Use invalidate_lock instead of f2fs' private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we fix a long standing
race between hole punching and read(2) / readahead(2) paths that can
lead to stale page cache contents.
CC: Jaegeuk Kim <jaegeuk@kernel.org> CC: Chao Yu <yuchao0@huawei.com> CC: linux-f2fs-devel@lists.sourceforge.net Acked-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz>