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From: Andy Chittenden on 27 Jul 2010 09:00 On 2010-07-27 13:21, Eric Dumazet wrote: > Le mardi 27 juillet 2010 à 11:53 +0100, Andy Chittenden a écrit : >>>>> IE the client starts a connection and then closes it again without sending data. >>>> Once this happens, here's some rpcdebug info for the rpc module using 2.6.34.1 kernel: >>>> >>>> ... lots of the following nfsv3 WRITE requests: >>>> [ 7670.026741] 57793 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026759] 57794 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026778] 57795 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026797] 57796 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026815] 57797 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026834] 57798 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026853] 57799 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026871] 57800 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026890] 57801 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026909] 57802 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7680.520042] RPC: worker connecting xprt ffff88013e62d800 via tcp to 10.1.6.102 (port 2049) >>>> [ 7680.520066] RPC: ffff88013e62d800 connect status 99 connected 0 sock state 7 >>>> [ 7680.520074] RPC: 33550 __rpc_wake_up_task (now 4296812426) >>>> [ 7680.520079] RPC: 33550 disabling timer >>>> [ 7680.520084] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" >>>> [ 7680.520089] RPC: __rpc_wake_up_task done >>>> [ 7680.520094] RPC: 33550 __rpc_execute flags=0x1 >>>> [ 7680.520098] RPC: 33550 xprt_connect_status: retrying >>>> [ 7680.520103] RPC: 33550 call_connect_status (status -11) >>>> [ 7680.520108] RPC: 33550 call_transmit (status 0) >>>> [ 7680.520112] RPC: 33550 xprt_prepare_transmit >>>> [ 7680.520118] RPC: 33550 rpc_xdr_encode (status 0) >>>> [ 7680.520123] RPC: 33550 marshaling UNIX cred ffff88012e002300 >>>> [ 7680.520130] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data >>>> [ 7680.520136] RPC: 33550 xprt_transmit(32920) >>>> [ 7680.520145] RPC: xs_tcp_send_request(32920) = -32 >>>> [ 7680.520151] RPC: xs_tcp_state_change client ffff88013e62d800... >>>> [ 7680.520156] RPC: state 7 conn 0 dead 0 zapped 1 >>> I changed that debug to output sk_shutdown too. That has a value of 2 >>> (IE SEND_SHUTDOWN). Looking at tcp_sendmsg(), I see this: >>> err = -EPIPE; >>> if (sk->sk_err || (sk->sk_shutdown& SEND_SHUTDOWN)) >>> goto out_err; >>> which correlates with the trace "xs_tcp_send_request(32920) = -32". So, >>> this looks like a problem in the sockets/tcp layer. The rpc layer issues >>> a shutdown and then reconnects using the same socket. So either >>> sk_shutdown needs zeroing once the shutdown completes or should be >>> zeroed on subsequent connect. The latter sounds safer. >> This patch for 2.6.34.1 fixes the issue: >> >> --- /home/company/software/src/linux-2.6.34.1/net/ipv4/tcp_output.c 2010-07-27 08:46:46.917000000 +0100 >> +++ net/ipv4/tcp_output.c 2010-07-27 09:19:16.000000000 +0100 >> @@ -2522,6 +2522,13 @@ >> struct tcp_sock *tp = tcp_sk(sk); >> __u8 rcv_wscale; >> >> + /* clear down any previous shutdown attempts so that >> + * reconnects on a socket that's been shutdown leave the >> + * socket in a usable state (otherwise tcp_sendmsg() returns >> + * -EPIPE). >> + */ >> + sk->sk_shutdown = 0; >> + >> /* We'll fix this up when we get a response from the other end. >> * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. >> */ >> >> As I mentioned in my first message, we first saw this issue in 2.6.32 as supplied by debian (linux-image-2.6.32-5-amd64 Version: 2.6.32-17). It looks like the same patch would fix the