[openwrt/staging/rmilecki.git] /

From 8ee8571e47aa75221e5fbd4c9c7802fc4244c346 Mon Sep 17 00:00:00 2001
From: Yu Zhao <yuzhao@google.com>
Date: Wed, 21 Dec 2022 21:19:04 -0700
Subject: [PATCH 06/19] BACKPORT: mm: multi-gen LRU: per-node lru_gen_folio
 lists

For each node, memcgs are divided into two generations: the old and
the young. For each generation, memcgs are randomly sharded into
multiple bins to improve scalability. For each bin, an RCU hlist_nulls
is virtually divided into three segments: the head, the tail and the
default.

An onlining memcg is added to the tail of a random bin in the old
generation. The eviction starts at the head of a random bin in the old
generation. The per-node memcg generation counter, whose reminder (mod
2) indexes the old generation, is incremented when all its bins become
empty.

There are four operations:
1. MEMCG_LRU_HEAD, which moves an memcg to the head of a random bin in
   its current generation (old or young) and updates its "seg" to
   "head";
2. MEMCG_LRU_TAIL, which moves an memcg to the tail of a random bin in
   its current generation (old or young) and updates its "seg" to
   "tail";
3. MEMCG_LRU_OLD, which moves an memcg to the head of a random bin in
   the old generation, updates its "gen" to "old" and resets its "seg"
   to "default";
4. MEMCG_LRU_YOUNG, which moves an memcg to the tail of a random bin
   in the young generation, updates its "gen" to "young" and resets
   its "seg" to "default".

The events that trigger the above operations are:
1. Exceeding the soft limit, which triggers MEMCG_LRU_HEAD;
2. The first attempt to reclaim an memcg below low, which triggers
   MEMCG_LRU_TAIL;
3. The first attempt to reclaim an memcg below reclaimable size
   threshold, which triggers MEMCG_LRU_TAIL;
4. The second attempt to reclaim an memcg below reclaimable size
   threshold, which triggers MEMCG_LRU_YOUNG;
5. Attempting to reclaim an memcg below min, which triggers
   MEMCG_LRU_YOUNG;
6. Finishing the aging on the eviction path, which triggers
   MEMCG_LRU_YOUNG;
7. Offlining an memcg, which triggers MEMCG_LRU_OLD.

Note that memcg LRU only applies to global reclaim, and the
round-robin incrementing of their max_seq counters ensures the
eventual fairness to all eligible memcgs. For memcg reclaim, it still
relies on mem_cgroup_iter().

Link: https://lkml.kernel.org/r/20221222041905.2431096-7-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bug: 274865848
(cherry picked from commit e4dde56cd208674ce899b47589f263499e5b8cdc)
[TJ: Resolved conflicts with older function signatures for
min_cgroup_below_min / min_cgroup_below_low and includes]
Change-Id: Idc8a0f635e035d72dd911f807d1224cb47cbd655
Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
 include/linux/memcontrol.h |  10 +
 include/linux/mm_inline.h  |  17 ++
 include/linux/mmzone.h     | 117 +++++++++++-
 mm/memcontrol.c            |  16 ++
 mm/page_alloc.c            |   1 +
 mm/vmscan.c                | 374 +++++++++++++++++++++++++++++++++----
 6 files changed, 500 insertions(+), 35 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e039763029563..82d28b052a9e5 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -790,6 +790,11 @@ static inline void obj_cgroup_put(struct obj_cgroup *objcg)
        percpu_ref_put(&objcg->refcnt);
 }
 
+static inline bool mem_cgroup_tryget(struct mem_cgroup *memcg)
+{
+       return !memcg || css_tryget(&memcg->css);
+}
+
 static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
        if (memcg)
@@ -1290,6 +1295,11 @@ static inline void obj_cgroup_put(struct obj_cgroup *objcg)
 {
 }
 
+static inline bool mem_cgroup_tryget(struct mem_cgroup *memcg)
+{
+       return true;
+}
+
 static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
 }
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index da38e3d962e2f..c1fd3922dc5dd 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -122,6 +122,18 @@ static inline bool lru_gen_in_fault(void)
        return current->in_lru_fault;
 }
 
