From 6aeff241fe6c4561a842b344c1ca14a700ec8441 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Mon, 6 Apr 2020 20:04:21 -0700 Subject: [PATCH] mm/migrate.c: migrate PG_readahead flag Currently the migration code doesn't migrate PG_readahead flag. Theoretically this would incur slight performance loss as the application might have to ramp its readahead back up again. Even though such problem happens, it might be hidden by something else since migration is typically triggered by compaction and NUMA balancing, any of which should be more noticeable. Migrate the flag after end_page_writeback() since it may clear PG_reclaim flag, which is the same bit as PG_readahead, for the new page. [akpm@linux-foundation.org: tweak comment] Signed-off-by: Yang Shi Signed-off-by: Andrew Morton Cc: Matthew Wilcox Cc: Michal Hocko Cc: Mel Gorman Link: http://lkml.kernel.org/r/1581640185-95731-1-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Linus Torvalds --- mm/migrate.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/migrate.c b/mm/migrate.c index c550230664b1..1a205503be3f 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -647,6 +647,14 @@ void migrate_page_states(struct page *newpage, struct page *page) if (PageWriteback(newpage)) end_page_writeback(newpage); + /* + * PG_readahead shares the same bit with PG_reclaim. The above + * end_page_writeback() may clear PG_readahead mistakenly, so set the + * bit after that. + */ + if (PageReadahead(page)) + SetPageReadahead(newpage); + copy_page_owner(page, newpage); mem_cgroup_migrate(page, newpage); -- 2.30.2