problem there too. >> > CC netdev > > This reminds me a similar problem we had in the past, fixed with commit > 1fdf475a (tcp: tcp_disconnect() should clear window_clamp) > > But tcp_disconnect() already clears sk->sk_shutdown > > If NFS calls tcp_disconnect(), then shutdown(), there is a problem. > > Maybe xs_tcp_shutdown() should make some sanity tests ? > > Following sequence is legal, and your patch might break it. > > fd = socket(...); > shutdown(fd, SHUT_WR); > ... > connect(fd, ...); > > > Thanks for the response. From my reading of the RPC code, because nothing clears the sk_shutdown flag, the RPC code goes into a loop when recovering from packets being lost: shutdown connect send fails so repeat My patch stops the NFS client hang that I was seeing but I'm not an expert on either the socket layer, RPC code or NFS code so I'm happy for someone else to come up with the alternative, correct fix. -- Andy, BlueArc Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Chuck Lever on 27 Jul 2010 13:30 Add CC: linux-nfs(a)vger.kernel.org On 07/27/10 08:21 AM, Eric Dumazet wrote: > Le mardi 27 juillet 2010 à 11:53 +0100, Andy Chittenden a écrit : >>>>> IE the client starts a connection and then closes it again without sending data. >>>> Once this happens, here's some rpcdebug info for the rpc module using 2.6.34.1 kernel: >>>> >>>> ... lots of the following nfsv3 WRITE requests: >>>> [ 7670.026741] 57793 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026759] 57794 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026778] 57795 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026797] 57796 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026815] 57797 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026834] 57798 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026853] 57799 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026871] 57800 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026890] 57801 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026909] 57802 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7680.520042] RPC: worker connecting xprt ffff88013e62d800 via tcp to 10.1.6.102 (port 2049) >>>> [ 7680.520066] RPC: ffff88013e62d800 connect status 99 connected 0 sock state 7 >>>> [ 7680.520074] RPC: 33550 __rpc_wake_up_task (now 4296812426) >>>> [ 7680.520079] RPC: 33550 disabling timer >>>> [ 7680.520084] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" >>>> [ 7680.520089] RPC: __rpc_wake_up_task done >>>> [ 7680.520094] RPC: 33550 __rpc_execute flags=0x1 >>>> [ 7680.520098] RPC: 33550 xprt_connect_status: retrying >>>> [ 7680.520103] RPC: 33550 call_connect_status (status -11) >>>> [ 7680.520108] RPC: 33550 call_transmit (status 0) >>>> [ 7680.520112] RPC: 33550 xprt_prepare_transmit >>>> [ 7680.520118] RPC: 33550 rpc_xdr_encode (status 0) >>>> [ 7680.520123] RPC: 33550 marshaling UNIX cred ffff88012e002300 >>>> [ 7680.520130] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data >>>> [ 7680.520136] RPC: 33550 xprt_transmit(32920) >>>> [ 7680.520145] RPC: xs_tcp_send_request(32920) = -32 >>>> [ 7680.520151] RPC: xs_tcp_state_change client ffff88013e62d800... >>>> [ 7680.520156] RPC: state 7 conn 0 dead 0 zapped 1 >> >>> I changed that debug to output sk_shutdown too. That has a value of 2 >>> (IE SEND_SHUTDOWN). Looking at tcp_sendmsg(), I see this: >> >>> err = -EPIPE; >>> if (sk->sk_err || (sk->sk_shutdown& SEND_SHUTDOWN)) >>> goto out_err; >> >>> which correlates with the trace "xs_tcp_send_request(32920) = -32". So, >>> this looks like a problem in the sockets/tcp layer. The rpc layer issues >>> a shutdown and then reconnects using the same socket. So either >>> sk_shutdown needs zeroing