xfs: add raw parent pointer apis to support repair

Add a couple of utility functions to set or remove parent pointers from
a file.  These functions will be used by repair code, hence they skip
the xattr logging that regular parent pointer updates use.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_dir2.c

@@ -434,7 +434,7 @@ int
 xfs_dir_removename(
 	struct xfs_trans	*tp,
 	struct xfs_inode	*dp,
-	struct xfs_name		*name,
+	const struct xfs_name	*name,
 	xfs_ino_t		ino,
 	xfs_extlen_t		total)		/* bmap's total block count */
 {

fs/xfs/libxfs/xfs_dir2.h

@@ -58,7 +58,7 @@ extern int xfs_dir_lookup(struct xfs_trans *tp, struct xfs_inode *dp,
 				const struct xfs_name *name, xfs_ino_t *inum,
 				struct xfs_name *ci_name);
 extern int xfs_dir_removename(struct xfs_trans *tp, struct xfs_inode *dp,
-				struct xfs_name *name, xfs_ino_t ino,
+				const struct xfs_name *name, xfs_ino_t ino,
 				xfs_extlen_t tot);
 extern int xfs_dir_replace(struct xfs_trans *tp, struct xfs_inode *dp,
 				const struct xfs_name *name, xfs_ino_t inum,

fs/xfs/libxfs/xfs_parent.c

@@ -313,3 +313,67 @@ xfs_parent_lookup(
 	xfs_parent_da_args_init(scratch, tp, pptr, ip, ip->i_ino, parent_name);
 	return xfs_attr_get_ilocked(scratch);
 }
+
+/* Sanity-check a parent pointer before we try to perform repairs. */
+static inline bool
+xfs_parent_sanity_check(
+	struct xfs_mount		*mp,
+	const struct xfs_name		*parent_name,
+	const struct xfs_parent_rec	*pptr)
+{
+	if (!xfs_parent_namecheck(XFS_ATTR_PARENT, parent_name->name,
+				parent_name->len))
+		return false;
+
+	if (!xfs_parent_valuecheck(mp, pptr, sizeof(*pptr)))
+		return false;
+
+	return true;
+}
+
+
+/*
+ * Attach the parent pointer (@parent_name -> @pptr) to @ip immediately.
+ * Caller must not have a transaction or hold the ILOCK.  This is for
+ * specialized repair functions only.  The scratchpad need not be initialized.
+ */
+int
+xfs_parent_set(
+	struct xfs_inode	*ip,
+	xfs_ino_t		owner,
+	const struct xfs_name	*parent_name,
+	struct xfs_parent_rec	*pptr,
+	struct xfs_da_args	*scratch)
+{
+	if (!xfs_parent_sanity_check(ip->i_mount, parent_name, pptr)) {
+		ASSERT(0);
+		return -EFSCORRUPTED;
+	}
+
+	memset(scratch, 0, sizeof(struct xfs_da_args));
+	xfs_parent_da_args_init(scratch, NULL, pptr, ip, owner, parent_name);
+	return xfs_attr_set(scratch, XFS_ATTRUPDATE_CREATE, false);
+}
+
+/*
+ * Remove the parent pointer (@parent_name -> @pptr) from @ip immediately.
+ * Caller must not have a transaction or hold the ILOCK.  This is for
+ * specialized repair functions only.  The scratchpad need not be initialized.
+ */
+int
+xfs_parent_unset(
+	struct xfs_inode		*ip,
+	xfs_ino_t			owner,
+	const struct xfs_name		*parent_name,
+	struct xfs_parent_rec		*pptr,
+	struct xfs_da_args		*scratch)
+{
+	if (!xfs_parent_sanity_check(ip->i_mount, parent_name, pptr)) {
+		ASSERT(0);
+		return -EFSCORRUPTED;
+	}
+
+	memset(scratch, 0, sizeof(struct xfs_da_args));
+	xfs_parent_da_args_init(scratch, NULL, pptr, ip, owner, parent_name);
+	return xfs_attr_set(scratch, XFS_ATTRUPDATE_REMOVE, false);
+}

fs/xfs/libxfs/xfs_parent.h

@@ -100,5 +100,11 @@ int xfs_parent_from_attr(struct xfs_mount *mp, unsigned int attr_flags,
 int xfs_parent_lookup(struct xfs_trans *tp, struct xfs_inode *ip,
 		const struct xfs_name *name, struct xfs_parent_rec *pptr,
 		struct xfs_da_args *scratch);
+int xfs_parent_set(struct xfs_inode *ip, xfs_ino_t owner,
+		const struct xfs_name *name, struct xfs_parent_rec *pptr,
+		struct xfs_da_args *scratch);
+int xfs_parent_unset(struct xfs_inode *ip, xfs_ino_t owner,
+		const struct xfs_name *name, struct xfs_parent_rec *pptr,
+		struct xfs_da_args *scratch);
 
 #endif /* __XFS_PARENT_H__ */