[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/isci/request.c

@@ -3796,8 +3796,7 @@ int isci_request_execute(struct isci_host *ihost, struct isci_remote_device *ide
 		/* Cause this task to be scheduled in the SCSI error
 		 * handler thread.
 		 */
-		isci_execpath_callback(ihost, task,
-				       sas_task_abort);
+		sas_task_abort(task);
 
 		/* Change the status, since we are holding
 		 * the I/O until it is managed by the SCSI

drivers/scsi/isci/task.c

@@ -96,8 +96,7 @@ static void isci_task_refuse(struct isci_host *ihost, struct sas_task *task,
 			__func__, task, response, status);
 
 		task->lldd_task = NULL;
-
-		isci_execpath_callback(ihost, task, task->task_done);
+		task->task_done(task);
 		break;
 
 	case isci_perform_aborted_io_completion:
@@ -117,8 +116,7 @@ static void isci_task_refuse(struct isci_host *ihost, struct sas_task *task,
 			"%s: Error - task = %p, response=%d, "
 			"status=%d\n",
 			__func__, task, response, status);
-
-		isci_execpath_callback(ihost, task, sas_task_abort);
+		sas_task_abort(task);
 		break;
 
 	default:

drivers/scsi/isci/task.h

@@ -321,40 +321,4 @@ isci_task_set_completion_status(
 	return task_notification_selection;
 
 }
-/**
-* isci_execpath_callback() - This function is called from the task
-* execute path when the task needs to callback libsas about the submit-time
-* task failure.  The callback occurs either through the task's done function
-* or through sas_task_abort.  In the case of regular non-discovery SATA/STP I/O
-* requests, libsas takes the host lock before calling execute task.  Therefore
-* in this situation the host lock must be managed before calling the func.
-*
-* @ihost: This parameter is the controller to which the I/O request was sent.
-* @task: This parameter is the I/O request.
-* @func: This parameter is the function to call in the correct context.
-* @status: This parameter is the status code for the completed task.
-*
-*/
-static inline void isci_execpath_callback(struct isci_host *ihost,
-					  struct sas_task  *task,
-					  void (*func)(struct sas_task *))
-{
-	struct domain_device *dev = task->dev;
-
-	if (dev_is_sata(dev) && task->uldd_task) {
-		unsigned long flags;
-
-		/* Since we are still in the submit path, and since
-		 * libsas takes the host lock on behalf of SATA
-		 * devices before I/O starts (in the non-discovery case),
-		 * we need to unlock before we can call the callback function.
-		 */
-		raw_local_irq_save(flags);
-		spin_unlock(dev->sata_dev.ap->lock);
-		func(task);
-		spin_lock(dev->sata_dev.ap->lock);
-		raw_local_irq_restore(flags);
-	} else
-		func(task);
-}
 #endif /* !defined(_SCI_TASK_H_) */

drivers/scsi/libsas/sas_ata.c

@@ -166,23 +166,30 @@ static void sas_ata_task_done(struct sas_task *task)
 
 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;
 	}
 

drivers/scsi/mvsas/mv_sas.c

@@ -893,9 +893,6 @@ static int mvs_task_exec(struct sas_task *task, const int num, gfp_t gfp_flags,
 
 	mvi = ((struct mvs_device *)task->dev->lldd_dev)->mvi_info;
 
-	if ((dev->dev_type == SATA_DEV) && (dev->sata_dev.ap != NULL))
-		spin_unlock_irq(dev->sata_dev.ap->lock);
-
 	spin_lock_irqsave(&mvi->lock, flags);
 	rc = mvs_task_prep(task, mvi, is_tmf, tmf, &pass);
 	if (rc)
@@ -906,9 +903,6 @@ static int mvs_task_exec(struct sas_task *task, const int num, gfp_t gfp_flags,
 				(MVS_CHIP_SLOT_SZ - 1));
 	spin_unlock_irqrestore(&mvi->lock, flags);
 
-	if ((dev->dev_type == SATA_DEV) && (dev->sata_dev.ap != NULL))
-		spin_lock_irq(dev->sata_dev.ap->lock);
-
 	return rc;
 }
 

drivers/scsi/pm8001/pm8001_sas.c

@@ -364,7 +364,7 @@ static int pm8001_task_exec(struct sas_task *task, const int num,
 	struct pm8001_ccb_info *ccb;
 	u32 tag = 0xdeadbeef, rc, n_elem = 0;
 	u32 n = num;
-	unsigned long flags = 0, flags_libsas = 0;
+	unsigned long flags = 0;
 
 	if (!dev->port) {
 		struct task_status_struct *tsm = &t->task_status;
@@ -388,11 +388,7 @@ static int pm8001_task_exec(struct sas_task *task, const int num,
 				ts->stat = SAS_PHY_DOWN;
 
 				spin_unlock_irqrestore(&pm8001_ha->lock, flags);
-				spin_unlock_irqrestore(dev->sata_dev.ap->lock,
-						flags_libsas);
 				t->task_done(t);
-				spin_lock_irqsave(dev->sata_dev.ap->lock,
-					flags_libsas);
 				spin_lock_irqsave(&pm8001_ha->lock, flags);
 				if (n > 1)
 					t = list_entry(t->list.next,