v4.19.13 snapshot.
diff --git a/mm/compaction.c b/mm/compaction.c
new file mode 100644
index 0000000..faca45e
--- /dev/null
+++ b/mm/compaction.c
@@ -0,0 +1,2158 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/mm/compaction.c
+ *
+ * Memory compaction for the reduction of external fragmentation. Note that
+ * this heavily depends upon page migration to do all the real heavy
+ * lifting
+ *
+ * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
+ */
+#include <linux/cpu.h>
+#include <linux/swap.h>
+#include <linux/migrate.h>
+#include <linux/compaction.h>
+#include <linux/mm_inline.h>
+#include <linux/sched/signal.h>
+#include <linux/backing-dev.h>
+#include <linux/sysctl.h>
+#include <linux/sysfs.h>
+#include <linux/page-isolation.h>
+#include <linux/kasan.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/page_owner.h>
+#include "internal.h"
+
+#ifdef CONFIG_COMPACTION
+static inline void count_compact_event(enum vm_event_item item)
+{
+ count_vm_event(item);
+}
+
+static inline void count_compact_events(enum vm_event_item item, long delta)
+{
+ count_vm_events(item, delta);
+}
+#else
+#define count_compact_event(item) do { } while (0)
+#define count_compact_events(item, delta) do { } while (0)
+#endif
+
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/compaction.h>
+
+#define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
+#define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
+#define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
+#define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
+
+static unsigned long release_freepages(struct list_head *freelist)
+{
+ struct page *page, *next;
+ unsigned long high_pfn = 0;
+
+ list_for_each_entry_safe(page, next, freelist, lru) {
+ unsigned long pfn = page_to_pfn(page);
+ list_del(&page->lru);
+ __free_page(page);
+ if (pfn > high_pfn)
+ high_pfn = pfn;
+ }
+
+ return high_pfn;
+}
+
+static void map_pages(struct list_head *list)
+{
+ unsigned int i, order, nr_pages;
+ struct page *page, *next;
+ LIST_HEAD(tmp_list);
+
+ list_for_each_entry_safe(page, next, list, lru) {
+ list_del(&page->lru);
+
+ order = page_private(page);
+ nr_pages = 1 << order;
+
+ post_alloc_hook(page, order, __GFP_MOVABLE);
+ if (order)
+ split_page(page, order);
+
+ for (i = 0; i < nr_pages; i++) {
+ list_add(&page->lru, &tmp_list);
+ page++;
+ }
+ }
+
+ list_splice(&tmp_list, list);
+}
+
+#ifdef CONFIG_COMPACTION
+
+int PageMovable(struct page *page)
+{
+ struct address_space *mapping;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (!__PageMovable(page))
+ return 0;
+
+ mapping = page_mapping(page);
+ if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
+ return 1;
+
+ return 0;
+}
+EXPORT_SYMBOL(PageMovable);
+
+void __SetPageMovable(struct page *page, struct address_space *mapping)
+{
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
+ page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
+}
+EXPORT_SYMBOL(__SetPageMovable);
+
+void __ClearPageMovable(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageMovable(page), page);
+ /*
+ * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
+ * flag so that VM can catch up released page by driver after isolation.
+ * With it, VM migration doesn't try to put it back.
+ */
+ page->mapping = (void *)((unsigned long)page->mapping &
+ PAGE_MAPPING_MOVABLE);
+}
+EXPORT_SYMBOL(__ClearPageMovable);
+
+/* Do not skip compaction more than 64 times */
+#define COMPACT_MAX_DEFER_SHIFT 6
+
+/*
+ * Compaction is deferred when compaction fails to result in a page
+ * allocation success. 1 << compact_defer_limit compactions are skipped up
+ * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
+ */
+void defer_compaction(struct zone *zone, int order)
+{
+ zone->compact_considered = 0;
+ zone->compact_defer_shift++;
+
+ if (order < zone->compact_order_failed)
+ zone->compact_order_failed = order;
+
+ if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
+ zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
+
+ trace_mm_compaction_defer_compaction(zone, order);
+}
+
+/* Returns true if compaction should be skipped this time */
+bool compaction_deferred(struct zone *zone, int order)
+{
+ unsigned long defer_limit = 1UL << zone->compact_defer_shift;
+
+ if (order < zone->compact_order_failed)
+ return false;
+
+ /* Avoid possible overflow */
+ if (++zone->compact_considered > defer_limit)
+ zone->compact_considered = defer_limit;
+
+ if (zone->compact_considered >= defer_limit)
+ return false;
+
+ trace_mm_compaction_deferred(zone, order);
+
+ return true;
+}
+
+/*
+ * Update defer tracking counters after successful compaction of given order,
+ * which means an allocation either succeeded (alloc_success == true) or is
+ * expected to succeed.
+ */
+void compaction_defer_reset(struct zone *zone, int order,
+ bool alloc_success)
+{
+ if (alloc_success) {
+ zone->compact_considered = 0;
+ zone->compact_defer_shift = 0;
+ }
+ if (order >= zone->compact_order_failed)
+ zone->compact_order_failed = order + 1;
+
+ trace_mm_compaction_defer_reset(zone, order);
+}
+
+/* Returns true if restarting compaction after many failures */
+bool compaction_restarting(struct zone *zone, int order)
+{
+ if (order < zone->compact_order_failed)
+ return false;
+
+ return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
+ zone->compact_considered >= 1UL << zone->compact_defer_shift;
+}
+
+/* Returns true if the pageblock should be scanned for pages to isolate. */
+static inline bool isolation_suitable(struct compact_control *cc,
+ struct page *page)
+{
+ if (cc->ignore_skip_hint)
+ return true;
+
+ return !get_pageblock_skip(page);
+}
+
+static void reset_cached_positions(struct zone *zone)
+{
+ zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
+ zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
+ zone->compact_cached_free_pfn =
+ pageblock_start_pfn(zone_end_pfn(zone) - 1);
+}
+
+/*
+ * Compound pages of >= pageblock_order should consistenly be skipped until
+ * released. It is always pointless to compact pages of such order (if they are
+ * migratable), and the pageblocks they occupy cannot contain any free pages.
+ */
+static bool pageblock_skip_persistent(struct page *page)
+{
+ if (!PageCompound(page))
+ return false;
+
+ page = compound_head(page);
+
+ if (compound_order(page) >= pageblock_order)
+ return true;
+
+ return false;
+}
+
+/*
+ * This function is called to clear all cached information on pageblocks that
+ * should be skipped for page isolation when the migrate and free page scanner
+ * meet.
+ */
+static void __reset_isolation_suitable(struct zone *zone)
+{
+ unsigned long start_pfn = zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(zone);
+ unsigned long pfn;
+
+ zone->compact_blockskip_flush = false;
+
+ /* Walk the zone and mark every pageblock as suitable for isolation */
+ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
+ struct page *page;
+
+ cond_resched();
+
+ page = pfn_to_online_page(pfn);
+ if (!page)
+ continue;
+ if (zone != page_zone(page))
+ continue;
+ if (pageblock_skip_persistent(page))
+ continue;
+
+ clear_pageblock_skip(page);
+ }
+
+ reset_cached_positions(zone);
+}
+
+void reset_isolation_suitable(pg_data_t *pgdat)
+{
+ int zoneid;
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+ struct zone *zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ /* Only flush if a full compaction finished recently */
+ if (zone->compact_blockskip_flush)
+ __reset_isolation_suitable(zone);
+ }
+}
+
+/*
+ * If no pages were isolated then mark this pageblock to be skipped in the
+ * future. The information is later cleared by __reset_isolation_suitable().
