linux-kernel - Re: [PATCH] netfs: Delete subtree of 'fs/netfs' when netfs module exits

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Message-ID: <89b6b6ae-f805-43be-86ca-d3fb06ad8fec@huaweicloud.com>
Date: Wed, 28 Aug 2024 20:11:39 +0800
From: Baokun Li <libaokun@...weicloud.com>
To: David Howells <dhowells@...hat.com>
Cc: netfs@...ts.linux.dev, jlayton@...nel.org, hsiangkao@...ux.alibaba.com,
 jefflexu@...ux.alibaba.com, linux-erofs@...ts.ozlabs.org,
 brauner@...nel.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, yangerkun@...wei.com, houtao1@...wei.com,
 yukuai3@...wei.com, wozizhi@...wei.com, Baokun Li <libaokun1@...wei.com>,
 stable@...nel.org, Baokun Li <libaokun@...weicloud.com>
Subject: Re: [PATCH] netfs: Delete subtree of 'fs/netfs' when netfs module
 exits

Hi David,

On 2024/8/28 18:37, David Howells wrote:
> libaokun@...weicloud.com wrote:
>
>> In netfs_init() or fscache_proc_init(), we create dentry under 'fs/netfs',
>> but in netfs_exit(), we only delete the proc entry of 'fs/netfs' without
>> deleting its subtree. This triggers the following WARNING:
>>
>> ==================================================================
>> remove_proc_entry: removing non-empty directory 'fs/netfs', leaking at least 'requests'
>> WARNING: CPU: 4 PID: 566 at fs/proc/generic.c:717 remove_proc_entry+0x160/0x1c0
>> Modules linked in: netfs(-)
>> CPU: 4 UID: 0 PID: 566 Comm: rmmod Not tainted 6.11.0-rc3 #860
>> RIP: 0010:remove_proc_entry+0x160/0x1c0
>> Call Trace:
>>   <TASK>
>>   netfs_exit+0x12/0x620 [netfs]
>>   __do_sys_delete_module.isra.0+0x14c/0x2e0
>>   do_syscall_64+0x4b/0x110
>>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> ==================================================================
>>
>> Therefore use remove_proc_subtree instead() of remove_proc_entry() to
>> fix the above problem.
>>
>> Fixes: 7eb5b3e3a0a5 ("netfs, fscache: Move /proc/fs/fscache to /proc/fs/netfs and put in a symlink")
>> Cc: stable@...nel.org
>> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> Should remove_proc_entry() just remove the entire subtree anyway?
Yeah, in general, when we remove a proc entry, we don't care if it has
subtrees. But I'm not sure if there are certain scenarios where entries
must be removed in a certain order .
>
> But you can add:
>
> 	Acked-by: David Howells <dhowells@...hat.com>
>
> David

Thanks for your ack!

-- 
With Best Regards,
Baokun Li