Re: [PATCH] md-cluster: make md-cluster also can work when compiled into kernel

[NeilBrown <neilb@suse.com>]

[-- Attachment #1: Type: text/plain, Size: 1877 bytes --]

On Fri, Sep 02 2016, Guoqing Jiang wrote:

> The md-cluster is compiled as module by default,
> if it is compiled by built-in way, then we can't
> make md-cluster works.
>
> [64782.630008] md/raid1:md127: active with 2 out of 2 mirrors
> [64782.630528] md-cluster module not found.
> [64782.630530] md127: Could not setup cluster service (-2)
>
> Fixes: edb39c9 ("Introduce md_cluster_operations to handle cluster functions")
> Cc: stable@vger.kernel.org # v4.1+
> Cc: NeilBrown <neilb@suse.com>
> Reported-by: Marc Smith <marc.smith@mcc.edu>
> Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
> ---
>  drivers/md/md.c | 21 +++++++++------------
>  1 file changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index bdbbb6e1..3b19d21 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -7619,20 +7619,17 @@ EXPORT_SYMBOL(unregister_md_cluster_operations);
>  
>  int md_setup_cluster(struct mddev *mddev, int nodes)
>  {
> -	int err;
> -
> -	err = request_module("md-cluster");
> -	if (err) {
> -		pr_err("md-cluster module not found.\n");
> -		return -ENOENT;
> -	}
> -
> -	spin_lock(&pers_lock);
> -	if (!md_cluster_ops || !try_module_get(md_cluster_mod)) {
> +	if (!md_cluster_ops) {
> +		/* load module and ensure it won't be unloaded */
> +		request_module("md-cluster");
> +		spin_lock(&pers_lock);
> +		if (!try_module_get(md_cluster_mod)) {
> +			pr_err("can't get md-cluster module reference.\n");
> +			spin_unlock(&pers_lock);
> +			return -ENODEV;
> +		}
>  		spin_unlock(&pers_lock);
> -		return -ENOENT;
>  	}
> -	spin_unlock(&pers_lock);
>  
>  	return md_cluster_ops->join(mddev, nodes);
>  }
> -- 
> 2.6.6

No good.  If md_cluster_ops is set, try_module_get() won't be called, so
it will be possible to unload the module while it is in use.

NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 800 bytes --]