xfs: refactor directory tree root predicates

Metadata directory trees make reasoning about the parent of a file more
difficult.  Traditionally, user files are children of sb_rootino, and
metadata files are "children" of the superblock.  Now, we add a third
possibility -- some metadata files can be children of sb_metadirino, but
the classic ones (rt free space data and quotas) are left alone.

Let's add some helper functions (instead of open-coding the logic
everywhere) to make scrub logic easier to understand.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/common.c

@@ -1452,3 +1452,32 @@ xchk_inode_is_allocated(
 	rcu_read_unlock();
 	return error;
 }
+
+/* Is this inode a root directory for either tree? */
+bool
+xchk_inode_is_dirtree_root(const struct xfs_inode *ip)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+
+	return ip == mp->m_rootip ||
+		(xfs_has_metadir(mp) && ip == mp->m_metadirip);
+}
+
+/* Does the superblock point down to this inode? */
+bool
+xchk_inode_is_sb_rooted(const struct xfs_inode *ip)
+{
+	return xchk_inode_is_dirtree_root(ip) ||
+	       xfs_is_sb_inum(ip->i_mount, ip->i_ino);
+}
+
+/* What is the root directory inumber for this inode? */
+xfs_ino_t
+xchk_inode_rootdir_inum(const struct xfs_inode *ip)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+
+	if (xfs_is_metadir_inode(ip))
+		return mp->m_metadirip->i_ino;
+	return mp->m_rootip->i_ino;
+}

fs/xfs/scrub/common.h

@@ -242,4 +242,8 @@ void xchk_fsgates_enable(struct xfs_scrub *sc, unsigned int scrub_fshooks);
 int xchk_inode_is_allocated(struct xfs_scrub *sc, xfs_agino_t agino,
 		bool *inuse);
 
+bool xchk_inode_is_dirtree_root(const struct xfs_inode *ip);
+bool xchk_inode_is_sb_rooted(const struct xfs_inode *ip);
+xfs_ino_t xchk_inode_rootdir_inum(const struct xfs_inode *ip);
+
 #endif	/* __XFS_SCRUB_COMMON_H__ */

fs/xfs/scrub/dir.c

@@ -253,7 +253,7 @@ xchk_dir_actor(
 		 * If this is ".." in the root inode, check that the inum
 		 * matches this dir.
 		 */
-		if (dp->i_ino == mp->m_sb.sb_rootino && ino != dp->i_ino)
+		if (xchk_inode_is_dirtree_root(dp) && ino != dp->i_ino)
 			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 	}
 

fs/xfs/scrub/dir_repair.c

@@ -1270,7 +1270,7 @@ xrep_dir_scan_dirtree(
 	int			error;
 
 	/* Roots of directory trees are their own parents. */
-	if (sc->ip == sc->mp->m_rootip)
+	if (xchk_inode_is_dirtree_root(sc->ip))
 		xrep_findparent_scan_found(&rd->pscan, sc->ip->i_ino);
 
 	/*

fs/xfs/scrub/dirtree.c

@@ -917,7 +917,7 @@ xchk_dirtree(
 	 * scan, because the hook doesn't detach until after sc->ip gets
 	 * released during teardown.
 	 */
-	dl->root_ino = sc->mp->m_rootip->i_ino;
+	dl->root_ino = xchk_inode_rootdir_inum(sc->ip);
 	dl->scan_ino = sc->ip->i_ino;
 
 	trace_xchk_dirtree_start(sc->ip, sc->sm, 0);
@@ -983,3 +983,16 @@ xchk_dirtree(
 	trace_xchk_dirtree_done(sc->ip, sc->sm, error);
 	return error;
 }
+
+/* Does the directory targetted by this scrub have no parents? */
+bool
+xchk_dirtree_parentless(const struct xchk_dirtree *dl)
+{
+	struct xfs_scrub	*sc = dl->sc;
+
+	if (xchk_inode_is_dirtree_root(sc->ip))
+		return true;
+	if (VFS_I(sc->ip)->i_nlink == 0)
+		return true;
+	return false;
+}

fs/xfs/scrub/dirtree.h

@@ -156,17 +156,7 @@ struct xchk_dirtree {
 #define xchk_dirtree_for_each_path(dl, path) \
 	list_for_each_entry((path), &(dl)->path_list, list)
 
-static inline bool
-xchk_dirtree_parentless(const struct xchk_dirtree *dl)
-{
-	struct xfs_scrub	*sc = dl->sc;
-
-	if (sc->ip == sc->mp->m_rootip)
-		return true;
-	if (VFS_I(sc->ip)->i_nlink == 0)
-		return true;
-	return false;
-}
+bool xchk_dirtree_parentless(const struct xchk_dirtree *dl);
 
 int xchk_dirtree_find_paths_to_root(struct xchk_dirtree *dl);
 int xchk_dirpath_append(struct xchk_dirtree *dl, struct xfs_inode *ip,

fs/xfs/scrub/findparent.c

@@ -362,15 +362,18 @@ xrep_findparent_confirm(
 	};
 	int			error;
 
-	/*
-	 * The root directory always points to itself.  Unlinked dirs can point
-	 * anywhere, so we point them at the root dir too.
-	 */
-	if (sc->ip == sc->mp->m_rootip || VFS_I(sc->ip)->i_nlink == 0) {
+	/* The root directory always points to itself. */
+	if (sc->ip == sc->mp->m_rootip) {
 		*parent_ino = sc->mp->m_sb.sb_rootino;
 		return 0;
 	}
 
