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, 2 deletions

diff --git a/drivers/scsi/ibmmca.c b/drivers/scsi/ibmmca.c
index 9a4b69d4f4eb..67fc8ffd52e6 100644
--- a/drivers/scsi/ibmmca.c
+++ b/drivers/scsi/ibmmca.c
@@ -39,7 +39,7 @@
 #include <scsi/scsi_host.h>
 
 /* Common forward declarations for all Linux-versions: */
-static int ibmmca_queuecommand (Scsi_Cmnd *, void (*done) (Scsi_Cmnd *));
+static int ibmmca_queuecommand (struct Scsi_Host *, struct scsi_cmnd *);
 static int ibmmca_abort (Scsi_Cmnd *);
 static int ibmmca_host_reset (Scsi_Cmnd *);
 static int ibmmca_biosparam (struct scsi_device *, struct block_device *, sector_t, int *);
@@ -1691,7 +1691,7 @@ static int __devexit ibmmca_remove(struct device *dev)
 }
 
 /* The following routine is the SCSI command queue for the midlevel driver */
-static int ibmmca_queuecommand(Scsi_Cmnd * cmd, void (*done) (Scsi_Cmnd *))
+static int ibmmca_queuecommand_lck(Scsi_Cmnd * cmd, void (*done) (Scsi_Cmnd *))
 {
         unsigned int ldn;
         unsigned int scsi_cmd;
@@ -1996,6 +1996,8 @@ static int ibmmca_queuecommand(Scsi_Cmnd * cmd, void (*done) (Scsi_Cmnd *))
         return 0;
 }
 
+static DEF_SCSI_QCMD(ibmmca_queuecommand)
+
 static int __ibmmca_abort(Scsi_Cmnd * cmd)
 {
         /* Abort does not work, as the adapter never generates an interrupt on