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/initio.c b/drivers/scsi/initio.c
index 108797761b95..9627d062e16b 100644
--- a/drivers/scsi/initio.c
+++ b/drivers/scsi/initio.c
@@ -2639,7 +2639,7 @@ static void initio_build_scb(struct initio_host * host, struct scsi_ctrl_blk * c
  *      will cause the mid layer to call us again later with the command)
  */
 
-static int i91u_queuecommand(struct scsi_cmnd *cmd,
+static int i91u_queuecommand_lck(struct scsi_cmnd *cmd,
                 void (*done)(struct scsi_cmnd *))
 {
         struct initio_host *host = (struct initio_host *) cmd->device->host->hostdata;
@@ -2656,6 +2656,8 @@ static int i91u_queuecommand(struct scsi_cmnd *cmd,
         return 0;
 }
 
+static DEF_SCSI_QCMD(i91u_queuecommand)
+
 /**
  *      i91u_bus_reset          -       reset the SCSI bus
  *      @cmnd: Command block we want to trigger the reset for