v4.19.13 snapshot.
diff --git a/mm/vmscan.c b/mm/vmscan.c
new file mode 100644
index 0000000..961401c
--- /dev/null
+++ b/mm/vmscan.c
@@ -0,0 +1,4217 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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/sched/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 <linux/dax.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;
+
+ /*
+ * 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;
+
+ /* Writepage batching in laptop mode; RECLAIM_WRITE */
+ 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;
+
+ /*
+ * Cgroups are not reclaimed below their configured memory.low,
+ * unless we threaten to OOM. If any cgroups are skipped due to
+ * memory.low and nothing was reclaimed, go back for memory.low.
+ */
+ unsigned int memcg_low_reclaim:1;
+ unsigned int memcg_low_skipped:1;
+
+ unsigned int hibernation_mode:1;
+
+ /* One of the zones is ready for compaction */
+ unsigned int compaction_ready:1;
+
+ /* Allocation order */
+ s8 order;
+
+ /* Scan (total_size >> priority) pages at once */
+ s8 priority;
+
+ /* The highest zone to isolate pages for reclaim from */
+ s8 reclaim_idx;
+
+ /* This context's GFP mask */
+ gfp_t gfp_mask;
+
+ /* 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;
+
+ struct {
+ unsigned int dirty;
+ unsigned int unqueued_dirty;
+ unsigned int congested;
+ unsigned int writeback;
+ unsigned int immediate;
+ unsigned int file_taken;
+ unsigned int taken;
+ } nr;
+};
+
+#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_KMEM
+
+/*
+ * We allow subsystems to populate their shrinker-related
+ * LRU lists before register_shrinker_prepared() is called
+ * for the shrinker, since we don't want to impose
+ * restrictions on their internal registration order.
+ * In this case shrink_slab_memcg() may find corresponding
+ * bit is set in the shrinkers map.
+ *
+ * This value is used by the function to detect registering
+ * shrinkers and to skip do_shrink_slab() calls for them.
+ */
+#define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
+
+static DEFINE_IDR(shrinker_idr);
+static int shrinker_nr_max;
+
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+ int id, ret = -ENOMEM;
+
+ down_write(&shrinker_rwsem);
+ /* This may call shrinker, so it must use down_read_trylock() */
+ id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
+ if (id < 0)
+ goto unlock;
+
+ if (id >= shrinker_nr_max) {
+ if (memcg_expand_shrinker_maps(id)) {
+ idr_remove(&shrinker_idr, id);
+ goto unlock;
+ }
+
+ shrinker_nr_max = id + 1;
+ }
+ shrinker->id = id;
+ ret = 0;
+unlock:
+ up_write(&shrinker_rwsem);
+ return ret;
+}
+
+static void unregister_memcg_shrinker(struct shrinker *shrinker)
+{
+ int id = shrinker->id;
+
+ BUG_ON(id < 0);
+
+ down_write(&shrinker_rwsem);
+ idr_remove(&shrinker_idr, id);
+ up_write(&shrinker_rwsem);
+}
+#else /* CONFIG_MEMCG_KMEM */
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+ return 0;
+}
+
+static void unregister_memcg_shrinker(struct shrinker *shrinker)
+{
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
+#ifdef CONFIG_MEMCG
+static bool global_reclaim(struct scan_control *sc)
+{
+ return !sc->target_mem_cgroup;
+}
+
+/**
+ * sane_reclaim - is the usual dirty throttling mechanism operational?
+ * @sc: scan_control in question
+ *
+ * The normal page dirty throttling mechanism in balance_dirty_pages() is
+ * completely broken with the legacy memcg and direct stalling in
+ * shrink_page_list() is used for throttling instead, which lacks all the
+ * niceties such as fairness, adaptive pausing, bandwidth proportional
+ * allocation and configurability.
+ *
+ * This function tests whether the vmscan currently in progress can assume
+ * that the normal dirty throttling mechanism is operational.
+ */
+static bool sane_reclaim(struct scan_control *sc)
+{
+ struct mem_cgroup *memcg = sc->target_mem_cgroup;
+
+ if (!memcg)
+ return true;
+#ifdef CONFIG_CGROUP_WRITEBACK
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ return true;
+#endif
+ return false;
+}
+
+static void set_memcg_congestion(pg_data_t *pgdat,
+ struct mem_cgroup *memcg,
+ bool congested)
+{
+ struct mem_cgroup_per_node *mn;
+
+ if (!memcg)
+ return;
+
+ mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
+ WRITE_ONCE(mn->congested, congested);
+}
+
+static bool memcg_congested(pg_data_t *pgdat,
+ struct mem_cgroup *memcg)
+{
+ struct mem_cgroup_per_node *mn;
+
+ mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
+ return READ_ONCE(mn->congested);
+
+}
+#else
+static bool global_reclaim(struct scan_control *sc)
+{
+ return true;
+}
+
+static bool sane_reclaim(struct scan_control *sc)
+{
+ return true;
+}
+
+static inline void set_memcg_congestion(struct pglist_data *pgdat,
+ struct mem_cgroup *memcg, bool congested)
+{
+}
+
+static inline bool memcg_congested(struct pglist_data *pgdat,
+ struct mem_cgroup *memcg)
+{
+ return false;
+
+}
+#endif
+
+/*
+ * This misses isolated pages which are not accounted for to save counters.
+ * As the data only determines if reclaim or compaction continues, it is
+ * not expected that isolated pages will be a dominating factor.
+ */
+unsigned long zone_reclaimable_pages(struct zone *zone)
+{
+ unsigned long nr;
+
+ nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
+ zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
+ if (get_nr_swap_pages() > 0)
+ nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
+ zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
+
+ return nr;
+}
+
+/**
+ * lruvec_lru_size - Returns the number of pages on the given LRU list.
+ * @lruvec: lru vector
+ * @lru: lru to use
+ * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
+ */
+unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx)
+{
+ unsigned long lru_size;
+ int zid;
+
+ if (!mem_cgroup_disabled())
+ lru_size = mem_cgroup_get_lru_size(lruvec, lru);
+ else
+ lru_size = node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru);
+
+ for (zid = zone_idx + 1; zid < MAX_NR_ZONES; zid++) {
+ struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
+ unsigned long size;
+
+ if (!managed_zone(zone))
+ continue;
+
+ if (!mem_cgroup_disabled())
+ size = mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
+ else
+ size = zone_page_state(&lruvec_pgdat(lruvec)->node_zones[zid],
+ NR_ZONE_LRU_BASE + lru);
+ lru_size -= min(size, lru_size);
+ }
+
+ return lru_size;
+
+}
+
+/*
+ * Add a shrinker callback to be called from the vm.
+ */
+int prealloc_shrinker(struct shrinker *shrinker)
+{
+ size_t size = sizeof(*shrinker->nr_deferred);
+
+ if (shrinker->flags & SHRINKER_NUMA_AWARE)
+ size *= nr_node_ids;
+
+ shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
+ if (!shrinker->nr_deferred)
+ return -ENOMEM;
+
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+ if (prealloc_memcg_shrinker(shrinker))
+ goto free_deferred;
+ }
+
+ return 0;
+
+free_deferred:
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+ return -ENOMEM;
+}
+
+void free_prealloced_shrinker(struct shrinker *shrinker)
+{
+ if (!shrinker->nr_deferred)
+ return;
+
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ unregister_memcg_shrinker(shrinker);
+
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+}
+
+void register_shrinker_prepared(struct shrinker *shrinker)
+{
+ down_write(&shrinker_rwsem);
+ list_add_tail(&shrinker->list, &shrinker_list);
+#ifdef CONFIG_MEMCG_KMEM
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ idr_replace(&shrinker_idr, shrinker, shrinker->id);
+#endif
+ up_write(&shrinker_rwsem);
+}
+
+int register_shrinker(struct shrinker *shrinker)
+{
+ int err = prealloc_shrinker(shrinker);
+
+ if (err)
+ return err;
+ register_shrinker_prepared(shrinker);
+ return 0;
+}
+EXPORT_SYMBOL(register_shrinker);
+
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+ if (!shrinker->nr_deferred)
+ return;
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ unregister_memcg_shrinker(shrinker);
+ down_write(&shrinker_rwsem);
+ list_del(&shrinker->list);
+ up_write(&shrinker_rwsem);
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+}
+EXPORT_SYMBOL(unregister_shrinker);
+
+#define SHRINK_BATCH 128
+
+static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+ struct shrinker *shrinker, int priority)
+{
+ 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;
+ long scanned = 0, next_deferred;
+
+ if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+ nid = 0;
+
+ freeable = shrinker->count_objects(shrinker, shrinkctl);
+ if (freeable == 0 || freeable == SHRINK_EMPTY)
+ return freeable;
+
+ /*
+ * 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 = freeable >> priority;
+ delta *= 4;
+ do_div(delta, shrinker->seeks);
+
+ /*
+ * Make sure we apply some minimal pressure on default priority
+ * even on small cgroups. Stale objects are not only consuming memory
+ * by themselves, but can also hold a reference to a dying cgroup,
+ * preventing it from being reclaimed. A dying cgroup with all
+ * corresponding structures like per-cpu stats and kmem caches
+ * can be really big, so it may lead to a significant waste of memory.
