Re: [PATCH] block: fix revalidate performance regression

[Hannes Reinecke <hare@suse.de>]

On 5/29/23 04:38, Damien Le Moal wrote:
> The scsi driver function sd_read_block_characteristics() always calls
> disk_set_zoned() to a disk zoned model correctly, in case the device
> model changed. This is done even for regular disks to set the zoned
> model to BLK_ZONED_NONE and free any zone related resources if the drive
> previously was zoned.
> 
> This behavior significantly impact the time it takes to revalidate disks
> on a large system as the call to disk_clear_zone_settings() done from
> disk_set_zoned() for the BLK_ZONED_NONE case results in the device
> request queued to be quiesced, even if there is no zone resource to
> free.
> 
> Avoid this overhead for non zoned devices by not calling
> disk_clear_zone_settings() in disk_set_zoned() if the device model
> already was set to BLK_ZONED_NONE.
> 
> Reported by: Brian Bunker <brian@purestorage.com>
> Fixes: 508aebb80527 ("block: introduce blk_queue_clear_zone_settings()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>   block/blk-settings.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 896b4654ab00..4dd59059b788 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -915,6 +915,7 @@ static bool disk_has_partitions(struct gendisk *disk)
>   void disk_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
>   {
>   	struct request_queue *q = disk->queue;
> +	unsigned int old_model = q->limits.zoned;
>   
>   	switch (model) {
>   	case BLK_ZONED_HM:
> @@ -952,7 +953,7 @@ void disk_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
>   		 */
>   		blk_queue_zone_write_granularity(q,
>   						queue_logical_block_size(q));
> -	} else {
> +	} else if (old_model != BLK_ZONED_NONE) {
>   		disk_clear_zone_settings(disk);
>   	}
>   }
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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