILE]) {
+		unsigned long nr_anon, nr_file, percentage;
+		unsigned long nr_scanned;
+
+		for_each_evictable_lru(lru) {
+			if (nr[lru]) {
+				nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
+				nr[lru] -= nr_to_scan;
+
+				nr_reclaimed += shrink_list(lru, nr_to_scan,
+							    lruvec, sc);
+			}
+		}
+
+		if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
+			continue;
+
+		/*
+		 * For kswapd and memcg, reclaim at least the number of pages
+		 * requested. Ensure that the anon and file LRUs are scanned
+		 * proportionally what was requested by get_scan_count(). We
+		 * stop reclaiming one LRU and reduce the amount scanning
+		 * proportional to the original scan target.
+		 */
+		nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
+		nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
+
+		/*
+		 * It's just vindictive to attack the larger once the smaller
+		 * has gone to zero.  And given the way we stop scanning the
+		 * smaller below, this makes sure that we only make one nudge
+		 * towards proportionality once we've got nr_to_reclaim.
+		 */
+		if (!nr_file || !nr_anon)
+			break;
+
+		if (nr_file > nr_anon) {
+			unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
+						targets[LRU_ACTIVE_ANON] + 1;
+			lru = LRU_BASE;
+			percentage = nr_anon * 100 / scan_target;
+		} else {
+			unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
+						targets[LRU_ACTIVE_FILE] + 1;
+			lru = LRU_FILE;
+			percentage = nr_file * 100 / scan_target;
+		}
+
+		/* Stop scanning the smaller of the LRU */
+		nr[lru] = 0;
+		nr[lru + LRU_ACTIVE] = 0;
+
+		/*
+		 * Recalculate the other LRU scan count based on its original
+		 * scan target and the percentage scanning already complete
+		 */
+		lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
+		nr_scanned = targets[lru] - nr[lru];
+		nr[lru] = targets[lru] * (100 - percentage) / 100;
+		nr[lru] -= min(nr[lru], nr_scanned);
+
+		lru += LRU_ACTIVE;
+		nr_scanned = targets[lru] - nr[lru];
+		nr[lru] = targets[lru] * (100 - percentage) / 100;
+		nr[lru] -= min(nr[lru], nr_scanned);
+
+		scan_adjusted = true;
+	}
+	blk_finish_plug(&plug);
+	sc->nr_reclaimed += nr_reclaimed;
+
+	/*
+	 * Even if we did not try to evict anon pages at all, we want to
+	 * rebalance the anon lru active/inactive ratio.
+	 */
+	if (inactive_anon_is_low(lruvec))
+		shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+				   sc, LRU_ACTIVE_ANON);
+
+	throttle_vm_writeout(sc->gfp_mask);
+}
+
+/* Use reclaim/compaction for costly allocs or under memory pressure */
+static bool in_reclaim_compaction(struct scan_control *sc)
+{
+	if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
+			(sc->order > PAGE_ALLOC_COSTLY_ORDER ||
+			 sc->priority < DEF_PRIORITY - 2))
+		return true;
+
+	return false;
+}
+
+/*
+ * Reclaim/compaction is used for high-order allocation requests. It reclaims
+ * order-0 pages before compacting the zone. should_continue_reclaim() returns
+ * true if more pages should be reclaimed such that when the page allocator
+ * calls try_to_compact_zone() that it will have enough free pages to succeed.
+ * It will give up earlier than that if there is difficulty reclaiming pages.
+ */
+static inline bool should_continue_reclaim(struct zone *zone,
+					unsigned long nr_reclaimed,
+					unsigned long nr_scanned,
+					struct scan_control *sc)
+{
+	unsigned long pages_for_compaction;
+	unsigned long inactive_lru_pages;
+
+	/* If not in reclaim/compaction mode, stop */
+	if (!in_reclaim_compaction(sc))
+		return false;
+
+	/* Consider stopping depending on scan and reclaim activity */
+	if (sc->gfp_mask & __GFP_REPEAT) {
+		/*
+		 * For __GFP_REPEAT allocations, stop reclaiming if the
+		 * full LRU list has been scanned and we are still failing
+		 * to reclaim pages. This full LRU scan is potentially
+		 * expensive but a __GFP_REPEAT caller really wants to succeed
+		 */
+		if (!nr_reclaimed && !nr_scanned)
+			return false;
+	} else {
+		/*
+		 * For non-__GFP_REPEAT allocations which can presumably
+		 * fail without consequence, stop if we failed to reclaim
+		 * any pages from the last SWAP_CLUSTER_MAX number of
+		 * pages that were scanned. This will return to the
+		 * caller faster at the risk reclaim/compaction and
+		 * the resulting allocation attempt fails
+		 */
+		if (!nr_reclaimed)
+			return false;
+	}
+
+	/*
+	 * If we have not reclaimed enough pages for compaction and the
+	 * inactive lists are large enough, continue reclaiming
+	 */
+	pages_for_compaction = (2UL << sc->order);
+	inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
+	if (get_nr_swap_pages() > 0)
+		inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
+	if (sc->nr_reclaimed < pages_for_compaction &&
+			inactive_lru_pages > pages_for_compaction)
+		return true;
+
+	/* If compaction would go ahead or the allocation would succeed, stop */
+	switch (compaction_suitable(zone, sc->order, 0, 0)) {
+	case COMPACT_PARTIAL:
+	case COMPACT_CONTINUE:
+		return false;
+	default:
+		return true;
+	}
+}
+
+static bool shrink_zone(struct zone *zone, struct scan_control *sc,
+			bool is_classzone)
+{
+	struct reclaim_state *reclaim_state = current->reclaim_state;
+	unsigned long nr_reclaimed, nr_scanned;
+	bool reclaimable = false;
+
+	do {
+		struct mem_cgroup *root = sc->target_mem_cgroup;
+		struct mem_cgroup_reclaim_cookie reclaim = {
+			.zone = zone,
+			.priority = sc->priority,
+		};
+		unsigned long zone_lru_pages = 0;
+		struct mem_cgroup *memcg;
+
+		nr_reclaimed = sc->nr_reclaimed;
+		nr_scanned = sc->nr_scanned;
+
+		memcg = mem_cgroup_iter(root, NULL, &reclaim);
+		do {
+			unsigned long lru_pages;
+			unsigned long scanned;
+			struct lruvec *lruvec;
+			int swappiness;
+
+			if (mem_cgroup_low(root, memcg)) {
+				if (!sc->may_thrash)
+					continue;
+				mem_cgroup_events(memcg, MEMCG_LOW, 1);
+			}
+
+			lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+			swappiness = mem_cgroup_swappiness(memcg);
+			scanned = sc->nr_scanned;
+
+			shrink_lruvec(lruvec, swappiness, sc, &lru_pages);
+			zone_lru_pages += lru_pages;
+
+			if (memcg && is_classzone)
+				shrink_slab(sc->gfp_mask, zone_to_nid(zone),
+					    memcg, sc->nr_scanned - scanned,
+					    lru_pages);
+
+			/*
+			 * Direct reclaim and kswapd have to scan all memory
+			 * cgroups to fulfill the overall scan target for the
+			 * zone.
