Re: [PATCH] 2.6.25-rc4-git3 - inquiry cmd issued via /dev/sg? device causes infinite loop in 2.6.24

[Michael Reed <mdr@sgi.com>]

Boaz Harrosh wrote:
<snip>
>>
>>> Just to demonstrate what I mean a patch is attached. Just as an RFC, totally
>>> untested.
>> I can try this out and see what happens.
>>
>>
> Will not compile here is a cleaner one

Still in my queue.  Hopefully I'll get to poke at this today.

Mike

> 
> ---
> From: Boaz Harrosh <bharrosh@panasas.com>
> Date: Wed, 12 Mar 2008 13:18:49 +0200
> Subject: [PATCH] scsi: Always complete BLOCK_PC commands
> 
> Current code, in some IO combinations could wrongly retry
> a BLOCK_PC command in chunks. This was never intended.
> Fix it that BLOCK_PC will always complete atomically
> 
> Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
> ---
>  drivers/scsi/scsi_lib.c |   24 +++++++++++++-----------
>  1 files changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index ba21d97..4b8b57c 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -784,14 +784,20 @@ EXPORT_SYMBOL(scsi_release_buffers);
>   * in req->data_len and req->next_rq->data_len. The upper-layer driver can
>   * decide what to do with this information.
>   */
> -void scsi_end_bidi_request(struct scsi_cmnd *cmd)
> +static void scsi_end_blk_request(struct scsi_cmnd *cmd)
>  {
>  	struct request *req = cmd->request;
>  	unsigned int dlen = req->data_len;
> -	unsigned int next_dlen = req->next_rq->data_len;
> +	unsigned int next_dlen;
>  
> -	req->data_len = scsi_out(cmd)->resid;
> -	req->next_rq->data_len = scsi_in(cmd)->resid;
> +	if (blk_bidi_rq(req)) {
> +		next_dlen = req->next_rq->data_len;
> +		req->data_len = scsi_out(cmd)->resid;
> +		req->next_rq->data_len = scsi_in(cmd)->resid;
> +	} else {
> +		next_dlen = 0;
> +		req->data_len = scsi_get_resid(cmd);
> +	}
>  
>  	/* The req and req->next_rq have not been completed */
>  	BUG_ON(blk_end_bidi_request(req, 0, dlen, next_dlen));
> @@ -866,15 +872,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>  				req->sense_len = len;
>  			}
>  		}
> -		if (scsi_bidi_cmnd(cmd)) {
> -			/* will also release_buffers */
> -			scsi_end_bidi_request(cmd);
> -			return;
> -		}
> -		req->data_len = scsi_get_resid(cmd);
> +		/* will also release_buffers */
> +		scsi_end_blk_request(cmd);
> +		return;
>  	}
>  
> -	BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet */
>  	scsi_release_buffers(cmd);
>  
>  	/*