Re: [PATCH v5 3/5] scsi: core: Cap shost max_sectors according to DMA limits only once

[Damien Le Moal]

On 6/30/22 21:08, John Garry wrote:
> The shost->max_sectors is repeatedly capped according to the host DMA
> mapping limit for each sdev in __scsi_init_queue(). This is unnecessary, so
> set only once when adding the host.
> 
> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> ---
>  drivers/scsi/hosts.c    | 5 +++++
>  drivers/scsi/scsi_lib.c | 4 ----
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 8352f90d997d..d04bd2c7c9f1 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -236,6 +236,11 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>  
>  	shost->dma_dev = dma_dev;
>  
> +	if (dma_dev->dma_mask) {
> +		shost->max_sectors = min_t(unsigned int, shost->max_sectors,
> +				dma_max_mapping_size(dma_dev) >> SECTOR_SHIFT);
> +	}

Nit: you could remove the curly brackets... But it being a multi-line
statement, having them is OK too I think.

> +
>  	error = scsi_mq_setup_tags(shost);
>  	if (error)
>  		goto fail;
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 6ffc9e4258a8..6ce8acea322a 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1884,10 +1884,6 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
>  		blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
>  	}
>  
> -	if (dev->dma_mask) {
> -		shost->max_sectors = min_t(unsigned int, shost->max_sectors,
> -				dma_max_mapping_size(dev) >> SECTOR_SHIFT);
> -	}
>  	blk_queue_max_hw_sectors(q, shost->max_sectors);
>  	blk_queue_segment_boundary(q, shost->dma_boundary);
>  	dma_set_seg_boundary(dev, shost->dma_boundary);

Looks good.

Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>

-- 
Damien Le Moal
Western Digital Research