[PATCH V4 9/9] nvme-core: warn on allocating admin tag set with existing queue

[Maurizio Lombardi]

Currently, nvme_alloc_admin_tag_set() silently drops and releases
the existing admin_q if it called on a controller that already
had one (e.g., during a controller reset).

However, transport drivers should not be reallocating the admin tag
set and queue during a reset. Dropping the old queue and allocating
a new one destroys user-configured timeouts and may race against
nvme_admin_timeout_store()

Since all transport drivers are now expected to preserve the admin queue
across resets, calling nvme_alloc_admin_tag_set() when ctrl->admin_q
is already populated is a bug.

Remove the silent cleanup and replace it with a WARN_ON_ONCE() to
explicitly catch any transport drivers that violate this lifecycle rule

Reviewed-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Daniel Wagner <dwagner at suse.de>
Signed-off-by: Maurizio Lombardi <mlombard at redhat.com>
---
 drivers/nvme/host/core.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 73575d087a07..14876b5ec5e3 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4889,12 +4889,7 @@ int nvme_alloc_admin_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set,
 	if (ret)
 		return ret;
 
-	/*
-	 * If a previous admin queue exists (e.g., from before a reset),
-	 * put it now before allocating a new one to avoid orphaning it.
-	 */
-	if (ctrl->admin_q)
-		blk_put_queue(ctrl->admin_q);
+	WARN_ON_ONCE(ctrl->admin_q);
 
 	ctrl->admin_q = blk_mq_alloc_queue(set, NULL, NULL);
 	if (IS_ERR(ctrl->admin_q)) {
-- 
2.54.0