+	/* Unlinked dirs can point anywhere; point them up to the root dir. */
+	if (VFS_I(sc->ip)->i_nlink == 0) {
+		*parent_ino = xchk_inode_rootdir_inum(sc->ip);
+		return 0;
+	}
+
 	/* Reject garbage parent inode numbers and self-referential parents. */
 	if (*parent_ino == NULLFSINO)
 	       return 0;
@@ -413,7 +416,7 @@ xrep_findparent_self_reference(
 		return sc->mp->m_sb.sb_rootino;
 
 	if (VFS_I(sc->ip)->i_nlink == 0)
-		return sc->mp->m_sb.sb_rootino;
+		return xchk_inode_rootdir_inum(sc->ip);
 
 	return NULLFSINO;
 }

fs/xfs/scrub/inode_repair.c

@@ -1767,15 +1767,8 @@ xrep_inode_pptr(
 	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_internal_inode(ip))
+	/* Children of the superblock do not have parent pointers. */
+	if (xchk_inode_is_sb_rooted(ip))
 		return 0;
 
 	/* Inode already has an attr fork; no further work possible here. */

fs/xfs/scrub/nlinks.c

@@ -279,7 +279,7 @@ xchk_nlinks_collect_dirent(
 	 * determine the backref count.
 	 */
 	if (dotdot) {
-		if (dp == sc->mp->m_rootip)
+		if (xchk_inode_is_dirtree_root(dp))
 			error = xchk_nlinks_update_incore(xnc, ino, 1, 0, 0);
 		else if (!xfs_has_parent(sc->mp))
 			error = xchk_nlinks_update_incore(xnc, ino, 0, 1, 0);
@@ -735,7 +735,7 @@ xchk_nlinks_compare_inode(
 		}
 	}
 
-	if (ip == sc->mp->m_rootip) {
+	if (xchk_inode_is_dirtree_root(ip)) {
 		/*
 		 * For the root of a directory tree, both the '.' and '..'
 		 * entries should point to the root directory.  The dotdot

fs/xfs/scrub/nlinks_repair.c

@@ -60,11 +60,9 @@ xrep_nlinks_is_orphaned(
 	unsigned int		actual_nlink,
 	const struct xchk_nlink	*obs)
 {
-	struct xfs_mount	*mp = ip->i_mount;
-
 	if (obs->parents != 0)
 		return false;
-	if (ip == mp->m_rootip || ip == sc->orphanage)
+	if (xchk_inode_is_dirtree_root(ip) || ip == sc->orphanage)
 		return false;
 	return actual_nlink != 0;
 }

fs/xfs/scrub/orphanage.c

@@ -295,7 +295,9 @@ xrep_orphanage_can_adopt(
 		return false;
 	if (sc->ip == sc->orphanage)
 		return false;
-	if (xfs_is_sb_inum(sc->mp, sc->ip->i_ino))
+	if (xchk_inode_is_sb_rooted(sc->ip))
+		return false;
+	if (xfs_is_internal_inode(sc->ip))
 		return false;
 	return true;
 }

fs/xfs/scrub/parent.c

@@ -300,7 +300,7 @@ xchk_parent_pptr_and_dotdot(
 	}
 
 	/* Is this the root dir?  Then '..' must point to itself. */
-	if (sc->ip == sc->mp->m_rootip) {
+	if (xchk_inode_is_dirtree_root(sc->ip)) {
 		if (sc->ip->i_ino != pp->parent_ino)
 			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
 		return 0;
@@ -711,7 +711,7 @@ xchk_parent_count_pptrs(
 	}
 
 	if (S_ISDIR(VFS_I(sc->ip)->i_mode)) {
-		if (sc->ip == sc->mp->m_rootip)
+		if (xchk_inode_is_dirtree_root(sc->ip))
 			pp->pptrs_found++;
 
 		if (VFS_I(sc->ip)->i_nlink == 0 && pp->pptrs_found > 0)
@@ -885,10 +885,9 @@ bool
 xchk_pptr_looks_zapped(
 	struct xfs_inode	*ip)
 {
-	struct xfs_mount	*mp = ip->i_mount;
 	struct inode		*inode = VFS_I(ip);
 
-	ASSERT(xfs_has_parent(mp));
+	ASSERT(xfs_has_parent(ip->i_mount));
 
 	/*
 	 * Temporary files that cannot be linked into the directory tree do not
@@ -902,15 +901,15 @@ xchk_pptr_looks_zapped(
 	 * of a parent pointer scan is always the empty set.  It's safe to scan
 	 * them even if the attr fork was zapped.
 	 */
-	if (ip == mp->m_rootip)
+	if (xchk_inode_is_dirtree_root(ip))
 		return false;
 
 	/*
-	 * Metadata inodes are all rooted in the superblock and do not have
-	 * any parents.  Hence the attr fork will not be initialized, but
-	 * there are no parent pointers that might have been zapped.
+	 * Metadata inodes that are rooted in the superblock do not have any
+	 * parents.  Hence the attr fork will not be initialized, but there are
+	 * no parent pointers that might have been zapped.
 	 */
-	if (xfs_is_internal_inode(ip))
+	if (xchk_inode_is_sb_rooted(ip))
 		return false;
 
 	/*

fs/xfs/scrub/parent_repair.c

@@ -1334,7 +1334,7 @@ xrep_parent_rebuild_pptrs(
 	 * so that we can decide if we're moving this file to the orphanage.
 	 * For this purpose, root directories are their own parents.
 	 */
-	if (sc->ip == sc->mp->m_rootip) {
+	if (xchk_inode_is_dirtree_root(sc->ip)) {
 		xrep_findparent_scan_found(&rp->pscan, sc->ip->i_ino);
 	} else {
 		error = xrep_parent_lookup_pptrs(sc, &parent_ino);