+ */
+ delta = max_t(unsigned long long, delta, min(freeable, batch_size));
+
+ 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;
+ next_deferred = nr;
+ } else
+ next_deferred = total_scan;
+
+ /*
+ * 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,
+ freeable, delta, total_scan, priority);
+
+ /*
+ * 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;
+ shrinkctl->nr_scanned = nr_to_scan;
+ ret = shrinker->scan_objects(shrinker, shrinkctl);
+ if (ret == SHRINK_STOP)
+ break;
+ freed += ret;
+
+ count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
+ total_scan -= shrinkctl->nr_scanned;
+ scanned += shrinkctl->nr_scanned;
+
+ cond_resched();
+ }
+
+ if (next_deferred >= scanned)
+ next_deferred -= scanned;
+ else
+ next_deferred = 0;
+ /*
+ * 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 (next_deferred > 0)
+ new_nr = atomic_long_add_return(next_deferred,
+ &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;
+}
+
+#ifdef CONFIG_MEMCG_KMEM
+static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg, int priority)
+{
+ struct memcg_shrinker_map *map;
+ unsigned long ret, freed = 0;
+ int i;
+
+ if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))
+ return 0;
+
+ if (!down_read_trylock(&shrinker_rwsem))
+ return 0;
+
+ map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map,
+ true);
+ if (unlikely(!map))
+ goto unlock;
+
+ for_each_set_bit(i, map->map, shrinker_nr_max) {
+ struct shrink_control sc = {
+ .gfp_mask = gfp_mask,
+ .nid = nid,
+ .memcg = memcg,
+ };
+ struct shrinker *shrinker;
+
+ shrinker = idr_find(&shrinker_idr, i);
+ if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) {
+ if (!shrinker)
+ clear_bit(i, map->map);
+ continue;
+ }
+
+ ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY) {
+ clear_bit(i, map->map);
+ /*
+ * After the shrinker reported that it had no objects to
+ * free, but before we cleared the corresponding bit in
+ * the memcg shrinker map, a new object might have been
+ * added. To make sure, we have the bit set in this
+ * case, we invoke the shrinker one more time and reset
+ * the bit if it reports that it is not empty anymore.
+ * The memory barrier here pairs with the barrier in
+ * memcg_set_shrinker_bit():
+ *
+ * list_lru_add() shrink_slab_memcg()
+ * list_add_tail() clear_bit()
+ * <MB> <MB>
+ * set_bit() do_shrink_slab()
+ */
+ smp_mb__after_atomic();
+ ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY)
+ ret = 0;
+ else
+ memcg_set_shrinker_bit(memcg, nid, i);
+ }
+ freed += ret;
+
+ if (rwsem_is_contended(&shrinker_rwsem)) {
+ freed = freed ? : 1;
+ break;
+ }
+ }
+unlock:
+ up_read(&shrinker_rwsem);
+ return freed;
+}
+#else /* CONFIG_MEMCG_KMEM */
+static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg, int priority)
+{
+ return 0;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
+/**
+ * shrink_slab - shrink slab caches
+ * @gfp_mask: allocation context
+ * @nid: node whose slab caches to target
+ * @memcg: memory cgroup whose slab caches to target
+ * @priority: the reclaim priority
+ *
+ * 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. Unaware shrinkers
+ * are called only if it is the root cgroup.
+ *
+ * @priority is sc->priority, we take the number of objects and >> by priority
+ * in order to get the scan target.
+ *
+ * Returns the number of reclaimed slab objects.
+ */
+static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg,
+ int priority)
+{
+ unsigned long ret, freed = 0;
+ struct shrinker *shrinker;
+
+ if (!mem_cgroup_is_root(memcg))
+ return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
+
+ if (!down_read_trylock(&shrinker_rwsem))
+ goto out;
+
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ struct shrink_control sc = {
+ .gfp_mask = gfp_mask,
+ .nid = nid,
+ .memcg = memcg,
+ };
+
+ ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY)
+ ret = 0;
+ freed += ret;
+ /*
+ * Bail out if someone want to register a new shrinker to
+ * prevent the regsitration from being stalled for long periods
+ * by parallel ongoing shrinking.
+ */
+ if (rwsem_is_contended(&shrinker_rwsem)) {
+ freed = freed ? : 1;
+ break;
+ }
+ }
+
+ 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;
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
+ } 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.
+ */
+ int radix_pins = PageTransHuge(page) && PageSwapCache(page) ?
+ HPAGE_PMD_NR : 1;
+ return page_count(page) - page_has_private(page) == 1 + radix_pins;
+}
+
+static int may_write_to_inode(struct inode *inode, struct scan_control *sc)
+{
+ if (current->flags & PF_SWAPWRITE)
+ return 1;
+ if (!inode_write_congested(inode))
+ return 1;
+ if (inode_to_bdi(inode) == 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_inode(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);
+ inc_node_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)
+{
+ unsigned long flags;
+ int refcount;
+
+ BUG_ON(!PageLocked(page));
+ BUG_ON(mapping != page_mapping(page));
+
+ xa_lock_irqsave(&mapping->i_pages, flags);
+ /*
+ * 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->_refcount.
+ *
+ * Note that if SetPageDirty is always performed via set_page_dirty,
+ * and thus under the i_pages lock, then this ordering is not required.
+ */
+ if (unlikely(PageTransHuge(page)) && PageSwapCache(page))
+ refcount = 1 + HPAGE_PMD_NR;
+ else
+ refcount = 2;
+ if (!page_ref_freeze(page, refcount))
+ goto cannot_free;
+ /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
+ if (unlikely(PageDirty(page))) {
+ page_ref_unfreeze(page, refcount);
+ goto cannot_free;
+ }
+
+ if (PageSwapCache(page)) {
+ swp_entry_t swap = { .val = page_private(page) };
+ mem_cgroup_swapout(page, swap);
+ __delete_from_swap_cache(page);
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+ put_swap_page(page, 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.
+ *
+ * We also don't store shadows for DAX mappings because the
+ * only page cache pages found in these are zero pages
+ * covering holes, and because we don't want to mix DAX
+ * exceptional entries and shadow exceptional entries in the
+ * same address_space.
+ */
+ if (reclaimed && page_is_file_cache(page) &&
+ !mapping_exiting(mapping) && !dax_mapping(mapping))
+ shadow = workingset_eviction(mapping, page);
+ __delete_from_page_cache(page, shadow);
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+
+ if (freepage != NULL)
+ freepage(page);
+ }
+
+ return 1;
+
+cannot_free:
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+ 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_ref_unfreeze(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)
+{
+ lru_cache_add(page);
+ 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) ||
+ (PageAnon(page) && !PageSwapBacked(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 pglist_data *pgdat,
+ struct scan_control *sc,
+ enum ttu_flags ttu_flags,
+ struct reclaim_stat *stat,
+ bool force_reclaim)
+{
+ LIST_HEAD(ret_pages);
+ LIST_HEAD(free_pages);
+ int pgactivate = 0;
+ unsigned nr_unqueued_dirty = 0;
+ unsigned nr_dirty = 0;
+ unsigned nr_congested = 0;
+ unsigned nr_reclaimed = 0;
+ unsigned nr_writeback = 0;
+ unsigned nr_immediate = 0;
+ unsigned nr_ref_keep = 0;
+ unsigned nr_unmap_fail = 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);
+
+ sc->nr_scanned++;
+
+ if (unlikely(!page_evictable(page)))
+ goto activate_locked;
+
+ 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)) &&
+ !(PageAnon(page) && !PageSwapBacked(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 node 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 &&
+ inode_write_congested(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 or new memcg reclaim encounters a page that is
+ * not marked for immediate reclaim, or the caller does not
+ * have __GFP_FS (or __GFP_IO if it's simply going to swap,
+ * not to fs). In this case mark the page for immediate
+ * reclaim and continue scanning.
