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-rw-r--r--mm/vmscan.c8183
1 files changed, 8183 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
new file mode 100644
index 0000000000..0dfb9a75df
--- /dev/null
+++ b/mm/vmscan.c
@@ -0,0 +1,8183 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 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/migrate.h>
+#include <linux/delayacct.h>
+#include <linux/sysctl.h>
+#include <linux/memory-tiers.h>
+#include <linux/oom.h>
+#include <linux/pagevec.h>
+#include <linux/prefetch.h>
+#include <linux/printk.h>
+#include <linux/dax.h>
+#include <linux/psi.h>
+#include <linux/pagewalk.h>
+#include <linux/shmem_fs.h>
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
+#include <linux/khugepaged.h>
+#include <linux/rculist_nulls.h>
+#include <linux/random.h>
+
+#include <asm/tlbflush.h>
+#include <asm/div64.h>
+
+#include <linux/swapops.h>
+#include <linux/balloon_compaction.h>
+#include <linux/sched/sysctl.h>
+
+#include "internal.h"
+#include "swap.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;
+
+ /*
+ * Scan pressure balancing between anon and file LRUs
+ */
+ unsigned long anon_cost;
+ unsigned long file_cost;
+
+ /* Can active folios be deactivated as part of reclaim? */
+#define DEACTIVATE_ANON 1
+#define DEACTIVATE_FILE 2
+ unsigned int may_deactivate:2;
+ unsigned int force_deactivate:1;
+ unsigned int skipped_deactivate:1;
+
+ /* Writepage batching in laptop mode; RECLAIM_WRITE */
+ unsigned int may_writepage:1;
+
+ /* Can mapped folios be reclaimed? */
+ unsigned int may_unmap:1;
+
+ /* Can folios be swapped as part of reclaim? */
+ unsigned int may_swap:1;
+
+ /* Proactive reclaim invoked by userspace through memory.reclaim */
+ unsigned int proactive:1;
+
+ /*
+ * Cgroup memory below memory.low is protected as long as we
+ * don't threaten to OOM. If any cgroup is reclaimed at
+ * reduced force or passed over entirely due to its memory.low
+ * setting (memcg_low_skipped), and nothing is reclaimed as a
+ * result, then go back for one more cycle that reclaims the protected
+ * memory (memcg_low_reclaim) to avert OOM.
+ */
+ 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;
+
+ /* There is easily reclaimable cold cache in the current node */
+ unsigned int cache_trim_mode:1;
+
+ /* The file folios on the current node are dangerously low */
+ unsigned int file_is_tiny:1;
+
+ /* Always discard instead of demoting to lower tier memory */
+ unsigned int no_demotion:1;
+
+ /* Allocation order */
+ s8 order;
+
+ /* Scan (total_size >> priority) pages at once */
+ s8 priority;
+
+ /* The highest zone to isolate folios 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;
+
+ /* for recording the reclaimed slab by now */
+ struct reclaim_state reclaim_state;
+};
+
+#ifdef ARCH_HAS_PREFETCHW
+#define prefetchw_prev_lru_folio(_folio, _base, _field) \
+ do { \
+ if ((_folio)->lru.prev != _base) { \
+ struct folio *prev; \
+ \
+ prev = lru_to_folio(&(_folio->lru)); \
+ prefetchw(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
+#endif
+
+/*
+ * From 0 .. 200. Higher means more swappy.
+ */
+int vm_swappiness = 60;
+
+LIST_HEAD(shrinker_list);
+DECLARE_RWSEM(shrinker_rwsem);
+
+#ifdef CONFIG_MEMCG
+static int shrinker_nr_max;
+
+/* The shrinker_info is expanded in a batch of BITS_PER_LONG */
+static inline int shrinker_map_size(int nr_items)
+{
+ return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
+}
+
+static inline int shrinker_defer_size(int nr_items)
+{
+ return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t));
+}
+
+static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
+ int nid)
+{
+ return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
+ lockdep_is_held(&shrinker_rwsem));
+}
+
+static int expand_one_shrinker_info(struct mem_cgroup *memcg,
+ int map_size, int defer_size,
+ int old_map_size, int old_defer_size,
+ int new_nr_max)
+{
+ struct shrinker_info *new, *old;
+ struct mem_cgroup_per_node *pn;
+ int nid;
+ int size = map_size + defer_size;
+
+ for_each_node(nid) {
+ pn = memcg->nodeinfo[nid];
+ old = shrinker_info_protected(memcg, nid);
+ /* Not yet online memcg */
+ if (!old)
+ return 0;
+
+ /* Already expanded this shrinker_info */
+ if (new_nr_max <= old->map_nr_max)
+ continue;
+
+ new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
+ if (!new)
+ return -ENOMEM;
+
+ new->nr_deferred = (atomic_long_t *)(new + 1);
+ new->map = (void *)new->nr_deferred + defer_size;
+ new->map_nr_max = new_nr_max;
+
+ /* map: set all old bits, clear all new bits */
+ memset(new->map, (int)0xff, old_map_size);
+ memset((void *)new->map + old_map_size, 0, map_size - old_map_size);
+ /* nr_deferred: copy old values, clear all new values */
+ memcpy(new->nr_deferred, old->nr_deferred, old_defer_size);
+ memset((void *)new->nr_deferred + old_defer_size, 0,
+ defer_size - old_defer_size);
+
+ rcu_assign_pointer(pn->shrinker_info, new);
+ kvfree_rcu(old, rcu);
+ }
+
+ return 0;
+}
+
+void free_shrinker_info(struct mem_cgroup *memcg)
+{
+ struct mem_cgroup_per_node *pn;
+ struct shrinker_info *info;
+ int nid;
+
+ for_each_node(nid) {
+ pn = memcg->nodeinfo[nid];
+ info = rcu_dereference_protected(pn->shrinker_info, true);
+ kvfree(info);
+ rcu_assign_pointer(pn->shrinker_info, NULL);
+ }
+}
+
+int alloc_shrinker_info(struct mem_cgroup *memcg)
+{
+ struct shrinker_info *info;
+ int nid, size, ret = 0;
+ int map_size, defer_size = 0;
+
+ down_write(&shrinker_rwsem);
+ map_size = shrinker_map_size(shrinker_nr_max);
+ defer_size = shrinker_defer_size(shrinker_nr_max);
+ size = map_size + defer_size;
+ for_each_node(nid) {
+ info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
+ if (!info) {
+ free_shrinker_info(memcg);
+ ret = -ENOMEM;
+ break;
+ }
+ info->nr_deferred = (atomic_long_t *)(info + 1);
+ info->map = (void *)info->nr_deferred + defer_size;
+ info->map_nr_max = shrinker_nr_max;
+ rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
+ }
+ up_write(&shrinker_rwsem);
+
+ return ret;
+}
+
+static int expand_shrinker_info(int new_id)
+{
+ int ret = 0;
+ int new_nr_max = round_up(new_id + 1, BITS_PER_LONG);
+ int map_size, defer_size = 0;
+ int old_map_size, old_defer_size = 0;
+ struct mem_cgroup *memcg;
+
+ if (!root_mem_cgroup)
+ goto out;
+
+ lockdep_assert_held(&shrinker_rwsem);
+
+ map_size = shrinker_map_size(new_nr_max);
+ defer_size = shrinker_defer_size(new_nr_max);
+ old_map_size = shrinker_map_size(shrinker_nr_max);
+ old_defer_size = shrinker_defer_size(shrinker_nr_max);
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ ret = expand_one_shrinker_info(memcg, map_size, defer_size,
+ old_map_size, old_defer_size,
+ new_nr_max);
+ if (ret) {
+ mem_cgroup_iter_break(NULL, memcg);
+ goto out;
+ }
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+out:
+ if (!ret)
+ shrinker_nr_max = new_nr_max;
+
+ return ret;
+}
+
+void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
+{
+ if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
+ struct shrinker_info *info;
+
+ rcu_read_lock();
+ info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
+ if (!WARN_ON_ONCE(shrinker_id >= info->map_nr_max)) {
+ /* Pairs with smp mb in shrink_slab() */
+ smp_mb__before_atomic();
+ set_bit(shrinker_id, info->map);
+ }
+ rcu_read_unlock();
+ }
+}
+
+static DEFINE_IDR(shrinker_idr);
+
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+ int id, ret = -ENOMEM;
+
+ if (mem_cgroup_disabled())
+ return -ENOSYS;
+
+ down_write(&shrinker_rwsem);
+ /* This may call shrinker, so it must use down_read_trylock() */
+ id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
+ if (id < 0)
+ goto unlock;
+
+ if (id >= shrinker_nr_max) {
+ if (expand_shrinker_info(id)) {
+ idr_remove(&shrinker_idr, id);
+ goto unlock;
+ }
+ }
+ 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);
+
+ lockdep_assert_held(&shrinker_rwsem);
+
+ idr_remove(&shrinker_idr, id);
+}
+
+static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
+ struct mem_cgroup *memcg)
+{
+ struct shrinker_info *info;
+
+ info = shrinker_info_protected(memcg, nid);
+ return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
+}
+
+static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
+ struct mem_cgroup *memcg)
+{
+ struct shrinker_info *info;
+
+ info = shrinker_info_protected(memcg, nid);
+ return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
+}
+
+void reparent_shrinker_deferred(struct mem_cgroup *memcg)
+{
+ int i, nid;
+ long nr;
+ struct mem_cgroup *parent;
+ struct shrinker_info *child_info, *parent_info;
+
+ parent = parent_mem_cgroup(memcg);
+ if (!parent)
+ parent = root_mem_cgroup;
+
+ /* Prevent from concurrent shrinker_info expand */
+ down_read(&shrinker_rwsem);
+ for_each_node(nid) {
+ child_info = shrinker_info_protected(memcg, nid);
+ parent_info = shrinker_info_protected(parent, nid);
+ for (i = 0; i < child_info->map_nr_max; i++) {
+ nr = atomic_long_read(&child_info->nr_deferred[i]);
+ atomic_long_add(nr, &parent_info->nr_deferred[i]);
+ }
+ }
+ up_read(&shrinker_rwsem);
+}
+
+/* Returns true for reclaim through cgroup limits or cgroup interfaces. */
+static bool cgroup_reclaim(struct scan_control *sc)
+{
+ return sc->target_mem_cgroup;
+}
+
+/*
+ * Returns true for reclaim on the root cgroup. This is true for direct
+ * allocator reclaim and reclaim through cgroup interfaces on the root cgroup.
+ */
+static bool root_reclaim(struct scan_control *sc)
+{
+ return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup);
+}
+
+/**
+ * writeback_throttling_sane - is the usual dirty throttling mechanism available?
+ * @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_folio_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 writeback_throttling_sane(struct scan_control *sc)
+{
+ if (!cgroup_reclaim(sc))
+ return true;
+#ifdef CONFIG_CGROUP_WRITEBACK
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ return true;
+#endif
+ return false;
+}
+#else
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+ return -ENOSYS;
+}
+
+static void unregister_memcg_shrinker(struct shrinker *shrinker)
+{
+}
+
+static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
+ struct mem_cgroup *memcg)
+{
+ return 0;
+}
+
+static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
+ struct mem_cgroup *memcg)
+{
+ return 0;
+}
+
+static bool cgroup_reclaim(struct scan_control *sc)
+{
+ return false;
+}
+
+static bool root_reclaim(struct scan_control *sc)
+{
+ return true;
+}
+
+static bool writeback_throttling_sane(struct scan_control *sc)
+{
+ return true;
+}
+#endif
+
+static void set_task_reclaim_state(struct task_struct *task,
+ struct reclaim_state *rs)
+{
+ /* Check for an overwrite */
+ WARN_ON_ONCE(rs && task->reclaim_state);
+
+ /* Check for the nulling of an already-nulled member */
+ WARN_ON_ONCE(!rs && !task->reclaim_state);
+
+ task->reclaim_state = rs;
+}
+
+/*
+ * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
+ * scan_control->nr_reclaimed.
+ */
+static void flush_reclaim_state(struct scan_control *sc)
+{
+ /*
+ * Currently, reclaim_state->reclaimed includes three types of pages
+ * freed outside of vmscan:
+ * (1) Slab pages.
+ * (2) Clean file pages from pruned inodes (on highmem systems).
+ * (3) XFS freed buffer pages.
+ *
+ * For all of these cases, we cannot universally link the pages to a
+ * single memcg. For example, a memcg-aware shrinker can free one object
+ * charged to the target memcg, causing an entire page to be freed.
+ * If we count the entire page as reclaimed from the memcg, we end up
+ * overestimating the reclaimed amount (potentially under-reclaiming).
+ *
+ * Only count such pages for global reclaim to prevent under-reclaiming
+ * from the target memcg; preventing unnecessary retries during memcg
+ * charging and false positives from proactive reclaim.
+ *
+ * For uncommon cases where the freed pages were actually mostly
+ * charged to the target memcg, we end up underestimating the reclaimed
+ * amount. This should be fine. The freed pages will be uncharged
+ * anyway, even if they are not counted here properly, and we will be
+ * able to make forward progress in charging (which is usually in a
+ * retry loop).
+ *
+ * We can go one step further, and report the uncharged objcg pages in
+ * memcg reclaim, to make reporting more accurate and reduce
+ * underestimation, but it's probably not worth the complexity for now.
+ */
+ if (current->reclaim_state && root_reclaim(sc)) {
+ sc->nr_reclaimed += current->reclaim_state->reclaimed;
+ current->reclaim_state->reclaimed = 0;
+ }
+}
+
+static long xchg_nr_deferred(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ int nid = sc->nid;
+
+ if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+ nid = 0;
+
+ if (sc->memcg &&
+ (shrinker->flags & SHRINKER_MEMCG_AWARE))
+ return xchg_nr_deferred_memcg(nid, shrinker,
+ sc->memcg);
+
+ return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+}
+
+
+static long add_nr_deferred(long nr, struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ int nid = sc->nid;
+
+ if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+ nid = 0;
+
+ if (sc->memcg &&
+ (shrinker->flags & SHRINKER_MEMCG_AWARE))
+ return add_nr_deferred_memcg(nr, nid, shrinker,
+ sc->memcg);
+
+ return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
+}
+
+static bool can_demote(int nid, struct scan_control *sc)
+{
+ if (!numa_demotion_enabled)
+ return false;
+ if (sc && sc->no_demotion)
+ return false;
+ if (next_demotion_node(nid) == NUMA_NO_NODE)
+ return false;
+
+ return true;
+}
+
+static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
+ int nid,
+ struct scan_control *sc)
+{
+ if (memcg == NULL) {
+ /*
+ * For non-memcg reclaim, is there
+ * space in any swap device?
+ */
+ if (get_nr_swap_pages() > 0)
+ return true;
+ } else {
+ /* Is the memcg below its swap limit? */
+ if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
+ return true;
+ }
+
+ /*
+ * The page can not be swapped.
+ *
+ * Can it be reclaimed from this node via demotion?
+ */
+ return can_demote(nid, sc);
+}
+
+/*
+ * This misses isolated folios which are not accounted for to save counters.
+ * As the data only determines if reclaim or compaction continues, it is
+ * not expected that isolated folios 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 (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
+ 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 - 1 for the whole LRU list)
+ */
+static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
+ int zone_idx)
+{
+ unsigned long size = 0;
+ int zid;
+
+ for (zid = 0; zid <= zone_idx; zid++) {
+ struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
+
+ if (!managed_zone(zone))
+ continue;
+
+ if (!mem_cgroup_disabled())
+ size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
+ else
+ size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
+ }
+ return size;
+}
+
+/*
+ * Add a shrinker callback to be called from the vm.
+ */
+static int __prealloc_shrinker(struct shrinker *shrinker)
+{
+ unsigned int size;
+ int err;
+
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+ err = prealloc_memcg_shrinker(shrinker);
+ if (err != -ENOSYS)
+ return err;
+
+ shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
+ }
+
+ 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;
+
+ return 0;
+}
+
+#ifdef CONFIG_SHRINKER_DEBUG
+int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
+{
+ va_list ap;
+ int err;
+
+ va_start(ap, fmt);
+ shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
+ va_end(ap);
+ if (!shrinker->name)
+ return -ENOMEM;
+
+ err = __prealloc_shrinker(shrinker);
+ if (err) {
+ kfree_const(shrinker->name);
+ shrinker->name = NULL;
+ }
+
+ return err;
+}
+#else
+int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
+{
+ return __prealloc_shrinker(shrinker);
+}
+#endif
+
+void free_prealloced_shrinker(struct shrinker *shrinker)
+{
+#ifdef CONFIG_SHRINKER_DEBUG
+ kfree_const(shrinker->name);
+ shrinker->name = NULL;
+#endif
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+ down_write(&shrinker_rwsem);
+ unregister_memcg_shrinker(shrinker);
+ up_write(&shrinker_rwsem);
+ return;
+ }
+
+ 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);
+ shrinker->flags |= SHRINKER_REGISTERED;
+ shrinker_debugfs_add(shrinker);
+ up_write(&shrinker_rwsem);
+}
+
+static int __register_shrinker(struct shrinker *shrinker)
+{
+ int err = __prealloc_shrinker(shrinker);
+
+ if (err)
+ return err;
+ register_shrinker_prepared(shrinker);
+ return 0;
+}
+
+#ifdef CONFIG_SHRINKER_DEBUG
+int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
+{
+ va_list ap;
+ int err;
+
+ va_start(ap, fmt);
+ shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
+ va_end(ap);
+ if (!shrinker->name)
+ return -ENOMEM;
+
+ err = __register_shrinker(shrinker);
+ if (err) {
+ kfree_const(shrinker->name);
+ shrinker->name = NULL;
+ }
+ return err;
+}
+#else
+int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
+{
+ return __register_shrinker(shrinker);
+}
+#endif
+EXPORT_SYMBOL(register_shrinker);
+
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+ struct dentry *debugfs_entry;
+ int debugfs_id;
+
+ if (!(shrinker->flags & SHRINKER_REGISTERED))
+ return;
+
+ down_write(&shrinker_rwsem);
+ list_del(&shrinker->list);
+ shrinker->flags &= ~SHRINKER_REGISTERED;
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ unregister_memcg_shrinker(shrinker);
+ debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
+ up_write(&shrinker_rwsem);
+
+ shrinker_debugfs_remove(debugfs_entry, debugfs_id);
+
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+}
+EXPORT_SYMBOL(unregister_shrinker);
+
+/**
+ * synchronize_shrinkers - Wait for all running shrinkers to complete.
+ *
+ * This is equivalent to calling unregister_shrink() and register_shrinker(),
+ * but atomically and with less overhead. This is useful to guarantee that all
+ * shrinker invocations have seen an update, before freeing memory, similar to
+ * rcu.
+ */
+void synchronize_shrinkers(void)
+{
+ down_write(&shrinker_rwsem);
+ up_write(&shrinker_rwsem);
+}
+EXPORT_SYMBOL(synchronize_shrinkers);
+
+#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;
+ long batch_size = shrinker->batch ? shrinker->batch
+ : SHRINK_BATCH;
+ long scanned = 0, next_deferred;
+
+ 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 = xchg_nr_deferred(shrinker, shrinkctl);
+
+ if (shrinker->seeks) {
+ delta = freeable >> priority;
+ delta *= 4;
+ do_div(delta, shrinker->seeks);
+ } else {
+ /*
+ * These objects don't require any IO to create. Trim
+ * them aggressively under memory pressure to keep
+ * them from causing refetches in the IO caches.
+ */
+ delta = freeable / 2;
+ }
+
+ total_scan = nr >> priority;
+ total_scan += delta;
+ total_scan = min(total_scan, (2 * freeable));
+
+ 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();
+ }
+
+ /*
+ * The deferred work is increased by any new work (delta) that wasn't
+ * done, decreased by old deferred work that was done now.
+ *
+ * And it is capped to two times of the freeable items.
+ */
+ next_deferred = max_t(long, (nr + delta - scanned), 0);
+ next_deferred = min(next_deferred, (2 * freeable));
+
+ /*
+ * move the unused scan count back into the shrinker in a
+ * manner that handles concurrent updates.
+ */
+ new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
+
+ trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
+ return freed;
+}
+
+#ifdef CONFIG_MEMCG
+static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg, int priority)
+{
+ struct shrinker_info *info;
+ unsigned long ret, freed = 0;
+ int i;
+
+ if (!mem_cgroup_online(memcg))
+ return 0;
+
+ if (!down_read_trylock(&shrinker_rwsem))
+ return 0;
+
+ info = shrinker_info_protected(memcg, nid);
+ if (unlikely(!info))
+ goto unlock;
+
+ for_each_set_bit(i, info->map, info->map_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->flags & SHRINKER_REGISTERED))) {
+ if (!shrinker)
+ clear_bit(i, info->map);
+ continue;
+ }
+
+ /* Call non-slab shrinkers even though kmem is disabled */
+ if (!memcg_kmem_online() &&
+ !(shrinker->flags & SHRINKER_NONSLAB))
+ continue;
+
+ ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY) {
+ clear_bit(i, info->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
+ * 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
+ 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 */
+static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg, int priority)
+{
+ return 0;
+}
+#endif /* CONFIG_MEMCG */
+
+/**
+ * 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;
+
+ /*
+ * The root memcg might be allocated even though memcg is disabled
+ * via "cgroup_disable=memory" boot parameter. This could make
+ * mem_cgroup_is_root() return false, then just run memcg slab
+ * shrink, but skip global shrink. This may result in premature
+ * oom.
+ */
+ if (!mem_cgroup_disabled() && !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 registration 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;
+}
+
+static unsigned long drop_slab_node(int nid)
+{
+ unsigned long freed = 0;
+ struct mem_cgroup *memcg = NULL;
+
+ 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);
+
+ return freed;
+}
+
+void drop_slab(void)
+{
+ int nid;
+ int shift = 0;
+ unsigned long freed;
+
+ do {
+ freed = 0;
+ for_each_online_node(nid) {
+ if (fatal_signal_pending(current))
+ return;
+
+ freed += drop_slab_node(nid);
+ }
+ } while ((freed >> shift++) > 1);
+}
+
+static int reclaimer_offset(void)
+{
+ BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
+ PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
+ BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
+ PGSCAN_DIRECT - PGSCAN_KSWAPD);
+ BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
+ PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
+ BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
+ PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
+
+ if (current_is_kswapd())
+ return 0;
+ if (current_is_khugepaged())
+ return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
+ return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
+}
+
+static inline int is_page_cache_freeable(struct folio *folio)
+{
+ /*
+ * A freeable page cache folio is referenced only by the caller
+ * that isolated the folio, the page cache and optional filesystem
+ * private data at folio->private.