once the shutdown completes or should be >>> zeroed on subsequent connect. The latter sounds safer. >> This patch for 2.6.34.1 fixes the issue: >> >> --- /home/company/software/src/linux-2.6.34.1/net/ipv4/tcp_output.c 2010-07-27 08:46:46.917000000 +0100 >> +++ net/ipv4/tcp_output.c 2010-07-27 09:19:16.000000000 +0100 >> @@ -2522,6 +2522,13 @@ >> struct tcp_sock *tp = tcp_sk(sk); >> __u8 rcv_wscale; >> >> + /* clear down any previous shutdown attempts so that >> + * reconnects on a socket that's been shutdown leave the >> + * socket in a usable state (otherwise tcp_sendmsg() returns >> + * -EPIPE). >> + */ >> + sk->sk_shutdown = 0; >> + >> /* We'll fix this up when we get a response from the other end. >> * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. >> */ >> >> As I mentioned in my first message, we first saw this issue in 2.6.32 as supplied by debian (linux-image-2.6.32-5-amd64 Version: 2.6.32-17). It looks like the same patch would fix the problem there too. >> > > CC netdev > > This reminds me a similar problem we had in the past, fixed with commit > 1fdf475a (tcp: tcp_disconnect() should clear window_clamp) > > But tcp_disconnect() already clears sk->sk_shutdown > > If NFS calls tcp_disconnect(), then shutdown(), there is a problem. If tcp_disconnect() was called at some point, I would expect to see a message from xs_error_report() in the debugging output. Perhaps tcp_disconnect() is not being invoked at all? > Maybe xs_tcp_shutdown() should make some sanity tests ? > > Following sequence is legal, and your patch might break it. > > fd = socket(...); > shutdown(fd, SHUT_WR); > ... > connect(fd, ...); I looked closely at some of Andy's debugging output from the linux-kernel mailing list archive. I basically agree that the network layer is returning -EPIPE from tcp_sendmsg(), which the RPC client logic does not expect. But it's not clear to me how it gets into this state. > [ 7728.520042] RPC: worker connecting xprt ffff88013e62d800 via tcp to 10.1.6.102 (port 2049) > [ 7728.520093] RPC: ffff88013e62d800 connect status 115 connected 0 sock state 2 "sock state 2" => sk->sk_state == TCP_SYN_SENT > [ 7728.520884] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.520889] RPC: state 1 conn 0 dead 0 zapped 1 "state 1" => sk->sk_state == TCP_ESTABLISHED RPC client wakes up this RPC task now that the connection is established. > [ 7728.520896] RPC: 33550 __rpc_wake_up_task (now 4296824426) > [ 7728.520900] RPC: 33550 disabling timer > [ 7728.520906] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" > [ 7728.520912] RPC: __rpc_wake_up_task done > [ 7728.520932] RPC: 33550 __rpc_execute flags=0x1 > [ 7728.520937] RPC: 33550 xprt_connect_status: retrying > [ 7728.520942] RPC: 33550 call_connect_status (status -11) The awoken RPC task's status is -EAGAIN, which prevents a reconnection attempt. > [ 7728.520947] RPC: 33550 call_transmit (status 0) > [ 7728.520951] RPC: 33550 xprt_prepare_transmit > [ 7728.520957] RPC: 33550 rpc_xdr_encode (status 0) > [ 7728.520962] RPC: 33550 marshaling UNIX cred ffff88012e002300 > [ 7728.520969] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data > [ 7728.520976] RPC: 33550 xprt_transmit(32920) RPC client encodes the request and attempts to send it. > [ 7728.520984] RPC: xs_tcp_send_request(32920) = -32 Network layer says -EPIPE, for some reason. RPC client calls kernel_sock_shutdown(SHUT_WR). > [ 7728.520997] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521007] RPC: state 4 conn 1 dead 0 zapped 1 "state 4" => sk->sk_state == TCP_FIN_WAIT1 The RPC client sets up a linger timeout. > [ 7728.521013] RPC: 33550 call_status (status -32) > [ 7728.521018] RPC: 33550 call_bind (status 0) > [ 