The module unload code will wait for a controller to be delete even when
there is no controller and we wait for completion forever to happen.
Thus only wait for the completion when there is a controller which
needs to be removed.

Signed-off-by: Daniel Wagner <dwagner@suse.de>
---
 drivers/nvme/host/fc.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 15dc9dfe88a9..69f7943c5056 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3947,10 +3947,11 @@ static int __init nvme_fc_init_module(void)
 	return ret;
 }
 
-static void
+static bool
 nvme_fc_delete_controllers(struct nvme_fc_rport *rport)
 {
 	struct nvme_fc_ctrl *ctrl;
+	bool cleanup = false;
 
 	spin_lock(&rport->lock);
 	list_for_each_entry(ctrl, &rport->ctrl_list, ctrl_list) {
@@ -3958,21 +3959,28 @@ nvme_fc_delete_controllers(struct nvme_fc_rport *rport)
 			"NVME-FC{%d}: transport unloading: deleting ctrl\n",
 			ctrl->cnum);
 		nvme_delete_ctrl(&ctrl->ctrl);
+		cleanup = true;
 	}
 	spin_unlock(&rport->lock);
+
+	return cleanup;
 }
 
-static void
+static bool
 nvme_fc_cleanup_for_unload(void)
 {
 	struct nvme_fc_lport *lport;
 	struct nvme_fc_rport *rport;
+	bool cleanup = false;
 
 	list_for_each_entry(lport, &nvme_fc_lport_list, port_list) {
 		list_for_each_entry(rport, &lport->endp_list, endp_list) {
-			nvme_fc_delete_controllers(rport);
+			if (nvme_fc_delete_controllers(rport))
+				cleanup = true;
 		}
 	}
+
+	return cleanup;
 }
 
 static void __exit nvme_fc_exit_module(void)
@@ -3982,10 +3990,8 @@ static void __exit nvme_fc_exit_module(void)
 
 	spin_lock_irqsave(&nvme_fc_lock, flags);
 	nvme_fc_waiting_to_unload = true;
-	if (!list_empty(&nvme_fc_lport_list)) {
-		need_cleanup = true;
-		nvme_fc_cleanup_for_unload();
-	}
+	if (!list_empty(&nvme_fc_lport_list))
+		need_cleanup = nvme_fc_cleanup_for_unload();
 	spin_unlock_irqrestore(&nvme_fc_lock, flags);
 	if (need_cleanup) {
 		pr_info("%s: waiting for ctlr deletes\n", __func__);
-- 
2.43.0

On 12/18/23 16:30, Daniel Wagner wrote:
> The module unload code will wait for a controller to be delete even when
> there is no controller and we wait for completion forever to happen.
> Thus only wait for the completion when there is a controller which
> needs to be removed.
> 
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
>   drivers/nvme/host/fc.c | 20 +++++++++++++-------
>   1 file changed, 13 insertions(+), 7 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Ivo Totev, Andrew McDonald,
Werner Knoblich

On Mon, Dec 18, 2023 at 04:30:54PM +0100, Daniel Wagner wrote:
> The module unload code will wait for a controller to be delete even when
> there is no controller and we wait for completion forever to happen.
> Thus only wait for the completion when there is a controller which
> needs to be removed.

This whole code looks fishy to me, and I suspect this patch only papers
over it.  Why do we this wait to start with?  If we've found that out and
documented it, the code really should be using a wait_event variant that
checks for the actual condition (no more controllers), because without
that you might still have a race otherwise.

On Tue, Dec 19, 2023 at 05:35:14AM +0100, Christoph Hellwig wrote:
> On Mon, Dec 18, 2023 at 04:30:54PM +0100, Daniel Wagner wrote:
> > The module unload code will wait for a controller to be delete even when
> > there is no controller and we wait for completion forever to happen.
> > Thus only wait for the completion when there is a controller which
> > needs to be removed.
> 
> This whole code looks fishy to me, and I suspect this patch only papers
> over it.  Why do we this wait to start with?  If we've found that out and
> documented it, the code really should be using a wait_event variant that
> checks for the actual condition (no more controllers), because without
> that you might still have a race otherwise.

The synchronization here does feel off, but Daniel's change looks
correct to the current implementation and is a minimal diff to fix it.
Do you want to see this re-worked with a better wait condition or can we
proceed with this?