Re: [PATCH] block: soft limit zone-append sectors as well

[Jens Axboe <axboe@kernel.dk>]

On 10/7/20 3:20 AM, Johannes Thumshirn wrote:
> Martin rightfully noted that for normal filesystem IO we have soft limits
> in place, to prevent them from getting too big and not lead to
> unpredictable latencies. For zone append we only have the hardware limit
> in place.
> 
> Cap the max sectors we submit via zone-append to the maximal number of
> sectors if the second limit is lower.
> 
> Link: https://lore.kernel.org/linux-btrfs/yq1k0w8g3rw.fsf@ca-mkp.ca.oracle.com
> Reported-by: Martin K. Petersen <martin.petersen@oracle.com>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  include/linux/blkdev.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index cf80e61b4c5e..967cd76f16d4 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1406,7 +1406,10 @@ static inline unsigned int queue_max_segment_size(const struct request_queue *q)
>  
>  static inline unsigned int queue_max_zone_append_sectors(const struct request_queue *q)
>  {
> -	return q->limits.max_zone_append_sectors;
> +
> +	struct queue_limits *l = q->limits;
> +
> +	return min(l->max_zone_append_sectors, l->max_sectors);

As the test robot points out, this won't even compile... How much
testing did you do with this?

-- 
Jens Axboe