+ */
+static void update_pageblock_skip(struct compact_control *cc,
+ struct page *page, unsigned long nr_isolated,
+ bool migrate_scanner)
+{
+ struct zone *zone = cc->zone;
+ unsigned long pfn;
+
+ if (cc->no_set_skip_hint)
+ return;
+
+ if (!page)
+ return;
+
+ if (nr_isolated)
+ return;
+
+ set_pageblock_skip(page);
+
+ pfn = page_to_pfn(page);
+
+ /* Update where async and sync compaction should restart */
+ if (migrate_scanner) {
+ if (pfn > zone->compact_cached_migrate_pfn[0])
+ zone->compact_cached_migrate_pfn[0] = pfn;
+ if (cc->mode != MIGRATE_ASYNC &&
+ pfn > zone->compact_cached_migrate_pfn[1])
+ zone->compact_cached_migrate_pfn[1] = pfn;
+ } else {
+ if (pfn < zone->compact_cached_free_pfn)
+ zone->compact_cached_free_pfn = pfn;
+ }
+}
+#else
+static inline bool isolation_suitable(struct compact_control *cc,
+ struct page *page)
+{
+ return true;
+}
+
+static inline bool pageblock_skip_persistent(struct page *page)
+{
+ return false;
+}
+
+static inline void update_pageblock_skip(struct compact_control *cc,
+ struct page *page, unsigned long nr_isolated,
+ bool migrate_scanner)
+{
+}
+#endif /* CONFIG_COMPACTION */
+
+/*
+ * Compaction requires the taking of some coarse locks that are potentially
+ * very heavily contended. For async compaction, back out if the lock cannot
+ * be taken immediately. For sync compaction, spin on the lock if needed.
+ *
+ * Returns true if the lock is held
+ * Returns false if the lock is not held and compaction should abort
+ */
+static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
+ struct compact_control *cc)
+{
+ if (cc->mode == MIGRATE_ASYNC) {
+ if (!spin_trylock_irqsave(lock, *flags)) {
+ cc->contended = true;
+ return false;
+ }
+ } else {
+ spin_lock_irqsave(lock, *flags);
+ }
+
+ return true;
+}
+
+/*
+ * Compaction requires the taking of some coarse locks that are potentially
+ * very heavily contended. The lock should be periodically unlocked to avoid
+ * having disabled IRQs for a long time, even when there is nobody waiting on
+ * the lock. It might also be that allowing the IRQs will result in
+ * need_resched() becoming true. If scheduling is needed, async compaction
+ * aborts. Sync compaction schedules.
+ * Either compaction type will also abort if a fatal signal is pending.
+ * In either case if the lock was locked, it is dropped and not regained.
+ *
+ * Returns true if compaction should abort due to fatal signal pending, or
+ * async compaction due to need_resched()
+ * Returns false when compaction can continue (sync compaction might have
+ * scheduled)
+ */
+static bool compact_unlock_should_abort(spinlock_t *lock,
+ unsigned long flags, bool *locked, struct compact_control *cc)
+{
+ if (*locked) {
+ spin_unlock_irqrestore(lock, flags);
+ *locked = false;
+ }
+
+ if (fatal_signal_pending(current)) {
+ cc->contended = true;
+ return true;
+ }
+
+ if (need_resched()) {
+ if (cc->mode == MIGRATE_ASYNC) {
+ cc->contended = true;
+ return true;
+ }
+ cond_resched();
+ }
+
+ return false;
+}
+
+/*
+ * Aside from avoiding lock contention, compaction also periodically checks
+ * need_resched() and either schedules in sync compaction or aborts async
+ * compaction. This is similar to what compact_unlock_should_abort() does, but
+ * is used where no lock is concerned.
+ *
+ * Returns false when no scheduling was needed, or sync compaction scheduled.
+ * Returns true when async compaction should abort.
+ */
+static inline bool compact_should_abort(struct compact_control *cc)
+{
+ /* async compaction aborts if contended */
+ if (need_resched()) {
+ if (cc->mode == MIGRATE_ASYNC) {
+ cc->contended = true;
+ return true;
+ }
+
+ cond_resched();
+ }
+
+ return false;
+}
+
+/*
+ * Isolate free pages onto a private freelist. If @strict is true, will abort
+ * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
+ * (even though it may still end up isolating some pages).
+ */
+static unsigned long isolate_freepages_block(struct compact_control *cc,
+ unsigned long *start_pfn,
+ unsigned long end_pfn,
+ struct list_head *freelist,
+ bool strict)
+{
+ int nr_scanned = 0, total_isolated = 0;
+ struct page *cursor, *valid_page = NULL;
+ unsigned long flags = 0;
+ bool locked = false;
+ unsigned long blockpfn = *start_pfn;
+ unsigned int order;
+
+ cursor = pfn_to_page(blockpfn);
+
+ /* Isolate free pages. */
+ for (; blockpfn < end_pfn; blockpfn++, cursor++) {
+ int isolated;
+ struct page *page = cursor;
+
+ /*
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort if fatal signal
+ * pending or async compaction detects need_resched()
+ */
+ if (!(blockpfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(&cc->zone->lock, flags,
+ &locked, cc))
+ break;
+
+ nr_scanned++;
+ if (!pfn_valid_within(blockpfn))
+ goto isolate_fail;
+
+ if (!valid_page)
+ valid_page = page;
+
+ /*
+ * For compound pages such as THP and hugetlbfs, we can save
+ * potentially a lot of iterations if we skip them at once.
+ * The check is racy, but we can consider only valid values
+ * and the only danger is skipping too much.
+ */
+ if (PageCompound(page)) {
+ const unsigned int order = compound_order(page);
+
+ if (likely(order < MAX_ORDER)) {
+ blockpfn += (1UL << order) - 1;
+ cursor += (1UL << order) - 1;
+ }
+ goto isolate_fail;
+ }
+
+ if (!PageBuddy(page))
+ goto isolate_fail;
+
+ /*
+ * If we already hold the lock, we can skip some rechecking.
+ * Note that if we hold the lock now, checked_pageblock was
+ * already set in some previous iteration (or strict is true),
+ * so it is correct to skip the suitable migration target
+ * recheck as well.
+ */
+ if (!locked) {
+ /*
+ * The zone lock must be held to isolate freepages.
+ * Unfortunately this is a very coarse lock and can be
+ * heavily contended if there are parallel allocations
+ * or parallel compactions. For async compaction do not
+ * spin on the lock and we acquire the lock as late as
+ * possible.
+ */
+ locked = compact_trylock_irqsave(&cc->zone->lock,
+ &flags, cc);
+ if (!locked)
+ break;
+
+ /* Recheck this is a buddy page under lock */
+ if (!PageBuddy(page))
+ goto isolate_fail;
+ }
+
+ /* Found a free page, will break it into order-0 pages */
+ order = page_order(page);
+ isolated = __isolate_free_page(page, order);
+ if (!isolated)
+ break;
+ set_page_private(page, order);
+
+ total_isolated += isolated;
+ cc->nr_freepages += isolated;
+ list_add_tail(&page->lru, freelist);
+
+ if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
+ blockpfn += isolated;
+ break;
+ }
+ /* Advance to the end of split page */
+ blockpfn += isolated - 1;
+ cursor += isolated - 1;
+ continue;
+
+isolate_fail:
+ if (strict)
+ break;
+ else
+ continue;
+
+ }
+
+ if (locked)
+ spin_unlock_irqrestore(&cc->zone->lock, flags);
+
+ /*
+ * There is a tiny chance that we have read bogus compound_order(),
+ * so be careful to not go outside of the pageblock.
+ */
+ if (unlikely(blockpfn > end_pfn))
+ blockpfn = end_pfn;
+
+ trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
+ nr_scanned, total_isolated);
+
+ /* Record how far we have got within the block */
+ *start_pfn = blockpfn;
+
+ /*
+ * If strict isolation is requested by CMA then check that all the
+ * pages requested were isolated. If there were any failures, 0 is
+ * returned and CMA will fail.
