From: Alex Shi alex.shi@linux.alibaba.com
[ Upstream commit 9df41314390b81a541ca6e84c8340bad0959e4b5 ]
Currently, compaction would get the lru_lock and then do page isolation which works fine with pgdat->lru_lock, since any page isoltion would compete for the lru_lock. If we want to change to memcg lru_lock, we have to isolate the page before getting lru_lock, thus isoltion would block page's memcg change which relay on page isoltion too. Then we could safely use per memcg lru_lock later.
The new page isolation use previous introduced TestClearPageLRU() + pgdat lru locking which will be changed to memcg lru lock later.
Hugh Dickins hughd@google.com fixed following bugs in this patch's early version:
Fix lots of crashes under compaction load: isolate_migratepages_block() must clean up appropriately when rejecting a page, setting PageLRU again if it had been cleared; and a put_page() after get_page_unless_zero() cannot safely be done while holding locked_lruvec - it may turn out to be the final put_page(), which will take an lruvec lock when PageLRU.
And move __isolate_lru_page_prepare back after get_page_unless_zero to make trylock_page() safe: trylock_page() is not safe to use at this time: its setting PG_locked can race with the page being freed or allocated ("Bad page"), and can also erase flags being set by one of those "sole owners" of a freshly allocated page who use non-atomic __SetPageFlag().
Link: https://lkml.kernel.org/r/1604566549-62481-16-git-send-email-alex.shi@linux.... Suggested-by: Johannes Weiner hannes@cmpxchg.org Signed-off-by: Alex Shi alex.shi@linux.alibaba.com Acked-by: Hugh Dickins hughd@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Matthew Wilcox willy@infradead.org Cc: Alexander Duyck alexander.duyck@gmail.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: "Chen, Rong A" rong.a.chen@intel.com Cc: Daniel Jordan daniel.m.jordan@oracle.com Cc: "Huang, Ying" ying.huang@intel.com Cc: Jann Horn jannh@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Konstantin Khlebnikov khlebnikov@yandex-team.ru Cc: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@kernel.org Cc: Michal Hocko mhocko@suse.com Cc: Mika Penttilä mika.penttila@nextfour.com Cc: Minchan Kim minchan@kernel.org Cc: Shakeel Butt shakeelb@google.com Cc: Tejun Heo tj@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Wei Yang richard.weiyang@gmail.com Cc: Yang Shi yang.shi@linux.alibaba.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 | 2 +- mm/compaction.c | 42 +++++++++++++++++++++++++++++++++--------- mm/vmscan.c | 43 ++++++++++++++++++++++--------------------- 3 files changed, 56 insertions(+), 31 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h index fbc6805358da..3577d3a6ec37 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -358,7 +358,7 @@ 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 int __isolate_lru_page(struct page *page, isolate_mode_t mode); +extern int __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 8dfbe86bd74f..ba3e907f03b7 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -890,6 +890,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) { if (!cc->ignore_skip_hint && get_pageblock_skip(page)) { low_pfn = end_pfn; + page = NULL; goto isolate_abort; } valid_page = page; @@ -971,6 +972,21 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page)) goto isolate_fail;
+ /* + * 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))) + goto isolate_fail; + + if (__isolate_lru_page_prepare(page, isolate_mode) != 0) + goto isolate_fail_put; + + /* Try isolate the page */ + if (!TestClearPageLRU(page)) + goto isolate_fail_put; + /* If we already hold the lock, we can skip some rechecking */ if (!locked) { locked = compact_lock_irqsave(&pgdat->lru_lock, @@ -983,10 +999,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, goto isolate_abort; }
- /* 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 @@ -994,16 +1006,13 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, */ if (unlikely(PageCompound(page) && !cc->alloc_contig)) { low_pfn += compound_nr(page) - 1; - goto isolate_fail; + SetPageLRU(page); + goto isolate_fail_put; } }
lruvec = mem_cgroup_page_lruvec(page, pgdat);
- /* Try isolate the page */ - if (__isolate_lru_page(page, isolate_mode) != 0) - goto isolate_fail; - /* The whole page is taken off the LRU; skip the tail pages. */ if (PageCompound(page)) low_pfn += compound_nr(page) - 1; @@ -1032,6 +1041,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, }
continue; + +isolate_fail_put: + /* Avoid potential deadlock in freeing page under lru_lock */ + if (locked) { + spin_unlock_irqrestore(&pgdat->lru_lock, flags); + locked = false; + } + put_page(page); + isolate_fail: if (!skip_on_failure) continue; @@ -1068,9 +1086,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (unlikely(low_pfn > end_pfn)) low_pfn = end_pfn;
+ page = NULL; + isolate_abort: if (locked) spin_unlock_irqrestore(&pgdat->lru_lock, flags); + if (page) { + SetPageLRU(page); + put_page(page); + }
/* * Updated the cached scanner pfn once the pageblock has been scanned diff --git a/mm/vmscan.c b/mm/vmscan.c index 8d62eedfc794..5ada402c8d95 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1545,7 +1545,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, * * returns 0 on success, -ve errno on failure. */ -int __isolate_lru_page(struct page *page, isolate_mode_t mode) +int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) { int ret = -EBUSY;
@@ -1597,22 +1597,9 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode) if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) return ret;
- if (likely(get_page_unless_zero(page))) { - /* - * 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 (TestClearPageLRU(page)) - ret = 0; - else - put_page(page); - } - - return ret; + return 0; }
- /* * Update LRU sizes after isolating pages. The LRU size updates must * be complete before mem_cgroup_update_lru_size due to a sanity check. @@ -1692,20 +1679,34 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, * only when the page is being freed somewhere else. */ scan += nr_pages; - switch (__isolate_lru_page(page, mode)) { + switch (__isolate_lru_page_prepare(page, mode)) { case 0: + /* + * 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))) + goto busy; + + if (!TestClearPageLRU(page)) { + /* + * This page may in other isolation path, + * but we still hold lru_lock. + */ + put_page(page); + goto busy; + } + nr_taken += nr_pages; nr_zone_taken[page_zonenum(page)] += nr_pages; list_move(&page->lru, dst); break;
- case -EBUSY: + default: +busy: /* else it is being freed elsewhere */ list_move(&page->lru, src); - continue; - - default: - BUG(); } }