Re: nfs-bug when server for 9-Stable becomes client as well ?

Vincent Hoffman <vince@unsane.co.uk> writes:

> On 06/07/2012 14:19, Arno J. Klaassen wrote:
>> Hello,
>>
>> looks like I discouvered a probable bug in the nfs-code, very
>> easy to reproduce in my setup :
>>
>>
>>    Machine-1 : Today's 9-stable, exporting /files (ufs) and /z2 (zfs)
>>
>>    Machine-2 : 8-stable as of April the 10th exporting /raid1
>>
>> On Machine-1 I mount /raid1 (rw,nfsv3,intr,tcp,rsize=32768,wsize=32768)
>> and start a script on this mount looping something like :
>>
>>   dd if=/dev/random of=BIG bs=1048576 count=${SIZE}
>>   cp -fp BIG BIG2
>>   cmp -x BIG BIG2
>>
>> I let this run for 24 hours (from time to time stressing Machine-1 with
>> other scripts, including provoking heavy swapping), no problem at all.
>>
>> However, then I mount /z2 (rw,nfsv3,intr,tcp,rsize=32768,wsize=32768)
>> on Machine-2, and *immediately* the above loop on Machine-1 fails :
>>
>>   Copying file ...cp: BIG: Permission denied
>>
>> No console messages this time, last time I got 
>>
>>   kernel: nfs_getpages: error 13
>>   kernel: vm_fault: pager read error, pid 87803 (cmp)
>>
>> on Machine-1.
>>
>> I repeated this scenario by replacing Machine-2 with a good old
>> 6-4-stable one, same outcome.
>>
>> Please tell me what I could do to nail this down a bit more.
> Its possible (although not definite) that you have hit the a mountd bug
> as documented in PRs
>
> kern/131342
> kern/136865

especially kern/131342 looks similar and quite old; funny I never hit
this before, I basically do the same tests since 'ages' on each new box.
Could be that faster network/cpu unreveals some race condition; I notice
as well that this server is the first (IIRC) who uses 3 different IRQs
for network interrupts (em(4) Intel(R) PRO/1000).

> I've recently asked on -CURRENT about this and had a patch to try from
> Rick, I'm testing it now but it doesnt seem to fix it for me, just
> improve it alothough I'm trying to get enough runs to be a valid sample.
> (see
> http://docs.freebsd.org/cgi/getmsg.cgi?fetch=377627+0+archive/2012/freebsd-current/20120701.freebsd-current
> )
>
> What I did for my production nas was edit mount.c so it didnt send a
> SIGHUP to mountd as suggested by rick, as it was easy to do and non
> intrusive.

hmm, this means I should patch each fbsd-client, no? May be easier to
patch mountd to ignore SIHGUP and use some non-standard signal to force
re-init?

Arno

> Vince
>
>>
>> Thanx in advance,
>>
>> Best, Arno
>>
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>
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