linux-kernel - Re: [PATCH 03/10] nvme-multipath: add error handling support for add

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Date:   Fri, 27 Aug 2021 13:29:32 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     axboe@...nel.dk, colyli@...e.de, kent.overstreet@...il.com,
        sagi@...mberg.me, vishal.l.verma@...el.com,
        dan.j.williams@...el.com, dave.jiang@...el.com,
        ira.weiny@...el.com, konrad.wilk@...cle.com, roger.pau@...rix.com,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        sstabellini@...nel.org, minchan@...nel.org, ngupta@...are.org,
        senozhatsky@...omium.org, xen-devel@...ts.xenproject.org,
        nvdimm@...ts.linux.dev, linux-nvme@...ts.infradead.org,
        linux-bcache@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10] nvme-multipath: add error handling support for
 add_disk()

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);
>  	}