xfs: online repair of parent pointers

Teach the online repair code to fix parent pointers for directories.
For now, this means correcting the dotdot entry of an existing directory
that is otherwise consistent.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/Makefile

@@ -205,6 +205,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   inode_repair.o \
 				   newbt.o \
 				   nlinks_repair.o \
+				   parent_repair.o \
 				   rcbag_btree.o \
 				   rcbag.o \
 				   reap.o \

fs/xfs/scrub/parent.c

@@ -10,6 +10,7 @@
 #include "xfs_trans_resv.h"
 #include "xfs_mount.h"
 #include "xfs_log_format.h"
+#include "xfs_trans.h"
 #include "xfs_inode.h"
 #include "xfs_icache.h"
 #include "xfs_dir2.h"
@@ -18,12 +19,21 @@
 #include "scrub/common.h"
 #include "scrub/readdir.h"
 #include "scrub/tempfile.h"
+#include "scrub/repair.h"
 
 /* Set us up to scrub parents. */
 int
 xchk_setup_parent(
 	struct xfs_scrub	*sc)
 {
+	int			error;
+
+	if (xchk_could_repair(sc)) {
+		error = xrep_setup_parent(sc);
+		if (error)
+			return error;
+	}
+
 	return xchk_setup_inode_contents(sc, 0);
 }
 

fs/xfs/scrub/parent_repair.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_icache.h"
+#include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_dir2.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_dir2_priv.h"
+#include "xfs_trans_space.h"
+#include "xfs_health.h"
+#include "xfs_exchmaps.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+#include "scrub/iscan.h"
+#include "scrub/findparent.h"
+#include "scrub/readdir.h"
+
+/*
+ * Repairing The Directory Parent Pointer
+ * ======================================
+ *
+ * Currently, only directories support parent pointers (in the form of '..'
+ * entries), so we simply scan the filesystem and update the '..' entry.
+ *
+ * Note that because the only parent pointer is the dotdot entry, we won't
+ * touch an unhealthy directory, since the directory repair code is perfectly
+ * capable of rebuilding a directory with the proper parent inode.
+ *
+ * See the section on locking issues in dir_repair.c for more information about
+ * conflicts with the VFS.  The findparent code wll keep our incore parent
+ * inode up to date.
+ */
+
+struct xrep_parent {
+	struct xfs_scrub	*sc;
+
+	/*
+	 * Information used to scan the filesystem to find the inumber of the
+	 * dotdot entry for this directory.
+	 */
+	struct xrep_parent_scan_info pscan;
+};
+
+/* Tear down all the incore stuff we created. */
+static void
+xrep_parent_teardown(
+	struct xrep_parent	*rp)
+{
+	xrep_findparent_scan_teardown(&rp->pscan);
+}
+
+/* Set up for a parent repair. */
+int
+xrep_setup_parent(
+	struct xfs_scrub	*sc)
+{
+	struct xrep_parent	*rp;
+
+	xchk_fsgates_enable(sc, XCHK_FSGATES_DIRENTS);
+
+	rp = kvzalloc(sizeof(struct xrep_parent), XCHK_GFP_FLAGS);
+	if (!rp)
+		return -ENOMEM;
+	rp->sc = sc;
+	sc->buf = rp;
+
+	return 0;
+}
+
+/*
+ * Scan all files in the filesystem for a child dirent that we can turn into
+ * the dotdot entry for this directory.
+ */
+STATIC int
+xrep_parent_find_dotdot(
+	struct xrep_parent	*rp)
+{
+	struct xfs_scrub	*sc = rp->sc;
+	xfs_ino_t		ino;
+	unsigned int		sick, checked;
+	int			error;
+
+	/*
+	 * Avoid sick directories.  There shouldn't be anyone else clearing the
+	 * directory's sick status.
+	 */
+	xfs_inode_measure_sickness(sc->ip, &sick, &checked);
+	if (sick & XFS_SICK_INO_DIR)
+		return -EFSCORRUPTED;
+
+	ino = xrep_findparent_self_reference(sc);
+	if (ino != NULLFSINO) {
+		xrep_findparent_scan_finish_early(&rp->pscan, ino);
+		return 0;
+	}
+
+	/*
+	 * Drop the ILOCK on this directory so that we can scan for the dotdot
+	 * entry.  Figure out who is going to be the parent of this directory,
+	 * then retake the ILOCK so that we can salvage directory entries.
+	 */
+	xchk_iunlock(sc, XFS_ILOCK_EXCL);
+	error = xrep_findparent_scan(&rp->pscan);
+	xchk_ilock(sc, XFS_ILOCK_EXCL);
+
+	return error;
+}
+
+/* Reset a directory's dotdot entry, if needed. */
+STATIC int
+xrep_parent_reset_dotdot(
+	struct xrep_parent	*rp)
+{
+	struct xfs_scrub	*sc = rp->sc;
+	xfs_ino_t		ino;
+	unsigned int		spaceres;
+	int			error = 0;
+
+	ASSERT(sc->ilock_flags & XFS_ILOCK_EXCL);
+
+	error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &ino);
+	if (error || ino == rp->pscan.parent_ino)
+		return error;
+
+	xfs_trans_ijoin(sc->tp, sc->ip, 0);
+
+	trace_xrep_parent_reset_dotdot(sc->ip, rp->pscan.parent_ino);
+
+	/*
+	 * Reserve more space just in case we have to expand the dir.  We're
+	 * allowed to exceed quota to repair inconsistent metadata.
+	 */
+	spaceres = XFS_RENAME_SPACE_RES(sc->mp, xfs_name_dotdot.len);
+	error = xfs_trans_reserve_more_inode(sc->tp, sc->ip, spaceres, 0,
+			true);
+	if (error)
+		return error;
+
+	error = xfs_dir_replace(sc->tp, sc->ip, &xfs_name_dotdot,
+			rp->pscan.parent_ino, spaceres);
+	if (error)
+		return error;
+
+	/*
+	 * Roll transaction to detach the inode from the transaction but retain
+	 * ILOCK_EXCL.
+	 */
+	return xfs_trans_roll(&sc->tp);
+}
+
+/*
+ * Commit the new parent pointer structure (currently only the dotdot entry) to
+ * the file that we're repairing.
+ */
+STATIC int
+xrep_parent_rebuild_tree(
+	struct xrep_parent	*rp)
+{
+	if (rp->pscan.parent_ino == NULLFSINO) {
+		/* Cannot fix orphaned directories yet. */
+		return -EFSCORRUPTED;
+	}
+
+	return xrep_parent_reset_dotdot(rp);
+}
+
+/* Set up the filesystem scan so we can look for parents. */
+STATIC int
+xrep_parent_setup_scan(
+	struct xrep_parent	*rp)
+{
+	struct xfs_scrub	*sc = rp->sc;
+
+	return xrep_findparent_scan_start(sc, &rp->pscan);
+}
+
+int
+xrep_parent(
+	struct xfs_scrub	*sc)
+{
+	struct xrep_parent	*rp = sc->buf;
+	int			error;
+
+	error = xrep_parent_setup_scan(rp);
+	if (error)
+		return error;
+
+	error = xrep_parent_find_dotdot(rp);
+	if (error)
+		goto out_teardown;
+
+	/* Last chance to abort before we start committing fixes. */
+	if (xchk_should_terminate(sc, &error))
+		goto out_teardown;
+
+	error = xrep_parent_rebuild_tree(rp);
+	if (error)
+		goto out_teardown;
+
+out_teardown:
+	xrep_parent_teardown(rp);
+	return error;
+}