+ *
+ * Require may_enter_fs because we would wait on fs, which
+ * may not have submitted IO yet. And the loop driver 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.
+ *
+ * 3) Legacy memcg encounters a page that is 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.
+ *
+ * In cases 1) and 2) we activate the pages to get them out of
+ * the way while we continue scanning for clean pages on the
+ * inactive list and refilling from the active list. The
+ * observation here is that waiting for disk writes is more
+ * expensive than potentially causing reloads down the line.
+ * Since they're marked for immediate reclaim, they won't put
+ * memory pressure on the cache working set any longer than it
+ * takes to write them to disk.
+ */
+ if (PageWriteback(page)) {
+ /* Case 1 above */
+ if (current_is_kswapd() &&
+ PageReclaim(page) &&
+ test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
+ nr_immediate++;
+ goto activate_locked;
+
+ /* Case 2 above */
+ } else if (sane_reclaim(sc) ||
+ !PageReclaim(page) || !may_enter_fs) {
+ /*
+ * 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 activate_locked;
+
+ /* Case 3 above */
+ } else {
+ unlock_page(page);
+ wait_on_page_writeback(page);
+ /* then go back and try same page again */
+ list_add_tail(&page->lru, page_list);
+ continue;
+ }
+ }
+
+ if (!force_reclaim)
+ references = page_check_references(page, sc);
+
+ switch (references) {
+ case PAGEREF_ACTIVATE:
+ goto activate_locked;
+ case PAGEREF_KEEP:
+ nr_ref_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.
+ * Lazyfree page could be freed directly
+ */
+ if (PageAnon(page) && PageSwapBacked(page)) {
+ if (!PageSwapCache(page)) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (PageTransHuge(page)) {
+ /* cannot split THP, skip it */
+ if (!can_split_huge_page(page, NULL))
+ goto activate_locked;
+ /*
+ * Split pages without a PMD map right
+ * away. Chances are some or all of the
+ * tail pages can be freed without IO.
+ */
+ if (!compound_mapcount(page) &&
+ split_huge_page_to_list(page,
+ page_list))
+ goto activate_locked;
+ }
+ if (!add_to_swap(page)) {
+ if (!PageTransHuge(page))
+ goto activate_locked;
+ /* Fallback to swap normal pages */
+ if (split_huge_page_to_list(page,
+ page_list))
+ goto activate_locked;
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_vm_event(THP_SWPOUT_FALLBACK);
+#endif
+ if (!add_to_swap(page))
+ goto activate_locked;
+ }
+
+ may_enter_fs = 1;
+
+ /* Adding to swap updated mapping */
+ mapping = page_mapping(page);
+ }
+ } else if (unlikely(PageTransHuge(page))) {
+ /* Split file THP */
+ if (split_huge_page_to_list(page, page_list))
+ goto keep_locked;
+ }
+
+ /*
+ * The page is mapped into the page tables of one or more
+ * processes. Try to unmap it here.
+ */
+ if (page_mapped(page)) {
+ enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
+
+ if (unlikely(PageTransHuge(page)))
+ flags |= TTU_SPLIT_HUGE_PMD;
+ if (!try_to_unmap(page, flags)) {
+ nr_unmap_fail++;
+ goto activate_locked;
+ }
+ }
+
+ if (PageDirty(page)) {
+ /*
+ * Only kswapd can writeback filesystem pages
+ * to avoid risk of stack overflow. But avoid
+ * injecting inefficient single-page IO into
+ * flusher writeback as much as possible: only
+ * write pages when we've encountered many
+ * dirty pages, and when we've already scanned
+ * the rest of the LRU for clean pages and see
+ * the same dirty pages again (PageReclaim).
+ */
+ if (page_is_file_cache(page) &&
+ (!current_is_kswapd() || !PageReclaim(page) ||
+ !test_bit(PGDAT_DIRTY, &pgdat->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_node_page_state(page, NR_VMSCAN_IMMEDIATE);
+ SetPageReclaim(page);
+
+ goto activate_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. Flush the TLB if a writable entry
+ * potentially exists to avoid CPU writes after IO
+ * starts and then write it out here.
+ */
+ try_to_unmap_flush_dirty();
+ 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 (PageAnon(page) && !PageSwapBacked(page)) {
+ /* follow __remove_mapping for reference */
+ if (!page_ref_freeze(page, 1))
+ goto keep_locked;
+ if (PageDirty(page)) {
+ page_ref_unfreeze(page, 1);
+ goto keep_locked;
+ }
+
+ count_vm_event(PGLAZYFREED);
+ count_memcg_page_event(page, PGLAZYFREED);
+ } else 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.
+ */
+ __ClearPageLocked(page);
+free_it:
+ nr_reclaimed++;
+
+ /*
+ * Is there need to periodically free_page_list? It would
+ * appear not as the counts should be low
+ */
+ if (unlikely(PageTransHuge(page))) {
+ mem_cgroup_uncharge(page);
+ (*get_compound_page_dtor(page))(page);
+ } else
+ list_add(&page->lru, &free_pages);
+ continue;
+
+activate_locked:
+ /* Not a candidate for swapping, so reclaim swap space. */
+ if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
+ PageMlocked(page)))
+ try_to_free_swap(page);
+ VM_BUG_ON_PAGE(PageActive(page), page);
+ if (!PageMlocked(page)) {
+ SetPageActive(page);
+ pgactivate++;
+ count_memcg_page_event(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);
+ try_to_unmap_flush();
+ free_unref_page_list(&free_pages);
+
+ list_splice(&ret_pages, page_list);
+ count_vm_events(PGACTIVATE, pgactivate);
+
+ if (stat) {
+ stat->nr_dirty = nr_dirty;
+ stat->nr_congested = nr_congested;
+ stat->nr_unqueued_dirty = nr_unqueued_dirty;
+ stat->nr_writeback = nr_writeback;
+ stat->nr_immediate = nr_immediate;
+ stat->nr_activate = pgactivate;
+ stat->nr_ref_keep = nr_ref_keep;
+ stat->nr_unmap_fail = nr_unmap_fail;
+ }
+ 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;
+ 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) &&
+ !__PageMovable(page)) {
+ ClearPageActive(page);
+ list_move(&page->lru, &clean_pages);
+ }
+ }
+
+ ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
+ TTU_IGNORE_ACCESS, NULL, true);
+ list_splice(&clean_pages, page_list);
+ mod_node_page_state(zone->zone_pgdat, 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_ASYNC_MIGRATE is used to indicate that it only wants to pages
+ * that it is possible to migrate without blocking
+ */
+ if (mode & ISOLATE_ASYNC_MIGRATE) {
+ /* All the caller can do on PageWriteback is block */
+ if (PageWriteback(page))
+ return ret;
+
+ if (PageDirty(page)) {
+ struct address_space *mapping;
+ bool migrate_dirty;
+
+ /*
+ * Only pages without mappings or that have a
+ * ->migratepage callback are possible to migrate
+ * without blocking. However, we can be racing with
+ * truncation so it's necessary to lock the page
+ * to stabilise the mapping as truncation holds
+ * the page lock until after the page is removed
+ * from the page cache.
+ */
+ if (!trylock_page(page))
+ return ret;
+
+ mapping = page_mapping(page);
+ migrate_dirty = !mapping || mapping->a_ops->migratepage;
+ unlock_page(page);
+ if (!migrate_dirty)
+ 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;
+}
+
+
+/*
+ * Update LRU sizes after isolating pages. The LRU size updates must
+ * be complete before mem_cgroup_update_lru_size due to a santity check.
+ */
+static __always_inline void update_lru_sizes(struct lruvec *lruvec,
+ enum lru_list lru, unsigned long *nr_zone_taken)
+{
+ int zid;
+
+ for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+ if (!nr_zone_taken[zid])
+ continue;
+
+ __update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
+#ifdef CONFIG_MEMCG
+ mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
+#endif
+ }
+
+}
+
+/*
+ * 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 eligible 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 nr_zone_taken[MAX_NR_ZONES] = { 0 };
+ unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
+ unsigned long skipped = 0;
+ unsigned long scan, total_scan, nr_pages;
+ LIST_HEAD(pages_skipped);
+
+ scan = 0;
+ for (total_scan = 0;
+ scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src);
+ total_scan++) {
+ struct page *page;
+
+ page = lru_to_page(src);
+ prefetchw_prev_lru_page(page, src, flags);
+
+ VM_BUG_ON_PAGE(!PageLRU(page), page);
+
+ if (page_zonenum(page) > sc->reclaim_idx) {
+ list_move(&page->lru, &pages_skipped);
+ nr_skipped[page_zonenum(page)]++;
+ continue;
+ }
+
+ /*
+ * Do not count skipped pages because that makes the function
+ * return with no isolated pages if the LRU mostly contains
+ * ineligible pages. This causes the VM to not reclaim any
+ * pages, triggering a premature OOM.
