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?
Trond--
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