+#ifdef CONFIG_MEMCG
+static inline int lru_gen_memcg_seg(struct lruvec *lruvec)
+{
+       return READ_ONCE(lruvec->lrugen.seg);
+}
+#else
+static inline int lru_gen_memcg_seg(struct lruvec *lruvec)
+{
+       return 0;
+}
+#endif
+
 static inline int lru_gen_from_seq(unsigned long seq)
 {
        return seq % MAX_NR_GENS;
@@ -297,6 +309,11 @@ static inline bool lru_gen_in_fault(void)
        return false;
 }
 
+static inline int lru_gen_memcg_seg(struct lruvec *lruvec)
+{
+       return 0;
+}
+
 static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
 {
        return false;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 02e4323744715..66e067a635682 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -7,6 +7,7 @@
 
 #include <linux/spinlock.h>
 #include <linux/list.h>
+#include <linux/list_nulls.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/cache.h>
@@ -367,6 +368,15 @@ struct page_vma_mapped_walk;
 #define LRU_GEN_MASK           ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF)
 #define LRU_REFS_MASK          ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF)
 
+/* 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_LRU_GEN
 
 enum {
@@ -426,6 +436,14 @@ struct lru_gen_folio {
        atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS];
        /* whether the multi-gen LRU is enabled */
        bool enabled;
+#ifdef CONFIG_MEMCG
+       /* the memcg generation this lru_gen_folio belongs to */
+       u8 gen;
+       /* the list segment this lru_gen_folio belongs to */
+       u8 seg;
+       /* per-node lru_gen_folio list for global reclaim */
+       struct hlist_nulls_node list;
+#endif
 };
 
 enum {
@@ -479,12 +497,87 @@ void lru_gen_init_lruvec(struct lruvec *lruvec);
 void lru_gen_look_around(struct page_vma_mapped_walk *pvmw);
 
 #ifdef CONFIG_MEMCG
+
+/*
+ * For each node, memcgs are divided into two generations: the old and the
+ * young. For each generation, memcgs are randomly sharded into multiple bins
+ * to improve scalability. For each bin, the hlist_nulls is virtually divided
+ * into three segments: the head, the tail and the default.
+ *
+ * An onlining memcg is added to the tail of a random bin in the old generation.
+ * The eviction starts at the head of a random bin in the old generation. The
+ * per-node memcg generation counter, whose reminder (mod MEMCG_NR_GENS) indexes
+ * the old generation, is incremented when all its bins become empty.
+ *
+ * There are four operations:
+ * 1. MEMCG_LRU_HEAD, which moves an memcg to the head of a random bin in its
+ *    current generation (old or young) and updates its "seg" to "head";
+ * 2. MEMCG_LRU_TAIL, which moves an memcg to the tail of a random bin in its
+ *    current generation (old or young) and updates its "seg" to "tail";
+ * 3. MEMCG_LRU_OLD, which moves an memcg to the head of a random bin in the old
+ *    generation, updates its "gen" to "old" and resets its "seg" to "default";
+ * 4. MEMCG_LRU_YOUNG, which moves an memcg to the tail of a random bin in the
+ *    young generation, updates its "gen" to "young" and resets its "seg" to
+ *    "default".
+ *
+ * The events that trigger the above operations are:
+ * 1. Exceeding the soft limit, which triggers MEMCG_LRU_HEAD;
+ * 2. The first attempt to reclaim an memcg below low, which triggers
+ *    MEMCG_LRU_TAIL;
+ * 3. The first attempt to reclaim an memcg below reclaimable size threshold,
+ *    which triggers MEMCG_LRU_TAIL;
+ * 4. The second attempt to reclaim an memcg below reclaimable size threshold,
+ *    which triggers MEMCG_LRU_YOUNG;
+ * 5. Attempting to reclaim an memcg below min, which triggers MEMCG_LRU_YOUNG;
+ * 6. Finishing the aging on the eviction path, which triggers MEMCG_LRU_YOUNG;
+ * 7. Offlining an memcg, which triggers MEMCG_LRU_OLD.
+ *
+ * Note that memcg LRU only applies to global reclaim, and the round-robin
+ * incrementing of their max_seq counters ensures the eventual fairness to all
+ * eligible memcgs. For memcg reclaim, it still relies on mem_cgroup_iter().
+ */
+#define MEMCG_NR_GENS  2
+#define MEMCG_NR_BINS  8
+
+struct lru_gen_memcg {
+       /* the per-node memcg generation counter */
+       unsigned long seq;
+       /* each memcg has one lru_gen_folio per node */
+       unsigned long nr_memcgs[MEMCG_NR_GENS];
+       /* per-node lru_gen_folio list for global reclaim */
+       struct hlist_nulls_head fifo[MEMCG_NR_GENS][MEMCG_NR_BINS];
+       /* protects the above */
+       spinlock_t lock;
+};
+
+void lru_gen_init_pgdat(struct pglist_data *pgdat);
+
 void lru_gen_init_memcg(struct mem_cgroup *memcg);
 void lru_gen_exit_memcg(struct mem_cgroup *memcg);
-#endif
+void lru_gen_online_memcg(struct mem_cgroup *memcg);
+void lru_gen_offline_memcg(struct mem_cgroup *memcg);
+void lru_gen_release_memcg(struct mem_cgroup *memcg);
+void lru_gen_rotate_memcg(struct lruvec *lruvec, int op);
+
+#else /* !CONFIG_MEMCG */
+
+#define MEMCG_NR_GENS  1
+
+struct lru_gen_memcg {
+};
+
+static inline void lru_gen_init_pgdat(struct pglist_data *pgdat)
+{
+}
+
+#endif /* CONFIG_MEMCG */
 
