linux-kernel - Re: [PATCH v2] bcachefs: chardev: make bch_chardev

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Date: Mon, 11 Mar 2024 09:41:56 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: "Ricardo B. Marliere" <ricardo@...liere.net>, Kent Overstreet
	<kent.overstreet@...ux.dev>, Brian Foster <bfoster@...hat.com>
CC: <linux-bcachefs@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] bcachefs: chardev: make bch_chardev_class constant

It's fine for me.

On 2024/3/8 20:12, Ricardo B. Marliere wrote:
> Since commit 43a7206b0963 ("driver core: class: make class_register() take
> a const *"), the driver core allows for struct class to be in read-only
> memory, so move the bch_chardev_class structure to be declared at build
> time placing it into read-only memory, instead of having to be dynamically
> allocated at boot time. Also, correctly clean up after failing paths in
> bch2_chardev_init().
> 
> Cc: Hongbo Li <lihongbo22@...wei.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Ricardo B. Marliere <ricardo@...liere.net>
> ---
> Changes in v2:
> - Used "free the last thing" pattern in bch2_chardev_init().
> - Link to v1: https://lore.kernel.org/r/20240305-bcachefs-v1-1-436196e25729@marliere.net
> ---
>   fs/bcachefs/chardev.c | 35 ++++++++++++++++++++++-------------
>   1 file changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/bcachefs/chardev.c b/fs/bcachefs/chardev.c
> index 226b39c17667..dc09f547dae6 100644
> --- a/fs/bcachefs/chardev.c
> +++ b/fs/bcachefs/chardev.c
> @@ -940,7 +940,9 @@ static const struct file_operations bch_chardev_fops = {
>   };
>   
>   static int bch_chardev_major;
> -static struct class *bch_chardev_class;
> +static const struct class bch_chardev_class = {
> +	.name = "bcachefs",
> +};
>   static struct device *bch_chardev;
>   
>   void bch2_fs_chardev_exit(struct bch_fs *c)
> @@ -957,7 +959,7 @@ int bch2_fs_chardev_init(struct bch_fs *c)
>   	if (c->minor < 0)
>   		return c->minor;
>   
> -	c->chardev = device_create(bch_chardev_class, NULL,
> +	c->chardev = device_create(&bch_chardev_class, NULL,
>   				   MKDEV(bch_chardev_major, c->minor), c,
>   				   "bcachefs%u-ctl", c->minor);
>   	if (IS_ERR(c->chardev))
> @@ -968,32 +970,39 @@ int bch2_fs_chardev_init(struct bch_fs *c)
>   
>   void bch2_chardev_exit(void)
>   {
> -	if (!IS_ERR_OR_NULL(bch_chardev_class))
> -		device_destroy(bch_chardev_class,
> -			       MKDEV(bch_chardev_major, U8_MAX));
> -	if (!IS_ERR_OR_NULL(bch_chardev_class))
> -		class_destroy(bch_chardev_class);
> +	device_destroy(&bch_chardev_class, MKDEV(bch_chardev_major, U8_MAX));
> +	class_unregister(&bch_chardev_class);
>   	if (bch_chardev_major > 0)
>   		unregister_chrdev(bch_chardev_major, "bcachefs");
>   }
>   
>   int __init bch2_chardev_init(void)
>   {
> +	int ret;
> +
>   	bch_chardev_major = register_chrdev(0, "bcachefs-ctl", &bch_chardev_fops);
>   	if (bch_chardev_major < 0)
>   		return bch_chardev_major;
>   
> -	bch_chardev_class = class_create("bcachefs");
> -	if (IS_ERR(bch_chardev_class))
> -		return PTR_ERR(bch_chardev_class);
> +	ret = class_register(&bch_chardev_class);
> +	if (ret)
> +		goto major_out;
>   
> -	bch_chardev = device_create(bch_chardev_class, NULL,
> +	bch_chardev = device_create(&bch_chardev_class, NULL,
>   				    MKDEV(bch_chardev_major, U8_MAX),
>   				    NULL, "bcachefs-ctl");
> -	if (IS_ERR(bch_chardev))
> -		return PTR_ERR(bch_chardev);
> +	if (IS_ERR(bch_chardev)) {
> +		ret = PTR_ERR(bch_chardev);
> +		goto class_out;
> +	}
>   
>   	return 0;
> +
> +class_out:
> +	class_unregister(&bch_chardev_class);
> +major_out:
> +	unregister_chrdev(bch_chardev_major, "bcachefs-ctl");
> +	return ret;
>   }
>   
>   #endif /* NO_BCACHEFS_CHARDEV */
> 
> ---
> base-commit: 90d35da658da8cff0d4ecbb5113f5fac9d00eb72
> change-id: 20240305-bcachefs-27a4bb8b9f4f
> 
> Best regards,