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Date: Thu, 7 Mar 2024 15:43:44 +0800
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Subject: Re: [PATCH] erofs: fix lockdep false positives on initializing
 erofs_pseudo_mnt
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To: Al Viro <viro@zeniv.linux.org.uk>
CC: <linux-erofs@lists.ozlabs.org>, <xiang@kernel.org>, <chao@kernel.org>,
	<huyue2@coolpad.com>, <jefflexu@linux.alibaba.com>,
	<linux-kernel@vger.kernel.org>, <yangerkun@huawei.com>, <houtao1@huawei.com>,
	<yukuai3@huawei.com>, <chengzhihao1@huawei.com>, Baokun Li
	<libaokun1@huawei.com>
References: <20240307024459.883044-1-libaokun1@huawei.com>
 <20240307050717.GB538574@ZenIV>
 <7e9746db-033e-64d0-a3d5-9d341c66cec7@huawei.com>
 <20240307072112.GC538574@ZenIV>
From: Baokun Li <libaokun1@huawei.com>
In-Reply-To: <20240307072112.GC538574@ZenIV>
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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
.