xfs: ask the dentry cache if it knows the parent of a directory

It's possible that the dentry cache can tell us the parent of a
directory.  Therefore, when repairing directory dot dot entries, query
the dcache as a last resort before scanning the entire filesystem.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/fs/xfs/scrub/parent_repair.c b/fs/xfs/scrub/parent_repair.c
index 308a6cad9227..1e4b454b66b9 100644
--- a/fs/xfs/scrub/parent_repair.c
+++ b/fs/xfs/scrub/parent_repair.c
@@ -211,6 +211,44 @@ xrep_parents_walk(
  * capable of rebuilding a directory with the proper parent inode.
  */
 
+/* Check the dentry cache to see if it thinks it knows of a parent. */
+STATIC xfs_ino_t
+xrep_parent_check_dcache(
+	struct xfs_inode	*dp)
+{
+	struct inode		*pip = NULL;
+	struct dentry		*dentry, *parent;
+	xfs_ino_t		ret = NULLFSINO;
+
+	ASSERT(S_ISDIR(VFS_I(dp)->i_mode));
+
+	dentry = d_find_alias(VFS_I(dp));
+	if (!dentry)
+		goto out;
+
+	parent = dget_parent(dentry);
+	if (!parent)
+		goto out_dput;
+
+	if (parent->d_sb != dp->i_mount->m_super) {
+		dput(parent);
+		goto out_dput;
+	}
+
+	pip = igrab(d_inode(parent));
+	dput(parent);
+
+	if (S_ISDIR(pip->i_mode))
+		ret = XFS_I(pip)->i_ino;
+
+	xfs_irele(XFS_I(pip));
+
+out_dput:
+	dput(dentry);
+out:
+	return ret;
+}
+
 struct xrep_dir_parent_pick_info {
 	struct xfs_scrub	*sc;
 	xfs_ino_t		found_parent;
@@ -286,6 +324,7 @@ xrep_dir_parent_find(
 		.sc		= sc,
 		.found_parent	= NULLFSINO,
 	};
+	xfs_ino_t		suggestion;
 	bool			is_parent = false;
 	int			error;
 
@@ -320,6 +359,18 @@ xrep_dir_parent_find(
 			return error;
 	}
 
+	/* Maybe the dcache will supply us with a parent? */
+	suggestion = xrep_parent_check_dcache(sc->ip);
+	if (!xfs_verify_dir_ino(sc->mp, suggestion)) {
+		error = xrep_dir_parent_check(sc, suggestion, &is_parent);
+		if (error)
+			return error;
+		if (is_parent) {
+			*parent_ino = suggestion;
+			return 0;
+		}
+	}
+
 	/* Otherwise, scan the entire filesystem to find a parent. */
 	error = xrep_parents_walk(sc, sc->ip->i_ino, xrep_dir_parent_pick,
 			&dpi);