From: Hugh Dickins hughd@google.com
[ Upstream commit 89f6c88a6ab4a11deb14c270f7f1454cda4f73d6 ]
__isolate_lru_page_prepare() conflates two unrelated functions, with the flags to one disjoint from the flags to the other; and hides some of the important checks outside of isolate_migratepages_block(), where the sequence is better to be visible. It comes from the days of lumpy reclaim, before compaction, when the combination made more sense.
Move what's needed by mm/compaction.c isolate_migratepages_block() inline there, and what's needed by mm/vmscan.c isolate_lru_pages() inline there.
Shorten "isolate_mode" to "mode", so the sequence of conditions is easier to read. Declare a "mapping" variable, to save one call to page_mapping() (but not another: calling again after page is locked is necessary). Simplify isolate_lru_pages() with a "move_to" list pointer.
Link: https://lkml.kernel.org/r/879d62a8-91cc-d3c6-fb3b-69768236df68@google.com Signed-off-by: Hugh Dickins hughd@google.com Acked-by: David Rientjes rientjes@google.com Reviewed-by: Alex Shi alexs@kernel.org Cc: Alexander Duyck alexander.duyck@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Stable-dep-of: 829ae0f81ce0 ("mm: migrate: fix THP's mapcount on isolation") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/swap.h | 1 - mm/compaction.c | 51 +++++++++++++++++++--- mm/vmscan.c | 101 ++++++++----------------------------------- 3 files changed, 62 insertions(+), 91 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h index 394d5de5d4b4..a502928c29c5 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -358,7 +358,6 @@ extern void lru_cache_add_inactive_or_unevictable(struct page *page, extern unsigned long zone_reclaimable_pages(struct zone *zone); extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *mask); -extern bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode); extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, unsigned long nr_pages, gfp_t gfp_mask, diff --git a/mm/compaction.c b/mm/compaction.c index ea46aadc7c21..57ce6b001b10 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -784,7 +784,7 @@ static bool too_many_isolated(pg_data_t *pgdat) * @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. + * @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. @@ -798,7 +798,7 @@ static bool too_many_isolated(pg_data_t *pgdat) */ static unsigned long isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, - unsigned long end_pfn, isolate_mode_t isolate_mode) + unsigned long end_pfn, isolate_mode_t mode) { pg_data_t *pgdat = cc->zone->zone_pgdat; unsigned long nr_scanned = 0, nr_isolated = 0; @@ -806,6 +806,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, unsigned long flags = 0; bool locked = false; struct page *page = NULL, *valid_page = NULL; + struct address_space *mapping; unsigned long start_pfn = low_pfn; bool skip_on_failure = false; unsigned long next_skip_pfn = 0; @@ -949,7 +950,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, locked = false; }
- if (!isolate_movable_page(page, isolate_mode)) + if (!isolate_movable_page(page, mode)) goto isolate_success; }
@@ -961,15 +962,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, * so avoid taking lru_lock and isolating it unnecessarily in an * admittedly racy check. */ - if (!page_mapping(page) && - page_count(page) > page_mapcount(page)) + mapping = page_mapping(page); + if (!mapping && 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)) + if (!(cc->gfp_mask & __GFP_FS) && mapping) goto isolate_fail;
/* @@ -980,9 +981,45 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (unlikely(!get_page_unless_zero(page))) goto isolate_fail;
- if (!__isolate_lru_page_prepare(page, isolate_mode)) + /* Only take pages on LRU: a check now makes later tests safe */ + if (!PageLRU(page)) + goto isolate_fail_put; + + /* Compaction might skip unevictable pages but CMA takes them */ + if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page)) + goto isolate_fail_put; + + /* + * To minimise LRU disruption, the caller can indicate with + * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages + * it will be able to migrate without blocking - clean pages + * for the most part. PageWriteback would require blocking. + */ + if ((mode & ISOLATE_ASYNC_MIGRATE) && PageWriteback(page)) goto isolate_fail_put;
