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Re: [dm-devel] [PATCH] dm_crypt: Issue all previous bios before remapping barrier bio



On Tuesday 02 February 2010 18:17:24 Mikulas Patocka wrote:
> On Mon, 1 Feb 2010, Milan Broz wrote:
> > On 02/01/2010 04:19 PM, Nikanth Karthikesan wrote:
> > > Before remapping a barrier bio, make sure that there are no un-issued
> > > pending I/O in the workqueue. Otherwise a dm_flush would simply add
> > > a barrier request to the underlying device, without issuing the bio's
> > > queued in the dm_crypt device.
> >
> > This should not be needed. Core dm code waits for all bios submitted
> > before barrier requests.
> >
> > Mikulas, could you verify it?
> >
> > Milan
> 
> Yes, you are right, the patch is not needed.
> 
> When the target receives an empty barrier request, there are no other data
> requests in flight.
> 
> BTW. The target may receive more empty barrier requests simultaneously, if
> it asked for it by setting ti->num_flush_requests to more than one. But
> barrier and non-barrier requests are never mixed.
> 

Correct. Sorry, I was a bit hasty in sending that patch. It is not required. 
Thanks for the patient explanation.

Thanks
Nikanth


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