 #else /* !CONFIG_LRU_GEN */
 
+static inline void lru_gen_init_pgdat(struct pglist_data *pgdat)
+{
+}
+
 static inline void lru_gen_init_lruvec(struct lruvec *lruvec)
 {
 }
@@ -494,6 +587,7 @@ static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
 }
 
 #ifdef CONFIG_MEMCG
+
 static inline void lru_gen_init_memcg(struct mem_cgroup *memcg)
 {
 }
@@ -501,7 +595,24 @@ static inline void lru_gen_init_memcg(struct mem_cgroup *memcg)
 static inline void lru_gen_exit_memcg(struct mem_cgroup *memcg)
 {
 }
-#endif
+
+static inline void lru_gen_online_memcg(struct mem_cgroup *memcg)
+{
+}
+
+static inline void lru_gen_offline_memcg(struct mem_cgroup *memcg)
+{
+}
+
+static inline void lru_gen_release_memcg(struct mem_cgroup *memcg)
+{
+}
+
+static inline void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
+{
+}
+
+#endif /* CONFIG_MEMCG */
 
 #endif /* CONFIG_LRU_GEN */
 
@@ -1219,6 +1330,8 @@ typedef struct pglist_data {
 #ifdef CONFIG_LRU_GEN
        /* kswap mm walk data */
        struct lru_gen_mm_walk  mm_walk;
+       /* lru_gen_folio list */
+       struct lru_gen_memcg memcg_lru;
 #endif
 
        CACHELINE_PADDING(_pad2_);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3e8f1ad0fe9db..7815d556e38cc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -477,6 +477,16 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
        struct mem_cgroup_per_node *mz;
        struct mem_cgroup_tree_per_node *mctz;
 
+       if (lru_gen_enabled()) {
+               struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
+
+               /* see the comment on MEMCG_NR_GENS */
+               if (soft_limit_excess(memcg) && lru_gen_memcg_seg(lruvec) != MEMCG_LRU_HEAD)
+                       lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);
+
+               return;
+       }
+
        mctz = soft_limit_tree.rb_tree_per_node[nid];
        if (!mctz)
                return;
@@ -3522,6 +3532,9 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
        struct mem_cgroup_tree_per_node *mctz;
        unsigned long excess;
 
+       if (lru_gen_enabled())
+               return 0;
+
        if (order > 0)
                return 0;
 
@@ -5382,6 +5395,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
        if (unlikely(mem_cgroup_is_root(memcg)))
                queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
                                   2UL*HZ);
+       lru_gen_online_memcg(memcg);
        return 0;
 offline_kmem:
        memcg_offline_kmem(memcg);
@@ -5413,6 +5427,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
        memcg_offline_kmem(memcg);
        reparent_shrinker_deferred(memcg);
        wb_memcg_offline(memcg);
+       lru_gen_offline_memcg(memcg);
 
        drain_all_stock(memcg);
 
@@ -5424,6 +5439,7 @@ static void mem_cgroup_css_released(struct cgroup_subsys_state *css)
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
        invalidate_reclaim_iterators(memcg);
+       lru_gen_release_memcg(memcg);
 }
 
 static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 69668817fed37..473057b81a9df 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7957,6 +7957,7 @@ static void __init free_area_init_node(int nid)
        pgdat_set_deferred_range(pgdat);
 
        free_area_init_core(pgdat);
+       lru_gen_init_pgdat(pgdat);
 }
 
 static void __init free_area_init_memoryless_node(int nid)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0c47952714b26..65eb28448f216 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -54,6 +54,8 @@
 #include <linux/shmem_fs.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
+#include <linux/rculist_nulls.h>
+#include <linux/random.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -134,11 +136,6 @@ struct scan_control {
        /* Always discard instead of demoting to lower tier memory */
        unsigned int no_demotion:1;
 
