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Diffstat (limited to 'mm/swap.c')
| -rw-r--r-- | mm/swap.c | 1104 |
1 files changed, 1104 insertions, 0 deletions
diff --git a/mm/swap.c b/mm/swap.c new file mode 100644 index 000000000..cd8f0150b --- /dev/null +++ b/mm/swap.c @@ -0,0 +1,1104 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/mm/swap.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + */ + +/* + * This file contains the default values for the operation of the + * Linux VM subsystem. Fine-tuning documentation can be found in + * Documentation/admin-guide/sysctl/vm.rst. + * Started 18.12.91 + * Swap aging added 23.2.95, Stephen Tweedie. + * Buffermem limits added 12.3.98, Rik van Riel. + */ + +#include <linux/mm.h> +#include <linux/sched.h> +#include <linux/kernel_stat.h> +#include <linux/swap.h> +#include <linux/mman.h> +#include <linux/pagemap.h> +#include <linux/pagevec.h> +#include <linux/init.h> +#include <linux/export.h> +#include <linux/mm_inline.h> +#include <linux/percpu_counter.h> +#include <linux/memremap.h> +#include <linux/percpu.h> +#include <linux/cpu.h> +#include <linux/notifier.h> +#include <linux/backing-dev.h> +#include <linux/memcontrol.h> +#include <linux/gfp.h> +#include <linux/uio.h> +#include <linux/hugetlb.h> +#include <linux/page_idle.h> +#include <linux/local_lock.h> +#include <linux/buffer_head.h> + +#include "internal.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/pagemap.h> + +/* How many pages do we try to swap or page in/out together? As a power of 2 */ +int page_cluster; +const int page_cluster_max = 31; + +/* Protecting only lru_rotate.fbatch which requires disabling interrupts */ +struct lru_rotate { + local_lock_t lock; + struct folio_batch fbatch; +}; +static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = { + .lock = INIT_LOCAL_LOCK(lock), +}; + +/* + * The following folio batches are grouped together because they are protected + * by disabling preemption (and interrupts remain enabled). + */ +struct cpu_fbatches { + local_lock_t lock; + struct folio_batch lru_add; + struct folio_batch lru_deactivate_file; + struct folio_batch lru_deactivate; + struct folio_batch lru_lazyfree; +#ifdef CONFIG_SMP + struct folio_batch activate; +#endif +}; +static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = { + .lock = INIT_LOCAL_LOCK(lock), +}; + +/* + * This path almost never happens for VM activity - pages are normally freed + * in batches. But it gets used by networking - and for compound pages. + */ +static void __page_cache_release(struct folio *folio) +{ + if (folio_test_lru(folio)) { + struct lruvec *lruvec; + unsigned long flags; + + lruvec = folio_lruvec_lock_irqsave(folio, &flags); + lruvec_del_folio(lruvec, folio); + __folio_clear_lru_flags(folio); + unlock_page_lruvec_irqrestore(lruvec, flags); + } + /* See comment on folio_test_mlocked in release_pages() */ + if (unlikely(folio_test_mlocked(folio))) { + long nr_pages = folio_nr_pages(folio); + + __folio_clear_mlocked(folio); + zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages); + count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages); + } +} + +static void __folio_put_small(struct folio *folio) +{ + __page_cache_release(folio); + mem_cgroup_uncharge(folio); + free_unref_page(&folio->page, 0); +} + +static void __folio_put_large(struct folio *folio) +{ + /* + * __page_cache_release() is supposed to be called for thp, not for + * hugetlb. This is because hugetlb page does never have PageLRU set + * (it's never listed to any LRU lists) and no memcg routines should + * be called for hugetlb (it has a separate hugetlb_cgroup.) + */ + if (!folio_test_hugetlb(folio)) + __page_cache_release(folio); + destroy_large_folio(folio); +} + +void __folio_put(struct folio *folio) +{ + if (unlikely(folio_is_zone_device(folio))) + free_zone_device_page(&folio->page); + else if (unlikely(folio_test_large(folio))) + __folio_put_large(folio); + else + __folio_put_small(folio); +} +EXPORT_SYMBOL(__folio_put); + +/** + * put_pages_list() - release