Re: [PATCH 0/2] blk-throttle: Couple of cleanup and fixes for limit update code

[Jens Axboe]

On 2011-03-07 21:29, Vivek Goyal wrote:
> On Mon, Mar 07, 2011 at 09:13:45PM +0100, Jens Axboe wrote:
>> On 2011-03-07 16:50, Vivek Goyal wrote:
>>> On Mon, Feb 21, 2011 at 06:42:48PM -0500, Vivek Goyal wrote:
>>>> Hi Jens,
>>>>
>>>> Couple of throttle fixes seem to have fallen through cracks.
>>>>
>>>> https://lkml.org/lkml/2010/12/15/331
>>>>
>>>> I am reposting it for inclusion. Please let me know if you have any concerns.
>>>> Oleg and Paul acked the patch in the past so I am retaining their Reviewed-by:
>>>> lines.
>>>>
>>>
>>> Hi Jens,
>>>
>>> Can you please apply following patches for 2.6.39. These are good for fixing
>>> couple of race conditions in block throttle code w.r.t limit updates.
>>> Please let me know if you have concernes with these patches.
>>
>> I have applied them now. 2/2 is a nice cleanup. But it does not apply
>> cleanly after the workqueue change we merged last week. I fixed it up
>> for you, manually applied hunk #5 and added the below diff. Please
>> inspect the end result. You should have rebased that patch.
> 
> Sorry, this patch was posted before workqueue change last week. I should
> have rebased and reposted it before pinging you again. Will take care of
> it next time onwards.
> 
>>
>> Also note that you seem to have a double xchg() in there, also added
>> from 2/2.
> 
> Actually one xchg is tracking per group limit changes (tg) and one xchg()
> it tracking overall limit change per queue (td), meaning if any of
> the group on this queue has changed the limit or not. That avoids
> traversal of list of all the groups if none of the group has changed
> the limit.

Irk, it's the tg and td looking too similar. It's indeed not a double
xhcg(), sorry for the noise.

-- 
Jens Axboe

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