Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush

[Tejun Heo <teheo suse de>]

Hello,

On 08/18/2010 08:35 AM, Tejun Heo wrote:
>> It's not bisecting to find bugs in the barrier conversion.  We can't
>> easily bisect it down anyway.  The problem is when we try to bisect
>> other problems and get into the middle of the series barriers suddenly
>> are gone.  Which is not very helpful for things like data integrity
>> problems in filesystems.
> 
> Ah, okay, hmmm.... alright, I'll resequence the patches.  If the
> filesystem changes can be put into a single tree somehow, we can keep
> things mostly working at least for direct devices.

Sorry but I'm doing it.  It just doesn't make much sense.  I can't
relax the ordering for REQ_HARDBARRIER without breaking the remapping
drivers.  So, to keep things working, I'll have to 1. relax the
ordering 2. implement new REQ_FLUSH/FUA based interface and 3. use
them in the filesystems in the same patch.  That's just wrong.  And I
don't think md/dm changes can or should go through the block tree.
They're way too invasive for that.  It's a new implementation and
barrier won't work (fail gracefully) for several commits during the
transition.  I don't think there's a better way around it.

Thanks.

-- 
tejun