[PATCH 1/2] scsi: explicitly release bidi buffers

[PATCH 1/2] scsi: explicitly release bidi buffers

[Christoph Hellwig]

Instead of trying to guess when we have a BIDI buffer in scsi_release_buffers
add a function to explicitly free the BIDI ressoures in the one place that
handles them.  This avoids needing a special __scsi_release_buffers for the
case where we already have freed the request as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index debe30a..3012700 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -511,8 +511,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-static void __scsi_release_buffers(struct scsi_cmnd *, int);
-
 /*
  * Function:    scsi_end_request()
  *
@@ -568,7 +566,7 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
 	 * This will goose the queue request function at the end, so we don't
 	 * need to worry about launching another command.
 	 */
-	__scsi_release_buffers(cmd, 0);
+	scsi_release_buffers(cmd);
 	scsi_next_command(cmd);
 	return NULL;
 }
@@ -624,30 +622,10 @@ static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
 	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
 }
 
-static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
-{
-
-	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb);
-
-	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
-
-	if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
-		struct scsi_data_buffer *bidi_sdb =
-			cmd->request->next_rq->special;
-		scsi_free_sgtable(bidi_sdb);
-		kmem_cache_free(scsi_sdb_cache, bidi_sdb);
-		cmd->request->next_rq->special = NULL;
-	}
-
-	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(cmd->prot_sdb);
-}
-
 /*
  * Function:    scsi_release_buffers()
  *
- * Purpose:     Completion processing for block device I/O requests.
+ * Purpose:     Free resources allocate for a scsi_command.
  *
  * Arguments:   cmd	- command that we are bailing.
  *
@@ -658,15 +636,29 @@ static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
  * Notes:       In the event that an upper level driver rejects a
  *		command, we must release resources allocated during
  *		the __init_io() function.  Primarily this would involve
- *		the scatter-gather table, and potentially any bounce
- *		buffers.
+ *		the scatter-gather table.
  */
 void scsi_release_buffers(struct scsi_cmnd *cmd)
 {
-	__scsi_release_buffers(cmd, 1);
+	if (cmd->sdb.table.nents)
+		scsi_free_sgtable(&cmd->sdb);
+
+	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+
+	if (scsi_prot_sg_count(cmd))
+		scsi_free_sgtable(cmd->prot_sdb);
 }
 EXPORT_SYMBOL(scsi_release_buffers);
 
+static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
+{
+	struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
+
+	scsi_free_sgtable(bidi_sdb);
+	kmem_cache_free(scsi_sdb_cache, bidi_sdb);
+	cmd->request->next_rq->special = NULL;
+}
+
 /**
  * __scsi_error_from_host_byte - translate SCSI error code into errno
  * @cmd:	SCSI command (unused)
@@ -799,6 +791,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 			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);

[PATCH 2/2] scsi: remove scsi_end_request

[Christoph Hellwig]

By folding scsi_end_request into its only caller we can significantly clean
up the completion logic.  We can use simple goto labels now to only have
a single place to finish or requeue command there instead of the previous
convoluted logic.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3012700..0bcb7c4 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -511,66 +511,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * Function:    scsi_end_request()
- *
- * Purpose:     Post-processing of completed commands (usually invoked at end
- *		of upper level post-processing and scsi_io_completion).
- *
- * Arguments:   cmd	 - command that is complete.
- *              error    - 0 if I/O indicates success, < 0 for I/O error.
- *              bytes    - number of bytes of completed I/O
- *		requeue  - indicates whether we should requeue leftovers.
- *
- * Lock status: Assumed that lock is not held upon entry.
- *
- * Returns:     cmd if requeue required, NULL otherwise.
- *
- * Notes:       This is called for block device requests in order to
- *              mark some number of sectors as complete.
- * 
- *		We are guaranteeing that the request queue will be goosed
- *		at some point during this call.
- * Notes:	If cmd was requeued, upon return it will be a stale pointer.
- */
-static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
-					  int bytes, int requeue)
-{
-	struct request_queue *q = cmd->device->request_queue;
-	struct request *req = cmd->request;
-
-	/*
-	 * If there are blocks left over at the end, set up the command
-	 * to queue the remainder of them.
-	 */
-	if (blk_end_request(req, error, bytes)) {
-		/* kill remainder if no retrys */
-		if (error && scsi_noretry_cmd(cmd))
-			blk_end_request_all(req, error);
-		else {
-			if (requeue) {
-				/*
-				 * Bleah.  Leftovers again.  Stick the
-				 * leftovers in the front of the
-				 * queue, and goose the queue again.
-				 */
-				scsi_release_buffers(cmd);
-				scsi_requeue_command(q, cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	/*
-	 * This will goose the queue request function at the end, so we don't
-	 * need to worry about launching another command.
-	 */
-	scsi_release_buffers(cmd);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;
@@ -716,16 +656,9 @@ static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
  *
  * Returns:     Nothing
  *
- * Notes:       This function is matched in terms of capabilities to
- *              the function that created the scatter-gather list.
- *              In other words, if there are no bounce buffers
- *              (the normal case for most drivers), we don't need
- *              the logic to deal with cleaning up afterwards.
- *
- *		We must call scsi_end_request().  This will finish off
- *		the specified number of sectors.  If we are done, the
- *		command block will be released and the queue function
- *		will be goosed.  If we are not done then we have to
+ * Notes:       We will finish off the specified number of sectors.  If we
+ *		are done, the command block will be released and the queue
+ *		function will be goosed.  If we are not done then we have to
  *		figure out what to do next:
  *
  *		a) We can call scsi_requeue_command().  The request
@@ -734,7 +667,7 @@ static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
  *		   be used if we made forward progress, or if we want
  *		   to switch from READ(10) to READ(6) for example.
  *
- *		b) We can call scsi_queue_insert().  The request will
+ *		b) We can call __scsi_queue_insert().  The request will
  *		   be put back on the queue and retried using the same
  *		   command as before, possibly after a delay.
  *
@@ -792,6 +725,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 
 			scsi_release_buffers(cmd);
 			scsi_release_bidi_buffers(cmd);
+
 			blk_end_request_all(req, 0);
 
 			scsi_next_command(cmd);
@@ -831,12 +765,25 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	}
 