a list of pages + * @pages: list of pages threaded on page->lru + * + * Release a list of pages which are strung together on page.lru. + */ +void put_pages_list(struct list_head *pages) +{ + struct folio *folio, *next; + + list_for_each_entry_safe(folio, next, pages, lru) { + if (!folio_put_testzero(folio)) { + list_del(&folio->lru); + continue; + } + if (folio_test_large(folio)) { + list_del(&folio->lru); + __folio_put_large(folio); + continue; + } + /* LRU flag must be clear because it's passed using the lru */ + } + + free_unref_page_list(pages); + INIT_LIST_HEAD(pages); +} +EXPORT_SYMBOL(put_pages_list); + +typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio); + +static void lru_add_fn(struct lruvec *lruvec, struct folio *folio) +{ + int was_unevictable = folio_test_clear_unevictable(folio); + long nr_pages = folio_nr_pages(folio); + + VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + + /* + * Is an smp_mb__after_atomic() still required here, before + * folio_evictable() tests the mlocked flag, to rule out the possibility + * of stranding an evictable folio on an unevictable LRU? I think + * not, because __munlock_folio() only clears the mlocked flag + * while the LRU lock is held. + * + * (That is not true of __page_cache_release(), and not necessarily + * true of release_pages(): but those only clear the mlocked flag after + * folio_put_testzero() has excluded any other users of the folio.) + */ + if (folio_evictable(folio)) { + if (was_unevictable) + __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages); + } else { + folio_clear_active(folio); + folio_set_unevictable(folio); + /* + * folio->mlock_count = !!folio_test_mlocked(folio)? + * But that leaves __mlock_folio() in doubt whether another + * actor has already counted the mlock or not. Err on the + * safe side, underestimate, let page reclaim fix it, rather + * than leaving a page on the unevictable LRU indefinitely. + */ + folio->mlock_count = 0; + if (!was_unevictable) + __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages); + } + + lruvec_add_folio(lruvec, folio); + trace_mm_lru_insertion(folio); +} + +static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn) +{ + int i; + struct lruvec *lruvec = NULL; + unsigned long flags = 0; + + for (i = 0; i < folio_batch_count(fbatch); i++) { + struct folio *folio = fbatch->folios[i]; + + /* block memcg migration while the folio moves between lru */ + if (move_fn != lru_add_fn && !folio_test_clear_lru(folio)) + continue; + + lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags); + move_fn(lruvec, folio); + + folio_set_lru(folio); + } + + if (lruvec) + unlock_page_lruvec_irqrestore(lruvec, flags); + folios_put(fbatch->folios, folio_batch_count(fbatch)); + folio_batch_reinit(fbatch); +} + +static void folio_batch_add_and_move(struct folio_batch *fbatch, + struct folio *folio, move_fn_t move_fn) +{ + if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) && + !lru_cache_disabled()) + return; + folio_batch_move_lru(fbatch, move_fn); +} + +static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio) +{ + if (!folio_test_unevictable(folio)) { + lruvec_del_folio(lruvec, folio); + folio_clear_active(folio); + lruvec_add_folio_tail(lruvec, folio); + __count_vm_events(PGROTATED, folio_nr_pages(folio)); + } +} + +/* + * Writeback is about to end against a folio which has been marked for + * immediate reclaim. If it still appears to be reclaimable, move it + * to the tail of the inactive list. + * + * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races. + */ +void folio_rotate_reclaimable(struct folio *folio) +{ + if (!folio_test_locked(folio) && !folio_test_dirty(folio) && + !folio_test_unevictable(folio) && folio_test_lru(folio)) { + struct folio_batch *fbatch; + unsigned long flags; + + folio_get(folio); + local_lock_irqsave(&lru_rotate.lock, flags); + fbatch = this_cpu_ptr(&lru_rotate.fbatch); + folio_batch_add_and_move(fbatch, folio, lru_move_tail_fn); + local_unlock_irqrestore(&lru_rotate.lock, flags); + } +} + +void