Re: [PATCH 1/5] sd: configure ZBC devices

["Ewan D. Milne" <emilne@redhat.com>]

On Mon, 2016-07-25 at 08:00 +0200, Hannes Reinecke wrote:
> On 07/24/2016 12:04 AM, Bart Van Assche wrote:
> > On 07/23/16 13:31, Hannes Reinecke wrote:
> >> On 07/22/2016 11:56 PM, Ewan D. Milne wrote:
> >>>
> >>> So, blk_queue_chunk_sectors() has:
> >>>
> >>> void blk_queue_chunk_sectors(struct request_queue *q, unsigned int
> >>> chunk_sectors)
> >>> {
> >>>         BUG_ON(!is_power_of_2(chunk_sectors));
> >>>         q->limits.chunk_sectors = chunk_sectors;
> >>> }
> >>>
> >>> and it seems like if some device reports a non-power-of-2 zone_len
> >>> then we
> >>> will BUG_ON().  Probably would be better if we reported an error
> >>> instead?
> >>>
> >> The ZBC spec mandates that the zone size must be a power of 2.
> >> So I don't have problems with triggering a BUG_ON for non-compliant
> >> drives.
> > 
> > Triggering BUG_ON() if zone_len is not a power of two is completely
> > unacceptable. No matter what zone information a ZBC drive exports that
> > shouldn't result in a kernel oops.
> > 
> Ok, will be fixing this.
> 
> Cheers,
> 
> Hannes

Yes, unfortunately we have too much history with non-compliant devices.
And, I much prefer to avoid crashing the kernel if it is not necessary.

Thanks.

-Ewan