Re: [PATCH] Only print SCSI data direction warning once for a command

[Douglas Gilbert]

Andi Kleen wrote:
> > to the log because they come from printk_ratelimit().  So all you've
> > done is halved the volume of flow to the logs and left a dangling printk
> > suppressed message that keeps spewing, so I don't think the patch even
> > does what you describe it as doing ...  if you reverse the order of the
> > operands in the if() it will ...
>
> Here's an updated patch with the reversed order.
>
> -Andi
>
> ---
>
> Only print SCSI data direction warning once for a command v2
>
> When I use cdparanoia my logs get spammed a lot by
>
> printk: 464 messages suppressed.
> sg_write: data in/out 30576/30576 bytes for SCSI command 0xbe--guessing data in;
>    program cdparanoia not setting count and/or reply_len properly
> printk: 1078 messages suppressed.
>
> and many more of those. With this patch the message is only printed once
> for a command in a row.
>
> v1->v2: Prevent rate limit messages too (pointed out by jejb)
>
> Signed-off-by: Andi Kleen <ak@xxxxxxx>
>
> ---
>  drivers/scsi/sg.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> Index: linux/drivers/scsi/sg.c
> ===================================================================
> --- linux.orig/drivers/scsi/sg.c
> +++ linux/drivers/scsi/sg.c
> @@ -602,8 +602,9 @@ sg_write(struct file *filp, const char _
>  	 * but is is possible that the app intended SG_DXFER_TO_DEV, because there
>  	 * is a non-zero input_size, so emit a warning.
>  	 */
> -	if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV)
> -		if (printk_ratelimit())
> +	if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV) {
> +		static char cmd[TASK_COMM_LEN];
> +		if (strcmp(current->comm, cmd) && printk_ratelimit()) {
>  			printk(KERN_WARNING
>  			       "sg_write: data in/out %d/%d bytes for SCSI command 0x%x--"
>  			       "guessing data in;\n" KERN_WARNING "   "
> @@ -611,6 +612,9 @@ sg_write(struct file *filp, const char _
>  			       old_hdr.reply_len - (int)SZ_SG_HEADER,
>  			       input_size, (unsigned int) cmnd[0],
>  			       current->comm);
> +			strcpy(cmd, current->comm);
> +		}
> +	}
>  	k = sg_common_write(sfp, srp, cmnd, sfp->timeout, blocking);
>  	return (k < 0) ? k : count;
>  }

Signed-off-by: Douglas Gilbert <dougg@xxxxxxxxxx>

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