+ */
+ if (strict && blockpfn < end_pfn)
+ total_isolated = 0;
+
+ /* Update the pageblock-skip if the whole pageblock was scanned */
+ if (blockpfn == end_pfn)
+ update_pageblock_skip(cc, valid_page, total_isolated, false);
+
+ cc->total_free_scanned += nr_scanned;
+ if (total_isolated)
+ count_compact_events(COMPACTISOLATED, total_isolated);
+ return total_isolated;
+}
+
+/**
+ * isolate_freepages_range() - isolate free pages.
+ * @cc: Compaction control structure.
+ * @start_pfn: The first PFN to start isolating.
+ * @end_pfn: The one-past-last PFN.
+ *
+ * Non-free pages, invalid PFNs, or zone boundaries within the
+ * [start_pfn, end_pfn) range are considered errors, cause function to
+ * undo its actions and return zero.
+ *
+ * Otherwise, function returns one-past-the-last PFN of isolated page
+ * (which may be greater then end_pfn if end fell in a middle of
+ * a free page).
+ */
+unsigned long
+isolate_freepages_range(struct compact_control *cc,
+ unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
+ LIST_HEAD(freelist);
+
+ pfn = start_pfn;
+ block_start_pfn = pageblock_start_pfn(pfn);
+ if (block_start_pfn < cc->zone->zone_start_pfn)
+ block_start_pfn = cc->zone->zone_start_pfn;
+ block_end_pfn = pageblock_end_pfn(pfn);
+
+ for (; pfn < end_pfn; pfn += isolated,
+ block_start_pfn = block_end_pfn,
+ block_end_pfn += pageblock_nr_pages) {
+ /* Protect pfn from changing by isolate_freepages_block */
+ unsigned long isolate_start_pfn = pfn;
+
+ block_end_pfn = min(block_end_pfn, end_pfn);
+
+ /*
+ * pfn could pass the block_end_pfn if isolated freepage
+ * is more than pageblock order. In this case, we adjust
+ * scanning range to right one.
+ */
+ if (pfn >= block_end_pfn) {
+ block_start_pfn = pageblock_start_pfn(pfn);
+ block_end_pfn = pageblock_end_pfn(pfn);
+ block_end_pfn = min(block_end_pfn, end_pfn);
+ }
+
+ if (!pageblock_pfn_to_page(block_start_pfn,
+ block_end_pfn, cc->zone))
+ break;
+
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, &freelist, true);
+
+ /*
+ * In strict mode, isolate_freepages_block() returns 0 if
+ * there are any holes in the block (ie. invalid PFNs or
+ * non-free pages).
+ */
+ if (!isolated)
+ break;
+
+ /*
+ * If we managed to isolate pages, it is always (1 << n) *
+ * pageblock_nr_pages for some non-negative n. (Max order
+ * page may span two pageblocks).
+ */
+ }
+
+ /* __isolate_free_page() does not map the pages */
+ map_pages(&freelist);
+
+ if (pfn < end_pfn) {
+ /* Loop terminated early, cleanup. */
+ release_freepages(&freelist);
+ return 0;
+ }
+
+ /* We don't use freelists for anything. */
+ return pfn;
+}
+
+/* Similar to reclaim, but different enough that they don't share logic */
+static bool too_many_isolated(struct zone *zone)
+{
+ unsigned long active, inactive, isolated;
+
+ inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) +
+ node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON);
+ active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) +
+ node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON);
+ isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) +
+ node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON);
+
+ return isolated > (inactive + active) / 2;
+}
+
+/**
+ * isolate_migratepages_block() - isolate all migrate-able pages within
+ * a single pageblock
+ * @cc: Compaction control structure.
+ * @low_pfn: The first PFN to isolate
+ * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
+ * @isolate_mode: Isolation mode to be used.
+ *
+ * Isolate all pages that can be migrated from the range specified by
+ * [low_pfn, end_pfn). The range is expected to be within same pageblock.
+ * Returns zero if there is a fatal signal pending, otherwise PFN of the
+ * first page that was not scanned (which may be both less, equal to or more
+ * than end_pfn).
+ *
+ * The pages are isolated on cc->migratepages list (not required to be empty),
+ * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
+ * is neither read nor updated.
+ */
+static unsigned long
+isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
+ unsigned long end_pfn, isolate_mode_t isolate_mode)
+{
+ struct zone *zone = cc->zone;
+ unsigned long nr_scanned = 0, nr_isolated = 0;
+ struct lruvec *lruvec;
+ unsigned long flags = 0;
+ bool locked = false;
+ struct page *page = NULL, *valid_page = NULL;
+ unsigned long start_pfn = low_pfn;
+ bool skip_on_failure = false;
+ unsigned long next_skip_pfn = 0;
+
+ /*
+ * Ensure that there are not too many pages isolated from the LRU
+ * list by either parallel reclaimers or compaction. If there are,
+ * delay for some time until fewer pages are isolated
+ */
+ while (unlikely(too_many_isolated(zone))) {
+ /* async migration should just abort */
+ if (cc->mode == MIGRATE_ASYNC)
+ return 0;
+
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+ if (fatal_signal_pending(current))
+ return 0;
+ }
+
+ if (compact_should_abort(cc))
+ return 0;
+
+ if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
+ skip_on_failure = true;
+ next_skip_pfn = block_end_pfn(low_pfn, cc->order);
+ }
+
+ /* Time to isolate some pages for migration */
+ for (; low_pfn < end_pfn; low_pfn++) {
+
+ if (skip_on_failure && low_pfn >= next_skip_pfn) {
+ /*
+ * We have isolated all migration candidates in the
+ * previous order-aligned block, and did not skip it due
+ * to failure. We should migrate the pages now and
+ * hopefully succeed compaction.
+ */
+ if (nr_isolated)
+ break;
+
+ /*
+ * We failed to isolate in the previous order-aligned
+ * block. Set the new boundary to the end of the
+ * current block. Note we can't simply increase
+ * next_skip_pfn by 1 << order, as low_pfn might have
+ * been incremented by a higher number due to skipping
+ * a compound or a high-order buddy page in the
+ * previous loop iteration.
+ */
+ next_skip_pfn = block_end_pfn(low_pfn, cc->order);
+ }
+
+ /*
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort async compaction
+ * if contended.
+ */
+ if (!(low_pfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(zone_lru_lock(zone), flags,
+ &locked, cc))
+ break;
+
+ if (!pfn_valid_within(low_pfn))
+ goto isolate_fail;
+ nr_scanned++;
+
+ page = pfn_to_page(low_pfn);
+
+ if (!valid_page)
+ valid_page = page;
+
+ /*
+ * Skip if free. We read page order here without zone lock
+ * which is generally unsafe, but the race window is small and
+ * the worst thing that can happen is that we skip some
+ * potential isolation targets.
+ */
+ if (PageBuddy(page)) {
+ unsigned long freepage_order = page_order_unsafe(page);
+
+ /*
+ * Without lock, we cannot be sure that what we got is
+ * a valid page order. Consider only values in the
+ * valid order range to prevent low_pfn overflow.
+ */
+ if (freepage_order > 0 && freepage_order < MAX_ORDER)
+ low_pfn += (1UL << freepage_order) - 1;
+ continue;
+ }
+
+ /*
+ * Regardless of being on LRU, compound pages such as THP and
+ * hugetlbfs are not to be compacted. We can potentially save
+ * a lot of iterations if we skip them at once. The check is
+ * racy, but we can consider only valid values and the only
+ * danger is skipping too much.
