Commits
Jan Kara committed 47e20933814
mm/filemap.c: don't bother dropping mmap_sem for zero size readahead commit 5c72feee3e45b40a3c96c7145ec422899d0e8964 upstream. When handling a page fault, we drop mmap_sem to start async readahead so that we don't block on IO submission with mmap_sem held. However there's no point to drop mmap_sem in case readahead is disabled. Handle that case to avoid pointless dropping of mmap_sem and retrying the fault. This was actually reported to block mlockall(MCL_CURRENT) indefinitely. Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations") Reported-by: Minchan Kim <minchan@kernel.org> Reported-by: Robert Stupp <snazy@gmx.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Link: http://lkml.kernel.org/r/20200212101356.30759-1-jack@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: SeongJae Park <sjpark@amazon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>