Re: [Qemu-devel] [Qemu-block] [PATCH] qcow2: Fix qcow2_make_empty() with external data file

From: Stefan Hajnoczi <stefanha@gmail.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org,
	qemu-stable@nongnu.org, mreitz@redhat.com
Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] qcow2: Fix qcow2_make_empty() with external data file
Date: Mon, 29 Apr 2019 12:13:31 -0400	[thread overview]
Message-ID: <20190429161331.GC13640@stefanha-x1.localdomain> (raw)
In-Reply-To: <20190429105741.31033-1-kwolf@redhat.com>

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On Mon, Apr 29, 2019 at 12:57:41PM +0200, Kevin Wolf wrote:
> make_completely_empty() is an optimisated path for bdrv_make_empty()
> where completely new metadata is created inside the image file instead
> of going through all clusters and discarding them. For an external data
> file, however, we actually need to do discard operations on the data
> file; just overwriting the qcow2 file doesn't get rid of the data.
> 
> The necessary slow path with an explicit discard operation already
> exists for other cases. Use it for external data files, too.
> 
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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