linux-kernel - Re: [PATCH][next] scsi: scsi_debug: remove a redundant assignment to variable ret

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Message-ID: <2be706cc-0944-4413-b1b0-52d34fbdadf8@stanley.mountain>
Date: Wed, 2 Oct 2024 18:10:24 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Colin Ian King <colin.i.king@...il.com>
Cc: "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] scsi: scsi_debug: remove a redundant assignment to
 variable ret

On Wed, Oct 02, 2024 at 02:50:43PM +0100, Colin Ian King wrote:
> The variable ret is being assigned a value that is never read, the
> following break statement exits the loop where ret is being re-assigned
> a new value. Remove the redundant assignment.
> 
> Signed-off-by: Colin Ian King <colin.i.king@...il.com>
> ---
>  drivers/scsi/scsi_debug.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index d95f417e24c0..7c60f5acc4a3 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -3686,14 +3686,12 @@ static int do_device_access(struct sdeb_store_info *sip, struct scsi_cmnd *scp,
>  		sdeb_data_sector_lock(sip, do_write);
>  		ret = sg_copy_buffer(sdb->table.sgl, sdb->table.nents,

You would think there would be a:

	total += ret;

here.

>  		   fsp + (block * sdebug_sector_size),
>  		   sdebug_sector_size, sg_skip, do_write);
>  		sdeb_data_sector_unlock(sip, do_write);
> -		if (ret != sdebug_sector_size) {
> -			ret += (i * sdebug_sector_size);
> +		if (ret != sdebug_sector_size)
>  			break;
> -		}
>  		sg_skip += sdebug_sector_size;
>  		if (++block >= sdebug_store_sectors)
>  			block = 0;
>  	}
>  	ret = num * sdebug_sector_size;
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
And that this would be a "return total;"

The comment at the start of the function says that it's supposed to return the
actual number of bytes that were copied.  And you can see how that was the
intention.

But what it actually does is it always reports that it copied the complete
number of bytes.  #Success #Woohoo

I wouldn't feel comfortable changing it to report partial copies without testing
it.  Someone needs to look at it more carefully to figure out what the correct
fix is.

regards,
dan carpenter