xfs: force swapext to a realtime file to use the file content exchange ioctl

xfs_swap_extent_rmap does not use log items to track the overall
progress of an attempt to swap the extent mappings between two files.
If the system crashes in the middle of swapping a partially written
realtime extent, the mapping will be left in an inconsistent state
wherein a file can point to multiple extents on the rt volume.

The new file range exchange functionality handles this correctly, so all
callers must upgrade to that.

Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>

Author: Darrick J. Wong

fs/xfs/xfs_bmap_util.c

@@ -1532,6 +1532,18 @@ xfs_swap_extents(
 		goto out_unlock;
 	}
 
+	/*
+	 * The rmapbt implementation is unable to resume a swapext operation
+	 * after a crash if the allocation unit size is larger than a block.
+	 * This (deprecated) interface will not be upgraded to handle this
+	 * situation.  Defragmentation must be performed with the commit range
+	 * ioctl.
+	 */
+	if (XFS_IS_REALTIME_INODE(ip) && xfs_has_rtgroups(ip->i_mount)) {
+		error = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
 	error = xfs_qm_dqattach(ip);
 	if (error)
 		goto out_unlock;