+ */
+ return folio_ref_count(folio) - folio_test_private(folio) ==
+ 1 + folio_nr_pages(folio);
+}
+
+/*
+ * We detected a synchronous write error writing a folio 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 folio and once
+ * that folio is locked, the mapping is pinned.
+ *
+ * We're allowed to run sleeping folio_lock() here because we know the caller has
+ * __GFP_FS.
+ */
+static void handle_write_error(struct address_space *mapping,
+ struct folio *folio, int error)
+{
+ folio_lock(folio);
+ if (folio_mapping(folio) == mapping)
+ mapping_set_error(mapping, error);
+ folio_unlock(folio);
+}
+
+static bool skip_throttle_noprogress(pg_data_t *pgdat)
+{
+ int reclaimable = 0, write_pending = 0;
+ int i;
+
+ /*
+ * If kswapd is disabled, reschedule if necessary but do not
+ * throttle as the system is likely near OOM.
+ */
+ if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
+ return true;
+
+ /*
+ * If there are a lot of dirty/writeback folios then do not
+ * throttle as throttling will occur when the folios cycle
+ * towards the end of the LRU if still under writeback.
+ */
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!managed_zone(zone))
+ continue;
+
+ reclaimable += zone_reclaimable_pages(zone);
+ write_pending += zone_page_state_snapshot(zone,
+ NR_ZONE_WRITE_PENDING);
+ }
+ if (2 * write_pending <= reclaimable)
+ return true;
+
+ return false;
+}
+
+void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
+{
+ wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
+ long timeout, ret;
+ DEFINE_WAIT(wait);
+
+ /*
+ * Do not throttle user workers, kthreads other than kswapd or
+ * workqueues. They may be required for reclaim to make
+ * forward progress (e.g. journalling workqueues or kthreads).
+ */
+ if (!current_is_kswapd() &&
+ current->flags & (PF_USER_WORKER|PF_KTHREAD)) {
+ cond_resched();
+ return;
+ }
+
+ /*
+ * These figures are pulled out of thin air.
+ * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
+ * parallel reclaimers which is a short-lived event so the timeout is
+ * short. Failing to make progress or waiting on writeback are
+ * potentially long-lived events so use a longer timeout. This is shaky
+ * logic as a failure to make progress could be due to anything from
+ * writeback to a slow device to excessive referenced folios at the tail
+ * of the inactive LRU.
+ */
+ switch(reason) {
+ case VMSCAN_THROTTLE_WRITEBACK:
+ timeout = HZ/10;
+
+ if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
+ WRITE_ONCE(pgdat->nr_reclaim_start,
+ node_page_state(pgdat, NR_THROTTLED_WRITTEN));
+ }
+
+ break;
+ case VMSCAN_THROTTLE_CONGESTED:
+ fallthrough;
+ case VMSCAN_THROTTLE_NOPROGRESS:
+ if (skip_throttle_noprogress(pgdat)) {
+ cond_resched();
+ return;
+ }
+
+ timeout = 1;
+
+ break;
+ case VMSCAN_THROTTLE_ISOLATED:
+ timeout = HZ/50;
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ timeout = HZ;
+ break;
+ }
+
+ prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+ ret = schedule_timeout(timeout);
+ finish_wait(wqh, &wait);
+
+ if (reason == VMSCAN_THROTTLE_WRITEBACK)
+ atomic_dec(&pgdat->nr_writeback_throttled);
+
+ trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
+ jiffies_to_usecs(timeout - ret),
+ reason);
+}
+
+/*
+ * Account for folios written if tasks are throttled waiting on dirty
+ * folios to clean. If enough folios have been cleaned since throttling
+ * started then wakeup the throttled tasks.
+ */
+void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
+ int nr_throttled)
+{
+ unsigned long nr_written;
+
+ node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
+
+ /*
+ * This is an inaccurate read as the per-cpu deltas may not
+ * be synchronised. However, given that the system is
+ * writeback throttled, it is not worth taking the penalty
+ * of getting an accurate count. At worst, the throttle
+ * timeout guarantees forward progress.
+ */
+ nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
+ READ_ONCE(pgdat->nr_reclaim_start);
+
+ if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
+ wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
+}
+
+/* possible outcome of pageout() */
+typedef enum {
+ /* failed to write folio out, folio is locked */
+ PAGE_KEEP,
+ /* move folio to the active list, folio is locked */
+ PAGE_ACTIVATE,
+ /* folio has been sent to the disk successfully, folio is unlocked */
+ PAGE_SUCCESS,
+ /* folio is clean and locked */
+ PAGE_CLEAN,
+} pageout_t;
+
+/*
+ * pageout is called by shrink_folio_list() for each dirty folio.
+ * Calls ->writepage().
+ */
+static pageout_t pageout(struct folio *folio, struct address_space *mapping,
+ struct swap_iocb **plug)
+{
+ /*
+ * If the folio 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 folio's queue, we can perform writeback even if that
+ * will block.
+ *
+ * If the folio 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(folio))
+ return PAGE_KEEP;
+ if (!mapping) {
+ /*
+ * Some data journaling orphaned folios can have
+ * folio->mapping == NULL while being dirty with clean buffers.
+ */
+ if (folio_test_private(folio)) {
+ if (try_to_free_buffers(folio)) {
+ folio_clear_dirty(folio);
+ pr_info("%s: orphaned folio\n", __func__);
+ return PAGE_CLEAN;
+ }
+ }
+ return PAGE_KEEP;
+ }
+ if (mapping->a_ops->writepage == NULL)
+ return PAGE_ACTIVATE;
+
+ if (folio_clear_dirty_for_io(folio)) {
+ 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,
+ .swap_plug = plug,
+ };
+
+ folio_set_reclaim(folio);
+ res = mapping->a_ops->writepage(&folio->page, &wbc);
+ if (res < 0)
+ handle_write_error(mapping, folio, res);
+ if (res == AOP_WRITEPAGE_ACTIVATE) {
+ folio_clear_reclaim(folio);
+ return PAGE_ACTIVATE;
+ }
+
+ if (!folio_test_writeback(folio)) {
+ /* synchronous write or broken a_ops? */
+ folio_clear_reclaim(folio);
+ }
+ trace_mm_vmscan_write_folio(folio);
+ node_stat_add_folio(folio, NR_VMSCAN_WRITE);
+ return PAGE_SUCCESS;
+ }
+
+ return PAGE_CLEAN;
+}
+
+/*
+ * Same as remove_mapping, but if the folio is removed from the mapping, it
+ * gets returned with a refcount of 0.
+ */
+static int __remove_mapping(struct address_space *mapping, struct folio *folio,
+ bool reclaimed, struct mem_cgroup *target_memcg)
+{
+ int refcount;
+ void *shadow = NULL;
+
+ BUG_ON(!folio_test_locked(folio));
+ BUG_ON(mapping != folio_mapping(folio));
+
+ if (!folio_test_swapcache(folio))
+ spin_lock(&mapping->host->i_lock);
+ xa_lock_irq(&mapping->i_pages);
+ /*
+ * The non racy check for a busy folio.
+ *
+ * Must be careful with the order of the tests. When someone has
+ * a ref to the folio, it may be possible that they dirty it then
+ * drop the reference. So if the dirty flag is tested before the
+ * refcount here, then the following race may occur:
+ *
+ * get_user_pages(&page);
+ * [user mapping goes away]
+ * write_to(page);
+ * !folio_test_dirty(folio) [good]
+ * folio_set_dirty(folio);
+ * folio_put(folio);
+ * !refcount(folio) [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 folio->flags
+ * load is not satisfied before that of folio->_refcount.
+ *
+ * Note that if the dirty flag is always set via folio_mark_dirty,
+ * and thus under the i_pages lock, then this ordering is not required.
+ */
+ refcount = 1 + folio_nr_pages(folio);
+ if (!folio_ref_freeze(folio, refcount))
+ goto cannot_free;
+ /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
+ if (unlikely(folio_test_dirty(folio))) {
+ folio_ref_unfreeze(folio, refcount);
+ goto cannot_free;
+ }
+
+ if (folio_test_swapcache(folio)) {
+ swp_entry_t swap = folio->swap;
+
+ if (reclaimed && !mapping_exiting(mapping))
+ shadow = workingset_eviction(folio, target_memcg);
+ __delete_from_swap_cache(folio, swap, shadow);
+ mem_cgroup_swapout(folio, swap);
+ xa_unlock_irq(&mapping->i_pages);
+ put_swap_folio(folio, swap);
+ } else {
+ void (*free_folio)(struct folio *);
+
+ free_folio = mapping->a_ops->free_folio;
+ /*
+ * 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 optimization,
+ * 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 folios 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 && folio_is_file_lru(folio) &&
+ !mapping_exiting(mapping) && !dax_mapping(mapping))
+ shadow = workingset_eviction(folio, target_memcg);
+ __filemap_remove_folio(folio, shadow);
+ xa_unlock_irq(&mapping->i_pages);
+ if (mapping_shrinkable(mapping))
+ inode_add_lru(mapping->host);
+ spin_unlock(&mapping->host->i_lock);
+
+ if (free_folio)
+ free_folio(folio);
+ }
+
+ return 1;
+
+cannot_free:
+ xa_unlock_irq(&mapping->i_pages);
+ if (!folio_test_swapcache(folio))
+ spin_unlock(&mapping->host->i_lock);
+ return 0;
+}
+
+/**
+ * remove_mapping() - Attempt to remove a folio from its mapping.
+ * @mapping: The address space.
+ * @folio: The folio to remove.
+ *
+ * If the folio is dirty, under writeback or if someone else has a ref
+ * on it, removal will fail.
+ * Return: The number of pages removed from the mapping. 0 if the folio
+ * could not be removed.
+ * Context: The caller should have a single refcount on the folio and
+ * hold its lock.
+ */
+long remove_mapping(struct address_space *mapping, struct folio *folio)
+{
+ if (__remove_mapping(mapping, folio, false, NULL)) {
+ /*
+ * Unfreezing the refcount with 1 effectively
+ * drops the pagecache ref for us without requiring another
+ * atomic operation.
+ */
+ folio_ref_unfreeze(folio, 1);
+ return folio_nr_pages(folio);
+ }
+ return 0;
+}
+
+/**
+ * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
+ * @folio: Folio to be returned to an LRU list.
+ *
+ * Add previously isolated @folio to appropriate LRU list.
+ * The folio may still be unevictable for other reasons.
+ *
+ * Context: lru_lock must not be held, interrupts must be enabled.
+ */
+void folio_putback_lru(struct folio *folio)
+{
+ folio_add_lru(folio);
+ folio_put(folio); /* drop ref from isolate */
+}
+
+enum folio_references {
+ FOLIOREF_RECLAIM,
+ FOLIOREF_RECLAIM_CLEAN,
+ FOLIOREF_KEEP,
+ FOLIOREF_ACTIVATE,
+};
+
+static enum folio_references folio_check_references(struct folio *folio,
+ struct scan_control *sc)
+{
+ int referenced_ptes, referenced_folio;
+ unsigned long vm_flags;
+
+ referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
+ &vm_flags);
+ referenced_folio = folio_test_clear_referenced(folio);
+
+ /*
+ * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
+ * Let the folio, now marked Mlocked, be moved to the unevictable list.
+ */
+ if (vm_flags & VM_LOCKED)
+ return FOLIOREF_ACTIVATE;
+
+ /* rmap lock contention: rotate */
+ if (referenced_ptes == -1)
+ return FOLIOREF_KEEP;
+
+ if (referenced_ptes) {
+ /*
+ * All mapped folios start out with page table
+ * references from the instantiating fault, so we need
+ * to look twice if a mapped file/anon folio 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 folios as well
+ * so that recently deactivated but used folios are
+ * quickly recovered.
+ */
+ folio_set_referenced(folio);
+
+ if (referenced_folio || referenced_ptes > 1)
+ return FOLIOREF_ACTIVATE;
+
+ /*
+ * Activate file-backed executable folios after first usage.
+ */
+ if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
+ return FOLIOREF_ACTIVATE;
+
+ return FOLIOREF_KEEP;
+ }
+
+ /* Reclaim if clean, defer dirty folios to writeback */
+ if (referenced_folio && folio_is_file_lru(folio))
+ return FOLIOREF_RECLAIM_CLEAN;
+
+ return FOLIOREF_RECLAIM;
+}
+
+/* Check if a folio is dirty or under writeback */
+static void folio_check_dirty_writeback(struct folio *folio,
+ bool *dirty, bool *writeback)
+{
+ struct address_space *mapping;
+
+ /*
+ * Anonymous folios are not handled by flushers and must be written
+ * from reclaim context. Do not stall reclaim based on them.
+ * MADV_FREE anonymous folios are put into inactive file list too.
+ * They could be mistakenly treated as file lru. So further anon
+ * test is needed.
+ */
+ if (!folio_is_file_lru(folio) ||
+ (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
+ *dirty = false;
+ *writeback = false;
+ return;
+ }
+
+ /* By default assume that the folio flags are accurate */
+ *dirty = folio_test_dirty(folio);
+ *writeback = folio_test_writeback(folio);
+
+ /* Verify dirty/writeback state if the filesystem supports it */
+ if (!folio_test_private(folio))
+ return;
+
+ mapping = folio_mapping(folio);
+ if (mapping && mapping->a_ops->is_dirty_writeback)
+ mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
+}
+
+static struct folio *alloc_demote_folio(struct folio *src,
+ unsigned long private)
+{
+ struct folio *dst;
+ nodemask_t *allowed_mask;
+ struct migration_target_control *mtc;
+
+ mtc = (struct migration_target_control *)private;
+
+ allowed_mask = mtc->nmask;
+ /*
+ * make sure we allocate from the target node first also trying to
+ * demote or reclaim pages from the target node via kswapd if we are
+ * low on free memory on target node. If we don't do this and if
+ * we have free memory on the slower(lower) memtier, we would start
+ * allocating pages from slower(lower) memory tiers without even forcing
+ * a demotion of cold pages from the target memtier. This can result
+ * in the kernel placing hot pages in slower(lower) memory tiers.
+ */
+ mtc->nmask = NULL;
+ mtc->gfp_mask |= __GFP_THISNODE;
+ dst = alloc_migration_target(src, (unsigned long)mtc);
+ if (dst)
+ return dst;
+
+ mtc->gfp_mask &= ~__GFP_THISNODE;
+ mtc->nmask = allowed_mask;
+
+ return alloc_migration_target(src, (unsigned long)mtc);
+}
+
+/*
+ * Take folios on @demote_folios and attempt to demote them to another node.
+ * Folios which are not demoted are left on @demote_folios.
+ */
+static unsigned int demote_folio_list(struct list_head *demote_folios,
+ struct pglist_data *pgdat)
+{
+ int target_nid = next_demotion_node(pgdat->node_id);
+ unsigned int nr_succeeded;
+ nodemask_t allowed_mask;
+
+ struct migration_target_control mtc = {
+ /*
+ * Allocate from 'node', or fail quickly and quietly.
+ * When this happens, 'page' will likely just be discarded
+ * instead of migrated.
+ */
+ .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
+ __GFP_NOMEMALLOC | GFP_NOWAIT,
+ .nid = target_nid,
+ .nmask = &allowed_mask
+ };
+
+ if (list_empty(demote_folios))
+ return 0;
+
+ if (target_nid == NUMA_NO_NODE)
+ return 0;
+
+ node_get_allowed_targets(pgdat, &allowed_mask);
+
+ /* Demotion ignores all cpuset and mempolicy settings */
+ migrate_pages(demote_folios, alloc_demote_folio, NULL,
+ (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
+ &nr_succeeded);
+
+ __count_vm_events(PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded);
+
+ return nr_succeeded;
+}
+
+static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
+{
+ if (gfp_mask & __GFP_FS)
+ return true;
+ if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
+ return false;
+ /*
+ * We can "enter_fs" for swap-cache with only __GFP_IO
+ * providing this isn't SWP_FS_OPS.
+ * ->flags can be updated non-atomicially (scan_swap_map_slots),
+ * but that will never affect SWP_FS_OPS, so the data_race
+ * is safe.
+ */
+ return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
+}
+
+/*
+ * shrink_folio_list() returns the number of reclaimed pages
+ */
+static unsigned int shrink_folio_list(struct list_head *folio_list,
+ struct pglist_data *pgdat, struct scan_control *sc,
+ struct reclaim_stat *stat, bool ignore_references)
+{
+ LIST_HEAD(ret_folios);
+ LIST_HEAD(free_folios);
+ LIST_HEAD(demote_folios);
+ unsigned int nr_reclaimed = 0;
+ unsigned int pgactivate = 0;
+ bool do_demote_pass;
+ struct swap_iocb *plug = NULL;
+
+ memset(stat, 0, sizeof(*stat));
+ cond_resched();
+ do_demote_pass = can_demote(pgdat->node_id, sc);
+
+retry:
+ while (!list_empty(folio_list)) {
+ struct address_space *mapping;
+ struct folio *folio;
+ enum folio_references references = FOLIOREF_RECLAIM;
+ bool dirty, writeback;
+ unsigned int nr_pages;
+
+ cond_resched();
+
+ folio = lru_to_folio(folio_list);
+ list_del(&folio->lru);
+
+ if (!folio_trylock(folio))
+ goto keep;
+
+ VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
+
+ nr_pages = folio_nr_pages(folio);
+
+ /* Account the number of base pages */
+ sc->nr_scanned += nr_pages;
+
+ if (unlikely(!folio_evictable(folio)))
+ goto activate_locked;
+
+ if (!sc->may_unmap && folio_mapped(folio))
+ goto keep_locked;
+
+ /* folio_update_gen() tried to promote this page? */
+ if (lru_gen_enabled() && !ignore_references &&
+ folio_mapped(folio) && folio_test_referenced(folio))
+ goto keep_locked;
+
+ /*
+ * The number of dirty pages determines if a node is marked
+ * reclaim_congested. kswapd will stall and start writing
+ * folios if the tail of the LRU is all dirty unqueued folios.
+ */
+ folio_check_dirty_writeback(folio, &dirty, &writeback);
+ if (dirty || writeback)
+ stat->nr_dirty += nr_pages;
+
+ if (dirty && !writeback)
+ stat->nr_unqueued_dirty += nr_pages;
+
+ /*
+ * Treat this folio as congested if folios are cycling
+ * through the LRU so quickly that the folios marked
+ * for immediate reclaim are making it to the end of
+ * the LRU a second time.
+ */
+ if (writeback && folio_test_reclaim(folio))
+ stat->nr_congested += nr_pages;
+
+ /*
+ * If a folio at the tail of the LRU is under writeback, there
+ * are three cases to consider.
+ *
+ * 1) If reclaim is encountering an excessive number
+ * of folios under writeback and this folio has both
+ * the writeback and reclaim flags set, then it
+ * indicates that folios are being queued for I/O but
+ * are being recycled through the LRU before the I/O
+ * can complete. Waiting on the folio itself risks an
+ * indefinite stall if it is impossible to writeback
+ * the folio due to I/O error or disconnected storage
+ * so instead note that the LRU is being scanned too
+ * quickly and the caller can stall after the folio
+ * list has been processed.
+ *
+ * 2) Global or new memcg reclaim encounters a folio 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 folio for immediate
+ * reclaim and continue scanning.
+ *
+ * Require may_enter_fs() because we would wait on fs, which
+ * may not have submitted I/O yet. And the loop driver might
+ * enter reclaim, and deadlock if it waits on a folio 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 folio that already has the
+ * reclaim flag set. memcg does not have any dirty folio
+ * throttling so we could easily OOM just because too many
+ * folios are in writeback and there is nothing else to
+ * reclaim. Wait for the writeback to complete.
+ *
+ * In cases 1) and 2) we activate the folios to get them out of
+ * the way while we continue scanning for clean folios 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 (folio_test_writeback(folio)) {
+ /* Case 1 above */
+ if (current_is_kswapd() &&
+ folio_test_reclaim(folio) &&
+ test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
+ stat->nr_immediate += nr_pages;
+ goto activate_locked;
+
+ /* Case 2 above */
+ } else if (writeback_throttling_sane(sc) ||
+ !folio_test_reclaim(folio) ||
+ !may_enter_fs(folio, sc->gfp_mask)) {
+ /*
+ * This is slightly racy -
+ * folio_end_writeback() might have
+ * just cleared the reclaim flag, then
+ * setting the reclaim flag here ends up
+ * interpreted as the readahead flag - but
+ * that does not matter enough to care.
+ * What we do want is for this folio to
+ * have the reclaim flag set next time
+ * memcg reclaim reaches the tests above,
+ * so it will then wait for writeback to
+ * avoid OOM; and it's also appropriate
+ * in global reclaim.
+ */
+ folio_set_reclaim(folio);
+ stat->nr_writeback += nr_pages;
+ goto activate_locked;
+
+ /* Case 3 above */
+ } else {
+ folio_unlock(folio);
+ folio_wait_writeback(folio);
+ /* then go back and try same folio again */
+ list_add_tail(&folio->lru, folio_list);
+ continue;
+ }
+ }
+
+ if (!ignore_references)
+ references = folio_check_references(folio, sc);
+
+ switch (references) {
+ case FOLIOREF_ACTIVATE:
+ goto activate_locked;
+ case FOLIOREF_KEEP:
+ stat->nr_ref_keep += nr_pages;
+ goto keep_locked;
+ case FOLIOREF_RECLAIM:
+ case FOLIOREF_RECLAIM_CLEAN:
+ ; /* try to reclaim the folio below */
+ }
+
+ /*
+ * Before reclaiming the folio, try to relocate
+ * its contents to another node.
+ */
+ if (do_demote_pass &&
+ (thp_migration_supported() || !folio_test_large(folio))) {
+ list_add(&folio->lru, &demote_folios);
+ folio_unlock(folio);
+ continue;
+ }
+
+ /*
+ * Anonymous process memory has backing store?
+ * Try to allocate it some swap space here.
+ * Lazyfree folio could be freed directly
+ */
+ if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
+ if (!folio_test_swapcache(folio)) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (folio_maybe_dma_pinned(folio))
+ goto keep_locked;
+ if (folio_test_large(folio)) {
+ /* cannot split folio, skip it */
+ if (!can_split_folio(folio, NULL))
+ goto activate_locked;
+ /*
+ * Split folios without a PMD map right
+ * away. Chances are some or all of the
+ * tail pages can be freed without IO.
