tree 11d7854acb61128821b948796d1eb2e2f87b925f
parent 17048e8a083fec7ad841d88ef0812707fbc7e39f
author Jan Kara <jack@suse.com> 1449516671 -0500
committer Theodore Ts'o <tytso@mit.edu> 1449516671 -0500

ext4: fix races between buffered IO and collapse / insert range

Current code implementing FALLOC_FL_COLLAPSE_RANGE and
FALLOC_FL_INSERT_RANGE is prone to races with buffered writes and page
faults. If buffered write or write via mmap manages to squeeze between
filemap_write_and_wait_range() and truncate_pagecache() in the fallocate
implementations, the written data is simply discarded by
truncate_pagecache() although it should have been shifted.

Fix the problem by moving filemap_write_and_wait_range() call inside
i_mutex and i_mmap_sem. That way we are protected against races with
both buffered writes and page faults.

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>