+			 *
+			 * Limit reclaim, on the other hand, only cares about
+			 * nr_to_reclaim pages to be reclaimed and it will
+			 * retry with decreasing priority if one round over the
+			 * whole hierarchy is not sufficient.
+			 */
+			if (!global_reclaim(sc) &&
+					sc->nr_reclaimed >= sc->nr_to_reclaim) {
+				mem_cgroup_iter_break(root, memcg);
+				break;
+			}
+		} while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
+
+		/*
+		 * Shrink the slab caches in the same proportion that
+		 * the eligible LRU pages were scanned.
+		 */
+		if (global_reclaim(sc) && is_classzone)
+			shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL,
+				    sc->nr_scanned - nr_scanned,
+				    zone_lru_pages);
+
+		if (reclaim_state) {
+			sc->nr_reclaimed += reclaim_state->reclaimed_slab;
+			reclaim_state->reclaimed_slab = 0;
+		}
+
+		vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
+			   sc->nr_scanned - nr_scanned,
+			   sc->nr_reclaimed - nr_reclaimed);
+
+		if (sc->nr_reclaimed - nr_reclaimed)
+			reclaimable = true;
+
+	} while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
+					 sc->nr_scanned - nr_scanned, sc));
+
+	return reclaimable;
+}
+
+/*
+ * Returns true if compaction should go ahead for a high-order request, or
+ * the high-order allocation would succeed without compaction.
+ */
+static inline bool compaction_ready(struct zone *zone, int order)
+{
+	unsigned long balance_gap, watermark;
+	bool watermark_ok;
+
+	/*
+	 * Compaction takes time to run and there are potentially other
+	 * callers using the pages just freed. Continue reclaiming until
+	 * there is a buffer of free pages available to give compaction
+	 * a reasonable chance of completing and allocating the page
+	 */
+	balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+			zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
+	watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);
+	watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
+
+	/*
+	 * If compaction is deferred, reclaim up to a point where
+	 * compaction will have a chance of success when re-enabled
+	 */
+	if (compaction_deferred(zone, order))
+		return watermark_ok;
+
+	/*
+	 * If compaction is not ready to start and allocation is not likely
+	 * to succeed without it, then keep reclaiming.
+	 */
+	if (compaction_suitable(zone, order, 0, 0) == COMPACT_SKIPPED)
+		return false;
+
+	return watermark_ok;
+}
+
+/*
+ * This is the direct reclaim path, for page-allocating processes.  We only
+ * try to reclaim pages from zones which will satisfy the caller's allocation
+ * request.
+ *
+ * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
+ * Because:
+ * a) The caller may be trying to free *extra* pages to satisfy a higher-order
+ *    allocation or
+ * 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.
+ *
+ * If a zone is deemed to be full of pinned pages then just give it a light
+ * scan then give up on it.
+ *
+ * Returns true if a zone was reclaimable.
+ */
+static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
+{
+	struct zoneref *z;
+	struct zone *zone;
+	unsigned long nr_soft_reclaimed;
+	unsigned long nr_soft_scanned;
+	gfp_t orig_mask;
+	enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
+	bool reclaimable = false;
+
+	/*
+	 * If the number of buffer_heads in the machine exceeds the maximum
+	 * allowed level, force direct reclaim to scan the highmem zone as
+	 * highmem pages could be pinning lowmem pages storing buffer_heads
+	 */
+	orig_mask = sc->gfp_mask;
+	if (buffer_heads_over_limit)
+		sc->gfp_mask |= __GFP_HIGHMEM;
+
+	for_each_zone_zonelist_nodemask(zone, z, zonelist,
+					requested_highidx, sc->nodemask) {
+		enum zone_type classzone_idx;
+
+		if (!populated_zone(zone))
+			continue;
+
+		classzone_idx = requested_highidx;
+		while (!populated_zone(zone->zone_pgdat->node_zones +
+							classzone_idx))
+			classzone_idx--;
+
+		/*
+		 * Take care memory controller reclaiming has small influence
+		 * to global LRU.
+		 */
+		if (global_reclaim(sc)) {
+			if (!cpuset_zone_allowed(zone,
+						 GFP_KERNEL | __GFP_HARDWALL))
+				continue;
+
+			if (sc->priority != DEF_PRIORITY &&
+			    !zone_reclaimable(zone))
+				continue;	/* Let kswapd poll it */
+
+			/*
+			 * If we already have plenty of memory free for
+			 * compaction in this zone, don't free any more.
+			 * Even though compaction is invoked for any
+			 * non-zero order, only frequent costly order
+			 * reclamation is disruptive enough to become a
+			 * noticeable problem, like transparent huge
+			 * page allocations.
