Patch "nvme: fix subsystem multiple controllers support check" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

nvme: fix subsystem multiple controllers support check

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nvme-fix-subsystem-multiple-controllers-support-check.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Israel Rukshin <[email protected]>
Date: Thu, 4 Jan 2018 17:56:14 +0200
Subject: nvme: fix subsystem multiple controllers support check

From: Israel Rukshin <[email protected]>

commit b837b28394fb76993c28bb242db7061ee0417da6 upstream.

There is a problem when another module (e.g. nvmet) takes a reference on the nvme block device and the physical nvme drive is removed. In that case nvme_free_ctrl() will not be called and the controller state will be "deleting" or "dead" unless nvmet module releases the block device. Later on, the same nvme drive probes back and nvme_init_subsystem() will be called and fail due to duplicate subnqn (if the nvme device doesn't support subsystem with multiple controllers). This will cause a probe failure. This commit changes the check of multiple controllers support at nvme_init_subsystem() by not counting all the controllers at "dead" or "deleting" state (this is safe because controllers at this state will never be active again).

---
 drivers/nvme/host/core.c |   18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

@@ -2052,6 +2052,22 @@ static const struct attribute_group *nvm
 	NULL,
 };
 
+static int nvme_active_ctrls(struct nvme_subsystem *subsys)
+{
+	int count = 0;
+	struct nvme_ctrl *ctrl;
+
+	mutex_lock(&subsys->lock);
+	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+		if (ctrl->state != NVME_CTRL_DELETING &&
+		    ctrl->state != NVME_CTRL_DEAD)
+			count++;
+	}
+	mutex_unlock(&subsys->lock);
+
+	return count;
+}
+
 static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 {
 	struct nvme_subsystem *subsys, *found;

@@ -2090,7 +2106,7 @@ static int nvme_init_subsystem(struct nv
 		 * Verify that the subsystem actually supports multiple
 		 * controllers, else bail out.
 		 */
-		if (!(id->cmic & (1 << 1))) {
+		if (nvme_active_ctrls(found) && !(id->cmic & (1 << 1))) {
 			dev_err(ctrl->device,
 				"ignoring ctrl due to duplicate subnqn (%s).\n",
 				found->subnqn);

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/nvme-fix-subsystem-multiple-controllers-support-check.patch