 	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
+	 * If we finished all bytes in the request we are done now.
 	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
+	if (!blk_end_request(req, error, good_bytes))
+		goto next_command;
+
+	/*
+	 * Kill remainder if no retrys.
+	 */
+	if (error && scsi_noretry_cmd(cmd)) {
+		blk_end_request_all(req, error);
+		goto next_command;
+	}
+
+	/*
+	 * If there had been no error, but we have leftover bytes in the
+	 * requeues just queue the command up again.
+	 */
+	if (result == 0)
+		goto requeue;
 
 	error = __scsi_error_from_host_byte(cmd, result);
 
@@ -958,7 +905,6 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	switch (action) {
 	case ACTION_FAIL:
 		/* Give up and fail the remainder of the request */
-		scsi_release_buffers(cmd);
 		if (!(req->cmd_flags & REQ_QUIET)) {
 			if (description)
 				scmd_printk(KERN_INFO, cmd, "%s\n",
@@ -968,12 +914,11 @@ 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))
-			scsi_requeue_command(q, cmd);
-		else
-			scsi_next_command(cmd);
-		break;
+		if (!blk_end_request_err(req, error))
+			goto next_command;
+		/*FALLTHRU*/
 	case ACTION_REPREP:
+	requeue:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.
 		 */
@@ -989,6 +934,11 @@ 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,

Re: [PATCH 1/2] scsi: explicitly release bidi buffers

[Christoph Hellwig]

Now that LSF is done can I get anyone excited to review these?

On Wed, Mar 12, 2014 at 04:06:06AM -0700, Christoph Hellwig wrote:
> Instead of trying to guess when we have a BIDI buffer in scsi_release_buffers
> add a function to explicitly free the BIDI ressoures in the one place that
> handles them.  This avoids needing a special __scsi_release_buffers for the
> case where we already have freed the request as well.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index debe30a..3012700 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -511,8 +511,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
>  		scsi_run_queue(sdev->request_queue);
>  }
>  
> -static void __scsi_release_buffers(struct scsi_cmnd *, int);
> -
>  /*
>   * Function:    scsi_end_request()
>   *
> @@ -568,7 +566,7 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
>  	 * This will goose the queue request function at the end, so we don't
>  	 * need to worry about launching another command.
>  	 */
> -	__scsi_release_buffers(cmd, 0);
> +	scsi_release_buffers(cmd);
>  	scsi_next_command(cmd);
>  	return NULL;
>  }
> @@ -624,30 +622,10 @@ static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
>  	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
>  }
>  
> -static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
> -{
> -
> -	if (cmd->sdb.table.nents)
> -		scsi_free_sgtable(&cmd->sdb);
> -
> -	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
> -
> -	if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
> -		struct scsi_data_buffer *bidi_sdb =
> -			cmd->request->next_rq->special;
> -		scsi_free_sgtable(bidi_sdb);
> -		kmem_cache_free(scsi_sdb_cache, bidi_sdb);
> -		cmd->request->next_rq->special = NULL;
> -	}
> -
> -	if (scsi_prot_sg_count(cmd))
> -		scsi_free_sgtable(cmd->prot_sdb);
> -}
> -
>  /*
>   * Function:    scsi_release_buffers()
>   *
> - * Purpose:     Completion processing for block device I/O requests.
> + * Purpose:     Free resources allocate for a scsi_command.
>   *
>   * Arguments:   cmd	- command that we are bailing.
>   *
> @@ -658,15 +636,29 @@ static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
>   * Notes:       In the event that an upper level driver rejects a
>   *		command, we must release resources allocated during
>   *		the __init_io() function.  Primarily this would involve
> - *		the scatter-gather table, and potentially any bounce
> - *		buffers.
> + *		the scatter-gather table.
>   */
>  void scsi_release_buffers(struct scsi_cmnd *cmd)
>  {
> -	__scsi_release_buffers(cmd, 1);
> +	if (cmd->sdb.table.nents)
> +		scsi_free_sgtable(&cmd->sdb);
> +
> +	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
> +
> +	if (scsi_prot_sg_count(cmd))
> +		scsi_free_sgtable(cmd->prot_sdb);
>  }
>  EXPORT_SYMBOL(scsi_release_buffers);
>  
> +static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
> +{
> +	struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
> +
> +	scsi_free_sgtable(bidi_sdb);
> +	kmem_cache_free(scsi_sdb_cache, bidi_sdb);
> +	cmd->request->next_rq->special = NULL;
> +}
> +
>  /**
>   * __scsi_error_from_host_byte - translate SCSI error code into errno
>   * @cmd:	SCSI command (unused)
> @@ -799,6 +791,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>  			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);
> --
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