+ */
+ if (PageCompound(page)) {
+ const unsigned int order = compound_order(page);
+
+ if (likely(order < MAX_ORDER))
+ low_pfn += (1UL << order) - 1;
+ goto isolate_fail;
+ }
+
+ /*
+ * Check may be lockless but that's ok as we recheck later.
+ * It's possible to migrate LRU and non-lru movable pages.
+ * Skip any other type of page
+ */
+ if (!PageLRU(page)) {
+ /*
+ * __PageMovable can return false positive so we need
+ * to verify it under page_lock.
+ */
+ if (unlikely(__PageMovable(page)) &&
+ !PageIsolated(page)) {
+ if (locked) {
+ spin_unlock_irqrestore(zone_lru_lock(zone),
+ flags);
+ locked = false;
+ }
+
+ if (!isolate_movable_page(page, isolate_mode))
+ goto isolate_success;
+ }
+
+ goto isolate_fail;
+ }
+
+ /*
+ * Migration will fail if an anonymous page is pinned in memory,
+ * so avoid taking lru_lock and isolating it unnecessarily in an
+ * admittedly racy check.
+ */
+ if (!page_mapping(page) &&
+ page_count(page) > page_mapcount(page))
+ goto isolate_fail;
+
+ /*
+ * Only allow to migrate anonymous pages in GFP_NOFS context
+ * because those do not depend on fs locks.
+ */
+ if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
+ goto isolate_fail;
+
+ /* If we already hold the lock, we can skip some rechecking */
+ if (!locked) {
+ locked = compact_trylock_irqsave(zone_lru_lock(zone),
+ &flags, cc);
+ if (!locked)
+ break;
+
+ /* Recheck PageLRU and PageCompound under lock */
+ if (!PageLRU(page))
+ goto isolate_fail;
+
+ /*
+ * Page become compound since the non-locked check,
+ * and it's on LRU. It can only be a THP so the order
+ * is safe to read and it's 0 for tail pages.
+ */
+ if (unlikely(PageCompound(page))) {
+ low_pfn += (1UL << compound_order(page)) - 1;
+ goto isolate_fail;
+ }
+ }
+
+ lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
+
+ /* Try isolate the page */
+ if (__isolate_lru_page(page, isolate_mode) != 0)
+ goto isolate_fail;
+
+ VM_BUG_ON_PAGE(PageCompound(page), page);
+
+ /* Successfully isolated */
+ del_page_from_lru_list(page, lruvec, page_lru(page));
+ inc_node_page_state(page,
+ NR_ISOLATED_ANON + page_is_file_cache(page));
+
+isolate_success:
+ list_add(&page->lru, &cc->migratepages);
+ cc->nr_migratepages++;
+ nr_isolated++;
+
+ /*
+ * Record where we could have freed pages by migration and not
+ * yet flushed them to buddy allocator.
+ * - this is the lowest page that was isolated and likely be
+ * then freed by migration.
+ */
+ if (!cc->last_migrated_pfn)
+ cc->last_migrated_pfn = low_pfn;
+
+ /* Avoid isolating too much */
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
+ ++low_pfn;
+ break;
+ }
+
+ continue;
+isolate_fail:
+ if (!skip_on_failure)
+ continue;
+
+ /*
+ * We have isolated some pages, but then failed. Release them
+ * instead of migrating, as we cannot form the cc->order buddy
+ * page anyway.
+ */
+ if (nr_isolated) {
+ if (locked) {
+ spin_unlock_irqrestore(zone_lru_lock(zone), flags);
+ locked = false;
+ }
+ putback_movable_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ cc->last_migrated_pfn = 0;
+ nr_isolated = 0;
+ }
+
+ if (low_pfn < next_skip_pfn) {
+ low_pfn = next_skip_pfn - 1;
+ /*
+ * The check near the loop beginning would have updated
+ * next_skip_pfn too, but this is a bit simpler.
+ */
+ next_skip_pfn += 1UL << cc->order;
+ }
+ }
+
+ /*
+ * The PageBuddy() check could have potentially brought us outside
+ * the range to be scanned.
+ */
+ if (unlikely(low_pfn > end_pfn))
+ low_pfn = end_pfn;
+
+ if (locked)
+ spin_unlock_irqrestore(zone_lru_lock(zone), flags);
+
+ /*
+ * Update the pageblock-skip information and cached scanner pfn,
+ * if the whole pageblock was scanned without isolating any page.
+ */
+ if (low_pfn == end_pfn)
+ update_pageblock_skip(cc, valid_page, nr_isolated, true);
+
+ trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
+ nr_scanned, nr_isolated);
+
+ cc->total_migrate_scanned += nr_scanned;
+ if (nr_isolated)
+ count_compact_events(COMPACTISOLATED, nr_isolated);
+
+ return low_pfn;
+}
+
+/**
+ * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
+ * @cc: Compaction control structure.
+ * @start_pfn: The first PFN to start isolating.
+ * @end_pfn: The one-past-last PFN.
+ *
+ * Returns zero if isolation fails fatally due to e.g. pending signal.
+ * Otherwise, function returns one-past-the-last PFN of isolated page
+ * (which may be greater than end_pfn if end fell in a middle of a THP page).
+ */
+unsigned long
+isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
+ unsigned long end_pfn)
+{
+ unsigned long pfn, block_start_pfn, block_end_pfn;
+
+ /* Scan block by block. First and last block may be incomplete */
+ pfn = start_pfn;
+ block_start_pfn = pageblock_start_pfn(pfn);
+ if (block_start_pfn < cc->zone->zone_start_pfn)
+ block_start_pfn = cc->zone->zone_start_pfn;
+ block_end_pfn = pageblock_end_pfn(pfn);
+
+ for (; pfn < end_pfn; pfn = block_end_pfn,
+ block_start_pfn = block_end_pfn,
+ block_end_pfn += pageblock_nr_pages) {
+
+ block_end_pfn = min(block_end_pfn, end_pfn);
+
+ if (!pageblock_pfn_to_page(block_start_pfn,
+ block_end_pfn, cc->zone))
+ continue;
+
+ pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
+ ISOLATE_UNEVICTABLE);
+
+ if (!pfn)
+ break;
+
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
+ break;
+ }
+
+ return pfn;
+}
+
+#endif /* CONFIG_COMPACTION || CONFIG_CMA */
+#ifdef CONFIG_COMPACTION
+
+static bool suitable_migration_source(struct compact_control *cc,
+ struct page *page)
+{
+ int block_mt;
+
+ if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
+ return true;
+
+ block_mt = get_pageblock_migratetype(page);
+
+ if (cc->migratetype == MIGRATE_MOVABLE)
+ return is_migrate_movable(block_mt);
+ else
+ return block_mt == cc->migratetype;
+}
+
+/* Returns true if the page is within a block suitable for migration to */
+static bool suitable_migration_target(struct compact_control *cc,
+ struct page *page)
+{
+ /* If the page is a large free page, then disallow migration */
+ if (PageBuddy(page)) {
+ /*
+ * We are checking page_order without zone->lock taken. But
+ * the only small danger is that we skip a potentially suitable
+ * pageblock, so it's not worth to check order for valid range.
+ */
+ if (page_order_unsafe(page) >= pageblock_order)
+ return false;
+ }
+
+ if (cc->ignore_block_suitable)
+ return true;
+
+ /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
+ if (is_migrate_movable(get_pageblock_migratetype(page)))
+ return true;
+
+ /* Otherwise skip the block */
+ return false;
+}
+
+/*
+ * Test whether the free scanner has reached the same or lower pageblock than
+ * the migration scanner, and compaction should thus terminate.
+ */
+static inline bool compact_scanners_met(struct compact_control *cc)
+{
+ return (cc->free_pfn >> pageblock_order)
+ <= (cc->migrate_pfn >> pageblock_order);
+}
+
+/*
+ * Based on information in the current compact_control, find blocks
+ * suitable for isolating free pages from and then isolate them.