+ */
+ if (!folio_entire_mapcount(folio) &&
+ split_folio_to_list(folio,
+ folio_list))
+ goto activate_locked;
+ }
+ if (!add_to_swap(folio)) {
+ if (!folio_test_large(folio))
+ goto activate_locked_split;
+ /* Fallback to swap normal pages */
+ if (split_folio_to_list(folio,
+ folio_list))
+ goto activate_locked;
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_vm_event(THP_SWPOUT_FALLBACK);
+#endif
+ if (!add_to_swap(folio))
+ goto activate_locked_split;
+ }
+ }
+ } else if (folio_test_swapbacked(folio) &&
+ folio_test_large(folio)) {
+ /* Split shmem folio */
+ if (split_folio_to_list(folio, folio_list))
+ goto keep_locked;
+ }
+
+ /*
+ * If the folio was split above, the tail pages will make
+ * their own pass through this function and be accounted
+ * then.
+ */
+ if ((nr_pages > 1) && !folio_test_large(folio)) {
+ sc->nr_scanned -= (nr_pages - 1);
+ nr_pages = 1;
+ }
+
+ /*
+ * The folio is mapped into the page tables of one or more
+ * processes. Try to unmap it here.
+ */
+ if (folio_mapped(folio)) {
+ enum ttu_flags flags = TTU_BATCH_FLUSH;
+ bool was_swapbacked = folio_test_swapbacked(folio);
+
+ if (folio_test_pmd_mappable(folio))
+ flags |= TTU_SPLIT_HUGE_PMD;
+
+ try_to_unmap(folio, flags);
+ if (folio_mapped(folio)) {
+ stat->nr_unmap_fail += nr_pages;
+ if (!was_swapbacked &&
+ folio_test_swapbacked(folio))
+ stat->nr_lazyfree_fail += nr_pages;
+ goto activate_locked;
+ }
+ }
+
+ /*
+ * Folio is unmapped now so it cannot be newly pinned anymore.
+ * No point in trying to reclaim folio if it is pinned.
+ * Furthermore we don't want to reclaim underlying fs metadata
+ * if the folio is pinned and thus potentially modified by the
+ * pinning process as that may upset the filesystem.
+ */
+ if (folio_maybe_dma_pinned(folio))
+ goto activate_locked;
+
+ mapping = folio_mapping(folio);
+ if (folio_test_dirty(folio)) {
+ /*
+ * Only kswapd can writeback filesystem folios
+ * to avoid risk of stack overflow. But avoid
+ * injecting inefficient single-folio I/O into
+ * flusher writeback as much as possible: only
+ * write folios when we've encountered many
+ * dirty folios, and when we've already scanned
+ * the rest of the LRU for clean folios and see
+ * the same dirty folios again (with the reclaim
+ * flag set).
+ */
+ if (folio_is_file_lru(folio) &&
+ (!current_is_kswapd() ||
+ !folio_test_reclaim(folio) ||
+ !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
+ /*
+ * Immediately reclaim when written back.
+ * Similar in principle to folio_deactivate()
+ * except we already have the folio isolated
+ * and know it's dirty
+ */
+ node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
+ nr_pages);
+ folio_set_reclaim(folio);
+
+ goto activate_locked;
+ }
+
+ if (references == FOLIOREF_RECLAIM_CLEAN)
+ goto keep_locked;
+ if (!may_enter_fs(folio, sc->gfp_mask))
+ goto keep_locked;
+ if (!sc->may_writepage)
+ goto keep_locked;
+
+ /*
+ * Folio is dirty. Flush the TLB if a writable entry
+ * potentially exists to avoid CPU writes after I/O
+ * starts and then write it out here.
+ */
+ try_to_unmap_flush_dirty();
+ switch (pageout(folio, mapping, &plug)) {
+ case PAGE_KEEP:
+ goto keep_locked;
+ case PAGE_ACTIVATE:
+ goto activate_locked;
+ case PAGE_SUCCESS:
+ stat->nr_pageout += nr_pages;
+
+ if (folio_test_writeback(folio))
+ goto keep;
+ if (folio_test_dirty(folio))
+ goto keep;
+
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the folio.
+ */
+ if (!folio_trylock(folio))
+ goto keep;
+ if (folio_test_dirty(folio) ||
+ folio_test_writeback(folio))
+ goto keep_locked;
+ mapping = folio_mapping(folio);
+ fallthrough;
+ case PAGE_CLEAN:
+ ; /* try to free the folio below */
+ }
+ }
+
+ /*
+ * If the folio has buffers, try to free the buffer
+ * mappings associated with this folio. If we succeed
+ * we try to free the folio as well.
+ *
+ * We do this even if the folio is dirty.
+ * filemap_release_folio() does not perform I/O, but it
+ * is possible for a folio to have the dirty flag 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. filemap_release_folio() will
+ * discover that cleanness and will drop the buffers
+ * and mark the folio clean - it can be freed.
+ *
+ * Rarely, folios can have buffers and no ->mapping.
+ * These are the folios which were not successfully
+ * invalidated in truncate_cleanup_folio(). We try to
+ * drop those buffers here and if that worked, and the
+ * folio is no longer mapped into process address space
+ * (refcount == 1) it can be freed. Otherwise, leave
+ * the folio on the LRU so it is swappable.
+ */
+ if (folio_needs_release(folio)) {
+ if (!filemap_release_folio(folio, sc->gfp_mask))
+ goto activate_locked;
+ if (!mapping && folio_ref_count(folio) == 1) {
+ folio_unlock(folio);
+ if (folio_put_testzero(folio))
+ goto free_it;
+ else {
+ /*
+ * rare race with speculative reference.
+ * the speculative reference will free
+ * this folio shortly, so we may
+ * increment nr_reclaimed here (and
+ * leave it off the LRU).
+ */
+ nr_reclaimed += nr_pages;
+ continue;
+ }
+ }
+ }
+
+ if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
+ /* follow __remove_mapping for reference */
+ if (!folio_ref_freeze(folio, 1))
+ goto keep_locked;
+ /*
+ * The folio has only one reference left, which is
+ * from the isolation. After the caller puts the
+ * folio back on the lru and drops the reference, the
+ * folio will be freed anyway. It doesn't matter
+ * which lru it goes on. So we don't bother checking
+ * the dirty flag here.
+ */
+ count_vm_events(PGLAZYFREED, nr_pages);
+ count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
+ } else if (!mapping || !__remove_mapping(mapping, folio, true,
+ sc->target_mem_cgroup))
+ goto keep_locked;
+
+ folio_unlock(folio);
+free_it:
+ /*
+ * Folio may get swapped out as a whole, need to account
+ * all pages in it.
+ */
+ nr_reclaimed += nr_pages;
+
+ /*
+ * Is there need to periodically free_folio_list? It would
+ * appear not as the counts should be low
+ */
+ if (unlikely(folio_test_large(folio)))
+ destroy_large_folio(folio);
+ else
+ list_add(&folio->lru, &free_folios);
+ continue;
+
+activate_locked_split:
+ /*
+ * The tail pages that are failed to add into swap cache
+ * reach here. Fixup nr_scanned and nr_pages.
+ */
+ if (nr_pages > 1) {
+ sc->nr_scanned -= (nr_pages - 1);
+ nr_pages = 1;
+ }
+activate_locked:
+ /* Not a candidate for swapping, so reclaim swap space. */
+ if (folio_test_swapcache(folio) &&
+ (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
+ folio_free_swap(folio);
+ VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
+ if (!folio_test_mlocked(folio)) {
+ int type = folio_is_file_lru(folio);
+ folio_set_active(folio);
+ stat->nr_activate[type] += nr_pages;
+ count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
+ }
+keep_locked:
+ folio_unlock(folio);
+keep:
+ list_add(&folio->lru, &ret_folios);
+ VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
+ folio_test_unevictable(folio), folio);
+ }
+ /* 'folio_list' is always empty here */
+
+ /* Migrate folios selected for demotion */
+ nr_reclaimed += demote_folio_list(&demote_folios, pgdat);
+ /* Folios that could not be demoted are still in @demote_folios */
+ if (!list_empty(&demote_folios)) {
+ /* Folios which weren't demoted go back on @folio_list */
+ list_splice_init(&demote_folios, folio_list);
+
+ /*
+ * goto retry to reclaim the undemoted folios in folio_list if
+ * desired.
+ *
+ * Reclaiming directly from top tier nodes is not often desired
+ * due to it breaking the LRU ordering: in general memory
+ * should be reclaimed from lower tier nodes and demoted from
+ * top tier nodes.
+ *
+ * However, disabling reclaim from top tier nodes entirely
+ * would cause ooms in edge scenarios where lower tier memory
+ * is unreclaimable for whatever reason, eg memory being
+ * mlocked or too hot to reclaim. We can disable reclaim
+ * from top tier nodes in proactive reclaim though as that is
+ * not real memory pressure.
+ */
+ if (!sc->proactive) {
+ do_demote_pass = false;
+ goto retry;
+ }
+ }
+
+ pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
+
+ mem_cgroup_uncharge_list(&free_folios);
+ try_to_unmap_flush();
+ free_unref_page_list(&free_folios);
+
+ list_splice(&ret_folios, folio_list);
+ count_vm_events(PGACTIVATE, pgactivate);
+
+ if (plug)
+ swap_write_unplug(plug);
+ return nr_reclaimed;
+}
+
+unsigned int reclaim_clean_pages_from_list(struct zone *zone,
+ struct list_head *folio_list)
+{
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .may_unmap = 1,
+ };
+ struct reclaim_stat stat;
+ unsigned int nr_reclaimed;
+ struct folio *folio, *next;
+ LIST_HEAD(clean_folios);
+ unsigned int noreclaim_flag;
+
+ list_for_each_entry_safe(folio, next, folio_list, lru) {
+ if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
+ !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
+ !folio_test_unevictable(folio)) {
+ folio_clear_active(folio);
+ list_move(&folio->lru, &clean_folios);
+ }
+ }
+
+ /*
+ * We should be safe here since we are only dealing with file pages and
+ * we are not kswapd and therefore cannot write dirty file pages. But
+ * call memalloc_noreclaim_save() anyway, just in case these conditions
+ * change in the future.
+ */
+ noreclaim_flag = memalloc_noreclaim_save();
+ nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
+ &stat, true);
+ memalloc_noreclaim_restore(noreclaim_flag);
+
+ list_splice(&clean_folios, folio_list);
+ mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
+ -(long)nr_reclaimed);
+ /*
+ * Since lazyfree pages are isolated from file LRU from the beginning,
+ * they will rotate back to anonymous LRU in the end if it failed to
+ * discard so isolated count will be mismatched.
+ * Compensate the isolated count for both LRU lists.
+ */
+ mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
+ stat.nr_lazyfree_fail);
+ mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
+ -(long)stat.nr_lazyfree_fail);
+ return nr_reclaimed;
+}
+
+/*
+ * Update LRU sizes after isolating pages. The LRU size updates must
+ * be complete before mem_cgroup_update_lru_size due to a sanity 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_CMA
+/*
+ * It is waste of effort to scan and reclaim CMA pages if it is not available
+ * for current allocation context. Kswapd can not be enrolled as it can not
+ * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL
+ */
+static bool skip_cma(struct folio *folio, struct scan_control *sc)
+{
+ return !current_is_kswapd() &&
+ gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE &&
+ get_pageblock_migratetype(&folio->page) == MIGRATE_CMA;
+}
+#else
+static bool skip_cma(struct folio *folio, struct scan_control *sc)
+{
+ return false;
+}
+#endif
+
+/*
+ * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
+ *
+ * lruvec->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).
+ *
+ * Lru_lock 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
+ * @lru: LRU list id for isolating
+ *
+ * returns how many pages were moved onto *@dst.
+ */
+static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct list_head *dst,
+ unsigned long *nr_scanned, struct scan_control *sc,
+ 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(folios_skipped);
+
+ total_scan = 0;
+ scan = 0;
+ while (scan < nr_to_scan && !list_empty(src)) {
+ struct list_head *move_to = src;
+ struct folio *folio;
+
+ folio = lru_to_folio(src);
+ prefetchw_prev_lru_folio(folio, src, flags);
+
+ nr_pages = folio_nr_pages(folio);
+ total_scan += nr_pages;
+
+ if (folio_zonenum(folio) > sc->reclaim_idx ||
+ skip_cma(folio, sc)) {
+ nr_skipped[folio_zonenum(folio)] += nr_pages;
+ move_to = &folios_skipped;
+ goto move;
+ }
+
+ /*
+ * Do not count skipped folios because that makes the function
+ * return with no isolated folios if the LRU mostly contains
+ * ineligible folios. This causes the VM to not reclaim any
+ * folios, triggering a premature OOM.
+ * Account all pages in a folio.
+ */
+ scan += nr_pages;
+
+ if (!folio_test_lru(folio))
+ goto move;
+ if (!sc->may_unmap && folio_mapped(folio))
+ goto move;
+
+ /*
+ * Be careful not to clear the lru flag until after we're
+ * sure the folio is not being freed elsewhere -- the
+ * folio release code relies on it.
+ */
+ if (unlikely(!folio_try_get(folio)))
+ goto move;
+
+ if (!folio_test_clear_lru(folio)) {
+ /* Another thread is already isolating this folio */
+ folio_put(folio);
+ goto move;
+ }
+
+ nr_taken += nr_pages;
+ nr_zone_taken[folio_zonenum(folio)] += nr_pages;
+ move_to = dst;
+move:
+ list_move(&folio->lru, move_to);
+ }
+
+ /*
+ * Splice any skipped folios 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 folios to skip and waste lots
+ * of cpu cycles.
+ */
+ if (!list_empty(&folios_skipped)) {
+ int zid;
+
+ list_splice(&folios_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,
+ sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru);
+ update_lru_sizes(lruvec, lru, nr_zone_taken);
+ return nr_taken;
+}
+
+/**
+ * folio_isolate_lru() - Try to isolate a folio from its LRU list.
+ * @folio: Folio to isolate from its LRU list.
+ *
+ * Isolate a @folio from an LRU list and adjust the vmstat statistic
+ * corresponding to whatever LRU list the folio was on.
+ *
+ * The folio will have its LRU flag cleared. If it was found on the
+ * active list, it will have the Active flag set. If it was found on the
+ * unevictable list, it will have the Unevictable flag set. These flags
+ * may need to be cleared by the caller before letting the page go.
+ *
+ * Context:
+ *
+ * (1) Must be called with an elevated refcount on the folio. This is a
+ * fundamental difference from isolate_lru_folios() (which is called
+ * without a stable reference).
+ * (2) The lru_lock must not be held.
+ * (3) Interrupts must be enabled.
+ *
+ * Return: true if the folio was removed from an LRU list.
+ * false if the folio was not on an LRU list.
+ */
+bool folio_isolate_lru(struct folio *folio)
+{
+ bool ret = false;
+
+ VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
+
+ if (folio_test_clear_lru(folio)) {
+ struct lruvec *lruvec;
+
+ folio_get(folio);
+ lruvec = folio_lruvec_lock_irq(folio);
+ lruvec_del_folio(lruvec, folio);
+ unlock_page_lruvec_irq(lruvec);
+ ret = true;
+ }
+
+ return ret;
+}
+
+/*
+ * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
+ * then get rescheduled. 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;
+ bool too_many;
+
+ if (current_is_kswapd())
+ return 0;
+
+ if (!writeback_throttling_sane(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 (gfp_has_io_fs(sc->gfp_mask))
+ inactive >>= 3;
+
+ too_many = isolated > inactive;
+
+ /* Wake up tasks throttled due to too_many_isolated. */
+ if (!too_many)
+ wake_throttle_isolated(pgdat);
+
+ return too_many;
+}
+
+/*
+ * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
+ * On return, @list is reused as a list of folios to be freed by the caller.
+ *
+ * Returns the number of pages moved to the given lruvec.
+ */
+static unsigned int move_folios_to_lru(struct lruvec *lruvec,
+ struct list_head *list)
+{
+ int nr_pages, nr_moved = 0;
+ LIST_HEAD(folios_to_free);
+
+ while (!list_empty(list)) {
+ struct folio *folio = lru_to_folio(list);
+
+ VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
+ list_del(&folio->lru);
+ if (unlikely(!folio_evictable(folio))) {
+ spin_unlock_irq(&lruvec->lru_lock);
+ folio_putback_lru(folio);
+ spin_lock_irq(&lruvec->lru_lock);
+ continue;
+ }
+
+ /*
+ * The folio_set_lru needs to be kept here for list integrity.
+ * Otherwise:
+ * #0 move_folios_to_lru #1 release_pages
+ * if (!folio_put_testzero())
+ * if (folio_put_testzero())
+ * !lru //skip lru_lock
+ * folio_set_lru()
+ * list_add(&folio->lru,)
+ * list_add(&folio->lru,)
+ */
+ folio_set_lru(folio);
+
+ if (unlikely(folio_put_testzero(folio))) {
+ __folio_clear_lru_flags(folio);
+
+ if (unlikely(folio_test_large(folio))) {
+ spin_unlock_irq(&lruvec->lru_lock);
+ destroy_large_folio(folio);
+ spin_lock_irq(&lruvec->lru_lock);
+ } else
+ list_add(&folio->lru, &folios_to_free);
+
+ continue;
+ }
+
+ /*
+ * All pages were isolated from the same lruvec (and isolation
+ * inhibits memcg migration).
+ */
+ VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
+ lruvec_add_folio(lruvec, folio);
+ nr_pages = folio_nr_pages(folio);
+ nr_moved += nr_pages;
+ if (folio_test_active(folio))
+ workingset_age_nonresident(lruvec, nr_pages);
+ }
+
+ /*
+ * To save our caller's stack, now use input list for pages to free.
+ */
+ list_splice(&folios_to_free, list);
+
+ return nr_moved;
+}
+
+/*
+ * If a kernel thread (such as nfsd for loop-back mounts) services a backing
+ * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
+ * we should not throttle. Otherwise it is safe to do so.
+ */
+static int current_may_throttle(void)
+{
+ return !(current->flags & PF_LOCAL_THROTTLE);
+}
+
+/*
+ * shrink_inactive_list() is a helper for shrink_node(). It returns the number
+ * of reclaimed pages
+ */
+static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct scan_control *sc,
+ enum lru_list lru)
+{
+ LIST_HEAD(folio_list);
+ unsigned long nr_scanned;
+ unsigned int nr_reclaimed = 0;
+ unsigned long nr_taken;
+ struct reclaim_stat stat;
+ bool file = is_file_lru(lru);
+ enum vm_event_item item;
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ bool stalled = false;
+
+ while (unlikely(too_many_isolated(pgdat, file, sc))) {
+ if (stalled)
+ return 0;
+
+ /* wait a bit for the reclaimer. */
+ stalled = true;
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
+
+ /* We are about to die and free our memory. Return now. */
+ if (fatal_signal_pending(current))
+ return SWAP_CLUSTER_MAX;
+ }
+
+ lru_add_drain();
+
+ spin_lock_irq(&lruvec->lru_lock);
+
+ nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
+ &nr_scanned, sc, lru);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
+ item = PGSCAN_KSWAPD + reclaimer_offset();
+ if (!cgroup_reclaim(sc))
+ __count_vm_events(item, nr_scanned);
+ __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
+ __count_vm_events(PGSCAN_ANON + file, nr_scanned);
+
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ if (nr_taken == 0)
+ return 0;
+
+ nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
+
+ spin_lock_irq(&lruvec->lru_lock);
+ move_folios_to_lru(lruvec, &folio_list);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+ item = PGSTEAL_KSWAPD + reclaimer_offset();
+ if (!cgroup_reclaim(sc))
+ __count_vm_events(item, nr_reclaimed);
+ __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
+ __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
+ mem_cgroup_uncharge_list(&folio_list);
+ free_unref_page_list(&folio_list);
+
+ /*
+ * If dirty folios 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 folios 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 folios 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);
+ /*
+ * For cgroupv1 dirty throttling is achieved by waking up
+ * the kernel flusher here and later waiting on folios
+ * which are in writeback to finish (see shrink_folio_list()).
+ *
+ * Flusher may not be able to issue writeback quickly
+ * enough for cgroupv1 writeback throttling to work
+ * on a large system.
+ */
+ if (!writeback_throttling_sane(sc))
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
+ }
+
+ 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;
+}
+
+/*
+ * shrink_active_list() moves folios from the active LRU to the inactive LRU.
+ *
+ * We move them the other way if the folio is referenced by one or more
+ * processes.
+ *
+ * If the folios are mostly unmapped, the processing is fast and it is
+ * appropriate to hold lru_lock across the whole operation. But if
+ * the folios are mapped, the processing is slow (folio_referenced()), so
+ * we should drop lru_lock around each folio. It's impossible to balance
+ * this, so instead we remove the folios from the LRU while processing them.
+ * It is safe to rely on the active flag against the non-LRU folios in here
+ * because nobody will play with that bit on a non-LRU folio.
+ *
+ * The downside is that we have to touch folio->_refcount against each folio.
+ * But we had to alter folio->flags anyway.
+ */
+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 folios which were snipped off */
+ LIST_HEAD(l_active);
+ LIST_HEAD(l_inactive);
+ unsigned nr_deactivate, nr_activate;
+ unsigned nr_rotated = 0;
+ int file = is_file_lru(lru);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ lru_add_drain();
+
+ spin_lock_irq(&lruvec->lru_lock);
+
+ nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
+ &nr_scanned, sc, lru);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
+
+ if (!cgroup_reclaim(sc))
+ __count_vm_events(PGREFILL, nr_scanned);
+ __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
+
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ while (!list_empty(&l_hold)) {
+ struct folio *folio;
+
+ cond_resched();
+ folio = lru_to_folio(&l_hold);
+ list_del(&folio->lru);
+
+ if (unlikely(!folio_evictable(folio))) {
+ folio_putback_lru(folio);
+ continue;
+ }
+
+ if (unlikely(buffer_heads_over_limit)) {
+ if (folio_needs_release(folio) &&
+ folio_trylock(folio)) {
+ filemap_release_folio(folio, 0);
+ folio_unlock(folio);
+ }
+ }
+
+ /* Referenced or rmap lock contention: rotate */
+ if (folio_referenced(folio, 0, sc->target_mem_cgroup,
+ &vm_flags) != 0) {
+ /*
+ * Identify referenced, file-backed active folios 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 folios
+ * are not likely to be evicted by use-once streaming
+ * IO, plus JVM can create lots of anon VM_EXEC folios,
+ * so we ignore them here.