7728.521023] RPC: 33550 call_connect xprt ffff88013e62d800 is not connected > [ 7728.521028] RPC: 33550 xprt_connect xprt ffff88013e62d800 is not connected > [ 7728.521035] RPC: 33550 sleep_on(queue "xprt_pending" time 4296824426) > [ 7728.521040] RPC: 33550 added to queue ffff88013e62db20 "xprt_pending" > [ 7728.521045] RPC: 33550 setting alarm for 60000 ms RPC client puts this RPC task to sleep. > [ 7728.521439] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521444] RPC: state 5 conn 0 dead 0 zapped 1 "state 5" => sk->sk_state == TCP_FIN_WAIT2 > [ 7728.521602] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521608] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521612] RPC: disconnected transport ffff88013e62d800 "state 7" => sk->sk_state == TCP_CLOSE The RPC client marks the socket closed. and the linger timeout is cancelled. At this point, sk_shutdown should be set to zero, correct? I don't see an xs_error_report() call here, which would confirm that the socket took a trip through tcp_disconnect(). > [ 7728.521617] RPC: 33550 __rpc_wake_up_task (now 4296824426) > [ 7728.521621] RPC: 33550 disabling timer > [ 7728.521626] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" > [ 7728.521631] RPC: __rpc_wake_up_task done RPC client wakes up the RPC task. Meanwhile... > [ 7728.521636] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521641] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521645] RPC: disconnected transport ffff88013e62d800 > [ 7728.521649] RPC: xs_tcp_data_ready... .... network layer calls closed socket's data_ready method... while the awoken RPC task gets underway. > [ 7728.521662] RPC: 33550 __rpc_execute flags=0x1 > [ 7728.521666] RPC: 33550 xprt_connect_status: retrying > [ 7728.521671] RPC: 33550 call_connect_status (status -11) The awoken RPC task's status is -EAGAIN, which prevents a reconnection attempt, even though there is no established connection. RPC client barrels on to send the request again. > [ 7728.521675] RPC: 33550 call_transmit (status 0) > [ 7728.521679] RPC: 33550 xprt_prepare_transmit > [ 7728.521683] RPC: 33550 rpc_xdr_encode (status 0) > [ 7728.521688] RPC: 33550 marshaling UNIX cred ffff88012e002300 > [ 7728.521694] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data > [ 7728.521699] RPC: 33550 xprt_transmit(32920) > [ 7728.521704] RPC: xs_tcp_send_request(32920) = -32 RPC client attempts to send again, gets -EPIPE, and calls kernel_sock_shutdown(SHUT_WR). If there is no connection established, the RPC client expects -ENOTCONN, in which case it will attempt to reconnect here. > [ 7728.521709] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521714] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521718] RPC: disconnected transport ffff88013e62d800 "state 7" => sk->sk_state == TCP_CLOSE Following this, the RPC client attempts to retransmit the request repeatedly, but the socket remains in the TCP_CLOSE state. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Andy Chittenden on 28 Jul 2010 03:10 > I don't see an xs_error_report() call here, which would confirm that the socket took a trip through tcp_disconnect(). From my reading of tcp_disconnect(), it calls sk->sk_error_report(sk) unconditionally so as there's no xs_error_report(), that surely means the exact opposite: tcp_disconnect() wasn't called. If it's not called, sk_shutdown is not cleared. And my revised tracing confirmed that it was set to SEND_SHUTDOWN. -- Andy, BlueArc Engineering -----Original Message----- From: Chuck Lever [mailto:chuck.lever(a)oracle.com] Sent: 27 July 2010 18:29 To: Eric Dumazet Cc: Andy Chittenden; Linux Kernel Mailing List (linux-kernel(a)vger.kernel.org); Trond Myklebust; netdev; Linux