Re: [Qemu-block] [Qemu-devel] [PATCH v5 14/18] qcow2: Switch qcow2_measure() to byte-based iteration

2017-07-14 Thread Eric Blake 
On 07/13/2017 01:49 PM, John Snow wrote:
> 
> 
> On 07/12/2017 09:05 PM, Eric Blake wrote:
>> This is new code, but it is easier to read if it makes passes over
>> the image using bytes rather than sectors (and will get easier in
>> the future when bdrv_get_block_status is converted to byte-based).
>>
>> While at it, fix a bug in the computation of nb_sectors using MAX
>> rather than MIN and thus always passing INT_MAX (thankfully, the
>> bug was harmless, as bdrv_get_block_status_above() clamps its
>> answers according to image size).
>>
> 
> Well, unless ssize was >= 2^40, and then it wouldn't have chosen
> INT_MAX, right!?

But then it would have wrapped the value around while assigning it to
'int nb_sectors'.  I suppose for some very-interesting size images, you
could get nb_sectors to turn into a negative value?  At any rate, it's
good the bug was short-lived.

> 
>> Signed-off-by: Eric Blake 
>>
> 
> Reviewed-by: John Snow 
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3266
Virtualization:  qemu.org | libvirt.org



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Re: [Qemu-block] [Qemu-devel] [PATCH v5 14/18] qcow2: Switch qcow2_measure() to byte-based iteration

2017-07-13 Thread John Snow 


On 07/12/2017 09:05 PM, Eric Blake wrote:
> This is new code, but it is easier to read if it makes passes over
> the image using bytes rather than sectors (and will get easier in
> the future when bdrv_get_block_status is converted to byte-based).
> 
> While at it, fix a bug in the computation of nb_sectors using MAX
> rather than MIN and thus always passing INT_MAX (thankfully, the
> bug was harmless, as bdrv_get_block_status_above() clamps its
> answers according to image size).
> 

Well, unless ssize was >= 2^40, and then it wouldn't have chosen
INT_MAX, right!?

> Signed-off-by: Eric Blake 
> 

Reviewed-by: John Snow