Re: [RFC PATCH 1/2] NFSD: fix misaligned DIO READ to not use a start_extra_page, exposes rpcrdma bug?

[Chuck Lever <chuck.lever@oracle.com>]

On 9/2/25 11:56 AM, Chuck Lever wrote:
> On 8/30/25 1:38 PM, Mike Snitzer wrote:

>> dt (j:1 t:1): File System Information:
>> dt (j:1 t:1):            Mounted from device: 192.168.0.105:/hs_test
>> dt (j:1 t:1):           Mounted on directory: /mnt/hs_test
>> dt (j:1 t:1):                Filesystem type: nfs4
>> dt (j:1 t:1):             Filesystem options: rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,fatal_neterrors=none,proto=tcp,nconnect=16,port=20491,timeo=600,retrans=2,sec=sys,clientaddr=192.168.0.106,local_lock=none,addr=192.168.0.105
> 
> I haven't been able to reproduce a similar failure in my lab with
> NFSv4.2 over RDMA with FDR InfiniBand. I've run dt 6-7 times, all
> successful. Also, for shit giggles, I tried the fsx-based subtests in
> fstests, no new failures there either. The export is xfs on an NVMe
> add-on card; server uses direct I/O for READ and page cache for WRITE.
> 
> Notice the mount options for your test run: "proto=tcp" and
> "nconnect=16". Even if your network fabric is RoCE, "proto=tcp" will
> not use RDMA at all; it will use bog standard TCP/IP on your ultra
> fast Ethernet network.
> 
> What should I try next? I can apply 2/2 or add "nconnect" or move the
> testing to my RoCE fabric after lunch and keep poking at it.
> 
> Or, I could switch to TCP. Suggestions welcome.

The client is not sending any READ procedures/operations to the server.
The following is NFSv3 for clarity, but NFSv4.x results are similar:

            nfsd-1669  [003]  1466.634816: svc_process:
addr=192.168.2.67 xid=0x7b2a6274 service=nfsd vers=3 proc=NULL
            nfsd-1669  [003]  1466.635389: svc_process:
addr=192.168.2.67 xid=0x7d2a6274 service=nfsd vers=3 proc=FSINFO
            nfsd-1669  [003]  1466.635420: svc_process:
addr=192.168.2.67 xid=0x7e2a6274 service=nfsd vers=3 proc=PATHCONF
            nfsd-1669  [003]  1466.635451: svc_process:
addr=192.168.2.67 xid=0x7f2a6274 service=nfsd vers=3 proc=GETATTR
            nfsd-1669  [003]  1466.635486: svc_process:
addr=192.168.2.67 xid=0x802a6274 service=nfsacl vers=3 proc=NULL
            nfsd-1669  [003]  1466.635558: svc_process:
addr=192.168.2.67 xid=0x812a6274 service=nfsd vers=3 proc=FSINFO
            nfsd-1669  [003]  1466.635585: svc_process:
addr=192.168.2.67 xid=0x822a6274 service=nfsd vers=3 proc=GETATTR
            nfsd-1669  [003]  1470.029208: svc_process:
addr=192.168.2.67 xid=0x832a6274 service=nfsd vers=3 proc=ACCESS
            nfsd-1669  [003]  1470.029255: svc_process:
addr=192.168.2.67 xid=0x842a6274 service=nfsd vers=3 proc=LOOKUP
            nfsd-1669  [003]  1470.029296: svc_process:
addr=192.168.2.67 xid=0x852a6274 service=nfsd vers=3 proc=FSSTAT
            nfsd-1669  [003]  1470.039715: svc_process:
addr=192.168.2.67 xid=0x862a6274 service=nfsacl vers=3 proc=GETACL
            nfsd-1669  [003]  1470.039758: svc_process:
addr=192.168.2.67 xid=0x872a6274 service=nfsd vers=3 proc=CREATE
            nfsd-1669  [003]  1470.040091: svc_process:
addr=192.168.2.67 xid=0x882a6274 service=nfsd vers=3 proc=WRITE
            nfsd-1669  [003]  1470.040469: svc_process:
addr=192.168.2.67 xid=0x892a6274 service=nfsd vers=3 proc=GETATTR
            nfsd-1669  [003]  1470.040503: svc_process:
addr=192.168.2.67 xid=0x8a2a6274 service=nfsd vers=3 proc=ACCESS
            nfsd-1669  [003]  1470.041867: svc_process:
addr=192.168.2.67 xid=0x8b2a6274 service=nfsd vers=3 proc=FSSTAT
            nfsd-1669  [003]  1470.042109: svc_process:
addr=192.168.2.67 xid=0x8c2a6274 service=nfsd vers=3 proc=REMOVE

So I'm probably missing some setting on the reproducer/client.

/mnt from klimt.ib.1015granger.net:/export/fast
 Flags:	rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,
  fatal_neterrors=none,proto=rdma,port=20049,timeo=600,retrans=2,
  sec=sys,mountaddr=192.168.2.55,mountvers=3,mountproto=tcp,
  local_lock=none,addr=192.168.2.55

Linux morisot.1015granger.net 6.15.10-100.fc41.x86_64 #1 SMP
 PREEMPT_DYNAMIC Fri Aug 15 14:55:12 UTC 2025 x86_64 GNU/Linux


-- 
Chuck Lever