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Date: Tue, 13 Sep 2016 16:35:18 +0100
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20160913153518.GA5677@stefanha-x1.localdomain>
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Subject: Re: [Qemu-devel] [PATCH v5] qemu-img: change opening method for the
 output in dd
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To: Reda Sallahi <fullmanet@gmail.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>, Fam Zheng <famz@redhat.com>


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On Fri, Aug 26, 2016 at 09:19:40AM +0200, Reda Sallahi wrote:
> -    blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
> -                    false, false);
> +    ret = access(out_filename, F_OK); /* Check if file exists */

The QEMU block layer does not use POSIX file I/O because it needs to
support protocols like iSCSI and ssh.

The only way to test for the existence of a disk image is by opening it
with block layer APIs.

Can you just move the img_open() call from the else statement up here
instead?

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