Commit 0e267c44 authored Jul 02, 2013 by Josef Bacik

Btrfs: wait ordered range before doing direct io

My recent truncate patch uncovered this bug, but I can reproduce it without the
truncate patch. If you mount with -o compress-force, do a direct write to some
area, do a buffered write to some other area, and then do a direct read you will
get the wrong data for where you did the buffered write. This is because the
generic direct io helpers only call filemap_write_and_wait once, and for
compression we need it twice. So to be safe add the btrfs_wait_ordered_range to
the start of the direct io function to make sure any compressed writes have
truly been written. This patch makes xfstests 130 pass when you mount with -o
compress-force=lzo. Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

parent 7fb7d76f

fs/btrfs/inode.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -7270,8 +7270,16 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
		atomic_inc(&inode->i_dio_count);
		smp_mb__after_atomic_inc();

		if (rw & WRITE) {
		/*
		* The generic stuff only does filemap_write_and_wait_range, which isn't
		* enough if we've written compressed pages to this area, so we need to
		* call btrfs_wait_ordered_range to make absolutely sure that any
		* outstanding dirty pages are on disk.
		*/
		count = iov_length(iov, nr_segs);
		btrfs_wait_ordered_range(inode, offset, count);

		if (rw & WRITE) {
		/*
		* If the write DIO is beyond the EOF, we need update
		* the isize, but it is protected by i_mutex. So we can