xfs: ensure unlinked list state is consistent with nlink during scrub

Now that we have the means to tell if an inode is on an unlinked inode
list or not, we can check that an inode with zero link count is on the
unlinked list; and an inode that has nonzero link count is not on that
list.  Make repair clean things up too.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/inode.c

@@ -739,6 +739,23 @@ xchk_inode_check_reflink_iflag(
 		xchk_ino_set_corrupt(sc, ino);
 }
 
+/*
+ * If this inode has zero link count, it must be on the unlinked list.  If
+ * it has nonzero link count, it must not be on the unlinked list.
+ */
+STATIC void
+xchk_inode_check_unlinked(
+	struct xfs_scrub	*sc)
+{
+	if (VFS_I(sc->ip)->i_nlink == 0) {
+		if (!xfs_inode_on_unlinked_list(sc->ip))
+			xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+	} else {
+		if (xfs_inode_on_unlinked_list(sc->ip))
+			xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+	}
+}
+
 /* Scrub an inode. */
 int
 xchk_inode(
@@ -771,6 +788,8 @@ xchk_inode(
 	if (S_ISREG(VFS_I(sc->ip)->i_mode))
 		xchk_inode_check_reflink_iflag(sc, sc->ip->i_ino);
 
+	xchk_inode_check_unlinked(sc);
+
 	xchk_inode_xref(sc, sc->ip->i_ino, &di);
 out:
 	return error;

fs/xfs/scrub/inode_repair.c

@@ -1745,6 +1745,46 @@ xrep_inode_problems(
 	return xrep_roll_trans(sc);
 }
 
+/*
+ * Make sure this inode's unlinked list pointers are consistent with its
+ * link count.
+ */
+STATIC int
+xrep_inode_unlinked(
+	struct xfs_scrub	*sc)
+{
+	unsigned int		nlink = VFS_I(sc->ip)->i_nlink;
+	int			error;
+
+	/*
+	 * If this inode is linked from the directory tree and on the unlinked
+	 * list, remove it from the unlinked list.
+	 */
+	if (nlink > 0 && xfs_inode_on_unlinked_list(sc->ip)) {
+		struct xfs_perag	*pag;
+		int			error;
+
+		pag = xfs_perag_get(sc->mp,
+				XFS_INO_TO_AGNO(sc->mp, sc->ip->i_ino));
+		error = xfs_iunlink_remove(sc->tp, pag, sc->ip);
+		xfs_perag_put(pag);
+		if (error)
+			return error;
+	}
+
+	/*
+	 * If this inode is not linked from the directory tree yet not on the
+	 * unlinked list, put it on the unlinked list.
+	 */
+	if (nlink == 0 && !xfs_inode_on_unlinked_list(sc->ip)) {
+		error = xfs_iunlink(sc->tp, sc->ip);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
 /* Repair an inode's fields. */
 int
 xrep_inode(
@@ -1794,5 +1834,10 @@ xrep_inode(
 			return error;
 	}
 
+	/* Reconnect incore unlinked list */
+	error = xrep_inode_unlinked(sc);
+	if (error)
+		return error;
+
 	return xrep_defer_finish(sc);
 }

fs/xfs/xfs_inode.c

@@ -42,9 +42,6 @@
 
 struct kmem_cache *xfs_inode_cache;
 
-STATIC int xfs_iunlink_remove(struct xfs_trans *tp, struct xfs_perag *pag,
-	struct xfs_inode *);
-
 /*
  * helper function to extract extent size hint from inode
  */
@@ -2252,7 +2249,7 @@ xfs_iunlink_remove_inode(
 /*
  * Pull the on-disk inode from the AGI unlinked list.
  */
-STATIC int
+int
 xfs_iunlink_remove(
 	struct xfs_trans	*tp,
 	struct xfs_perag	*pag,

fs/xfs/xfs_inode.h

@@ -617,6 +617,8 @@ extern struct kmem_cache	*xfs_inode_cache;
 bool xfs_inode_needs_inactive(struct xfs_inode *ip);
 
 int xfs_iunlink(struct xfs_trans *tp, struct xfs_inode *ip);
+int xfs_iunlink_remove(struct xfs_trans *tp, struct xfs_perag *pag,
+		struct xfs_inode *ip);
 
 void xfs_end_io(struct work_struct *work);