Merge tag 'scrub-usage-stats-6.6_2023-08-10' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.6-mergeA

xfs: add usage counters for scrub

This series introduces simple usage and performance counters for the
online fsck subsystem.  The goal here is to enable developers and
sysadmins to look at summary counts of how many objects were checked and
repaired; what the outcomes were; and how much time the kernel has spent
on these operations.  The counter file is exposed in debugfs because
that's easier than cramming it into the device model, and debugfs
doesn't have rules against complex file contents, unlike sysfs.

Signed-off-by: Darrick J. Wong <[email protected]>
Signed-off-by: Chandan Babu R <[email protected]>

* tag 'scrub-usage-stats-6.6_2023-08-10' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: track usage statistics of online fsck
  xfs: create scaffolding for creating debugfs entries

12 files changed, 569 insertions, 11 deletions

diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
index 152348b4dece..c9d653168ad0 100644
--- a/fs/xfs/Kconfig
+++ b/fs/xfs/Kconfig
@@ -143,6 +143,23 @@ config XFS_ONLINE_SCRUB
 
 	  If unsure, say N.
 
+config XFS_ONLINE_SCRUB_STATS
+	bool "XFS online metadata check usage data collection"
+	default y
+	depends on XFS_ONLINE_SCRUB
+	select FS_DEBUG
+	help
+	  If you say Y here, the kernel will gather usage data about
+	  the online metadata check subsystem.  This includes the number
+	  of invocations, the outcomes, and the results of repairs, if any.
+	  This may slow down scrub slightly due to the use of high precision
+	  timers and the need to merge per-invocation information into the
+	  filesystem counters.
+
+	  Usage data are collected in /sys/kernel/debug/xfs/scrub.
+
+	  If unsure, say N.
+
 config XFS_ONLINE_REPAIR
 	bool "XFS online metadata repair support"
 	default n
diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index f175f823fcd4..d59fcf3fd0d5 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -168,6 +168,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   xfile.o \
 				   )
 
+xfs-$(CONFIG_XFS_ONLINE_SCRUB_STATS) += scrub/stats.o
 xfs-$(CONFIG_XFS_RT)		+= scrub/rtbitmap.o
 xfs-$(CONFIG_XFS_QUOTA)		+= scrub/quota.o
 
diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 83a1b1437a4f..1b8b5439f2d7 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -32,6 +32,7 @@
 #include "scrub/trace.h"
 #include "scrub/repair.h"
 #include "scrub/bitmap.h"
+#include "scrub/stats.h"
 
 /*
  * Attempt to repair some metadata, if the metadata is corrupt and userspace
@@ -40,8 +41,10 @@
  */
 int
 xrep_attempt(
-	struct xfs_scrub	*sc)
+	struct xfs_scrub	*sc,
+	struct xchk_stats_run	*run)
 {
+	u64			repair_start;
 	int			error = 0;
 
 	trace_xrep_attempt(XFS_I(file_inode(sc->file)), sc->sm, error);
@@ -50,8 +53,11 @@ xrep_attempt(
 
 	/* Repair whatever's broken. */
 	ASSERT(sc->ops->repair);
+	run->repair_attempted = true;
+	repair_start = xchk_stats_now();
 	error = sc->ops->repair(sc);
 	trace_xrep_done(XFS_I(file_inode(sc->file)), sc->sm, error);
+	run->repair_ns += xchk_stats_elapsed_ns(repair_start);
 	switch (error) {
 	case 0:
 		/*
@@ -60,14 +66,17 @@ xrep_attempt(
 		 */
 		sc->sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
 		sc->flags |= XREP_ALREADY_FIXED;
+		run->repair_succeeded = true;
 		return -EAGAIN;
 	case -ECHRNG:
 		sc->flags |= XCHK_NEED_DRAIN;
+		run->retries++;
 		return -EAGAIN;
 	case -EDEADLOCK:
 		/* Tell the caller to try again having grabbed all the locks. */
 		if (!(sc->flags & XCHK_TRY_HARDER)) {
 			sc->flags |= XCHK_TRY_HARDER;
+			run->retries++;
 			return -EAGAIN;
 		}
 		/*
diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h
index 45478040a19d..60d2a9ae5f2e 100644
--- a/fs/xfs/scrub/repair.h
+++ b/fs/xfs/scrub/repair.h
@@ -8,6 +8,8 @@
 