lru_note_cost(struct lruvec *lruvec, bool file, + unsigned int nr_io, unsigned int nr_rotated) +{ + unsigned long cost; + + /* + * Reflect the relative cost of incurring IO and spending CPU + * time on rotations. This doesn't attempt to make a precise + * comparison, it just says: if reloads are about comparable + * between the LRU lists, or rotations are overwhelmingly + * different between them, adjust scan balance for CPU work. + */ + cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated; + + do { + unsigned long lrusize; + + /* + * Hold lruvec->lru_lock is safe here, since + * 1) The pinned lruvec in reclaim, or + * 2) From a pre-LRU page during refault (which also holds the + * rcu lock, so would be safe even if the page was on the LRU + * and could move simultaneously to a new lruvec). + */ + spin_lock_irq(&lruvec->lru_lock); + /* Record cost event */ + if (file) + lruvec->file_cost += cost; + else + lruvec->anon_cost += cost; + + /* + * Decay previous events + * + * Because workloads change over time (and to avoid + * overflow) we keep these statistics as a floating + * average, which ends up weighing recent refaults + * more than old ones. + */ + lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) + + lruvec_page_state(lruvec, NR_ACTIVE_ANON) + + lruvec_page_state(lruvec, NR_INACTIVE_FILE) + + lruvec_page_state(lruvec, NR_ACTIVE_FILE); + + if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) { + lruvec->file_cost /= 2; + lruvec->anon_cost /= 2; + } + spin_unlock_irq(&lruvec->lru_lock); + } while ((lruvec = parent_lruvec(lruvec))); +} + +void lru_note_cost_refault(struct folio *folio) +{ + lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio), + folio_nr_pages(folio), 0); +} + +static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio) +{ + if (!folio_test_active(folio) && !folio_test_unevictable(folio)) { + long nr_pages = folio_nr_pages(folio); + + lruvec_del_folio(lruvec, folio); + folio_set_active(folio); + lruvec_add_folio(lruvec, folio); + trace_mm_lru_activate(folio); + + __count_vm_events(PGACTIVATE, nr_pages); + __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE, + nr_pages); + } +} + +#ifdef CONFIG_SMP +static void folio_activate_drain(int cpu) +{ + struct folio_batch *fbatch = &per_cpu(cpu_fbatches.activate, cpu); + + if (folio_batch_count(fbatch)) + folio_batch_move_lru(fbatch, folio_activate_fn); +} + +void folio_activate(struct folio *folio) +{ + if (folio_test_lru(folio) && !folio_test_active(folio) && + !folio_test_unevictable(folio)) { + struct folio_batch *fbatch; + + folio_get(folio); + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.activate); + folio_batch_add_and_move(fbatch, folio, folio_activate_fn); + local_unlock(&cpu_fbatches.lock); + } +} + +#else +static inline void folio_activate_drain(int cpu) +{ +} + +void folio_activate(struct folio *folio) +{ + struct lruvec *lruvec; + + if (folio_test_clear_lru(folio)) { + lruvec = folio_lruvec_lock_irq(folio); + folio_activate_fn(lruvec, folio); + unlock_page_lruvec_irq(lruvec); + folio_set_lru(folio); + } +} +#endif + +static void __lru_cache_activate_folio(struct folio *folio) +{ + struct folio_batch *fbatch; + int i; + + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.lru_add); + + /* + * Search backwards on the optimistic assumption that the folio being + * activated has just been added to this batch. Note that only + * the local batch is examined as a !LRU folio could be in the + * process of being released, reclaimed, migrated or on a remote + * batch that is currently being drained. Furthermore, marking + * a remote batch's folio active potentially hits a race where + * a folio is marked active just after it is added to the inactive + * list causing accounting errors and BUG_ON checks to trigger. + */ + for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) { + struct folio *batch_folio = fbatch->folios[i]; + + if (batch_folio == folio) { + folio_set_active(folio); + break; + } + } + + local_unlock(&cpu_fbatches.lock); +} + +#ifdef