Re: [PATCH 03/10] nvme-multipath: add error handling support for add_disk()

From: Keith Busch <kbusch@kernel.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: axboe@kernel.dk, colyli@suse.de, kent.overstreet@gmail.com,
	sagi@grimberg.me, vishal.l.verma@intel.com,
	dan.j.williams@intel.com, dave.jiang@intel.com,
	ira.weiny@intel.com, konrad.wilk@oracle.com,
	roger.pau@citrix.com, boris.ostrovsky@oracle.com,
	jgross@suse.com, sstabellini@kernel.org, minchan@kernel.org,
	ngupta@vflare.org, senozhatsky@chromium.org,
	xen-devel@lists.xenproject.org, nvdimm@lists.linux.dev,
	linux-nvme@lists.infradead.org, linux-bcache@vger.kernel.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/10] nvme-multipath: add error handling support for add_disk()
Date: Fri, 27 Aug 2021 13:29:32 -0700	[thread overview]
Message-ID: <20210827202932.GA82376@dhcp-10-100-145-180.wdc.com> (raw)
In-Reply-To: <20210827191809.3118103-4-mcgrof@kernel.org>

On Fri, Aug 27, 2021 at 12:18:02PM -0700, Luis Chamberlain wrote:
> @@ -479,13 +479,17 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
>  static void nvme_mpath_set_live(struct nvme_ns *ns)
>  {
>  	struct nvme_ns_head *head = ns->head;
> +	int rc;
>  
>  	if (!head->disk)
>  		return;
>  
> -	if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
> -		device_add_disk(&head->subsys->dev, head->disk,
> -				nvme_ns_id_attr_groups);
> +	if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {

This should still be test_and_set_bit() because it is protecting against
two nvme paths simultaneously calling device_add_disk() on the same
namespace head.

> +		rc = device_add_disk(&head->subsys->dev, head->disk,
> +				     nvme_ns_id_attr_groups);
> +		if (rc)
> +			return;
> +		set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);
>  		nvme_add_ns_head_cdev(head);
>  	}