+ */
+ if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
+ nr_rotated += folio_nr_pages(folio);
+ list_add(&folio->lru, &l_active);
+ continue;
+ }
+ }
+
+ folio_clear_active(folio); /* we are de-activating */
+ folio_set_workingset(folio);
+ list_add(&folio->lru, &l_inactive);
+ }
+
+ /*
+ * Move folios back to the lru list.
+ */
+ spin_lock_irq(&lruvec->lru_lock);
+
+ nr_activate = move_folios_to_lru(lruvec, &l_active);
+ nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
+ /* Keep all free folios in l_active list */
+ list_splice(&l_inactive, &l_active);
+
+ __count_vm_events(PGDEACTIVATE, nr_deactivate);
+ __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
+
+ __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ if (nr_rotated)
+ lru_note_cost(lruvec, file, 0, nr_rotated);
+ mem_cgroup_uncharge_list(&l_active);
+ free_unref_page_list(&l_active);
+ trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
+ nr_deactivate, nr_rotated, sc->priority, file);
+}
+
+static unsigned int reclaim_folio_list(struct list_head *folio_list,
+ struct pglist_data *pgdat)
+{
+ struct reclaim_stat dummy_stat;
+ unsigned int nr_reclaimed;
+ struct folio *folio;
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .may_writepage = 1,
+ .may_unmap = 1,
+ .may_swap = 1,
+ .no_demotion = 1,
+ };
+
+ nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
+ while (!list_empty(folio_list)) {
+ folio = lru_to_folio(folio_list);
+ list_del(&folio->lru);
+ folio_putback_lru(folio);
+ }
+
+ return nr_reclaimed;
+}
+
+unsigned long reclaim_pages(struct list_head *folio_list)
+{
+ int nid;
+ unsigned int nr_reclaimed = 0;
+ LIST_HEAD(node_folio_list);
+ unsigned int noreclaim_flag;
+
+ if (list_empty(folio_list))
+ return nr_reclaimed;
+
+ noreclaim_flag = memalloc_noreclaim_save();
+
+ nid = folio_nid(lru_to_folio(folio_list));
+ do {
+ struct folio *folio = lru_to_folio(folio_list);
+
+ if (nid == folio_nid(folio)) {
+ folio_clear_active(folio);
+ list_move(&folio->lru, &node_folio_list);
+ continue;
+ }
+
+ nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
+ nid = folio_nid(lru_to_folio(folio_list));
+ } while (!list_empty(folio_list));
+
+ nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
+
+ memalloc_noreclaim_restore(noreclaim_flag);
+
+ return nr_reclaimed;
+}
+
+static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct scan_control *sc)
+{
+ if (is_active_lru(lru)) {
+ if (sc->may_deactivate & (1 << is_file_lru(lru)))
+ shrink_active_list(nr_to_scan, lruvec, sc, lru);
+ else
+ sc->skipped_deactivate = 1;
+ return 0;
+ }
+
+ return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
+}
+
+/*
+ * 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
+ * folio 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 folios
+ * on this LRU, maintained by the pageout code. An inactive_ratio
+ * of 3 means 3:1 or 25% of the folios 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_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
+{
+ enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
+ unsigned long inactive, active;
+ unsigned long inactive_ratio;
+ unsigned long gb;
+
+ inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
+ active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
+
+ gb = (inactive + active) >> (30 - PAGE_SHIFT);
+ if (gb)
+ inactive_ratio = int_sqrt(10 * gb);
+ else
+ inactive_ratio = 1;
+
+ return inactive * inactive_ratio < active;
+}
+
+enum scan_balance {
+ SCAN_EQUAL,
+ SCAN_FRACT,
+ SCAN_ANON,
+ SCAN_FILE,
+};
+
+static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
+{
+ unsigned long file;
+ struct lruvec *target_lruvec;
+
+ if (lru_gen_enabled())
+ return;
+
+ target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
+
+ /*
+ * Flush the memory cgroup stats, so that we read accurate per-memcg
+ * lruvec stats for heuristics.
+ */
+ mem_cgroup_flush_stats();
+
+ /*
+ * Determine the scan balance between anon and file LRUs.
+ */
+ spin_lock_irq(&target_lruvec->lru_lock);
+ sc->anon_cost = target_lruvec->anon_cost;
+ sc->file_cost = target_lruvec->file_cost;
+ spin_unlock_irq(&target_lruvec->lru_lock);
+
+ /*
+ * Target desirable inactive:active list ratios for the anon
+ * and file LRU lists.
+ */
+ if (!sc->force_deactivate) {
+ unsigned long refaults;
+
+ /*
+ * When refaults are being observed, it means a new
+ * workingset is being established. Deactivate to get
+ * rid of any stale active pages quickly.
+ */
+ refaults = lruvec_page_state(target_lruvec,
+ WORKINGSET_ACTIVATE_ANON);
+ if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
+ inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
+ sc->may_deactivate |= DEACTIVATE_ANON;
+ else
+ sc->may_deactivate &= ~DEACTIVATE_ANON;
+
+ refaults = lruvec_page_state(target_lruvec,
+ WORKINGSET_ACTIVATE_FILE);
+ if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
+ inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
+ sc->may_deactivate |= DEACTIVATE_FILE;
+ else
+ sc->may_deactivate &= ~DEACTIVATE_FILE;
+ } else
+ sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
+
+ /*
+ * If we have plenty of inactive file pages that aren't
+ * thrashing, try to reclaim those first before touching
+ * anonymous pages.
+ */
+ file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
+ if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
+ sc->cache_trim_mode = 1;
+ else
+ sc->cache_trim_mode = 0;
+
+ /*
+ * 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 (!cgroup_reclaim(sc)) {
+ unsigned long total_high_wmark = 0;
+ unsigned long free, anon;
+ int z;
+
+ free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
+ file = 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);
+ }
+
+ /*
+ * Consider anon: if that's low too, this isn't a
+ * runaway file reclaim problem, but rather just
+ * extreme pressure. Reclaim as per usual then.
+ */
+ anon = node_page_state(pgdat, NR_INACTIVE_ANON);
+
+ sc->file_is_tiny =
+ file + free <= total_high_wmark &&
+ !(sc->may_deactivate & DEACTIVATE_ANON) &&
+ anon >> sc->priority;
+ }
+}
+
+/*
+ * Determine how aggressively the anon and file LRU lists should be
+ * scanned.
+ *
+ * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
+ * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
+ */
+static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
+ unsigned long *nr)
+{
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ unsigned long anon_cost, file_cost, total_cost;
+ int swappiness = mem_cgroup_swappiness(memcg);
+ u64 fraction[ANON_AND_FILE];
+ u64 denominator = 0; /* gcc */
+ enum scan_balance scan_balance;
+ unsigned long ap, fp;
+ enum lru_list lru;
+
+ /* If we have no swap space, do not bother scanning anon folios. */
+ if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
+ 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 (cgroup_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;
+ }
+
+ /*
+ * If the system is almost out of file pages, force-scan anon.
+ */
+ if (sc->file_is_tiny) {
+ scan_balance = SCAN_ANON;
+ goto out;
+ }
+
+ /*
+ * If there is enough inactive page cache, we do not reclaim
+ * anything from the anonymous working right now.
+ */
+ if (sc->cache_trim_mode) {
+ scan_balance = SCAN_FILE;
+ goto out;
+ }
+
+ scan_balance = SCAN_FRACT;
+ /*
+ * Calculate the pressure balance between anon and file pages.
+ *
+ * The amount of pressure we put on each LRU is inversely
+ * proportional to the cost of reclaiming each list, as
+ * determined by the share of pages that are refaulting, times
+ * the relative IO cost of bringing back a swapped out
+ * anonymous page vs reloading a filesystem page (swappiness).
+ *
+ * Although we limit that influence to ensure no list gets
+ * left behind completely: at least a third of the pressure is
+ * applied, before swappiness.
+ *
+ * With swappiness at 100, anon and file have equal IO cost.
+ */
+ total_cost = sc->anon_cost + sc->file_cost;
+ anon_cost = total_cost + sc->anon_cost;
+ file_cost = total_cost + sc->file_cost;
+ total_cost = anon_cost + file_cost;
+
+ ap = swappiness * (total_cost + 1);
+ ap /= anon_cost + 1;
+
+ fp = (200 - swappiness) * (total_cost + 1);
+ fp /= file_cost + 1;
+
+ fraction[0] = ap;
+ fraction[1] = fp;
+ denominator = ap + fp;
+out:
+ for_each_evictable_lru(lru) {
+ int file = is_file_lru(lru);
+ unsigned long lruvec_size;
+ unsigned long low, min;
+ unsigned long scan;
+
+ lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
+ mem_cgroup_protection(sc->target_mem_cgroup, memcg,
+ &min, &low);
+
+ if (min || low) {
+ /*
+ * Scale a cgroup's reclaim pressure by proportioning
+ * its current usage to its memory.low or memory.min
+ * setting.
+ *
+ * This is important, as otherwise scanning aggression
+ * becomes extremely binary -- from nothing as we
+ * approach the memory protection threshold, to totally
+ * nominal as we exceed it. This results in requiring
+ * setting extremely liberal protection thresholds. It
+ * also means we simply get no protection at all if we
+ * set it too low, which is not ideal.
+ *
+ * If there is any protection in place, we reduce scan
+ * pressure by how much of the total memory used is
+ * within protection thresholds.
+ *
+ * There is one special case: in the first reclaim pass,
+ * we skip over all groups that are within their low
+ * protection. If that fails to reclaim enough pages to
+ * satisfy the reclaim goal, we come back and override
+ * the best-effort low protection. However, we still
+ * ideally want to honor how well-behaved groups are in
+ * that case instead of simply punishing them all
+ * equally. As such, we reclaim them based on how much
+ * memory they are using, reducing the scan pressure
+ * again by how much of the total memory used is under
+ * hard protection.
+ */
+ unsigned long cgroup_size = mem_cgroup_size(memcg);
+ unsigned long protection;
+
+ /* memory.low scaling, make sure we retry before OOM */
+ if (!sc->memcg_low_reclaim && low > min) {
+ protection = low;
+ sc->memcg_low_skipped = 1;
+ } else {
+ protection = min;
+ }
+
+ /* Avoid TOCTOU with earlier protection check */
+ cgroup_size = max(cgroup_size, protection);
+
+ scan = lruvec_size - lruvec_size * protection /
+ (cgroup_size + 1);
+
+ /*
+ * Minimally target SWAP_CLUSTER_MAX pages to keep
+ * reclaim moving forwards, avoiding decrementing
+ * sc->priority further than desirable.
+ */
+ scan = max(scan, SWAP_CLUSTER_MAX);
+ } else {
+ scan = lruvec_size;
+ }
+
+ scan >>= 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(lruvec_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 on
+ * the offlined memory cgroups because of a
+ * round-off error.
+ */
+ scan = mem_cgroup_online(memcg) ?
+ div64_u64(scan * fraction[file], denominator) :
+ 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)
+ scan = 0;
+ break;
+ default:
+ /* Look ma, no brain */
+ BUG();
+ }
+
+ nr[lru] = scan;
+ }
+}
+
+/*
+ * Anonymous LRU management is a waste if there is
+ * ultimately no way to reclaim the memory.
+ */
+static bool can_age_anon_pages(struct pglist_data *pgdat,
+ struct scan_control *sc)
+{
+ /* Aging the anon LRU is valuable if swap is present: */
+ if (total_swap_pages > 0)
+ return true;
+
+ /* Also valuable if anon pages can be demoted: */
+ return can_demote(pgdat->node_id, sc);
+}
+
+#ifdef CONFIG_LRU_GEN
+
+#ifdef CONFIG_LRU_GEN_ENABLED
+DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
+#define get_cap(cap) static_branch_likely(&lru_gen_caps[cap])
+#else
+DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
+#define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap])
+#endif
+
+static bool should_walk_mmu(void)
+{
+ return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK);
+}
+
+static bool should_clear_pmd_young(void)
+{
+ return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG);
+}
+
+/******************************************************************************
+ * shorthand helpers
+ ******************************************************************************/
+
+#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
+
+#define DEFINE_MAX_SEQ(lruvec) \
+ unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
+
+#define DEFINE_MIN_SEQ(lruvec) \
+ unsigned long min_seq[ANON_AND_FILE] = { \
+ READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \
+ READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \
+ }
+
+#define for_each_gen_type_zone(gen, type, zone) \
+ for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \
+ for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \
+ for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
+
+#define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS)
+#define get_memcg_bin(bin) ((bin) % MEMCG_NR_BINS)
+
+static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
+{
+ struct pglist_data *pgdat = NODE_DATA(nid);
+
+#ifdef CONFIG_MEMCG
+ if (memcg) {
+ struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
+
+ /* see the comment in mem_cgroup_lruvec() */
+ if (!lruvec->pgdat)
+ lruvec->pgdat = pgdat;
+
+ return lruvec;
+ }
+#endif
+ VM_WARN_ON_ONCE(!mem_cgroup_disabled());
+
+ return &pgdat->__lruvec;
+}
+
+static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
+{
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ if (!sc->may_swap)
+ return 0;
+
+ if (!can_demote(pgdat->node_id, sc) &&
+ mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
+ return 0;
+
+ return mem_cgroup_swappiness(memcg);
+}
+
+static int get_nr_gens(struct lruvec *lruvec, int type)
+{
+ return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
+}
+
+static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
+{
+ /* see the comment on lru_gen_folio */
+ return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
+ get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
+ get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
+}
+
+/******************************************************************************
+ * Bloom filters
+ ******************************************************************************/
+
+/*
+ * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
+ * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
+ * bits in a bitmap, k is the number of hash functions and n is the number of
+ * inserted items.
+ *
+ * Page table walkers use one of the two filters to reduce their search space.
+ * To get rid of non-leaf entries that no longer have enough leaf entries, the
+ * aging uses the double-buffering technique to flip to the other filter each
+ * time it produces a new generation. For non-leaf entries that have enough
+ * leaf entries, the aging carries them over to the next generation in
+ * walk_pmd_range(); the eviction also report them when walking the rmap
+ * in lru_gen_look_around().
+ *
+ * For future optimizations:
+ * 1. It's not necessary to keep both filters all the time. The spare one can be
+ * freed after the RCU grace period and reallocated if needed again.
+ * 2. And when reallocating, it's worth scaling its size according to the number
+ * of inserted entries in the other filter, to reduce the memory overhead on
+ * small systems and false positives on large systems.
+ * 3. Jenkins' hash function is an alternative to Knuth's.
+ */
+#define BLOOM_FILTER_SHIFT 15
+
+static inline int filter_gen_from_seq(unsigned long seq)
+{
+ return seq % NR_BLOOM_FILTERS;
+}
+
+static void get_item_key(void *item, int *key)
+{
+ u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
+
+ BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
+
+ key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
+ key[1] = hash >> BLOOM_FILTER_SHIFT;
+}
+
+static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
+{
+ int key[2];
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ filter = READ_ONCE(lruvec->mm_state.filters[gen]);
+ if (!filter)
+ return true;
+
+ get_item_key(item, key);
+
+ return test_bit(key[0], filter) && test_bit(key[1], filter);
+}
+
+static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
+{
+ int key[2];
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ filter = READ_ONCE(lruvec->mm_state.filters[gen]);
+ if (!filter)
+ return;
+
+ get_item_key(item, key);
+
+ if (!test_bit(key[0], filter))
+ set_bit(key[0], filter);
+ if (!test_bit(key[1], filter))
+ set_bit(key[1], filter);
+}
+
+static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq)
+{
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ filter = lruvec->mm_state.filters[gen];
+ if (filter) {
+ bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
+ return;
+ }
+
+ filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
+ __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
+ WRITE_ONCE(lruvec->mm_state.filters[gen], filter);
+}
+
+/******************************************************************************
+ * mm_struct list
+ ******************************************************************************/
+
+static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
+{
+ static struct lru_gen_mm_list mm_list = {
+ .fifo = LIST_HEAD_INIT(mm_list.fifo),
+ .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
+ };
+
+#ifdef CONFIG_MEMCG
+ if (memcg)
+ return &memcg->mm_list;
+#endif
+ VM_WARN_ON_ONCE(!mem_cgroup_disabled());
+
+ return &mm_list;
+}
+
+void lru_gen_add_mm(struct mm_struct *mm)
+{
+ int nid;
+ struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+
+ VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
+#ifdef CONFIG_MEMCG
+ VM_WARN_ON_ONCE(mm->lru_gen.memcg);
+ mm->lru_gen.memcg = memcg;
+#endif
+ spin_lock(&mm_list->lock);
+
+ for_each_node_state(nid, N_MEMORY) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ /* the first addition since the last iteration */
+ if (lruvec->mm_state.tail == &mm_list->fifo)
+ lruvec->mm_state.tail = &mm->lru_gen.list;
+ }
+
+ list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
+
+ spin_unlock(&mm_list->lock);
+}
+
+void lru_gen_del_mm(struct mm_struct *mm)
+{
+ int nid;
+ struct lru_gen_mm_list *mm_list;
+ struct mem_cgroup *memcg = NULL;
+
+ if (list_empty(&mm->lru_gen.list))
+ return;
+
+#ifdef CONFIG_MEMCG
+ memcg = mm->lru_gen.memcg;
+#endif
+ mm_list = get_mm_list(memcg);
+
+ spin_lock(&mm_list->lock);
+
+ for_each_node(nid) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ /* where the current iteration continues after */
+ if (lruvec->mm_state.head == &mm->lru_gen.list)
+ lruvec->mm_state.head = lruvec->mm_state.head->prev;
+
+ /* where the last iteration ended before */
+ if (lruvec->mm_state.tail == &mm->lru_gen.list)
+ lruvec->mm_state.tail = lruvec->mm_state.tail->next;
+ }
+
+ list_del_init(&mm->lru_gen.list);
+
+ spin_unlock(&mm_list->lock);
+
+#ifdef CONFIG_MEMCG
+ mem_cgroup_put(mm->lru_gen.memcg);
+ mm->lru_gen.memcg = NULL;
+#endif
+}
+
+#ifdef CONFIG_MEMCG
+void lru_gen_migrate_mm(struct mm_struct *mm)
+{
+ struct mem_cgroup *memcg;
+ struct task_struct *task = rcu_dereference_protected(mm->owner, true);
+
+ VM_WARN_ON_ONCE(task->mm != mm);
+ lockdep_assert_held(&task->alloc_lock);
+
+ /* for mm_update_next_owner() */
+ if (mem_cgroup_disabled())
+ return;
+
+ /* migration can happen before addition */
+ if (!mm->lru_gen.memcg)
+ return;
+
+ rcu_read_lock();
+ memcg = mem_cgroup_from_task(task);
+ rcu_read_unlock();
+ if (memcg == mm->lru_gen.memcg)
+ return;
+
+ VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
+
+ lru_gen_del_mm(mm);
+ lru_gen_add_mm(mm);
+}
+#endif
+
+static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
+{
+ int i;
+ int hist;
+
+ lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
+
+ if (walk) {
+ hist = lru_hist_from_seq(walk->max_seq);
+
+ for (i = 0; i < NR_MM_STATS; i++) {
+ WRITE_ONCE(lruvec->mm_state.stats[hist][i],
+ lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]);
+ walk->mm_stats[i] = 0;
+ }
+ }
+
+ if (NR_HIST_GENS > 1 && last) {
+ hist = lru_hist_from_seq(lruvec->mm_state.seq + 1);
+
+ for (i = 0; i < NR_MM_STATS; i++)
+ WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0);
+ }
+}
+
+static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
+{
+ int type;
+ unsigned long size = 0;
+ struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
+ int key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
+
+ if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
+ return true;
+
+ clear_bit(key, &mm->lru_gen.bitmap);
+
+ for (type = !walk->can_swap; type < ANON_AND_FILE; type++) {
+ size += type ? get_mm_counter(mm, MM_FILEPAGES) :
+ get_mm_counter(mm, MM_ANONPAGES) +
+ get_mm_counter(mm, MM_SHMEMPAGES);
+ }
+
+ if (size < MIN_LRU_BATCH)
+ return true;
+
+ return !mmget_not_zero(mm);
+}
+
+static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
+ struct mm_struct **iter)
+{
+ bool first = false;
+ bool last = false;
+ struct mm_struct *mm = NULL;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+ struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
+
+ /*
+ * mm_state->seq is incremented after each iteration of mm_list. There
+ * are three interesting cases for this page table walker:
+ * 1. It tries to start a new iteration with a stale max_seq: there is
+ * nothing left to do.
+ * 2. It started the next iteration: it needs to reset the Bloom filter
+ * so that a fresh set of PTE tables can be recorded.
+ * 3. It ended the current iteration: it needs to reset the mm stats
+ * counters and tell its caller to increment max_seq.
+ */
+ spin_lock(&mm_list->lock);
+
+ VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq);
+
+ if (walk->max_seq <= mm_state->seq)
+ goto done;
+
+ if (!mm_state->head)
+ mm_state->head = &mm_list->fifo;
+
+ if (mm_state->head == &mm_list->fifo)
+ first = true;
+
+ do {
+ mm_state->head = mm_state->head->next;
+ if (mm_state->head == &mm_list->fifo) {
+ WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
+ last = true;
+ break;
+ }
+
+ /* force scan for those added after the last iteration */
+ if (!mm_state->tail || mm_state->tail == mm_state->head) {
+ mm_state->tail = mm_state->head->next;
+ walk->force_scan = true;
+ }
+
+ mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
+ if (should_skip_mm(mm, walk))
+ mm = NULL;
+ } while (!mm);
+done:
+ if (*iter || last)
+ reset_mm_stats(lruvec, walk, last);
+
+ spin_unlock(&mm_list->lock);
+
+ if (mm && first)
+ reset_bloom_filter(lruvec, walk->max_seq + 1);
+
+ if (*iter)
+ mmput_async(*iter);
+
+ *iter = mm;
+
+ return last;
+}
+
+static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
+{
+ bool success = false;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+ struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
+
+ spin_lock(&mm_list->lock);
+
+ VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq);
+
+ if (max_seq > mm_state->seq) {
+ mm_state->head = NULL;
+ mm_state->tail = NULL;
+ WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
+ reset_mm_stats(lruvec, NULL, true);
+ success = true;
+ }
+
+ spin_unlock(&mm_list->lock);
+
+ return success;
+}
+
+/******************************************************************************
+ * PID controller
+ ******************************************************************************/
+
+/*
+ * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
+ *
+ * The P term is refaulted/(evicted+protected) from a tier in the generation
+ * currently being evicted; the I term is the exponential moving average of the
+ * P term over the generations previously evicted, using the smoothing factor
+ * 1/2; the D term isn't supported.
