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, 4 insertions, 3 deletions

diff --git a/drivers/scsi/megaraid/megaraid_mbox.c b/drivers/scsi/megaraid/megaraid_mbox.c
index a7810a106b3..5708cb27d07 100644
--- a/drivers/scsi/megaraid/megaraid_mbox.c
+++ b/drivers/scsi/megaraid/megaraid_mbox.c
@@ -113,8 +113,7 @@ static int megaraid_mbox_fire_sync_cmd(adapter_t *);
 static void megaraid_mbox_display_scb(adapter_t *, scb_t *);
 static void megaraid_mbox_setup_device_map(adapter_t *);
 
-static int megaraid_queue_command(struct scsi_cmnd *,
-                void (*)(struct scsi_cmnd *));
+static int megaraid_queue_command(struct Scsi_Host *, struct scsi_cmnd *);
 static scb_t *megaraid_mbox_build_cmd(adapter_t *, struct scsi_cmnd *, int *);
 static void megaraid_mbox_runpendq(adapter_t *, scb_t *);
 static void megaraid_mbox_prepare_pthru(adapter_t *, scb_t *,
@@ -1484,7 +1483,7 @@ mbox_post_cmd(adapter_t *adapter, scb_t *scb)
  * Queue entry point for mailbox based controllers.
  */
 static int
-megaraid_queue_command(struct scsi_cmnd *scp, void (*done)(struct scsi_cmnd *))
+megaraid_queue_command_lck(struct scsi_cmnd *scp, void (*done)(struct scsi_cmnd *))
 {
         adapter_t       *adapter;
         scb_t           *scb;
@@ -1513,6 +1512,8 @@ megaraid_queue_command(struct scsi_cmnd *scp, void (*done)(struct scsi_cmnd *))
         return if_busy;
 }
 
+static DEF_SCSI_QCMD(megaraid_queue_command)
+
 /**
  * megaraid_mbox_build_cmd - transform the mid-layer scsi commands
  * @adapter     : controller's soft state