CONFIG_LRU_GEN +static void folio_inc_refs(struct folio *folio) +{ + unsigned long new_flags, old_flags = READ_ONCE(folio->flags); + + if (folio_test_unevictable(folio)) + return; + + if (!folio_test_referenced(folio)) { + folio_set_referenced(folio); + return; + } + + if (!folio_test_workingset(folio)) { + folio_set_workingset(folio); + return; + } + + /* see the comment on MAX_NR_TIERS */ + do { + new_flags = old_flags & LRU_REFS_MASK; + if (new_flags == LRU_REFS_MASK) + break; + + new_flags += BIT(LRU_REFS_PGOFF); + new_flags |= old_flags & ~LRU_REFS_MASK; + } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); +} +#else +static void folio_inc_refs(struct folio *folio) +{ +} +#endif /* CONFIG_LRU_GEN */ + +/* + * Mark a page as having seen activity. + * + * inactive,unreferenced -> inactive,referenced + * inactive,referenced -> active,unreferenced + * active,unreferenced -> active,referenced + * + * When a newly allocated page is not yet visible, so safe for non-atomic ops, + * __SetPageReferenced(page) may be substituted for mark_page_accessed(page). + */ +void folio_mark_accessed(struct folio *folio) +{ + if (lru_gen_enabled()) { + folio_inc_refs(folio); + return; + } + + if (!folio_test_referenced(folio)) { + folio_set_referenced(folio); + } else if (folio_test_unevictable(folio)) { + /* + * Unevictable pages are on the "LRU_UNEVICTABLE" list. But, + * this list is never rotated or maintained, so marking an + * unevictable page accessed has no effect. + */ + } else if (!folio_test_active(folio)) { + /* + * If the folio is on the LRU, queue it for activation via + * cpu_fbatches.activate. Otherwise, assume the folio is in a + * folio_batch, mark it active and it'll be moved to the active + * LRU on the next drain. + */ + if (folio_test_lru(folio)) + folio_activate(folio); + else + __lru_cache_activate_folio(folio); + folio_clear_referenced(folio); + workingset_activation(folio); + } + if (folio_test_idle(folio)) + folio_clear_idle(folio); +} +EXPORT_SYMBOL(folio_mark_accessed); + +/** + * folio_add_lru - Add a folio to an LRU list. + * @folio: The folio to be added to the LRU. + * + * Queue the folio for addition to the LRU. The decision on whether + * to add the page to the [in]active [file|anon] list is deferred until the + * folio_batch is drained. This gives a chance for the caller of folio_add_lru() + * have the folio added to the active list using folio_mark_accessed(). + */ +void folio_add_lru(struct folio *folio) +{ + struct folio_batch *fbatch; + + VM_BUG_ON_FOLIO(folio_test_active(folio) && + folio_test_unevictable(folio), folio); + VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + + /* see the comment in lru_gen_add_folio() */ + if (lru_gen_enabled() && !folio_test_unevictable(folio) && + lru_gen_in_fault() && !(current->flags & PF_MEMALLOC)) + folio_set_active(folio); + + folio_get(folio); + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.lru_add); + folio_batch_add_and_move(fbatch, folio, lru_add_fn); + local_unlock(&cpu_fbatches.lock); +} +EXPORT_SYMBOL(folio_add_lru); + +/** + * folio_add_lru_vma() - Add a folio to the appropate LRU list for this VMA. + * @folio: The folio to be added to the LRU. + * @vma: VMA in which the folio is mapped. + * + * If the VMA is mlocked, @folio is added to the unevictable list. + * Otherwise, it is treated the same way as folio_add_lru(). + */ +void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma) +{ + VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + + if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED)) + mlock_new_folio(folio); + else + folio_add_lru(folio); +} + +/* + * If the folio cannot be invalidated, it is moved to the + * inactive list to speed up its reclaim. It is moved to the + * head of the list, rather than the tail, to give the flusher + * threads some time to write it out, as this is much more + * effective than the single-page writeout from reclaim. + * + * If the folio isn't mapped and dirty/writeback, the folio + * could be reclaimed