-#ifdef CONFIG_LRU_GEN
-       /* help kswapd make better choices among multiple memcgs */
-       unsigned long last_reclaimed;
-#endif
-
        /* Allocation order */
        s8 order;
 
@@ -3160,6 +3157,9 @@ DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
                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);
@@ -4440,8 +4440,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
                if (sc->priority <= DEF_PRIORITY - 2)
                        wait_event_killable(lruvec->mm_state.wait,
                                            max_seq < READ_ONCE(lrugen->max_seq));
-
-               return max_seq < READ_ONCE(lrugen->max_seq);
+               return false;
        }
 
        VM_WARN_ON_ONCE(max_seq != READ_ONCE(lrugen->max_seq));
@@ -4514,8 +4513,6 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
 
        VM_WARN_ON_ONCE(!current_is_kswapd());
 
-       sc->last_reclaimed = sc->nr_reclaimed;
-
        /* check the order to exclude compaction-induced reclaim */
        if (!min_ttl || sc->order || sc->priority == DEF_PRIORITY)
                return;
@@ -5104,8 +5101,7 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
  * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
  *    reclaim.
  */
-static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc,
-                                   bool can_swap)
+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);
@@ -5122,10 +5118,8 @@ static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *
        if (sc->priority == DEF_PRIORITY)
                return nr_to_scan;
 
-       try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false);
-
        /* skip this lruvec as it's low on cold folios */
-       return 0;
+       return try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false) ? -1 : 0;
 }
 
 static unsigned long get_nr_to_reclaim(struct scan_control *sc)
@@ -5134,29 +5128,18 @@ static unsigned long get_nr_to_reclaim(struct scan_control *sc)
        if (!global_reclaim(sc))
                return -1;
 
-       /* discount the previous progress for kswapd */
-       if (current_is_kswapd())
-               return sc->nr_to_reclaim + sc->last_reclaimed;
-
        return max(sc->nr_to_reclaim, compact_gap(sc->order));
 }
 
-static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 {
-       struct blk_plug plug;
+       long nr_to_scan;
        unsigned long scanned = 0;
        unsigned long nr_to_reclaim = get_nr_to_reclaim(sc);
 
-       lru_add_drain();
-
-       blk_start_plug(&plug);
-
-       set_mm_walk(lruvec_pgdat(lruvec));
-
        while (true) {
                int delta;
                int swappiness;
-               unsigned long nr_to_scan;
 
                if (sc->may_swap)
                        swappiness = get_swappiness(lruvec, sc);
@@ -5166,7 +5149,7 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
                        swappiness = 0;
 
                nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness);
-               if (!nr_to_scan)
+               if (nr_to_scan <= 0)
                        break;
 
                delta = evict_folios(lruvec, sc, swappiness);
@@ -5183,11 +5166,252 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
                cond_resched();
        }
 