+ */
+static void isolate_freepages(struct compact_control *cc)
+{
+ struct zone *zone = cc->zone;
+ struct page *page;
+ unsigned long block_start_pfn; /* start of current pageblock */
+ unsigned long isolate_start_pfn; /* exact pfn we start at */
+ unsigned long block_end_pfn; /* end of current pageblock */
+ unsigned long low_pfn; /* lowest pfn scanner is able to scan */
+ struct list_head *freelist = &cc->freepages;
+
+ /*
+ * Initialise the free scanner. The starting point is where we last
+ * successfully isolated from, zone-cached value, or the end of the
+ * zone when isolating for the first time. For looping we also need
+ * this pfn aligned down to the pageblock boundary, because we do
+ * block_start_pfn -= pageblock_nr_pages in the for loop.
+ * For ending point, take care when isolating in last pageblock of a
+ * a zone which ends in the middle of a pageblock.
+ * The low boundary is the end of the pageblock the migration scanner
+ * is using.
+ */
+ isolate_start_pfn = cc->free_pfn;
+ block_start_pfn = pageblock_start_pfn(cc->free_pfn);
+ block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
+ zone_end_pfn(zone));
+ low_pfn = pageblock_end_pfn(cc->migrate_pfn);
+
+ /*
+ * Isolate free pages until enough are available to migrate the
+ * pages on cc->migratepages. We stop searching if the migrate
+ * and free page scanners meet or enough free pages are isolated.
+ */
+ for (; block_start_pfn >= low_pfn;
+ block_end_pfn = block_start_pfn,
+ block_start_pfn -= pageblock_nr_pages,
+ isolate_start_pfn = block_start_pfn) {
+ /*
+ * This can iterate a massively long zone without finding any
+ * suitable migration targets, so periodically check if we need
+ * to schedule, or even abort async compaction.
+ */
+ if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
+ && compact_should_abort(cc))
+ break;
+
+ page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
+ zone);
+ if (!page)
+ continue;
+
+ /* Check the block is suitable for migration */
+ if (!suitable_migration_target(cc, page))
+ continue;
+
+ /* If isolation recently failed, do not retry */
+ if (!isolation_suitable(cc, page))
+ continue;
+
+ /* Found a block suitable for isolating free pages from. */
+ isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn,
+ freelist, false);
+
+ /*
+ * If we isolated enough freepages, or aborted due to lock
+ * contention, terminate.
+ */
+ if ((cc->nr_freepages >= cc->nr_migratepages)
+ || cc->contended) {
+ if (isolate_start_pfn >= block_end_pfn) {
+ /*
+ * Restart at previous pageblock if more
+ * freepages can be isolated next time.
+ */
+ isolate_start_pfn =
+ block_start_pfn - pageblock_nr_pages;
+ }
+ break;
+ } else if (isolate_start_pfn < block_end_pfn) {
+ /*
+ * If isolation failed early, do not continue
+ * needlessly.
+ */
+ break;
+ }
+ }
+
+ /* __isolate_free_page() does not map the pages */
+ map_pages(freelist);
+
+ /*
+ * Record where the free scanner will restart next time. Either we
+ * broke from the loop and set isolate_start_pfn based on the last
+ * call to isolate_freepages_block(), or we met the migration scanner
+ * and the loop terminated due to isolate_start_pfn < low_pfn
+ */
+ cc->free_pfn = isolate_start_pfn;
+}
+
+/*
+ * This is a migrate-callback that "allocates" freepages by taking pages
+ * from the isolated freelists in the block we are migrating to.
+ */
+static struct page *compaction_alloc(struct page *migratepage,
+ unsigned long data)
+{
+ struct compact_control *cc = (struct compact_control *)data;
+ struct page *freepage;
+
+ /*
+ * Isolate free pages if necessary, and if we are not aborting due to
+ * contention.
+ */
+ if (list_empty(&cc->freepages)) {
+ if (!cc->contended)
+ isolate_freepages(cc);
+
+ if (list_empty(&cc->freepages))
+ return NULL;
+ }
+
+ freepage = list_entry(cc->freepages.next, struct page, lru);
+ list_del(&freepage->lru);
+ cc->nr_freepages--;
+
+ return freepage;
+}
+
+/*
+ * This is a migrate-callback that "frees" freepages back to the isolated
+ * freelist. All pages on the freelist are from the same zone, so there is no
+ * special handling needed for NUMA.
+ */
+static void compaction_free(struct page *page, unsigned long data)
+{
+ struct compact_control *cc = (struct compact_control *)data;
+
+ list_add(&page->lru, &cc->freepages);
+ cc->nr_freepages++;
+}
+
+/* possible outcome of isolate_migratepages */
+typedef enum {
+ ISOLATE_ABORT, /* Abort compaction now */
+ ISOLATE_NONE, /* No pages isolated, continue scanning */
+ ISOLATE_SUCCESS, /* Pages isolated, migrate */
+} isolate_migrate_t;
+
+/*
+ * Allow userspace to control policy on scanning the unevictable LRU for
+ * compactable pages.
+ */
+int sysctl_compact_unevictable_allowed __read_mostly = 1;
+
+/*
+ * Isolate all pages that can be migrated from the first suitable block,
+ * starting at the block pointed to by the migrate scanner pfn within
+ * compact_control.
+ */
+static isolate_migrate_t isolate_migratepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned long block_start_pfn;
+ unsigned long block_end_pfn;
+ unsigned long low_pfn;
+ struct page *page;
+ const isolate_mode_t isolate_mode =
+ (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
+ (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
+
+ /*
+ * Start at where we last stopped, or beginning of the zone as
+ * initialized by compact_zone()
+ */
+ low_pfn = cc->migrate_pfn;
+ block_start_pfn = pageblock_start_pfn(low_pfn);
+ if (block_start_pfn < zone->zone_start_pfn)
+ block_start_pfn = zone->zone_start_pfn;
+
+ /* Only scan within a pageblock boundary */
+ block_end_pfn = pageblock_end_pfn(low_pfn);
+
+ /*
+ * Iterate over whole pageblocks until we find the first suitable.
+ * Do not cross the free scanner.
+ */
+ for (; block_end_pfn <= cc->free_pfn;
+ low_pfn = block_end_pfn,
+ block_start_pfn = block_end_pfn,
+ block_end_pfn += pageblock_nr_pages) {
+
+ /*
+ * This can potentially iterate a massively long zone with
+ * many pageblocks unsuitable, so periodically check if we
+ * need to schedule, or even abort async compaction.
+ */
+ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
+ && compact_should_abort(cc))
+ break;
+
+ page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
+ zone);
+ if (!page)
+ continue;
+
+ /* If isolation recently failed, do not retry */
+ if (!isolation_suitable(cc, page))
+ continue;
+
+ /*
+ * For async compaction, also only scan in MOVABLE blocks.
+ * Async compaction is optimistic to see if the minimum amount
+ * of work satisfies the allocation.
+ */
+ if (!suitable_migration_source(cc, page))
+ continue;
+
+ /* Perform the isolation */
+ low_pfn = isolate_migratepages_block(cc, low_pfn,
+ block_end_pfn, isolate_mode);
+
+ if (!low_pfn || cc->contended)
+ return ISOLATE_ABORT;
+
+ /*
+ * Either we isolated something and proceed with migration. Or
+ * we failed and compact_zone should decide if we should
+ * continue or not.
