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Date: Wed, 15 Mar 2017 21:13:43 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] blk: fix aio context loss on media change
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To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, pbonzini@redhat.com, jsnow@redhat.com

On Wed, 03/15 13:06, Kevin Wolf wrote:
> > > 
> > > Stefan, Paolo, do you remember the details why we didn't even do a
> > > simple fix like the one below? I think there were some patches on the
> > > list, no?
> > 
> > ISTM the concern was mostly "what about other BB in the graph?"
> > 
> > Should the new op blocker API be used in this one (a new type of perm)?
> 
> If we know what operation to block, that's an option. Would "change the
> node's AioContext" work for it?
> 
> I think it would effectively mean that you need to attach the device
> first and then jobs etc. respect the AioContext, whereas the opposite
> order breaks because they don't have callbacks to adjust the AioContext
> after the fact.
> 
> This seems to match what's actually safe, so it might really be as easy
> as this.

Yes, this sounds good to me.

Vladimir, would you like to implement this? It would be good to have this fixed
in 2.9.

Fam