+       /* whether try_to_inc_max_seq() was successful */
+       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;
+       int seg = lru_gen_memcg_seg(lruvec);
+       struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+       struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+       /* see the comment on MEMCG_NR_GENS */
+       if (!lruvec_is_sizable(lruvec, sc))
+               return seg != MEMCG_LRU_TAIL ? MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
+
+       mem_cgroup_calculate_protection(NULL, memcg);
+
+       if (mem_cgroup_below_min(memcg))
+               return MEMCG_LRU_YOUNG;
+
+       if (mem_cgroup_below_low(memcg)) {
+               /* see the comment on MEMCG_NR_GENS */
+               if (seg != 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);
+
+       sc->nr_reclaimed += current->reclaim_state->reclaimed_slab;
+       current->reclaim_state->reclaimed_slab = 0;
+
+       return success ? MEMCG_LRU_YOUNG : 0;
+}
+
+#ifdef CONFIG_MEMCG
+
+static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
+{
+       int gen;
+       int bin;
+       int first_bin;
+       struct lruvec *lruvec;
+       struct lru_gen_folio *lrugen;
+       const struct hlist_nulls_node *pos;
+       int op = 0;
+       struct mem_cgroup *memcg = NULL;
+       unsigned long nr_to_reclaim = get_nr_to_reclaim(sc);
+
+       bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
+restart:
+       gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
+
+       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);
+
+               mem_cgroup_put(memcg);
+
+               lruvec = container_of(lrugen, struct lruvec, lrugen);
+               memcg = lruvec_memcg(lruvec);
+
+               if (!mem_cgroup_tryget(memcg)) {
+                       op = 0;
+                       memcg = NULL;
+                       continue;
+               }
+
+               rcu_read_unlock();
+
+               op = shrink_one(lruvec, sc);
+
+               if (sc->nr_reclaimed >= nr_to_reclaim)
+                       goto success;
+
+               rcu_read_lock();
+       }
+
+       rcu_read_unlock();
+
+       /* 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;
+success:
+       if (op)
+               lru_gen_rotate_memcg(lruvec, op);
+
+       mem_cgroup_put(memcg);
+}
+
+static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+{
+       struct blk_plug plug;
+
+       VM_WARN_ON_ONCE(global_reclaim(sc));
+
+       lru_add_drain();
+
+       blk_start_plug(&plug);
+
+       set_mm_walk(lruvec_pgdat(lruvec));
+
+       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 / MEMCG_NR_GENS) >>
+        * priority) * reclaimed_to_scanned_ratio = nr_to_reclaim, where the
+        * estimated 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);
+
+       reclaimable /= MEMCG_NR_GENS;
+
+       /* 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(!global_reclaim(sc));
+
+       lru_add_drain();
+
+       blk_start_plug(&plug);
+
+       set_mm_walk(pgdat);
+
+       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);
+
+       /* kswapd should never fail */
+       pgdat->kswapd_failures = 0;
+}
+
+#ifdef CONFIG_MEMCG
+void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
+{
+       int seg;
+       int old, new;
+       int bin = get_random_u32_below(MEMCG_NR_BINS);
+       struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+
+       spin_lock(&pgdat->memcg_lru.lock);
+
+       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);
+
+       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]++;
+
+       lruvec->lrugen.gen = new;
+       WRITE_ONCE(lruvec->lrugen.seg, seg);
+
+       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(&pgdat->memcg_lru.lock);
+}
+#endif
+
 /******************************************************************************
  *                          state change
  ******************************************************************************/
@@ -5644,11 +5868,11 @@ static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
 
        if (!mem_cgroup_disabled()) {
                rcu_read_lock();
+
                memcg = mem_cgroup_from_id(memcg_id);
-#ifdef CONFIG_MEMCG
-               if (memcg && !css_tryget(&memcg->css))
+               if (!mem_cgroup_tryget(memcg))
                        memcg = NULL;
-#endif
+
                rcu_read_unlock();
 
                if (!memcg)
@@ -5796,6 +6020,19 @@ void lru_gen_init_lruvec(struct lruvec *lruvec)
 }
 
 #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);
@@ -5819,7 +6056,69 @@ void lru_gen_exit_memcg(struct mem_cgroup *memcg)
                }
        }
 }
-#endif
+
+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(&pgdat->memcg_lru.lock);
+
+               VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
+
+               gen = get_memcg_gen(pgdat->memcg_lru.seq);
+
+               hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]);
+               pgdat->memcg_lru.nr_memcgs[gen]++;
+
+               lruvec->lrugen.gen = gen;
+
+               spin_unlock(&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(&pgdat->memcg_lru.lock);
+
+               VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
+
+               gen = lruvec->lrugen.gen;
+
+               hlist_nulls_del_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);
+
+               spin_unlock(&pgdat->memcg_lru.lock);
+       }
+}
+
+#endif /* CONFIG_MEMCG */
 
 static int __init init_lru_gen(void)
 {
@@ -5846,6 +6145,10 @@ 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)
@@ -5859,7 +6162,7 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
        bool proportional_reclaim;
        struct blk_plug plug;
 
-       if (lru_gen_enabled()) {
+       if (lru_gen_enabled() && !global_reclaim(sc)) {
                lru_gen_shrink_lruvec(lruvec, sc);
                return;
        }
@@ -6102,6 +6405,11 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
        struct lruvec *target_lruvec;
        bool reclaimable = false;
 
+       if (lru_gen_enabled() && global_reclaim(sc)) {
+               lru_gen_shrink_node(pgdat, sc);
+               return;
+       }
+
        target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
 
 again:
-- 
2.40.1