 #include "xfs_quota_defs.h"
 
+struct xchk_stats_run;
+
 static inline int xrep_notsupported(struct xfs_scrub *sc)
 {
 	return -EOPNOTSUPP;
@@ -25,7 +27,7 @@ static inline int xrep_notsupported(struct xfs_scrub *sc)
 
 /* Repair helpers */
 
-int xrep_attempt(struct xfs_scrub *sc);
+int xrep_attempt(struct xfs_scrub *sc, struct xchk_stats_run *run);
 void xrep_failure(struct xfs_mount *mp);
 int xrep_roll_ag_trans(struct xfs_scrub *sc);
 int xrep_defer_finish(struct xfs_scrub *sc);
@@ -70,7 +72,8 @@ int xrep_agi(struct xfs_scrub *sc);
 
 static inline int
 xrep_attempt(
-	struct xfs_scrub	*sc)
+	struct xfs_scrub	*sc,
+	struct xchk_stats_run	*run)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index 3d98f604765e..e6962cf651d9 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -22,6 +22,7 @@
 #include "scrub/trace.h"
 #include "scrub/repair.h"
 #include "scrub/health.h"
+#include "scrub/stats.h"
 
 /*
  * Online Scrub and Repair
@@ -461,8 +462,10 @@ xfs_scrub_metadata(
 	struct file			*file,
 	struct xfs_scrub_metadata	*sm)
 {
+	struct xchk_stats_run		run = { };
 	struct xfs_scrub		*sc;
 	struct xfs_mount		*mp = XFS_I(file_inode(file))->i_mount;
+	u64				check_start;
 	int				error = 0;
 
 	BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
@@ -517,7 +520,9 @@ retry_op:
 		goto out_teardown;
 
