xfs: default attr fork size does not handle device inodes

Device inodes have a non-default data fork size of 8 bytes
as checked/enforced by xfs_repair. xfs_default_attroffset() doesn't
handle this, so lets do a minor refactor so it does.

Fixes: e6a688c3 ("xfs: initialise attr fork on inode create")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -195,6 +195,9 @@ xfs_default_attroffset(
 	struct xfs_mount	*mp = ip->i_mount;
 	uint			offset;
 
+	if (ip->i_df.if_format == XFS_DINODE_FMT_DEV)
+		return roundup(sizeof(xfs_dev_t), 8);
+
 	if (mp->m_sb.sb_inodesize == 256)
 		offset = XFS_LITINO(mp) - XFS_BMDR_SPACE_CALC(MINABTPTRS);
 	else
@@ -1038,16 +1041,18 @@ xfs_bmap_set_attrforkoff(
 	int			size,
 	int			*version)
 {
+	int			default_size = xfs_default_attroffset(ip) >> 3;
+
 	switch (ip->i_df.if_format) {
 	case XFS_DINODE_FMT_DEV:
-		ip->i_forkoff = roundup(sizeof(xfs_dev_t), 8) >> 3;
+		ip->i_forkoff = default_size;
 		break;
 	case XFS_DINODE_FMT_LOCAL:
 	case XFS_DINODE_FMT_EXTENTS:
 	case XFS_DINODE_FMT_BTREE:
 		ip->i_forkoff = xfs_attr_shortform_bytesfit(ip, size);
 		if (!ip->i_forkoff)
-			ip->i_forkoff = xfs_default_attroffset(ip) >> 3;
+			ip->i_forkoff = default_size;
 		else if ((ip->i_mount->m_flags & XFS_MOUNT_ATTR2) && version)
 			*version = 2;
 		break;