xfs: factor out dir2 data block reading

And add a verifier callback function while there.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Phil White <pwhite@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_dir2_block.c b/fs/xfs/xfs_dir2_block.c
index 57351b8..ca03b10 100644
--- a/fs/xfs/xfs_dir2_block.c
+++ b/fs/xfs/xfs_dir2_block.c
@@ -970,8 +970,7 @@
 	 * Read the data block if we don't already have it, give up if it fails.
 	 */
 	if (!dbp) {
-		error = xfs_da_read_buf(tp, dp, mp->m_dirdatablk, -1, &dbp,
-					XFS_DATA_FORK, NULL);
+		error = xfs_dir2_data_read(tp, dp, mp->m_dirdatablk, -1, &dbp);
 		if (error)
 			return error;
 	}