+			 */
+			if (IS_ENABLED(CONFIG_COMPACTION) &&
+			    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
+			    zonelist_zone_idx(z) <= requested_highidx &&
+			    compaction_ready(zone, sc->order)) {
+				sc->compaction_ready = true;
+				continue;
+			}
+
+			/*
+			 * This steals pages from memory cgroups over softlimit
+			 * and returns the number of reclaimed pages and
+			 * scanned pages. This works for global memory pressure
+			 * and balancing, not for a memcg's limit.
+			 */
+			nr_soft_scanned = 0;
+			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+						sc->order, sc->gfp_mask,
+						&nr_soft_scanned);
+			sc->nr_reclaimed += nr_soft_reclaimed;
+			sc->nr_scanned += nr_soft_scanned;
+			if (nr_soft_reclaimed)
+				reclaimable = true;
+			/* need some check for avoid more shrink_zone() */
+		}
+
+		if (shrink_zone(zone, sc, zone_idx(zone) == classzone_idx))
+			reclaimable = true;
+
+		if (global_reclaim(sc) &&
+		    !reclaimable && zone_reclaimable(zone))
+			reclaimable = true;
+	}
+
+	/*
+	 * Restore to original mask to avoid the impact on the caller if we
+	 * promoted it to __GFP_HIGHMEM.
+	 */
+	sc->gfp_mask = orig_mask;
+
+	return reclaimable;
+}
+
+/*
+ * This is the main entry point to direct page reclaim.
+ *
+ * If a full scan of the inactive list fails to free enough memory then we
+ * are "out of memory" and something needs to be killed.
+ *
+ * If the caller is !__GFP_FS then the probability of a failure is reasonably
+ * high - the zone may be full of dirty or under-writeback pages, which this
+ * caller can't do much about.  We kick 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.
+ *
+ * returns:	0, if no pages reclaimed
+ * 		else, the number of pages reclaimed
+ */
+static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
+					  struct scan_control *sc)
+{
+	int initial_priority = sc->priority;
+	unsigned long total_scanned = 0;
+	unsigned long writeback_threshold;
+	bool zones_reclaimable;
+retry:
+	delayacct_freepages_start();
+
+	if (global_reclaim(sc))
+		count_vm_event(ALLOCSTALL);
+
+	do {
+		vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
+				sc->priority);
+		sc->nr_scanned = 0;
+		zones_reclaimable = shrink_zones(zonelist, sc);
+
+		total_scanned += sc->nr_scanned;
+		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
+			break;
+
+		if (sc->compaction_ready)
+			break;
+
+		/*
+		 * If we're getting trouble reclaiming, start doing
+		 * writepage even in laptop mode.
+		 */
+		if (sc->priority < DEF_PRIORITY - 2)
+			sc->may_writepage = 1;
+
+		/*
+		 * 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.
+		 */
+		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
+		if (total_scanned > writeback_threshold) {
+			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
+						WB_REASON_TRY_TO_FREE_PAGES);
+			sc->may_writepage = 1;
+		}
+	} while (--sc->priority >= 0);
+
+	delayacct_freepages_end();
+
+	if (sc->nr_reclaimed)
+		return sc->nr_reclaimed;
+
+	/* Aborted reclaim to try compaction? don't OOM, then */
+	if (sc->compaction_ready)
+		return 1;
+
+	/* Untapped cgroup reserves?  Don't OOM, retry. */
+	if (!sc->may_thrash) {
+		sc->priority = initial_priority;
+		sc->may_thrash = 1;
+		goto retry;
+	}
+
+	/* Any of the zones still reclaimable?  Don't OOM. */
+	if (zones_reclaimable)
+		return 1;
+
+	return 0;
+}
+
+static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
+{
+	struct zone *zone;
+	unsigned long pfmemalloc_reserve = 0;
+	unsigned long free_pages = 0;
+	int i;
+	bool wmark_ok;
+
+	for (i = 0; i <= ZONE_NORMAL; i++) {
+		zone = &pgdat->node_zones[i];
+		if (!populated_zone(zone))
+			continue;
+
+		pfmemalloc_reserve += min_wmark_pages(zone);
+		free_pages += zone_page_state(zone, NR_FREE_PAGES);
+	}
+
+	/* If there are no reserves (unexpected config) then do not throttle */
+	if (!pfmemalloc_reserve)
+		return true;
+
+	wmark_ok = free_pages > pfmemalloc_reserve / 2;
+
+	/* kswapd must be awake if processes are being throttled */
+	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
+		pgdat->classzone_idx = min(pgdat->classzone_idx,
+						(enum zone_type)ZONE_NORMAL);
+		wake_up_interruptible(&pgdat->kswapd_wait);
+	}
+
+	return wmark_ok;
+}
+
+/*
+ * Throttle direct reclaimers if backing storage is backed by the network
+ * and the PFMEMALLOC reserve for the preferred node is getting dangerously
+ * depleted. kswapd will continue to make progress and wake the processes
+ * when the low watermark is reached.
+ *
+ * Returns true if a fatal signal was delivered during throttling. If this
+ * happens, the page allocator should not consider triggering the OOM killer.
+ */
+static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
+					nodemask_t *nodemask)
+{
+	struct zoneref *z;
+	struct zone *zone;
+	pg_data_t *pgdat = NULL;
+
+	/*
+	 * Kernel threads should not be throttled as they may be indirectly
+	 * responsible for cleaning pages necessary for reclaim to make forward
+	 * progress. kjournald for example may enter direct reclaim while
+	 * committing a transaction where throttling it could forcing other
+	 * processes to block on log_wait_commit().
+	 */
+	if (current->flags & PF_KTHREAD)
+		goto out;
+
+	/*
+	 * If a fatal signal is pending, this process should not throttle.
+	 * It should return quickly so it can exit and free its memory
+	 */
+	if (fatal_signal_pending(current))
+		goto out;
+
+	/*
+	 * Check if the pfmemalloc reserves are ok by finding the first node
+	 * with a usable ZONE_NORMAL or lower zone. The expectation is that
+	 * GFP_KERNEL will be required for allocating network buffers when
+	 * swapping over the network so ZONE_HIGHMEM is unusable.
+	 *
+	 * Throttling is based on the first usable node and throttled processes
+	 * wait on a queue until kswapd makes progress and wakes them. There
+	 * is an affinity then between processes waking up and where reclaim
+	 * progress has been made assuming the process wakes on the same node.
+	 * More importantly, processes running on remote nodes will not compete
+	 * for remote pfmemalloc reserves and processes on different nodes
+	 * should make reasonable progress.
+	 */
+	for_each_zone_zonelist_nodemask(zone, z, zonelist,
+					gfp_zone(gfp_mask), nodemask) {
+		if (zone_idx(zone) > ZONE_NORMAL)
+			continue;
+
+		/* Throttle based on the first usable node */
+		pgdat = zone->zone_pgdat;
+		if (pfmemalloc_watermark_ok(pgdat))
+			goto out;
+		break;
+	}
+
+	/* If no zone was usable by the allocation flags then do not throttle */
+	if (!pgdat)
+		goto out;
+
+	/* Account for the throttling */
+	count_vm_event(PGSCAN_DIRECT_THROTTLE);
+
+	/*
+	 * If the caller cannot enter the filesystem, it's possible that it
+	 * is due to the caller holding an FS lock or performing a journal
+	 * transaction in the case of a filesystem like ext[3|4]. In this case,
+	 * it is not safe to block on pfmemalloc_wait as kswapd could be
+	 * blocked waiting on the same lock. Instead, throttle for up to a
+	 * second before continuing.
+	 */
+	if (!(gfp_mask & __GFP_FS)) {
+		wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
+			pfmemalloc_watermark_ok(pgdat), HZ);
+
+		goto check_pending;
+	}
+
+	/* Throttle until kswapd wakes the process */
+	wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
+		pfmemalloc_watermark_ok(pgdat));
+
+check_pending:
+	if (fatal_signal_pending(current))
+		return true;
+
+out:
+	return false;
+}
+
+unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
+				gfp_t gfp_mask, nodemask_t *nodemask)
+{
+	unsigned long nr_reclaimed;
+	struct scan_control sc = {
+		.nr_to_reclaim = SWAP_CLUSTER_MAX,
+		.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+		.order = order,
+		.nodemask = nodemask,
+		.priority = DEF_PRIORITY,
+		.may_writepage = !laptop_mode,
+		.may_unmap = 1,
+		.may_swap = 1,
+	};
+
+	/*
+	 * Do not enter reclaim if fatal signal was delivered while throttled.
+	 * 1 is returned so that the page allocator does not OOM kill at this
+	 * point.
+	 */
+	if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
+		return 1;
+
+	trace_mm_vmscan_direct_reclaim_begin(order,
+				sc.may_writepage,
+				gfp_mask);
+
+	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
+
+	return nr_reclaimed;
+}
+
+#ifdef CONFIG_MEMCG
+
+unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
+						gfp_t gfp_mask, bool noswap,
+						struct zone *zone,
+						unsigned long *nr_scanned)
+{
+	struct scan_control sc = {
+		.nr_to_reclaim = SWAP_CLUSTER_MAX,
+		.target_mem_cgroup = memcg,
+		.may_writepage = !laptop_mode,
+		.may_unmap = 1,
+		.may_swap = !noswap,
+	};
+	struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+	int swappiness = mem_cgroup_swappiness(memcg);
+	unsigned long lru_pages;
+
+	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
+
+	trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
+						      sc.may_writepage,
+						      sc.gfp_mask);
+
+	/*
+	 * 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_lruvec(lruvec, swappiness, &sc, &lru_pages);
+
+	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
+
+	*nr_scanned = sc.nr_scanned;
+	return sc.nr_reclaimed;
+}
+
+unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+					   unsigned long nr_pages,
+					   gfp_t gfp_mask,
+					   bool may_swap)
+{
+	struct zonelist *zonelist;
+	unsigned long nr_reclaimed;
+	int nid;
+	struct scan_control sc = {
+		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
+		.target_mem_cgroup = memcg,
+		.priority = DEF_PRIORITY,
+		.may_writepage = !laptop_mode,
+		.may_unmap = 1,
+		.may_swap = may_swap,
+	};
+
+	/*
+	 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
+	 * take care of from where we get pages. So the node where we start the
+	 * scan does not need to be the current node.
+	 */
+	nid = mem_cgroup_select_victim_node(memcg);
+
+	zonelist = NODE_DATA(nid)->node_zonelists;
+
+	trace_mm_vmscan_memcg_reclaim_begin(0,
+					    sc.may_writepage,
+					    sc.gfp_mask);
+
+	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+
+	return nr_reclaimed;
+}
+#endif
+
+static void age_active_anon(struct zone *zone, struct scan_control *sc)
+{
+	struct mem_cgroup *memcg;
+
+	if (!total_swap_pages)
+		return;
+
+	memcg = mem_cgroup_iter(NULL, NULL, NULL);
+	do {
+		struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+
+		if (inactive_anon_is_low(lruvec))
+			shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+					   sc, LRU_ACTIVE_ANON);
+
+		memcg = mem_cgroup_iter(NULL, memcg, NULL);
+	} while (memcg);
+}
+
+static bool zone_balanced(struct zone *zone, int order,
+			  unsigned long balance_gap, int classzone_idx)
+{
+	if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
+				    balance_gap, classzone_idx, 0))
+		return false;
+
+	if (IS_ENABLED(CONFIG_COMPACTION) && order && compaction_suitable(zone,
+				order, 0, classzone_idx) == COMPACT_SKIPPED)
+		return false;
+
+	return true;
+}
+
+/*
+ * pgdat_balanced() is used when checking if a node is balanced.
