linux-kernel - Re: [RFC PATCH 17/20] famfs: Add module stuff

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Message-ID: <20240226134748.00003f57@Huawei.com>
Date: Mon, 26 Feb 2024 13:47:48 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: John Groves <John@...ves.net>
CC: John Groves <jgroves@...ron.com>, Jonathan Corbet <corbet@....net>, "Dan
 Williams" <dan.j.williams@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, "Alexander
 Viro" <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, "Jan
 Kara" <jack@...e.cz>, Matthew Wilcox <willy@...radead.org>,
	<linux-cxl@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <john@...alactic.com>, Dave Chinner
	<david@...morbit.com>, Christoph Hellwig <hch@...radead.org>,
	<dave.hansen@...ux.intel.com>, <gregory.price@...verge.com>
Subject: Re: [RFC PATCH 17/20] famfs: Add module stuff

On Fri, 23 Feb 2024 11:42:01 -0600
John Groves <John@...ves.net> wrote:

> This commit introduces the module init and exit machinery for famfs.
> 
> Signed-off-by: John Groves <john@...ves.net>
I'd prefer to see this from the start with the functionality of the module
built up as you go + build logic in place.  Makes it easy to spot places
where the patches aren't appropriately self constrained. 
> ---
>  fs/famfs/famfs_inode.c | 44 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
> index ab46ec50b70d..0d659820e8ff 100644
> --- a/fs/famfs/famfs_inode.c
> +++ b/fs/famfs/famfs_inode.c
> @@ -462,4 +462,48 @@ static struct file_system_type famfs_fs_type = {
>  	.fs_flags	  = FS_USERNS_MOUNT,
>  };
>  
> +/*****************************************************************************************
> + * Module stuff

I'd drop these drivers structure comments. They add little beyond
a high possibility of being wrong after the code has evolved a bit.

> + */
> +static struct kobject *famfs_kobj;
> +
> +static int __init init_famfs_fs(void)
> +{
> +	int rc;
> +
> +#if defined(CONFIG_DEV_DAX_IOMAP)
> +	pr_notice("%s: Your kernel supports famfs on /dev/dax\n", __func__);
> +#else
> +	pr_notice("%s: Your kernel does not support famfs on /dev/dax\n", __func__);
> +#endif
> +	famfs_kobj = kobject_create_and_add(MODULE_NAME, fs_kobj);
> +	if (!famfs_kobj) {
> +		pr_warn("Failed to create kobject\n");
> +		return -ENOMEM;
> +	}
> +
> +	rc = sysfs_create_group(famfs_kobj, &famfs_attr_group);
> +	if (rc) {
> +		kobject_put(famfs_kobj);
> +		pr_warn("%s: Failed to create sysfs group\n", __func__);
> +		return rc;
> +	}
> +
> +	return register_filesystem(&famfs_fs_type);

If this fails, do we not leak the kobj and sysfs groups?

> +}
> +
> +static void
> +__exit famfs_exit(void)
> +{
> +	sysfs_remove_group(famfs_kobj,  &famfs_attr_group);
> +	kobject_put(famfs_kobj);
> +	unregister_filesystem(&famfs_fs_type);
> +	pr_info("%s: unregistered\n", __func__);
> +}
> +
> +
> +fs_initcall(init_famfs_fs);
> +module_exit(famfs_exit);
> +
> +MODULE_AUTHOR("John Groves, Micron Technology");
>  MODULE_LICENSE("GPL");