+ *
+ * The setpoint (SP) is always the first tier of one type; the process variable
+ * (PV) is either any tier of the other type or any other tier of the same
+ * type.
+ *
+ * The error is the difference between the SP and the PV; the correction is to
+ * turn off protection when SP>PV or turn on protection when SP<PV.
+ *
+ * For future optimizations:
+ * 1. The D term may discount the other two terms over time so that long-lived
+ * generations can resist stale information.
+ */
+struct ctrl_pos {
+ unsigned long refaulted;
+ unsigned long total;
+ int gain;
+};
+
+static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
+ struct ctrl_pos *pos)
+{
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ int hist = lru_hist_from_seq(lrugen->min_seq[type]);
+
+ pos->refaulted = lrugen->avg_refaulted[type][tier] +
+ atomic_long_read(&lrugen->refaulted[hist][type][tier]);
+ pos->total = lrugen->avg_total[type][tier] +
+ atomic_long_read(&lrugen->evicted[hist][type][tier]);
+ if (tier)
+ pos->total += lrugen->protected[hist][type][tier - 1];
+ pos->gain = gain;
+}
+
+static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
+{
+ int hist, tier;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
+ unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
+
+ lockdep_assert_held(&lruvec->lru_lock);
+
+ if (!carryover && !clear)
+ return;
+
+ hist = lru_hist_from_seq(seq);
+
+ for (tier = 0; tier < MAX_NR_TIERS; tier++) {
+ if (carryover) {
+ unsigned long sum;
+
+ sum = lrugen->avg_refaulted[type][tier] +
+ atomic_long_read(&lrugen->refaulted[hist][type][tier]);
+ WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
+
+ sum = lrugen->avg_total[type][tier] +
+ atomic_long_read(&lrugen->evicted[hist][type][tier]);
+ if (tier)
+ sum += lrugen->protected[hist][type][tier - 1];
+ WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
+ }
+
+ if (clear) {
+ atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
+ atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
+ if (tier)
+ WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0);
+ }
+ }
+}
+
+static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
+{
+ /*
+ * Return true if the PV has a limited number of refaults or a lower
+ * refaulted/total than the SP.
+ */
+ return pv->refaulted < MIN_LRU_BATCH ||
+ pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
+ (sp->refaulted + 1) * pv->total * pv->gain;
+}
+
+/******************************************************************************
+ * the aging
+ ******************************************************************************/
+
+/* promote pages accessed through page tables */
+static int folio_update_gen(struct folio *folio, int gen)
+{
+ unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
+
+ VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
+ VM_WARN_ON_ONCE(!rcu_read_lock_held());
+
+ do {
+ /* lru_gen_del_folio() has isolated this page? */
+ if (!(old_flags & LRU_GEN_MASK)) {
+ /* for shrink_folio_list() */
+ new_flags = old_flags | BIT(PG_referenced);
+ continue;
+ }
+
+ new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
+ new_flags |= (gen + 1UL) << LRU_GEN_PGOFF;
+ } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
+
+ return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+}
+
+/* protect pages accessed multiple times through file descriptors */
+static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
+{
+ int type = folio_is_file_lru(folio);
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
+ unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
+
+ VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
+
+ do {
+ new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+ /* folio_update_gen() has promoted this page? */
+ if (new_gen >= 0 && new_gen != old_gen)
+ return new_gen;
+
+ new_gen = (old_gen + 1) % MAX_NR_GENS;
+
+ new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
+ new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
+ /* for folio_end_writeback() */
+ if (reclaiming)
+ new_flags |= BIT(PG_reclaim);
+ } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
+
+ lru_gen_update_size(lruvec, folio, old_gen, new_gen);
+
+ return new_gen;
+}
+
+static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
+ int old_gen, int new_gen)
+{
+ int type = folio_is_file_lru(folio);
+ int zone = folio_zonenum(folio);
+ int delta = folio_nr_pages(folio);
+
+ VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
+ VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
+
+ walk->batched++;
+
+ walk->nr_pages[old_gen][type][zone] -= delta;
+ walk->nr_pages[new_gen][type][zone] += delta;
+}
+
+static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
+{
+ int gen, type, zone;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ walk->batched = 0;
+
+ for_each_gen_type_zone(gen, type, zone) {
+ enum lru_list lru = type * LRU_INACTIVE_FILE;
+ int delta = walk->nr_pages[gen][type][zone];
+
+ if (!delta)
+ continue;
+
+ walk->nr_pages[gen][type][zone] = 0;
+ WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
+ lrugen->nr_pages[gen][type][zone] + delta);
+
+ if (lru_gen_is_active(lruvec, gen))
+ lru += LRU_ACTIVE;
+ __update_lru_size(lruvec, lru, zone, delta);
+ }
+}
+
+static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
+{
+ struct address_space *mapping;
+ struct vm_area_struct *vma = args->vma;
+ struct lru_gen_mm_walk *walk = args->private;
+
+ if (!vma_is_accessible(vma))
+ return true;
+
+ if (is_vm_hugetlb_page(vma))
+ return true;
+
+ if (!vma_has_recency(vma))
+ return true;
+
+ if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
+ return true;
+
+ if (vma == get_gate_vma(vma->vm_mm))
+ return true;
+
+ if (vma_is_anonymous(vma))
+ return !walk->can_swap;
+
+ if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
+ return true;
+
+ mapping = vma->vm_file->f_mapping;
+ if (mapping_unevictable(mapping))
+ return true;
+
+ if (shmem_mapping(mapping))
+ return !walk->can_swap;
+
+ /* to exclude special mappings like dax, etc. */
+ return !mapping->a_ops->read_folio;
+}
+
+/*
+ * Some userspace memory allocators map many single-page VMAs. Instead of
+ * returning back to the PGD table for each of such VMAs, finish an entire PMD
+ * table to reduce zigzags and improve cache performance.
+ */
+static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
+ unsigned long *vm_start, unsigned long *vm_end)
+{
+ unsigned long start = round_up(*vm_end, size);
+ unsigned long end = (start | ~mask) + 1;
+ VMA_ITERATOR(vmi, args->mm, start);
+
+ VM_WARN_ON_ONCE(mask & size);
+ VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
+
+ for_each_vma(vmi, args->vma) {
+ if (end && end <= args->vma->vm_start)
+ return false;
+
+ if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
+ continue;
+
+ *vm_start = max(start, args->vma->vm_start);
+ *vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
+
+ return true;
+ }
+
+ return false;
+}
+
+static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
+{
+ unsigned long pfn = pte_pfn(pte);
+
+ VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
+
+ if (!pte_present(pte) || is_zero_pfn(pfn))
+ return -1;
+
+ if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
+ return -1;
+
+ if (WARN_ON_ONCE(!pfn_valid(pfn)))
+ return -1;
+
+ return pfn;
+}
+
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
+static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
+{
+ unsigned long pfn = pmd_pfn(pmd);
+
+ VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
+
+ if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
+ return -1;
+
+ if (WARN_ON_ONCE(pmd_devmap(pmd)))
+ return -1;
+
+ if (WARN_ON_ONCE(!pfn_valid(pfn)))
+ return -1;
+
+ return pfn;
+}
+#endif
+
+static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
+ struct pglist_data *pgdat, bool can_swap)
+{
+ struct folio *folio;
+
+ /* try to avoid unnecessary memory loads */
+ if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
+ return NULL;
+
+ folio = pfn_folio(pfn);
+ if (folio_nid(folio) != pgdat->node_id)
+ return NULL;
+
+ if (folio_memcg_rcu(folio) != memcg)
+ return NULL;
+
+ /* file VMAs can contain anon pages from COW */
+ if (!folio_is_file_lru(folio) && !can_swap)
+ return NULL;
+
+ return folio;
+}
+
+static bool suitable_to_scan(int total, int young)
+{
+ int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
+
+ /* suitable if the average number of young PTEs per cacheline is >=1 */
+ return young * n >= total;
+}
+
+static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
+ struct mm_walk *args)
+{
+ int i;
+ pte_t *pte;
+ spinlock_t *ptl;
+ unsigned long addr;
+ int total = 0;
+ int young = 0;
+ struct lru_gen_mm_walk *walk = args->private;
+ struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
+ int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
+
+ pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl);
+ if (!pte)
+ return false;
+ if (!spin_trylock(ptl)) {
+ pte_unmap(pte);
+ return false;
+ }
+
+ arch_enter_lazy_mmu_mode();
+restart:
+ for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
+ unsigned long pfn;
+ struct folio *folio;
+ pte_t ptent = ptep_get(pte + i);
+
+ total++;
+ walk->mm_stats[MM_LEAF_TOTAL]++;
+
+ pfn = get_pte_pfn(ptent, args->vma, addr);
+ if (pfn == -1)
+ continue;
+
+ if (!pte_young(ptent)) {
+ walk->mm_stats[MM_LEAF_OLD]++;
+ continue;
+ }
+
+ folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
+ if (!folio)
+ continue;
+
+ if (!ptep_test_and_clear_young(args->vma, addr, pte + i))
+ VM_WARN_ON_ONCE(true);
+
+ young++;
+ walk->mm_stats[MM_LEAF_YOUNG]++;
+
+ if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
+ !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_test_swapcache(folio)))
+ folio_mark_dirty(folio);
+
+ old_gen = folio_update_gen(folio, new_gen);
+ if (old_gen >= 0 && old_gen != new_gen)
+ update_batch_size(walk, folio, old_gen, new_gen);
+ }
+
+ if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
+ goto restart;
+
+ arch_leave_lazy_mmu_mode();
+ pte_unmap_unlock(pte, ptl);
+
+ return suitable_to_scan(total, young);
+}
+
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
+static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
+ struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
+{
+ int i;
+ pmd_t *pmd;
+ spinlock_t *ptl;
+ struct lru_gen_mm_walk *walk = args->private;
+ struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
+ int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
+
+ VM_WARN_ON_ONCE(pud_leaf(*pud));
+
+ /* try to batch at most 1+MIN_LRU_BATCH+1 entries */
+ if (*first == -1) {
+ *first = addr;
+ bitmap_zero(bitmap, MIN_LRU_BATCH);
+ return;
+ }
+
+ i = addr == -1 ? 0 : pmd_index(addr) - pmd_index(*first);
+ if (i && i <= MIN_LRU_BATCH) {
+ __set_bit(i - 1, bitmap);
+ return;
+ }
+
+ pmd = pmd_offset(pud, *first);
+
+ ptl = pmd_lockptr(args->mm, pmd);
+ if (!spin_trylock(ptl))
+ goto done;
+
+ arch_enter_lazy_mmu_mode();
+
+ do {
+ unsigned long pfn;
+ struct folio *folio;
+
+ /* don't round down the first address */
+ addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first;
+
+ pfn = get_pmd_pfn(pmd[i], vma, addr);
+ if (pfn == -1)
+ goto next;
+
+ if (!pmd_trans_huge(pmd[i])) {
+ if (should_clear_pmd_young())
+ pmdp_test_and_clear_young(vma, addr, pmd + i);
+ goto next;
+ }
+
+ folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
+ if (!folio)
+ goto next;
+
+ if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
+ goto next;
+
+ walk->mm_stats[MM_LEAF_YOUNG]++;
+
+ if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
+ !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_test_swapcache(folio)))
+ folio_mark_dirty(folio);
+
+ old_gen = folio_update_gen(folio, new_gen);
+ if (old_gen >= 0 && old_gen != new_gen)
+ update_batch_size(walk, folio, old_gen, new_gen);
+next:
+ i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
+ } while (i <= MIN_LRU_BATCH);
+
+ arch_leave_lazy_mmu_mode();
+ spin_unlock(ptl);
+done:
+ *first = -1;
+}
+#else
+static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
+ struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
+{
+}
+#endif
+
+static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
+ struct mm_walk *args)
+{
+ int i;
+ pmd_t *pmd;
+ unsigned long next;
+ unsigned long addr;
+ struct vm_area_struct *vma;
+ DECLARE_BITMAP(bitmap, MIN_LRU_BATCH);
+ unsigned long first = -1;
+ struct lru_gen_mm_walk *walk = args->private;
+
+ VM_WARN_ON_ONCE(pud_leaf(*pud));
+
+ /*
+ * Finish an entire PMD in two passes: the first only reaches to PTE
+ * tables to avoid taking the PMD lock; the second, if necessary, takes
+ * the PMD lock to clear the accessed bit in PMD entries.
+ */
+ pmd = pmd_offset(pud, start & PUD_MASK);
+restart:
+ /* walk_pte_range() may call get_next_vma() */
+ vma = args->vma;
+ for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
+ pmd_t val = pmdp_get_lockless(pmd + i);
+
+ next = pmd_addr_end(addr, end);
+
+ if (!pmd_present(val) || is_huge_zero_pmd(val)) {
+ walk->mm_stats[MM_LEAF_TOTAL]++;
+ continue;
+ }
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ if (pmd_trans_huge(val)) {
+ unsigned long pfn = pmd_pfn(val);
+ struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
+
+ walk->mm_stats[MM_LEAF_TOTAL]++;
+
+ if (!pmd_young(val)) {
+ walk->mm_stats[MM_LEAF_OLD]++;
+ continue;
+ }
+
+ /* try to avoid unnecessary memory loads */
+ if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
+ continue;
+
+ walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
+ continue;
+ }
+#endif
+ walk->mm_stats[MM_NONLEAF_TOTAL]++;
+
+ if (should_clear_pmd_young()) {
+ if (!pmd_young(val))
+ continue;
+
+ walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
+ }
+
+ if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq, pmd + i))
+ continue;
+
+ walk->mm_stats[MM_NONLEAF_FOUND]++;
+
+ if (!walk_pte_range(&val, addr, next, args))
+ continue;
+
+ walk->mm_stats[MM_NONLEAF_ADDED]++;
+
+ /* carry over to the next generation */
+ update_bloom_filter(walk->lruvec, walk->max_seq + 1, pmd + i);
+ }
+
+ walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first);
+
+ if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
+ goto restart;
+}
+
+static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
+ struct mm_walk *args)
+{
+ int i;
+ pud_t *pud;
+ unsigned long addr;
+ unsigned long next;
+ struct lru_gen_mm_walk *walk = args->private;
+
+ VM_WARN_ON_ONCE(p4d_leaf(*p4d));
+
+ pud = pud_offset(p4d, start & P4D_MASK);
+restart:
+ for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
+ pud_t val = READ_ONCE(pud[i]);
+
+ next = pud_addr_end(addr, end);
+
+ if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
+ continue;
+
+ walk_pmd_range(&val, addr, next, args);
+
+ if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
+ end = (addr | ~PUD_MASK) + 1;
+ goto done;
+ }
+ }
+
+ if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
+ goto restart;
+
+ end = round_up(end, P4D_SIZE);
+done:
+ if (!end || !args->vma)
+ return 1;
+
+ walk->next_addr = max(end, args->vma->vm_start);
+
+ return -EAGAIN;
+}
+
+static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
+{
+ static const struct mm_walk_ops mm_walk_ops = {
+ .test_walk = should_skip_vma,
+ .p4d_entry = walk_pud_range,
+ .walk_lock = PGWALK_RDLOCK,
+ };
+
+ int err;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+ walk->next_addr = FIRST_USER_ADDRESS;
+
+ do {
+ DEFINE_MAX_SEQ(lruvec);
+
+ err = -EBUSY;
+
+ /* another thread might have called inc_max_seq() */
+ if (walk->max_seq != max_seq)
+ break;
+
+ /* folio_update_gen() requires stable folio_memcg() */
+ if (!mem_cgroup_trylock_pages(memcg))
+ break;
+
+ /* the caller might be holding the lock for write */
+ if (mmap_read_trylock(mm)) {
+ err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
+
+ mmap_read_unlock(mm);
+ }
+
+ mem_cgroup_unlock_pages();
+
+ if (walk->batched) {
+ spin_lock_irq(&lruvec->lru_lock);
+ reset_batch_size(lruvec, walk);
+ spin_unlock_irq(&lruvec->lru_lock);
+ }
+
+ cond_resched();
+ } while (err == -EAGAIN);
+}
+
+static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc)
+{
+ struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
+
+ if (pgdat && current_is_kswapd()) {
+ VM_WARN_ON_ONCE(walk);
+
+ walk = &pgdat->mm_walk;
+ } else if (!walk && force_alloc) {
+ VM_WARN_ON_ONCE(current_is_kswapd());
+
+ walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
+ }
+
+ current->reclaim_state->mm_walk = walk;
+
+ return walk;
+}
+
+static void clear_mm_walk(void)
+{
+ struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
+
+ VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
+ VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
+
+ current->reclaim_state->mm_walk = NULL;
+
+ if (!current_is_kswapd())
+ kfree(walk);
+}
+
+static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
+{
+ int zone;
+ int remaining = MAX_LRU_BATCH;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
+
+ if (type == LRU_GEN_ANON && !can_swap)
+ goto done;
+
+ /* prevent cold/hot inversion if force_scan is true */
+ for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+ struct list_head *head = &lrugen->folios[old_gen][type][zone];
+
+ while (!list_empty(head)) {
+ struct folio *folio = lru_to_folio(head);
+
+ VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
+
+ new_gen = folio_inc_gen(lruvec, folio, false);
+ list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
+
+ if (!--remaining)
+ return false;
+ }
+ }
+done:
+ reset_ctrl_pos(lruvec, type, true);
+ WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
+
+ return true;
+}
+
+static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
+{
+ int gen, type, zone;
+ bool success = false;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ DEFINE_MIN_SEQ(lruvec);
+
+ VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
+
+ /* find the oldest populated generation */
+ for (type = !can_swap; type < ANON_AND_FILE; type++) {
+ while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
+ gen = lru_gen_from_seq(min_seq[type]);
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+ if (!list_empty(&lrugen->folios[gen][type][zone]))
+ goto next;
+ }
+
+ min_seq[type]++;
+ }
+next:
+ ;
+ }
+
+ /* see the comment on lru_gen_folio */
+ if (can_swap) {
+ min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]);
+ min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]);
+ }
+
+ for (type = !can_swap; type < ANON_AND_FILE; type++) {
+ if (min_seq[type] == lrugen->min_seq[type])
+ continue;
+
+ reset_ctrl_pos(lruvec, type, true);
+ WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
+ success = true;
+ }
+
+ return success;
+}
+
+static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan)
+{
+ int prev, next;
+ int type, zone;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+restart:
+ spin_lock_irq(&lruvec->lru_lock);
+
+ VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
+
+ for (type = ANON_AND_FILE - 1; type >= 0; type--) {
+ if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
+ continue;
+
+ VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
+
+ if (inc_min_seq(lruvec, type, can_swap))
+ continue;
+
+ spin_unlock_irq(&lruvec->lru_lock);
+ cond_resched();
+ goto restart;
+ }
+
+ /*
+ * Update the active/inactive LRU sizes for compatibility. Both sides of
+ * the current max_seq need to be covered, since max_seq+1 can overlap
+ * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
+ * overlap, cold/hot inversion happens.
+ */
+ prev = lru_gen_from_seq(lrugen->max_seq - 1);
+ next = lru_gen_from_seq(lrugen->max_seq + 1);
+
+ for (type = 0; type < ANON_AND_FILE; type++) {
+ for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+ enum lru_list lru = type * LRU_INACTIVE_FILE;
+ long delta = lrugen->nr_pages[prev][type][zone] -
+ lrugen->nr_pages[next][type][zone];
+
+ if (!delta)
+ continue;
+
+ __update_lru_size(lruvec, lru, zone, delta);
+ __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
+ }
+ }
+
+ for (type = 0; type < ANON_AND_FILE; type++)
+ reset_ctrl_pos(lruvec, type, false);
+
+ WRITE_ONCE(lrugen->timestamps[next], jiffies);
+ /* make sure preceding modifications appear */
+ smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
+
+ spin_unlock_irq(&lruvec->lru_lock);
+}
+
+static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
+ struct scan_control *sc, bool can_swap, bool force_scan)
+{
+ bool success;
+ struct lru_gen_mm_walk *walk;
+ struct mm_struct *mm = NULL;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq));
+
+ /* see the comment in iterate_mm_list() */
+ if (max_seq <= READ_ONCE(lruvec->mm_state.seq)) {
+ success = false;
+ goto done;
+ }
+
+ /*
+ * If the hardware doesn't automatically set the accessed bit, fallback
+ * to lru_gen_look_around(), which only clears the accessed bit in a
+ * handful of PTEs. Spreading the work out over a period of time usually
+ * is less efficient, but it avoids bursty page faults.
+ */
+ if (!should_walk_mmu()) {
+ success = iterate_mm_list_nowalk(lruvec, max_seq);
+ goto done;
+ }
+
+ walk = set_mm_walk(NULL, true);
+ if (!walk) {
+ success = iterate_mm_list_nowalk(lruvec, max_seq);
+ goto done;
+ }
+
+ walk->lruvec = lruvec;
+ walk->max_seq = max_seq;
+ walk->can_swap = can_swap;
+ walk->force_scan = force_scan;
+
+ do {
+ success = iterate_mm_list(lruvec, walk, &mm);
+ if (mm)
+ walk_mm(lruvec, mm, walk);
+ } while (mm);
+done:
+ if (success)
+ inc_max_seq(lruvec, can_swap, force_scan);
+
+ return success;
+}
+
+/******************************************************************************
+ * working set protection
+ ******************************************************************************/
+
+static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
+{
+ int gen, type, zone;
+ unsigned long total = 0;
+ bool can_swap = get_swappiness(lruvec, sc);
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ DEFINE_MAX_SEQ(lruvec);
+ DEFINE_MIN_SEQ(lruvec);
+
+ for (type = !can_swap; type < ANON_AND_FILE; type++) {
+ unsigned long seq;
+
+ for (seq = min_seq[type]; seq <= max_seq; seq++) {
+ gen = lru_gen_from_seq(seq);
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++)
+ total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
+ }
+ }
+
+ /* whether the size is big enough to be helpful */
+ return mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
+}
+
+static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc,
+ unsigned long min_ttl)
+{
+ int gen;
+ unsigned long birth;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ DEFINE_MIN_SEQ(lruvec);
+
+ /* see the comment on lru_gen_folio */
+ gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
+ birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
+
+ if (time_is_after_jiffies(birth + min_ttl))
+ return false;
+
+ if (!lruvec_is_sizable(lruvec, sc))
+ return false;
+
+ mem_cgroup_calculate_protection(NULL, memcg);
+
+ return !mem_cgroup_below_min(NULL, memcg);
+}
+
+/* to protect the working set of the last N jiffies */
+static unsigned long lru_gen_min_ttl __read_mostly;
+
+static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ struct mem_cgroup *memcg;
+ unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
+
+ VM_WARN_ON_ONCE(!current_is_kswapd());
+
+ /* check the order to exclude compaction-induced reclaim */
+ if (!min_ttl || sc->order || sc->priority == DEF_PRIORITY)
+ return;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
+
+ if (lruvec_is_reclaimable(lruvec, sc, min_ttl)) {
+ mem_cgroup_iter_break(NULL, memcg);
+ return;
+ }
+
+ cond_resched();
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
+
+ /*
+ * The main goal is to OOM kill if every generation from all memcgs is
+ * younger than min_ttl. However, another possibility is all memcgs are
+ * either too small or below min.
