Re: [PATCH v7 6/8] block: make BlockConf size props 32bit and accept size suffixes

[Eric Blake]

On 5/28/20 4:39 PM, Roman Kagan wrote:
> Convert all size-related properties in BlockConf to 32bit.  This will
> allow to accomodate bigger block sizes (in a followup patch).

s/allow to accomodate/accommodate/

> This also allows to make them all accept size suffixes, either via
> DEFINE_PROP_BLOCKSIZE or via DEFINE_PROP_SIZE32.
>
> Also, since min_io_size is exposed to the guest by scsi and virtio-blk
> devices as an uint16_t in units of logical blocks, introduce an
> additional check in blkconf_blocksizes to prevent its silent truncation.
>
> Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
> ---

> +    if (conf->min_io_size / conf->logical_block_size > UINT16_MAX) {
> +        error_setg(errp,
> +                   "min_io_size must not exceed " stringify(UINT16_MAX)
> +                   " logical blocks");

On my libc, this results in "must not exceed (65535) logical blocks".

Worse, I could envision a platform where it prints something funky like:

"exceed (2 * (32768) + 1) logical", based on however complex the 
definition of UINT16_MAX is.  You're better off printing this one with 
%d than with stringify().

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org