Re: [PATCH V3] nvme: introduce nvme_disk_is_ns_head helper

[Liu Song <liusong@linux.alibaba.com>]

Using helper functions makes the code more readable.

Reviewed-by: Liu Song <liusong@linux.alibaba.com>

在 2023/12/27 17:31, Guixin Liu 写道:
> We currently rely on gendisk's file operations (fops) to distinguish
> between a namespace head (ns_head) and a regular namespace. To enhance
> code readability, introduce a helper function.
> Additionally, we must ensure that the device is not an ns_head before
> calling nvme_get_ns_from_dev(). To enforce this, add a WARN_ON check
> within the nvme_get_ns_from_dev().
>
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> ---
> Changes from v2 to v3:
> - simplify to disk->fops == &nvme_ns_head_ops.
>
> Changes from v1 to v2:
> - change helper name from nvme_gendisk_is_ns_head to
>    nvme_disk_is_ns_head.
> - remove redundant comment.
>
>   drivers/nvme/host/nvme.h  | 10 +++++++++-
>   drivers/nvme/host/pr.c    |  2 +-
>   drivers/nvme/host/sysfs.c |  9 +++++----
>   3 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index e7411dac00f7..3dcbf48e9fdf 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -1029,9 +1029,17 @@ static inline int nvme_update_zone_info(struct nvme_ns *ns, unsigned lbaf)
>   }
>   #endif
>   
> +static inline bool nvme_disk_is_ns_head(struct gendisk *disk)
> +{
> +	return disk->fops == &nvme_ns_head_ops;
> +}
> +
>   static inline struct nvme_ns *nvme_get_ns_from_dev(struct device *dev)
>   {
> -	return dev_to_disk(dev)->private_data;
> +	struct gendisk *disk = dev_to_disk(dev);
> +
> +	WARN_ON(nvme_disk_is_ns_head(disk));
> +	return disk->private_data;
>   }
>   
>   #ifdef CONFIG_NVME_HWMON
> diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> index 391b1465ebfd..fc3eed00f9ff 100644
> --- a/drivers/nvme/host/pr.c
> +++ b/drivers/nvme/host/pr.c
> @@ -98,7 +98,7 @@ static int nvme_send_pr_command(struct block_device *bdev,
>   		struct nvme_command *c, void *data, unsigned int data_len)
>   {
>   	if (IS_ENABLED(CONFIG_NVME_MULTIPATH) &&
> -	    bdev->bd_disk->fops == &nvme_ns_head_ops)
> +	    nvme_disk_is_ns_head(bdev->bd_disk))
>   		return nvme_send_ns_head_pr_command(bdev, c, data, data_len);
>   
>   	return nvme_send_ns_pr_command(bdev->bd_disk->private_data, c, data,
> diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
> index c6b7fbd4d34d..925042ca728b 100644
> --- a/drivers/nvme/host/sysfs.c
> +++ b/drivers/nvme/host/sysfs.c
> @@ -39,10 +39,10 @@ static inline struct nvme_ns_head *dev_to_ns_head(struct device *dev)
>   {
>   	struct gendisk *disk = dev_to_disk(dev);
>   
> -	if (disk->fops == &nvme_bdev_ops)
> -		return nvme_get_ns_from_dev(dev)->head;
> -	else
> +	if (nvme_disk_is_ns_head(disk))
>   		return disk->private_data;
> +	else
> +		return nvme_get_ns_from_dev(dev)->head;
>   }
>   
>   static ssize_t wwid_show(struct device *dev, struct device_attribute *attr,
> @@ -148,7 +148,8 @@ static umode_t nvme_ns_id_attrs_are_visible(struct kobject *kobj,
>   	}
>   #ifdef CONFIG_NVME_MULTIPATH
>   	if (a == &dev_attr_ana_grpid.attr || a == &dev_attr_ana_state.attr) {
> -		if (dev_to_disk(dev)->fops != &nvme_bdev_ops) /* per-path attr */
> +		/* per-path attr */
> +		if (nvme_disk_is_ns_head(dev_to_disk(dev)))
>   			return 0;
>   		if (!nvme_ctrl_use_ana(nvme_get_ns_from_dev(dev)->ctrl))
>   			return 0;