 	/* Scrub for errors. */
+	check_start = xchk_stats_now();
 	error = sc->ops->scrub(sc);
+	run.scrub_ns += xchk_stats_elapsed_ns(check_start);
 	if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
 		goto try_harder;
 	if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
@@ -551,7 +556,7 @@ retry_op:
 		 * If it's broken, userspace wants us to fix it, and we haven't
 		 * already tried to fix it, then attempt a repair.
 		 */
-		error = xrep_attempt(sc);
+		error = xrep_attempt(sc, &run);
 		if (error == -EAGAIN) {
 			/*
 			 * Either the repair function succeeded or it couldn't
@@ -579,12 +584,15 @@ out:
 		sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
 		error = 0;
 	}
+	if (error != -ENOENT)
+		xchk_stats_merge(mp, sm, &run);
 	return error;
 need_drain:
 	error = xchk_teardown(sc, 0);
 	if (error)
 		goto out_sc;
 	sc->flags |= XCHK_NEED_DRAIN;
+	run.retries++;
 	goto retry_op;
 try_harder:
 	/*
@@ -596,5 +604,6 @@ try_harder:
 	if (error)
 		goto out_sc;
 	sc->flags |= XCHK_TRY_HARDER;
+	run.retries++;
 	goto retry_op;
 }
diff --git a/fs/xfs/scrub/stats.c b/fs/xfs/scrub/stats.c
new file mode 100644
index 000000000000..aeb92624176b
--- /dev/null
+++ b/fs/xfs/scrub/stats.c
@@ -0,0 +1,405 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 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_sysfs.h"
+#include "xfs_btree.h"
+#include "xfs_super.h"
+#include "scrub/scrub.h"
+#include "scrub/stats.h"
+#include "scrub/trace.h"
+
+struct xchk_scrub_stats {
+	/* all 32-bit counters here */
+
+	/* checking stats */
+	uint32_t		invocations;
+	uint32_t		clean;
+	uint32_t		corrupt;
+	uint32_t		preen;
+	uint32_t		xfail;
+	uint32_t		xcorrupt;
+	uint32_t		incomplete;
+	uint32_t		warning;
+	uint32_t		retries;
+
+	/* repair stats */
+	uint32_t		repair_invocations;
+	uint32_t		repair_success;
+
+	/* all 64-bit items here */
+
+	/* runtimes */
+	uint64_t		checktime_us;
+	uint64_t		repairtime_us;
+
+	/* non-counter state must go at the end for clearall */
+	spinlock_t		css_lock;
+};
+
+struct xchk_stats {
+	struct dentry		*cs_debugfs;
+	struct xchk_scrub_stats	cs_stats[XFS_SCRUB_TYPE_NR];
+};
+
+
+static struct xchk_stats	global_stats;
+
+static const char *name_map[XFS_SCRUB_TYPE_NR] = {
+	[XFS_SCRUB_TYPE_SB]		= "sb",
+	[XFS_SCRUB_TYPE_AGF]		= "agf",
+	[XFS_SCRUB_TYPE_AGFL]		= "agfl",
+	[XFS_SCRUB_TYPE_AGI]		= "agi",
+	[XFS_SCRUB_TYPE_BNOBT]		= "bnobt",
+	[XFS_SCRUB_TYPE_CNTBT]		= "cntbt",
+	[XFS_SCRUB_TYPE_INOBT]		= "inobt",
+	[XFS_SCRUB_TYPE_FINOBT]		= "finobt",
+	[XFS_SCRUB_TYPE_RMAPBT]		= "rmapbt",
+	[XFS_SCRUB_TYPE_REFCNTBT]	= "refcountbt",
+	[XFS_SCRUB_TYPE_INODE]		= "inode",
+	[XFS_SCRUB_TYPE_BMBTD]		= "bmapbtd",
+	[XFS_SCRUB_TYPE_BMBTA]		= "bmapbta",
+	[XFS_SCRUB_TYPE_BMBTC]		= "bmapbtc",
+	[XFS_SCRUB_TYPE_DIR]		= "directory",
+	[XFS_SCRUB_TYPE_XATTR]		= "xattr",
+	[XFS_SCRUB_TYPE_SYMLINK]	= "symlink",
+	[XFS_SCRUB_TYPE_PARENT]		= "parent",
+	[XFS_SCRUB_TYPE_RTBITMAP]	= "rtbitmap",
+	[XFS_SCRUB_TYPE_RTSUM]		= "rtsummary",
+	[XFS_SCRUB_TYPE_UQUOTA]		= "usrquota",
+	[XFS_SCRUB_TYPE_GQUOTA]		= "grpquota",
+	[XFS_SCRUB_TYPE_PQUOTA]		= "prjquota",
+	[XFS_SCRUB_TYPE_FSCOUNTERS]	= "fscounters",
+};
+
