Re: [PATCH] 53c700: fix BUG on untagged commands

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On Mon, 2016-06-13 at 22:00 -0700, James Bottomley wrote:
> The untagged command case in the 53c700 driver has been broken since
> host wide tags were enabled because the replaced scsi_find_tag()
> function had a special case for the tag value SCSI_NO_TAG to retrieve
> sdev->current_cmnd.  The replacement function scsi_host_find_tag() has
> no such special case and returns NULL causing untagged commands to
> trigger a BUG() in the driver.  Inspection shows that the 53c700 is the
> only driver using this SCSI_NO_TAG case, so a local fix in the driver
> suffices to fix this problem globally.
> 
> Fixes: 64d513ac31b - "scsi: use host wide tags by default"
> Cc: stable@xxxxxxxxxxxxxxx	# 4.4+
> Reported-by: Helge Deller <deller@xxxxxx>
> Tested-by: Helge Deller <deller@xxxxxx>
> Signed-off-by: James Bottomley <jejb@xxxxxxxxxxxxxxxxxx>
> 
> ---
> 
> diff --git a/drivers/scsi/53c700.c b/drivers/scsi/53c700.c
> index d4c2856..3ddc85e 100644
> --- a/drivers/scsi/53c700.c
> +++ b/drivers/scsi/53c700.c
> @@ -1122,7 +1122,7 @@ process_script_interrupt(__u32 dsps, __u32 dsp, struct scsi_cmnd *SCp,
>  		} else {
>  			struct scsi_cmnd *SCp;
>  
> -			SCp = scsi_host_find_tag(SDp->host, SCSI_NO_TAG);
> +			SCp = SDp->current_cmnd;
>  			if(unlikely(SCp == NULL)) {
>  				sdev_printk(KERN_ERR, SDp,
>  					"no saved request for untagged cmd\n");
> @@ -1826,7 +1826,7 @@ NCR_700_queuecommand_lck(struct scsi_cmnd *SCp, void (*done)(struct scsi_cmnd *)
>  		       slot->tag, slot);
>  	} else {
>  		slot->tag = SCSI_NO_TAG;
> -		/* must populate current_cmnd for scsi_host_find_tag to work */
> +		/* save current command for reselection */
>  		SCp->device->current_cmnd = SCp;
>  	}
>  	/* sanity check: some of the commands generated by the mid-layer
> 
> 
> --
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Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>



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