/* * 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/sysctl/vm.txt. * 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/percpu.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/backing-dev.h> #include <linux/memcontrol.h> #include <linux/gfp.h> #include "internal.h" /* How many pages do we try to swap or page in/out together? */ int page_cluster; static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs); static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs); static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs); /* * This path almost never happens for VM activity - pages are normally * freed via pagevecs. But it gets used by networking. */ static void __page_cache_release(struct page *page) { if (PageLRU(page)) { struct zone *zone = page_zone(page); struct lruvec *lruvec; unsigned long flags; spin_lock_irqsave(&zone->lru_lock, flags); lruvec = mem_cgroup_page_lruvec(page, zone); VM_BUG_ON(!PageLRU(page)); __ClearPageLRU(page); del_page_from_lru_list(page, lruvec, page_off_lru(page)); spin_unlock_irqrestore(&zone->lru_lock, flags); } } static void __put_single_page(struct page *page) { __page_cache_release(page); free_hot_cold_page(page, 0); } static void __put_compound_page(struct page *page) { compound_page_dtor *dtor; __page_cache_release(page); dtor = get_compound_page_dtor(page); (*dtor)(page); } static void put_compound_page(struct page *page) { if (unlikely(PageTail(page))) { /* __split_huge_page_refcount can run under us */ struct page *page_head = compound_trans_head(page); if (likely(page != page_head && get_page_unless_zero(page_head))) { unsigned long flags; /* * THP can not break up slab pages so avoid taking * compound_lock(). Slab performs non-atomic bit ops * on page->flags for better performance. In particular * slab_unlock() in slub used to be a hot path. It is * still hot on arches that do not support * this_cpu_cmpxchg_double(). */ if (PageSlab(page_head)) { if (PageTail(page)) { if (put_page_testzero(page_head)) VM_BUG_ON(1); atomic_dec(&page->_mapcount); goto skip_lock_tail; } else goto skip_lock; } /* * page_head wasn't a dangling pointer but it * may not be a head page anymore by the time * we obtain the lock. That is ok as long as it * can't be freed from under us. */ flags = compound_lock_irqsave(page_head); if (unlikely(!PageTail(page))) { /* __split_huge_page_refcount run before us */ compound_unlock_irqrestore(page_head, flags); skip_lock: if (put_page_testzero(page_head)) __put_single_page(page_head); out_put_single: if (put_page_testzero(page)) __put_single_page(page); return; } VM_BUG_ON(page_head != page->first_page); /* * We can release the refcount taken by * get_page_unless_zero() now that * __split_huge_page_refcount() is blocked on * the compound_lock. */ if (put_page_testzero(page_head)) VM_BUG_ON(1); /* __split_huge_page_refcount will wait now */ VM_BUG_ON(page_mapcount(page) <= 0); atomic_dec(&page->_mapcount); VM_BUG_ON(atomic_read(&page_head->_count) <= 0); VM_BUG_ON(atomic_read(&page->_count) != 0); compound_unlock_irqrestore(page_head, flags); skip_lock_tail: if (put_page_testzero(page_head)) { if (PageHead(page_head)) __put_compound_page(page_head); else __put_single_page(page_head); } } else { /* page_head is a dangling pointer */ VM_BUG_ON(PageTail(page)); goto out_put_single; } } else if (put_page_testzero(page)) { if (PageHead(page)) __put_compound_page(page); else __put_single_page(page); } } void put_page(struct page *page) { if (unlikely(PageCompound(page))) put_compound_page(page); else if (put_page_testzero(page)) __put_single_page(page); } EXPORT_SYMBOL(put_page); /* * This function is exported but must not be called by anything other * than get_page(). It implements the slow path of get_page(). */ bool __get_page_tail(struct page *page) { /* * This takes care of get_page() if run on a tail page * returned by one of the get_user_pages/follow_page variants. * get_user_pages/follow_page itself doesn't need the compound * lock because it runs __get_page_tail_foll() under the * proper PT lock that already serializes against * split_huge_page(). */ unsigned long flags; bool got = false; struct page *page_head = compound_trans_head(page); if (likely(page != page_head && get_page_unless_zero(page_head))) { /* Ref to put_compound_page() comment. */ if (PageSlab(page_head)) { if (likely(PageTail(page))) { __get_page_tail_foll(page, false); return true; } else { put_page(page_head); return false; } } /* * page_head wasn't a dangling pointer but it * may not be a head page anymore by the time * we obtain the lock. That is ok as long as it * can't be freed from under us. */ flags = compound_lock_irqsave(page_head); /* here __split_huge_page_refcount won't run anymore */ if (likely(PageTail(page))) { __get_page_tail_foll(page, false); got = true; } compound_unlock_irqrestore(page_head, flags); if (unlikely(!got)) put_page(page_head); } return got; } EXPORT_SYMBOL(__get_page_tail); /** * 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. Currently * used by read_cache_pages() and related error recovery code. */ void put_pages_list(struct list_head *pages) { while (!list_empty(pages)) { struct page *victim; victim = list_entry(pages->prev, struct page, lru); list_del(&victim->lru); page_cache_release(victim); } } EXPORT_SYMBOL(put_pages_list); static void pagevec_lru_move_fn(struct pagevec *pvec, void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg), void *arg) { int i; struct zone *zone = NULL; struct lruvec *lruvec; unsigned long flags = 0; for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; struct zone *pagezone = page_zone(page); if (pagezone != zone) { if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); zone = pagezone; spin_lock_irqsave(&zone->lru_lock, flags); } lruvec = mem_cgroup_page_lruvec(page, zone); (*move_fn)(page, lruvec, arg); } if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); release_pages(pvec->pages, pvec->nr, pvec->cold); pagevec_reinit(pvec); } static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec, void *arg) { int *pgmoved = arg; if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { enum lru_list lru = page_lru_base_type(page); list_move_tail(&page->lru, &lruvec->lists[lru]); (*pgmoved)++; } } /* * pagevec_move_tail() must be called with IRQ disabled. * Otherwise this may cause nasty races. */ static void pagevec_move_tail(struct pagevec *pvec) { int pgmoved = 0; pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved); __count_vm_events(PGROTATED, pgmoved); } /* * Writeback is about to end against a page which has been marked for immediate * reclaim. If it still appears to be reclaimable, move it to the tail of the * inactive list. */ void rotate_reclaimable_page(struct page *page) { if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) && !PageUnevictable(page) && PageLRU(page)) { struct pagevec *pvec; unsigned long flags; page_cache_get(page); local_irq_save(flags); pvec = &__get_cpu_var(lru_rotate_pvecs); if (!pagevec_add(pvec, page)) pagevec_move_tail(pvec); local_irq_restore(flags); } } static void update_page_reclaim_stat(struct lruvec *lruvec, int file, int rotated) { struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; reclaim_stat->recent_scanned[file]++; if (rotated) reclaim_stat->recent_rotated[file]++; } static void __activate_page(struct page *page, struct lruvec *lruvec, void *arg) { if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { int file = page_is_file_cache(page); int lru = page_lru_base_type(page); del_page_from_lru_list(page, lruvec, lru); SetPageActive(page); lru += LRU_ACTIVE; add_page_to_lru_list(page, lruvec, lru); __count_vm_event(PGACTIVATE); update_page_reclaim_stat(lruvec, file, 1); } } #ifdef CONFIG_SMP static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs); static void activate_page_drain(int cpu) { struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu); if (pagevec_count(pvec)) pagevec_lru_move_fn(pvec, __activate_page, NULL); } void activate_page(struct page *page) { if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { struct pagevec *pvec = &get_cpu_var(activate_page_pvecs); page_cache_get(page); if (!pagevec_add(pvec, page)) pagevec_lru_move_fn(pvec, __activate_page, NULL); put_cpu_var(activate_page_pvecs); } } #else static inline void activate_page_drain(int cpu) { } void activate_page(struct page *page) { struct zone *zone = page_zone(page); spin_lock_irq(&zone->lru_lock); __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL); spin_unlock_irq(&zone->lru_lock); } #endif /* * Mark a page as having seen activity. * * inactive,unreferenced -> inactive,referenced * inactive,referenced -> active,unreferenced * active,unreferenced -> active,referenced */ void mark_page_accessed(struct page *page) { if (!PageActive(page) && !PageUnevictable(page) && PageReferenced(page) && PageLRU(page)) { activate_page(page); ClearPageReferenced(page); } else if (!PageReferenced(page)) { SetPageReferenced(page); } } EXPORT_SYMBOL(mark_page_accessed); void __lru_cache_add(struct page *page, enum lru_list lru) { struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru]; page_cache_get(page); if (!pagevec_add(pvec, page)) __pagevec_lru_add(pvec, lru); put_cpu_var(lru_add_pvecs); } EXPORT_SYMBOL(__lru_cache_add); /** * lru_cache_add_lru - add a page to a page list * @page: the page to be added to the LRU. * @lru: the LRU list to which the page is added. */ void lru_cache_add_lru(struct page *page, enum lru_list lru) { if (PageActive(page)) { VM_BUG_ON(PageUnevictable(page)); ClearPageActive(page); } else if (PageUnevictable(page)) { VM_BUG_ON(PageActive(page)); ClearPageUnevictable(page); } VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page)); __lru_cache_add(page, lru); } /** * add_page_to_unevictable_list - add a page to the unevictable list * @page: the page to be added to the unevictable list * * Add page directly to its zone's unevictable list. To avoid races with * tasks that might be making the page evictable, through eg. munlock, * munmap or exit, while it's not on the lru, we want to add the page * while it's locked or otherwise "invisible" to other tasks. This is * difficult to do when using the pagevec cache, so bypass that. */ void add_page_to_unevictable_list(struct page *page) { struct zone *zone = page_zone(page); struct lruvec *lruvec; spin_lock_irq(&zone->lru_lock); lruvec = mem_cgroup_page_lruvec(page, zone); SetPageUnevictable(page); SetPageLRU(page); add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE); spin_unlock_irq(&zone->lru_lock); } /* * If the page can not 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 page isn't page_mapped and dirty/writeback, the page * could reclaim asap using PG_reclaim. * * 1. active, mapped page -> none * 2. active, dirty/writeback page -> inactive, head, PG_reclaim * 3. inactive, mapped page -> none * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim * 5. inactive, clean -> inactive, tail * 6. Others -> none * * In 4, why it moves inactive's head, the VM expects the page would * be write it out by flusher threads as this is much more effective * than the single-page writeout from reclaim. */ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec, void *arg) { int lru, file; bool active; if (!PageLRU(page)) return; if (PageUnevictable(page)) return; /* Some processes are using the page */ if (page_mapped(page)) return; active = PageActive(page); file = page_is_file_cache(page); lru = page_lru_base_type(page); del_page_from_lru_list(page, lruvec, lru + active); ClearPageActive(page); ClearPageReferenced(page); add_page_to_lru_list(page, lruvec, lru); if (PageWriteback(page) || PageDirty(page)) { /* * PG_reclaim could be raced with end_page_writeback * It can make readahead confusing. But race window * is _really_ small and it's non-critical problem. */ SetPageReclaim(page); } else { /* * The page's writeback ends up during pagevec * We moves tha page into tail of inactive. */ list_move_tail(&page->lru, &lruvec->lists[lru]); __count_vm_event(PGROTATED); } if (active) __count_vm_event(PGDEACTIVATE); update_page_reclaim_stat(lruvec, file, 0); } /* * Drain pages out of the cpu's pagevecs. * 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 pagevec *pvecs = per_cpu(lru_add_pvecs, cpu); struct pagevec *pvec; int lru; for_each_lru(lru) { pvec = &pvecs[lru - LRU_BASE]; if (pagevec_count(pvec)) __pagevec_lru_add(pvec, lru); } pvec = &per_cpu(lru_rotate_pvecs, cpu); if (pagevec_count(pvec)) { unsigned long flags; /* No harm done if a racing interrupt already did this */ local_irq_save(flags); pagevec_move_tail(pvec); local_irq_restore(flags); } pvec = &per_cpu(lru_deactivate_pvecs, cpu); if (pagevec_count(pvec)) pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL); activate_page_drain(cpu); } /** * deactivate_page - forcefully deactivate a page * @page: page to deactivate * * This function hints the VM that @page is a good reclaim candidate, * for example if its invalidation fails due to the page being dirty * or under writeback. */ void deactivate_page(struct page *page) { /* * In a workload with many unevictable page such as mprotect, unevictable * page deactivation for accelerating reclaim is pointless. */ if (PageUnevictable(page)) return; if (likely(get_page_unless_zero(page))) { struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs); if (!pagevec_add(pvec, page)) pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL); put_cpu_var(lru_deactivate_pvecs); } } void lru_add_drain(void) { lru_add_drain_cpu(get_cpu()); put_cpu(); } static void lru_add_drain_per_cpu(struct work_struct *dummy) { lru_add_drain(); } /* * Returns 0 for success */ int lru_add_drain_all(void) { return schedule_on_each_cpu(lru_add_drain_per_cpu); } /* * Batched page_cache_release(). Decrement the reference count on all the * passed pages. If it fell to zero then remove the page from the LRU and * free it. * * Avoid taking zone->lru_lock if possible, but if it is taken, retain it * for the remainder of the operation. * * The locking in this function is against shrink_inactive_list(): we recheck * the page count inside the lock to see whether shrink_inactive_list() * grabbed the page via the LRU. If it did, give up: shrink_inactive_list() * will free