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Date: Tue, 19 Jan 2010 19:51:28 +0100
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [PATCH 07/10] qcow2: Improve error handling in
	update_refcount
Message-ID: <20100119185128.GA31526@lst.de>
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	<1263816696-24122-8-git-send-email-kwolf@redhat.com>
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To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org

On Mon, Jan 18, 2010 at 01:11:33PM +0100, Kevin Wolf wrote:
> If update_refcount fails, try to undo any changes made so far to avoid
> inconsistencies in the image file.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2-refcount.c |   32 +++++++++++++++++++++++++-------
>  1 files changed, 25 insertions(+), 7 deletions(-)
> 

> +    /*
> +     * Try do undo any updates if an error is returned (This may succeed in
> +     * some cases like ENOSPC for allocating a new refcount block)
> +     */
> +    if (ret < 0) {
> +        int dummy;
> +        dummy = update_refcount(bs, offset, cluster_offset - offset, -addend);

So we recursively call into update_refcount here.  What happens an error
causes all updates to fail?