+ */
+ break;
+ }
+
+ /* Record where migration scanner will be restarted. */
+ cc->migrate_pfn = low_pfn;
+
+ return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
+}
+
+/*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+static inline bool is_via_compact_memory(int order)
+{
+ return order == -1;
+}
+
+static enum compact_result __compact_finished(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned int order;
+ const int migratetype = cc->migratetype;
+
+ if (cc->contended || fatal_signal_pending(current))
+ return COMPACT_CONTENDED;
+
+ /* Compaction run completes if the migrate and free scanner meet */
+ if (compact_scanners_met(cc)) {
+ /* Let the next compaction start anew. */
+ reset_cached_positions(zone);
+
+ /*
+ * Mark that the PG_migrate_skip information should be cleared
+ * by kswapd when it goes to sleep. kcompactd does not set the
+ * flag itself as the decision to be clear should be directly
+ * based on an allocation request.
+ */
+ if (cc->direct_compaction)
+ zone->compact_blockskip_flush = true;
+
+ if (cc->whole_zone)
+ return COMPACT_COMPLETE;
+ else
+ return COMPACT_PARTIAL_SKIPPED;
+ }
+
+ if (is_via_compact_memory(cc->order))
+ return COMPACT_CONTINUE;
+
+ if (cc->finishing_block) {
+ /*
+ * We have finished the pageblock, but better check again that
+ * we really succeeded.
+ */
+ if (IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
+ cc->finishing_block = false;
+ else
+ return COMPACT_CONTINUE;
+ }
+
+ /* Direct compactor: Is a suitable page free? */
+ for (order = cc->order; order < MAX_ORDER; order++) {
+ struct free_area *area = &zone->free_area[order];
+ bool can_steal;
+
+ /* Job done if page is free of the right migratetype */
+ if (!list_empty(&area->free_list[migratetype]))
+ return COMPACT_SUCCESS;
+
+#ifdef CONFIG_CMA
+ /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
+ if (migratetype == MIGRATE_MOVABLE &&
+ !list_empty(&area->free_list[MIGRATE_CMA]))
+ return COMPACT_SUCCESS;
+#endif
+ /*
+ * Job done if allocation would steal freepages from
+ * other migratetype buddy lists.
+ */
+ if (find_suitable_fallback(area, order, migratetype,
+ true, &can_steal) != -1) {
+
+ /* movable pages are OK in any pageblock */
+ if (migratetype == MIGRATE_MOVABLE)
+ return COMPACT_SUCCESS;
+
+ /*
+ * We are stealing for a non-movable allocation. Make
+ * sure we finish compacting the current pageblock
+ * first so it is as free as possible and we won't
+ * have to steal another one soon. This only applies
+ * to sync compaction, as async compaction operates
+ * on pageblocks of the same migratetype.
+ */
+ if (cc->mode == MIGRATE_ASYNC ||
+ IS_ALIGNED(cc->migrate_pfn,
+ pageblock_nr_pages)) {
+ return COMPACT_SUCCESS;
+ }
+
+ cc->finishing_block = true;
+ return COMPACT_CONTINUE;
+ }
+ }
+
+ return COMPACT_NO_SUITABLE_PAGE;
+}
+
+static enum compact_result compact_finished(struct zone *zone,
+ struct compact_control *cc)
+{
+ int ret;
+
+ ret = __compact_finished(zone, cc);
+ trace_mm_compaction_finished(zone, cc->order, ret);
+ if (ret == COMPACT_NO_SUITABLE_PAGE)
+ ret = COMPACT_CONTINUE;
+
+ return ret;
+}
+
+/*
+ * compaction_suitable: Is this suitable to run compaction on this zone now?
+ * Returns
+ * COMPACT_SKIPPED - If there are too few free pages for compaction
+ * COMPACT_SUCCESS - If the allocation would succeed without compaction
+ * COMPACT_CONTINUE - If compaction should run now
+ */
+static enum compact_result __compaction_suitable(struct zone *zone, int order,
+ unsigned int alloc_flags,
+ int classzone_idx,
+ unsigned long wmark_target)
+{
+ unsigned long watermark;
+
+ if (is_via_compact_memory(order))
+ return COMPACT_CONTINUE;
+
+ watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
+ /*
+ * If watermarks for high-order allocation are already met, there
+ * should be no need for compaction at all.
+ */
+ if (zone_watermark_ok(zone, order, watermark, classzone_idx,
+ alloc_flags))
+ return COMPACT_SUCCESS;
+
+ /*
+ * Watermarks for order-0 must be met for compaction to be able to
+ * isolate free pages for migration targets. This means that the
+ * watermark and alloc_flags have to match, or be more pessimistic than
+ * the check in __isolate_free_page(). We don't use the direct
+ * compactor's alloc_flags, as they are not relevant for freepage
+ * isolation. We however do use the direct compactor's classzone_idx to
+ * skip over zones where lowmem reserves would prevent allocation even
+ * if compaction succeeds.
+ * For costly orders, we require low watermark instead of min for
+ * compaction to proceed to increase its chances.
+ * ALLOC_CMA is used, as pages in CMA pageblocks are considered
+ * suitable migration targets
+ */
+ watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
+ low_wmark_pages(zone) : min_wmark_pages(zone);
+ watermark += compact_gap(order);
+ if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
+ ALLOC_CMA, wmark_target))
+ return COMPACT_SKIPPED;
+
+ return COMPACT_CONTINUE;
+}
+
+enum compact_result compaction_suitable(struct zone *zone, int order,
+ unsigned int alloc_flags,
+ int classzone_idx)
+{
+ enum compact_result ret;
+ int fragindex;
+
+ ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
+ zone_page_state(zone, NR_FREE_PAGES));
+ /*
+ * fragmentation index determines if allocation failures are due to
+ * low memory or external fragmentation
+ *
+ * index of -1000 would imply allocations might succeed depending on
+ * watermarks, but we already failed the high-order watermark check
+ * index towards 0 implies failure is due to lack of memory
+ * index towards 1000 implies failure is due to fragmentation
+ *
+ * Only compact if a failure would be due to fragmentation. Also
+ * ignore fragindex for non-costly orders where the alternative to
+ * a successful reclaim/compaction is OOM. Fragindex and the
+ * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
+ * excessive compaction for costly orders, but it should not be at the
+ * expense of system stability.
+ */
+ if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
+ fragindex = fragmentation_index(zone, order);
+ if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
+ ret = COMPACT_NOT_SUITABLE_ZONE;
+ }
+
+ trace_mm_compaction_suitable(zone, order, ret);
+ if (ret == COMPACT_NOT_SUITABLE_ZONE)
+ ret = COMPACT_SKIPPED;
+
+ return ret;
+}
+
+bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
+ int alloc_flags)
+{
+ struct zone *zone;
+ struct zoneref *z;
+
+ /*
+ * Make sure at least one zone would pass __compaction_suitable if we continue
+ * retrying the reclaim.
+ */
+ for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
+ ac->nodemask) {
+ unsigned long available;
+ enum compact_result compact_result;
+
+ /*
+ * Do not consider all the reclaimable memory because we do not
+ * want to trash just for a single high order allocation which
+ * is even not guaranteed to appear even if __compaction_suitable
+ * is happy about the watermark check.
+ */
+ available = zone_reclaimable_pages(zone) / order;
+ available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
+ compact_result = __compaction_suitable(zone, order, alloc_flags,
+ ac_classzone_idx(ac), available);
+ if (compact_result != COMPACT_SKIPPED)
+ return true;
+ }
+
+ return false;
+}
+
+static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
+{
+ enum compact_result ret;
+ unsigned long start_pfn = zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(zone);
+ const bool sync = cc->mode != MIGRATE_ASYNC;
+
+ cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
+ ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
+ cc->classzone_idx);
+ /* Compaction is likely to fail */
+ if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
+ return ret;
+
+ /* huh, compaction_suitable is returning something unexpected */
+ VM_BUG_ON(ret != COMPACT_CONTINUE);
+
+ /*
+ * Clear pageblock skip if there were failures recently and compaction
+ * is about to be retried after being deferred.
