From 8d8869ca5d2d9d86db96271ab063fdcfa9baf5b4 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 18 Sep 2020 21:20:12 -0700 Subject: mm: fix check_move_unevictable_pages() on THP check_move_unevictable_pages() is used in making unevictable shmem pages evictable: by shmem_unlock_mapping(), drm_gem_check_release_pagevec() and i915/gem check_release_pagevec(). Those may pass down subpages of a huge page, when /sys/kernel/mm/transparent_hugepage/shmem_enabled is "force". That does not crash or warn at present, but the accounting of vmstats unevictable_pgs_scanned and unevictable_pgs_rescued is inconsistent: scanned being incremented on each subpage, rescued only on the head (since tails already appear evictable once the head has been updated). 5.8 commit 5d91f31faf8e ("mm: swap: fix vmstats for huge page") has established that vm_events in general (and unevictable_pgs_rescued in particular) should count every subpage: so follow that precedent here. Do this in such a way that if mem_cgroup_page_lruvec() is made stricter (to check page->mem_cgroup is always set), no problem: skip the tails before calling it, and add thp_nr_pages() to vmstats on the head. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Acked-by: Yang Shi Cc: Johannes Weiner Cc: Michal Hocko Cc: Mike Kravetz Cc: Qian Cai Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008301405000.5954@eggly.anvils Signed-off-by: Linus Torvalds --- mm/vmscan.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 9727dd8e2581..466fc3144fff 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4268,8 +4268,14 @@ void check_move_unevictable_pages(struct pagevec *pvec) for (i = 0; i < pvec->nr; i++) { struct page *page = pvec->pages[i]; struct pglist_data *pagepgdat = page_pgdat(page); + int nr_pages; + + if (PageTransTail(page)) + continue; + + nr_pages = thp_nr_pages(page); + pgscanned += nr_pages; - pgscanned++; if (pagepgdat != pgdat) { if (pgdat) spin_unlock_irq(&pgdat->lru_lock); @@ -4288,7 +4294,7 @@ void check_move_unevictable_pages(struct pagevec *pvec) ClearPageUnevictable(page); del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); add_page_to_lru_list(page, lruvec, lru); - pgrescued++; + pgrescued += nr_pages; } } -- cgit v1.2.3-58-ga151