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/gdth.c b/drivers/scsi/gdth.c
index 841101846b88..76365700e2d5 100644
--- a/drivers/scsi/gdth.c
+++ b/drivers/scsi/gdth.c
@@ -185,7 +185,7 @@ static long gdth_unlocked_ioctl(struct file *filep, unsigned int cmd,
                                 unsigned long arg);
 
 static void gdth_flush(gdth_ha_str *ha);
-static int gdth_queuecommand(Scsi_Cmnd *scp,void (*done)(Scsi_Cmnd *));
+static int gdth_queuecommand(struct Scsi_Host *h, struct scsi_cmnd *cmd);
 static int __gdth_queuecommand(gdth_ha_str *ha, struct scsi_cmnd *scp,
                                 struct gdth_cmndinfo *cmndinfo);
 static void gdth_scsi_done(struct scsi_cmnd *scp);
@@ -4004,7 +4004,7 @@ static int gdth_bios_param(struct scsi_device *sdev,struct block_device *bdev,se
 }
 
 
-static int gdth_queuecommand(struct scsi_cmnd *scp,
+static int gdth_queuecommand_lck(struct scsi_cmnd *scp,
                                 void (*done)(struct scsi_cmnd *))
 {
     gdth_ha_str *ha = shost_priv(scp->device->host);
@@ -4022,6 +4022,8 @@ static int gdth_queuecommand(struct scsi_cmnd *scp,
     return __gdth_queuecommand(ha, scp, cmndinfo);
 }
 
+static DEF_SCSI_QCMD(gdth_queuecommand)
+
 static int __gdth_queuecommand(gdth_ha_str *ha, struct scsi_cmnd *scp,
                                 struct gdth_cmndinfo *cmndinfo)
 {