+ */
+ scan++;
+ switch (__isolate_lru_page(page, mode)) {
+ case 0:
+ nr_pages = hpage_nr_pages(page);
+ nr_taken += nr_pages;
+ nr_zone_taken[page_zonenum(page)] += nr_pages;
+ list_move(&page->lru, dst);
+ break;
+
+ case -EBUSY:
+ /* else it is being freed elsewhere */
+ list_move(&page->lru, src);
+ continue;
+
+ default:
+ BUG();
+ }
+ }
+
+ /*
+ * Splice any skipped pages to the start of the LRU list. Note that
+ * this disrupts the LRU order when reclaiming for lower zones but
+ * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
+ * scanning would soon rescan the same pages to skip and put the
+ * system at risk of premature OOM.
+ */
+ if (!list_empty(&pages_skipped)) {
+ int zid;
+
+ list_splice(&pages_skipped, src);
+ for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+ if (!nr_skipped[zid])
+ continue;
+
+ __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
+ skipped += nr_skipped[zid];
+ }
+ }
+ *nr_scanned = total_scan;
+ trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
+ total_scan, skipped, nr_taken, mode, lru);
+ update_lru_sizes(lruvec, lru, nr_zone_taken);
+ 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);
+ WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
+
+ if (PageLRU(page)) {
+ struct zone *zone = page_zone(page);
+ struct lruvec *lruvec;
+
+ spin_lock_irq(zone_lru_lock(zone));
+ lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
+ 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(zone));
+ }
+ 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 pglist_data *pgdat, int file,
+ struct scan_control *sc)
+{
+ unsigned long inactive, isolated;
+
+ if (current_is_kswapd())
+ return 0;
+
+ if (!sane_reclaim(sc))
+ return 0;
+
+ if (file) {
+ inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
+ isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
+ } else {
+ inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
+ isolated = node_page_state(pgdat, 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_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
+ 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 pglist_data *pgdat = lruvec_pgdat(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(&pgdat->lru_lock);
+ putback_lru_page(page);
+ spin_lock_irq(&pgdat->lru_lock);
+ continue;
+ }
+
+ lruvec = mem_cgroup_page_lruvec(page, pgdat);
+
+ 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(&pgdat->lru_lock);
+ mem_cgroup_uncharge(page);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&pgdat->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_node(). 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;
+ struct reclaim_stat stat = {};
+ isolate_mode_t isolate_mode = 0;
+ int file = is_file_lru(lru);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+ bool stalled = false;
+
+ while (unlikely(too_many_isolated(pgdat, file, sc))) {
+ if (stalled)
+ return 0;
+
+ /* wait a bit for the reclaimer. */
+ msleep(100);
+ stalled = true;
+
+ /* 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;
+
+ spin_lock_irq(&pgdat->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
+ &nr_scanned, sc, isolate_mode, lru);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
+ reclaim_stat->recent_scanned[file] += nr_taken;
+
+ if (current_is_kswapd()) {
+ if (global_reclaim(sc))
+ __count_vm_events(PGSCAN_KSWAPD, nr_scanned);
+ count_memcg_events(lruvec_memcg(lruvec), PGSCAN_KSWAPD,
+ nr_scanned);
+ } else {
+ if (global_reclaim(sc))
+ __count_vm_events(PGSCAN_DIRECT, nr_scanned);
+ count_memcg_events(lruvec_memcg(lruvec), PGSCAN_DIRECT,
+ nr_scanned);
+ }
+ spin_unlock_irq(&pgdat->lru_lock);
+
+ if (nr_taken == 0)
+ return 0;
+
+ nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, 0,
+ &stat, false);
+
+ spin_lock_irq(&pgdat->lru_lock);
+
+ if (current_is_kswapd()) {
+ if (global_reclaim(sc))
+ __count_vm_events(PGSTEAL_KSWAPD, nr_reclaimed);
+ count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_KSWAPD,
+ nr_reclaimed);
+ } else {
+ if (global_reclaim(sc))
+ __count_vm_events(PGSTEAL_DIRECT, nr_reclaimed);
+ count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_DIRECT,
+ nr_reclaimed);
+ }
+
+ putback_inactive_pages(lruvec, &page_list);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+
+ spin_unlock_irq(&pgdat->lru_lock);
+
+ mem_cgroup_uncharge_list(&page_list);
+ free_unref_page_list(&page_list);
+
+ /*
+ * If dirty pages are scanned that are not queued for IO, it
+ * implies that flushers are not doing their job. This can
+ * happen when memory pressure pushes dirty pages to the end of
+ * the LRU before the dirty limits are breached and the dirty
+ * data has expired. It can also happen when the proportion of
+ * dirty pages grows not through writes but through memory
+ * pressure reclaiming all the clean cache. And in some cases,
+ * the flushers simply cannot keep up with the allocation
+ * rate. Nudge the flusher threads in case they are asleep.
+ */
+ if (stat.nr_unqueued_dirty == nr_taken)
+ wakeup_flusher_threads(WB_REASON_VMSCAN);
+
+ sc->nr.dirty += stat.nr_dirty;
+ sc->nr.congested += stat.nr_congested;
+ sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
+ sc->nr.writeback += stat.nr_writeback;
+ sc->nr.immediate += stat.nr_immediate;
+ sc->nr.taken += nr_taken;
+ if (file)
+ sc->nr.file_taken += nr_taken;
+
+ trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
+ nr_scanned, nr_reclaimed, &stat, sc->priority, 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->_refcount against each page.
+ * But we had to alter page->flags anyway.
+ *
+ * Returns the number of pages moved to the given lru.
+ */
+
+static unsigned move_active_pages_to_lru(struct lruvec *lruvec,
+ struct list_head *list,
+ struct list_head *pages_to_free,
+ enum lru_list lru)
+{
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ struct page *page;
+ int nr_pages;
+ int nr_moved = 0;
+
+ while (!list_empty(list)) {
+ page = lru_to_page(list);
+ lruvec = mem_cgroup_page_lruvec(page, pgdat);
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ SetPageLRU(page);
+
+ nr_pages = hpage_nr_pages(page);
+ update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
+ list_move(&page->lru, &lruvec->lists[lru]);
+
+ if (put_page_testzero(page)) {
+ __ClearPageLRU(page);
+ __ClearPageActive(page);
+ del_page_from_lru_list(page, lruvec, lru);
+
+ if (unlikely(PageCompound(page))) {
+ spin_unlock_irq(&pgdat->lru_lock);
+ mem_cgroup_uncharge(page);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&pgdat->lru_lock);
+ } else
+ list_add(&page->lru, pages_to_free);
+ } else {
+ nr_moved += nr_pages;
+ }
+ }
+
+ if (!is_active_lru(lru)) {
+ __count_vm_events(PGDEACTIVATE, nr_moved);
+ count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
+ nr_moved);
+ }
+
+ return nr_moved;
+}
+
+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 nr_deactivate, nr_activate;
+ unsigned nr_rotated = 0;
+ isolate_mode_t isolate_mode = 0;
+ int file = is_file_lru(lru);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ lru_add_drain();
+
+ if (!sc->may_unmap)
+ isolate_mode |= ISOLATE_UNMAPPED;
+
+ spin_lock_irq(&pgdat->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
+ &nr_scanned, sc, isolate_mode, lru);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
+ reclaim_stat->recent_scanned[file] += nr_taken;
+
+ __count_vm_events(PGREFILL, nr_scanned);
+ count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
+
+ spin_unlock_irq(&pgdat->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(&pgdat->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;
+
+ nr_activate = move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
+ nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+ spin_unlock_irq(&pgdat->lru_lock);
+
+ mem_cgroup_uncharge_list(&l_hold);
+ free_unref_page_list(&l_hold);
+ trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
+ nr_deactivate, nr_rotated, sc->priority, file);
+}
+
+/*
+ * The inactive anon list should be small enough that the VM never has
+ * to do too much work.
+ *
+ * The inactive file list should be small enough to leave most memory
+ * to the established workingset on the scan-resistant active list,
+ * but large enough to avoid thrashing the aggregate readahead window.
+ *
+ * Both inactive lists should also be large enough that each inactive
+ * page has a chance to be referenced again before it is reclaimed.
+ *
+ * If that fails and refaulting is observed, the inactive list grows.
