Re: [PATCH 11/14] scsi: unwind blk_end_request_all and blk_end_request_err calls

[Hannes Reinecke]

On 06/25/2014 06:51 PM, Christoph Hellwig wrote:
> Replace the calls to the various blk_end_request variants with opencode
> equivalents.  Blk-mq is using a model that gives the driver control
> between the bio updates and the actual completion, and making the old
> code follow that same model allows us to keep the code more similar for
> both pathes.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>   drivers/scsi/scsi_lib.c |   61 ++++++++++++++++++++++++++++++++---------------
>   1 file changed, 42 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a64b9d3..58534fd 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -625,6 +625,37 @@ static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
>   	cmd->request->next_rq->special = NULL;
>   }
>
> +static bool scsi_end_request(struct request *req, int error,
> +		unsigned int bytes, unsigned int bidi_bytes)
> +{
> +	struct scsi_cmnd *cmd = req->special;
> +	struct scsi_device *sdev = cmd->device;
> +	struct request_queue *q = sdev->request_queue;
> +	unsigned long flags;
> +
> +
> +	if (blk_update_request(req, error, bytes))
> +		return true;
> +
> +	/* Bidi request must be completed as a whole */
> +	if (unlikely(bidi_bytes) &&
> +	    blk_update_request(req->next_rq, error, bidi_bytes))
> +		return true;
> +
> +	if (blk_queue_add_random(q))
> +		add_disk_randomness(req->rq_disk);
> +
> +	spin_lock_irqsave(q->queue_lock, flags);
> +	blk_finish_request(req, error);
> +	spin_unlock_irqrestore(q->queue_lock, flags);
> +
> +	if (bidi_bytes)
> +		scsi_release_bidi_buffers(cmd);
> +	scsi_release_buffers(cmd);
> +	scsi_next_command(cmd);
> +	return false;
> +}
> +
>   /**
>    * __scsi_error_from_host_byte - translate SCSI error code into errno
>    * @cmd:	SCSI command (unused)
> @@ -697,7 +728,7 @@ static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
>    *		   be put back on the queue and retried using the same
>    *		   command as before, possibly after a delay.
>    *
> - *		c) We can call blk_end_request() with -EIO to fail
> + *		c) We can call scsi_end_request() with -EIO to fail
>    *		   the remainder of the request.
>    */
>   void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
> @@ -749,13 +780,9 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>   			 * both sides at once.
>   			 */
>   			req->next_rq->resid_len = scsi_in(cmd)->resid;
> -
> -			scsi_release_buffers(cmd);
> -			scsi_release_bidi_buffers(cmd);
> -
> -			blk_end_request_all(req, 0);
> -
> -			scsi_next_command(cmd);
> +			if (scsi_end_request(req, 0, blk_rq_bytes(req),
> +					blk_rq_bytes(req->next_rq)))
> +				BUG();
>   			return;
>   		}
>   	}
> @@ -794,15 +821,16 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>   	/*
>   	 * If we finished all bytes in the request we are done now.
>   	 */
> -	if (!blk_end_request(req, error, good_bytes))
> -		goto next_command;
> +	if (!scsi_end_request(req, error, good_bytes, 0))
> +		return;
>
>   	/*
>   	 * Kill remainder if no retrys.
>   	 */
>   	if (error && scsi_noretry_cmd(cmd)) {
> -		blk_end_request_all(req, error);
> -		goto next_command;
> +		if (scsi_end_request(req, error, blk_rq_bytes(req), 0))
> +			BUG();
> +		return;
>   	}
>
>   	/*
> @@ -947,8 +975,8 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>   				scsi_print_sense("", cmd);
>   			scsi_print_command(cmd);
>   		}
> -		if (!blk_end_request_err(req, error))
> -			goto next_command;
> +		if (!scsi_end_request(req, error, blk_rq_err_bytes(req), 0))
> +			return;
>   		/*FALLTHRU*/
>   	case ACTION_REPREP:
>   	requeue:
> @@ -967,11 +995,6 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>   		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
>   		break;
>   	}
> -	return;
> -
> -next_command:
> -	scsi_release_buffers(cmd);
> -	scsi_next_command(cmd);
>   }
>
>   static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
YES.

That code really was a mess.

Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke		      zSeries & Storage
hare@xxxxxxx			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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