From edef1297f33a4546559d905457b435a5ea160bab Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Sat, 8 Nov 2014 20:15:09 -0500 Subject: SUNRPC: serialize iostats updates Occasionally mountstats reports a negative retransmission rate. Ensure that two RPCs completing concurrently don't confuse the sums in the transport's op_metrics array. Since pNFS filelayout can invoke rpc_count_iostats() on another transport from xprt_release(), we can't rely on simply holding the transport_lock in xprt_release(). There's nothing for it but hard serialization. One spin lock per RPC operation should make this as painless as it can be. Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker --- net/sunrpc/stats.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) (limited to 'net/sunrpc') diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c index 54530490944..9711a155bc5 100644 --- a/net/sunrpc/stats.c +++ b/net/sunrpc/stats.c @@ -116,7 +116,15 @@ EXPORT_SYMBOL_GPL(svc_seq_show); */ struct rpc_iostats *rpc_alloc_iostats(struct rpc_clnt *clnt) { - return kcalloc(clnt->cl_maxproc, sizeof(struct rpc_iostats), GFP_KERNEL); + struct rpc_iostats *stats; + int i; + + stats = kcalloc(clnt->cl_maxproc, sizeof(*stats), GFP_KERNEL); + if (stats) { + for (i = 0; i < clnt->cl_maxproc; i++) + spin_lock_init(&stats[i].om_lock); + } + return stats; } EXPORT_SYMBOL_GPL(rpc_alloc_iostats); @@ -135,20 +143,21 @@ EXPORT_SYMBOL_GPL(rpc_free_iostats); * rpc_count_iostats - tally up per-task stats * @task: completed rpc_task * @stats: array of stat structures - * - * Relies on the caller for serialization. */ void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats) { struct rpc_rqst *req = task->tk_rqstp; struct rpc_iostats *op_metrics; - ktime_t delta; + ktime_t delta, now; if (!stats || !req) return; + now = ktime_get(); op_metrics = &stats[task->tk_msg.rpc_proc->p_statidx]; + spin_lock(&op_metrics->om_lock); + op_metrics->om_ops++; op_metrics->om_ntrans += req->rq_ntrans; op_metrics->om_timeouts += task->tk_timeouts; @@ -161,8 +170,10 @@ void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats) op_metrics->om_rtt = ktime_add(op_metrics->om_rtt, req->rq_rtt); - delta = ktime_sub(ktime_get(), task->tk_start); + delta = ktime_sub(now, task->tk_start); op_metrics->om_execute = ktime_add(op_metrics->om_execute, delta); + + spin_unlock(&op_metrics->om_lock); } EXPORT_SYMBOL_GPL(rpc_count_iostats); -- cgit v1.2.3-70-g09d2