NFS Mailing List Subject: Re: nfs client hang Add CC: linux-nfs(a)vger.kernel.org On 07/27/10 08:21 AM, Eric Dumazet wrote: > Le mardi 27 juillet 2010 à 11:53 +0100, Andy Chittenden a écrit : >>>>> IE the client starts a connection and then closes it again without sending data. >>>> Once this happens, here's some rpcdebug info for the rpc module using 2.6.34.1 kernel: >>>> >>>> ... lots of the following nfsv3 WRITE requests: >>>> [ 7670.026741] 57793 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026759] 57794 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026778] 57795 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026797] 57796 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026815] 57797 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026834] 57798 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026853] 57799 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026871] 57800 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026890] 57801 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7670.026909] 57802 0001 -11 ffff88012e32b000 (null) 0 ffffffffa03beb10 nfsv3 WRITE a:call_reserveresult q:xprt_backlog >>>> [ 7680.520042] RPC: worker connecting xprt ffff88013e62d800 via tcp to 10.1.6.102 (port 2049) >>>> [ 7680.520066] RPC: ffff88013e62d800 connect status 99 connected 0 sock state 7 >>>> [ 7680.520074] RPC: 33550 __rpc_wake_up_task (now 4296812426) >>>> [ 7680.520079] RPC: 33550 disabling timer >>>> [ 7680.520084] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" >>>> [ 7680.520089] RPC: __rpc_wake_up_task done >>>> [ 7680.520094] RPC: 33550 __rpc_execute flags=0x1 >>>> [ 7680.520098] RPC: 33550 xprt_connect_status: retrying >>>> [ 7680.520103] RPC: 33550 call_connect_status (status -11) >>>> [ 7680.520108] RPC: 33550 call_transmit (status 0) >>>> [ 7680.520112] RPC: 33550 xprt_prepare_transmit >>>> [ 7680.520118] RPC: 33550 rpc_xdr_encode (status 0) >>>> [ 7680.520123] RPC: 33550 marshaling UNIX cred ffff88012e002300 >>>> [ 7680.520130] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data >>>> [ 7680.520136] RPC: 33550 xprt_transmit(32920) >>>> [ 7680.520145] RPC: xs_tcp_send_request(32920) = -32 >>>> [ 7680.520151] RPC: xs_tcp_state_change client ffff88013e62d800... >>>> [ 7680.520156] RPC: state 7 conn 0 dead 0 zapped 1 >> >>> I changed that debug to output sk_shutdown too. That has a value of 2 >>> (IE SEND_SHUTDOWN). Looking at tcp_sendmsg(), I see this: >> >>> err = -EPIPE; >>> if (sk->sk_err || (sk->sk_shutdown& SEND_SHUTDOWN)) >>> goto out_err; >> >>> which correlates with the trace "xs_tcp_send_request(32920) = -32". So, >>> this looks like a problem in the sockets/tcp layer. The rpc layer issues >>> a shutdown and then reconnects using the same socket. So either >>> sk_shutdown needs zeroing once the shutdown completes or should be >>> zeroed on subsequent connect. The latter sounds safer. >> This patch for 2.6.34.1 fixes the issue: >> >> --- /home/company/software/src/linux-2.6.34.1/net/ipv4/tcp_output.c 2010-07-27 08:46:46.917000000 +0100 >> +++ net/ipv4/tcp_output.c 2010-07-27 09:19:16.000000000 +0100 >> @@ -2522,6 +2522,13 @@ >> struct tcp_sock *tp = tcp_sk(sk); >> __u8 rcv_wscale; >> >> + /* clear down any previous shutdown attempts so that >> + * reconnects on a socket that's been shutdown leave the >> + * socket in a usable state (otherwise tcp_sendmsg() returns >> + * -EPIPE). >> + */ >> + sk->sk_shutdown = 0; >> + >> /* We'll fix this up when we get a response from the other end. >> * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. >> */ >> >> As I mentioned in my first message, we first saw this issue in 2.6.32 as supplied by debian (linux-image-2.6.32-5-amd64 Version: 