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/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
index f4cd846abf6d..0d48fb4d1044 100644
--- a/drivers/scsi/qla4xxx/ql4_os.c
+++ b/drivers/scsi/qla4xxx/ql4_os.c
@@ -79,8 +79,7 @@ static enum blk_eh_timer_return qla4xxx_eh_cmd_timed_out(struct scsi_cmnd *sc);
 /*
  * SCSI host template entry points
  */
-static int qla4xxx_queuecommand(struct scsi_cmnd *cmd,
-                                void (*done) (struct scsi_cmnd *));
+static int qla4xxx_queuecommand(struct Scsi_Host *h, struct scsi_cmnd *cmd);
 static int qla4xxx_eh_abort(struct scsi_cmnd *cmd);
 static int qla4xxx_eh_device_reset(struct scsi_cmnd *cmd);
 static int qla4xxx_eh_target_reset(struct scsi_cmnd *cmd);
@@ -464,7 +463,7 @@ void qla4xxx_srb_compl(struct kref *ref)
  * completion handling).   Unfortunely, it sometimes calls the scheduler
  * in interrupt context which is a big NO! NO!.
  **/
-static int qla4xxx_queuecommand(struct scsi_cmnd *cmd,
+static int qla4xxx_queuecommand_lck(struct scsi_cmnd *cmd,
                                 void (*done)(struct scsi_cmnd *))
 {
         struct scsi_qla_host *ha = to_qla_host(cmd->device->host);
@@ -538,6 +537,8 @@ qc_fail_command:
         return 0;
 }
 
+static DEF_SCSI_QCMD(qla4xxx_queuecommand)
+
 /**
  * qla4xxx_mem_free - frees memory allocated to adapter
  * @ha: Pointer to host adapter structure.