+ */
+ if (compaction_restarting(zone, cc->order))
+ __reset_isolation_suitable(zone);
+
+ /*
+ * Setup to move all movable pages to the end of the zone. Used cached
+ * information on where the scanners should start (unless we explicitly
+ * want to compact the whole zone), but check that it is initialised
+ * by ensuring the values are within zone boundaries.
+ */
+ if (cc->whole_zone) {
+ cc->migrate_pfn = start_pfn;
+ cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
+ } else {
+ cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
+ cc->free_pfn = zone->compact_cached_free_pfn;
+ if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
+ cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
+ zone->compact_cached_free_pfn = cc->free_pfn;
+ }
+ if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
+ cc->migrate_pfn = start_pfn;
+ zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
+ zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
+ }
+
+ if (cc->migrate_pfn == start_pfn)
+ cc->whole_zone = true;
+ }
+
+ cc->last_migrated_pfn = 0;
+
+ trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
+ cc->free_pfn, end_pfn, sync);
+
+ migrate_prep_local();
+
+ while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
+ int err;
+
+ switch (isolate_migratepages(zone, cc)) {
+ case ISOLATE_ABORT:
+ ret = COMPACT_CONTENDED;
+ putback_movable_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ goto out;
+ case ISOLATE_NONE:
+ /*
+ * We haven't isolated and migrated anything, but
+ * there might still be unflushed migrations from
+ * previous cc->order aligned block.
+ */
+ goto check_drain;
+ case ISOLATE_SUCCESS:
+ ;
+ }
+
+ err = migrate_pages(&cc->migratepages, compaction_alloc,
+ compaction_free, (unsigned long)cc, cc->mode,
+ MR_COMPACTION);
+
+ trace_mm_compaction_migratepages(cc->nr_migratepages, err,
+ &cc->migratepages);
+
+ /* All pages were either migrated or will be released */
+ cc->nr_migratepages = 0;
+ if (err) {
+ putback_movable_pages(&cc->migratepages);
+ /*
+ * migrate_pages() may return -ENOMEM when scanners meet
+ * and we want compact_finished() to detect it
+ */
+ if (err == -ENOMEM && !compact_scanners_met(cc)) {
+ ret = COMPACT_CONTENDED;
+ goto out;
+ }
+ /*
+ * We failed to migrate at least one page in the current
+ * order-aligned block, so skip the rest of it.
+ */
+ if (cc->direct_compaction &&
+ (cc->mode == MIGRATE_ASYNC)) {
+ cc->migrate_pfn = block_end_pfn(
+ cc->migrate_pfn - 1, cc->order);
+ /* Draining pcplists is useless in this case */
+ cc->last_migrated_pfn = 0;
+
+ }
+ }
+
+check_drain:
+ /*
+ * Has the migration scanner moved away from the previous
+ * cc->order aligned block where we migrated from? If yes,
+ * flush the pages that were freed, so that they can merge and
+ * compact_finished() can detect immediately if allocation
+ * would succeed.
+ */
+ if (cc->order > 0 && cc->last_migrated_pfn) {
+ int cpu;
+ unsigned long current_block_start =
+ block_start_pfn(cc->migrate_pfn, cc->order);
+
+ if (cc->last_migrated_pfn < current_block_start) {
+ cpu = get_cpu();
+ lru_add_drain_cpu(cpu);
+ drain_local_pages(zone);
+ put_cpu();
+ /* No more flushing until we migrate again */
+ cc->last_migrated_pfn = 0;
+ }
+ }
+
+ }
+
+out:
+ /*
+ * Release free pages and update where the free scanner should restart,
+ * so we don't leave any returned pages behind in the next attempt.
+ */
+ if (cc->nr_freepages > 0) {
+ unsigned long free_pfn = release_freepages(&cc->freepages);
+
+ cc->nr_freepages = 0;
+ VM_BUG_ON(free_pfn == 0);
+ /* The cached pfn is always the first in a pageblock */
+ free_pfn = pageblock_start_pfn(free_pfn);
+ /*
+ * Only go back, not forward. The cached pfn might have been
+ * already reset to zone end in compact_finished()
+ */
+ if (free_pfn > zone->compact_cached_free_pfn)
+ zone->compact_cached_free_pfn = free_pfn;
+ }
+
+ count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
+ count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
+
+ trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
+ cc->free_pfn, end_pfn, sync, ret);
+
+ return ret;
+}
+
+static enum compact_result compact_zone_order(struct zone *zone, int order,
+ gfp_t gfp_mask, enum compact_priority prio,
+ unsigned int alloc_flags, int classzone_idx)
+{
+ enum compact_result ret;
+ struct compact_control cc = {
+ .nr_freepages = 0,
+ .nr_migratepages = 0,
+ .total_migrate_scanned = 0,
+ .total_free_scanned = 0,
+ .order = order,
+ .gfp_mask = gfp_mask,
+ .zone = zone,
+ .mode = (prio == COMPACT_PRIO_ASYNC) ?
+ MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
+ .alloc_flags = alloc_flags,
+ .classzone_idx = classzone_idx,
+ .direct_compaction = true,
+ .whole_zone = (prio == MIN_COMPACT_PRIORITY),
+ .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
+ .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
+ };
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ ret = compact_zone(zone, &cc);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+
+ return ret;
+}
+
+int sysctl_extfrag_threshold = 500;
+
+/**
+ * try_to_compact_pages - Direct compact to satisfy a high-order allocation
+ * @gfp_mask: The GFP mask of the current allocation
+ * @order: The order of the current allocation
+ * @alloc_flags: The allocation flags of the current allocation
+ * @ac: The context of current allocation
+ * @prio: Determines how hard direct compaction should try to succeed
+ *
+ * This is the main entry point for direct page compaction.
+ */
+enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
+ unsigned int alloc_flags, const struct alloc_context *ac,
+ enum compact_priority prio)
+{
+ int may_perform_io = gfp_mask & __GFP_IO;
+ struct zoneref *z;
+ struct zone *zone;
+ enum compact_result rc = COMPACT_SKIPPED;
+
+ /*
+ * Check if the GFP flags allow compaction - GFP_NOIO is really
+ * tricky context because the migration might require IO
+ */
+ if (!may_perform_io)
+ return COMPACT_SKIPPED;
+
+ trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
+
+ /* Compact each zone in the list */
+ for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
+ ac->nodemask) {
+ enum compact_result status;
+
+ if (prio > MIN_COMPACT_PRIORITY
+ && compaction_deferred(zone, order)) {
+ rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
+ continue;
+ }
+
+ status = compact_zone_order(zone, order, gfp_mask, prio,
+ alloc_flags, ac_classzone_idx(ac));
+ rc = max(status, rc);
+
+ /* The allocation should succeed, stop compacting */
+ if (status == COMPACT_SUCCESS) {
+ /*
+ * We think the allocation will succeed in this zone,
+ * but it is not certain, hence the false. The caller
+ * will repeat this with true if allocation indeed
+ * succeeds in this zone.
+ */
+ compaction_defer_reset(zone, order, false);
+
+ break;
+ }
+
+ if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
+ status == COMPACT_PARTIAL_SKIPPED))
+ /*
+ * We think that allocation won't succeed in this zone
+ * so we defer compaction there. If it ends up
+ * succeeding after all, it will be reset.
