[PATCH V5 7/7] nvme-core: warn on allocating admin tag set with existing queue

[Hannes Reinecke]

On 5/14/26 10:32, Maurizio Lombardi wrote:
> 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: Sagi Grimberg <sagi at grimberg.me>
> 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 e6bb1f5e9657..f23a957c6e8f 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -4893,12 +4893,7 @@ 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)) {

Why don't you return an error here?
The WARN_ON() now introduces a memory leak (at best); I'd rather
not do that here as we can easily recover here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
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