[PATCH] scsi: fix the return value of scsi_logical_block_count

[PATCH] scsi: fix the return value of scsi_logical_block_count

[Chaotian Jing]

scsi_logical_block_count() should return the block count of scsi device,
but the original code has a wrong implement.

Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
---
 include/scsi/scsi_cmnd.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 45c40d200154..f0be0caa295a 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -236,7 +236,7 @@ static inline unsigned int scsi_logical_block_count(struct scsi_cmnd *scmd)
 {
 	unsigned int shift = ilog2(scmd->device->sector_size) - SECTOR_SHIFT;
 
-	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
+	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;
 }
 
 /*
-- 
2.46.0

Re: [PATCH] scsi: fix the return value of scsi_logical_block_count

[Bart Van Assche]

On 8/6/24 12:26 AM, Chaotian Jing wrote:
> scsi_logical_block_count() should return the block count of scsi device,
> but the original code has a wrong implement.
> 
> Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
> ---
>   include/scsi/scsi_cmnd.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
> index 45c40d200154..f0be0caa295a 100644
> --- a/include/scsi/scsi_cmnd.h
> +++ b/include/scsi/scsi_cmnd.h
> @@ -236,7 +236,7 @@ static inline unsigned int scsi_logical_block_count(struct scsi_cmnd *scmd)
>   {
>   	unsigned int shift = ilog2(scmd->device->sector_size) - SECTOR_SHIFT;
>   
> -	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
> +	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;
>   }
>   
>   /*

Please add the following to this patch:

Cc: stable@vger.kernel.org
Fixes: 6a20e21ae1e2 ("scsi: core: Add helper to return number of logical 
blocks in a request")

Anyway:

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

[PATCH] scsi: fix the return value of scsi_logical_block_count

[Chaotian Jing]

scsi_logical_block_count() should return the block count of scsi device,
but the original code has a wrong implement.

Cc: stable@vger.kernel.org
Fixes: 6a20e21ae1e2 ("scsi: core: Add helper to return number of logical
blocks in a request")
Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
---
 include/scsi/scsi_cmnd.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 45c40d200154..f0be0caa295a 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -236,7 +236,7 @@ static inline unsigned int scsi_logical_block_count(struct scsi_cmnd *scmd)
 {
 	unsigned int shift = ilog2(scmd->device->sector_size) - SECTOR_SHIFT;
 
-	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
+	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;
 }
 
 /*
-- 
2.46.0

Re: [PATCH] scsi: fix the return value of scsi_logical_block_count

[John Garry]

On 06/08/2024 08:26, Chaotian Jing wrote:
> scsi_logical_block_count() should return the block count of scsi device,

scsi command, not scsi device

> but the original code has a wrong implement.
> 
> Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
> ---
>   include/scsi/scsi_cmnd.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
> index 45c40d200154..f0be0caa295a 100644
> --- a/include/scsi/scsi_cmnd.h
> +++ b/include/scsi/scsi_cmnd.h
> @@ -236,7 +236,7 @@ static inline unsigned int scsi_logical_block_count(struct scsi_cmnd *scmd)

I find it questionable why we have this in the core code, since it's 
only used in error handling logs for one driver. And obviously no one 
was paying attention to it.

>   {
>   	unsigned int shift = ilog2(scmd->device->sector_size) - SECTOR_SHIFT;
>   
> -	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
> +	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;

blk_rq_sectors() converts from bytes to linux sectors, and then we shift 
it by diff in linux sectors and LBS.

To me, if this were used in fastpath - which it isn't - the following 
seems better:

return blk_rq_bytes(scsi_cmd_to_rq(scmd)) / scmd->device->sector_size;

>   }
>   
>   /*

Re: [PATCH] scsi: fix the return value of scsi_logical_block_count

[Martin K. Petersen]

Chaotian,

> @@ -236,7 +236,7 @@ static inline unsigned int scsi_logical_block_count(struct scsi_cmnd *scmd)
>  {
>  	unsigned int shift = ilog2(scmd->device->sector_size) - SECTOR_SHIFT;
>  
> -	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
> +	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;
>  }

There's no point in shifting twice by converting to sectors first.
Please just remove the SECTOR_SHIFT subtraction.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH] scsi: fix the return value of scsi_logical_block_count

[Chaotian Jing (井朝天)]

On Mon, 2024-08-12 at 21:52 -0400, Martin K. Petersen wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  
> Chaotian,
> 
> > @@ -236,7 +236,7 @@ static inline unsigned int
> scsi_logical_block_count(struct scsi_cmnd *scmd)
> >  {
> >  	unsigned int shift = ilog2(scmd->device->sector_size) -
> SECTOR_SHIFT;
> >  
> > -	return blk_rq_bytes(scsi_cmd_to_rq(scmd)) >> shift;
> > +	return blk_rq_sectors(scsi_cmd_to_rq(scmd)) >> shift;
> >  }
> 
> There's no point in shifting twice by converting to sectors first.
> Please just remove the SECTOR_SHIFT subtraction.
> 
Thanks, will fix it at next version.
> -- 
> Martin K. Petersen	Oracle Linux Engineering