+ *
+ * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
+ * on this LRU, maintained by the pageout code. An inactive_ratio
+ * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
+ *
+ * total target max
+ * memory ratio inactive
+ * -------------------------------------
+ * 10MB 1 5MB
+ * 100MB 1 50MB
+ * 1GB 3 250MB
+ * 10GB 10 0.9GB
+ * 100GB 31 3GB
+ * 1TB 101 10GB
+ * 10TB 320 32GB
+ */
+static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
+ struct mem_cgroup *memcg,
+ struct scan_control *sc, bool actual_reclaim)
+{
+ enum lru_list active_lru = file * LRU_FILE + LRU_ACTIVE;
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ enum lru_list inactive_lru = file * LRU_FILE;
+ unsigned long inactive, active;
+ unsigned long inactive_ratio;
+ unsigned long refaults;
+ unsigned long gb;
+
+ /*
+ * If we don't have swap space, anonymous page deactivation
+ * is pointless.
+ */
+ if (!file && !total_swap_pages)
+ return false;
+
+ inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx);
+ active = lruvec_lru_size(lruvec, active_lru, sc->reclaim_idx);
+
+ if (memcg)
+ refaults = memcg_page_state(memcg, WORKINGSET_ACTIVATE);
+ else
+ refaults = node_page_state(pgdat, WORKINGSET_ACTIVATE);
+
+ /*
+ * When refaults are being observed, it means a new workingset
+ * is being established. Disable active list protection to get
+ * rid of the stale workingset quickly.
+ */
+ if (file && actual_reclaim && lruvec->refaults != refaults) {
+ inactive_ratio = 0;
+ } else {
+ gb = (inactive + active) >> (30 - PAGE_SHIFT);
+ if (gb)
+ inactive_ratio = int_sqrt(10 * gb);
+ else
+ inactive_ratio = 1;
+ }
+
+ if (actual_reclaim)
+ trace_mm_vmscan_inactive_list_is_low(pgdat->node_id, sc->reclaim_idx,
+ lruvec_lru_size(lruvec, inactive_lru, MAX_NR_ZONES), inactive,
+ lruvec_lru_size(lruvec, active_lru, MAX_NR_ZONES), active,
+ inactive_ratio, file);
+
+ return inactive * inactive_ratio < active;
+}
+
+static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct mem_cgroup *memcg,
+ struct scan_control *sc)
+{
+ if (is_active_lru(lru)) {
+ if (inactive_list_is_low(lruvec, is_file_lru(lru),
+ memcg, sc, true))
+ 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, struct mem_cgroup *memcg,
+ struct scan_control *sc, unsigned long *nr,
+ unsigned long *lru_pages)
+{
+ int swappiness = mem_cgroup_swappiness(memcg);
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+ u64 fraction[2];
+ u64 denominator = 0; /* gcc */
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ unsigned long anon_prio, file_prio;
+ enum scan_balance scan_balance;
+ unsigned long anon, file;
+ unsigned long ap, fp;
+ enum lru_list lru;
+
+ /* If we have no swap space, do not bother scanning anon pages. */
+ if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 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 pgdatfile;
+ unsigned long pgdatfree;
+ int z;
+ unsigned long total_high_wmark = 0;
+
+ pgdatfree = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
+ pgdatfile = node_page_state(pgdat, NR_ACTIVE_FILE) +
+ node_page_state(pgdat, NR_INACTIVE_FILE);
+
+ for (z = 0; z < MAX_NR_ZONES; z++) {
+ struct zone *zone = &pgdat->node_zones[z];
+ if (!managed_zone(zone))
+ continue;
+
+ total_high_wmark += high_wmark_pages(zone);
+ }
+
+ if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
+ /*
+ * Force SCAN_ANON if there are enough inactive
+ * anonymous pages on the LRU in eligible zones.
+ * Otherwise, the small LRU gets thrashed.
+ */
+ if (!inactive_list_is_low(lruvec, false, memcg, sc, false) &&
+ lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
+ >> sc->priority) {
+ scan_balance = SCAN_ANON;
+ goto out;
+ }
+ }
+ }
+
+ /*
+ * If there is enough inactive page cache, i.e. if the size of the
+ * inactive list is greater than that of the active list *and* the
+ * inactive list actually has some pages to scan on this priority, we
+ * do not reclaim anything from the anonymous working set right now.
+ * Without the second condition we could end up never scanning an
+ * lruvec even if it has plenty of old anonymous pages unless the
+ * system is under heavy pressure.
+ */
+ if (!inactive_list_is_low(lruvec, true, memcg, sc, false) &&
+ lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
+ 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 = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) +
+ lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES);
+ file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
+ lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES);
+
+ spin_lock_irq(&pgdat->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(&pgdat->lru_lock);
+
+ fraction[0] = ap;
+ fraction[1] = fp;
+ denominator = ap + fp + 1;
+out:
+ *lru_pages = 0;
+ for_each_evictable_lru(lru) {
+ int file = is_file_lru(lru);
+ unsigned long size;
+ unsigned long scan;
+
+ size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
+ scan = size >> sc->priority;
+ /*
+ * If the cgroup's already been deleted, make sure to
+ * scrape out the remaining cache.
+ */
+ if (!scan && !mem_cgroup_online(memcg))
+ 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.
+ * Make sure we don't miss the last page
+ * because of a round-off error.
+ */
+ scan = DIV64_U64_ROUND_UP(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;
+ }
+}
+
+/*
+ * This is a basic per-node page freer. Used by both kswapd and direct reclaim.
+ */
+static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg,
+ struct scan_control *sc, unsigned long *lru_pages)
+{
+ struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);
+ 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, memcg, 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, memcg, sc);
+ }
+ }
+
+ cond_resched();
+
+ 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_list_is_low(lruvec, false, memcg, sc, true))
+ shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+ sc, LRU_ACTIVE_ANON);
+}
+
+/* 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 pglist_data *pgdat,
+ unsigned long nr_reclaimed,
+ unsigned long nr_scanned,
+ struct scan_control *sc)
+{
+ unsigned long pages_for_compaction;
+ unsigned long inactive_lru_pages;
+ int z;
+
+ /* 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_RETRY_MAYFAIL) {
+ /*
+ * For __GFP_RETRY_MAYFAIL 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_RETRY_MAYFAIL caller really wants to succeed
+ */
+ if (!nr_reclaimed && !nr_scanned)
+ return false;
+ } else {
+ /*
+ * For non-__GFP_RETRY_MAYFAIL 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 = compact_gap(sc->order);
+ inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
+ if (get_nr_swap_pages() > 0)
+ inactive_lru_pages += node_page_state(pgdat, 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 */
+ for (z = 0; z <= sc->reclaim_idx; z++) {
+ struct zone *zone = &pgdat->node_zones[z];
+ if (!managed_zone(zone))
+ continue;
+
+ switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
+ case COMPACT_SUCCESS:
+ case COMPACT_CONTINUE:
+ return false;
+ default:
+ /* check next zone */
+ ;
+ }
+ }
+ return true;
+}
+
+static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
+{
+ return test_bit(PGDAT_CONGESTED, &pgdat->flags) ||
+ (memcg && memcg_congested(pgdat, memcg));
+}
+
+static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
+{
+ 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 = {
+ .pgdat = pgdat,
+ .priority = sc->priority,
+ };
+ unsigned long node_lru_pages = 0;
+ struct mem_cgroup *memcg;
+
+ memset(&sc->nr, 0, sizeof(sc->nr));
+
+ nr_reclaimed = sc->nr_reclaimed;
+ nr_scanned = sc->nr_scanned;
+
+ memcg = mem_cgroup_iter(root, NULL, &reclaim);
+ do {
+ unsigned long lru_pages;
+ unsigned long reclaimed;
+ unsigned long scanned;
+
+ switch (mem_cgroup_protected(root, memcg)) {
+ case MEMCG_PROT_MIN:
+ /*
+ * Hard protection.
+ * If there is no reclaimable memory, OOM.
+ */
+ continue;
+ case MEMCG_PROT_LOW:
+ /*
+ * Soft protection.
+ * Respect the protection only as long as
+ * there is an unprotected supply
+ * of reclaimable memory from other cgroups.
