From e0975b2aae0e669f995f7d5f11db25c3080ae11c Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Fri, 28 Dec 2018 00:38:36 -0800 Subject: mm, fault_around: do not take a reference to a locked page filemap_map_pages takes a speculative reference to each page in the range before it tries to lock that page. While this is correct it also can influence page migration which will bail out when seeing an elevated reference count. The faultaround code would bail on seeing a locked page so we can pro-actively check the PageLocked bit before page_cache_get_speculative and prevent from pointless reference count churn. Link: http://lkml.kernel.org/r/20181211142741.2607-4-mhocko@kernel.org Signed-off-by: Michal Hocko Suggested-by: Jan Kara Acked-by: Kirill A. Shutemov Reviewed-by: David Hildenbrand Acked-by: Hugh Dickins Reviewed-by: William Kucharski Cc: Oscar Salvador Cc: Pavel Tatashin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index 8cec52968e83..29655fb47a2c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2614,6 +2614,13 @@ void filemap_map_pages(struct vm_fault *vmf, goto next; head = compound_head(page); + + /* + * Check for a locked page first, as a speculative + * reference may adversely influence page migration. + */ + if (PageLocked(head)) + goto next; if (!page_cache_get_speculative(head)) goto next; -- cgit v1.2.3-55-g7522