Re: [PATCH 02/13] libmultipath: Add basic gendisk support

[Benjamin Marzinski <bmarzins@redhat.com>]

On Wed, Feb 25, 2026 at 03:32:14PM +0000, John Garry wrote:
> Add support to allocate and free a multipath gendisk.
> 
> NVMe has almost like-for-like equivalents here:
> - mpath_alloc_head_disk() -> nvme_mpath_alloc_disk()
> - multipath_partition_scan_work() -> nvme_partition_scan_work()
> - mpath_remove_disk() -> nvme_remove_head()
> - mpath_device_set_live() -> nvme_mpath_set_live()
> 
> struct mpath_head_template is introduced as a method for drivers to
> provide custom multipath functionality.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
> +
> +void mpath_device_set_live(struct mpath_disk *mpath_disk,
> +			struct mpath_device *mpath_device)
> +{
> +	struct mpath_head *mpath_head = mpath_disk->mpath_head;

You're dereferencing mpath_disk here, before the check if it's NULL.

-Ben

> +	int ret;
> +
> +	if (!mpath_disk)
> +		return;
> +
> +	if (!test_and_set_bit(MPATH_HEAD_DISK_LIVE, &mpath_head->flags)) {
> +		dev_set_drvdata(disk_to_dev(mpath_disk->disk), mpath_disk);
> +		ret = device_add_disk(mpath_disk->parent, mpath_disk->disk,
> +				mpath_head->mpdt->device_groups);
> +		if (ret) {
> +			clear_bit(MPATH_HEAD_DISK_LIVE, &mpath_head->flags);
> +			return;
> +		}
> +		queue_work(mpath_wq, &mpath_disk->partition_scan_work);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(mpath_device_set_live);
> +
>  struct mpath_head *mpath_alloc_head(void)
>  {
>  	struct mpath_head *mpath_head;
> -- 
> 2.43.5