From: Mike Snitzer <snitzer@kernel.org>
To: Anna Schumaker <anna@kernel.org>, Trond Myklebust <trondmy@kernel.org>
Cc: Mike Snitzer <snitzer@hammerspace.com>,
linux-nfs@vger.kernel.org,
Jonathan Flynn <jonathan.flynn@hammerspace.com>
Subject: [PATCH v2 11/12] NFSv4/flexfiles: take the report decision out of the critical section
Date: Thu, 5 Nov 2026 19:12:48 -0500 [thread overview]
Message-ID: <20261106001251.73472-12-snitzer@kernel.org> (raw)
In-Reply-To: <20261106001251.73472-1-snitzer@kernel.org>
From: Mike Snitzer <snitzer@hammerspace.com>
When an I/O to a data server starts, the stripe lock also covered the
decision to send a LAYOUTSTATS report. That decision reads the mirror
and the layout header, divides in ktime_to_ms(), and does a cmpxchg on
ffl->last_report_time. None of it is data that the lock protects.
Move the decision into nfs4_ff_layoutstat_report_due() and call it,
and nfs4_ff_layoutstat_set_start_time(), after the unlock. The lock now
covers two writes to one cacheline. The order of the updates and the
report does not change.
nfs4_ff_layoutstat_end_io() loses its unused dss_info argument.
Signed-off-by: Mike Snitzer <snitzer@hammerspace.com>
---
fs/nfs/flexfilelayout/flexfilelayout.c | 49 ++++++++++++++------------
1 file changed, 27 insertions(+), 22 deletions(-)
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index b4d4971816145..f3f4573880d98 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -739,32 +739,36 @@ nfs4_ff_layoutstat_set_start_time(struct nfs4_ff_layout_ds_stripe *dss_info,
try_cmpxchg64(&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_ds_stripe *dss_info,
- struct nfs4_ff_layoutstat *layoutstat,
+/* Account for an I/O about to be sent to this stripe. */
+static void
+nfs4_ff_layoutstat_start_io(struct nfs4_ff_layoutstat *layoutstat,
__u64 requested, ktime_t now)
+{
+ lockdep_assert_held(&layoutstat->lock);
+
+ nfs4_ff_start_busy_timer(layoutstat, now);
+ layoutstat->io_stat.bytes_requested += requested;
+}
+
+/*
+ * Is a LAYOUTSTATS report due? Called outside the statistics locks, which
+ * protect none of this. last_report_time is shared by every mirror and
+ * stripe of the layout: the cmpxchg winner reports.
+ */
+static bool
+nfs4_ff_layoutstat_report_due(struct nfs4_ff_layout_ds_stripe *dss_info,
+ ktime_t now)
{
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;
ktime_t last_report;
- lockdep_assert_held(&layoutstat->lock);
-
- nfs4_ff_start_busy_timer(layoutstat, now);
- 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)
report_interval = (s64)layoutstats_timer * 1000LL;
- /* Shared by every mirror and stripe: the cmpxchg winner reports. */
last_report = READ_ONCE(ffl->last_report_time);
if (ktime_to_ms(ktime_sub(now, last_report)) < report_interval)
return false;
@@ -774,8 +778,7 @@ nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_ds_stripe *dss_info,
/* Account for an I/O that has completed on this stripe. */
static void
-nfs4_ff_layoutstat_end_io(struct nfs4_ff_layout_ds_stripe *dss_info,
- struct nfs4_ff_layoutstat *layoutstat,
+nfs4_ff_layoutstat_end_io(struct nfs4_ff_layoutstat *layoutstat,
__u64 requested,
__u64 completed,
ktime_t time_completed,
@@ -809,10 +812,11 @@ nfs4_ff_layout_stat_io_start_read(struct inode *inode,
bool report;
spin_lock(&dss_info->read_stat.lock);
- report = nfs4_ff_layoutstat_start_io(dss_info, &dss_info->read_stat,
- requested, now);
+ nfs4_ff_layoutstat_start_io(&dss_info->read_stat, requested, now);
spin_unlock(&dss_info->read_stat.lock);
+ nfs4_ff_layoutstat_set_start_time(dss_info, now);
+ report = nfs4_ff_layoutstat_report_due(dss_info, now);
if (report)
pnfs_report_layoutstat(inode, nfs_io_gfp_mask());
}
@@ -827,7 +831,7 @@ nfs4_ff_layout_stat_io_end_read(struct rpc_task *task,
struct nfs4_ff_layout_ds_stripe *dss_info = &mirror->dss[dss_id];
spin_lock(&dss_info->read_stat.lock);
- nfs4_ff_layoutstat_end_io(dss_info, &dss_info->read_stat,
+ nfs4_ff_layoutstat_end_io(&dss_info->read_stat,
requested, completed,
ktime_get(), task->tk_start);
spin_unlock(&dss_info->read_stat.lock);
@@ -843,10 +847,11 @@ nfs4_ff_layout_stat_io_start_write(struct inode *inode,
bool report;
spin_lock(&dss_info->write_stat.lock);
- report = nfs4_ff_layoutstat_start_io(dss_info, &dss_info->write_stat,
- requested, now);
+ nfs4_ff_layoutstat_start_io(&dss_info->write_stat, requested, now);
spin_unlock(&dss_info->write_stat.lock);
+ nfs4_ff_layoutstat_set_start_time(dss_info, now);
+ report = nfs4_ff_layoutstat_report_due(dss_info, now);
if (report)
pnfs_report_layoutstat(inode, nfs_io_gfp_mask());
}
@@ -865,7 +870,7 @@ nfs4_ff_layout_stat_io_end_write(struct rpc_task *task,
requested = completed = 0;
spin_lock(&dss_info->write_stat.lock);
- nfs4_ff_layoutstat_end_io(dss_info, &dss_info->write_stat,
+ nfs4_ff_layoutstat_end_io(&dss_info->write_stat,
requested, completed,
ktime_get(), task->tk_start);
spin_unlock(&dss_info->write_stat.lock);
--
2.52.0
next prev parent reply other threads:[~2026-11-06 0:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-06 0:12 [PATCH v2 00/12] NFSv4/flexfiles: scale layoutstats for striped layouts Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 01/12] NFSv4/flexfiles: move layoutstats accounting to a per-stripe lock Mike Snitzer
2026-11-06 12:28 ` kernel test robot
2026-11-06 0:12 ` [PATCH v2 02/12] NFSv4/flexfiles: drop the now-unused per-mirror lock Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 03/12] NFSv4/flexfiles: cacheline align the per-stripe layoutstats Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 04/12] NFSv4/flexfiles: make dss_info->start_time write-once Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 05/12] NFSv4/flexfiles: drop the redundant atomic from the busy timer Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 06/12] NFSv4/flexfiles: pair the in-flight count with the layoutstats updates Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 07/12] NFSv4/flexfiles: derive ffil_ops_requested rather than storing it Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 08/12] NFSv4/flexfiles: give each direction its own lock and cacheline Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 09/12] NFSv4/flexfiles: drop NFS4_FF_MIRROR_STAT_AVAIL Mike Snitzer
2026-11-06 0:12 ` [PATCH v2 10/12] NFSv4/flexfiles: rotate LAYOUTSTATS reporting across a mirror's stripes Mike Snitzer
2026-11-06 0:12 ` Mike Snitzer [this message]
2026-11-06 0:12 ` [PATCH v2 12/12] NFSv4/flexfiles: share one helper for the start of a read and a write Mike Snitzer
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