Re: [Qemu-block] [PATCH for-4.1 v2] qemu-img: Saner printing of large file sizes

[Max Reitz]

On 01.04.19 16:57, Eric Blake wrote:
> Disk sizes close to INT64_MAX cause overflow, for some pretty
> ridiculous output:
> 
>   $ ./nbdkit -U - memory size=$((2**63 - 512)) --run 'qemu-img info $nbd'
>   image: nbd+unix://?socket=/tmp/nbdkitHSAzNz/socket
>   file format: raw
>   virtual size: -8388607T (9223372036854775296 bytes)
>   disk size: unavailable
> 
> But there's no reason to have two separate implementations of integer
> to human-readable abbreviation, where one has overflow and stops at
> 'T', while the other avoids overflow and goes all the way to 'E'. With
> this patch, the output now claims 8EiB instead of -8388607T, which
> really is the correct rounding of largest file size supported by qemu
> (we could go 511 bytes larger if we used byte-accurate sizing instead
> of rounding up to the next sector boundary, but that wouldn't change
> the human-readable result).
> 
> Quite a few iotests need updates to expected output to match.
> 
> Reported-by: Richard W.M. Jones <address@hidden>
> Signed-off-by: Eric Blake <address@hidden>
> Tested-by: Richard W.M. Jones <address@hidden>
> Reviewed-by: Alberto Garcia <address@hidden>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> 
> v2 - actually update iotests to match; no change to block/ code so R-b added

There are more iotests this breaks.  First, there is 059 for vmdk, which
looks just like the rest.

But for -m32, it gets a bit more difficult.  Every size above 999 GB
(1000 GB gets rounded to 1 TB, which is 2^31 * 512) gets printed as
"inf [unit]":

$ ./qemu-img create -f qcow2 /tmp/foo.qcow2 1T
$ ./qemu-img info /tmp/foo.qcow2
[...]
virtual size: inf TiB (1099511627776 bytes)
[...]

$ ./qemu-img create -f qcow2 /tmp/foo.qcow2 1P
$ ./qemu-img info /tmp/foo.qcow2
[...]
virtual size: inf PiB (1125899906842624 bytes)
[...]

This breaks the iotests that test the maximum disk size of more exotic
formats.  I can see failures for vdi, vhdx, and parallels.

But regardless of the iotests, we shouldn’t show the size as infinite
just because of -m32.

Max

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