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

[John Garry via iommu]

On 01/07/2022 00:41, Damien Le Moal wrote:
  
  	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.



tglx seems to think that they are ok, and I generally agree (now):

https://lore.kernel.org/linux-arm-kernel/877djwdorz@nanos.tec.linutronix.de/

AFAICT coding-style.rst is ok with them in this scenario too

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

[Damien Le Moal via iommu]

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 
> ---
>  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 Le Moal
Western Digital Research
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[PATCH v5 3/5] scsi: core: Cap shost max_sectors according to DMA limits only once

[John Garry via iommu]

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 
---
 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);
+   }
+
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);
-- 
2.35.3

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