+/* Format the scrub stats into a text buffer, similar to pcp style. */
+STATIC ssize_t
+xchk_stats_format(
+	struct xchk_stats	*cs,
+	char			*buf,
+	size_t			remaining)
+{
+	struct xchk_scrub_stats	*css = &cs->cs_stats[0];
+	unsigned int		i;
+	ssize_t			copied = 0;
+	int			ret = 0;
+
+	for (i = 0; i < XFS_SCRUB_TYPE_NR; i++, css++) {
+		if (!name_map[i])
+			continue;
+
+		ret = scnprintf(buf, remaining,
+ "%s %u %u %u %u %u %u %u %u %u %llu %u %u %llu\n",
+				name_map[i],
+				(unsigned int)css->invocations,
+				(unsigned int)css->clean,
+				(unsigned int)css->corrupt,
+				(unsigned int)css->preen,
+				(unsigned int)css->xfail,
+				(unsigned int)css->xcorrupt,
+				(unsigned int)css->incomplete,
+				(unsigned int)css->warning,
+				(unsigned int)css->retries,
+				(unsigned long long)css->checktime_us,
+				(unsigned int)css->repair_invocations,
+				(unsigned int)css->repair_success,
+				(unsigned long long)css->repairtime_us);
+		if (ret <= 0)
+			break;
+
+		remaining -= ret;
+		copied += ret;
+		buf +=  ret;
+	}
+
+	return copied > 0 ? copied : ret;
+}
+
+/* Estimate the worst case buffer size required to hold the whole report. */
+STATIC size_t
+xchk_stats_estimate_bufsize(
+	struct xchk_stats	*cs)
+{
+	struct xchk_scrub_stats	*css = &cs->cs_stats[0];
+	unsigned int		i;
+	size_t			field_width;
+	size_t			ret = 0;
+
+	/* 4294967296 plus one space for each u32 field */
+	field_width = 11 * (offsetof(struct xchk_scrub_stats, checktime_us) /
+			    sizeof(uint32_t));
+
+	/* 18446744073709551615 plus one space for each u64 field */
+	field_width += 21 * ((offsetof(struct xchk_scrub_stats, css_lock) -
+			      offsetof(struct xchk_scrub_stats, checktime_us)) /
+			     sizeof(uint64_t));
+
+	for (i = 0; i < XFS_SCRUB_TYPE_NR; i++, css++) {
+		if (!name_map[i])
+			continue;
+
+		/* name plus one space */
+		ret += 1 + strlen(name_map[i]);
+
+		/* all fields, plus newline */
+		ret += field_width + 1;
+	}
+
+	return ret;
+}
+
+/* Clear all counters. */
+STATIC void
+xchk_stats_clearall(
+	struct xchk_stats	*cs)
+{
+	struct xchk_scrub_stats	*css = &cs->cs_stats[0];
+	unsigned int		i;
+
+	for (i = 0; i < XFS_SCRUB_TYPE_NR; i++, css++) {
+		spin_lock(&css->css_lock);
+		memset(css, 0, offsetof(struct xchk_scrub_stats, css_lock));
+		spin_unlock(&css->css_lock);
+	}
+}
+
+#define XFS_SCRUB_OFLAG_UNCLEAN	(XFS_SCRUB_OFLAG_CORRUPT | \
+				 XFS_SCRUB_OFLAG_PREEN | \
+				 XFS_SCRUB_OFLAG_XFAIL | \
+				 XFS_SCRUB_OFLAG_XCORRUPT | \
+				 XFS_SCRUB_OFLAG_INCOMPLETE | \
+				 XFS_SCRUB_OFLAG_WARNING)
+
+STATIC void
+xchk_stats_merge_one(
+	struct xchk_stats		*cs,
+	const struct xfs_scrub_metadata	*sm,
+	const struct xchk_stats_run	*run)
+{
+	struct xchk_scrub_stats		*css;
+
+	ASSERT(sm->sm_type < XFS_SCRUB_TYPE_NR);
+
+	css = &cs->cs_stats[sm->sm_type];
+	spin_lock(&css->css_lock);
+	css->invocations++;
+	if (!(sm->sm_flags & XFS_SCRUB_OFLAG_UNCLEAN))
+		css->clean++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+		css->corrupt++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_PREEN)
+		css->preen++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_XFAIL)
+		css->xfail++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_XCORRUPT)
