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/sym53c8xx_2/sym_glue.c b/drivers/scsi/sym53c8xx_2/sym_glue.c
index 8b955b534a36..6b97ded9d45d 100644
--- a/drivers/scsi/sym53c8xx_2/sym_glue.c
+++ b/drivers/scsi/sym53c8xx_2/sym_glue.c
@@ -505,7 +505,7 @@ void sym_log_bus_error(struct Scsi_Host *shost)
  * queuecommand method.  Entered with the host adapter lock held and
  * interrupts disabled.
  */
-static int sym53c8xx_queue_command(struct scsi_cmnd *cmd,
+static int sym53c8xx_queue_command_lck(struct scsi_cmnd *cmd,
                                         void (*done)(struct scsi_cmnd *))
 {
         struct sym_hcb *np = SYM_SOFTC_PTR(cmd);
@@ -536,6 +536,8 @@ static int sym53c8xx_queue_command(struct scsi_cmnd *cmd,
         return 0;
 }
 
+static DEF_SCSI_QCMD(sym53c8xx_queue_command)
+
 /*
  *  Linux entry point of the interrupt handler.
  */