fs/xfs/scrub/repair.h

@@ -92,6 +92,7 @@ int xrep_setup_ag_rmapbt(struct xfs_scrub *sc);
 int xrep_setup_ag_refcountbt(struct xfs_scrub *sc);
 int xrep_setup_xattr(struct xfs_scrub *sc);
 int xrep_setup_directory(struct xfs_scrub *sc);
+int xrep_setup_parent(struct xfs_scrub *sc);
 
 /* Repair setup functions */
 int xrep_setup_ag_allocbt(struct xfs_scrub *sc);
@@ -127,6 +128,7 @@ int xrep_nlinks(struct xfs_scrub *sc);
 int xrep_fscounters(struct xfs_scrub *sc);
 int xrep_xattr(struct xfs_scrub *sc);
 int xrep_directory(struct xfs_scrub *sc);
+int xrep_parent(struct xfs_scrub *sc);
 
 #ifdef CONFIG_XFS_RT
 int xrep_rtbitmap(struct xfs_scrub *sc);
@@ -198,6 +200,7 @@ xrep_setup_nothing(
 #define xrep_setup_ag_refcountbt	xrep_setup_nothing
 #define xrep_setup_xattr		xrep_setup_nothing
 #define xrep_setup_directory		xrep_setup_nothing
+#define xrep_setup_parent		xrep_setup_nothing
 
 #define xrep_setup_inode(sc, imap)	((void)0)
 
@@ -225,6 +228,7 @@ xrep_setup_nothing(
 #define xrep_rtsummary			xrep_notsupported
 #define xrep_xattr			xrep_notsupported
 #define xrep_directory			xrep_notsupported
+#define xrep_parent			xrep_notsupported
 
 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 

fs/xfs/scrub/scrub.c

@@ -343,7 +343,7 @@ static const struct xchk_meta_ops meta_scrub_ops[] = {
 		.type	= ST_INODE,
 		.setup	= xchk_setup_parent,
 		.scrub	= xchk_parent,
-		.repair	= xrep_notsupported,
+		.repair	= xrep_parent,
 	},
 	[XFS_SCRUB_TYPE_RTBITMAP] = {	/* realtime bitmap */
 		.type	= ST_FS,

fs/xfs/scrub/trace.h

@@ -2550,6 +2550,7 @@ DEFINE_EVENT(xrep_dir_class, name, \
 	TP_ARGS(dp, parent_ino))
 DEFINE_XREP_DIR_EVENT(xrep_dir_rebuild_tree);
 DEFINE_XREP_DIR_EVENT(xrep_dir_reset_fork);
+DEFINE_XREP_DIR_EVENT(xrep_parent_reset_dotdot);
 
 DECLARE_EVENT_CLASS(xrep_dirent_class,
 	TP_PROTO(struct xfs_inode *dp, const struct xfs_name *name,