xfs: inode repair should ensure there's an attr fork to store parent pointers

The runtime parent pointer update code expects that any file being moved
around the directory tree already has an attr fork.  However, if we had
to rebuild an inode core record, there's a chance that we zeroed forkoff
as part of the inode to pass the iget verifiers.

Therefore, if we performed any repairs on an inode core, ensure that the
inode has a nonzero forkoff before unlocking the inode.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/inode_repair.c

@@ -1736,6 +1736,44 @@ xrep_inode_extsize(
 	}
 }
 
+/* Ensure this file has an attr fork if it needs to hold a parent pointer. */
+STATIC int
+xrep_inode_pptr(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_mount	*mp = sc->mp;
+	struct xfs_inode	*ip = sc->ip;
+	struct inode		*inode = VFS_I(ip);
+
+	if (!xfs_has_parent(mp))
+		return 0;
+
+	/*
+	 * Unlinked inodes that cannot be added to the directory tree will not
+	 * have a parent pointer.
+	 */
+	if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
+		return 0;
+
+	/* The root directory doesn't have a parent pointer. */
+	if (ip == mp->m_rootip)
+		return 0;
+
+	/*
+	 * Metadata inodes are rooted in the superblock and do not have any
+	 * parents.
+	 */
+	if (xfs_is_metadata_inode(ip))
+		return 0;
+
+	/* Inode already has an attr fork; no further work possible here. */
+	if (xfs_inode_has_attr_fork(ip))
+		return 0;
+
+	return xfs_bmap_add_attrfork(sc->tp, ip,
+			sizeof(struct xfs_attr_sf_hdr), true);
+}
+
 /* Fix any irregularities in an inode that the verifiers don't catch. */
 STATIC int
 xrep_inode_problems(
@@ -1744,6 +1782,9 @@ xrep_inode_problems(
 	int			error;
 
 	error = xrep_inode_blockcounts(sc);
+	if (error)
+		return error;
+	error = xrep_inode_pptr(sc);
 	if (error)
 		return error;
 	xrep_inode_timestamps(sc->ip);