+ if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) { + bool migrate_dirty; + + /* + * Only pages without mappings or that have a + * ->migratepage callback are possible to migrate + * without blocking. However, we can be racing with + * truncation so it's necessary to lock the page + * to stabilise the mapping as truncation holds + * the page lock until after the page is removed + * from the page cache. + */ + if (!trylock_page(page)) + goto isolate_fail_put; + + mapping = page_mapping(page); + migrate_dirty = !mapping || mapping->a_ops->migratepage; + unlock_page(page); + if (!migrate_dirty) + goto isolate_fail_put; + } + /* Try isolate the page */ if (!TestClearPageLRU(page)) goto isolate_fail_put; diff --git a/mm/vmscan.c b/mm/vmscan.c index 00a47845a15b..9cba0f890b33 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1535,69 +1535,6 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, return nr_reclaimed; }
-/* - * Attempt to remove the specified page from its LRU. Only take this page - * if it is of the appropriate PageActive status. Pages which are being - * freed elsewhere are also ignored. - * - * page: page to consider - * mode: one of the LRU isolation modes defined above - * - * returns true on success, false on failure. - */ -bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) -{ - /* Only take pages on the LRU. */ - if (!PageLRU(page)) - return false; - - /* Compaction should not handle unevictable pages but CMA can do so */ - if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) - return false; - - /* - * To minimise LRU disruption, the caller can indicate that it only - * wants to isolate pages it will be able to operate on without - * blocking - clean pages for the most part. - * - * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages - * that it is possible to migrate without blocking - */ - if (mode & ISOLATE_ASYNC_MIGRATE) { - /* All the caller can do on PageWriteback is block */ - if (PageWriteback(page)) - return false; - - if (PageDirty(page)) { - struct address_space *mapping; - bool migrate_dirty; - - /* - * Only pages without mappings or that have a - * ->migratepage callback are possible to migrate - * without blocking. However, we can be racing with - * truncation so it's necessary to lock the page - * to stabilise the mapping as truncation holds - * the page lock until after the page is removed - * from the page cache. - */ - if (!trylock_page(page)) - return false; - - mapping = page_mapping(page); - migrate_dirty = !mapping || mapping->a_ops->migratepage; - unlock_page(page); - if (!migrate_dirty) - return false; - } - } - - if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) - return false; - - return true; -} - /* * Update LRU sizes after isolating pages. The LRU size updates must * be complete before mem_cgroup_update_lru_size due to a sanity check. @@ -1647,11 +1584,11 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, unsigned long skipped = 0; unsigned long scan, total_scan, nr_pages; LIST_HEAD(pages_skipped); - isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED);
total_scan = 0; scan = 0; while (scan < nr_to_scan && !list_empty(src)) { + struct list_head *move_to = src; struct page *page;
page = lru_to_page(src); @@ -1661,9 +1598,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, total_scan += nr_pages;
if (page_zonenum(page) > sc->reclaim_idx) { - list_move(&page->lru, &pages_skipped); nr_skipped[page_zonenum(page)] += nr_pages; - continue; + move_to = &pages_skipped; + goto move; }
/* @@ -1671,37 +1608,34 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, * return with no isolated pages if the LRU mostly contains * ineligible pages. This causes the VM to not reclaim any * pages, triggering a premature OOM. - * - * Account all tail pages of THP. This would not cause - * premature OOM since __isolate_lru_page() returns -EBUSY - * only when the page is being freed somewhere else. + * Account all tail pages of THP. */ scan += nr_pages; - if (!__isolate_lru_page_prepare(page, mode)) { - /* It is being freed elsewhere */ - list_move(&page->lru, src); - continue; - } + + if (!PageLRU(page)) + goto move; + if (!sc->may_unmap && page_mapped(page)) + goto move; + /* * Be careful not to clear PageLRU until after we're * sure the page is not being freed elsewhere -- the * page release code relies on it. */ - if (unlikely(!get_page_unless_zero(page))) { - list_move(&page->lru, src); - continue; - } + if (unlikely(!get_page_unless_zero(page))) + goto move;
if (!TestClearPageLRU(page)) { /* Another thread is already isolating this page */ put_page(page); - list_move(&page->lru, src); - continue; + goto move; }
nr_taken += nr_pages; nr_zone_taken[page_zonenum(page)] += nr_pages; - list_move(&page->lru, dst); + move_to = dst; +move: + list_move(&page->lru, move_to); }
/* @@ -1725,7 +1659,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, } *nr_scanned = total_scan; trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, - total_scan, skipped, nr_taken, mode, lru); + total_scan, skipped, nr_taken, + sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru); update_lru_sizes(lruvec, lru, nr_zone_taken); return nr_taken; }