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nvme: fix subsystem multiple controllers support check

PATCH New Keith Busch 1 participant 1 message Mar 16, 2018

Subsystems (2)
Stable branch NVMe
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Keith Busch

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PATCH 1/1 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).

Fixes ab9e00cc72fa ("nvme: track subsystems")
Reviewed-by Max Gurtovoy <[email protected]>
Signed-off-by Israel Rukshin <[email protected]>
Signed-off-by Christoph Hellwig <[email protected]>
Signed-off-by Keith Busch <[email protected]>
---
 drivers/nvme/host/core.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)
drivers/nvme/host/core.c +17 -1
index 3551fbd6fe41..935593032123 100644
@@ -2052,6 +2052,22 @@ static const struct attribute_group *nvme_subsys_attrs_groups[] = {
 	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 nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 		 * 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);
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2.14.3