it. */ void release_pages(struct page **pages, int nr, int cold) { int i; LIST_HEAD(pages_to_free); struct zone *zone = NULL; struct lruvec *lruvec; unsigned long uninitialized_var(flags); for (i = 0; i < nr; i++) { struct page *page = pages[i]; if (unlikely(PageCompound(page))) { if (zone) { spin_unlock_irqrestore(&zone->lru_lock, flags); zone = NULL; } put_compound_page(page); continue; } if (!put_page_testzero(page)) continue; if (PageLRU(page)) { struct zone *pagezone = page_zone(page); if (pagezone != zone) { if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); zone = pagezone; spin_lock_irqsave(&zone->lru_lock, flags); } lruvec = mem_cgroup_page_lruvec(page, zone); VM_BUG_ON(!PageLRU(page)); __ClearPageLRU(page); del_page_from_lru_list(page, lruvec, page_off_lru(page)); } list_add(&page->lru, &pages_to_free); } if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); free_hot_cold_page_list(&pages_to_free, cold); } EXPORT_SYMBOL(release_pages); /* * The pages 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 pages may be * cache-warm and we want to give them back to the page allocator ASAP. * * So __pagevec_release() will drain those queues here. __pagevec_lru_add() * and __pagevec_lru_add_active() call release_pages() directly to avoid * mutual recursion. */ void __pagevec_release(struct pagevec *pvec) { lru_add_drain(); release_pages(pvec->pages, pagevec_count(pvec), pvec->cold); pagevec_reinit(pvec); } EXPORT_SYMBOL(__pagevec_release); #ifdef CONFIG_TRANSPARENT_HUGEPAGE /* used by __split_huge_page_refcount() */ void lru_add_page_tail(struct page *page, struct page *page_tail, struct lruvec *lruvec) { int uninitialized_var(active); enum lru_list lru; const int file = 0; VM_BUG_ON(!PageHead(page)); VM_BUG_ON(PageCompound(page_tail)); VM_BUG_ON(PageLRU(page_tail)); VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&lruvec_zone(lruvec)->lru_lock)); SetPageLRU(page_tail); if (page_evictable(page_tail, NULL)) { if (PageActive(page)) { SetPageActive(page_tail); active = 1; lru = LRU_ACTIVE_ANON; } else { active = 0; lru = LRU_INACTIVE_ANON; } } else { SetPageUnevictable(page_tail); lru = LRU_UNEVICTABLE; } if (likely(PageLRU(page))) list_add_tail(&page_tail->lru, &page->lru); else { struct list_head *list_head; /* * Head page has not yet been counted, as an hpage, * so we must account for each subpage individually. * * Use the standard add function to put page_tail on the list, * but then correct its position so they all end up in order. */ add_page_to_lru_list(page_tail, lruvec, lru); list_head = page_tail->lru.prev; list_move_tail(&page_tail->lru, list_head); } if (!PageUnevictable(page)) update_page_reclaim_stat(lruvec, file, active); } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec, void *arg) { enum lru_list lru = (enum lru_list)arg; int file = is_file_lru(lru); int active = is_active_lru(lru); VM_BUG_ON(PageActive(page)); VM_BUG_ON(PageUnevictable(page)); VM_BUG_ON(PageLRU(page)); SetPageLRU(page); if (active) SetPageActive(page); add_page_to_lru_list(page, lruvec, lru); update_page_reclaim_stat(lruvec, file, active); } /* * Add the passed pages to the LRU, then drop the caller's refcount * on them. Reinitialises the caller's pagevec. */ void __pagevec_lru_add(struct pagevec *pvec, enum lru_list lru) { VM_BUG_ON(is_unevictable_lru(lru)); pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)lru); } EXPORT_SYMBOL(__pagevec_lru_add); /** * pagevec_lookup - gang pagecache lookup * @pvec: Where the resulting pages are placed * @mapping: The address_space to search * @start: The starting page index * @nr_pages: The maximum number of pages * * pagevec_lookup() will search for and return a group of up to @nr_pages pages * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a * reference against the pages in @pvec. * * The search returns a group of mapping-contiguous pages with ascending * indexes. There may be holes in the indices due to not-present pages. * * pagevec_lookup() returns the number of pages which were found. */ unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping, pgoff_t start, unsigned nr_pages) { pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages); return pagevec_count(pvec); } EXPORT_SYMBOL(pagevec_lookup); unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping, pgoff_t *index, int tag, unsigned nr_pages) { pvec->nr = find_get_pages_tag(mapping, index, tag, nr_pages, pvec->pages); return pagevec_count(pvec); } EXPORT_SYMBOL(pagevec_lookup_tag); /* * Perform any setup for the swap system */ void __init swap_setup(void) { unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT); #ifdef CONFIG_SWAP bdi_init(swapper_space.backing_dev_info); #endif /* 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 */ }