[OpenAFS-devel] Cache inconsistency in client 1.4.8 and above

[Felix Frank]

  This message is in MIME format.  The first part should be readable text,
  while the remaining parts are likely unreadable without MIME-aware tools.

--579669762-50219747-1240311866=:15575
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed

>> Cache consistency with mmap'ed writes can apparently only be achieved when
>> no afs_linux_writepage_sync's are aborted at all.
>>
>> I think I still haven't truly understood the exact idea of the antirecursion
>> patch. To me, it seems to omit writing some precious data.
>
> We had a backtrace which showed we were calling back into ourselves.
> The sole goal was to prevent that. Anything beyond was incidental and
> uneeded.

There is yet another fix proposal in RT #124627. It works for me at least.
Evidently, after applying fixes, deadlocks could still occur during the
first invocation of osi_VM_StoreAllSegments, so 
linux-mmap-antirecursion-20081020 never really worked, I'm afraid.
This current fix hopefully will.

One thing had me puzzled for a while - the mmap_test program (attached) 
works fine on a 2.6.18-128.1.6.el5 kernel, but reliably produces corrupt
chunks in a virtual machine with the 2.6.18-128.1.6.el5xen kernel,
both using 100MB disk caches. This holds true for both vanilla 1.4.10 and
various fixes I've been trying the last days.

Can anyone reproduce?

Cheers
  - Felix
--579669762-50219747-1240311866=:15575
Content-Type: TEXT/PLAIN; charset=US-ASCII; name=mmap_test.c
Content-Transfer-Encoding: BASE64
Content-Description: 
Content-Disposition: attachment; filename=mmap_test.c
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--579669762-50219747-1240311866=:15575--