+ */
+ if (mutex_trylock(&oom_lock)) {
+ struct oom_control oc = {
+ .gfp_mask = sc->gfp_mask,
+ };
+
+ out_of_memory(&oc);
+
+ mutex_unlock(&oom_lock);
+ }
+}
+
+/******************************************************************************
+ * rmap/PT walk feedback
+ ******************************************************************************/
+
+/*
+ * This function exploits spatial locality when shrink_folio_list() walks the
+ * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
+ * the scan was done cacheline efficiently, it adds the PMD entry pointing to
+ * the PTE table to the Bloom filter. This forms a feedback loop between the
+ * eviction and the aging.
+ */
+void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
+{
+ int i;
+ unsigned long start;
+ unsigned long end;
+ struct lru_gen_mm_walk *walk;
+ int young = 0;
+ pte_t *pte = pvmw->pte;
+ unsigned long addr = pvmw->address;
+ struct vm_area_struct *vma = pvmw->vma;
+ struct folio *folio = pfn_folio(pvmw->pfn);
+ bool can_swap = !folio_is_file_lru(folio);
+ struct mem_cgroup *memcg = folio_memcg(folio);
+ struct pglist_data *pgdat = folio_pgdat(folio);
+ struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
+ DEFINE_MAX_SEQ(lruvec);
+ int old_gen, new_gen = lru_gen_from_seq(max_seq);
+
+ lockdep_assert_held(pvmw->ptl);
+ VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
+
+ if (spin_is_contended(pvmw->ptl))
+ return;
+
+ /* exclude special VMAs containing anon pages from COW */
+ if (vma->vm_flags & VM_SPECIAL)
+ return;
+
+ /* avoid taking the LRU lock under the PTL when possible */
+ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
+
+ start = max(addr & PMD_MASK, vma->vm_start);
+ end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1;
+
+ if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
+ if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
+ end = start + MIN_LRU_BATCH * PAGE_SIZE;
+ else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2)
+ start = end - MIN_LRU_BATCH * PAGE_SIZE;
+ else {
+ start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2;
+ end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2;
+ }
+ }
+
+ /* folio_update_gen() requires stable folio_memcg() */
+ if (!mem_cgroup_trylock_pages(memcg))
+ return;
+
+ arch_enter_lazy_mmu_mode();
+
+ pte -= (addr - start) / PAGE_SIZE;
+
+ for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
+ unsigned long pfn;
+ pte_t ptent = ptep_get(pte + i);
+
+ pfn = get_pte_pfn(ptent, vma, addr);
+ if (pfn == -1)
+ continue;
+
+ if (!pte_young(ptent))
+ continue;
+
+ folio = get_pfn_folio(pfn, memcg, pgdat, can_swap);
+ if (!folio)
+ continue;
+
+ if (!ptep_test_and_clear_young(vma, addr, pte + i))
+ VM_WARN_ON_ONCE(true);
+
+ young++;
+
+ if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
+ !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_test_swapcache(folio)))
+ folio_mark_dirty(folio);
+
+ if (walk) {
+ old_gen = folio_update_gen(folio, new_gen);
+ if (old_gen >= 0 && old_gen != new_gen)
+ update_batch_size(walk, folio, old_gen, new_gen);
+
+ continue;
+ }
+
+ old_gen = folio_lru_gen(folio);
+ if (old_gen < 0)
+ folio_set_referenced(folio);
+ else if (old_gen != new_gen)
+ folio_activate(folio);
+ }
+
+ arch_leave_lazy_mmu_mode();
+ mem_cgroup_unlock_pages();
+
+ /* feedback from rmap walkers to page table walkers */
+ if (suitable_to_scan(i, young))
+ update_bloom_filter(lruvec, max_seq, pvmw->pmd);
+}
+
+/******************************************************************************
+ * memcg LRU
+ ******************************************************************************/
+
+/* see the comment on MEMCG_NR_GENS */
+enum {
+ MEMCG_LRU_NOP,
+ MEMCG_LRU_HEAD,
+ MEMCG_LRU_TAIL,
+ MEMCG_LRU_OLD,
+ MEMCG_LRU_YOUNG,
+};
+
+#ifdef CONFIG_MEMCG
+
+static int lru_gen_memcg_seg(struct lruvec *lruvec)
+{
+ return READ_ONCE(lruvec->lrugen.seg);
+}
+
+static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
+{
+ int seg;
+ int old, new;
+ unsigned long flags;
+ int bin = get_random_u32_below(MEMCG_NR_BINS);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ spin_lock_irqsave(&pgdat->memcg_lru.lock, flags);
+
+ VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
+
+ seg = 0;
+ new = old = lruvec->lrugen.gen;
+
+ /* see the comment on MEMCG_NR_GENS */
+ if (op == MEMCG_LRU_HEAD)
+ seg = MEMCG_LRU_HEAD;
+ else if (op == MEMCG_LRU_TAIL)
+ seg = MEMCG_LRU_TAIL;
+ else if (op == MEMCG_LRU_OLD)
+ new = get_memcg_gen(pgdat->memcg_lru.seq);
+ else if (op == MEMCG_LRU_YOUNG)
+ new = get_memcg_gen(pgdat->memcg_lru.seq + 1);
+ else
+ VM_WARN_ON_ONCE(true);
+
+ WRITE_ONCE(lruvec->lrugen.seg, seg);
+ WRITE_ONCE(lruvec->lrugen.gen, new);
+
+ hlist_nulls_del_rcu(&lruvec->lrugen.list);
+
+ if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD)
+ hlist_nulls_add_head_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
+ else
+ hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
+
+ pgdat->memcg_lru.nr_memcgs[old]--;
+ pgdat->memcg_lru.nr_memcgs[new]++;
+
+ if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq))
+ WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
+
+ spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags);
+}
+
+void lru_gen_online_memcg(struct mem_cgroup *memcg)
+{
+ int gen;
+ int nid;
+ int bin = get_random_u32_below(MEMCG_NR_BINS);
+
+ for_each_node(nid) {
+ struct pglist_data *pgdat = NODE_DATA(nid);
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ spin_lock_irq(&pgdat->memcg_lru.lock);
+
+ VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
+
+ gen = get_memcg_gen(pgdat->memcg_lru.seq);
+
+ lruvec->lrugen.gen = gen;
+
+ hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]);
+ pgdat->memcg_lru.nr_memcgs[gen]++;
+
+ spin_unlock_irq(&pgdat->memcg_lru.lock);
+ }
+}
+
+void lru_gen_offline_memcg(struct mem_cgroup *memcg)
+{
+ int nid;
+
+ for_each_node(nid) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ lru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD);
+ }
+}
+
+void lru_gen_release_memcg(struct mem_cgroup *memcg)
+{
+ int gen;
+ int nid;
+
+ for_each_node(nid) {
+ struct pglist_data *pgdat = NODE_DATA(nid);
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ spin_lock_irq(&pgdat->memcg_lru.lock);
+
+ if (hlist_nulls_unhashed(&lruvec->lrugen.list))
+ goto unlock;
+
+ gen = lruvec->lrugen.gen;
+
+ hlist_nulls_del_init_rcu(&lruvec->lrugen.list);
+ pgdat->memcg_lru.nr_memcgs[gen]--;
+
+ if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))
+ WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
+unlock:
+ spin_unlock_irq(&pgdat->memcg_lru.lock);
+ }
+}
+
+void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
+{
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ /* see the comment on MEMCG_NR_GENS */
+ if (lru_gen_memcg_seg(lruvec) != MEMCG_LRU_HEAD)
+ lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);
+}
+
+#else /* !CONFIG_MEMCG */
+
+static int lru_gen_memcg_seg(struct lruvec *lruvec)
+{
+ return 0;
+}
+
+#endif
+
+/******************************************************************************
+ * the eviction
+ ******************************************************************************/
+
+static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
+ int tier_idx)
+{
+ bool success;
+ int gen = folio_lru_gen(folio);
+ int type = folio_is_file_lru(folio);
+ int zone = folio_zonenum(folio);
+ int delta = folio_nr_pages(folio);
+ int refs = folio_lru_refs(folio);
+ int tier = lru_tier_from_refs(refs);
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
+
+ /* unevictable */
+ if (!folio_evictable(folio)) {
+ success = lru_gen_del_folio(lruvec, folio, true);
+ VM_WARN_ON_ONCE_FOLIO(!success, folio);
+ folio_set_unevictable(folio);
+ lruvec_add_folio(lruvec, folio);
+ __count_vm_events(UNEVICTABLE_PGCULLED, delta);
+ return true;
+ }
+
+ /* dirty lazyfree */
+ if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) {
+ success = lru_gen_del_folio(lruvec, folio, true);
+ VM_WARN_ON_ONCE_FOLIO(!success, folio);
+ folio_set_swapbacked(folio);
+ lruvec_add_folio_tail(lruvec, folio);
+ return true;
+ }
+
+ /* promoted */
+ if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
+ list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
+ return true;
+ }
+
+ /* protected */
+ if (tier > tier_idx || refs == BIT(LRU_REFS_WIDTH)) {
+ int hist = lru_hist_from_seq(lrugen->min_seq[type]);
+
+ gen = folio_inc_gen(lruvec, folio, false);
+ list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
+
+ WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
+ lrugen->protected[hist][type][tier - 1] + delta);
+ return true;
+ }
+
+ /* ineligible */
+ if (zone > sc->reclaim_idx || skip_cma(folio, sc)) {
+ gen = folio_inc_gen(lruvec, folio, false);
+ list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
+ return true;
+ }
+
+ /* waiting for writeback */
+ if (folio_test_locked(folio) || folio_test_writeback(folio) ||
+ (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
+ gen = folio_inc_gen(lruvec, folio, true);
+ list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
+ return true;
+ }
+
+ return false;
+}
+
+static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
+{
+ bool success;
+
+ /* swapping inhibited */
+ if (!(sc->gfp_mask & __GFP_IO) &&
+ (folio_test_dirty(folio) ||
+ (folio_test_anon(folio) && !folio_test_swapcache(folio))))
+ return false;
+
+ /* raced with release_pages() */
+ if (!folio_try_get(folio))
+ return false;
+
+ /* raced with another isolation */
+ if (!folio_test_clear_lru(folio)) {
+ folio_put(folio);
+ return false;
+ }
+
+ /* see the comment on MAX_NR_TIERS */
+ if (!folio_test_referenced(folio))
+ set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0);
+
+ /* for shrink_folio_list() */
+ folio_clear_reclaim(folio);
+ folio_clear_referenced(folio);
+
+ success = lru_gen_del_folio(lruvec, folio, true);
+ VM_WARN_ON_ONCE_FOLIO(!success, folio);
+
+ return true;
+}
+
+static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
+ int type, int tier, struct list_head *list)
+{
+ int i;
+ int gen;
+ enum vm_event_item item;
+ int sorted = 0;
+ int scanned = 0;
+ int isolated = 0;
+ int remaining = MAX_LRU_BATCH;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+ VM_WARN_ON_ONCE(!list_empty(list));
+
+ if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
+ return 0;
+
+ gen = lru_gen_from_seq(lrugen->min_seq[type]);
+
+ for (i = MAX_NR_ZONES; i > 0; i--) {
+ LIST_HEAD(moved);
+ int skipped = 0;
+ int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
+ struct list_head *head = &lrugen->folios[gen][type][zone];
+
+ while (!list_empty(head)) {
+ struct folio *folio = lru_to_folio(head);
+ int delta = folio_nr_pages(folio);
+
+ VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
+
+ scanned += delta;
+
+ if (sort_folio(lruvec, folio, sc, tier))
+ sorted += delta;
+ else if (isolate_folio(lruvec, folio, sc)) {
+ list_add(&folio->lru, list);
+ isolated += delta;
+ } else {
+ list_move(&folio->lru, &moved);
+ skipped += delta;
+ }
+
+ if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
+ break;
+ }
+
+ if (skipped) {
+ list_splice(&moved, head);
+ __count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
+ }
+
+ if (!remaining || isolated >= MIN_LRU_BATCH)
+ break;
+ }
+
+ item = PGSCAN_KSWAPD + reclaimer_offset();
+ if (!cgroup_reclaim(sc)) {
+ __count_vm_events(item, isolated);
+ __count_vm_events(PGREFILL, sorted);
+ }
+ __count_memcg_events(memcg, item, isolated);
+ __count_memcg_events(memcg, PGREFILL, sorted);
+ __count_vm_events(PGSCAN_ANON + type, isolated);
+
+ /*
+ * There might not be eligible folios due to reclaim_idx. Check the
+ * remaining to prevent livelock if it's not making progress.
+ */
+ return isolated || !remaining ? scanned : 0;
+}
+
+static int get_tier_idx(struct lruvec *lruvec, int type)
+{
+ int tier;
+ struct ctrl_pos sp, pv;
+
+ /*
+ * To leave a margin for fluctuations, use a larger gain factor (1:2).
+ * This value is chosen because any other tier would have at least twice
+ * as many refaults as the first tier.
+ */
+ read_ctrl_pos(lruvec, type, 0, 1, &sp);
+ for (tier = 1; tier < MAX_NR_TIERS; tier++) {
+ read_ctrl_pos(lruvec, type, tier, 2, &pv);
+ if (!positive_ctrl_err(&sp, &pv))
+ break;
+ }
+
+ return tier - 1;
+}
+
+static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
+{
+ int type, tier;
+ struct ctrl_pos sp, pv;
+ int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness };
+
+ /*
+ * Compare the first tier of anon with that of file to determine which
+ * type to scan. Also need to compare other tiers of the selected type
+ * with the first tier of the other type to determine the last tier (of
+ * the selected type) to evict.
+ */
+ read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
+ read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
+ type = positive_ctrl_err(&sp, &pv);
+
+ read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
+ for (tier = 1; tier < MAX_NR_TIERS; tier++) {
+ read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
+ if (!positive_ctrl_err(&sp, &pv))
+ break;
+ }
+
+ *tier_idx = tier - 1;
+
+ return type;
+}
+
+static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
+ int *type_scanned, struct list_head *list)
+{
+ int i;
+ int type;
+ int scanned;
+ int tier = -1;
+ DEFINE_MIN_SEQ(lruvec);
+
+ /*
+ * Try to make the obvious choice first. When anon and file are both
+ * available from the same generation, interpret swappiness 1 as file
+ * first and 200 as anon first.
+ */
+ if (!swappiness)
+ type = LRU_GEN_FILE;
+ else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
+ type = LRU_GEN_ANON;
+ else if (swappiness == 1)
+ type = LRU_GEN_FILE;
+ else if (swappiness == 200)
+ type = LRU_GEN_ANON;
+ else
+ type = get_type_to_scan(lruvec, swappiness, &tier);
+
+ for (i = !swappiness; i < ANON_AND_FILE; i++) {
+ if (tier < 0)
+ tier = get_tier_idx(lruvec, type);
+
+ scanned = scan_folios(lruvec, sc, type, tier, list);
+ if (scanned)
+ break;
+
+ type = !type;
+ tier = -1;
+ }
+
+ *type_scanned = type;
+
+ return scanned;
+}
+
+static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
+{
+ int type;
+ int scanned;
+ int reclaimed;
+ LIST_HEAD(list);
+ LIST_HEAD(clean);
+ struct folio *folio;
+ struct folio *next;
+ enum vm_event_item item;
+ struct reclaim_stat stat;
+ struct lru_gen_mm_walk *walk;
+ bool skip_retry = false;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ spin_lock_irq(&lruvec->lru_lock);
+
+ scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
+
+ scanned += try_to_inc_min_seq(lruvec, swappiness);
+
+ if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS)
+ scanned = 0;
+
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ if (list_empty(&list))
+ return scanned;
+retry:
+ reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
+ sc->nr_reclaimed += reclaimed;
+
+ list_for_each_entry_safe_reverse(folio, next, &list, lru) {
+ if (!folio_evictable(folio)) {
+ list_del(&folio->lru);
+ folio_putback_lru(folio);
+ continue;
+ }
+
+ if (folio_test_reclaim(folio) &&
+ (folio_test_dirty(folio) || folio_test_writeback(folio))) {
+ /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
+ if (folio_test_workingset(folio))
+ folio_set_referenced(folio);
+ continue;
+ }
+
+ if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
+ folio_mapped(folio) || folio_test_locked(folio) ||
+ folio_test_dirty(folio) || folio_test_writeback(folio)) {
+ /* don't add rejected folios to the oldest generation */
+ set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
+ BIT(PG_active));
+ continue;
+ }
+
+ /* retry folios that may have missed folio_rotate_reclaimable() */
+ list_move(&folio->lru, &clean);
+ sc->nr_scanned -= folio_nr_pages(folio);
+ }
+
+ spin_lock_irq(&lruvec->lru_lock);
+
+ move_folios_to_lru(lruvec, &list);
+
+ walk = current->reclaim_state->mm_walk;
+ if (walk && walk->batched)
+ reset_batch_size(lruvec, walk);
+
+ item = PGSTEAL_KSWAPD + reclaimer_offset();
+ if (!cgroup_reclaim(sc))
+ __count_vm_events(item, reclaimed);
+ __count_memcg_events(memcg, item, reclaimed);
+ __count_vm_events(PGSTEAL_ANON + type, reclaimed);
+
+ spin_unlock_irq(&lruvec->lru_lock);
+
+ mem_cgroup_uncharge_list(&list);
+ free_unref_page_list(&list);
+
+ INIT_LIST_HEAD(&list);
+ list_splice_init(&clean, &list);
+
+ if (!list_empty(&list)) {
+ skip_retry = true;
+ goto retry;
+ }
+
+ return scanned;
+}
+
+static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
+ struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan)
+{
+ int gen, type, zone;
+ unsigned long old = 0;
+ unsigned long young = 0;
+ unsigned long total = 0;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ DEFINE_MIN_SEQ(lruvec);
+
+ /* whether this lruvec is completely out of cold folios */
+ if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) {
+ *nr_to_scan = 0;
+ return true;
+ }
+
+ for (type = !can_swap; type < ANON_AND_FILE; type++) {
+ unsigned long seq;
+
+ for (seq = min_seq[type]; seq <= max_seq; seq++) {
+ unsigned long size = 0;
+
+ gen = lru_gen_from_seq(seq);
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++)
+ size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
+
+ total += size;
+ if (seq == max_seq)
+ young += size;
+ else if (seq + MIN_NR_GENS == max_seq)
+ old += size;
+ }
+ }
+
+ /* try to scrape all its memory if this memcg was deleted */
+ if (!mem_cgroup_online(memcg)) {
+ *nr_to_scan = total;
+ return false;
+ }
+
+ *nr_to_scan = total >> sc->priority;
+
+ /*
+ * The aging tries to be lazy to reduce the overhead, while the eviction
+ * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
+ * ideal number of generations is MIN_NR_GENS+1.
+ */
+ if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
+ return false;
+
+ /*
+ * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
+ * of the total number of pages for each generation. A reasonable range
+ * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
+ * aging cares about the upper bound of hot pages, while the eviction
+ * cares about the lower bound of cold pages.
+ */
+ if (young * MIN_NR_GENS > total)
+ return true;
+ if (old * (MIN_NR_GENS + 2) < total)
+ return true;
+
+ return false;
+}
+
+/*
+ * For future optimizations:
+ * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
+ * reclaim.
+ */
+static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap)
+{
+ unsigned long nr_to_scan;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ DEFINE_MAX_SEQ(lruvec);
+
+ if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg))
+ return -1;
+
+ if (!should_run_aging(lruvec, max_seq, sc, can_swap, &nr_to_scan))
+ return nr_to_scan;
+
+ /* skip the aging path at the default priority */
+ if (sc->priority == DEF_PRIORITY)
+ return nr_to_scan;
+
+ /* skip this lruvec as it's low on cold folios */
+ return try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false) ? -1 : 0;
+}
+
+static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
+{
+ int i;
+ enum zone_watermarks mark;
+
+ /* don't abort memcg reclaim to ensure fairness */
+ if (!root_reclaim(sc))
+ return false;
+
+ if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
+ return true;
+
+ /* check the order to exclude compaction-induced reclaim */
+ if (!current_is_kswapd() || sc->order)
+ return false;
+
+ mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ?