+ *
+ * For order-0, all zones must be balanced!
+ *
+ * For high-order allocations only zones that meet watermarks and are in a
+ * zone allowed by the callers classzone_idx are added to balanced_pages. The
+ * total of balanced pages must be at least 25% of the zones allowed by
+ * classzone_idx for the node to be considered balanced. Forcing all zones to
+ * be balanced for high orders can cause excessive reclaim when there are
+ * imbalanced zones.
+ * The choice of 25% is due to
+ *   o a 16M DMA zone that is balanced will not balance a zone on any
+ *     reasonable sized machine
+ *   o On all other machines, the top zone must be at least a reasonable
+ *     percentage of the middle zones. For example, on 32-bit x86, highmem
+ *     would need to be at least 256M for it to be balance a whole node.
+ *     Similarly, on x86-64 the Normal zone would need to be at least 1G
+ *     to balance a node on its own. These seemed like reasonable ratios.
+ */
+static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
+{
+	unsigned long managed_pages = 0;
+	unsigned long balanced_pages = 0;
+	int i;
+
+	/* Check the watermark levels */
+	for (i = 0; i <= classzone_idx; i++) {
+		struct zone *zone = pgdat->node_zones + i;
+
+		if (!populated_zone(zone))
+			continue;
+
+		managed_pages += zone->managed_pages;
+
+		/*
+		 * A special case here:
+		 *
+		 * balance_pgdat() skips over all_unreclaimable after
+		 * DEF_PRIORITY. Effectively, it considers them balanced so
+		 * they must be considered balanced here as well!
+		 */
+		if (!zone_reclaimable(zone)) {
+			balanced_pages += zone->managed_pages;
+			continue;
+		}
+
+		if (zone_balanced(zone, order, 0, i))
+			balanced_pages += zone->managed_pages;
+		else if (!order)
+			return false;
+	}
+
+	if (order)
+		return balanced_pages >= (managed_pages >> 2);
+	else
+		return true;
+}
+
+/*
+ * Prepare kswapd for sleeping. This verifies that there are no processes
+ * waiting in throttle_direct_reclaim() and that watermarks have been met.
+ *
+ * Returns true if kswapd is ready to sleep
+ */
+static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
+					int classzone_idx)
+{
+	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
+	if (remaining)
+		return false;
+
+	/*
+	 * The throttled processes are normally woken up in balance_pgdat() as
+	 * soon as pfmemalloc_watermark_ok() is true. But there is a potential
+	 * race between when kswapd checks the watermarks and a process gets
+	 * throttled. There is also a potential race if processes get
+	 * throttled, kswapd wakes, a large process exits thereby balancing the
+	 * zones, which causes kswapd to exit balance_pgdat() before reaching
+	 * the wake up checks. If kswapd is going to sleep, no process should
+	 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
+	 * the wake up is premature, processes will wake kswapd and get
+	 * throttled again. The difference from wake ups in balance_pgdat() is
+	 * that here we are under prepare_to_wait().
+	 */
+	if (waitqueue_active(&pgdat->pfmemalloc_wait))
+		wake_up_all(&pgdat->pfmemalloc_wait);
+
+	return pgdat_balanced(pgdat, order, classzone_idx);
+}
+
+/*
+ * kswapd shrinks the zone by the number of pages required to reach
+ * the high watermark.
+ *
+ * Returns true if kswapd scanned at least the requested number of pages to
+ * reclaim or if the lack of progress was due to pages under writeback.
+ * This is used to determine if the scanning priority needs to be raised.
+ */
+static bool kswapd_shrink_zone(struct zone *zone,
+			       int classzone_idx,
+			       struct scan_control *sc,
+			       unsigned long *nr_attempted)
+{
+	int testorder = sc->order;
+	unsigned long balance_gap;
+	bool lowmem_pressure;
+
+	/* Reclaim above the high watermark. */
+	sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
+
+	/*
+	 * Kswapd reclaims only single pages with compaction enabled. Trying
+	 * too hard to reclaim until contiguous free pages have become
+	 * available can hurt performance by evicting too much useful data
+	 * from memory. Do not reclaim more than needed for compaction.
+	 */
+	if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
+			compaction_suitable(zone, sc->order, 0, classzone_idx)
+							!= COMPACT_SKIPPED)
+		testorder = 0;
+
+	/*
+	 * We put equal pressure on every zone, unless one zone has way too
+	 * many pages free already. The "too many pages" is defined as the
+	 * high wmark plus a "gap" where the gap is either the low
+	 * watermark or 1% of the zone, whichever is smaller.
+	 */
+	balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+			zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
+
+	/*
+	 * If there is no low memory pressure or the zone is balanced then no
+	 * reclaim is necessary
+	 */
+	lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
+	if (!lowmem_pressure && zone_balanced(zone, testorder,
+						balance_gap, classzone_idx))
+		return true;
+
+	shrink_zone(zone, sc, zone_idx(zone) == classzone_idx);
+
+	/* Account for the number of pages attempted to reclaim */
+	*nr_attempted += sc->nr_to_reclaim;
+
+	clear_bit(ZONE_WRITEBACK, &zone->flags);
+
+	/*
+	 * If a zone reaches its high watermark, consider it to be no longer
+	 * congested. It's possible there are dirty pages backed by congested
+	 * BDIs but as pressure is relieved, speculatively avoid congestion
+	 * waits.
+	 */
+	if (zone_reclaimable(zone) &&
+	    zone_balanced(zone, testorder, 0, classzone_idx)) {
+		clear_bit(ZONE_CONGESTED, &zone->flags);
+		clear_bit(ZONE_DIRTY, &zone->flags);
+	}
+
+	return sc->nr_scanned >= sc->nr_to_reclaim;
+}
+
+/*
+ * For kswapd, balance_pgdat() will work across all this node's zones until
+ * they are all at high_wmark_pages(zone).
