xfs: check metadata directory file path connectivity

Create a new scrubber type that checks that well known metadata
directory paths are connected to the metadata inode that the incore
structures think is in use.  For example, check that "/quota/user" in
the metadata directory tree actually points to
mp->m_quotainfo->qi_uquotaip->i_ino.

Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>

Author: Darrick J. Wong

fs/xfs/Makefile

@@ -174,6 +174,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   inode.o \
 				   iscan.o \
 				   listxattr.o \
+				   metapath.o \
 				   nlinks.o \
 				   parent.o \
 				   readdir.o \

fs/xfs/libxfs/xfs_fs.h

@@ -199,6 +199,7 @@ struct xfs_fsop_geom {
 #define XFS_FSOP_GEOM_SICK_QUOTACHECK	(1 << 6)  /* quota counts */
 #define XFS_FSOP_GEOM_SICK_NLINKS	(1 << 7)  /* inode link counts */
 #define XFS_FSOP_GEOM_SICK_METADIR	(1 << 8)  /* metadata directory */
+#define XFS_FSOP_GEOM_SICK_METAPATH	(1 << 9)  /* metadir tree path */
 
 /* Output for XFS_FS_COUNTS */
 typedef struct xfs_fsop_counts {
@@ -732,9 +733,10 @@ struct xfs_scrub_metadata {
 #define XFS_SCRUB_TYPE_NLINKS	26	/* inode link counts */
 #define XFS_SCRUB_TYPE_HEALTHY	27	/* everything checked out ok */
 #define XFS_SCRUB_TYPE_DIRTREE	28	/* directory tree structure */
+#define XFS_SCRUB_TYPE_METAPATH	29	/* metadata directory tree paths */
 
 /* Number of scrub subcommands. */
-#define XFS_SCRUB_TYPE_NR	29
+#define XFS_SCRUB_TYPE_NR	30
 
 /*
  * This special type code only applies to the vectored scrub implementation.
@@ -812,6 +814,15 @@ struct xfs_scrub_vec_head {
 
 #define XFS_SCRUB_VEC_FLAGS_ALL		(0)
 
+/*
+ * i: sm_ino values for XFS_SCRUB_TYPE_METAPATH to select a metadata file for
+ * path checking.
+ */
+#define XFS_SCRUB_METAPATH_PROBE	(0)  /* do we have a metapath scrubber? */
+
+/* Number of metapath sm_ino values */
+#define XFS_SCRUB_METAPATH_NR		(1)
+
 /*
  * ioctl limits
  */

fs/xfs/libxfs/xfs_health.h

@@ -63,6 +63,7 @@ struct xfs_da_args;
 #define XFS_SICK_FS_QUOTACHECK	(1 << 4)  /* quota counts */
 #define XFS_SICK_FS_NLINKS	(1 << 5)  /* inode link counts */
 #define XFS_SICK_FS_METADIR	(1 << 6)  /* metadata directory tree */
+#define XFS_SICK_FS_METAPATH	(1 << 7)  /* metadata directory tree path */
 
 /* Observable health issues for realtime volume metadata. */
 #define XFS_SICK_RT_BITMAP	(1 << 0)  /* realtime bitmap */
@@ -107,7 +108,8 @@ struct xfs_da_args;
 				 XFS_SICK_FS_PQUOTA | \
 				 XFS_SICK_FS_QUOTACHECK | \
 				 XFS_SICK_FS_NLINKS | \
-				 XFS_SICK_FS_METADIR)
+				 XFS_SICK_FS_METADIR | \
+				 XFS_SICK_FS_METAPATH)
 
 #define XFS_SICK_RT_PRIMARY	(XFS_SICK_RT_BITMAP | \
 				 XFS_SICK_RT_SUMMARY)

fs/xfs/scrub/common.h

@@ -73,6 +73,7 @@ int xchk_setup_xattr(struct xfs_scrub *sc);
 int xchk_setup_symlink(struct xfs_scrub *sc);
 int xchk_setup_parent(struct xfs_scrub *sc);
 int xchk_setup_dirtree(struct xfs_scrub *sc);
+int xchk_setup_metapath(struct xfs_scrub *sc);
 #ifdef CONFIG_XFS_RT
 int xchk_setup_rtbitmap(struct xfs_scrub *sc);
 int xchk_setup_rtsummary(struct xfs_scrub *sc);

