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Date: Wed, 08 Dec 2010 07:30:58 +0100
From: Jes Sorensen <Jes.Sorensen@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/1] qemu-img.c: Clean up handling of image
	size in img_create()
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org

On 12/07/10 21:36, Stefan Hajnoczi wrote:
> On Tue, Dec 7, 2010 at 5:39 PM,  <Jes.Sorensen@redhat.com> wrote:
>>     // The size for the image must always be specified, with one exception:
>>     // If we are using a backing file, we can obtain the size from there
>> -    if (get_option_parameter(param, BLOCK_OPT_SIZE)->value.n == -1) {
>> -
>> +    if (get_option_parameter(param, BLOCK_OPT_SIZE)->value.n == 0) {
>>         QEMUOptionParameter *backing_file =
>>             get_option_parameter(param, BLOCK_OPT_BACKING_FILE);
>>         QEMUOptionParameter *backing_fmt =
> 
> Today it is possible to create 0 byte sized images.  Your patch will
> change that:
> If there is a backing file, then the size will be taken from the backing file.
> If there is no backing file, then an error about missing size will be
> printed, even though a size of 0 has been given.
> 
> I don't think 0 sized images are very useful, but I'm not sure we
> should make this change.

The old code also fails if there is no size, except for when a backing
file is present.

I hadn't thought of the zero sized file, but on the other hand, I don't
see it being useful.

I would like to make this change to get the option handling cleaned up
as it allows me to refactor the code in img_create().

Cheers,
Jes