ufs_getfrag_block(): we only grab ->truncate_mutex on block creation path

BugLink: http://bugs.launchpad.net/bugs/1698799

commit 006351ac upstream.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

fs/ufs/inode.c

@@ -403,7 +403,9 @@ static int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buff
 
 	if (!create) {
 		phys64 = ufs_frag_map(inode, offsets, depth);
-		goto out;
+		if (phys64)
+			map_bh(bh_result, sb, phys64 + frag);
+		return 0;
 	}
 
         /* This code entered only while writing ....? */