asap using the reclaim flag. + * + * 1. active, mapped folio -> none + * 2. active, dirty/writeback folio -> inactive, head, reclaim + * 3. inactive, mapped folio -> none + * 4. inactive, dirty/writeback folio -> inactive, head, reclaim + * 5. inactive, clean -> inactive, tail + * 6. Others -> none + * + * In 4, it moves to the head of the inactive list so the folio is + * written out by flusher threads as this is much more efficient + * than the single-page writeout from reclaim. + */ +static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio) +{ + bool active = folio_test_active(folio); + long nr_pages = folio_nr_pages(folio); + + if (folio_test_unevictable(folio)) + return; + + /* Some processes are using the folio */ + if (folio_mapped(folio)) + return; + + lruvec_del_folio(lruvec, folio); + folio_clear_active(folio); + folio_clear_referenced(folio); + + if (folio_test_writeback(folio) || folio_test_dirty(folio)) { + /* + * Setting the reclaim flag could race with + * folio_end_writeback() and confuse readahead. But the + * race window is _really_ small and it's not a critical + * problem. + */ + lruvec_add_folio(lruvec, folio); + folio_set_reclaim(folio); + } else { + /* + * The folio's writeback ended while it was in the batch. + * We move that folio to the tail of the inactive list. + */ + lruvec_add_folio_tail(lruvec, folio); + __count_vm_events(PGROTATED, nr_pages); + } + + if (active) { + __count_vm_events(PGDEACTIVATE, nr_pages); + __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, + nr_pages); + } +} + +static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio) +{ + if (!folio_test_unevictable(folio) && (folio_test_active(folio) || lru_gen_enabled())) { + long nr_pages = folio_nr_pages(folio); + + lruvec_del_folio(lruvec, folio); + folio_clear_active(folio); + folio_clear_referenced(folio); + lruvec_add_folio(lruvec, folio); + + __count_vm_events(PGDEACTIVATE, nr_pages); + __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, + nr_pages); + } +} + +static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio) +{ + if (folio_test_anon(folio) && folio_test_swapbacked(folio) && + !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) { + long nr_pages = folio_nr_pages(folio); + + lruvec_del_folio(lruvec, folio); + folio_clear_active(folio); + folio_clear_referenced(folio); + /* + * Lazyfree folios are clean anonymous folios. They have + * the swapbacked flag cleared, to distinguish them from normal + * anonymous folios + */ + folio_clear_swapbacked(folio); + lruvec_add_folio(lruvec, folio); + + __count_vm_events(PGLAZYFREE, nr_pages); + __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE, + nr_pages); + } +} + +/* + * Drain pages out of the cpu's folio_batch. + * Either "cpu" is the current CPU, and preemption has already been + * disabled; or "cpu" is being hot-unplugged, and is already dead. + */ +void lru_add_drain_cpu(int cpu) +{ + struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu); + struct folio_batch *fbatch = &fbatches->lru_add; + + if (folio_batch_count(fbatch)) + folio_batch_move_lru(fbatch, lru_add_fn); + + fbatch = &per_cpu(lru_rotate.fbatch, cpu); + /* Disabling interrupts below acts as a compiler barrier. */ + if (data_race(folio_batch_count(fbatch))) { + unsigned long flags; + + /* No harm done if a racing interrupt already did this */ + local_lock_irqsave(&lru_rotate.lock, flags); + folio_batch_move_lru(fbatch, lru_move_tail_fn); + local_unlock_irqrestore(&lru_rotate.lock, flags); + } + + fbatch = &fbatches->lru_deactivate_file; + if (folio_batch_count(fbatch)) + folio_batch_move_lru(fbatch, lru_deactivate_file_fn); + + fbatch = &fbatches->lru_deactivate; + if (folio_batch_count(fbatch)) + folio_batch_move_lru(fbatch, lru_deactivate_fn); + + fbatch = &fbatches->lru_lazyfree; + if (folio_batch_count(fbatch)) + folio_batch_move_lru(fbatch, lru_lazyfree_fn); + + folio_activate_drain(cpu); +} + +/** + * deactivate_file_folio() - Deactivate a file folio. + * @folio: Folio to deactivate. + * + * This