Reflink should force the log out to disk if the filesystem was mounted
with wsync, the same as most other operations in xfs.

[Note: XFS_MOUNT_WSYNC is set when the admin mounts the filesystem
with either the 'wsync' or 'sync' mount options, which effectively means
that we're classifying reflink/dedupe as IO operations and making them
synchronous when required.]

Fixes: 3fc9f5e4 ("xfs: remove xfs_reflink_remap_range")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
[darrick: add more to the changelog]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>