Re: [PATCH v3 02/17] block: use int64_t as bytes type in tracked requests

[Eric Blake <eblake@redhat.com>]

On 4/30/20 6:10 AM, Vladimir Sementsov-Ogievskiy wrote:
> We are generally moving to int64_t for both offset and bytes parameters
> on all io paths.
> 
> Main motivation is realization of 64-bit write_zeroes operation for
> fast zeroing large disk chunks, up to the whole disk.
> 
> We chose signed type, to be consistent with off_t (which is signed) and
> with possibility for signed return type (where negative value means
> error).
> 
> So, convert tracked requests now.
> 
> Series: 64bit-block-status
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---

>   static void tracked_request_begin(BdrvTrackedRequest *req,
>                                     BlockDriverState *bs,
>                                     int64_t offset,
> -                                  uint64_t bytes,
> +                                  int64_t bytes,
>                                     enum BdrvTrackedRequestType type)
>   {
> -    assert(bytes <= INT64_MAX && offset <= INT64_MAX - bytes);
> +    assert(offset >= 0 && bytes >= 0 &&
> +           bytes <= INT64_MAX && offset <= INT64_MAX - bytes);

'bytes <= INT64_MAX' was previously a real runtime check, but is now a 
tautology and therefore a dead branch; a picky compiler might complain. 
This assert could be compressed to:

assert(offset >= 0 && (uint64_t) bytes <= INT64_MAX - offset);

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