+ */
+ if (!sc->memcg_low_reclaim) {
+ sc->memcg_low_skipped = 1;
+ continue;
+ }
+ memcg_memory_event(memcg, MEMCG_LOW);
+ break;
+ case MEMCG_PROT_NONE:
+ break;
+ }
+
+ reclaimed = sc->nr_reclaimed;
+ scanned = sc->nr_scanned;
+ shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
+ node_lru_pages += lru_pages;
+
+ shrink_slab(sc->gfp_mask, pgdat->node_id,
+ memcg, sc->priority);
+
+ /* Record the group's reclaim efficiency */
+ vmpressure(sc->gfp_mask, memcg, false,
+ sc->nr_scanned - scanned,
+ sc->nr_reclaimed - reclaimed);
+
+ /*
+ * Direct reclaim and kswapd have to scan all memory
+ * cgroups to fulfill the overall scan target for the
+ * node.
+ *
+ * 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)));
+
+ if (reclaim_state) {
+ sc->nr_reclaimed += reclaim_state->reclaimed_slab;
+ reclaim_state->reclaimed_slab = 0;
+ }
+
+ /* Record the subtree's reclaim efficiency */
+ vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
+ sc->nr_scanned - nr_scanned,
+ sc->nr_reclaimed - nr_reclaimed);
+
+ if (sc->nr_reclaimed - nr_reclaimed)
+ reclaimable = true;
+
+ if (current_is_kswapd()) {
+ /*
+ * 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 node is flagged PGDAT_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 (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
+ set_bit(PGDAT_WRITEBACK, &pgdat->flags);
+
+ /*
+ * Tag a node as congested if all the dirty pages
+ * scanned were backed by a congested BDI and
+ * wait_iff_congested will stall.
+ */
+ if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
+ set_bit(PGDAT_CONGESTED, &pgdat->flags);
+
+ /* Allow kswapd to start writing pages during reclaim.*/
+ if (sc->nr.unqueued_dirty == sc->nr.file_taken)
+ set_bit(PGDAT_DIRTY, &pgdat->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 (sc->nr.immediate)
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+ }
+
+ /*
+ * Legacy memcg will stall in page writeback so avoid forcibly
+ * stalling in wait_iff_congested().
+ */
+ if (!global_reclaim(sc) && sane_reclaim(sc) &&
+ sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
+ set_memcg_congestion(pgdat, root, true);
+
+ /*
+ * Stall direct reclaim for IO completions if underlying BDIs
+ * and node 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() && pgdat_memcg_congested(pgdat, root))
+ wait_iff_congested(BLK_RW_ASYNC, HZ/10);
+
+ } while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
+ sc->nr_scanned - nr_scanned, sc));
+
+ /*
+ * Kswapd gives up on balancing particular nodes after too
+ * many failures to reclaim anything from them and goes to
+ * sleep. On reclaim progress, reset the failure counter. A
+ * successful direct reclaim run will revive a dormant kswapd.
+ */
+ if (reclaimable)
+ pgdat->kswapd_failures = 0;
+
+ return reclaimable;
+}
+
+/*
+ * Returns true if compaction should go ahead for a costly-order request, or
+ * the allocation would already succeed without compaction. Return false if we
+ * should reclaim first.
+ */
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
+{
+ unsigned long watermark;
+ enum compact_result suitable;
+
+ suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
+ if (suitable == COMPACT_SUCCESS)
+ /* Allocation should succeed already. Don't reclaim. */
+ return true;
+ if (suitable == COMPACT_SKIPPED)
+ /* Compaction cannot yet proceed. Do reclaim. */
+ return false;
+
+ /*
+ * Compaction is already possible, but it takes time to run and there
+ * are potentially other callers using the pages just freed. So proceed
+ * with reclaim to make a buffer of free pages available to give
+ * compaction a reasonable chance of completing and allocating the page.
+ * Note that we won't actually reclaim the whole buffer in one attempt
+ * as the target watermark in should_continue_reclaim() is lower. But if
+ * we are already above the high+gap watermark, don't reclaim at all.
+ */
+ watermark = high_wmark_pages(zone) + compact_gap(sc->order);
+
+ return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
+}
+
+/*
+ * 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.
+ *
+ * If a zone is deemed to be full of pinned pages then just give it a light
+ * scan then give up on it.
+ */
+static void 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;
+ pg_data_t *last_pgdat = NULL;
+
+ /*
+ * 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;
+ sc->reclaim_idx = gfp_zone(sc->gfp_mask);
+ }
+
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ sc->reclaim_idx, sc->nodemask) {
+ /*
+ * 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 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 &&
+ compaction_ready(zone, sc)) {
+ sc->compaction_ready = true;
+ continue;
+ }
+
+ /*
+ * Shrink each node in the zonelist once. If the
+ * zonelist is ordered by zone (not the default) then a
+ * node may be shrunk multiple times but in that case
+ * the user prefers lower zones being preserved.
+ */
+ if (zone->zone_pgdat == last_pgdat)
+ 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->zone_pgdat,
+ sc->order, sc->gfp_mask,
+ &nr_soft_scanned);
+ sc->nr_reclaimed += nr_soft_reclaimed;
+ sc->nr_scanned += nr_soft_scanned;
+ /* need some check for avoid more shrink_zone() */
+ }
+
+ /* See comment about same check for global reclaim above */
+ if (zone->zone_pgdat == last_pgdat)
+ continue;
+ last_pgdat = zone->zone_pgdat;
+ shrink_node(zone->zone_pgdat, sc);
+ }
+
+ /*
+ * Restore to original mask to avoid the impact on the caller if we
+ * promoted it to __GFP_HIGHMEM.
+ */
+ sc->gfp_mask = orig_mask;
+}
+
+static void snapshot_refaults(struct mem_cgroup *root_memcg, pg_data_t *pgdat)
+{
+ struct mem_cgroup *memcg;
+
+ memcg = mem_cgroup_iter(root_memcg, NULL, NULL);
+ do {
+ unsigned long refaults;
+ struct lruvec *lruvec;
+
+ if (memcg)
+ refaults = memcg_page_state(memcg, WORKINGSET_ACTIVATE);
+ else
+ refaults = node_page_state(pgdat, WORKINGSET_ACTIVATE);
+
+ lruvec = mem_cgroup_lruvec(pgdat, memcg);
+ lruvec->refaults = refaults;
+ } while ((memcg = mem_cgroup_iter(root_memcg, memcg, NULL)));
+}
+
+/*
+ * 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;
+ pg_data_t *last_pgdat;
+ struct zoneref *z;
+ struct zone *zone;
+retry:
+ delayacct_freepages_start();
+
+ if (global_reclaim(sc))
+ __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
+
+ do {
+ vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
+ sc->priority);
+ sc->nr_scanned = 0;
+ shrink_zones(zonelist, sc);
+
+ 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;
+ } while (--sc->priority >= 0);
+
+ last_pgdat = NULL;
+ for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
+ sc->nodemask) {
+ if (zone->zone_pgdat == last_pgdat)
+ continue;
+ last_pgdat = zone->zone_pgdat;
+ snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
+ set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false);
+ }
+
+ 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->memcg_low_skipped) {
+ sc->priority = initial_priority;
+ sc->memcg_low_reclaim = 1;
+ sc->memcg_low_skipped = 0;
+ goto retry;
+ }
+
+ return 0;
+}
+
+static bool allow_direct_reclaim(pg_data_t *pgdat)
+{
+ struct zone *zone;
+ unsigned long pfmemalloc_reserve = 0;
+ unsigned long free_pages = 0;
+ int i;
+ bool wmark_ok;
+
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
+ return true;
+
+ for (i = 0; i <= ZONE_NORMAL; i++) {
+ zone = &pgdat->node_zones[i];
+ if (!managed_zone(zone))
+ continue;
+
+ if (!zone_reclaimable_pages(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->kswapd_classzone_idx = min(pgdat->kswapd_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 (allow_direct_reclaim(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,
+ allow_direct_reclaim(pgdat), HZ);
+
+ goto check_pending;
+ }
+
+ /* Throttle until kswapd wakes the process */
+ wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
+ allow_direct_reclaim(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 = current_gfp_context(gfp_mask),
+ .reclaim_idx = gfp_zone(gfp_mask),
+ .order = order,
+ .nodemask = nodemask,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = 1,
+ };
+
+ /*
+ * scan_control uses s8 fields for order, priority, and reclaim_idx.
+ * Confirm they are large enough for max values.
+ */
+ BUILD_BUG_ON(MAX_ORDER > S8_MAX);
+ BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
+ BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
+
+ /*
+ * 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(sc.gfp_mask, zonelist, nodemask))
+ return 1;
+
+ trace_mm_vmscan_direct_reclaim_begin(order,
+ sc.may_writepage,
+ sc.gfp_mask,
+ sc.reclaim_idx);
+
+ 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(struct mem_cgroup *memcg,
+ gfp_t gfp_mask, bool noswap,
+ pg_data_t *pgdat,
+ 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,
+ .reclaim_idx = MAX_NR_ZONES - 1,
+ .may_swap = !noswap,
+ };
+ 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,
+ sc.reclaim_idx);
+
+ /*
+ * 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_node from balance_pgdat
+ * will pick up pages from other mem cgroup's as well. We hack
+ * the priority and make it zero.
