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

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Date: Thu, 7 Mar 2024 17:08:29 +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 16:46, Al Viro wrote:
> On Thu, Mar 07, 2024 at 07:21:12AM +0000, 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?
> PS: at one point I considered renaming it to something that would sound
> less vague, but the best variant I'd been able to come up with was
> "publish_filesystem()", which is not much better and has an extra problem -
> how do you describe the reverse of that?  "withdraw_filesystem()"?
> Decided that it wasn't worth the amount of noise and headache...
I feel the emphasis on "fs_name" rather than "filesystem" is less
likely to be misunderstood. What do you think about renaming
to add_fs_name/remove_fs_name?

-- 
With Best Regards,
Baokun Li
.