[PATCH 3/3] nvme: check that EUI/GUID/UUID are globally unique

[Keith Busch]

On Thu, Feb 24, 2022 at 11:58:52AM +0100, Christoph Hellwig wrote:
> Add a check to verify that the unique identifiers are unique globally
> in addition to the existing check that verifies that they are unique
> inside a single subsystem.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  drivers/nvme/host/core.c | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index ac4749f257439..4f9623d9f7ed9 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3783,7 +3783,7 @@ static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
>  	ret = nvme_subsys_check_duplicate_ids(ctrl->subsys, &head->ids);
>  	if (ret) {
>  		dev_err(ctrl->device,
> -			"duplicate IDs for nsid %d\n", nsid);
> +			"duplicate IDs in subsystem for nsid %d\n", nsid);
>  		goto out_cleanup_srcu;
>  	}
>  
> @@ -3815,12 +3815,40 @@ static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
>  	return ERR_PTR(ret);
>  }
>  
> +static int nvme_global_check_ids(struct nvme_subsystem *this,
> +		struct nvme_ns_ids *ids)
> +{
> +	struct nvme_subsystem *s;
> +	int ret = 0;
> +
> +	mutex_lock(&nvme_subsystems_lock);
> +	list_for_each_entry(s, &nvme_subsystems, entry) {
> +		if (s == this)
> +			continue;
> +		mutex_lock(&s->lock);
> +		ret = nvme_subsys_check_duplicate_ids(s, ids);
> +		mutex_unlock(&s->lock);
> +		if (ret)
> +			break;
> +	}
> +	mutex_unlock(&nvme_subsystems_lock);
> +
> +	return ret;
> +}
> +
>  static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
>  		struct nvme_ns_ids *ids, bool is_shared)
>  {
>  	struct nvme_ctrl *ctrl = ns->ctrl;
>  	struct nvme_ns_head *head = NULL;
> -	int ret = 0;
> +	int ret;
> +
> +	ret = nvme_global_check_ids(ctrl->subsys, ids);
> +	if (ret) {
> +		dev_err(ctrl->device,
> +			"globally duplicate IDs for nsid %d\n", nsid);
> +		return ret;
> +	}

It looks like a race condition exists here such that two namespaces with
duplicate IDs in different subsystems being concurrently added may not
see the duplicate.