[SCSI] sas_ata: Satisfy libata qc function locking requirements

ata_qc_complete and ata_sas_queuecmd require that the port lock be held
when they are called.  sas_ata doesn't do this, leading to BUG messages
about qc tags newly allocated qc tags already being in use.  This patch
fixes the locking, which should clean up the rest of those messages.

So far I've tested this against an IBM x206m with two SATA disks with no
BUG messages and no other signs of things going wrong, and the machine
finally passed the pounder stress test.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/libsas/sas_ata.c

@@ -92,7 +92,9 @@ static void sas_ata_task_done(struct sas_task *task)
 	struct task_status_struct *stat = &task->task_status;
 	struct ata_task_resp *resp = (struct ata_task_resp *)stat->buf;
 	enum ata_completion_errors ac;
+	unsigned long flags;
 
+	spin_lock_irqsave(dev->sata_dev.ap->lock, flags);
 	if (stat->stat == SAS_PROTO_RESPONSE) {
 		ata_tf_from_fis(resp->ending_fis, &dev->sata_dev.tf);
 		qc->err_mask |= ac_err_mask(dev->sata_dev.tf.command);
@@ -113,6 +115,8 @@ static void sas_ata_task_done(struct sas_task *task)
 	}
 
 	ata_qc_complete(qc);
+	spin_unlock_irqrestore(dev->sata_dev.ap->lock, flags);
+
 	list_del_init(&task->list);
 	sas_free_task(task);
 }

drivers/scsi/libsas/sas_scsi_host.c

@@ -216,8 +216,12 @@ int sas_queuecommand(struct scsi_cmnd *cmd,
 		struct sas_task *task;
 
 		if (dev_is_sata(dev)) {
+			unsigned long flags;
+
+			spin_lock_irqsave(dev->sata_dev.ap->lock, flags);
 			res = ata_sas_queuecmd(cmd, scsi_done,
 					       dev->sata_dev.ap);
+			spin_unlock_irqrestore(dev->sata_dev.ap->lock, flags);
 			goto out;
 		}