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Date: Mon, 23 May 2016 09:00:40 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/3] blockdev-backup: Don't move target
 AioContext if it's attached
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To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>, Markus Armbruster <armbru@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, qemu-block@nongnu.org

On Fri, 05/20 10:03, Kevin Wolf wrote:
> Am 18.05.2016 um 10:24 hat Fam Zheng geschrieben:
> > If the BDS is attached, it will want to stay on the AioContext where its
> > BlockBackend is. Don't call bdrv_set_aio_context in this case.
> > 
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  blockdev.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > diff --git a/blockdev.c b/blockdev.c
> > index 1892b8e..eb15593 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -3376,8 +3376,18 @@ void do_blockdev_backup(const char *device, const char *target,
> >      }
> >      target_bs = blk_bs(target_blk);
> >  
> > +    if (bdrv_get_aio_context(target_bs) != aio_context) {
> > +        if (!target_bs->blk) {
> 
> How should this ever happen when we have target_bs = blk_bs(target_blk)
> two lines above?

I must have made a mistake with git or my editor, I meant to change it to
bdrv_lookup_bs above.

Fam

> 
> > +            /* The target BDS is not attached, we can safely move it to another
> > +             * AioContext. */
> > +            bdrv_set_aio_context(target_bs, aio_context);
> > +        } else {
> > +            error_setg(errp, "Target is attached to a different thread from "
> > +                             "source.");
> > +            goto out;
> > +        }
> > +    }
> 
> Kevin