Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx11.netapp.com ([216.240.18.76]:64186 "EHLO mx11.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752844Ab3KOWxm convert rfc822-to-8bit (ORCPT ); Fri, 15 Nov 2013 17:53:42 -0500 From: "Myklebust, Trond" To: Charles Edward Lever CC: Klemens Senn , Linux NFS Mailing List Subject: Re: NFS over RDMA stops working for data larger than 812 Bytes Date: Fri, 15 Nov 2013 22:53:38 +0000 Message-ID: References: <24663A6D-A54A-441B-880E-BB7FD6BBB3F2@oracle.com> <4673A7C9-3424-48F4-B64C-976EFE16017C@netapp.com> In-Reply-To: Content-Type: text/plain; charset="Windows-1252" MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Nov 15, 2013, at 17:31, Chuck Lever wrote: > > On Nov 15, 2013, at 5:29 PM, "Myklebust, Trond" wrote: > >> >> On Nov 15, 2013, at 16:39, Chuck Lever wrote: >> >>> Hi Trond- >>> >>> Klemens Senn says: >>>> Hi, >>>> >>>> I started setting up NFS over RDMA on a OpenSUSE 12.3 machine using the >>>> 3.7.10-1.16-default kernel. >>>> Mounting the NFS share works and getting a file with 812 Bytes succeeds. >>>> Reading 813 Bytes raises a Input/output error. >>>> >>>> The export on the server side is done with >>>> /data >>>> 172.16.100.0/24(rw,wdelay,crossmnt,insecure,no_root_squash,no_subtree_check,fsid=0,mountpoint) >>>> >>>> Following command is used for mounting the NFSv4 share: >>>> mount -t nfs -o port=20049,rdma,vers=4.0,timeo=900 172.16.100.2:/ /mnt/ >>>> >>>> Testing the client side with older kernels stated that the mount is >>>> working properly with the 3.4.67 kernel. I continued testing with the >>>> 3.10.17 kernel and enabled the debug level and noticed the message >>>> "server cheating in read reply: count 813 > recvd 0" >>>> >>>> Here is the syslog output: >>>> NFS: read(//813_bytes, 262144@0) >>>> NFS: nfs_readpage (ffffea001db1e898 4096@0) >>>> NFS: 0 initiated read call (req 0:33/70, 813 bytes @ offset 0) >>>> RPC: new task initialized, procpid 9881 >>>> RPC: allocated task ffff88105dacabf8 >>>> RPC: 1631 __rpc_execute flags=0x1 >>>> <-- nfs4_setup_sequence status=0 >>>> RPC: 1631 call_start nfs4 proc READ (async) >>>> RPC: 1631 call_reserve (status 0) >>>> RPC: 1631 reserved req ffff88085e641c00 xid 3f6a89a6 >>>> RPC: 1631 call_reserveresult (status 0) >>>> RPC: 1631 call_refresh (status 0) >>>> RPC: 1631 refreshing UNIX cred ffff88087c2108c0 >>>> RPC: 1631 call_refreshresult (status 0) >>>> RPC: 1631 call_allocate (status 0) >>>> RPC: xprt_rdma_allocate: size 684, request 0xffff88084a342000 >>>> RPC: 1631 call_bind (status 0) >>>> RPC: 1631 call_connect xprt ffff88085f297000 is connected >>>> RPC: 1631 call_transmit (status 0) >>>> RPC: 1631 xprt_prepare_transmit >>>> RPC: 1631 xprt_cwnd_limited cong = 0 cwnd = 4096 >>>> RPC: 1631 rpc_xdr_encode (status 0) >>>> RPC: 1631 marshaling UNIX cred ffff88087c2108c0 >>>> RPC: 1631 using AUTH_UNIX cred ffff88087c2108c0 to wrap rpc data >>>> RPC: 1631 xprt_transmit(144) >>>> RPC: rpcrdma_inline_pullup: pad 0 destp 0xffff88084a3437f0 len 144 >>>> hdrlen 144 >>>> RPC: rpcrdma_register_frmr_external: Using frmr ffff88084b612d10 >>>> to map 1 segments >>>> RPC: rpcrdma_create_chunks: write chunk elem >>>> 813@0x87bf95000:0x8a905 (more) >>>> RPC: rpcrdma_register_frmr_external: Using frmr ffff88084b612d38 >>>> to map 1 segments >>>> RPC: rpcrdma_create_chunks: write chunk elem >>>> 152@0x84a343974:0x8aa01 (last) >>>> RPC: