From: Max Reitz <mreitz@redhat.com>
To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Max Reitz <mreitz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 1/2] block/drive-mirror: Check for NULL backing_hd
Date: Tue, 05 Nov 2013 01:33:50 +0100 [thread overview]
Message-ID: <52783CEE.2020808@redhat.com> (raw)
In-Reply-To: <1383611413-21528-1-git-send-email-mreitz@redhat.com>
On 05.11.2013 01:30, Max Reitz wrote:
> It should be possible to execute the QMP "drive-mirror" command in
> "none" sync mode and "absolute-paths" mode even for block devices
> lacking a backing file.
>
> "absolute-paths" does in fact not require a backing file to be present,
> as can be seen from the "top" sync mode code path. "top" basically
> states that the device should indeed have a backing file - however, the
> current code catches the case if it doesn't and then simply treats it as
> "full" sync mode, creating a target image without a backing file (in
> "absolute-paths" mode). Thus, "absolute-paths" does not imply the target
> file must indeed have a backing file.
>
> Therefore, the target file may be left unbacked in case of "none" sync
> mode as well, if the specified device is not backed either. Currently,
> qemu will crash trying to dereference the backing file pointer since it
> assumes that it will always be non-NULL in that case ("none" with
> "absolute-paths").
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
Sorry, forgot the cover letter, will send a v2.
Max
prev parent reply other threads:[~2013-11-05 0:34 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-05 0:30 [Qemu-devel] [PATCH 1/2] block/drive-mirror: Check for NULL backing_hd Max Reitz
2013-11-05 0:33 ` Max Reitz [this message]
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