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Subject: Re: [PATCH 0/1] NFSv4.2: Fix NFS4ERR_STALE with inter server copy
To:     Bruce Fields <bfields@fieldses.org>
Cc:     linux-nfs@vger.kernel.org
References: <20200923230606.63904-1-dai.ngo@oracle.com>
 <e7e738c6-f6e7-0d04-07fa-8017da469b8a@oracle.com>
 <20201001205119.GI1496@fieldses.org>
From:   Dai Ngo <dai.ngo@oracle.com>
Message-ID: <9a60ba5b-aefe-d75b-683a-fa0f4db6ae24@oracle.com>
Date:   Thu, 1 Oct 2020 14:48:07 -0700
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Thanks Bruce for your comments,

On 10/1/20 1:51 PM, Bruce Fields wrote:
> On Tue, Sep 29, 2020 at 08:18:54PM -0700, Dai Ngo wrote:
>> Have you had chance to review this patch and if it's ok would it be
>> possible to include it in the 5.10 pull?
> I don't think the op table approach would be that difficult, I'd really
> rather see that.

I think if we do the op table approach then we should also try to solve
all other dependencies between various NFS client and server modules
and not just the SSC part. It might be a little involved so I'd like
to take some time to research before committing to the longer solution
which I plan to do. In the mean time, this small patch allows some of
us to use the inter server copy until the long term solution is available.

> Is this causing someone an immediate practical problem?

This causes inter server copy to fail with any kernel build with NFS_FS=m
which I think is a common config. And it also causes compile errors if
NFSD=y, NFS_FS=y and NFS_v4=m.

-Dai

>
> --b.
>
>> Thanks,
>>
>> -Dai
>>
>> On 9/23/20 4:06 PM, Dai Ngo wrote:
>>> This patch provides a temporarily relief for inter copy to work with
>>> some common configs.  For long term solution, I think Trond's suggestion
>>> of using fs/nfs/nfs_common to store an op table that server can use to
>>> access the client code is the way to go.
>>>
>>>   fs/nfsd/Kconfig | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>>
>>> Below are the results of my testing of upstream mainline without and with the fix.
>>>
>>> Upstream version used for testing:  5.9-rc5
>>>
>>> 1. Upstream mainline (existing code: NFS_FS=y)
>>>
>>>
>>> |----------------------------------------------------------------------------------------|
>>> |  NFSD  |  NFS_FS  |  NFS_V4  |               RESULTS                                   |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    y     |    m     | Build errors: nfs42_ssc_open/close                      |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    m     |    m     | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |        |          |          | See NOTE1.                                              |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    m     |   y (m)  | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |        |          |          | See NOTE2.                                              |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    y     |    y     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>>
>>>
>>> |----------------------------------------------------------------------------------------|
>>> |  NFSD  |  NFS_FS  |  NFS_V4  |               RESULTS                                   |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    y     |    m     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    m     |    m     | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    m     |   y (m)  | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    y     |    y     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>>
>>> 2. Upstream mainline (with the fix:  !(NFSD=y && (NFS_FS=m || NFS_V4=m))
>>>
>>>
>>> |----------------------------------------------------------------------------------------|
>>> |  NFSD  |  NFS_FS  |  NFS_V4  |               RESULTS                                   |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    y     |    m     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    m     |    m     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    m     |   y (m)  | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>> |   m    |    y     |    y     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>>
>>>
>>> |----------------------------------------------------------------------------------------|
>>> |  NFSD  |  NFS_FS  |  NFS_V4  |               RESULTS                                   |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    y     |    m     | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    m     |    m     | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    m     |   y (m)  | Build OK, inter server copy failed with NFS4ERR_STALE   |
>>> |----------------------------------------------------------------------------------------|
>>> |   y    |    y     |    y     | Build OK, inter server copy OK                          |
>>> |----------------------------------------------------------------------------------------|
>>>
>>> NOTE1:
>>> BUG:  When inter server copy fails with NFS4ERR_STALE, it left the file
>>> created with size of 0!
>>>
>>> NOTE2:
>>> When NFS_V4=y and NFS_FS=m, the build process automatically builds with NFS_V4=m
>>> and ignores the setting NFS_V4=y in the config file.
>>>
>>> This probably due to NFS_V4 in fs/nfs/Kconfig is configured to depend on NFS_FS.
>>>