[SCSI] libsas: remove ata_port.lock management duties from lldds

Each libsas driver (mvsas, pm8001, and isci) has invented a different
method for managing the ap->lock.  The lock is held by the ata
->queuecommand() path.  mvsas drops it prior to acquiring any internal
locks which allows it to hold its internal lock across calls to
task->task_done().  This capability is important as it is the only way
the driver can flush task->task_done() instances to guarantee that it no
longer has any in-flight references to a domain_device at
->lldd_dev_gone() time.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/libsas/sas_ata.c

@@ -166,23 +166,30 @@ qc_already_gone:
 
 static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
 {
-	int res;
+	unsigned long flags;
 	struct sas_task *task;
-	struct domain_device *dev = qc->ap->private_data;
+	struct scatterlist *sg;
+	int ret = AC_ERR_SYSTEM;
+	unsigned int si, xfer = 0;
+	struct ata_port *ap = qc->ap;
+	struct domain_device *dev = ap->private_data;
 	struct sas_ha_struct *sas_ha = dev->port->ha;
 	struct Scsi_Host *host = sas_ha->core.shost;
 	struct sas_internal *i = to_sas_internal(host->transportt);
-	struct scatterlist *sg;
-	unsigned int xfer = 0;
-	unsigned int si;
+
+	/* TODO: audit callers to ensure they are ready for qc_issue to
+	 * unconditionally re-enable interrupts
+	 */
+	local_irq_save(flags);
+	spin_unlock(ap->lock);
 
 	/* If the device fell off, no sense in issuing commands */
 	if (dev->gone)
-		return AC_ERR_SYSTEM;
+		goto out;
 
 	task = sas_alloc_task(GFP_ATOMIC);
 	if (!task)
-		return AC_ERR_SYSTEM;
+		goto out;
 	task->dev = dev;
 	task->task_proto = SAS_PROTOCOL_STP;
 	task->task_done = sas_ata_task_done;
@@ -227,21 +234,24 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
 		ASSIGN_SAS_TASK(qc->scsicmd, task);
 
 	if (sas_ha->lldd_max_execute_num < 2)
-		res = i->dft->lldd_execute_task(task, 1, GFP_ATOMIC);
+		ret = i->dft->lldd_execute_task(task, 1, GFP_ATOMIC);
 	else
-		res = sas_queue_up(task);
+		ret = sas_queue_up(task);
 
 	/* Examine */
-	if (res) {
-		SAS_DPRINTK("lldd_execute_task returned: %d\n", res);
+	if (ret) {
+		SAS_DPRINTK("lldd_execute_task returned: %d\n", ret);
 
 		if (qc->scsicmd)
 			ASSIGN_SAS_TASK(qc->scsicmd, NULL);
 		sas_free_task(task);
-		return AC_ERR_SYSTEM;
+		ret = AC_ERR_SYSTEM;
 	}
 
-	return 0;
+ out:
+	spin_lock(ap->lock);
+	local_irq_restore(flags);
+	return ret;
 }
 
 static bool sas_ata_qc_fill_rtf(struct ata_queued_cmd *qc)

drivers/scsi/libsas/sas_scsi_host.c

@@ -198,11 +198,9 @@ int sas_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 	}
 
 	if (dev_is_sata(dev)) {
-		unsigned long flags;
-
-		spin_lock_irqsave(dev->sata_dev.ap->lock, flags);
+		spin_lock_irq(dev->sata_dev.ap->lock);
 		res = ata_sas_queuecmd(cmd, dev->sata_dev.ap);
-		spin_unlock_irqrestore(dev->sata_dev.ap->lock, flags);
+		spin_unlock_irq(dev->sata_dev.ap->lock);
 		return res;
 	}