+ *
+ * Returns the final order kswapd was reclaiming at
+ *
+ * There is special handling here for zones which are full of pinned pages.
+ * This can happen if the pages are all mlocked, or if they are all used by
+ * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
+ * What we do is to detect the case where all pages in the zone have been
+ * scanned twice and there has been zero successful reclaim.  Mark the zone as
+ * dead and from now on, only perform a short scan.  Basically we're polling
+ * the zone for when the problem goes away.
+ *
+ * kswapd scans the zones in the highmem->normal->dma direction.  It skips
+ * zones which have free_pages > 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.
+ */
+static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
+							int *classzone_idx)
+{
+	int i;
+	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */
+	unsigned long nr_soft_reclaimed;
+	unsigned long nr_soft_scanned;
+	struct scan_control sc = {
+		.gfp_mask = GFP_KERNEL,
+		.order = order,
+		.priority = DEF_PRIORITY,
+		.may_writepage = !laptop_mode,
+		.may_unmap = 1,
+		.may_swap = 1,
+	};
+	count_vm_event(PAGEOUTRUN);
+
+	do {
+		unsigned long nr_attempted = 0;
+		bool raise_priority = true;
+		bool pgdat_needs_compaction = (order > 0);
+
+		sc.nr_reclaimed = 0;
+
+		/*
+		 * 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;
+
+			if (!populated_zone(zone))
+				continue;
+
+			if (sc.priority != DEF_PRIORITY &&
+			    !zone_reclaimable(zone))
+				continue;
+
+			/*
+			 * Do some background aging of the anon list, to give
+			 * pages a chance to be referenced before reclaiming.
+			 */
+			age_active_anon(zone, &sc);
+
+			/*
+			 * If the number of buffer_heads in the machine
+			 * exceeds the maximum allowed level and this node
+			 * has a highmem zone, force kswapd to reclaim from
+			 * it to relieve lowmem pressure.
+			 */
+			if (buffer_heads_over_limit && is_highmem_idx(i)) {
+				end_zone = i;
+				break;
+			}
+
+			if (!zone_balanced(zone, order, 0, 0)) {
+				end_zone = i;
+				break;
+			} else {
+				/*
+				 * If balanced, clear the dirty and congested
+				 * flags
+				 */
+				clear_bit(ZONE_CONGESTED, &zone->flags);
+				clear_bit(ZONE_DIRTY, &zone->flags);
+			}
+		}
+
+		if (i < 0)
+			goto out;
+
+		for (i = 0; i <= end_zone; i++) {
+			struct zone *zone = pgdat->node_zones + i;
+
+			if (!populated_zone(zone))
+				continue;
+
+			/*
+			 * If any zone is currently balanced then kswapd will
+			 * not call compaction as it is expected that the
+			 * necessary pages are already available.
+			 */
+			if (pgdat_needs_compaction &&
+					zone_watermark_ok(zone, order,
+						low_wmark_pages(zone),
+						*classzone_idx, 0))
+				pgdat_needs_compaction = false;
+		}
+
+		/*
+		 * If we're getting trouble reclaiming, start doing writepage
+		 * even in laptop mode.
+		 */
+		if (sc.priority < DEF_PRIORITY - 2)
+			sc.may_writepage = 1;
+
+		/*
+		 * 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;
+
+			if (!populated_zone(zone))
+				continue;
+
+			if (sc.priority != DEF_PRIORITY &&
+			    !zone_reclaimable(zone))
+				continue;
+
+			sc.nr_scanned = 0;
+
+			nr_soft_scanned = 0;
+			/*
+			 * Call soft limit reclaim before calling shrink_zone.
+			 */
+			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+							order, sc.gfp_mask,
+							&nr_soft_scanned);
+			sc.nr_reclaimed += nr_soft_reclaimed;
+
+			/*
+			 * There should be no need to raise the scanning
+			 * priority if enough pages are already being scanned
+			 * that that high watermark would be met at 100%
+			 * efficiency.
+			 */
+			if (kswapd_shrink_zone(zone, end_zone,
+					       &sc, &nr_attempted))
+				raise_priority = false;
+		}
+
+		/*
+		 * If the low watermark is met there is no need for processes
+		 * to be throttled on pfmemalloc_wait as they should not be
+		 * able to safely make forward progress. Wake them
+		 */
+		if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
+				pfmemalloc_watermark_ok(pgdat))
+			wake_up_all(&pgdat->pfmemalloc_wait);
+
+		/*
+		 * Fragmentation may mean that the system cannot be rebalanced
+		 * for high-order allocations in all zones. If twice the
+		 * allocation size has been reclaimed and the zones are still
+		 * not balanced then recheck the watermarks at order-0 to
+		 * prevent kswapd reclaiming excessively. Assume that a
+		 * process requested a high-order can direct reclaim/compact.
+		 */
+		if (order && sc.nr_reclaimed >= 2UL << order)
+			order = sc.order = 0;
+
+		/* Check if kswapd should be suspending */
+		if (try_to_freeze() || kthread_should_stop())
+			break;
+
+		/*
+		 * Compact if necessary and kswapd is reclaiming at least the
+		 * high watermark number of pages as requsted
+		 */
+		if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
+			compact_pgdat(pgdat, order);
+
+		/*
+		 * Raise priority if scanning rate is too low or there was no
+		 * progress in reclaiming pages
+		 */
+		if (raise_priority || !sc.nr_reclaimed)
+			sc.priority--;
+	} while (sc.priority >= 1 &&
+		 !pgdat_balanced(pgdat, order, *classzone_idx));
+
+out:
+	/*
+	 * Return the order we were reclaiming at so prepare_kswapd_sleep()
+	 * makes a decision on the order we were last reclaiming at. However,
+	 * if another caller entered the allocator slow path while kswapd
+	 * was awake, order will remain at the higher level
+	 */
+	*classzone_idx = end_zone;
+	return order;
+}
+
+static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
+{
+	long remaining = 0;
+	DEFINE_WAIT(wait);
+
+	if (freezing(current) || kthread_should_stop())
+		return;
+
+	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+
+	/* Try to sleep for a short interval */
+	if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
+		remaining = schedule_timeout(HZ/10);
+		finish_wait(&pgdat->kswapd_wait, &wait);
+		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+	}
+
+	/*
+	 * After a short sleep, check if it was a premature sleep. If not, then
+	 * go fully to sleep until explicitly woken up.
