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Diffstat (limited to '')
| -rw-r--r-- | mm/vmscan.c | 8183 |
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); |