On 19.02.2021 19:48, Chuck Lever wrote: > > >> On Feb 19, 2021, at 1:01 PM, Timo Rothenpieler wrote: >> >> On 19.02.2021 18:48, Chuck Lever wrote: >>>> On Feb 19, 2021, at 12:38 PM, Olga Kornievskaia wrote: >>>> >>>> On Thu, Feb 18, 2021 at 3:22 PM Timo Rothenpieler wrote: >>>>> >>>>> On 18.02.2021 19:30, Olga Kornievskaia wrote: >>>>>> Thank you for getting tracepoints from a busy server but can you get >>>>>> more? As suspected, the server is having issues sending the callback. >>>>>> I'm not sure why. Any chance to turn on the server's sunrpc >>>>>> tracespoints, probably both sunrpc and rdmas tracepoints, I wonder if >>>>>> we can any more info about why it's failing? >>>>> >>>>> I isolated out two of the machines on that cluster now, one acting as >>>>> NFS server from an ext4 mount, the other is the same client as before. >>>>> That way I managed to capture a trace and ibdump of an entire cycle: >>>>> mount + successful copy + 5 minutes later a copy that got stuck >>>>> >>>>> Next to no noise happened during those traces, you can find them attached. >>>>> >>>>> Another observation made due to this: unmount and re-mounting the NFS >>>>> share also gets it back into working condition for a while, no reboot >>>>> necessary. >>>>> During this trace, I got "lucky", and after just 5 minutes of waiting, >>>>> it got stuck. >>>>> >>>>> Before that, I had a run of mount + trying to copy every 5 minutes where >>>>> it ran for 45 minutes without getting stuck. At which point I decided to >>>>> remount once more. >>>> >>>> Timo, thank you for gathering the debug info. >>>> >>>> Chuck, I need your help. Why would the server lose a callback channel? >>>> >>>> <...>-1461944 [001] 2076465.200151: rpc_request: >>>> task:57752@6 nfs4_cbv1 CB_OFFLOAD (async) >>>> <...>-1461944 [001] 2076465.200151: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_reserve >>>> <...>-1461944 [001] 2076465.200154: xprt_reserve: >>>> task:57752@6 xid=0x00a0aaf9 >>>> <...>-1461944 [001] 2076465.200155: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_reserveresult >>>> <...>-1461944 [001] 2076465.200156: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_refresh >>>> <...>-1461944 [001] 2076465.200163: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_refreshresult >>>> <...>-1461944 [001] 2076465.200163: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_allocate >>>> <...>-1461944 [001] 2076465.200168: rpc_buf_alloc: >>>> task:57752@6 callsize=548 recvsize=104 status=0 >>>> <...>-1461944 [001] 2076465.200168: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE status=0 action=call_encode >>>> <...>-1461944 [001] 2076465.200173: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE|NEED_XMIT|NEED_RECV status=0 >>>> action=call_connect >>>> <...>-1461944 [001] 2076465.200174: rpc_call_rpcerror: >>>> task:57752@6 tk_status=-107 rpc_status=-107 >>>> <...>-1461944 [001] 2076465.200174: rpc_task_run_action: >>>> task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT >>>> runstate=RUNNING|ACTIVE|NEED_XMIT|NEED_RECV status=-107 >>>> action=rpc_exit_task >>>> >>>> It's reporting ENOTCON. I'm not really sure if this is related to copy >>>> offload but more perhaps doing callbacks over RDMA/IB. >>> If the client is awaiting a COPY notification callback, I can see why >>> a lost CB channel would cause the client to wait indefinitely. >>> The copy mechanism has to deal with this contingency... Perhaps the >>> server could force a disconnect so that the client and server have an >>> opportunity to re-establish the callback channel. >>> In any event, the trace log above shows nothing more than "hey, it's >>> not working." Are there any rpcrdma trace events we can look at to >>> determine why the backchannel is getting lost? >> >> The trace log attached to my previous mail has it enabled, along with nfsd and sunrpc. >> I'm attaching the two files again here. > > Thanks, Timo. > > The first CB_OFFLOAD callback succeeds: > > 2076155.216687: nfsd_cb_work: addr=10.110.10.252:0 client 602eb645:daa037ae procedure=CB_OFFLOAD > 2076155.216704: rpc_request: task:57746@6 nfs4_cbv1 CB_OFFLOAD (async) > > 2076155.216975: rpc_stats_latency: task:57746@6 xid=0xff9faaf9 nfs4_cbv1 CB_OFFLOAD backlog=33 rtt=195 execute=282 > 2076155.216977: nfsd_cb_done: addr=10.110.10.252:0 client 602eb645:daa037ae status=0 > > > About 305 seconds later, the autodisconnect timer fires. I'm not sure if this is the backchannel transport, but it looks suspicious: > > 2076460.314954: xprt_disconnect_auto: peer=[10.110.10.252]:0 state=LOCKED|CONNECTED|BOUND > 2076460.314957: xprt_disconnect_done: peer=[10.110.10.252]:0 state=LOCKED|CONNECTED|BOUND > > > The next CB_OFFLOAD callback fails because the xprt has been marked "disconnected" and the request's NOCONNECT flag is set. > > 2076465.200136: nfsd_cb_work: addr=10.110.10.252:0 client 602eb645:daa037ae procedure=CB_OFFLOAD > 2076465.200151: rpc_request: task:57752@6 nfs4_cbv1 CB_OFFLOAD (async) > > 2076465.200168: rpc_task_run_action: task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT runstate=RUNNING|ACTIVE status=0 action=call_encode > 2076465.200173: rpc_task_run_action: task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT runstate=RUNNING|ACTIVE|NEED_XMIT|NEED_RECV status=0 action=call_connect > 2076465.200174: rpc_call_rpcerror: task:57752@6 tk_status=-107 rpc_status=-107 > 2076465.200174: rpc_task_run_action: task:57752@6 flags=ASYNC|DYNAMIC|SOFT|NOCONNECT runstate=RUNNING|ACTIVE|NEED_XMIT|NEED_RECV status=-107 action=rpc_exit_task > 2076465.200179: nfsd_cb_done: addr=10.110.10.252:0 client 602eb645:daa037ae status=-107 > 2076465.200180: nfsd_cb_state: addr=10.110.10.252:0 client 602eb645:daa037ae state=FAULT > > > Perhaps RPC clients for NFSv4.1+ callback should be created with > the RPC_CLNT_CREATE_NO_IDLE_TIMEOUT flag. I added that flag to the callback client creation flags, and so far after a few hours of uptime, copying still works. Can't say anything about that being the appropriate fix for the issue at hand, as I lack the necessary insight into the NFS code, but I'll leave it running like that for now and observe. Can also gladly test any other patches. Thanks, Timo