rpcrdma_marshal_req: write chunk: hdrlen 68 rpclen 144 padlen >>>> 0 headerp 0xffff88084a343100 base 0xffff88084a343760 lkey 0x8000 >>>> RPC: rpcrdma_event_process: event rep ffff88084b612d10 status 0 >>>> opcode 8 length 4294936584 >>>> RPC: rpcrdma_event_process: event rep ffff88084b612d38 status 0 >>>> opcode 8 length 4294936584 >>>> RPC: 1631 xmit complete >>>> RPC: 1631 sleep_on(queue "xprt_pending" time 4296115067) >>>> RPC: 1631 added to queue ffff88085f297258 "xprt_pending" >>>> RPC: 1631 setting alarm for 90000 ms >>>> RPC: wake_up_first(ffff88085f297190 "xprt_sending") >>>> RPC: rpcrdma_event_process: event rep ffff88085e8bf000 status 0 >>>> opcode 80 length 128 >>>> RPC: rpcrdma_reply_handler: reply 0xffff88085e8bf000 completes >>>> request 0xffff88084a342000 >>>> RPC request 0xffff88085e641c00 xid 0xa6896a3f >>>> RPC: rpcrdma_count_chunks: chunk 813@0x87bf95000:0x8a905 >>>> RPC: rpcrdma_count_chunks: chunk 3@0x84a343974:0x8aa01 >>>> RPC: rpcrdma_inline_fixup: srcp 0xffff88085e8bf0a4 len 60 hdrlen 60 >>>> RPC: rpcrdma_reply_handler: xprt_complete_rqst(0xffff88085f297000, >>>> 0xffff88085e641c00, 876) >>>> RPC: 1631 xid 3f6a89a6 complete (876 bytes received) >>>> RPC: 1631 __rpc_wake_up_task (now 4296115067) >>>> RPC: 1631 disabling timer >>>> RPC: 1631 removed from queue ffff88085f297258 "xprt_pending" >>>> RPC: __rpc_wake_up_task done >>>> RPC: 1631 __rpc_execute flags=0x801 >>>> RPC: 1631 call_status (status 876) >>>> RPC: 1631 call_decode (status 876) >>>> RPC: 1631 validating UNIX cred ffff88087c2108c0 >>>> RPC: 1631 using AUTH_UNIX cred ffff88087c2108c0 to unwrap rpc data >>>> NFS: server cheating in read reply: count 813 > recvd 0 >>>> RPC: 1631 call_decode result 0 >>>> NFS: nfs_readpage_result: 1631, (status 0) >>>> --> nfs4_read_done >>>> >>>> Adding other debug prints to the kernel module told me that >>>> buf->page_len is set to 0 in xdr_align_pages (in file net/sunrpc/xdr.c). >>>> Comparing this piece of code with older kernel versions showed that the >>>> comparison with buf->page_len was introduces in kernel 3.7. >>>> By disabling this check the file transfer seems to work. >>>> >>>> Here is the patch for kernel 3.10.17: >>>> >>>> --- net/sunrpc/xdr.c 2013-10-18 19:44:19.000000000 +0200 >>>> +++ net/sunrpc/xdr_new.c 2013-11-08 14:06:00.241217773 +0100 >>>> @@ -747,7 +747,7 @@ >>>> nwords = xdr->nwords; >>>> len = nwords << 2; >>>> } >>>> - if (buf->page_len <= len) >>>> + if (buf->page_len && buf->page_len <= len) >>>> len = buf->page_len; >>>> else if (nwords < xdr->nwords) { >>>> /* Truncate page data and move it into the tail */ >>>> >>>> >>>> Can you please tell me which entity sets (or does not set) the total >>>> length (buf->page_len) after receiving the data from the RDMA_SEND >>>> operation from the server? >>>> >>>> Please advise >>>> >>>> Klemens >>> >>> Comparing xdr_align_pages() before commit a11a2bf4 and afterwords, it appears that it no longer handles cases where buf->page_len == 0 the same way it used to. xdr_align_pages() would never return zero unless xdr->nwords was zero. >> >> Why would the buf->page_len == 0 in a READ call? Has RDMA been relying on some kind of undocumented behaviour? > > See rpcrdma_inline_fixup(). I see it, but I don?t get it. What is it trying to do? Firstly, why is it playing with rqst->rq_rcv_buf instead of using rq_private_buf? Secondly, why is it mucking with the page buffer length?