On Nov 15, 2013, at 5:29 PM, "Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote:
>
> On Nov 15, 2013, at 16:39, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
>> Hi Trond-
>>
>> Klemens Senn <klemens.senn@xxxxxxxxx> 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
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