+ */
+ defer_compaction(zone, order);
+
+ /*
+ * We might have stopped compacting due to need_resched() in
+ * async compaction, or due to a fatal signal detected. In that
+ * case do not try further zones
+ */
+ if ((prio == COMPACT_PRIO_ASYNC && need_resched())
+ || fatal_signal_pending(current))
+ break;
+ }
+
+ return rc;
+}
+
+
+/* Compact all zones within a node */
+static void compact_node(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+ int zoneid;
+ struct zone *zone;
+ struct compact_control cc = {
+ .order = -1,
+ .total_migrate_scanned = 0,
+ .total_free_scanned = 0,
+ .mode = MIGRATE_SYNC,
+ .ignore_skip_hint = true,
+ .whole_zone = true,
+ .gfp_mask = GFP_KERNEL,
+ };
+
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+
+ zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ cc.nr_freepages = 0;
+ cc.nr_migratepages = 0;
+ cc.zone = zone;
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ compact_zone(zone, &cc);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+ }
+}
+
+/* Compact all nodes in the system */
+static void compact_nodes(void)
+{
+ int nid;
+
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ for_each_online_node(nid)
+ compact_node(nid);
+}
+
+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
+
+/*
+ * This is the entry point for compacting all nodes via
+ * /proc/sys/vm/compact_memory
+ */
+int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ compact_nodes();
+
+ return 0;
+}
+
+int sysctl_extfrag_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ proc_dointvec_minmax(table, write, buffer, length, ppos);
+
+ return 0;
+}
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+static ssize_t sysfs_compact_node(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int nid = dev->id;
+
+ if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ compact_node(nid);
+ }
+
+ return count;
+}
+static DEVICE_ATTR(compact, 0200, NULL, sysfs_compact_node);
+
+int compaction_register_node(struct node *node)
+{
+ return device_create_file(&node->dev, &dev_attr_compact);
+}
+
+void compaction_unregister_node(struct node *node)
+{
+ return device_remove_file(&node->dev, &dev_attr_compact);
+}
+#endif /* CONFIG_SYSFS && CONFIG_NUMA */
+
+static inline bool kcompactd_work_requested(pg_data_t *pgdat)
+{
+ return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
+}
+
+static bool kcompactd_node_suitable(pg_data_t *pgdat)
+{
+ int zoneid;
+ struct zone *zone;
+ enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
+
+ for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
+ zone = &pgdat->node_zones[zoneid];
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
+ classzone_idx) == COMPACT_CONTINUE)
+ return true;
+ }
+
+ return false;
+}
+
+static void kcompactd_do_work(pg_data_t *pgdat)
+{
+ /*
+ * With no special task, compact all zones so that a page of requested
+ * order is allocatable.
+ */
+ int zoneid;
+ struct zone *zone;
+ struct compact_control cc = {
+ .order = pgdat->kcompactd_max_order,
+ .total_migrate_scanned = 0,
+ .total_free_scanned = 0,
+ .classzone_idx = pgdat->kcompactd_classzone_idx,
+ .mode = MIGRATE_SYNC_LIGHT,
+ .ignore_skip_hint = false,
+ .gfp_mask = GFP_KERNEL,
+ };
+ trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
+ cc.classzone_idx);
+ count_compact_event(KCOMPACTD_WAKE);
+
+ for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
+ int status;
+
+ zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ if (compaction_deferred(zone, cc.order))
+ continue;
+
+ if (compaction_suitable(zone, cc.order, 0, zoneid) !=
+ COMPACT_CONTINUE)
+ continue;
+
+ cc.nr_freepages = 0;
+ cc.nr_migratepages = 0;
+ cc.total_migrate_scanned = 0;
+ cc.total_free_scanned = 0;
+ cc.zone = zone;
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ if (kthread_should_stop())
+ return;
+ status = compact_zone(zone, &cc);
+
+ if (status == COMPACT_SUCCESS) {
+ compaction_defer_reset(zone, cc.order, false);
+ } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
+ /*
+ * Buddy pages may become stranded on pcps that could
+ * otherwise coalesce on the zone's free area for
+ * order >= cc.order. This is ratelimited by the
+ * upcoming deferral.
+ */
+ drain_all_pages(zone);
+
+ /*
+ * We use sync migration mode here, so we defer like
+ * sync direct compaction does.
+ */
+ defer_compaction(zone, cc.order);
+ }
+
+ count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
+ cc.total_migrate_scanned);
+ count_compact_events(KCOMPACTD_FREE_SCANNED,
+ cc.total_free_scanned);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+ }
+
+ /*
+ * Regardless of success, we are done until woken up next. But remember
+ * the requested order/classzone_idx in case it was higher/tighter than
+ * our current ones
+ */
+ if (pgdat->kcompactd_max_order <= cc.order)
+ pgdat->kcompactd_max_order = 0;
+ if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
+ pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
+}
+
+void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ if (!order)
+ return;
+
+ if (pgdat->kcompactd_max_order < order)
+ pgdat->kcompactd_max_order = order;
+
+ if (pgdat->kcompactd_classzone_idx > classzone_idx)
+ pgdat->kcompactd_classzone_idx = classzone_idx;
+
+ /*
+ * Pairs with implicit barrier in wait_event_freezable()
+ * such that wakeups are not missed.
+ */
+ if (!wq_has_sleeper(&pgdat->kcompactd_wait))
+ return;
+
+ if (!kcompactd_node_suitable(pgdat))
+ return;
+
+ trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
+ classzone_idx);
+ wake_up_interruptible(&pgdat->kcompactd_wait);
+}
+
+/*
+ * The background compaction daemon, started as a kernel thread
+ * from the init process.
+ */
+static int kcompactd(void *p)
+{
+ 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);
+
+ set_freezable();
+
+ pgdat->kcompactd_max_order = 0;
+ pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
+
+ while (!kthread_should_stop()) {
+ trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
+ wait_event_freezable(pgdat->kcompactd_wait,
+ kcompactd_work_requested(pgdat));
+
+ kcompactd_do_work(pgdat);
+ }
+
+ return 0;
+}
+
+/*
+ * This kcompactd start function will be called by init and node-hot-add.
+ * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
+ */
+int kcompactd_run(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+ int ret = 0;
+
+ if (pgdat->kcompactd)
+ return 0;
+
+ pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
+ if (IS_ERR(pgdat->kcompactd)) {
+ pr_err("Failed to start kcompactd on node %d\n", nid);
+ ret = PTR_ERR(pgdat->kcompactd);
+ pgdat->kcompactd = NULL;
+ }
+ return ret;
+}
+
+/*
+ * Called by memory hotplug when all memory in a node is offlined. Caller must
+ * hold mem_hotplug_begin/end().
+ */
+void kcompactd_stop(int nid)
+{
+ struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
+
+ if (kcompactd) {
+ kthread_stop(kcompactd);
+ NODE_DATA(nid)->kcompactd = NULL;
+ }
+}
+
+/*
+ * It's optimal to keep kcompactd on the same CPUs as their memory, but
+ * not required for correctness. So if the last cpu in a node goes
+ * away, we get changed to run anywhere: as the first one comes back,
+ * restore their cpu bindings.
+ */
+static int kcompactd_cpu_online(unsigned int cpu)
+{
+ int nid;
+
+ for_each_node_state(nid, N_MEMORY) {
+ pg_data_t *pgdat = NODE_DATA(nid);
+ const struct cpumask *mask;
+
+ mask = cpumask_of_node(pgdat->node_id);
+
+ if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
+ /* One of our CPUs online: restore mask */
+ set_cpus_allowed_ptr(pgdat->kcompactd, mask);
+ }
+ return 0;
+}
+
+static int __init kcompactd_init(void)
+{
+ int nid;
+ int ret;
+
+ ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "mm/compaction:online",
+ kcompactd_cpu_online, NULL);
+ if (ret < 0) {
+ pr_err("kcompactd: failed to register hotplug callbacks.\n");
+ return ret;
+ }
+
+ for_each_node_state(nid, N_MEMORY)
+ kcompactd_run(nid);
+ return 0;
+}
+subsys_initcall(kcompactd_init)
+
+#endif /* CONFIG_COMPACTION */