+		css->xcorrupt++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE)
+		css->incomplete++;
+	if (sm->sm_flags & XFS_SCRUB_OFLAG_WARNING)
+		css->warning++;
+	css->retries += run->retries;
+	css->checktime_us += howmany_64(run->scrub_ns, NSEC_PER_USEC);
+
+	if (run->repair_attempted)
+		css->repair_invocations++;
+	if (run->repair_succeeded)
+		css->repair_success++;
+	css->repairtime_us += howmany_64(run->repair_ns, NSEC_PER_USEC);
+	spin_unlock(&css->css_lock);
+}
+
+/* Merge these scrub-run stats into the global and mount stat data. */
+void
+xchk_stats_merge(
+	struct xfs_mount		*mp,
+	const struct xfs_scrub_metadata	*sm,
+	const struct xchk_stats_run	*run)
+{
+	xchk_stats_merge_one(&global_stats, sm, run);
+	xchk_stats_merge_one(mp->m_scrub_stats, sm, run);
+}
+
+/* debugfs boilerplate */
+
+static ssize_t
+xchk_scrub_stats_read(
+	struct file		*file,
+	char __user		*ubuf,
+	size_t			count,
+	loff_t			*ppos)
+{
+	struct xchk_stats	*cs = file->private_data;
+	char			*buf;
+	size_t			bufsize;
+	ssize_t			avail, ret;
+
+	/*
+	 * This generates stringly snapshot of all the scrub counters, so we
+	 * do not want userspace to receive garbled text from multiple calls.
+	 * If the file position is greater than 0, return a short read.
+	 */
+	if (*ppos > 0)
+		return 0;
+
+	bufsize = xchk_stats_estimate_bufsize(cs);
+
+	buf = kvmalloc(bufsize, XCHK_GFP_FLAGS);
+	if (!buf)
+		return -ENOMEM;
+
+	avail = xchk_stats_format(cs, buf, bufsize);
+	if (avail < 0) {
+		ret = avail;
+		goto out;
+	}
+
+	ret = simple_read_from_buffer(ubuf, count, ppos, buf, avail);
+out:
+	kvfree(buf);
+	return ret;
+}
+
+static const struct file_operations scrub_stats_fops = {
+	.open			= simple_open,
+	.read			= xchk_scrub_stats_read,
+};
+
+static ssize_t
+xchk_clear_scrub_stats_write(
+	struct file		*file,
+	const char __user	*ubuf,
+	size_t			count,
+	loff_t			*ppos)
+{
+	struct xchk_stats	*cs = file->private_data;
+	unsigned int		val;
+	int			ret;
+
+	ret = kstrtouint_from_user(ubuf, count, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	xchk_stats_clearall(cs);
+	return count;
+}
+
+static const struct file_operations clear_scrub_stats_fops = {
+	.open			= simple_open,
+	.write			= xchk_clear_scrub_stats_write,
+};
+
+/* Initialize the stats object. */
+STATIC int
+xchk_stats_init(
+	struct xchk_stats	*cs,
+	struct xfs_mount	*mp)
+{
+	struct xchk_scrub_stats	*css = &cs->cs_stats[0];
+	unsigned int		i;
+
+	for (i = 0; i < XFS_SCRUB_TYPE_NR; i++, css++)
+		spin_lock_init(&css->css_lock);
+
+	return 0;
+}
+
+/* Connect the stats object to debugfs. */
+void
+xchk_stats_register(
+	struct xchk_stats	*cs,
+	struct dentry		*parent)
+{
+	if (!parent)
+		return;
+
+	cs->cs_debugfs = xfs_debugfs_mkdir("scrub", parent);
+	if (!cs->cs_debugfs)
+		return;
+
+	debugfs_create_file("stats", 0644, cs->cs_debugfs, cs,
+			&scrub_stats_fops);
+	debugfs_create_file("clear_stats", 0400, cs->cs_debugfs, cs,
+			&clear_scrub_stats_fops);
+}
+
+/* Free all resources related to the stats object. */
+STATIC int
+xchk_stats_teardown(
+	struct xchk_stats	*cs)
+{
+	return 0;
+}
+
+/* Disconnect the stats object from debugfs. */
+void
+xchk_stats_unregister(
+	struct xchk_stats	*cs)
+{