+ */
+ shrink_node_memcg(pgdat, memcg, &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;
+ unsigned int noreclaim_flag;
+ struct scan_control sc = {
+ .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+ .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
+ .reclaim_idx = MAX_NR_ZONES - 1,
+ .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[ZONELIST_FALLBACK];
+
+ trace_mm_vmscan_memcg_reclaim_begin(0,
+ sc.may_writepage,
+ sc.gfp_mask,
+ sc.reclaim_idx);
+
+ noreclaim_flag = memalloc_noreclaim_save();
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+ memalloc_noreclaim_restore(noreclaim_flag);
+
+ trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+
+ return nr_reclaimed;
+}
+#endif
+
+static void age_active_anon(struct pglist_data *pgdat,
+ 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_lruvec(pgdat, memcg);
+
+ if (inactive_list_is_low(lruvec, false, memcg, sc, true))
+ shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+ sc, LRU_ACTIVE_ANON);
+
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
+}
+
+/*
+ * Returns true if there is an eligible zone balanced for the request order
+ * and classzone_idx
+ */
+static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ int i;
+ unsigned long mark = -1;
+ struct zone *zone;
+
+ for (i = 0; i <= classzone_idx; i++) {
+ zone = pgdat->node_zones + i;
+
+ if (!managed_zone(zone))
+ continue;
+
+ mark = high_wmark_pages(zone);
+ if (zone_watermark_ok_safe(zone, order, mark, classzone_idx))
+ return true;
+ }
+
+ /*
+ * If a node has no populated zone within classzone_idx, it does not
+ * need balancing by definition. This can happen if a zone-restricted
+ * allocation tries to wake a remote kswapd.
+ */
+ if (mark == -1)
+ return true;
+
+ return false;
+}
+
+/* Clear pgdat state for congested, dirty or under writeback. */
+static void clear_pgdat_congested(pg_data_t *pgdat)
+{
+ clear_bit(PGDAT_CONGESTED, &pgdat->flags);
+ clear_bit(PGDAT_DIRTY, &pgdat->flags);
+ clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
+}
+
+/*
+ * 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, int classzone_idx)
+{
+ /*
+ * The throttled processes are normally woken up in balance_pgdat() as
+ * soon as allow_direct_reclaim() 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);
+
+ /* Hopeless node, leave it to direct reclaim */
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
+ return true;
+
+ if (pgdat_balanced(pgdat, order, classzone_idx)) {
+ clear_pgdat_congested(pgdat);
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * kswapd shrinks a node of pages that are at or below the highest usable
+ * zone that is currently unbalanced.
+ *
+ * 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_node(pg_data_t *pgdat,
+ struct scan_control *sc)
+{
+ struct zone *zone;
+ int z;
+
+ /* Reclaim a number of pages proportional to the number of zones */
+ sc->nr_to_reclaim = 0;
+ for (z = 0; z <= sc->reclaim_idx; z++) {
+ zone = pgdat->node_zones + z;
+ if (!managed_zone(zone))
+ continue;
+
+ sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
+ }
+
+ /*
+ * Historically care was taken to put equal pressure on all zones but
+ * now pressure is applied based on node LRU order.
+ */
+ shrink_node(pgdat, sc);
+
+ /*
+ * Fragmentation may mean that the system cannot be rebalanced for
+ * high-order allocations. If twice the allocation size has been
+ * reclaimed then recheck watermarks only at order-0 to prevent
+ * excessive reclaim. Assume that a process requested a high-order
+ * can direct reclaim/compact.
+ */
+ if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
+ sc->order = 0;
+
+ return sc->nr_scanned >= sc->nr_to_reclaim;
+}
+
+/*
+ * For kswapd, balance_pgdat() will reclaim pages across a node from zones
+ * that are eligible for use by the caller until at least one zone is
+ * balanced.
+ *
+ * Returns the order kswapd finished reclaiming at.
+ *
+ * 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), any page is that zone
+ * or lower is eligible for reclaim until at least one usable zone is
+ * balanced.
+ */
+static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ int i;
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ struct zone *zone;
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .order = order,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = 1,
+ };
+
+ __fs_reclaim_acquire();
+
+ count_vm_event(PAGEOUTRUN);
+
+ do {
+ unsigned long nr_reclaimed = sc.nr_reclaimed;
+ bool raise_priority = true;
+ bool ret;
+
+ sc.reclaim_idx = classzone_idx;
+
+ /*
+ * If the number of buffer_heads exceeds the maximum allowed
+ * then consider reclaiming from all zones. This has a dual
+ * purpose -- on 64-bit systems it is expected that
+ * buffer_heads are stripped during active rotation. On 32-bit
+ * systems, highmem pages can pin lowmem memory and shrinking
+ * buffers can relieve lowmem pressure. Reclaim may still not
+ * go ahead if all eligible zones for the original allocation
+ * request are balanced to avoid excessive reclaim from kswapd.
+ */
+ if (buffer_heads_over_limit) {
+ for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
+ zone = pgdat->node_zones + i;
+ if (!managed_zone(zone))
+ continue;
+
+ sc.reclaim_idx = i;
+ break;
+ }
+ }
+
+ /*
+ * Only reclaim if there are no eligible zones. Note that
+ * sc.reclaim_idx is not used as buffer_heads_over_limit may
+ * have adjusted it.
+ */
+ if (pgdat_balanced(pgdat, sc.order, classzone_idx))
+ goto out;
+
+ /*
+ * Do some background aging of the anon list, to give
+ * pages a chance to be referenced before reclaiming. All
+ * pages are rotated regardless of classzone as this is
+ * about consistent aging.
+ */
+ age_active_anon(pgdat, &sc);
+
+ /*
+ * If we're getting trouble reclaiming, start doing writepage
+ * even in laptop mode.
+ */
+ if (sc.priority < DEF_PRIORITY - 2)
+ sc.may_writepage = 1;
+
+ /* Call soft limit reclaim before calling shrink_node. */
+ sc.nr_scanned = 0;
+ nr_soft_scanned = 0;
+ nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.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_node(pgdat, &sc))
+ 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) &&
+ allow_direct_reclaim(pgdat))
+ wake_up_all(&pgdat->pfmemalloc_wait);
+
+ /* Check if kswapd should be suspending */
+ __fs_reclaim_release();
+ ret = try_to_freeze();
+ __fs_reclaim_acquire();
+ if (ret || kthread_should_stop())
+ break;
+
+ /*
+ * Raise priority if scanning rate is too low or there was no
+ * progress in reclaiming pages
+ */
+ nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
+ if (raise_priority || !nr_reclaimed)
+ sc.priority--;
+ } while (sc.priority >= 1);
+
+ if (!sc.nr_reclaimed)
+ pgdat->kswapd_failures++;
+
+out:
+ snapshot_refaults(NULL, pgdat);
+ __fs_reclaim_release();
+ /*
+ * Return the order kswapd stopped reclaiming at as
+ * prepare_kswapd_sleep() takes it into account. If another caller
+ * entered the allocator slow path while kswapd was awake, order will
+ * remain at the higher level.
+ */
+ return sc.order;
+}
+
+/*
+ * pgdat->kswapd_classzone_idx is the highest zone index that a recent
+ * allocation request woke kswapd for. When kswapd has not woken recently,
+ * the value is MAX_NR_ZONES which is not a valid index. This compares a
+ * given classzone and returns it or the highest classzone index kswapd
+ * was recently woke for.
+ */
+static enum zone_type kswapd_classzone_idx(pg_data_t *pgdat,
+ enum zone_type classzone_idx)
+{
+ if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES)
+ return classzone_idx;
+
+ return max(pgdat->kswapd_classzone_idx, classzone_idx);
+}
+
+static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
+ unsigned 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. Note that kcompactd will only be
+ * woken if it is possible to sleep for a short interval. This is
+ * deliberate on the assumption that if reclaim cannot keep an
+ * eligible zone balanced that it's also unlikely that compaction will
+ * succeed.
+ */
+ if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
+ /*
+ * 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);
+
+ /*
+ * We have freed the memory, now we should compact it to make
+ * allocation of the requested order possible.
