Re: [RFC PATCH] nvme: refuse an unsolicited format change on a namespace that is in use

[Keith Busch <kbusch@kernel.org>]

On Tue, Aug 11, 2026 at 03:21:11PM -0400, Chao Shi wrote:
> @@ -2436,6 +2454,28 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
>  		goto out;
>  	}
>  
> +	/*
> +	 * Changing the LBA format or the metadata size reinterprets everything
> +	 * the host has already cached, queued or handed to the integrity code
> +	 * for this namespace, and freezing the queue does not cover any of it:
> +	 * page cache contents, bios batched on a plug and the deferred
> +	 * integrity verify work all outlive the freeze.  If such a change
> +	 * arrives unsolicited while the namespace is in use, refuse it and let
> +	 * the caller take the namespace offline rather than adopt a geometry
> +	 * that describes something else than what the host is holding.
> +	 */
> +	if (nvme_ns_openers(ns) &&
> +	    !test_bit(NVME_CTRL_SELF_RESCAN, &ns->ctrl->flags) &&
> +	    (ns->head->lba_shift != id->lbaf[lbaf].ds ||
> +	     ns->head->ms != le16_to_cpu(id->lbaf[lbaf].ms))) {
> +		dev_err(ns->ctrl->device,
> +			"unsolicited format change on in-use nsid %u (lba_shift %u -> %u, ms %u -> %u)\n",
> +			info->nsid, ns->head->lba_shift, id->lbaf[lbaf].ds,
> +			ns->head->ms, le16_to_cpu(id->lbaf[lbaf].ms));
> +		ret = NVME_SC_INVALID_NS | NVME_STATUS_DNR;
> +		goto out;
> +	}

Refusing to acknowledge the new format doesn't mean you get to continue
using the old format. You're going to corrupt memory and data this way.