Re: [PATCH 2/2] nvme: fix unmatched id's under delayed path deletion

[Christoph Hellwig <hch@lst.de>]

On Wed, Feb 25, 2026 at 12:21:09PM -0800, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> The NVMe controller is allowed to reuse an NSID for a new namespace after
> deleting the previous namespace that had been using it. The delayed removal may
> have the stale namespace head in the subsystem list pending the timer, which

Overlong lines.

> +	bool retry = IS_ENABLED(CONFIG_NVME_MULTIPATH);
>  	struct nvme_ctrl *ctrl = ns->ctrl;
>  	struct nvme_ns_head *head = NULL;
>  	int ret;
> @@ -4008,6 +4009,7 @@ static int nvme_init_ns_head(struct nvme_ns *ns, struct nvme_ns_info *info)
>  		ctrl->quirks |= NVME_QUIRK_BOGUS_NID;
>  	}
>  
> +again:
>  	mutex_lock(&ctrl->subsys->lock);
>  	head = nvme_find_ns_head(ctrl, info->nsid);
>  	if (!head) {
> @@ -4033,6 +4035,22 @@ static int nvme_init_ns_head(struct nvme_ns *ns, struct nvme_ns_info *info)
>  			goto out_put_ns_head;
>  		}
>  		if (!nvme_ns_ids_equal(&head->ids, &info->ids)) {
> +			/*
> +			 * A newly created namespace can reuse an NSID that was
> +			 * previously deleted. If the head has no active paths,
> +			 * it is pending delayed removal and still occupying
> +			 * this NSID in the subsystem list. Flush the removal
> +			 * work to clear the stale head and retry.
> +			 */
> +			if (retry && list_empty(&head->list)) {

I find the retry logic a bit odd and different from other places
do in similar areas.  What I'd expected is either a "nr_retries" or
"did_retry" variable initialized to 0/false, then checked here to
be not set (plus the IS_ENABLED() for multipath) and incremented/set
below.

But independent of that, the actual logic looks fine.