xfs: track usage statistics of online fsck

Track the usage, outcomes, and run times of the online fsck code, and
report these values via debugfs.  The columns in the file are:

 * scrubber name

 * number of scrub invocations
 * clean objects found
 * corruptions found
 * optimizations found
 * cross referencing failures
 * inconsistencies found during cross referencing
 * incomplete scrubs
 * warnings
 * number of time scrub had to retry
 * cumulative amount of time spent scrubbing (microseconds)

 * number of repair inovcations
 * successfully repaired objects
 * cumuluative amount of time spent repairing (microseconds)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

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

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
 

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;
 		}
 		/*

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;
 }

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 @@ xfs_scrub_metadata(
 		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 @@ xfs_scrub_metadata(
 		 * 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 @@ xfs_scrub_metadata(
 		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 @@ xfs_scrub_metadata(
 	if (error)
 		goto out_sc;
 	sc->flags |= XCHK_TRY_HARDER;
+	run.retries++;
 	goto retry_op;
 }