function hints to the VM that @folio is a good reclaim candidate, + * for example if its invalidation fails due to the folio being dirty + * or under writeback. + * + * Context: Caller holds a reference on the folio. + */ +void deactivate_file_folio(struct folio *folio) +{ + struct folio_batch *fbatch; + + /* Deactivating an unevictable folio will not accelerate reclaim */ + if (folio_test_unevictable(folio)) + return; + + folio_get(folio); + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file); + folio_batch_add_and_move(fbatch, folio, lru_deactivate_file_fn); + local_unlock(&cpu_fbatches.lock); +} + +/* + * folio_deactivate - deactivate a folio + * @folio: folio to deactivate + * + * folio_deactivate() moves @folio to the inactive list if @folio was on the + * active list and was not unevictable. This is done to accelerate the + * reclaim of @folio. + */ +void folio_deactivate(struct folio *folio) +{ + if (folio_test_lru(folio) && !folio_test_unevictable(folio) && + (folio_test_active(folio) || lru_gen_enabled())) { + struct folio_batch *fbatch; + + folio_get(folio); + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate); + folio_batch_add_and_move(fbatch, folio, lru_deactivate_fn); + local_unlock(&cpu_fbatches.lock); + } +} + +/** + * folio_mark_lazyfree - make an anon folio lazyfree + * @folio: folio to deactivate + * + * folio_mark_lazyfree() moves @folio to the inactive file list. + * This is done to accelerate the reclaim of @folio. + */ +void folio_mark_lazyfree(struct folio *folio) +{ + if (folio_test_lru(folio) && folio_test_anon(folio) && + folio_test_swapbacked(folio) && !folio_test_swapcache(folio) && + !folio_test_unevictable(folio)) { + struct folio_batch *fbatch; + + folio_get(folio); + local_lock(&cpu_fbatches.lock); + fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree); + folio_batch_add_and_move(fbatch, folio, lru_lazyfree_fn); + local_unlock(&cpu_fbatches.lock); + } +} + +void lru_add_drain(void) +{ + local_lock(&cpu_fbatches.lock); + lru_add_drain_cpu(smp_processor_id()); + local_unlock(&cpu_fbatches.lock); + mlock_drain_local(); +} + +/* + * It's called from per-cpu workqueue context in SMP case so + * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on + * the same cpu. It shouldn't be a problem in !SMP case since + * the core is only one and the locks will disable preemption. + */ +static void lru_add_and_bh_lrus_drain(void) +{ + local_lock(&cpu_fbatches.lock); + lru_add_drain_cpu(smp_processor_id()); + local_unlock(&cpu_fbatches.lock); + invalidate_bh_lrus_cpu(); + mlock_drain_local(); +} + +void lru_add_drain_cpu_zone(struct zone *zone) +{ + local_lock(&cpu_fbatches.lock); + lru_add_drain_cpu(smp_processor_id()); + drain_local_pages(zone); + local_unlock(&cpu_fbatches.lock); + mlock_drain_local(); +} + +#ifdef CONFIG_SMP + +static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); + +static void lru_add_drain_per_cpu(struct work_struct *dummy) +{ + lru_add_and_bh_lrus_drain(); +} + +static bool cpu_needs_drain(unsigned int cpu) +{ + struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu); + + /* Check these in order of likelihood that they're not zero */ + return folio_batch_count(&fbatches->lru_add) || + data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) || + folio_batch_count(&fbatches->lru_deactivate_file) || + folio_batch_count(&fbatches->lru_deactivate) || + folio_batch_count(&fbatches->lru_lazyfree) || + folio_batch_count(&fbatches->activate) || + need_mlock_drain(cpu) || + has_bh_in_lru(cpu, NULL); +} + +/* + * Doesn't need any cpu hotplug locking because we do rely on per-cpu + * kworkers being shut down before our page_alloc_cpu_dead callback is + * executed on the offlined cpu. + * Calling this function with cpu hotplug locks held can actually lead + * to obscure indirect dependencies via WQ context. + */ +static inline void __lru_add_drain_all(bool force_all_cpus) +{ + /* + * lru_drain_gen - Global pages generation number + * + * (A) Definition: global lru_drain_gen = x implies that all