+ WMARK_PROMO : WMARK_HIGH;
+
+ for (i = 0; i <= sc->reclaim_idx; i++) {
+ struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
+ unsigned long size = wmark_pages(zone, mark) + MIN_LRU_BATCH;
+
+ if (managed_zone(zone) && !zone_watermark_ok(zone, 0, size, sc->reclaim_idx, 0))
+ return false;
+ }
+
+ /* kswapd should abort if all eligible zones are safe */
+ return true;
+}
+
+static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+ long nr_to_scan;
+ unsigned long scanned = 0;
+ int swappiness = get_swappiness(lruvec, sc);
+
+ /* clean file folios are more likely to exist */
+ if (swappiness && !(sc->gfp_mask & __GFP_IO))
+ swappiness = 1;
+
+ while (true) {
+ int delta;
+
+ nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness);
+ if (nr_to_scan <= 0)
+ break;
+
+ delta = evict_folios(lruvec, sc, swappiness);
+ if (!delta)
+ break;
+
+ scanned += delta;
+ if (scanned >= nr_to_scan)
+ break;
+
+ if (should_abort_scan(lruvec, sc))
+ break;
+
+ cond_resched();
+ }
+
+ /* whether this lruvec should be rotated */
+ return nr_to_scan < 0;
+}
+
+static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
+{
+ bool success;
+ unsigned long scanned = sc->nr_scanned;
+ unsigned long reclaimed = sc->nr_reclaimed;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+ mem_cgroup_calculate_protection(NULL, memcg);
+
+ if (mem_cgroup_below_min(NULL, memcg))
+ return MEMCG_LRU_YOUNG;
+
+ if (mem_cgroup_below_low(NULL, memcg)) {
+ /* see the comment on MEMCG_NR_GENS */
+ if (lru_gen_memcg_seg(lruvec) != MEMCG_LRU_TAIL)
+ return MEMCG_LRU_TAIL;
+
+ memcg_memory_event(memcg, MEMCG_LOW);
+ }
+
+ success = try_to_shrink_lruvec(lruvec, sc);
+
+ shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority);
+
+ if (!sc->proactive)
+ vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned,
+ sc->nr_reclaimed - reclaimed);
+
+ flush_reclaim_state(sc);
+
+ if (success && mem_cgroup_online(memcg))
+ return MEMCG_LRU_YOUNG;
+
+ if (!success && lruvec_is_sizable(lruvec, sc))
+ return 0;
+
+ /* one retry if offlined or too small */
+ return lru_gen_memcg_seg(lruvec) != MEMCG_LRU_TAIL ?
+ MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
+}
+
+#ifdef CONFIG_MEMCG
+
+static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ int op;
+ int gen;
+ int bin;
+ int first_bin;
+ struct lruvec *lruvec;
+ struct lru_gen_folio *lrugen;
+ struct mem_cgroup *memcg;
+ struct hlist_nulls_node *pos;
+
+ gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
+ bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
+restart:
+ op = 0;
+ memcg = NULL;
+
+ rcu_read_lock();
+
+ hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) {
+ if (op) {
+ lru_gen_rotate_memcg(lruvec, op);
+ op = 0;
+ }
+
+ mem_cgroup_put(memcg);
+ memcg = NULL;
+
+ if (gen != READ_ONCE(lrugen->gen))
+ continue;
+
+ lruvec = container_of(lrugen, struct lruvec, lrugen);
+ memcg = lruvec_memcg(lruvec);
+
+ if (!mem_cgroup_tryget(memcg)) {
+ lru_gen_release_memcg(memcg);
+ memcg = NULL;
+ continue;
+ }
+
+ rcu_read_unlock();
+
+ op = shrink_one(lruvec, sc);
+
+ rcu_read_lock();
+
+ if (should_abort_scan(lruvec, sc))
+ break;
+ }
+
+ rcu_read_unlock();
+
+ if (op)
+ lru_gen_rotate_memcg(lruvec, op);
+
+ mem_cgroup_put(memcg);
+
+ if (!is_a_nulls(pos))
+ return;
+
+ /* restart if raced with lru_gen_rotate_memcg() */
+ if (gen != get_nulls_value(pos))
+ goto restart;
+
+ /* try the rest of the bins of the current generation */
+ bin = get_memcg_bin(bin + 1);
+ if (bin != first_bin)
+ goto restart;
+}
+
+static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+ struct blk_plug plug;
+
+ VM_WARN_ON_ONCE(root_reclaim(sc));
+ VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap);
+
+ lru_add_drain();
+
+ blk_start_plug(&plug);
+
+ set_mm_walk(NULL, sc->proactive);
+
+ if (try_to_shrink_lruvec(lruvec, sc))
+ lru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);
+
+ clear_mm_walk();
+
+ blk_finish_plug(&plug);
+}
+
+#else /* !CONFIG_MEMCG */
+
+static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ BUILD_BUG();
+}
+
+static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+ BUILD_BUG();
+}
+
+#endif
+
+static void set_initial_priority(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ int priority;
+ unsigned long reclaimable;
+ struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
+
+ if (sc->priority != DEF_PRIORITY || sc->nr_to_reclaim < MIN_LRU_BATCH)
+ return;
+ /*
+ * Determine the initial priority based on
+ * (total >> priority) * reclaimed_to_scanned_ratio = nr_to_reclaim,
+ * where reclaimed_to_scanned_ratio = inactive / total.
+ */
+ reclaimable = node_page_state(pgdat, NR_INACTIVE_FILE);
+ if (get_swappiness(lruvec, sc))
+ reclaimable += node_page_state(pgdat, NR_INACTIVE_ANON);
+
+ /* round down reclaimable and round up sc->nr_to_reclaim */
+ priority = fls_long(reclaimable) - 1 - fls_long(sc->nr_to_reclaim - 1);
+
+ sc->priority = clamp(priority, 0, DEF_PRIORITY);
+}
+
+static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ struct blk_plug plug;
+ unsigned long reclaimed = sc->nr_reclaimed;
+
+ VM_WARN_ON_ONCE(!root_reclaim(sc));
+
+ /*
+ * Unmapped clean folios are already prioritized. Scanning for more of
+ * them is likely futile and can cause high reclaim latency when there
+ * is a large number of memcgs.
+ */
+ if (!sc->may_writepage || !sc->may_unmap)
+ goto done;
+
+ lru_add_drain();
+
+ blk_start_plug(&plug);
+
+ set_mm_walk(pgdat, sc->proactive);
+
+ set_initial_priority(pgdat, sc);
+
+ if (current_is_kswapd())
+ sc->nr_reclaimed = 0;
+
+ if (mem_cgroup_disabled())
+ shrink_one(&pgdat->__lruvec, sc);
+ else
+ shrink_many(pgdat, sc);
+
+ if (current_is_kswapd())
+ sc->nr_reclaimed += reclaimed;
+
+ clear_mm_walk();
+
+ blk_finish_plug(&plug);
+done:
+ /* kswapd should never fail */
+ pgdat->kswapd_failures = 0;
+}
+
+/******************************************************************************
+ * state change
+ ******************************************************************************/
+
+static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
+{
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ if (lrugen->enabled) {
+ enum lru_list lru;
+
+ for_each_evictable_lru(lru) {
+ if (!list_empty(&lruvec->lists[lru]))
+ return false;
+ }
+ } else {
+ int gen, type, zone;
+
+ for_each_gen_type_zone(gen, type, zone) {
+ if (!list_empty(&lrugen->folios[gen][type][zone]))
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static bool fill_evictable(struct lruvec *lruvec)
+{
+ enum lru_list lru;
+ int remaining = MAX_LRU_BATCH;
+
+ for_each_evictable_lru(lru) {
+ int type = is_file_lru(lru);
+ bool active = is_active_lru(lru);
+ struct list_head *head = &lruvec->lists[lru];
+
+ while (!list_empty(head)) {
+ bool success;
+ struct folio *folio = lru_to_folio(head);
+
+ VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
+
+ lruvec_del_folio(lruvec, folio);
+ success = lru_gen_add_folio(lruvec, folio, false);
+ VM_WARN_ON_ONCE(!success);
+
+ if (!--remaining)
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static bool drain_evictable(struct lruvec *lruvec)
+{
+ int gen, type, zone;
+ int remaining = MAX_LRU_BATCH;
+
+ for_each_gen_type_zone(gen, type, zone) {
+ struct list_head *head = &lruvec->lrugen.folios[gen][type][zone];
+
+ while (!list_empty(head)) {
+ bool success;
+ struct folio *folio = lru_to_folio(head);
+
+ VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
+ VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
+
+ success = lru_gen_del_folio(lruvec, folio, false);
+ VM_WARN_ON_ONCE(!success);
+ lruvec_add_folio(lruvec, folio);
+
+ if (!--remaining)
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static void lru_gen_change_state(bool enabled)
+{
+ static DEFINE_MUTEX(state_mutex);
+
+ struct mem_cgroup *memcg;
+
+ cgroup_lock();
+ cpus_read_lock();
+ get_online_mems();
+ mutex_lock(&state_mutex);
+
+ if (enabled == lru_gen_enabled())
+ goto unlock;
+
+ if (enabled)
+ static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
+ else
+ static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ int nid;
+
+ for_each_node(nid) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ spin_lock_irq(&lruvec->lru_lock);
+
+ VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
+ VM_WARN_ON_ONCE(!state_is_valid(lruvec));
+
+ lruvec->lrugen.enabled = enabled;
+
+ while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
+ spin_unlock_irq(&lruvec->lru_lock);
+ cond_resched();
+ spin_lock_irq(&lruvec->lru_lock);
+ }
+
+ spin_unlock_irq(&lruvec->lru_lock);
+ }
+
+ cond_resched();
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
+unlock:
+ mutex_unlock(&state_mutex);
+ put_online_mems();
+ cpus_read_unlock();
+ cgroup_unlock();
+}
+
+/******************************************************************************
+ * sysfs interface
+ ******************************************************************************/
+
+static ssize_t min_ttl_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
+}
+
+/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
+static ssize_t min_ttl_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t len)
+{
+ unsigned int msecs;
+
+ if (kstrtouint(buf, 0, &msecs))
+ return -EINVAL;
+
+ WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
+
+ return len;
+}
+
+static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR_RW(min_ttl_ms);
+
+static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ unsigned int caps = 0;
+
+ if (get_cap(LRU_GEN_CORE))
+ caps |= BIT(LRU_GEN_CORE);
+
+ if (should_walk_mmu())
+ caps |= BIT(LRU_GEN_MM_WALK);
+
+ if (should_clear_pmd_young())
+ caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
+
+ return sysfs_emit(buf, "0x%04x\n", caps);
+}
+
+/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
+static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t len)
+{
+ int i;
+ unsigned int caps;
+
+ if (tolower(*buf) == 'n')
+ caps = 0;
+ else if (tolower(*buf) == 'y')
+ caps = -1;
+ else if (kstrtouint(buf, 0, &caps))
+ return -EINVAL;
+
+ for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
+ bool enabled = caps & BIT(i);
+
+ if (i == LRU_GEN_CORE)
+ lru_gen_change_state(enabled);
+ else if (enabled)
+ static_branch_enable(&lru_gen_caps[i]);
+ else
+ static_branch_disable(&lru_gen_caps[i]);
+ }
+
+ return len;
+}
+
+static struct kobj_attribute lru_gen_enabled_attr = __ATTR_RW(enabled);
+
+static struct attribute *lru_gen_attrs[] = {
+ &lru_gen_min_ttl_attr.attr,
+ &lru_gen_enabled_attr.attr,
+ NULL
+};
+
+static const struct attribute_group lru_gen_attr_group = {
+ .name = "lru_gen",
+ .attrs = lru_gen_attrs,
+};
+
+/******************************************************************************
+ * debugfs interface
+ ******************************************************************************/
+
+static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
+{
+ struct mem_cgroup *memcg;
+ loff_t nr_to_skip = *pos;
+
+ m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
+ if (!m->private)
+ return ERR_PTR(-ENOMEM);
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ int nid;
+
+ for_each_node_state(nid, N_MEMORY) {
+ if (!nr_to_skip--)
+ return get_lruvec(memcg, nid);
+ }
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
+
+ return NULL;
+}
+
+static void lru_gen_seq_stop(struct seq_file *m, void *v)
+{
+ if (!IS_ERR_OR_NULL(v))
+ mem_cgroup_iter_break(NULL, lruvec_memcg(v));
+
+ kvfree(m->private);
+ m->private = NULL;
+}
+
+static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ int nid = lruvec_pgdat(v)->node_id;
+ struct mem_cgroup *memcg = lruvec_memcg(v);
+
+ ++*pos;
+
+ nid = next_memory_node(nid);
+ if (nid == MAX_NUMNODES) {
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ if (!memcg)
+ return NULL;
+
+ nid = first_memory_node;
+ }
+
+ return get_lruvec(memcg, nid);
+}
+
+static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
+ unsigned long max_seq, unsigned long *min_seq,
+ unsigned long seq)
+{
+ int i;
+ int type, tier;
+ int hist = lru_hist_from_seq(seq);
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ for (tier = 0; tier < MAX_NR_TIERS; tier++) {
+ seq_printf(m, " %10d", tier);
+ for (type = 0; type < ANON_AND_FILE; type++) {
+ const char *s = " ";
+ unsigned long n[3] = {};
+
+ if (seq == max_seq) {
+ s = "RT ";
+ n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
+ n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
+ } else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
+ s = "rep";
+ n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
+ n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
+ if (tier)
+ n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]);
+ }
+
+ for (i = 0; i < 3; i++)
+ seq_printf(m, " %10lu%c", n[i], s[i]);
+ }
+ seq_putc(m, '\n');
+ }
+
+ seq_puts(m, " ");
+ for (i = 0; i < NR_MM_STATS; i++) {
+ const char *s = " ";
+ unsigned long n = 0;
+
+ if (seq == max_seq && NR_HIST_GENS == 1) {
+ s = "LOYNFA";
+ n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
+ } else if (seq != max_seq && NR_HIST_GENS > 1) {
+ s = "loynfa";
+ n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
+ }
+
+ seq_printf(m, " %10lu%c", n, s[i]);
+ }
+ seq_putc(m, '\n');
+}
+
+/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
+static int lru_gen_seq_show(struct seq_file *m, void *v)
+{
+ unsigned long seq;
+ bool full = !debugfs_real_fops(m->file)->write;
+ struct lruvec *lruvec = v;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ int nid = lruvec_pgdat(lruvec)->node_id;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ DEFINE_MAX_SEQ(lruvec);
+ DEFINE_MIN_SEQ(lruvec);
+
+ if (nid == first_memory_node) {
+ const char *path = memcg ? m->private : "";
+
+#ifdef CONFIG_MEMCG
+ if (memcg)
+ cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
+#endif
+ seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
+ }
+
+ seq_printf(m, " node %5d\n", nid);
+
+ if (!full)
+ seq = min_seq[LRU_GEN_ANON];
+ else if (max_seq >= MAX_NR_GENS)
+ seq = max_seq - MAX_NR_GENS + 1;
+ else
+ seq = 0;
+
+ for (; seq <= max_seq; seq++) {
+ int type, zone;
+ int gen = lru_gen_from_seq(seq);
+ unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
+
+ seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
+
+ for (type = 0; type < ANON_AND_FILE; type++) {
+ unsigned long size = 0;
+ char mark = full && seq < min_seq[type] ? 'x' : ' ';
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++)
+ size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
+
+ seq_printf(m, " %10lu%c", size, mark);
+ }
+
+ seq_putc(m, '\n');
+
+ if (full)
+ lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
+ }
+
+ return 0;
+}
+
+static const struct seq_operations lru_gen_seq_ops = {
+ .start = lru_gen_seq_start,
+ .stop = lru_gen_seq_stop,
+ .next = lru_gen_seq_next,
+ .show = lru_gen_seq_show,
+};
+
+static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
+ bool can_swap, bool force_scan)
+{
+ DEFINE_MAX_SEQ(lruvec);
+ DEFINE_MIN_SEQ(lruvec);
+
+ if (seq < max_seq)
+ return 0;
+
+ if (seq > max_seq)
+ return -EINVAL;
+
+ if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq)
+ return -ERANGE;
+
+ try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan);
+
+ return 0;
+}
+
+static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
+ int swappiness, unsigned long nr_to_reclaim)
+{
+ DEFINE_MAX_SEQ(lruvec);
+
+ if (seq + MIN_NR_GENS > max_seq)
+ return -EINVAL;
+
+ sc->nr_reclaimed = 0;
+
+ while (!signal_pending(current)) {
+ DEFINE_MIN_SEQ(lruvec);
+
+ if (seq < min_seq[!swappiness])
+ return 0;
+
+ if (sc->nr_reclaimed >= nr_to_reclaim)
+ return 0;
+
+ if (!evict_folios(lruvec, sc, swappiness))
+ return 0;
+
+ cond_resched();
+ }
+
+ return -EINTR;
+}
+
+static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
+ struct scan_control *sc, int swappiness, unsigned long opt)
+{
+ struct lruvec *lruvec;
+ int err = -EINVAL;
+ struct mem_cgroup *memcg = NULL;
+
+ if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
+ return -EINVAL;
+
+ if (!mem_cgroup_disabled()) {
+ rcu_read_lock();
+
+ memcg = mem_cgroup_from_id(memcg_id);
+ if (!mem_cgroup_tryget(memcg))
+ memcg = NULL;
+
+ rcu_read_unlock();
+
+ if (!memcg)
+ return -EINVAL;
+ }
+
+ if (memcg_id != mem_cgroup_id(memcg))
+ goto done;
+
+ lruvec = get_lruvec(memcg, nid);
+
+ if (swappiness < 0)
+ swappiness = get_swappiness(lruvec, sc);
+ else if (swappiness > 200)
+ goto done;
+
+ switch (cmd) {
+ case '+':
+ err = run_aging(lruvec, seq, sc, swappiness, opt);
+ break;
+ case '-':
+ err = run_eviction(lruvec, seq, sc, swappiness, opt);
+ break;
+ }
+done:
+ mem_cgroup_put(memcg);
+
+ return err;
+}
+
+/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
+static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
+ size_t len, loff_t *pos)
+{
+ void *buf;
+ char *cur, *next;
+ unsigned int flags;
+ struct blk_plug plug;
+ int err = -EINVAL;
+ struct scan_control sc = {
+ .may_writepage = true,
+ .may_unmap = true,
+ .may_swap = true,
+ .reclaim_idx = MAX_NR_ZONES - 1,
+ .gfp_mask = GFP_KERNEL,
+ };
+
+ buf = kvmalloc(len + 1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ if (copy_from_user(buf, src, len)) {
+ kvfree(buf);
+ return -EFAULT;
+ }
+
+ set_task_reclaim_state(current, &sc.reclaim_state);
+ flags = memalloc_noreclaim_save();
+ blk_start_plug(&plug);
+ if (!set_mm_walk(NULL, true)) {
+ err = -ENOMEM;
+ goto done;
+ }
+
+ next = buf;
+ next[len] = '\0';
+
+ while ((cur = strsep(&next, ",;\n"))) {
+ int n;
+ int end;
+ char cmd;
+ unsigned int memcg_id;
+ unsigned int nid;
+ unsigned long seq;
+ unsigned int swappiness = -1;
+ unsigned long opt = -1;
+
+ cur = skip_spaces(cur);
+ if (!*cur)
+ continue;
+
+ n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
+ &seq, &end, &swappiness, &end, &opt, &end);
+ if (n < 4 || cur[end]) {
+ err = -EINVAL;
+ break;
+ }
+
+ err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
+ if (err)
+ break;
+ }
+done:
+ clear_mm_walk();
+ blk_finish_plug(&plug);
+ memalloc_noreclaim_restore(flags);
+ set_task_reclaim_state(current, NULL);
+
+ kvfree(buf);
+
+ return err ? : len;
+}
+
+static int lru_gen_seq_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &lru_gen_seq_ops);
+}
+
+static const struct file_operations lru_gen_rw_fops = {
+ .open = lru_gen_seq_open,
+ .read = seq_read,
+ .write = lru_gen_seq_write,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static const struct file_operations lru_gen_ro_fops = {
+ .open = lru_gen_seq_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+/******************************************************************************
+ * initialization
+ ******************************************************************************/
+
+void lru_gen_init_lruvec(struct lruvec *lruvec)
+{
+ int i;
+ int gen, type, zone;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+
+ lrugen->max_seq = MIN_NR_GENS + 1;
+ lrugen->enabled = lru_gen_enabled();
+
+ for (i = 0; i <= MIN_NR_GENS + 1; i++)
+ lrugen->timestamps[i] = jiffies;
+
+ for_each_gen_type_zone(gen, type, zone)
+ INIT_LIST_HEAD(&lrugen->folios[gen][type][zone]);
+
+ lruvec->mm_state.seq = MIN_NR_GENS;
+}
+
+#ifdef CONFIG_MEMCG
+
+void lru_gen_init_pgdat(struct pglist_data *pgdat)
+{
+ int i, j;
+
+ spin_lock_init(&pgdat->memcg_lru.lock);
+
+ for (i = 0; i < MEMCG_NR_GENS; i++) {
+ for (j = 0; j < MEMCG_NR_BINS; j++)
+ INIT_HLIST_NULLS_HEAD(&pgdat->memcg_lru.fifo[i][j], i);
+ }
+}
+
+void lru_gen_init_memcg(struct mem_cgroup *memcg)
+{
+ INIT_LIST_HEAD(&memcg->mm_list.fifo);
+ spin_lock_init(&memcg->mm_list.lock);
+}
+
+void lru_gen_exit_memcg(struct mem_cgroup *memcg)
+{
+ int i;
+ int nid;
+
+ VM_WARN_ON_ONCE(!list_empty(&memcg->mm_list.fifo));
+
+ for_each_node(nid) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
+ sizeof(lruvec->lrugen.nr_pages)));
+
+ lruvec->lrugen.list.next = LIST_POISON1;
+
+ for (i = 0; i < NR_BLOOM_FILTERS; i++) {
+ bitmap_free(lruvec->mm_state.filters[i]);
+ lruvec->mm_state.filters[i] = NULL;
+ }
+ }
+}
+
+#endif /* CONFIG_MEMCG */
+
+static int __init init_lru_gen(void)
+{
+ BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
+ BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
+
+ if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
+ pr_err("lru_gen: failed to create sysfs group\n");
+
+ debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
+ debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
+
+ return 0;
+};
+late_initcall(init_lru_gen);
+
+#else /* !CONFIG_LRU_GEN */
+
+static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
+{
+}
+
+static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+}
+
+static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
+{
+}
+
+#endif /* CONFIG_LRU_GEN */
+
+static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+ 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;
+ bool proportional_reclaim;
+ struct blk_plug plug;
+
+ if (lru_gen_enabled() && !root_reclaim(sc)) {
+ lru_gen_shrink_lruvec(lruvec, sc);
+ return;
+ }
+
+ get_scan_count(lruvec, sc, nr);
+
+ /* 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.
