[illumos-Developer] MUCH better --> zil for zvol TRUNCATE (and iSCSI UNMAP) working...

[George Wilson]

On 3/1/11 9:31 AM, Dan McDonald wrote:
> George gave me a few things to try (which I've numbered and quoted):
>
>> 1.) So I would recommend setting a breakpoint after zvol_log_truncate() and
>>      forcing a panic.  Then make sure that we process this ioctl again on
>>      bootup.
> We talked about this already, and forcing the reboot after zil_commit()
> causes the right thing to happen.
>
>> 2.) Also do the same thing after dmu_free_long_range().
> See above.
>
>> 3.) But you'll want to add another reboot point in zvol_replay_truncate()
>>      prior to calling dmu_free_long_range() and also after it. What we need
>>      to see is that zvol_replay_truncate() is called after these reboot
>>      points. If they are then we're still replaying the same log block on
>>      disk and we can leave the code the same. Make sense?
> Every time I rebooted in the *middle* of zvol_replay_truncate(), the
> rebooting system (once COMSTAR starts and attmempts to open the zvol) would
> drop into zvol_replay_truncate() again, no matter where I rebooted within the
> function (including JUST before an otherwise successful return).
>
> I think we're doing the right thing w.r.t. the zvol.  As I mentioned before,
> my client UNMAPs in chunks of 8MB where possible, so for sufficiently large
> files (like my original 128MB test tarball) I've only be able to catch the
> first 8MB chunk.
>
> So with that, I submit that this webrev:
>
> 	http://www.kebe.com/~danmcd/webrevs/unmap/
>
> might be fit for consumption by Illumos.  I still defer to reviewers with
> more ZFS clue than me, but this has been a good learning experience.

Great news! If you could make one more change and try the test again:

In zvol_replay_truncate() I don't think we need any of the dmu_tx_* 
stuff. I believe that this can be simplified to just call 
dmu_free_long_range().

- George
> Thanks!
> Dan
>
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