fs/xfs/scrub/health.c

@@ -109,6 +109,7 @@ static const struct xchk_health_map type_to_health_flag[XFS_SCRUB_TYPE_NR] = {
 	[XFS_SCRUB_TYPE_QUOTACHECK]	= { XHG_FS,  XFS_SICK_FS_QUOTACHECK },
 	[XFS_SCRUB_TYPE_NLINKS]		= { XHG_FS,  XFS_SICK_FS_NLINKS },
 	[XFS_SCRUB_TYPE_DIRTREE]	= { XHG_INO, XFS_SICK_INO_DIRTREE },
+	[XFS_SCRUB_TYPE_METAPATH]	= { XHG_FS,  XFS_SICK_FS_METAPATH },
 };
 
 /* Return the health status mask for this scrub type. */

fs/xfs/scrub/metapath.c

@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <[email protected]>
+ */
+#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_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_inode.h"
+#include "xfs_metafile.h"
+#include "xfs_quota.h"
+#include "xfs_qm.h"
+#include "xfs_dir2.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/readdir.h"
+
+/*
+ * Metadata Directory Tree Paths
+ * =============================
+ *
+ * A filesystem with metadir enabled expects to find metadata structures
+ * attached to files that are accessible by walking a path down the metadata
+ * directory tree.  Given the metadir path and the incore inode storing the
+ * metadata, this scrubber ensures that the ondisk metadir path points to the
+ * ondisk inode represented by the incore inode.
+ */
+
+struct xchk_metapath {
+	struct xfs_scrub		*sc;
+
+	/* Name for lookup */
+	struct xfs_name			xname;
+
+	/* Path for this metadata file and the parent directory */
+	const char			*path;
+	const char			*parent_path;
+
+	/* Directory parent of the metadata file. */
+	struct xfs_inode		*dp;
+
+	/* Locks held on dp */
+	unsigned int			dp_ilock_flags;
+};
+
+/* Release resources tracked in the buffer. */
+static inline void
+xchk_metapath_cleanup(
+	void			*buf)
+{
+	struct xchk_metapath	*mpath = buf;
+
+	if (mpath->dp_ilock_flags)
+		xfs_iunlock(mpath->dp, mpath->dp_ilock_flags);
+	kfree(mpath->path);
+}
+
+int
+xchk_setup_metapath(
+	struct xfs_scrub	*sc)
+{
+	if (!xfs_has_metadir(sc->mp))
+		return -ENOENT;
+	if (sc->sm->sm_gen)
+		return -EINVAL;
+
+	switch (sc->sm->sm_ino) {
+	case XFS_SCRUB_METAPATH_PROBE:
+		/* Just probing, nothing else to do. */
+		if (sc->sm->sm_agno)
+			return -EINVAL;
+		return 0;
+	default:
+		return -ENOENT;
+	}
+}
+
+/*
+ * Take the ILOCK on the metadata directory parent and child.  We do not know
+ * that the metadata directory is not corrupt, so we lock the parent and try
+ * to lock the child.  Returns 0 if successful, or -EINTR to abort the scrub.
+ */
+STATIC int
+xchk_metapath_ilock_both(
+	struct xchk_metapath	*mpath)
+{
+	struct xfs_scrub	*sc = mpath->sc;
+	int			error = 0;
+
+	while (true) {
+		xfs_ilock(mpath->dp, XFS_ILOCK_EXCL);
+		if (xchk_ilock_nowait(sc, XFS_ILOCK_EXCL)) {
+			mpath->dp_ilock_flags |= XFS_ILOCK_EXCL;
+			return 0;
+		}
+		xfs_iunlock(mpath->dp, XFS_ILOCK_EXCL);
+
+		if (xchk_should_terminate(sc, &error))
+			return error;
+
+		delay(1);
+	}
+
+	ASSERT(0);
+	return -EINTR;
+}
+
+/* Unlock parent and child inodes. */
+static inline void
+xchk_metapath_iunlock(
+	struct xchk_metapath	*mpath)
+{
+	struct xfs_scrub	*sc = mpath->sc;
+
+	xchk_iunlock(sc, XFS_ILOCK_EXCL);
+
+	mpath->dp_ilock_flags &= ~XFS_ILOCK_EXCL;
+	xfs_iunlock(mpath->dp, XFS_ILOCK_EXCL);
+}
+
+int
+xchk_metapath(
+	struct xfs_scrub	*sc)
+{
+	struct xchk_metapath	*mpath = sc->buf;
+	xfs_ino_t		ino = NULLFSINO;
+	int			error;
+
+	/* Just probing, nothing else to do. */
+	if (sc->sm->sm_ino == XFS_SCRUB_METAPATH_PROBE)
+		return 0;
+
+	/* Parent required to do anything else. */
+	if (mpath->dp == NULL) {
+		xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+		return 0;
+	}
+
+	error = xchk_trans_alloc_empty(sc);
+	if (error)
+		return error;
+
+	error = xchk_metapath_ilock_both(mpath);
+	if (error)
+		goto out_cancel;
+
+	/* Make sure the parent dir has a dirent pointing to this file. */
+	error = xchk_dir_lookup(sc, mpath->dp, &mpath->xname, &ino);
+	trace_xchk_metapath_lookup(sc, mpath->path, mpath->dp, ino);
+	if (error == -ENOENT) {
+		/* No directory entry at all */
+		xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+		error = 0;
+		goto out_ilock;
+	}
+	if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
+		goto out_ilock;
+	if (ino != sc->ip->i_ino) {
+		/* Pointing to wrong inode */
+		xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+	}
+
+out_ilock:
+	xchk_metapath_iunlock(mpath);
+out_cancel:
+	xchk_trans_cancel(sc);
+	return error;
+}

fs/xfs/scrub/scrub.c

@@ -442,6 +442,13 @@ static const struct xchk_meta_ops meta_scrub_ops[] = {
 		.has	= xfs_has_parent,
 		.repair	= xrep_dirtree,
 	},
+	[XFS_SCRUB_TYPE_METAPATH] = {	/* metadata directory tree path */
+		.type	= ST_GENERIC,
+		.setup	= xchk_setup_metapath,
+		.scrub	= xchk_metapath,
+		.has	= xfs_has_metadir,
+		.repair	= xrep_notsupported,
+	},
 };
 
 static int
@@ -489,6 +496,8 @@ xchk_validate_inputs(
 		if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
 			goto out;
 		break;
+	case ST_GENERIC:
+		break;
 	default:
 		goto out;
 	}

fs/xfs/scrub/scrub.h

@@ -73,6 +73,7 @@ enum xchk_type {
 	ST_PERAG,	/* per-AG metadata */
 	ST_FS,		/* per-FS metadata */
 	ST_INODE,	/* per-inode metadata */
+	ST_GENERIC,	/* determined by the scrubber */
 };
 
 struct xchk_meta_ops {
@@ -255,6 +256,7 @@ int xchk_xattr(struct xfs_scrub *sc);
 int xchk_symlink(struct xfs_scrub *sc);
 int xchk_parent(struct xfs_scrub *sc);
 int xchk_dirtree(struct xfs_scrub *sc);
+int xchk_metapath(struct xfs_scrub *sc);
 #ifdef CONFIG_XFS_RT
 int xchk_rtbitmap(struct xfs_scrub *sc);
 int xchk_rtsummary(struct xfs_scrub *sc);

fs/xfs/scrub/stats.c

@@ -80,6 +80,7 @@ static const char *name_map[XFS_SCRUB_TYPE_NR] = {
 	[XFS_SCRUB_TYPE_QUOTACHECK]	= "quotacheck",
 	[XFS_SCRUB_TYPE_NLINKS]		= "nlinks",
 	[XFS_SCRUB_TYPE_DIRTREE]	= "dirtree",
+	[XFS_SCRUB_TYPE_METAPATH]	= "metapath",
 };
 
 /* Format the scrub stats into a text buffer, similar to pcp style. */

fs/xfs/scrub/trace.c

@@ -20,6 +20,7 @@
 #include "xfs_dir2.h"
 #include "xfs_rmap.h"
 #include "xfs_parent.h"
+#include "xfs_metafile.h"
 #include "scrub/scrub.h"
 #include "scrub/xfile.h"
 #include "scrub/xfarray.h"