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, 3 deletions

diff --git a/drivers/scsi/bfa/bfad_im.c b/drivers/scsi/bfa/bfad_im.c
index 8daa716739d1..8ca967dee66d 100644
--- a/drivers/scsi/bfa/bfad_im.c
+++ b/drivers/scsi/bfa/bfad_im.c
@@ -30,8 +30,7 @@ DEFINE_IDR(bfad_im_port_index);
 struct scsi_transport_template *bfad_im_scsi_transport_template;
 struct scsi_transport_template *bfad_im_scsi_vport_transport_template;
 static void bfad_im_itnim_work_handler(struct work_struct *work);
-static int bfad_im_queuecommand(struct scsi_cmnd *cmnd,
-                                void (*done)(struct scsi_cmnd *));
+static int bfad_im_queuecommand(struct Scsi_Host *h, struct scsi_cmnd *cmnd);
 static int bfad_im_slave_alloc(struct scsi_device *sdev);
 static void bfad_im_fc_rport_add(struct bfad_im_port_s  *im_port,
                                 struct bfad_itnim_s *itnim);
@@ -1120,7 +1119,7 @@ bfad_im_itnim_work_handler(struct work_struct *work)
  * Scsi_Host template entry, queue a SCSI command to the BFAD.
  */
 static int
-bfad_im_queuecommand(struct scsi_cmnd *cmnd, void (*done) (struct scsi_cmnd *))
+bfad_im_queuecommand_lck(struct scsi_cmnd *cmnd, void (*done) (struct scsi_cmnd *))
 {
         struct bfad_im_port_s *im_port =
                 (struct bfad_im_port_s *) cmnd->device->host->hostdata[0];
@@ -1187,6 +1186,8 @@ out_fail_cmd:
         return 0;
 }
 
+static DEF_SCSI_QCMD(bfad_im_queuecommand)
+
 void
 bfad_os_rport_online_wait(struct bfad_s *bfad)
 {