linux-kernel - Re: [PATCH V5 09/19] famfs_fuse: magic.h: Add famfs magic numbers

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Message-ID: <CAJnrk1bvomN7_MZOO8hwf85qLztZys4LfCjfcs_ZUq8+YBk5Wg@mail.gmail.com>
Date: Tue, 27 Jan 2026 13:55:44 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: john@...alactic.com
Cc: John Groves <John@...ves.net>, Miklos Szeredi <miklos@...redi.hu>, 
	Dan Williams <dan.j.williams@...el.com>, Bernd Schubert <bschubert@....com>, 
	Alison Schofield <alison.schofield@...el.com>, John Groves <jgroves@...ron.com>, 
	John Groves <jgroves@...tmail.com>, Jonathan Corbet <corbet@....net>, 
	Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, 
	Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>, 
	Alexander Viro <viro@...iv.linux.org.uk>, David Hildenbrand <david@...nel.org>, 
	Christian Brauner <brauner@...nel.org>, "Darrick J . Wong" <djwong@...nel.org>, 
	Randy Dunlap <rdunlap@...radead.org>, Jeff Layton <jlayton@...nel.org>, 
	Amir Goldstein <amir73il@...il.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
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	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH V5 09/19] famfs_fuse: magic.h: Add famfs magic numbers

On Fri, Jan 16, 2026 at 11:52 AM John Groves <john@...alactic.com> wrote:
>
> From: John Groves <john@...ves.net>
>
> Famfs distinguishes between its on-media and in-memory superblocks. This
> reserves the numbers, but they are only used by the user space
> components of famfs.
>
> Signed-off-by: John Groves <john@...ves.net>
> ---
>  include/uapi/linux/magic.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
> index 638ca21b7a90..712b097bf2a5 100644
> --- a/include/uapi/linux/magic.h
> +++ b/include/uapi/linux/magic.h
> @@ -38,6 +38,8 @@
>  #define OVERLAYFS_SUPER_MAGIC  0x794c7630
>  #define FUSE_SUPER_MAGIC       0x65735546
>  #define BCACHEFS_SUPER_MAGIC   0xca451a4e
> +#define FAMFS_SUPER_MAGIC      0x87b282ff
> +#define FAMFS_STATFS_MAGIC      0x87b282fd

Could you explain why this needs to be added to uapi? If they are used
only by userspace, does it make more sense for these constants to live
in the userspace code instead?

Thanks,
Joanne

>
>  #define MINIX_SUPER_MAGIC      0x137F          /* minix v1 fs, 14 char names */
>  #define MINIX_SUPER_MAGIC2     0x138F          /* minix v1 fs, 30 char names */
> --
> 2.52.0
>
>