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>

4 files changed, 24 insertions, 8 deletions

diff --git a/include/scsi/libfc.h b/include/scsi/libfc.h
index f986ab7ffe6..5c4c1678f7b 100644
--- a/include/scsi/libfc.h
+++ b/include/scsi/libfc.h
@@ -1006,8 +1006,7 @@ void fc_fcp_destroy(struct fc_lport *);
 /*
  * SCSI INTERACTION LAYER
  *****************************/
-int fc_queuecommand(struct scsi_cmnd *,
-		    void (*done)(struct scsi_cmnd *));
+int fc_queuecommand(struct Scsi_Host *, struct scsi_cmnd *);
 int fc_eh_abort(struct scsi_cmnd *);
 int fc_eh_device_reset(struct scsi_cmnd *);
 int fc_eh_host_reset(struct scsi_cmnd *);
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index ae5196aae1a..b81d969ddc6 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -341,8 +341,7 @@ extern int iscsi_eh_abort(struct scsi_cmnd *sc);
 extern int iscsi_eh_recover_target(struct scsi_cmnd *sc);
 extern int iscsi_eh_session_reset(struct scsi_cmnd *sc);
 extern int iscsi_eh_device_reset(struct scsi_cmnd *sc);
-extern int iscsi_queuecommand(struct scsi_cmnd *sc,
-			      void (*done)(struct scsi_cmnd *));
+extern int iscsi_queuecommand(struct Scsi_Host *h, struct scsi_cmnd *sc);
 
 /*
  * iSCSI host helpers.
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 3dec1949f69..90ce527ecf3 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -621,8 +621,7 @@ int sas_set_phy_speed(struct sas_phy *phy,
 int sas_phy_enable(struct sas_phy *phy, int enabled);
 int sas_phy_reset(struct sas_phy *phy, int hard_reset);
 int sas_queue_up(struct sas_task *task);
-extern int sas_queuecommand(struct scsi_cmnd *,
-		     void (*scsi_done)(struct scsi_cmnd *));
+extern int sas_queuecommand(struct Scsi_Host * ,struct scsi_cmnd *);
 extern int sas_target_alloc(struct scsi_target *);
 extern int sas_slave_alloc(struct scsi_device *);
 extern int sas_slave_configure(struct scsi_device *);
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index d0a6a845f20..e7e385842a3 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -127,8 +127,7 @@ struct scsi_host_template {
 	 *
 	 * STATUS: REQUIRED
 	 */
-	int (* queuecommand)(struct scsi_cmnd *,
-			     void (*done)(struct scsi_cmnd *));
+	int (* queuecommand)(struct Scsi_Host *, struct scsi_cmnd *);
 
 	/*
 	 * The transfer functions are used to queue a scsi command to
@@ -505,6 +504,25 @@ struct scsi_host_template {
 };
 
 /*
+ * Temporary #define for host lock push down. Can be removed when all
+ * drivers have been updated to take advantage of unlocked
+ * queuecommand.
+ *
+ */
+#define DEF_SCSI_QCMD(func_name) \
+	int func_name(struct Scsi_Host *shost, struct scsi_cmnd *cmd)	\
+	{								\
+		unsigned long irq_flags;				\
+		int rc;							\
+		spin_lock_irqsave(shost->host_lock, irq_flags);		\
+		scsi_cmd_get_serial(shost, cmd);			\
+		rc = func_name##_lck (cmd, cmd->scsi_done);			\
+		spin_unlock_irqrestore(shost->host_lock, irq_flags);	\
+		return rc;						\
+	}
+
+
+/*
  * shost state: If you alter this, you also need to alter scsi_sysfs.c
  * (for the ascii descriptions) and the state model enforcer:
  * scsi_host_set_state()
@@ -752,6 +770,7 @@ extern struct Scsi_Host *scsi_host_get(struct Scsi_Host *);
 extern void scsi_host_put(struct Scsi_Host *t);
 extern struct Scsi_Host *scsi_host_lookup(unsigned short);
 extern const char *scsi_host_state_name(enum scsi_host_state);
+extern void scsi_cmd_get_serial(struct Scsi_Host *, struct scsi_cmnd *);
 
 extern u64 scsi_calculate_bounce_limit(struct Scsi_Host *);