+ */
+ proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
+ sc->priority == DEF_PRIORITY);
+
+ blk_start_plug(&plug);
+ while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
+ nr[LRU_INACTIVE_FILE]) {
+ unsigned long nr_anon, nr_file, percentage;
+ unsigned long nr_scanned;
+
+ for_each_evictable_lru(lru) {
+ if (nr[lru]) {
+ nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
+ nr[lru] -= nr_to_scan;
+
+ nr_reclaimed += shrink_list(lru, nr_to_scan,
+ lruvec, sc);
+ }
+ }
+
+ cond_resched();
+
+ if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
+ 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);
+ }
+ 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 (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
+ inactive_is_low(lruvec, LRU_INACTIVE_ANON))
+ 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_pages() 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,
+ 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;
+
+ /*
+ * 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
+ * with the risk reclaim/compaction and the resulting allocation attempt
+ * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
+ * allocations through requiring that the full LRU list has been scanned
+ * first, by assuming that zero delta of sc->nr_scanned means full LRU
+ * scan, but that approximation was wrong, and there were corner cases
+ * where always a non-zero amount of pages were scanned.
+ */
+ if (!nr_reclaimed)
+ return false;
+
+ /* 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;
+
+ /* Allocation can already succeed, nothing to do */
+ if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
+ sc->reclaim_idx, 0))
+ return false;
+
+ if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
+ 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 (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
+ inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
+
+ return inactive_lru_pages > pages_for_compaction;
+}
+
+static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
+{
+ struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
+ struct mem_cgroup *memcg;
+
+ memcg = mem_cgroup_iter(target_memcg, NULL, NULL);
+ do {
+ struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
+ unsigned long reclaimed;
+ unsigned long scanned;
+
+ /*
+ * This loop can become CPU-bound when target memcgs
+ * aren't eligible for reclaim - either because they
+ * don't have any reclaimable pages, or because their
+ * memory is explicitly protected. Avoid soft lockups.
+ */
+ cond_resched();
+
+ mem_cgroup_calculate_protection(target_memcg, memcg);
+
+ if (mem_cgroup_below_min(target_memcg, memcg)) {
+ /*
+ * Hard protection.
+ * If there is no reclaimable memory, OOM.
+ */
+ continue;
+ } else if (mem_cgroup_below_low(target_memcg, memcg)) {
+ /*
+ * 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);
+ }
+
+ reclaimed = sc->nr_reclaimed;
+ scanned = sc->nr_scanned;
+
+ shrink_lruvec(lruvec, sc);
+
+ shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
+ sc->priority);
+
+ /* Record the group's reclaim efficiency */
+ if (!sc->proactive)
+ vmpressure(sc->gfp_mask, memcg, false,
+ sc->nr_scanned - scanned,
+ sc->nr_reclaimed - reclaimed);
+
+ } while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL)));
+}
+
+static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
+{
+ unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed;
+ struct lruvec *target_lruvec;
+ bool reclaimable = false;
+
+ if (lru_gen_enabled() && root_reclaim(sc)) {
+ lru_gen_shrink_node(pgdat, sc);
+ return;
+ }
+
+ target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
+
+again:
+ memset(&sc->nr, 0, sizeof(sc->nr));
+
+ nr_reclaimed = sc->nr_reclaimed;
+ nr_scanned = sc->nr_scanned;
+
+ prepare_scan_count(pgdat, sc);
+
+ shrink_node_memcgs(pgdat, sc);
+
+ flush_reclaim_state(sc);
+
+ nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed;
+
+ /* Record the subtree's reclaim efficiency */
+ if (!sc->proactive)
+ vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
+ sc->nr_scanned - nr_scanned, nr_node_reclaimed);
+
+ if (nr_node_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);
+
+ /* 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 for immediate
+ * reclaim and under writeback (nr_immediate), it
+ * implies that pages are cycling through the LRU
+ * faster than they are written so forcibly stall
+ * until some pages complete writeback.
+ */
+ if (sc->nr.immediate)
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
+ }
+
+ /*
+ * Tag a node/memcg as congested if all the dirty pages were marked
+ * for writeback and immediate reclaim (counted in nr.congested).
+ *
+ * Legacy memcg will stall in page writeback so avoid forcibly
+ * stalling in reclaim_throttle().
+ */
+ if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) {
+ if (cgroup_reclaim(sc) && writeback_throttling_sane(sc))
+ set_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags);
+
+ if (current_is_kswapd())
+ set_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags);
+ }
+
+ /*
+ * Stall direct reclaim for IO completions if the lruvec is
+ * node is congested. Allow kswapd to continue until it
+ * starts encountering unqueued dirty pages or cycling through
+ * the LRU too quickly.
+ */
+ if (!current_is_kswapd() && current_may_throttle() &&
+ !sc->hibernation_mode &&
+ (test_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags) ||
+ test_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags)))
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
+
+ if (should_continue_reclaim(pgdat, nr_node_reclaimed, sc))
+ goto again;
+
+ /*
+ * 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;
+}
+
+/*
+ * 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;
+
+ /* Allocation can already succeed, nothing to do */
+ if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
+ sc->reclaim_idx, 0))
+ return true;
+
+ /* Compaction cannot yet proceed. Do reclaim. */
+ if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
+ 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);
+}
+
+static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
+{
+ /*
+ * If reclaim is making progress greater than 12% efficiency then
+ * wake all the NOPROGRESS throttled tasks.
+ */
+ if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
+ wait_queue_head_t *wqh;
+
+ wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
+ if (waitqueue_active(wqh))
+ wake_up(wqh);
+
+ return;
+ }
+
+ /*
+ * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
+ * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
+ * under writeback and marked for immediate reclaim at the tail of the
+ * LRU.
+ */
+ if (current_is_kswapd() || cgroup_reclaim(sc))
+ return;
+
+ /* Throttle if making no progress at high prioities. */
+ if (sc->priority == 1 && !sc->nr_reclaimed)
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
+}
+
+/*
+ * 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;
+ pg_data_t *first_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 (!cgroup_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() */
+ }
+
+ if (!first_pgdat)
+ first_pgdat = zone->zone_pgdat;
+
+ /* 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);
+ }
+
+ if (first_pgdat)
+ consider_reclaim_throttle(first_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 *target_memcg, pg_data_t *pgdat)
+{
+ struct lruvec *target_lruvec;
+ unsigned long refaults;
+
+ if (lru_gen_enabled())
+ return;
+
+ target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
+ refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
+ target_lruvec->refaults[WORKINGSET_ANON] = refaults;
+ refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
+ target_lruvec->refaults[WORKINGSET_FILE] = refaults;
+}
+
+/*
+ * 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 (!cgroup_reclaim(sc))
+ __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
+
+ do {
+ if (!sc->proactive)
+ 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);
+
+ if (cgroup_reclaim(sc)) {
+ struct lruvec *lruvec;
+
+ lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
+ zone->zone_pgdat);
+ clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
+ }
+ }
+
+ 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;
+
+ /*
+ * We make inactive:active ratio decisions based on the node's
+ * composition of memory, but a restrictive reclaim_idx or a
+ * memory.low cgroup setting can exempt large amounts of
+ * memory from reclaim. Neither of which are very common, so
+ * instead of doing costly eligibility calculations of the
+ * entire cgroup subtree up front, we assume the estimates are
+ * good, and retry with forcible deactivation if that fails.
+ */
+ if (sc->skipped_deactivate) {
+ sc->priority = initial_priority;
+ sc->force_deactivate = 1;
+ sc->skipped_deactivate = 0;
+ goto retry;
+ }
+
+ /* Untapped cgroup reserves? Don't OOM, retry. */
+ if (sc->memcg_low_skipped) {
+ sc->priority = initial_priority;
+ sc->force_deactivate = 0;
+ 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_snapshot(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)) {
+ if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
+ WRITE_ONCE(pgdat->kswapd_highest_zoneidx, 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);
+ else
+ /* Throttle until kswapd wakes the process */
+ wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
+ allow_direct_reclaim(pgdat));
+
+ 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;
+
+ set_task_reclaim_state(current, &sc.reclaim_state);
+ trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
+ set_task_reclaim_state(current, NULL);
+
+ return nr_reclaimed;
+}
+
+#ifdef CONFIG_MEMCG
+
+/* Only used by soft limit reclaim. Do not reuse for anything else. */
+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 lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
+ 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,
+ };
+
+ WARN_ON_ONCE(!current->reclaim_state);
+
+ sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
+
+ trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
+ sc.gfp_mask);
+
+ /*
+ * NOTE: Although we can get the priority field, using it
+ * here is not a good idea, since it limits the pages we can scan.
+ * if we don't reclaim here, the shrink_node from balance_pgdat
+ * will pick up pages from other mem cgroup's as well. We hack
+ * the priority and make it zero.
+ */
+ shrink_lruvec(lruvec, &sc);
+
+ 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,
+ unsigned int reclaim_options)
+{
+ unsigned long nr_reclaimed;
+ 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 = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
+ .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
+ };
+ /*
+ * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
+ * equal pressure on all the nodes. This is based on the assumption that
+ * the reclaim does not bail out early.
+ */
+ struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
+
+ set_task_reclaim_state(current, &sc.reclaim_state);
+ trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
+ 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);
+ set_task_reclaim_state(current, NULL);
+
+ return nr_reclaimed;
+}
+#endif
+
+static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
+{
+ struct mem_cgroup *memcg;
+ struct lruvec *lruvec;
+
+ if (lru_gen_enabled()) {
+ lru_gen_age_node(pgdat, sc);
+ return;
+ }
+
+ if (!can_age_anon_pages(pgdat, sc))
+ return;
+
+ lruvec = mem_cgroup_lruvec(NULL, pgdat);
+ if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
+ return;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ lruvec = mem_cgroup_lruvec(memcg, pgdat);
+ shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+ sc, LRU_ACTIVE_ANON);
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
+}
+
+static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
+{
+ int i;
+ struct zone *zone;
+
+ /*
+ * Check for watermark boosts top-down as the higher zones
+ * are more likely to be boosted. Both watermarks and boosts
+ * should not be checked at the same time as reclaim would
+ * start prematurely when there is no boosting and a lower
+ * zone is balanced.
+ */
+ for (i = highest_zoneidx; i >= 0; i--) {
+ zone = pgdat->node_zones + i;
+ if (!managed_zone(zone))
+ continue;
+
+ if (zone->watermark_boost)
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * Returns true if there is an eligible zone balanced for the request order
+ * and highest_zoneidx
+ */
+static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
+{
+ int i;
+ unsigned long mark = -1;
+ struct zone *zone;
+
+ /*
+ * Check watermarks bottom-up as lower zones are more likely to
+ * meet watermarks.
+ */
+ for (i = 0; i <= highest_zoneidx; i++) {
+ zone = pgdat->node_zones + i;
+
+ if (!managed_zone(zone))
+ continue;
+
+ if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
+ mark = wmark_pages(zone, WMARK_PROMO);
+ else
+ mark = high_wmark_pages(zone);
+ if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
+ return true;
+ }
+
+ /*
+ * If a node has no managed zone within highest_zoneidx, 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)
+{
+ struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
+
+ clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags);
+ clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->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 highest_zoneidx)
+{
+ /*
+ * 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, highest_zoneidx)) {
+ 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;
+}
+
+/* Page allocator PCP high watermark is lowered if reclaim is active. */
+static inline void
+update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
+{
+ int i;
+ struct zone *zone;
+
+ for (i = 0; i <= highest_zoneidx; i++) {
+ zone = pgdat->node_zones + i;
+
+ if (!managed_zone(zone))
+ continue;
+
+ if (active)
+ set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
+ else
+ clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
+ }
+}
+
+static inline void
+set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
+{
+ update_reclaim_active(pgdat, highest_zoneidx, true);
+}
+
+static inline void
+clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
+{
+ update_reclaim_active(pgdat, highest_zoneidx, false);
+}
+
+/*
+ * 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 in 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 highest_zoneidx)
+{
+ int i;
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ unsigned long pflags;
+ unsigned long nr_boost_reclaim;
+ unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
+ bool boosted;
+ struct zone *zone;
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .order = order,
+ .may_unmap = 1,
+ };
+
+ set_task_reclaim_state(current, &sc.reclaim_state);
+ psi_memstall_enter(&pflags);
+ __fs_reclaim_acquire(_THIS_IP_);
+
+ count_vm_event(PAGEOUTRUN);
+
+ /*
+ * Account for the reclaim boost. Note that the zone boost is left in
+ * place so that parallel allocations that are near the watermark will
+ * stall or direct reclaim until kswapd is finished.
+ */
+ nr_boost_reclaim = 0;
+ for (i = 0; i <= highest_zoneidx; i++) {
+ zone = pgdat->node_zones + i;
+ if (!managed_zone(zone))
+ continue;
+
+ nr_boost_reclaim += zone->watermark_boost;
+ zone_boosts[i] = zone->watermark_boost;
+ }
+ boosted = nr_boost_reclaim;
+
+restart:
+ set_reclaim_active(pgdat, highest_zoneidx);
+ sc.priority = DEF_PRIORITY;
+ do {
+ unsigned long nr_reclaimed = sc.nr_reclaimed;
+ bool raise_priority = true;
+ bool balanced;
+ bool ret;
+
+ sc.reclaim_idx = highest_zoneidx;
+
+ /*
+ * 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;
+ }
+ }
+
+ /*
+ * If the pgdat is imbalanced then ignore boosting and preserve
+ * the watermarks for a later time and restart. Note that the
+ * zone watermarks will be still reset at the end of balancing
+ * on the grounds that the normal reclaim should be enough to
+ * re-evaluate if boosting is required when kswapd next wakes.
+ */
+ balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
+ if (!balanced && nr_boost_reclaim) {
+ nr_boost_reclaim = 0;
+ goto restart;
+ }
+
+ /*
+ * If boosting is not active then 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 (!nr_boost_reclaim && balanced)
+ goto out;
+
+ /* Limit the priority of boosting to avoid reclaim writeback */
+ if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
+ raise_priority = false;
+
+ /*
+ * Do not writeback or swap pages for boosted reclaim. The
+ * intent is to relieve pressure not issue sub-optimal IO
+ * from reclaim context. If no pages are reclaimed, the
+ * reclaim will be aborted.
+ */
+ sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
+ sc.may_swap = !nr_boost_reclaim;
+
+ /*
+ * Do some background aging, to give pages a chance to be
+ * referenced before reclaiming. All pages are rotated
+ * regardless of classzone as this is about consistent aging.
+ */
+ kswapd_age_node(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(_THIS_IP_);
+ ret = try_to_freeze();
+ __fs_reclaim_acquire(_THIS_IP_);
+ 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;
+ nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
+
+ /*
+ * If reclaim made no progress for a boost, stop reclaim as
+ * IO cannot be queued and it could be an infinite loop in
+ * extreme circumstances.
+ */
+ if (nr_boost_reclaim && !nr_reclaimed)
+ break;
+
+ if (raise_priority || !nr_reclaimed)
+ sc.priority--;
+ } while (sc.priority >= 1);
+
+ if (!sc.nr_reclaimed)
+ pgdat->kswapd_failures++;
+
+out:
+ clear_reclaim_active(pgdat, highest_zoneidx);
+
+ /* If reclaim was boosted, account for the reclaim done in this pass */
+ if (boosted) {
+ unsigned long flags;
+
+ for (i = 0; i <= highest_zoneidx; i++) {
+ if (!zone_boosts[i])
+ continue;
+
+ /* Increments are under the zone lock */
+ zone = pgdat->node_zones + i;
+ spin_lock_irqsave(&zone->lock, flags);
+ zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
+ spin_unlock_irqrestore(&zone->lock, flags);
+ }
+
+ /*
+ * As there is now likely space, wakeup kcompact to defragment
+ * pageblocks.
+ */
+ wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
+ }
+
+ snapshot_refaults(NULL, pgdat);
+ __fs_reclaim_release(_THIS_IP_);
+ psi_memstall_leave(&pflags);
+ set_task_reclaim_state(current, NULL);
+
+ /*
+ * 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;
+}
+
+/*
+ * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
+ * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
+ * not a valid index then either kswapd runs for first time or kswapd couldn't
+ * sleep after previous reclaim attempt (node is still unbalanced). In that
+ * case return the zone index of the previous kswapd reclaim cycle.
+ */
+static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
+ enum zone_type prev_highest_zoneidx)
+{
+ enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
+
+ return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
+}
+
+static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
+ unsigned int highest_zoneidx)
+{
+ 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, highest_zoneidx)) {
+ /*
+ * 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, highest_zoneidx);
+
+ remaining = schedule_timeout(HZ/10);
+
+ /*
+ * If woken prematurely then reset kswapd_highest_zoneidx and
+ * order. The values will either be from a wakeup request or
+ * the previous request that slept prematurely.
+ */
+ if (remaining) {
+ WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
+ kswapd_highest_zoneidx(pgdat,
+ highest_zoneidx));
+
+ if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
+ WRITE_ONCE(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, highest_zoneidx)) {
+ 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 highest_zoneidx = MAX_NR_ZONES - 1;
+ pg_data_t *pgdat = (pg_data_t *)p;
+ struct task_struct *tsk = current;
+ const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
+
+ if (!cpumask_empty(cpumask))
+ set_cpus_allowed_ptr(tsk, cpumask);
+
+ /*
+ * 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_KSWAPD;
+ set_freezable();
+
+ WRITE_ONCE(pgdat->kswapd_order, 0);
+ WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
+ atomic_set(&pgdat->nr_writeback_throttled, 0);
+ for ( ; ; ) {
+ bool ret;
+
+ alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
+ highest_zoneidx = kswapd_highest_zoneidx(pgdat,
+ highest_zoneidx);
+
+kswapd_try_sleep:
+ kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
+ highest_zoneidx);
+
+ /* Read the new order and highest_zoneidx */
+ alloc_order = READ_ONCE(pgdat->kswapd_order);
+ highest_zoneidx = kswapd_highest_zoneidx(pgdat,
+ highest_zoneidx);
+ WRITE_ONCE(pgdat->kswapd_order, 0);
+ WRITE_ONCE(pgdat->kswapd_highest_zoneidx, 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, highest_zoneidx,
+ alloc_order);
+ reclaim_order = balance_pgdat(pgdat, alloc_order,
+ highest_zoneidx);
+ if (reclaim_order < alloc_order)
+ goto kswapd_try_sleep;
+ }
+
+ tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
+
+ 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 highest_zoneidx)
+{
+ pg_data_t *pgdat;
+ enum zone_type curr_idx;
+
+ if (!managed_zone(zone))
+ return;
+
+ if (!cpuset_zone_allowed(zone, gfp_flags))
+ return;
+
+ pgdat = zone->zone_pgdat;
+ curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
+
+ if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
+ WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
+
+ if (READ_ONCE(pgdat->kswapd_order) < order)
+ WRITE_ONCE(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, highest_zoneidx) &&
+ !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
+ /*
+ * 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, highest_zoneidx);
+ return;
+ }
+
+ trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, 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 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);
+ unsigned long nr_reclaimed;
+ unsigned int noreclaim_flag;
+
+ fs_reclaim_acquire(sc.gfp_mask);
+ noreclaim_flag = memalloc_noreclaim_save();
+ set_task_reclaim_state(current, &sc.reclaim_state);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ set_task_reclaim_state(current, NULL);
+ memalloc_noreclaim_restore(noreclaim_flag);
+ fs_reclaim_release(sc.gfp_mask);
+
+ return nr_reclaimed;
+}
+#endif /* CONFIG_HIBERNATION */
+
+/*
+ * This kswapd start function will be called by init and node-hot-add.
+ */
+void __meminit kswapd_run(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+
+ pgdat_kswapd_lock(pgdat);
+ if (!pgdat->kswapd) {
+ 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);
+ pgdat->kswapd = NULL;
+ }
+ }
+ pgdat_kswapd_unlock(pgdat);
+}
+
+/*
+ * Called by memory hotplug when all memory in a node is offlined. Caller must
+ * be holding mem_hotplug_begin/done().
+ */
+void __meminit kswapd_stop(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+ struct task_struct *kswapd;
+
+ pgdat_kswapd_lock(pgdat);
+ kswapd = pgdat->kswapd;
+ if (kswapd) {
+ kthread_stop(kswapd);
+ pgdat->kswapd = NULL;
+ }
+ pgdat_kswapd_unlock(pgdat);
+}
+
+static int __init kswapd_init(void)
+{
+ int nid;
+
+ swap_setup();
+ for_each_node_state(nid, N_MEMORY)
+ kswapd_run(nid);
+ 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;
+
+/*
+ * 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;
+ 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),
+ };
+ unsigned long pflags;
+
+ trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
+ sc.gfp_mask);
+
+ cond_resched();
+ psi_memstall_enter(&pflags);
+ fs_reclaim_acquire(sc.gfp_mask);
+ /*
+ * We need to be able to allocate from the reserves for RECLAIM_UNMAP
+ */
+ noreclaim_flag = memalloc_noreclaim_save();
+ set_task_reclaim_state(p, &sc.reclaim_state);
+
+ if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
+ node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_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);
+ }
+
+ set_task_reclaim_state(p, NULL);
+ memalloc_noreclaim_restore(noreclaim_flag);
+ fs_reclaim_release(sc.gfp_mask);
+ psi_memstall_leave(&pflags);
+
+ trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
+
+ 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_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
+ 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
+
+/**
+ * check_move_unevictable_folios - Move evictable folios to appropriate zone
+ * lru list
+ * @fbatch: Batch of lru folios to check.
+ *
+ * Checks folios for evictability, if an evictable folio is in the unevictable
+ * lru list, moves it to the appropriate evictable lru list. This function
+ * should be only used for lru folios.
+ */
+void check_move_unevictable_folios(struct folio_batch *fbatch)
+{
+ struct lruvec *lruvec = NULL;
+ int pgscanned = 0;
+ int pgrescued = 0;
+ int i;
+
+ for (i = 0; i < fbatch->nr; i++) {
+ struct folio *folio = fbatch->folios[i];
+ int nr_pages = folio_nr_pages(folio);
+
+ pgscanned += nr_pages;
+
+ /* block memcg migration while the folio moves between lrus */
+ if (!folio_test_clear_lru(folio))
+ continue;
+
+ lruvec = folio_lruvec_relock_irq(folio, lruvec);
+ if (folio_evictable(folio) && folio_test_unevictable(folio)) {
+ lruvec_del_folio(lruvec, folio);
+ folio_clear_unevictable(folio);
+ lruvec_add_folio(lruvec, folio);
+ pgrescued += nr_pages;
+ }
+ folio_set_lru(folio);
+ }
+
+ if (lruvec) {
+ __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
+ __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+ unlock_page_lruvec_irq(lruvec);
+ } else if (pgscanned) {
+ count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+ }
+}
+EXPORT_SYMBOL_GPL(check_move_unevictable_folios);