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/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index 50286d8..6bd2dbc 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -76,7 +76,7 @@ static void zfcp_scsi_command_fail(struct scsi_cmnd *scpnt, int result)
 	scpnt->scsi_done(scpnt);
 }
 
-static int zfcp_scsi_queuecommand(struct scsi_cmnd *scpnt,
+static int zfcp_scsi_queuecommand_lck(struct scsi_cmnd *scpnt,
 				  void (*done) (struct scsi_cmnd *))
 {
 	struct zfcp_scsi_dev *zfcp_sdev = sdev_to_zfcp(scpnt->device);
@@ -127,6 +127,8 @@ static int zfcp_scsi_queuecommand(struct scsi_cmnd *scpnt,
 	return ret;
 }
 
+static DEF_SCSI_QCMD(zfcp_scsi_queuecommand)
+
 static int zfcp_scsi_slave_alloc(struct scsi_device *sdev)
 {
 	struct fc_rport *rport = starget_to_rport(scsi_target(sdev));