+	debugfs_remove(cs->cs_debugfs);
+}
+
+/* Initialize global stats and register them */
+int __init
+xchk_global_stats_setup(
+	struct dentry		*parent)
+{
+	int			error;
+
+	error = xchk_stats_init(&global_stats, NULL);
+	if (error)
+		return error;
+
+	xchk_stats_register(&global_stats, parent);
+	return 0;
+}
+
+/* Unregister global stats and tear them down */
+void
+xchk_global_stats_teardown(void)
+{
+	xchk_stats_unregister(&global_stats);
+	xchk_stats_teardown(&global_stats);
+}
+
+/* Allocate per-mount stats */
+int
+xchk_mount_stats_alloc(
+	struct xfs_mount	*mp)
+{
+	struct xchk_stats	*cs;
+	int			error;
+
+	cs = kvzalloc(sizeof(struct xchk_stats), GFP_KERNEL);
+	if (!cs)
+		return -ENOMEM;
+
+	error = xchk_stats_init(cs, mp);
+	if (error)
+		goto out_free;
+
+	mp->m_scrub_stats = cs;
+	return 0;
+out_free:
+	kvfree(cs);
+	return error;
+}
+
+/* Free per-mount stats */
+void
+xchk_mount_stats_free(
+	struct xfs_mount	*mp)
+{
+	xchk_stats_teardown(mp->m_scrub_stats);
+	kvfree(mp->m_scrub_stats);
+	mp->m_scrub_stats = NULL;
+}
diff --git a/fs/xfs/scrub/stats.h b/fs/xfs/scrub/stats.h
new file mode 100644
index 000000000000..b358ad8d8b90
--- /dev/null
+++ b/fs/xfs/scrub/stats.h
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <[email protected]>
+ */
+#ifndef __XFS_SCRUB_STATS_H__
+#define __XFS_SCRUB_STATS_H__
+
+struct xchk_stats_run {
+	u64			scrub_ns;
+	u64			repair_ns;
+	unsigned int		retries;
+	bool			repair_attempted;
+	bool			repair_succeeded;
+};
+
+#ifdef CONFIG_XFS_ONLINE_SCRUB_STATS
+struct xchk_stats;
+
+int __init xchk_global_stats_setup(struct dentry *parent);
+void xchk_global_stats_teardown(void);
+
+int xchk_mount_stats_alloc(struct xfs_mount *mp);
+void xchk_mount_stats_free(struct xfs_mount *mp);
+
+void xchk_stats_register(struct xchk_stats *cs, struct dentry *parent);
+void xchk_stats_unregister(struct xchk_stats *cs);
+
+void xchk_stats_merge(struct xfs_mount *mp, const struct xfs_scrub_metadata *sm,
+		const struct xchk_stats_run *run);
+
+static inline u64 xchk_stats_now(void) { return ktime_get_ns(); }
+static inline u64 xchk_stats_elapsed_ns(u64 since)
+{
+	u64 now = xchk_stats_now();
+
+	/*
+	 * If the system doesn't have a high enough resolution clock, charge at
+	 * least one nanosecond so that our stats don't report instantaneous
+	 * runtimes.
+	 */
+	if (now == since)
+		return 1;
+
+	return now - since;
+}
+#else
+# define xchk_global_stats_setup(parent)	(0)
+# define xchk_global_stats_teardown()		((void)0)
+# define xchk_mount_stats_alloc(mp)		(0)
+# define xchk_mount_stats_free(mp)		((void)0)
+# define xchk_stats_register(cs, parent)	((void)0)
+# define xchk_stats_unregister(cs)		((void)0)
+# define xchk_stats_now()			(0)
+# define xchk_stats_elapsed_ns(x)		(0 * (x))
+# define xchk_stats_merge(mp, sm, run)		((void)0)
+#endif /* CONFIG_XFS_ONLINE_SCRUB_STATS */
+
+#endif /* __XFS_SCRUB_STATS_H__ */
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 74dcb05069e8..e9d317a3dafe 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -63,6 +63,7 @@ typedef __u32			xfs_nlink_t;
 #include <linux/rhashtable.h>
 #include <linux/xattr.h>
 #include <linux/mnt_idmapping.h>
+#include <linux/debugfs.h>
 
