SCSI host lock push-down

Move the mid-layer's ->queuecommand() invocation from being locked
with the host lock to being unlocked to facilitate speeding up the
critical path for drivers who don't need this lock taken anyway.

The patch below presents a simple SCSI host lock push-down as an
equivalent transformation.  No locking or other behavior should change
with this patch.  All existing bugs and locking orders are preserved.

Additionally, add one parameter to queuecommand,
	struct Scsi_Host *
and remove one parameter from queuecommand,
	void (*done)(struct scsi_cmnd *)

Scsi_Host* is a convenient pointer that most host drivers need anyway,
and 'done' is redundant to struct scsi_cmnd->scsi_done.

Minimal code disturbance was attempted with this change.  Most drivers
needed only two one-line modifications for their host lock push-down.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Acked-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 18 insertions, 14 deletions

diff --git a/drivers/scsi/arm/acornscsi.c b/drivers/scsi/arm/acornscsi.c
index 918ccf8..ec16672 100644
--- a/drivers/scsi/arm/acornscsi.c
+++ b/drivers/scsi/arm/acornscsi.c
@@ -2511,7 +2511,7 @@ acornscsi_intr(int irq, void *dev_id)
  *	      done - function called on completion, with pointer to command descriptor
  * Returns  : 0, or < 0 on error.
  */
-int acornscsi_queuecmd(struct scsi_cmnd *SCpnt,
+static int acornscsi_queuecmd_lck(struct scsi_cmnd *SCpnt,
 		       void (*done)(struct scsi_cmnd *))
 {
     AS_Host *host = (AS_Host *)SCpnt->device->host->hostdata;
@@ -2561,6 +2561,8 @@ int acornscsi_queuecmd(struct scsi_cmnd *SCpnt,
     return 0;
 }
 
+DEF_SCSI_QCMD(acornscsi_queuecmd)
+
 /*
  * Prototype: void acornscsi_reportstatus(struct scsi_cmnd **SCpntp1, struct scsi_cmnd **SCpntp2, int result)
  * Purpose  : pass a result to *SCpntp1, and check if *SCpntp1 = *SCpntp2
diff --git a/drivers/scsi/arm/fas216.c b/drivers/scsi/arm/fas216.c
index 9e71ac6..2b2ce21 100644
--- a/drivers/scsi/arm/fas216.c
+++ b/drivers/scsi/arm/fas216.c
@@ -2198,7 +2198,7 @@ no_command:
  * Returns: 0 on success, else error.
  * Notes: io_request_lock is held, interrupts are disabled.
  */
-int fas216_queue_command(struct scsi_cmnd *SCpnt,
+static int fas216_queue_command_lck(struct scsi_cmnd *SCpnt,
 			 void (*done)(struct scsi_cmnd *))
 {
 	FAS216_Info *info = (FAS216_Info *)SCpnt->device->host->hostdata;
@@ -2240,6 +2240,8 @@ int fas216_queue_command(struct scsi_cmnd *SCpnt,
 	return result;
 }
 
+DEF_SCSI_QCMD(fas216_queue_command)
+
 /**
  * fas216_internal_done - trigger restart of a waiting thread in fas216_noqueue_command
  * @SCpnt: Command to wake
@@ -2263,7 +2265,7 @@ static void fas216_internal_done(struct scsi_cmnd *SCpnt)
  * Returns: scsi result code.
  * Notes: io_request_lock is held, interrupts are disabled.
  */
-int fas216_noqueue_command(struct scsi_cmnd *SCpnt,
+static int fas216_noqueue_command_lck(struct scsi_cmnd *SCpnt,
 			   void (*done)(struct scsi_cmnd *))
 {
 	FAS216_Info *info = (FAS216_Info *)SCpnt->device->host->hostdata;
@@ -2277,7 +2279,7 @@ int fas216_noqueue_command(struct scsi_cmnd *SCpnt,
 	BUG_ON(info->scsi.irq != NO_IRQ);
 
 	info->internal_done = 0;
-	fas216_queue_command(SCpnt, fas216_internal_done);
+	fas216_queue_command_lck(SCpnt, fas216_internal_done);
 
 	/*
 	 * This wastes time, since we can't return until the command is
@@ -2310,6 +2312,8 @@ int fas216_noqueue_command(struct scsi_cmnd *SCpnt,
 	return 0;
 }
 
+DEF_SCSI_QCMD(fas216_noqueue_command)
+
 /*
  * Error handler timeout function.  Indicate that we timed out,
  * and wake up any error handler process so it can continue.
diff --git a/drivers/scsi/arm/fas216.h b/drivers/scsi/arm/fas216.h
index b65f4cf..377cfb7 100644
--- a/drivers/scsi/arm/fas216.h
+++ b/drivers/scsi/arm/fas216.h
@@ -331,23 +331,21 @@ extern int fas216_init (struct Scsi_Host *instance);
  */
 extern int fas216_add (struct Scsi_Host *instance, struct device *dev);
 
-/* Function: int fas216_queue_command(struct scsi_cmnd *SCpnt, void (*done)(struct scsi_cmnd *))
+/* Function: int fas216_queue_command(struct Scsi_Host *h, struct scsi_cmnd *SCpnt)
  * Purpose : queue a command for adapter to process.
- * Params  : SCpnt - Command to queue
- *	     done  - done function to call once command is complete
+ * Params  : h - host adapter
+ *	   : SCpnt - Command to queue
  * Returns : 0 - success, else error
  */
-extern int fas216_queue_command(struct scsi_cmnd *,
-				void (*done)(struct scsi_cmnd *));
+extern int fas216_queue_command(struct Scsi_Host *h, struct scsi_cmnd *SCpnt);
 
-/* Function: int fas216_noqueue_command(istruct scsi_cmnd *SCpnt, void (*done)(struct scsi_cmnd *))
+/* Function: int fas216_noqueue_command(struct Scsi_Host *h, struct scsi_cmnd *SCpnt)
  * Purpose : queue a command for adapter to process, and process it to completion.
- * Params  : SCpnt - Command to queue
- *	     done  - done function to call once command is complete
+ * Params  : h - host adapter
+ *	   : SCpnt - Command to queue
  * Returns : 0 - success, else error
  */
-extern int fas216_noqueue_command(struct scsi_cmnd *,
-				  void (*done)(struct scsi_cmnd *));
+extern int fas216_noqueue_command(struct Scsi_Host *, struct scsi_cmnd *)
 
 /* Function: irqreturn_t fas216_intr (FAS216_Info *info)
  * Purpose : handle interrupts from the interface to progress a command