+	 */
+	if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
+		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
+
+		/*
+		 * vmstat counters are not perfectly accurate and the estimated
+		 * value for counters such as NR_FREE_PAGES can deviate from the
+		 * true value by nr_online_cpus * threshold. To avoid the zone
+		 * watermarks being breached while under pressure, we reduce the
+		 * per-cpu vmstat threshold while kswapd is awake and restore
+		 * them before going back to sleep.
+		 */
+		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
+
+		/*
+		 * Compaction records what page blocks it recently failed to
+		 * isolate pages from and skips them in the future scanning.
+		 * When kswapd is going to sleep, it is reasonable to assume
+		 * that pages and compaction may succeed so reset the cache.
+		 */
+		reset_isolation_suitable(pgdat);
+
+		if (!kthread_should_stop())
+			schedule();
+
+		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
+	} else {
+		if (remaining)
+			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
+		else
+			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
+	}
+	finish_wait(&pgdat->kswapd_wait, &wait);
+}
+
+/*
+ * The background pageout daemon, started as a kernel thread
+ * from the init process.
+ *
+ * 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, new_order;
+	unsigned balanced_order;
+	int classzone_idx, new_classzone_idx;
+	int balanced_classzone_idx;
+	pg_data_t *pgdat = (pg_data_t*)p;
+	struct task_struct *tsk = current;
+
+	struct reclaim_state reclaim_state = {
+		.reclaimed_slab = 0,
+	};
+	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
+
+	lockdep_set_current_reclaim_state(GFP_KERNEL);
+
+	if (!cpumask_empty(cpumask))
+		set_cpus_allowed_ptr(tsk, cpumask);
+	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).
+	 */
+	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+	set_freezable();
+
+	order = new_order = 0;
+	balanced_order = 0;
+	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
+	balanced_classzone_idx = classzone_idx;
+	for ( ; ; ) {
+		bool ret;
+
+		/*
+		 * If the last balance_pgdat was unsuccessful it's unlikely a
+		 * new request of a similar or harder type will succeed soon
+		 * so consider going to sleep on the basis we reclaimed at
+		 */
+		if (balanced_classzone_idx >= new_classzone_idx &&
+					balanced_order == new_order) {
+			new_order = pgdat->kswapd_max_order;
+			new_classzone_idx = pgdat->classzone_idx;
+			pgdat->kswapd_max_order =  0;
+			pgdat->classzone_idx = pgdat->nr_zones - 1;
+		}
+
+		if (order < new_order || classzone_idx > new_classzone_idx) {
+			/*
+			 * Don't sleep if someone wants a larger 'order'
+			 * allocation or has tigher zone constraints
+			 */
+			order = new_order;
+			classzone_idx = new_classzone_idx;
+		} else {
+			kswapd_try_to_sleep(pgdat, balanced_order,
+						balanced_classzone_idx);
+			order = pgdat->kswapd_max_order;
+			classzone_idx = pgdat->classzone_idx;
+			new_order = order;
+			new_classzone_idx = classzone_idx;
+			pgdat->kswapd_max_order = 0;
+			pgdat->classzone_idx = pgdat->nr_zones - 1;
+		}
+
+		ret = try_to_freeze();
+		if (kthread_should_stop())
+			break;
+
+		/*
+		 * We can speed up thawing tasks if we don't call balance_pgdat
+		 * after returning from the refrigerator
+		 */
+		if (!ret) {
+			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
+			balanced_classzone_idx = classzone_idx;
+			balanced_order = balance_pgdat(pgdat, order,
+						&balanced_classzone_idx);
+		}
+	}
+
+	tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
+	current->reclaim_state = NULL;
+	lockdep_clear_current_reclaim_state();
+
+	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, enum zone_type classzone_idx)
+{
+	pg_data_t *pgdat;
+
+	if (!populated_zone(zone))
+		return;
+
+	if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
+		return;
+	pgdat = zone->zone_pgdat;
+	if (pgdat->kswapd_max_order < order) {
+		pgdat->kswapd_max_order = order;
+		pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
+	}
+	if (!waitqueue_active(&pgdat->kswapd_wait))
+		return;
+	if (zone_balanced(zone, order, 0, 0))
+		return;
+
+	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
+	wake_up_interruptible(&pgdat->kswapd_wait);
+}
+
+#ifdef CONFIG_HIBERNATION
+/*
+ * Try to free `nr_to_reclaim' 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
+ */
+unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
+{
+	struct reclaim_state reclaim_state;
+	struct scan_control sc = {
+		.nr_to_reclaim = nr_to_reclaim,
+		.gfp_mask = GFP_HIGHUSER_MOVABLE,
+		.priority = DEF_PRIORITY,
+		.may_writepage = 1,
+		.may_unmap = 1,
+		.may_swap = 1,
+		.hibernation_mode = 1,
+	};
+	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
+	struct task_struct *p = current;
+	unsigned long nr_reclaimed;
+
+	p->flags |= PF_MEMALLOC;
+	lockdep_set_current_reclaim_state(sc.gfp_mask);
+	reclaim_state.reclaimed_slab = 0;
+	p->reclaim_state = &reclaim_state;
+
+	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+	p->reclaim_state = NULL;
+	lockdep_clear_current_reclaim_state();
+	p->flags &= ~PF_MEMALLOC;
+
+	return nr_reclaimed;
+}
+#endif /* CONFIG_HIBERNATION */
+
+/* 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. */
+static int cpu_callback(struct notifier_block *nfb, unsigned long action,
+			void *hcpu)
+{
+	int nid;
+
+	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
+		for_each_node_state(nid, N_MEMORY) {
+			pg_data_t *pgdat = NODE_DATA(nid);
+			const struct cpumask *mask;
+
+			mask = cpumask_of_node(pgdat->node_id);
+
+			if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
+				/* One of our CPUs online: restore mask */
+				set_cpus_allowed_ptr(pgdat->kswapd, mask);
+		}
+	}
+	return NOTIFY_OK;
+}
+
+/*
+ * 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);
+		pr_err("Failed to start kswapd on node %d\n", nid);
+		ret = PTR_ERR(pgdat->kswapd);
+		pgdat->kswapd = NULL;
+	}
+	return ret;
+}
+
+/*
+ * Called by memory hotplug when all memory in a node is offlined.  Caller must
+ * hold mem_hotplug_begin/end().