+ */
+ wakeup_kcompactd(pgdat, alloc_order, classzone_idx);
+
+ remaining = schedule_timeout(HZ/10);
+
+ /*
+ * If woken prematurely then reset kswapd_classzone_idx and
+ * order. The values will either be from a wakeup request or
+ * the previous request that slept prematurely.
+ */
+ if (remaining) {
+ pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
+ pgdat->kswapd_order = max(pgdat->kswapd_order, reclaim_order);
+ }
+
+ 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 (!remaining &&
+ prepare_kswapd_sleep(pgdat, reclaim_order, 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);
+
+ 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 int alloc_order, reclaim_order;
+ unsigned int classzone_idx = MAX_NR_ZONES - 1;
+ 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);
+
+ 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();
+
+ pgdat->kswapd_order = 0;
+ pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
+ for ( ; ; ) {
+ bool ret;
+
+ alloc_order = reclaim_order = pgdat->kswapd_order;
+ classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
+
+kswapd_try_sleep:
+ kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
+ classzone_idx);
+
+ /* Read the new order and classzone_idx */
+ alloc_order = reclaim_order = pgdat->kswapd_order;
+ classzone_idx = kswapd_classzone_idx(pgdat, 0);
+ pgdat->kswapd_order = 0;
+ pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
+
+ 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)
+ continue;
+
+ /*
+ * Reclaim begins at the requested order but if a high-order
+ * reclaim fails then kswapd falls back to reclaiming for
+ * order-0. If that happens, kswapd will consider sleeping
+ * for the order it finished reclaiming at (reclaim_order)
+ * but kcompactd is woken to compact for the original
+ * request (alloc_order).
+ */
+ trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx,
+ alloc_order);
+ reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
+ if (reclaim_order < alloc_order)
+ goto kswapd_try_sleep;
+ }
+
+ tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
+ current->reclaim_state = NULL;
+
+ return 0;
+}
+
+/*
+ * A zone is low on free memory or too fragmented for high-order memory. If
+ * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
+ * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
+ * has failed or is not needed, still wake up kcompactd if only compaction is
+ * needed.
+ */
+void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
+ enum zone_type classzone_idx)
+{
+ pg_data_t *pgdat;
+
+ if (!managed_zone(zone))
+ return;
+
+ if (!cpuset_zone_allowed(zone, gfp_flags))
+ return;
+ pgdat = zone->zone_pgdat;
+ pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat,
+ classzone_idx);
+ pgdat->kswapd_order = max(pgdat->kswapd_order, order);
+ if (!waitqueue_active(&pgdat->kswapd_wait))
+ return;
+
+ /* Hopeless node, leave it to direct reclaim if possible */
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
+ pgdat_balanced(pgdat, order, classzone_idx)) {
+ /*
+ * There may be plenty of free memory available, but it's too
+ * fragmented for high-order allocations. Wake up kcompactd
+ * and rely on compaction_suitable() to determine if it's
+ * needed. If it fails, it will defer subsequent attempts to
+ * ratelimit its work.
+ */
+ if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
+ wakeup_kcompactd(pgdat, order, classzone_idx);
+ return;
+ }
+
+ trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, classzone_idx, order,
+ gfp_flags);
+ 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,
+ .reclaim_idx = MAX_NR_ZONES - 1,
+ .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;
+ unsigned int noreclaim_flag;
+
+ fs_reclaim_acquire(sc.gfp_mask);
+ noreclaim_flag = memalloc_noreclaim_save();
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ p->reclaim_state = NULL;
+ memalloc_noreclaim_restore(noreclaim_flag);
+ fs_reclaim_release(sc.gfp_mask);
+
+ 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 kswapd_cpu_online(unsigned int cpu)
+{
+ int nid;
+
+ 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 0;
+}
+
+/*
+ * 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_RUNNING);
+ 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, ret;
+
+ swap_setup();
+ for_each_node_state(nid, N_MEMORY)
+ kswapd_run(nid);
+ ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "mm/vmscan:online", kswapd_cpu_online,
+ NULL);
+ WARN_ON(ret < 0);
+ return 0;
+}
+
+module_init(kswapd_init)
+
+#ifdef CONFIG_NUMA
+/*
+ * Node reclaim mode
+ *
+ * If non-zero call node_reclaim when the number of free pages falls below
+ * the watermarks.
+ */
+int node_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_UNMAP (1<<2) /* Unmap pages during reclaim */
+
+/*
+ * Priority for NODE_RECLAIM. This determines the fraction of pages
+ * of a node considered for each zone_reclaim. 4 scans 1/16th of
+ * a zone.
+ */
+#define NODE_RECLAIM_PRIORITY 4
+
+/*
+ * Percentage of pages in a zone that must be unmapped for node_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 node_unmapped_file_pages(struct pglist_data *pgdat)
+{
+ unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
+ unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
+ node_page_state(pgdat, 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 unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
+{
+ unsigned long nr_pagecache_reclaimable;
+ unsigned long delta = 0;
+
+ /*
+ * If RECLAIM_UNMAP is set, then all file pages are considered
+ * potentially reclaimable. Otherwise, we have to worry about
+ * pages like swapcache and node_unmapped_file_pages() provides
+ * a better estimate
+ */
+ if (node_reclaim_mode & RECLAIM_UNMAP)
+ nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
+ else
+ nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
+
+ /* If we can't clean pages, remove dirty pages from consideration */
+ if (!(node_reclaim_mode & RECLAIM_WRITE))
+ delta += node_page_state(pgdat, 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 node through reclaim.
+ */
+static int __node_reclaim(struct pglist_data *pgdat, 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;
+ unsigned int noreclaim_flag;
+ struct scan_control sc = {
+ .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+ .gfp_mask = current_gfp_context(gfp_mask),
+ .order = order,
+ .priority = NODE_RECLAIM_PRIORITY,
+ .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
+ .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
+ .may_swap = 1,
+ .reclaim_idx = gfp_zone(gfp_mask),
+ };
+
+ cond_resched();
+ fs_reclaim_acquire(sc.gfp_mask);
+ /*
+ * We need to be able to allocate from the reserves for RECLAIM_UNMAP
+ * and we also need to be able to write out pages for RECLAIM_WRITE
+ * and RECLAIM_UNMAP.
+ */
+ noreclaim_flag = memalloc_noreclaim_save();
+ p->flags |= PF_SWAPWRITE;
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) {
+ /*
+ * Free memory by calling shrink node with increasing
+ * priorities until we have enough memory freed.
+ */
+ do {
+ shrink_node(pgdat, &sc);
+ } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
+ }
+
+ p->reclaim_state = NULL;
+ current->flags &= ~PF_SWAPWRITE;
+ memalloc_noreclaim_restore(noreclaim_flag);
+ fs_reclaim_release(sc.gfp_mask);
+ return sc.nr_reclaimed >= nr_pages;
+}
+
+int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
+{
+ int ret;
+
+ /*
+ * Node 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 node is overallocated. So we do not reclaim
+ * if less than a specified percentage of the node is used by
+ * unmapped file backed pages.
+ */
+ if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
+ node_page_state(pgdat, NR_SLAB_RECLAIMABLE) <= pgdat->min_slab_pages)
+ return NODE_RECLAIM_FULL;
+
+ /*
+ * Do not scan if the allocation should not be delayed.
+ */
+ if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
+ return NODE_RECLAIM_NOSCAN;
+
+ /*
+ * Only run node reclaim on the local node or on nodes 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.
+ */
+ if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
+ return NODE_RECLAIM_NOSCAN;
+
+ if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
+ return NODE_RECLAIM_NOSCAN;
+
+ ret = __node_reclaim(pgdat, gfp_mask, order);
+ clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->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)
+{
+ int ret;
+
+ /* Prevent address_space of inode and swap cache from being freed */
+ rcu_read_lock();
+ ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
+ rcu_read_unlock();
+ return ret;
+}
+
+#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 pglist_data *pgdat = NULL;
+ int pgscanned = 0;
+ int pgrescued = 0;
+ int i;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pages[i];
+ struct pglist_data *pagepgdat = page_pgdat(page);
+
+ pgscanned++;
+ if (pagepgdat != pgdat) {
+ if (pgdat)
+ spin_unlock_irq(&pgdat->lru_lock);
+ pgdat = pagepgdat;
+ spin_lock_irq(&pgdat->lru_lock);
+ }
+ lruvec = mem_cgroup_page_lruvec(page, pgdat);
+
+ 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 (pgdat) {
+ __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
+ __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+ spin_unlock_irq(&pgdat->lru_lock);
+ }
+}
+#endif /* CONFIG_SHMEM */