2.6.32-17). It looks like the same patch would fix the problem there too. >> > > CC netdev > > This reminds me a similar problem we had in the past, fixed with commit > 1fdf475a (tcp: tcp_disconnect() should clear window_clamp) > > But tcp_disconnect() already clears sk->sk_shutdown > > If NFS calls tcp_disconnect(), then shutdown(), there is a problem. If tcp_disconnect() was called at some point, I would expect to see a message from xs_error_report() in the debugging output. Perhaps tcp_disconnect() is not being invoked at all? > Maybe xs_tcp_shutdown() should make some sanity tests ? > > Following sequence is legal, and your patch might break it. > > fd = socket(...); > shutdown(fd, SHUT_WR); > ... > connect(fd, ...); I looked closely at some of Andy's debugging output from the linux-kernel mailing list archive. I basically agree that the network layer is returning -EPIPE from tcp_sendmsg(), which the RPC client logic does not expect. But it's not clear to me how it gets into this state. > [ 7728.520042] RPC: worker connecting xprt ffff88013e62d800 via tcp to 10.1.6.102 (port 2049) > [ 7728.520093] RPC: ffff88013e62d800 connect status 115 connected 0 sock state 2 "sock state 2" => sk->sk_state == TCP_SYN_SENT > [ 7728.520884] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.520889] RPC: state 1 conn 0 dead 0 zapped 1 "state 1" => sk->sk_state == TCP_ESTABLISHED RPC client wakes up this RPC task now that the connection is established. > [ 7728.520896] RPC: 33550 __rpc_wake_up_task (now 4296824426) > [ 7728.520900] RPC: 33550 disabling timer > [ 7728.520906] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" > [ 7728.520912] RPC: __rpc_wake_up_task done > [ 7728.520932] RPC: 33550 __rpc_execute flags=0x1 > [ 7728.520937] RPC: 33550 xprt_connect_status: retrying > [ 7728.520942] RPC: 33550 call_connect_status (status -11) The awoken RPC task's status is -EAGAIN, which prevents a reconnection attempt. > [ 7728.520947] RPC: 33550 call_transmit (status 0) > [ 7728.520951] RPC: 33550 xprt_prepare_transmit > [ 7728.520957] RPC: 33550 rpc_xdr_encode (status 0) > [ 7728.520962] RPC: 33550 marshaling UNIX cred ffff88012e002300 > [ 7728.520969] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data > [ 7728.520976] RPC: 33550 xprt_transmit(32920) RPC client encodes the request and attempts to send it. > [ 7728.520984] RPC: xs_tcp_send_request(32920) = -32 Network layer says -EPIPE, for some reason. RPC client calls kernel_sock_shutdown(SHUT_WR). > [ 7728.520997] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521007] RPC: state 4 conn 1 dead 0 zapped 1 "state 4" => sk->sk_state == TCP_FIN_WAIT1 The RPC client sets up a linger timeout. > [ 7728.521013] RPC: 33550 call_status (status -32) > [ 7728.521018] RPC: 33550 call_bind (status 0) > [ 7728.521023] RPC: 33550 call_connect xprt ffff88013e62d800 is not connected > [ 7728.521028] RPC: 33550 xprt_connect xprt ffff88013e62d800 is not connected > [ 7728.521035] RPC: 33550 sleep_on(queue "xprt_pending" time 4296824426) > [ 7728.521040] RPC: 33550 added to queue ffff88013e62db20 "xprt_pending" > [ 7728.521045] RPC: 33550 setting alarm for 60000 ms RPC client puts this RPC task to sleep. > [ 7728.521439] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521444] RPC: state 5 conn 0 dead 0 zapped 1 "state 5" => sk->sk_state == TCP_FIN_WAIT2 > [ 7728.521602] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521608] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521612] RPC: disconnected transport ffff88013e62d800 "state 7" => sk->sk_state == TCP_CLOSE The RPC client marks the socket closed. and the linger timeout is cancelled. At this point, sk_shutdown should be set to zero, correct? I