generations + * 0 < n <= x are already *scheduled* for draining. + * + * This is an optimization for the highly-contended use case where a + * user space workload keeps constantly generating a flow of pages for + * each CPU. + */ + static unsigned int lru_drain_gen; + static struct cpumask has_work; + static DEFINE_MUTEX(lock); + unsigned cpu, this_gen; + + /* + * Make sure nobody triggers this path before mm_percpu_wq is fully + * initialized. + */ + if (WARN_ON(!mm_percpu_wq)) + return; + + /* + * Guarantee folio_batch counter stores visible by this CPU + * are visible to other CPUs before loading the current drain + * generation. + */ + smp_mb(); + + /* + * (B) Locally cache global LRU draining generation number + * + * The read barrier ensures that the counter is loaded before the mutex + * is taken. It pairs with smp_mb() inside the mutex critical section + * at (D). + */ + this_gen = smp_load_acquire(&lru_drain_gen); + + mutex_lock(&lock); + + /* + * (C) Exit the draining operation if a newer generation, from another + * lru_add_drain_all(), was already scheduled for draining. Check (A). + */ + if (unlikely(this_gen != lru_drain_gen && !force_all_cpus)) + goto done; + + /* + * (D) Increment global generation number + * + * Pairs with smp_load_acquire() at (B), outside of the critical + * section. Use a full memory barrier to guarantee that the + * new global drain generation number is stored before loading + * folio_batch counters. + * + * This pairing must be done here, before the for_each_online_cpu loop + * below which drains the page vectors. + * + * Let x, y, and z represent some system CPU numbers, where x < y < z. + * Assume CPU #z is in the middle of the for_each_online_cpu loop + * below and has already reached CPU #y's per-cpu data. CPU #x comes + * along, adds some pages to its per-cpu vectors, then calls + * lru_add_drain_all(). + * + * If the paired barrier is done at any later step, e.g. after the + * loop, CPU #x will just exit at (C) and miss flushing out all of its + * added pages. + */ + WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1); + smp_mb(); + + cpumask_clear(&has_work); + for_each_online_cpu(cpu) { + struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); + + if (cpu_needs_drain(cpu)) { + INIT_WORK(work, lru_add_drain_per_cpu); + queue_work_on(cpu, mm_percpu_wq, work); + __cpumask_set_cpu(cpu, &has_work); + } + } + + for_each_cpu(cpu, &has_work) + flush_work(&per_cpu(lru_add_drain_work, cpu)); + +done: + mutex_unlock(&lock); +} + +void lru_add_drain_all(void) +{ + __lru_add_drain_all(false); +} +#else +void lru_add_drain_all(void) +{ + lru_add_drain(); +} +#endif /* CONFIG_SMP */ + +atomic_t lru_disable_count = ATOMIC_INIT(0); + +/* + * lru_cache_disable() needs to be called before we start compiling + * a list of pages to be migrated using isolate_lru_page(). + * It drains pages on LRU cache and then disable on all cpus until + * lru_cache_enable is called. + * + * Must be paired with a call to lru_cache_enable(). + */ +void lru_cache_disable(void) +{ + atomic_inc(&lru_disable_count); + /* + * Readers of lru_disable_count are protected by either disabling + * preemption or rcu_read_lock: + * + * preempt_disable, local_irq_disable [bh_lru_lock()] + * rcu_read_lock [rt_spin_lock CONFIG_PREEMPT_RT] + * preempt_disable [local_lock !CONFIG_PREEMPT_RT] + * + * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on + * preempt_disable() regions of code. So any CPU which sees + * lru_disable_count = 0 will have exited the critical + * section when synchronize_rcu() returns. + */ + synchronize_rcu_expedited(); +#ifdef CONFIG_SMP + __lru_add_drain_all(true); +#else + lru_add_and_bh_lrus_drain(); +#endif +} + +/** + * release_pages - batched put_page() + * @arg: array of pages to release + * @nr: number of pages + * + * Decrement the reference count on all the pages in @arg. If it + * fell to zero, remove the page from the LRU and free it. + * + * Note that the argument can be an array of pages, encoded pages, + * or folio