[PATCH v3 06/12] NFSv4/flexfiles: pair the in-flight count with the layoutstats updates

[Mike Snitzer <snitzer@kernel.org>]

From: Mike Snitzer <snitzer@hammerspace.com>

The in-flight count of the busy timer and the requested-side statistics
are two halves of one count, but the callers update them through two
helpers.  A new path could update one and not the other.

Fold nfs4_ff_layout_stat_io_update_requested() into
nfs4_ff_layoutstat_start_io(), and rename
nfs4_ff_layout_stat_io_update_completed() to
nfs4_ff_layoutstat_end_io().  Rename n_ops to ops_in_flight, which is
what it counts.

Both helpers now take the stripe, so they can assert the lock that
protects ops_in_flight.

No functional change.

Signed-off-by: Mike Snitzer <snitzer@hammerspace.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 96 +++++++++++++-------------
 fs/nfs/flexfilelayout/flexfilelayout.h |  2 +-
 2 files changed, 50 insertions(+), 48 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 81c3d9dd413e5..a5460c6ec2b4d 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -711,7 +711,7 @@ static void
 nfs4_ff_start_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
 {
 	/* first IO request? */
-	if (++timer->n_ops == 1)
+	if (++timer->ops_in_flight == 1)
 		timer->start_time = now;
 }
 
@@ -720,7 +720,7 @@ nfs4_ff_end_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
 {
 	ktime_t start;
 
-	WARN_ON_ONCE(--timer->n_ops < 0);
+	WARN_ON_ONCE(--timer->ops_in_flight < 0);
 
 	start = timer->start_time;
 	timer->start_time = now;
@@ -738,18 +738,27 @@ nfs4_ff_layoutstat_set_start_time(struct nfs4_ff_layout_ds_stripe *dss_info,
 		atomic64_try_cmpxchg(&dss_info->start_time, &unset, now);
 }
 
+/*
+ * Account for an I/O about to be sent to this stripe, and return true if a
+ * LAYOUTSTATS report is due.
+ */
 static bool
-nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror,
-			    u32 dss_id,
+nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_ds_stripe *dss_info,
 			    struct nfs4_ff_layoutstat *layoutstat,
-			    ktime_t now)
+			    __u64 requested, ktime_t now)
 {
-	s64 report_interval = FF_LAYOUTSTATS_REPORT_INTERVAL;
+	struct nfs4_ff_layout_mirror *mirror = dss_info->mirror;
 	struct nfs4_flexfile_layout *ffl = FF_LAYOUT_FROM_HDR(mirror->layout);
+	s64 report_interval = FF_LAYOUTSTATS_REPORT_INTERVAL;
 	s64 last_report;
 
+	lockdep_assert_held(&dss_info->lock);
+
 	nfs4_ff_start_busy_timer(&layoutstat->busy_timer, now);
-	nfs4_ff_layoutstat_set_start_time(&mirror->dss[dss_id], now);
+	layoutstat->io_stat.ops_requested++;
+	layoutstat->io_stat.bytes_requested += requested;
+
+	nfs4_ff_layoutstat_set_start_time(dss_info, now);
 	if (mirror->report_interval != 0)
 		report_interval = (s64)mirror->report_interval * 1000LL;
 	else if (layoutstats_timer != 0)
@@ -763,27 +772,21 @@ nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror,
 	return atomic64_try_cmpxchg(&ffl->last_report_time, &last_report, now);
 }
 
+/* Account for an I/O that has completed on this stripe. */
 static void
-nfs4_ff_layout_stat_io_update_requested(struct nfs4_ff_layoutstat *layoutstat,
-		__u64 requested)
-{
-	struct nfs4_ff_io_stat *iostat = &layoutstat->io_stat;
-
-	iostat->ops_requested++;
-	iostat->bytes_requested += requested;
-}
-
-static void
-nfs4_ff_layout_stat_io_update_completed(struct nfs4_ff_layoutstat *layoutstat,
-		__u64 requested,
-		__u64 completed,
-		ktime_t time_completed,
-		ktime_t time_started)
+nfs4_ff_layoutstat_end_io(struct nfs4_ff_layout_ds_stripe *dss_info,
+			  struct nfs4_ff_layoutstat *layoutstat,
+			  __u64 requested,
+			  __u64 completed,
+			  ktime_t time_completed,
+			  ktime_t time_started)
 {
 	struct nfs4_ff_io_stat *iostat = &layoutstat->io_stat;
 	ktime_t completion_time = ktime_sub(time_completed, time_started);
 	ktime_t timer;
 
