Return-Path: linux-nfs-owner@vger.kernel.org Received: from userp1040.oracle.com ([156.151.31.81]:33875 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752550Ab3KOWba convert rfc822-to-8bit (ORCPT ); Fri, 15 Nov 2013 17:31:30 -0500 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) Subject: Re: NFS over RDMA stops working for data larger than 812 Bytes From: Chuck Lever In-Reply-To: <4673A7C9-3424-48F4-B64C-976EFE16017C@netapp.com> Date: Fri, 15 Nov 2013 17:31:22 -0500 Cc: Klemens Senn , Linux NFS Mailing List Message-Id: References: <24663A6D-A54A-441B-880E-BB7FD6BBB3F2@oracle.com> <4673A7C9-3424-48F4-B64C-976EFE16017C@netapp.com> To: "Myklebust, Trond" Sender: linux-nfs-owner@vger.kernel.org List-ID: 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(). -- Chuck Lever chuck[dot]lever[at]oracle[dot]com