 #include <asm/page.h>
 #include <asm/div64.h>
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index fb87ffb48f7f..0a0fd19573d8 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -34,6 +34,7 @@
 #include "xfs_health.h"
 #include "xfs_trace.h"
 #include "xfs_ag.h"
+#include "scrub/stats.h"
 
 static DEFINE_MUTEX(xfs_uuid_table_mutex);
 static int xfs_uuid_table_size;
@@ -716,9 +717,11 @@ xfs_mountfs(
 	if (error)
 		goto out_remove_sysfs;
 
+	xchk_stats_register(mp->m_scrub_stats, mp->m_debugfs);
+
 	error = xfs_error_sysfs_init(mp);
 	if (error)
-		goto out_del_stats;
+		goto out_remove_scrub_stats;
 
 	error = xfs_errortag_init(mp);
 	if (error)
@@ -1033,7 +1036,8 @@ xfs_mountfs(
 	xfs_errortag_del(mp);
  out_remove_error_sysfs:
 	xfs_error_sysfs_del(mp);
- out_del_stats:
+ out_remove_scrub_stats:
+	xchk_stats_unregister(mp->m_scrub_stats);
 	xfs_sysfs_del(&mp->m_stats.xs_kobj);
  out_remove_sysfs:
 	xfs_sysfs_del(&mp->m_kobj);
@@ -1105,6 +1109,7 @@ xfs_unmountfs(
 
 	xfs_errortag_del(mp);
 	xfs_error_sysfs_del(mp);
+	xchk_stats_unregister(mp->m_scrub_stats);
 	xfs_sysfs_del(&mp->m_stats.xs_kobj);
 	xfs_sysfs_del(&mp->m_kobj);
 }
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e2866e7fa60c..a25eece3be2b 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -208,11 +208,15 @@ typedef struct xfs_mount {
 	uint64_t		m_resblks_avail;/* available reserved blocks */
 	uint64_t		m_resblks_save;	/* reserved blks @ remount,ro */
 	struct delayed_work	m_reclaim_work;	/* background inode reclaim */
+	struct dentry		*m_debugfs;	/* debugfs parent */
 	struct xfs_kobj		m_kobj;
 	struct xfs_kobj		m_error_kobj;
 	struct xfs_kobj		m_error_meta_kobj;
 	struct xfs_error_cfg	m_error_cfg[XFS_ERR_CLASS_MAX][XFS_ERR_ERRNO_MAX];
 	struct xstats		m_stats;	/* per-fs stats */
+#ifdef CONFIG_XFS_ONLINE_SCRUB_STATS
+	struct xchk_stats	*m_scrub_stats;
+#endif
 	xfs_agnumber_t		m_agfrotor;	/* last ag where space found */
 	atomic_t		m_agirotor;	/* last ag dir inode alloced */
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 818510243130..09638e8fb4ee 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -42,6 +42,7 @@
 #include "xfs_xattr.h"
 #include "xfs_iunlink_item.h"
 #include "xfs_dahash_test.h"
+#include "scrub/stats.h"
 
 #include <linux/magic.h>
 #include <linux/fs_context.h>
@@ -49,6 +50,7 @@
 
 static const struct super_operations xfs_super_operations;
 
+static struct dentry *xfs_debugfs;	/* top-level xfs debugfs dir */
 static struct kset *xfs_kset;		/* top-level xfs sysfs dir */
 #ifdef DEBUG
 static struct xfs_kobj xfs_dbg_kobj;	/* global debug sysfs attrs */
@@ -758,6 +760,7 @@ static void
 xfs_mount_free(
 	struct xfs_mount	*mp)
 {
+	debugfs_remove(mp->m_debugfs);
 	kfree(mp->m_rtname);
 	kfree(mp->m_logname);
 	kmem_free(mp);
@@ -1142,6 +1145,7 @@ xfs_fs_put_super(
 	xfs_unmountfs(mp);
 
 	xfs_freesb(mp);
+	xchk_mount_stats_free(mp);
 	free_percpu(mp->m_stats.xs_stats);
 	xfs_mount_list_del(mp);
 	xfs_inodegc_free_percpu(mp);
@@ -1479,6 +1483,21 @@ xfs_fs_validate_params(
 	return 0;
 }
 
+struct dentry *
+xfs_debugfs_mkdir(
+	const char	*name,
+	struct dentry	*parent)
+{
+	struct dentry	*child;
+
+	/* Apparently we're expected to ignore error returns?? */
+	child = debugfs_create_dir(name, parent);
+	if (IS_ERR(child))
+		return NULL;
+
+	return child;
+}
+
 static int
 xfs_fs_fill_super(
 	struct super_block	*sb,
@@ -1521,6 +1540,13 @@ xfs_fs_fill_super(
 	if (error)
 		goto out_free_names;
 
+	if (xfs_debugfs) {
+		mp->m_debugfs = xfs_debugfs_mkdir(mp->m_super->s_id,
+						  xfs_debugfs);
+	} else {
+		mp->m_debugfs = NULL;
+	}
+
 	error = xfs_init_mount_workqueues(mp);
 	if (error)
 		goto out_close_devices;
@@ -1547,10 +1573,14 @@ xfs_fs_fill_super(
 		goto out_destroy_inodegc;
 	}
 