+ */
+void kswapd_stop(int nid)
+{
+	struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
+
+	if (kswapd) {
+		kthread_stop(kswapd);
+		NODE_DATA(nid)->kswapd = NULL;
+	}
+}
+
+static int __init kswapd_init(void)
+{
+	int nid;
+
+	swap_setup();
+	for_each_node_state(nid, N_MEMORY)
+ 		kswapd_run(nid);
+	hotcpu_notifier(cpu_callback, 0);
+	return 0;
+}
+
+module_init(kswapd_init)
+
+#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;
+
+#define RECLAIM_OFF 0
+#define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
+#define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
+#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */
+
+/*
+ * 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
+
+/*
+ * Percentage of pages in a zone that must be unmapped for zone_reclaim to
+ * occur.
+ */
+int sysctl_min_unmapped_ratio = 1;
+
+/*
+ * 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;
+
+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;
+}
+
+/*
+ * Try to free up some pages from this zone through reclaim.
+ */
+static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+	/* Minimum pages needed in order to stay on node */
+	const unsigned long nr_pages = 1 << order;
+	struct task_struct *p = current;
+	struct reclaim_state reclaim_state;
+	struct scan_control sc = {
+		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+		.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+		.order = order,
+		.priority = ZONE_RECLAIM_PRIORITY,
+		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
+		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+		.may_swap = 1,
+	};
+
+	cond_resched();
+	/*
+	 * 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;
+	lockdep_set_current_reclaim_state(gfp_mask);
+	reclaim_state.reclaimed_slab = 0;
+	p->reclaim_state = &reclaim_state;
+
+	if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
+		/*
+		 * Free memory by calling shrink zone with increasing
+		 * priorities until we have enough memory freed.
+		 */
+		do {
+			shrink_zone(zone, &sc, true);
+		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
+	}
+
+	p->reclaim_state = NULL;
+	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
+	lockdep_clear_current_reclaim_state();
+	return sc.nr_reclaimed >= nr_pages;
+}
+
+int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+	int node_id;
+	int ret;
+
+	/*
+	 * Zone reclaim reclaims unmapped file backed pages and
+	 * slab pages if we are over the defined limits.
+	 *
+	 * 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.
+	 */
+	if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
+	    zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
+		return ZONE_RECLAIM_FULL;
+
+	if (!zone_reclaimable(zone))
+		return ZONE_RECLAIM_FULL;
+
+	/*
+	 * Do not scan if the allocation should not be delayed.
+	 */
+	if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
+		return ZONE_RECLAIM_NOSCAN;
+
+	/*
+	 * 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.
+	 */
+	node_id = zone_to_nid(zone);
+	if (node_state(node_id, N_CPU) && node_id != numa_node_id())
+		return ZONE_RECLAIM_NOSCAN;
+
+	if (test_and_set_bit(ZONE_RECLAIM_LOCKED, &zone->flags))
+		return ZONE_RECLAIM_NOSCAN;
+
+	ret = __zone_reclaim(zone, gfp_mask, order);
+	clear_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
+
+	if (!ret)
+		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
+
+	return ret;
+}
+#endif
+
+/*
+ * page_evictable - test whether a page is evictable
+ * @page: the page to test
+ *
+ * Test whether page is evictable--i.e., should be placed on active/inactive
+ * lists vs unevictable list.
+ *
+ * Reasons page might not be evictable:
+ * (1) page's mapping marked unevictable
+ * (2) page is part of an mlocked VMA
+ *
+ */
+int page_evictable(struct page *page)
+{
+	return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
+}
+
+#ifdef CONFIG_SHMEM
+/**
+ * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
+ * @pages:	array of pages to check
+ * @nr_pages:	number of pages to check
+ *
+ * Checks pages for evictability and moves them to the appropriate lru list.
+ *
+ * This function is only used for SysV IPC SHM_UNLOCK.
+ */
+void check_move_unevictable_pages(struct page **pages, int nr_pages)
+{
+	struct lruvec *lruvec;
+	struct zone *zone = NULL;
+	int pgscanned = 0;
+	int pgrescued = 0;
+	int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *page = pages[i];
+		struct zone *pagezone;
+
+		pgscanned++;
+		pagezone = page_zone(page);
+		if (pagezone != zone) {
+			if (zone)
+				spin_unlock_irq(&zone->lru_lock);
+			zone = pagezone;
+			spin_lock_irq(&zone->lru_lock);
+		}
+		lruvec = mem_cgroup_page_lruvec(page, zone);
+
+		if (!PageLRU(page) || !PageUnevictable(page))
+			continue;
+
+		if (page_evictable(page)) {
+			enum lru_list lru = page_lru_base_type(page);
+
+			VM_BUG_ON_PAGE(PageActive(page), page);
+			ClearPageUnevictable(page);
+			del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
+			add_page_to_lru_list(page, lruvec, lru);
+			pgrescued++;
+		}
+	}
+
+	if (zone) {
+		__count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
+		__count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+		spin_unlock_irq(&zone->lru_lock);
+	}
+}
+#endif /* CONFIG_SHMEM */