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References: <20180213142102.14450-1-stefanha@redhat.com>
	<20180213142102.14450-3-stefanha@redhat.com>
From: Eric Blake <eblake@redhat.com>
Message-ID: <49797c75-1e96-10fe-4be5-58cd2b0ebd7f@redhat.com>
Date: Tue, 13 Feb 2018 10:03:55 -0600
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Subject: Re: [Qemu-devel] [PATCH v2 2/4] block: add BlockBackend->in_flight
 counter
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To: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, John Snow <jsnow@redhat.com>

On 02/13/2018 08:21 AM, Stefan Hajnoczi wrote:
> BlockBackend currently relies on BlockDriverState->in_flight to track
> requests for blk_drain().  There is a corner case where
> BlockDriverState->in_flight cannot be used though: blk->root can be NULL
> when there is no medium.  This results in a segfault when the NULL
> pointer is dereferenced.
> 
> Introduce a BlockBackend->in_flight counter for aio requests so it works
> even when blk->root == NULL.
> 
> Based on a patch by Kevin Wolf <kwolf@redhat.com>.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   block.c               |  2 +-
>   block/block-backend.c | 60 +++++++++++++++++++++++++++++++++++++++++++++------
>   2 files changed, 54 insertions(+), 8 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org