xfs: fix flags argument to rmap lookup when converting shared file rmaps

Pass the same oldext argument (which contains the existing rmapping's
unwritten state) to xfs_rmap_lookup_le_range at the start of
xfs_rmap_convert_shared.  At this point in the code, flags is zero,
which means that we perform lookups using the wrong key.

Fixes: 3f165b334e ("xfs: convert unwritten status of reverse mappings for shared files")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_rmap.c

@@ -1514,7 +1514,7 @@ xfs_rmap_convert_shared(
 	 * record for our insertion point. This will also give us the record for
 	 * start block contiguity tests.
 	 */
-	error = xfs_rmap_lookup_le_range(cur, bno, owner, offset, flags,
+	error = xfs_rmap_lookup_le_range(cur, bno, owner, offset, oldext,
 			&PREV, &i);
 	if (error)
 		goto done;