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/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 67f78a470f5f..041958453e2a 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -713,7 +713,7 @@ static inline u16 lun_from_dev(struct scsi_device *dev)
  * @cmd:        struct scsi_cmnd to be executed
  * @done:       Callback function to be called when cmd is completed
 */
-static int ibmvscsi_queuecommand(struct scsi_cmnd *cmnd,
+static int ibmvscsi_queuecommand_lck(struct scsi_cmnd *cmnd,
                                  void (*done) (struct scsi_cmnd *))
 {
         struct srp_cmd *srp_cmd;
@@ -766,6 +766,8 @@ static int ibmvscsi_queuecommand(struct scsi_cmnd *cmnd,
         return ibmvscsi_send_srp_event(evt_struct, hostdata, 0);
 }
 
+static DEF_SCSI_QCMD(ibmvscsi_queuecommand)
+
 /* ------------------------------------------------------------
  * Routines for driver initialization
  */