Hi Trond- > On Dec 3, 2017, at 7:17 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote: > > We must ensure that the call to rpc_sleep_on() in xprt_transmit() cannot > race with the call to xprt_complete_rqst(). > > Reported-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=317 > Fixes: ce7c252a8c74 ("SUNRPC: Add a separate spinlock to protect..") > Cc: stable@xxxxxxxxxxxxxxx # 4.14+ > Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > --- > net/sunrpc/xprt.c | 26 +++++++++++++++++--------- > 1 file changed, 17 insertions(+), 9 deletions(-) > > diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c > index 333b9d697ae5..5e4278e9ce37 100644 > --- a/net/sunrpc/xprt.c > +++ b/net/sunrpc/xprt.c > @@ -1024,6 +1024,7 @@ void xprt_transmit(struct rpc_task *task) > } else if (!req->rq_bytes_sent) > return; > > + req->rq_connect_cookie = xprt->connect_cookie; > req->rq_xtime = ktime_get(); > status = xprt->ops->send_request(task); > trace_xprt_transmit(xprt, req->rq_xid, status); > @@ -1047,20 +1048,27 @@ void xprt_transmit(struct rpc_task *task) > xprt->stat.bklog_u += xprt->backlog.qlen; > xprt->stat.sending_u += xprt->sending.qlen; > xprt->stat.pending_u += xprt->pending.qlen; > + spin_unlock_bh(&xprt->transport_lock); > > - /* Don't race with disconnect */ > - if (!xprt_connected(xprt)) > - task->tk_status = -ENOTCONN; > - else { > + if (rpc_reply_expected(task) && !READ_ONCE(req->rq_reply_bytes_recvd)) { > /* > - * Sleep on the pending queue since > - * we're expecting a reply. > + * Sleep on the pending queue if we're expecting a reply. > + * The spinlock ensures atomicity between the test of > + * req->rq_reply_bytes_recvd, and the call to rpc_sleep_on(). > */ > - if (!req->rq_reply_bytes_recvd && rpc_reply_expected(task)) > + spin_lock(&xprt->recv_lock); > + if (!req->rq_reply_bytes_recvd) { > rpc_sleep_on(&xprt->pending, task, xprt_timer); > - req->rq_connect_cookie = xprt->connect_cookie; > + /* > + * Send an extra queue wakeup call if the > + * connection was dropped in case the call to > + * rpc_sleep_on() raced. > + */ > + if (!xprt_connected(xprt)) > + xprt_wake_pending_tasks(xprt, -ENOTCONN); > + } > + spin_unlock(&xprt->recv_lock); > } > - spin_unlock_bh(&xprt->transport_lock); > } > > static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task) > -- > 2.14.3 I've run into a problem with this version of the patch (on v4.15-rc3). With dbench on NFSv4.0 (on RDMA) I no longer see constant throughput and a temporarily climbing latency followed by a recovery, but this can happen on occasion: releasing clients 16 584 322.55 MB/sec warmup 1 sec latency 807.121 ms 16 584 161.28 MB/sec warmup 2 sec latency 1807.175 ms 16 584 107.52 MB/sec warmup 3 sec latency 2807.198 ms 16 584 80.64 MB/sec warmup 4 sec latency 3807.217 ms 16 584 64.51 MB/sec warmup 5 sec latency 4807.235 ms 16 584 53.76 MB/sec warmup 6 sec latency 5807.251 ms 16 584 46.08 MB/sec warmup 7 sec latency 6807.269 ms 16 584 40.32 MB/sec warmup 8 sec latency 7807.285 ms 16 584 35.84 MB/sec warmup 9 sec latency 8807.303 ms 16 584 32.26 MB/sec warmup 10 sec latency 9807.318 ms 16 584 29.32 MB/sec warmup 11 sec latency 10807.334 ms 16 584 26.88 MB/sec warmup 12 sec latency 11807.355 ms 16 584 24.81 MB/sec warmup 13 sec latency 12807.372 ms 16 584 23.04 MB/sec warmup 14 sec latency 13807.387 ms 16 584 21.50 MB/sec warmup 15 sec latency 14807.406 ms 16 584 20.16 MB/sec warmup 16 sec latency 15807.423 ms No recovery. The latency number keeps climbing, and throughput drops. "kernel: nfs: server klimt-ib not responding, still trying" appears in the client's /var/log/messages. Without this patch applied, the NFSv4.0 behavior is the same as I reported with NFSv3: every once in a while, one RPC completion is lost, but when the timer fires, the client notices the reply actually did arrive and the RPC completes normally. I'm looking into it. -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
