[PATCH v3 07/12] NFSv4/flexfiles: derive ffil_ops_requested rather than storing it

[Mike Snitzer <snitzer@kernel.org>]

From: Mike Snitzer <snitzer@hammerspace.com>

An op is in flight from when it is counted as requested until it is
counted as completed.  After the previous patch both counts are kept
together under one lock, so

        ops_requested == ops_completed + ops_in_flight

at all times.  Drop nfs4_ff_io_stat::ops_requested and compute it when
LAYOUTSTATS is encoded.  The wire format does not change.

This removes 8 bytes from each direction's statistics, which the next
patch needs.

Signed-off-by: Mike Snitzer <snitzer@hammerspace.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 12 +++++-------
 fs/nfs/flexfilelayout/flexfilelayout.h |  9 ++++++++-
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index a5460c6ec2b4d..23a8ae68aa5cc 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -755,7 +755,6 @@ nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_ds_stripe *dss_info,
 	lockdep_assert_held(&dss_info->lock);
 
 	nfs4_ff_start_busy_timer(&layoutstat->busy_timer, now);
-	layoutstat->io_stat.ops_requested++;
 	layoutstat->io_stat.bytes_requested += requested;
 
 	nfs4_ff_layoutstat_set_start_time(dss_info, now);
@@ -3049,12 +3048,13 @@ ff_layout_encode_nfstime(struct xdr_stream *xdr,
 
 static void
 ff_layout_encode_io_latency(struct xdr_stream *xdr,
-			    struct nfs4_ff_io_stat *stat)
+			    const struct nfs4_ff_layoutstat *layoutstat)
 {
+	const struct nfs4_ff_io_stat *stat = &layoutstat->io_stat;
 	__be32 *p;
 
 	p = xdr_reserve_space(xdr, 5 * 8);
-	p = xdr_encode_hyper(p, stat->ops_requested);
+	p = xdr_encode_hyper(p, nfs4_ff_ops_requested(layoutstat));
 	p = xdr_encode_hyper(p, stat->bytes_requested);
 	p = xdr_encode_hyper(p, stat->ops_completed);
 	p = xdr_encode_hyper(p, stat->bytes_completed);
@@ -3084,11 +3084,9 @@ ff_layout_encode_ff_layoutupdate(struct xdr_stream *xdr,
 	xdr_encode_opaque(p, fh->data, fh->size);
 	/* ff_io_latency4 read */
 	spin_lock(&dss_info->lock);
-	ff_layout_encode_io_latency(xdr,
-				    &dss_info->read_stat.io_stat);
+	ff_layout_encode_io_latency(xdr, &dss_info->read_stat);
 	/* ff_io_latency4 write */
-	ff_layout_encode_io_latency(xdr,
-				    &dss_info->write_stat.io_stat);
+	ff_layout_encode_io_latency(xdr, &dss_info->write_stat);
 	spin_unlock(&dss_info->lock);
 	/* nfstime4 */
 	ff_layout_encode_nfstime(xdr,
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index 93fbc22b43c37..caa4c1e63063f 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -55,7 +55,6 @@ struct nfs4_ff_layout_ds_err {
 };
 
 struct nfs4_ff_io_stat {
-	__u64				ops_requested;
 	__u64				bytes_requested;
 	__u64				ops_completed;
 	__u64				bytes_completed;
@@ -75,6 +74,14 @@ struct nfs4_ff_layoutstat {
 	struct nfs4_ff_busy_timer busy_timer;
 };
 
+/* Caller must hold the lock guarding this nfs4_ff_layoutstat. */
+static inline __u64
+nfs4_ff_ops_requested(const struct nfs4_ff_layoutstat *layoutstat)
+{
+	return layoutstat->io_stat.ops_completed +
+	       layoutstat->busy_timer.ops_in_flight;
+}
+
 struct nfs4_ff_layout_mirror;
 
 struct nfs4_ff_layout_ds_stripe {
-- 
2.52.0