don't see an xs_error_report() call here, which would confirm that the socket took a trip through tcp_disconnect(). > [ 7728.521617] RPC: 33550 __rpc_wake_up_task (now 4296824426) > [ 7728.521621] RPC: 33550 disabling timer > [ 7728.521626] RPC: 33550 removed from queue ffff88013e62db20 "xprt_pending" > [ 7728.521631] RPC: __rpc_wake_up_task done RPC client wakes up the RPC task. Meanwhile... > [ 7728.521636] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521641] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521645] RPC: disconnected transport ffff88013e62d800 > [ 7728.521649] RPC: xs_tcp_data_ready... ... network layer calls closed socket's data_ready method... while the awoken RPC task gets underway. > [ 7728.521662] RPC: 33550 __rpc_execute flags=0x1 > [ 7728.521666] RPC: 33550 xprt_connect_status: retrying > [ 7728.521671] RPC: 33550 call_connect_status (status -11) The awoken RPC task's status is -EAGAIN, which prevents a reconnection attempt, even though there is no established connection. RPC client barrels on to send the request again. > [ 7728.521675] RPC: 33550 call_transmit (status 0) > [ 7728.521679] RPC: 33550 xprt_prepare_transmit > [ 7728.521683] RPC: 33550 rpc_xdr_encode (status 0) > [ 7728.521688] RPC: 33550 marshaling UNIX cred ffff88012e002300 > [ 7728.521694] RPC: 33550 using AUTH_UNIX cred ffff88012e002300 to wrap rpc data > [ 7728.521699] RPC: 33550 xprt_transmit(32920) > [ 7728.521704] RPC: xs_tcp_send_request(32920) = -32 RPC client attempts to send again, gets -EPIPE, and calls kernel_sock_shutdown(SHUT_WR). If there is no connection established, the RPC client expects -ENOTCONN, in which case it will attempt to reconnect here. > [ 7728.521709] RPC: xs_tcp_state_change client ffff88013e62d800... > [ 7728.521714] RPC: state 7 conn 0 dead 0 zapped 1 > [ 7728.521718] RPC: disconnected transport ffff88013e62d800 "state 7" => sk->sk_state == TCP_CLOSE Following this, the RPC client attempts to retransmit the request repeatedly, but the socket remains in the TCP_CLOSE state.
From: Andy Chittenden on 28 Jul 2010 03:30 resending as it seems to have been corrupted on LKML! > The RPC client marks the socket closed. and the linger timeout is > cancelled. At this point, sk_shutdown should be set to zero, correct? > I don't see an xs_error_report() call here, which would confirm that the > socket took a trip through tcp_disconnect(). From my reading of tcp_disconnect(), it calls sk->sk_error_report(sk) unconditionally so as there's no xs_error_report(), that surely means the exact opposite: tcp_disconnect() wasn't called. If it's not called, sk_shutdown is not cleared. And my revised tracing confirmed that it was set to SEND_SHUTDOWN. -- Andy, BlueArc Engineering
From: Chuck Lever on 28 Jul 2010 13:40
On 07/28/10 03:24 AM, Andy Chittenden wrote: > resending as it seems to have been corrupted on LKML! > >> The RPC client marks the socket closed. and the linger timeout is >> cancelled. At this point, sk_shutdown should be set to zero, correct? >> I don't see an xs_error_report() call here, which would confirm that the >> socket took a trip through tcp_disconnect(). > > From my reading of tcp_disconnect(), it calls sk->sk_error_report(sk) > unconditionally so as there's no xs_error_report(), that surely means > the exact opposite: tcp_disconnect() wasn't called. If it's not > called, sk_shutdown is not cleared. And my revised tracing confirmed > that it was set to SEND_SHUTDOWN. Sorry, that's what I meant above. An xs_error_report() debugging message at that point in the log would confirm that the socket took a trip through tcp_disconnect(). But I don't see such a message. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |