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-rw-r--r--mm/swap.c784
1 files changed, 784 insertions, 0 deletions
diff --git a/mm/swap.c b/mm/swap.c
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index 00000000..5c13f133
--- /dev/null
+++ b/mm/swap.c
@@ -0,0 +1,784 @@
+/*
+ * 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)) {
+ unsigned long flags;
+ struct zone *zone = page_zone(page);
+
+ spin_lock_irqsave(&zone->lru_lock, flags);
+ VM_BUG_ON(!PageLRU(page));
+ __ClearPageLRU(page);
+ del_page_from_lru_list(zone, page, 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;
+ /*
+ * 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);
+ VM_BUG_ON(PageHead(page_head));
+ 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);
+ 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))) {
+ /*
+ * 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, void *arg),
+ void *arg)
+{
+ int i;
+ struct zone *zone = NULL;
+ 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);
+ }
+
+ (*move_fn)(page, 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, void *arg)
+{
+ int *pgmoved = arg;
+
+ if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
+ enum lru_list lru = page_lru_base_type(page);
+ struct lruvec *lruvec;
+
+ lruvec = mem_cgroup_lru_move_lists(page_zone(page),
+ page, lru, lru);
+ 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 zone *zone, struct page *page,
+ int file, int rotated)
+{
+ struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
+ struct zone_reclaim_stat *memcg_reclaim_stat;
+
+ memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
+
+ reclaim_stat->recent_scanned[file]++;
+ if (rotated)
+ reclaim_stat->recent_rotated[file]++;
+
+ if (!memcg_reclaim_stat)
+ return;
+
+ memcg_reclaim_stat->recent_scanned[file]++;
+ if (rotated)
+ memcg_reclaim_stat->recent_rotated[file]++;
+}
+
+static void __activate_page(struct page *page, void *arg)
+{
+ struct zone *zone = page_zone(page);
+
+ 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(zone, page, lru);
+
+ SetPageActive(page);
+ lru += LRU_ACTIVE;
+ add_page_to_lru_list(zone, page, lru);
+ __count_vm_event(PGACTIVATE);
+
+ update_page_reclaim_stat(zone, page, 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, 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);
+
+ spin_lock_irq(&zone->lru_lock);
+ SetPageUnevictable(page);
+ SetPageLRU(page);
+ add_page_to_lru_list(zone, page, 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, void *arg)
+{
+ int lru, file;
+ bool active;
+ struct zone *zone = page_zone(page);
+
+ 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(zone, page, lru + active);
+ ClearPageActive(page);
+ ClearPageReferenced(page);
+ add_page_to_lru_list(zone, page, 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 {
+ struct lruvec *lruvec;
+ /*
+ * The page's writeback ends up during pagevec
+ * We moves tha page into tail of inactive.
+ */
+ lruvec = mem_cgroup_lru_move_lists(zone, page, lru, lru);
+ list_move_tail(&page->lru, &lruvec->lists[lru]);
+ __count_vm_event(PGROTATED);
+ }
+
+ if (active)
+ __count_vm_event(PGDEACTIVATE);
+ update_page_reclaim_stat(zone, page, 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;
+ 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);
+ }
+ VM_BUG_ON(!PageLRU(page));
+ __ClearPageLRU(page);
+ del_page_from_lru_list(zone, page, 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 zone* zone,
+ struct page *page, struct page *page_tail)
+{
+ 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(&zone->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(zone, page_tail, lru);
+ list_head = page_tail->lru.prev;
+ list_move_tail(&page_tail->lru, list_head);
+ }
+
+ if (!PageUnevictable(page))
+ update_page_reclaim_stat(zone, page_tail, file, active);
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+static void __pagevec_lru_add_fn(struct page *page, void *arg)
+{
+ enum lru_list lru = (enum lru_list)arg;
+ struct zone *zone = page_zone(page);
+ 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(zone, page, lru);
+ update_page_reclaim_stat(zone, page, 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
+ */
+}
generated by cgit (git 2.34.1) at 2024-12-20 04:26:36 +0000