Re: [PATCH v2 03/10] nvme-multipath: add error handling support for add_disk()

[Hannes Reinecke <hare@xxxxxxx>]

On 9/28/21 12:00 AM, Luis Chamberlain wrote:
> We never checked for errors on add_disk() as this function
> returned void. Now that this is fixed, use the shiny new
> error handling.
>
> Since we now can tell for sure when a disk was added, move
> setting the bit NVME_NSHEAD_DISK_LIVE only when we did
> add the disk successfully.
>
> Nothing to do here as the cleanup is done elsewhere. We take
> care and use test_and_set_bit() because it is protects against
> two nvme paths simultaneously calling device_add_disk() on the
> same namespace head.
>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---
>   drivers/nvme/host/multipath.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index e8ccdd398f78..35cace4f3f5f 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -496,13 +496,22 @@ 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;
>   
> +	/*
> +        * test_and_set_bit() is used because it is protecting against two nvme
> +        * paths simultaneously calling device_add_disk() on the same namespace
> +        * head.
> +        */
>         if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
> -               device_add_disk(&head->subsys->dev, head->disk,
> -                               nvme_ns_id_attr_groups);
> +               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);
>         }
>   
> Errm.
Setting the same bit twice?
And shouldn't you unset the bit if 'device_add_disk()' fails?

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer