[stable] [PATCH 00/16]: Fix writeback regressions in 2.6.32

[Jens Axboe]

On 08/11/2010 03:59 PM, Greg KH wrote:
> On Tue, Aug 10, 2010 at 11:28:48AM +0200, Stefan Bader wrote:
>> Impact: 2.6.32 is facing some serious performance regression which are visible
>> plainly when unmounting filesystems as async writeback degrades to sync in
>> that case. But there seem to be other less visible problems as well.
>> I believe this set of patches also would be benefitial to go into upstream
>> stable.
>>
>> Fix: This series of patches was picked and backported when needed to apply
>> to 2.6.32.y (there is another set for 2.6.34.y[1]). It probably does not
>> solve all currently known problems but testing has shown considerable
>> improvements. At the beginning of the set there are some patches that were
>> picked to make the later patches applicable. Only one of them is a bit more
>> intrusive the others rather trivial.
>>
>> Testcase: Unmounting a fs that still has larger amounts of data to write back
>> to disk will take noticably longer time to complete (IIRC might be 30min).
>> Also general responsiveness was reported to improve. Currently there are no
>> known regressions reported when testing this backport.
> 
> Jens, what do you think about this series?

I think it is scary :-)

But seriously, we need to do something about this umount regression and
there's likely no way around this series. Doing the full backport is
the best option. Stefan, to what extent did you test this backport?

-- 
Jens Axboe