linux-kernel - Re: [PATCH] erofs: fix lockdep false positives on initializing erofs_pseudo

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Message-ID: <bca29c1a-6a4d-e128-b9b5-5c48020d4850@huawei.com>
Date: Thu, 7 Mar 2024 15:43:44 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Al Viro <viro@...iv.linux.org.uk>
CC: <linux-erofs@...ts.ozlabs.org>, <xiang@...nel.org>, <chao@...nel.org>,
	<huyue2@...lpad.com>, <jefflexu@...ux.alibaba.com>,
	<linux-kernel@...r.kernel.org>, <yangerkun@...wei.com>, <houtao1@...wei.com>,
	<yukuai3@...wei.com>, <chengzhihao1@...wei.com>, Baokun Li
	<libaokun1@...wei.com>
Subject: Re: [PATCH] erofs: fix lockdep false positives on initializing
 erofs_pseudo_mnt

On 2024/3/7 15:21, Al Viro wrote:
> 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?
It's dawning on me, thank you so much for explaining! ღ( ´･ᴗ･` )

-- 
With Best Regards,
Baokun Li
.