pointers. We ignore any encoded bits, and turn any of + * them into just a folio that gets free'd. + */ +void release_pages(release_pages_arg arg, int nr) +{ + int i; + struct encoded_page **encoded = arg.encoded_pages; + LIST_HEAD(pages_to_free); + struct lruvec *lruvec = NULL; + unsigned long flags = 0; + unsigned int lock_batch; + + for (i = 0; i < nr; i++) { + struct folio *folio; + + /* Turn any of the argument types into a folio */ + folio = page_folio(encoded_page_ptr(encoded[i])); + + /* + * Make sure the IRQ-safe lock-holding time does not get + * excessive with a continuous string of pages from the + * same lruvec. The lock is held only if lruvec != NULL. + */ + if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) { + unlock_page_lruvec_irqrestore(lruvec, flags); + lruvec = NULL; + } + + if (is_huge_zero_page(&folio->page)) + continue; + + if (folio_is_zone_device(folio)) { + if (lruvec) { + unlock_page_lruvec_irqrestore(lruvec, flags); + lruvec = NULL; + } + if (put_devmap_managed_page(&folio->page)) + continue; + if (folio_put_testzero(folio)) + free_zone_device_page(&folio->page); + continue; + } + + if (!folio_put_testzero(folio)) + continue; + + if (folio_test_large(folio)) { + if (lruvec) { + unlock_page_lruvec_irqrestore(lruvec, flags); + lruvec = NULL; + } + __folio_put_large(folio); + continue; + } + + if (folio_test_lru(folio)) { + struct lruvec *prev_lruvec = lruvec; + + lruvec = folio_lruvec_relock_irqsave(folio, lruvec, + &flags); + if (prev_lruvec != lruvec) + lock_batch = 0; + + lruvec_del_folio(lruvec, folio); + __folio_clear_lru_flags(folio); + } + + /* + * In rare cases, when truncation or holepunching raced with + * munlock after VM_LOCKED was cleared, Mlocked may still be + * found set here. This does not indicate a problem, unless + * "unevictable_pgs_cleared" appears worryingly large. + */ + if (unlikely(folio_test_mlocked(folio))) { + __folio_clear_mlocked(folio); + zone_stat_sub_folio(folio, NR_MLOCK); + count_vm_event(UNEVICTABLE_PGCLEARED); + } + + list_add(&folio->lru, &pages_to_free); + } + if (lruvec) + unlock_page_lruvec_irqrestore(lruvec, flags); + + mem_cgroup_uncharge_list(&pages_to_free); + free_unref_page_list(&pages_to_free); +} +EXPORT_SYMBOL(release_pages); + +/* + * The folios which we're about to release may be in the deferred lru-addition + * queues. That would prevent them from really being freed right now. That's + * OK from a correctness point of view but is inefficient - those folios may be + * cache-warm and we want to give them back to the page allocator ASAP. + * + * So __folio_batch_release() will drain those queues here. + * folio_batch_move_lru() calls folios_put() directly to avoid + * mutual recursion. + */ +void __folio_batch_release(struct folio_batch *fbatch) +{ + if (!fbatch->percpu_pvec_drained) { + lru_add_drain(); + fbatch->percpu_pvec_drained = true; + } + release_pages(fbatch->folios, folio_batch_count(fbatch)); + folio_batch_reinit(fbatch); +} +EXPORT_SYMBOL(__folio_batch_release); + +/** + * folio_batch_remove_exceptionals() - Prune non-folios from a batch. + * @fbatch: The batch to prune + * + * find_get_entries() fills a batch with both folios and shadow/swap/DAX + * entries. This function prunes all the non-folio entries from @fbatch + * without leaving holes, so that it can be passed on to folio-only batch + * operations. + */ +void folio_batch_remove_exceptionals(struct folio_batch *fbatch) +{ + unsigned int i, j; + + for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) { + struct folio *folio = fbatch->folios[i]; + if (!xa_is_value(folio)) + fbatch->folios[j++] = folio; + } + fbatch->nr = j; +} + +/* + * Perform any setup for the swap system + */ +void __init swap_setup(void) +{ + unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT); + + /* Use a smaller cluster for small-memory machines */ + if (megs < 16) + page_cluster = 2; + else + page_cluster = 3; + /* + * Right now other parts of the system means that we + * _really_ don't want to cluster much more + */ +} |