[GEDI] [PATCH v2 01/17] block/throttle-groups: throttle_group_co_io_limits_intercept(): 64bit bytes

Eric Blake eblake at redhat.com
Mon Apr 27 14:12:12 UTC 2020

On 4/27/20 5:05 AM, Philippe Mathieu-Daudé wrote:
> On 4/27/20 10:23 AM, Vladimir Sementsov-Ogievskiy wrote:
>> The function is called from 64bit io handlers, and bytes is just passed
>> to throttle_account() which is 64bit too (unsigned though). So, let's
>> convert intermediate argument to 64bit too.
> What is the meaning of negative bytes in this function?

An error.  It is more for consistency, in that we really cannot access 
more than 63 bits of size information (off_t is signed, and network 
protocols don't magically add a 64th bit to that underlying inherent 
limitation of files and block devices).

It may be worth adding assert(bytes >= 0), if that makes it easier to 
prove we are only dealing with positive lengths.

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

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