Re: [PATCH] erofs: fix lockdep false positives on initializing erofs_pseudo_mnt

[Al Viro]

On Thu, Mar 07, 2024 at 03:06:49PM +0800, Baokun Li wrote:
> > > +int erofs_anon_register_fs(void)
> > > +{
> > > +	return register_filesystem(&erofs_anon_fs_type);
> > > +}
> > What for?  The only thing it gives you is an ability to look it up by
> > name.  Which is completely pointless, IMO,
> The helper function here is to avoid extern erofs_anon_fs_type(), because
> we define it in fscache.c, but also use it in super.c. Moreover, we don't
> need
> to register it when CONFIG_EROFS_FS_ONDEMAND is not enabled, so we

You don't need to register it at all.

The one and only effect of register_filesystem() is making file_system_type
instance visible to get_fs_type() (and making it show up in /proc/filesystems).

That's it.  If you want to have it looked up by name (e.g. for userland
mounts), you need to register.  If not, you do not need to do that.

Note that kern_mount() take a pointer to struct file_system_type,
not its (string) name.  So all you get from registration is an extra line
in /proc/filesystems.  What's the point?