+	lockdep_assert_held(&dss_info->lock);
+
 	iostat->ops_completed++;
 	iostat->bytes_completed += completed;
 	iostat->bytes_not_delivered += requested - completed;
@@ -802,14 +805,13 @@ nfs4_ff_layout_stat_io_start_read(struct inode *inode,
 		u32 dss_id,
 		__u64 requested, ktime_t now)
 {
+	struct nfs4_ff_layout_ds_stripe *dss_info = &mirror->dss[dss_id];
 	bool report;
 
-	spin_lock(&mirror->dss[dss_id].lock);
-	report = nfs4_ff_layoutstat_start_io(
-		mirror, dss_id, &mirror->dss[dss_id].read_stat, now);
-	nfs4_ff_layout_stat_io_update_requested(
-		&mirror->dss[dss_id].read_stat, requested);
-	spin_unlock(&mirror->dss[dss_id].lock);
+	spin_lock(&dss_info->lock);
+	report = nfs4_ff_layoutstat_start_io(dss_info, &dss_info->read_stat,
+					     requested, now);
+	spin_unlock(&dss_info->lock);
 	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
 
 	if (report)
@@ -823,11 +825,13 @@ nfs4_ff_layout_stat_io_end_read(struct rpc_task *task,
 		__u64 requested,
 		__u64 completed)
 {
-	spin_lock(&mirror->dss[dss_id].lock);
-	nfs4_ff_layout_stat_io_update_completed(&mirror->dss[dss_id].read_stat,
-			requested, completed,
-			ktime_get(), task->tk_start);
-	spin_unlock(&mirror->dss[dss_id].lock);
+	struct nfs4_ff_layout_ds_stripe *dss_info = &mirror->dss[dss_id];
+
+	spin_lock(&dss_info->lock);
+	nfs4_ff_layoutstat_end_io(dss_info, &dss_info->read_stat,
+				  requested, completed,
+				  ktime_get(), task->tk_start);
+	spin_unlock(&dss_info->lock);
 	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
 }
 
@@ -837,18 +841,13 @@ nfs4_ff_layout_stat_io_start_write(struct inode *inode,
 		u32 dss_id,
 		__u64 requested, ktime_t now)
 {
+	struct nfs4_ff_layout_ds_stripe *dss_info = &mirror->dss[dss_id];
 	bool report;
 
-	spin_lock(&mirror->dss[dss_id].lock);
-	report = nfs4_ff_layoutstat_start_io(
-		mirror,
-		dss_id,
-		&mirror->dss[dss_id].write_stat,
-		now);
-	nfs4_ff_layout_stat_io_update_requested(
-		&mirror->dss[dss_id].write_stat,
-		requested);
-	spin_unlock(&mirror->dss[dss_id].lock);
+	spin_lock(&dss_info->lock);
+	report = nfs4_ff_layoutstat_start_io(dss_info, &dss_info->write_stat,
+					     requested, now);
+	spin_unlock(&dss_info->lock);
 	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
 
 	if (report)
@@ -863,13 +862,16 @@ nfs4_ff_layout_stat_io_end_write(struct rpc_task *task,
 		__u64 completed,
 		enum nfs3_stable_how committed)
 {
+	struct nfs4_ff_layout_ds_stripe *dss_info = &mirror->dss[dss_id];
+
 	if (committed == NFS_UNSTABLE)
 		requested = completed = 0;
 
-	spin_lock(&mirror->dss[dss_id].lock);
-	nfs4_ff_layout_stat_io_update_completed(&mirror->dss[dss_id].write_stat,
-			requested, completed, ktime_get(), task->tk_start);
-	spin_unlock(&mirror->dss[dss_id].lock);
+	spin_lock(&dss_info->lock);
+	nfs4_ff_layoutstat_end_io(dss_info, &dss_info->write_stat,
+				  requested, completed,
+				  ktime_get(), task->tk_start);
+	spin_unlock(&dss_info->lock);
 	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
 }
 
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index 483d730659713..93fbc22b43c37 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -67,7 +67,7 @@ struct nfs4_ff_io_stat {
 /* Both members are protected by the enclosing stripe's lock */
 struct nfs4_ff_busy_timer {
 	ktime_t start_time;
-	int n_ops;
+	int ops_in_flight;
 };
 
 struct nfs4_ff_layoutstat {
-- 
2.52.0