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>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/scsi/3w-sas.c b/drivers/scsi/3w-sas.c
index 6a95d111d207..13e39e1fdfe2 100644
--- a/drivers/scsi/3w-sas.c
+++ b/drivers/scsi/3w-sas.c
@@ -1501,7 +1501,7 @@ out:
 } /* End twl_scsi_eh_reset() */
 
 /* This is the main scsi queue function to handle scsi opcodes */
-static int twl_scsi_queue(struct scsi_cmnd *SCpnt, void (*done)(struct scsi_cmnd *))
+static int twl_scsi_queue_lck(struct scsi_cmnd *SCpnt, void (*done)(struct scsi_cmnd *))
 {
         int request_id, retval;
         TW_Device_Extension *tw_dev = (TW_Device_Extension *)SCpnt->device->host->hostdata;
@@ -1536,6 +1536,8 @@ out:
         return retval;
 } /* End twl_scsi_queue() */
 
+static DEF_SCSI_QCMD(twl_scsi_queue)
+
 /* This function tells the controller to shut down */
 static void __twl_shutdown(TW_Device_Extension *tw_dev)
 {