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/fd_mcs.c b/drivers/scsi/fd_mcs.c
index 2ad95aa..a2c6135 100644
--- a/drivers/scsi/fd_mcs.c
+++ b/drivers/scsi/fd_mcs.c
@@ -1072,7 +1072,7 @@ static int fd_mcs_release(struct Scsi_Host *shpnt)
 	return 0;
 }
 
-static int fd_mcs_queue(Scsi_Cmnd * SCpnt, void (*done) (Scsi_Cmnd *))
+static int fd_mcs_queue_lck(Scsi_Cmnd * SCpnt, void (*done) (Scsi_Cmnd *))
 {
 	struct Scsi_Host *shpnt = SCpnt->device->host;
 
@@ -1122,6 +1122,8 @@ static int fd_mcs_queue(Scsi_Cmnd * SCpnt, void (*done) (Scsi_Cmnd *))
 	return 0;
 }
 
+static DEF_SCSI_QCMD(fd_mcs_queue)
+
 #if DEBUG_ABORT || DEBUG_RESET
 static void fd_mcs_print_info(Scsi_Cmnd * SCpnt)
 {