-	error = xfs_readsb(mp, flags);
+	error = xchk_mount_stats_alloc(mp);
 	if (error)
 		goto out_free_stats;
 
+	error = xfs_readsb(mp, flags);
+	if (error)
+		goto out_free_scrub_stats;
+
 	error = xfs_finish_flags(mp);
 	if (error)
 		goto out_free_sb;
@@ -1728,6 +1758,8 @@ xfs_fs_fill_super(
 	xfs_filestream_unmount(mp);
  out_free_sb:
 	xfs_freesb(mp);
+ out_free_scrub_stats:
+	xchk_mount_stats_free(mp);
  out_free_stats:
 	free_percpu(mp->m_stats.xs_stats);
  out_destroy_inodegc:
@@ -2353,10 +2385,12 @@ init_xfs_fs(void)
 	if (error)
 		goto out_cleanup_procfs;
 
+	xfs_debugfs = xfs_debugfs_mkdir("xfs", NULL);
+
 	xfs_kset = kset_create_and_add("xfs", NULL, fs_kobj);
 	if (!xfs_kset) {
 		error = -ENOMEM;
-		goto out_sysctl_unregister;
+		goto out_debugfs_unregister;
 	}
 
 	xfsstats.xs_kobj.kobject.kset = xfs_kset;
@@ -2372,11 +2406,15 @@ init_xfs_fs(void)
 	if (error)
 		goto out_free_stats;
 
+	error = xchk_global_stats_setup(xfs_debugfs);
+	if (error)
+		goto out_remove_stats_kobj;
+
 #ifdef DEBUG
 	xfs_dbg_kobj.kobject.kset = xfs_kset;
 	error = xfs_sysfs_init(&xfs_dbg_kobj, &xfs_dbg_ktype, NULL, "debug");
 	if (error)
-		goto out_remove_stats_kobj;
+		goto out_remove_scrub_stats;
 #endif
 
 	error = xfs_qm_init();
@@ -2393,14 +2431,17 @@ init_xfs_fs(void)
  out_remove_dbg_kobj:
 #ifdef DEBUG
 	xfs_sysfs_del(&xfs_dbg_kobj);
- out_remove_stats_kobj:
+ out_remove_scrub_stats:
 #endif
+	xchk_global_stats_teardown();
+ out_remove_stats_kobj:
 	xfs_sysfs_del(&xfsstats.xs_kobj);
  out_free_stats:
 	free_percpu(xfsstats.xs_stats);
  out_kset_unregister:
 	kset_unregister(xfs_kset);
- out_sysctl_unregister:
+ out_debugfs_unregister:
+	debugfs_remove(xfs_debugfs);
 	xfs_sysctl_unregister();
  out_cleanup_procfs:
 	xfs_cleanup_procfs();
@@ -2424,9 +2465,11 @@ exit_xfs_fs(void)
 #ifdef DEBUG
 	xfs_sysfs_del(&xfs_dbg_kobj);
 #endif
+	xchk_global_stats_teardown();
 	xfs_sysfs_del(&xfsstats.xs_kobj);
 	free_percpu(xfsstats.xs_stats);
 	kset_unregister(xfs_kset);
+	debugfs_remove(xfs_debugfs);
 	xfs_sysctl_unregister();
 	xfs_cleanup_procfs();
 	xfs_mru_cache_uninit();
diff --git a/fs/xfs/xfs_super.h b/fs/xfs/xfs_super.h
index 364e2c2648a8..302e6e5d6c7e 100644
--- a/fs/xfs/xfs_super.h
+++ b/fs/xfs/xfs_super.h
@@ -100,4 +100,6 @@ extern struct workqueue_struct *xfs_discard_wq;
 
 #define XFS_M(sb)		((struct xfs_mount *)((sb)->s_fs_info))
 
+struct dentry *xfs_debugfs_mkdir(const char *name, struct dentry *parent);
+
 #endif	/* __XFS_SUPER_H__ */