[nfs][client] - Question about handling of the NFS3_EEXIST error in SYMLINK rpc

[alex.burlyga.ietf alex.burlyga.ietf]

Rick,

Thank you for a quick turn around, see answers inline:

On Sun, Jun 21, 2015 at 7:30 AM, Rick Macklem <rmacklem at uoguelph.ca> wrote:
> Alex Burlyga wrote:
>> Hi,
>>
>> NFS client code in nfsrpc_symlink() masks server returned NFS3_EEXIST
>> error
>> code
>> by returning 0 to the upper layers. I'm assuming this was an attempt
>> to
>> work around
>> some server's broken replay cache out there, however, it breaks a
>> more
>> common
>> case where server is returning EEXIST for legitimate reason and
>> application
>> is expecting this error code and equipped to deal with it.
>>
>> To fix it I see three ways of doing this:
>>  * Remove offending code
>>  * Make it optional, sysctl?
>>  * On NFS3_EEXIST send READLINK rpc to make sure symlink content is
>>  right
>>
>> Which of the ways will maximize the chances of getting this fix
>> upstream?
>>
> I've attached a patch for testing/review that does essentially #2.
> It has no effect on trivial tests, since the syscall does a Lookup
> before trying to create the symlink and fails with EEXIST.
> Do you have a case where competing clients are trying to create
> the symlink or something like that, which runs into this?

That's exactly failing test case we are running into.
>
> Please test the attached patch, since I don't know how to do that, rick
Great! I'll test it. I was leaning towards option 3 for SYMLINK and
option 2 for MKDIR.
This will work. Thanks for taking your time to generate the patch!

>
>> One more point, old client circa FreeBSD 7.0 does not exhibit this
>> problem.
>>
>> Alex
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