[PATCH v2 14/14] nvme-fc: Hold inflight requests while in FENCING state

[Mohamed Khalfella <mkhalfella@purestorage.com>]

While in FENCING state aborted inflight IOs should be held until fencing
is done. Update nvme_fc_fcpio_done() to not complete aborted requests or
requests with transport errors. These held requests will be canceled in
nvme_fc_delete_association() after fencing is done. nvme_fc_fcpio_done()
avoids racing with canceling aborted requests by making sure we complete
successful requests before waking up the waiting thread.

Signed-off-by: Mohamed Khalfella <mkhalfella@purestorage.com>
---
 drivers/nvme/host/fc.c | 61 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 51 insertions(+), 10 deletions(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 3a01aeb39081..122ebd7085b1 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -173,7 +173,7 @@ struct nvme_fc_ctrl {
 
 	struct kref		ref;
 	unsigned long		flags;
-	u32			iocnt;
+	atomic_t		iocnt;
 	wait_queue_head_t	ioabort_wait;
 
 	struct nvme_fc_fcp_op	aen_ops[NVME_NR_AEN_COMMANDS];
@@ -1822,7 +1822,7 @@ __nvme_fc_abort_op(struct nvme_fc_ctrl *ctrl, struct nvme_fc_fcp_op *op)
 		atomic_set(&op->state, opstate);
 	else if (test_bit(FCCTRL_TERMIO, &ctrl->flags)) {
 		op->flags |= FCOP_FLAGS_TERMIO;
-		ctrl->iocnt++;
+		atomic_inc(&ctrl->iocnt);
 	}
 	spin_unlock_irqrestore(&ctrl->lock, flags);
 
@@ -1852,20 +1852,29 @@ nvme_fc_abort_aen_ops(struct nvme_fc_ctrl *ctrl)
 }
 
 static inline void
+__nvme_fc_fcpop_count_one_down(struct nvme_fc_ctrl *ctrl)
+{
+	if (atomic_dec_return(&ctrl->iocnt) == 0)
+		wake_up(&ctrl->ioabort_wait);
+}
+
+static inline bool
 __nvme_fc_fcpop_chk_teardowns(struct nvme_fc_ctrl *ctrl,
 		struct nvme_fc_fcp_op *op, int opstate)
 {
 	unsigned long flags;
+	bool ret = false;
 
 	if (opstate == FCPOP_STATE_ABORTED) {
 		spin_lock_irqsave(&ctrl->lock, flags);
 		if (test_bit(FCCTRL_TERMIO, &ctrl->flags) &&
 		    op->flags & FCOP_FLAGS_TERMIO) {
-			if (!--ctrl->iocnt)
-				wake_up(&ctrl->ioabort_wait);
+			ret = true;
 		}
 		spin_unlock_irqrestore(&ctrl->lock, flags);
 	}
+
+	return ret;
 }
 
 static void nvme_fc_fenced_work(struct work_struct *work)
@@ -1973,7 +1982,8 @@ nvme_fc_fcpio_done(struct nvmefc_fcp_req *req)
 	struct nvme_command *sqe = &op->cmd_iu.sqe;
 	__le16 status = cpu_to_le16(NVME_SC_SUCCESS << 1);
 	union nvme_result result;
-	bool terminate_assoc = true;
+	bool op_term, terminate_assoc = true;
+	enum nvme_ctrl_state state;
 	int opstate;
 
 	/*
@@ -2106,16 +2116,38 @@ nvme_fc_fcpio_done(struct nvmefc_fcp_req *req)
 done:
 	if (op->flags & FCOP_FLAGS_AEN) {
 		nvme_complete_async_event(&queue->ctrl->ctrl, status, &result);
-		__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate);
+		if (__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate))
+			__nvme_fc_fcpop_count_one_down(ctrl);
 		atomic_set(&op->state, FCPOP_STATE_IDLE);
 		op->flags = FCOP_FLAGS_AEN;	/* clear other flags */
 		nvme_fc_ctrl_put(ctrl);
 		goto check_error;
 	}
 
-	__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate);
+	/*
+	 * We can not access op after the request is completed because it can
+	 * be reused immediately. At the same time we want to wakeup the thread
+	 * waiting for ongoing IOs _after_ requests are completed. This is
+	 * necessary because that thread will start canceling inflight IOs
+	 * and we want to avoid request completion racing with cancellation.
+	 */
+	op_term = __nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate);
+
+	/*
+	 * If we are going to terminate associations and the controller is
+	 * LIVE or FENCING, then do not complete this request now. Let error
+	 * recovery cancel this request when it is safe to do so.
+	 */
+	state = nvme_ctrl_state(&ctrl->ctrl);
+	if (terminate_assoc &&
+	    (state == NVME_CTRL_LIVE || state == NVME_CTRL_FENCING))
+		goto check_op_term;
+
 	if (!nvme_try_complete_req(rq, status, result))
 		nvme_fc_complete_rq(rq);
+check_op_term:
+	if (op_term)
+		__nvme_fc_fcpop_count_one_down(ctrl);
 
 check_error:
 	if (terminate_assoc)
@@ -2754,7 +2786,8 @@ nvme_fc_start_fcp_op(struct nvme_fc_ctrl *ctrl, struct nvme_fc_queue *queue,
 		 * cmd with the csn was supposed to arrive.
 		 */
 		opstate = atomic_xchg(&op->state, FCPOP_STATE_COMPLETE);
-		__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate);
+		if (__nvme_fc_fcpop_chk_teardowns(ctrl, op, opstate))
+			__nvme_fc_fcpop_count_one_down(ctrl);
 
 		if (!(op->flags & FCOP_FLAGS_AEN)) {
 			nvme_fc_unmap_data(ctrl, op->rq, op);
@@ -3223,7 +3256,7 @@ nvme_fc_delete_association(struct nvme_fc_ctrl *ctrl)
 
 	spin_lock_irqsave(&ctrl->lock, flags);
 	set_bit(FCCTRL_TERMIO, &ctrl->flags);
-	ctrl->iocnt = 0;
+	atomic_set(&ctrl->iocnt, 0);
 	spin_unlock_irqrestore(&ctrl->lock, flags);
 
 	__nvme_fc_abort_outstanding_ios(ctrl, false);
@@ -3232,11 +3265,19 @@ nvme_fc_delete_association(struct nvme_fc_ctrl *ctrl)
 	nvme_fc_abort_aen_ops(ctrl);
 
 	/* wait for all io that had to be aborted */
+	wait_event(ctrl->ioabort_wait, atomic_read(&ctrl->iocnt) == 0);
 	spin_lock_irq(&ctrl->lock);
-	wait_event_lock_irq(ctrl->ioabort_wait, ctrl->iocnt == 0, ctrl->lock);
 	clear_bit(FCCTRL_TERMIO, &ctrl->flags);
 	spin_unlock_irq(&ctrl->lock);
 
+	/*
+	 * At this point all inflight requests have been successfully
+	 * aborted. Now it is safe to cancel all requests we decided
+	 * not to complete in nvme_fc_fcpio_done().
+	 */
+	nvme_cancel_tagset(&ctrl->ctrl);
+	nvme_cancel_admin_tagset(&ctrl->ctrl);
+
 	nvme_fc_term_aen_ops(ctrl);
 
 	/*
-- 
2.52.0