scsi: qla2xxx: Fix session cleanup hang

On session cleanup, either an implicit LOGO or an implicit PRLO is used to
flush IOs.  If the flush command hit Queue Full condition, then it is
dropped.  This patch adds retry code to prevent command drop.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Quinn Tran

drivers/scsi/qla2xxx/qla_iocb.c

@@ -3645,23 +3645,22 @@ qla24xx_prlo_iocb(srb_t *sp, struct logio_entry_24xx *logio)
 int
 qla2x00_start_sp(srb_t *sp)
 {
-	int rval;
+	int rval = QLA_SUCCESS;
 	scsi_qla_host_t *vha = sp->vha;
 	struct qla_hw_data *ha = vha->hw;
 	struct qla_qpair *qp = sp->qpair;
 	void *pkt;
 	unsigned long flags;
 
-	rval = QLA_FUNCTION_FAILED;
 	spin_lock_irqsave(qp->qp_lock_ptr, flags);
 	pkt = __qla2x00_alloc_iocbs(sp->qpair, sp);
 	if (!pkt) {
+		rval = EAGAIN;
 		ql_log(ql_log_warn, vha, 0x700c,
 		    "qla2x00_alloc_iocbs failed.\n");
 		goto done;
 	}
 
-	rval = QLA_SUCCESS;
 	switch (sp->type) {
 	case SRB_LOGIN_CMD:
 		IS_FWI2_CAPABLE(ha) ?

drivers/scsi/qla2xxx/qla_os.c

@@ -5204,14 +5204,14 @@ qla2x00_do_work(struct scsi_qla_host *vha)
 	struct qla_work_evt *e, *tmp;
 	unsigned long flags;
 	LIST_HEAD(work);
+	int rc;
 
 	spin_lock_irqsave(&vha->work_lock, flags);
 	list_splice_init(&vha->work_list, &work);
 	spin_unlock_irqrestore(&vha->work_lock, flags);
 
 	list_for_each_entry_safe(e, tmp, &work, list) {
-		list_del_init(&e->list);
-
+		rc = QLA_SUCCESS;
 		switch (e->type) {
 		case QLA_EVT_AEN:
 			fc_host_post_event(vha->host, fc_get_event_number(),
@@ -5225,7 +5225,7 @@ qla2x00_do_work(struct scsi_qla_host *vha)
 			    e->u.logio.data);
 			break;
 		case QLA_EVT_ASYNC_LOGOUT:
-			qla2x00_async_logout(vha, e->u.logio.fcport);
+			rc = qla2x00_async_logout(vha, e->u.logio.fcport);
 			break;
 		case QLA_EVT_ASYNC_LOGOUT_DONE:
 			qla2x00_async_logout_done(vha, e->u.logio.fcport,
@@ -5270,7 +5270,7 @@ qla2x00_do_work(struct scsi_qla_host *vha)
 			qla24xx_do_nack_work(vha, e);
 			break;
 		case QLA_EVT_ASYNC_PRLO:
-			qla2x00_async_prlo(vha, e->u.logio.fcport);
+			rc = qla2x00_async_prlo(vha, e->u.logio.fcport);
 			break;
 		case QLA_EVT_ASYNC_PRLO_DONE:
 			qla2x00_async_prlo_done(vha, e->u.logio.fcport,
@@ -5303,6 +5303,15 @@ qla2x00_do_work(struct scsi_qla_host *vha)
 			    e->u.fcport.fcport, false);
 			break;
 		}
+
+		if (rc == EAGAIN) {
+			/* put 'work' at head of 'vha->work_list' */
+			spin_lock_irqsave(&vha->work_lock, flags);
+			list_splice(&work, &vha->work_list);
+			spin_unlock_irqrestore(&vha->work_lock, flags);
+			break;
+		}
+		list_del_init(&e->list);
 		if (e->flags & QLA_EVT_FLAG_FREE)
 			kfree(e);