Re: [Qemu-devel] [PATCH 0/3] block: fix blk_aio_*() segfault when blk->root == NULL

[Eric Blake <eblake@redhat.com>]

On 02/08/2018 11:18 AM, Stefan Hajnoczi wrote:
> Using bdrv_inc_in_flight(blk_bs(blk)) doesn't work since BlockBackend->root may
> be NULL.
> 
> This patch series solves the issue by adding an BlockBackend->in_flight counter
> so requests can be tracked even when there is no BlockDriverState.
> 
> This should fix the IDE and virtio-blk segfaults that have been encountered
> when there is no BlockDriverState.
> 
> The patch is based on work by Kevin Wolf.
> 
> Kevin Wolf (1):
>    block: test blk_aio_flush() with blk->root == NULL
> 
> Stefan Hajnoczi (2):
>    block: add BlockBackend->in_flight counter
>    Revert "IDE: Do not flush empty CDROM drives"

Tested by applying the series out of order (2, 3, 1) - the new test 
fails after 2 (so even our workaround was not robust), fails after 3 
(expected there, because we revert the workaround), then finally passes 
after 1 (the correct fix with no workaround needed).  So for the series, 
you can add:
Tested-by: Eric Blake <eblake@redhat.com>

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