Re: [PATCH v2] nfs: fix kernel warning when removing proc entry

From: ebiederm@xmission.com (Eric W. Biederman)
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	Dan Aloni <dan@kernelim.com>
Subject: Re: [PATCH v2] nfs: fix kernel warning when removing proc entry
Date: Tue, 19 Aug 2014 21:20:38 -0700	[thread overview]
Message-ID: <87ppfvrdux.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <1408217806-25877-1-git-send-email-xiyou.wangcong@gmail.com> (Cong Wang's message of "Sat, 16 Aug 2014 12:36:46 -0700")

Cong Wang <xiyou.wangcong@gmail.com> writes:

> I saw the following kernel warning:

Cong thanks for finding and tracking this.  I was clearly asleep at the
switch when I was testing my fix to the nfs client code :(

I have applied this patch and will push it to Linus after it has a
little bit to sit in linux-next.

Eric

> [ 1852.321222] ------------[ cut here ]------------
> [ 1852.326527] WARNING: CPU: 0 PID: 118 at fs/proc/generic.c:521 remove_proc_entry+0x154/0x16b()
> [ 1852.335630] remove_proc_entry: removing non-empty directory 'fs/nfsfs', leaking at least 'volumes'
> [ 1852.344084] CPU: 0 PID: 118 Comm: kworker/u8:2 Not tainted 3.16.0+ #540
> [ 1852.350036] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [ 1852.354992] Workqueue: netns cleanup_net
> [ 1852.358701]  0000000000000000 ffff880116f2fbd0 ffffffff819c03e9 ffff880116f2fc18
> [ 1852.366474]  ffff880116f2fc08 ffffffff810744ee ffffffff811e0e6e ffff8800d4e96238
> [ 1852.373507]  ffffffff81dbe665 ffff8800d46a5948 0000000000000005 ffff880116f2fc68
> [ 1852.380224] Call Trace:
> [ 1852.381976]  [<ffffffff819c03e9>] dump_stack+0x4d/0x66
> [ 1852.385495]  [<ffffffff810744ee>] warn_slowpath_common+0x7a/0x93
> [ 1852.389869]  [<ffffffff811e0e6e>] ? remove_proc_entry+0x154/0x16b
> [ 1852.393987]  [<ffffffff8107457b>] warn_slowpath_fmt+0x4c/0x4e
> [ 1852.397999]  [<ffffffff811e0e6e>] remove_proc_entry+0x154/0x16b
> [ 1852.402034]  [<ffffffff8129c73d>] nfs_fs_proc_net_exit+0x53/0x56
> [ 1852.406136]  [<ffffffff812a103b>] nfs_net_exit+0x12/0x1d
> [ 1852.409774]  [<ffffffff81785bc9>] ops_exit_list+0x44/0x55
> [ 1852.413529]  [<ffffffff81786389>] cleanup_net+0xee/0x182
> [ 1852.417198]  [<ffffffff81088c9e>] process_one_work+0x209/0x40d
> [ 1852.502320]  [<ffffffff81088bf7>] ? process_one_work+0x162/0x40d
> [ 1852.587629]  [<ffffffff810890c1>] worker_thread+0x1f0/0x2c7
> [ 1852.673291]  [<ffffffff81088ed1>] ? process_scheduled_works+0x2f/0x2f
> [ 1852.759470]  [<ffffffff8108e079>] kthread+0xc9/0xd1
> [ 1852.843099]  [<ffffffff8109427f>] ? finish_task_switch+0x3a/0xce
> [ 1852.926518]  [<ffffffff8108dfb0>] ? __kthread_parkme+0x61/0x61
> [ 1853.008565]  [<ffffffff819cbeac>] ret_from_fork+0x7c/0xb0
> [ 1853.076477]  [<ffffffff8108dfb0>] ? __kthread_parkme+0x61/0x61
> [ 1853.140653] ---[ end trace 69c4c6617f78e32d ]---
>
> It looks wrong that we add "/proc/net/nfsfs" in nfs_fs_proc_net_init()
> while remove "/proc/fs/nfsfs" in nfs_fs_proc_net_exit().
>
> Fixes: commit 65b38851a17 (NFS: Fix /proc/fs/nfsfs/servers and /proc/fs/nfsfs/volumes)
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Trond Myklebust <trond.myklebust@primarydata.com>
> Cc: Dan Aloni <dan@kernelim.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
> v2 - fix nfs_fs_proc_net_init() as well
>
>  fs/nfs/client.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 1c5ff6d..c117b96 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -1418,7 +1418,7 @@ int nfs_fs_proc_net_init(struct net *net)
>  error_2:
>  	remove_proc_entry("servers", nn->proc_nfsfs);
>  error_1:
> -	remove_proc_entry("fs/nfsfs", NULL);
> +	remove_proc_entry("nfsfs", net->proc_net);
>  error_0:
>  	return -ENOMEM;
>  }
> @@ -1429,7 +1429,7 @@ void nfs_fs_proc_net_exit(struct net *net)
>  
>  	remove_proc_entry("volumes", nn->proc_nfsfs);
>  	remove_proc_entry("servers", nn->proc_nfsfs);
> -	remove_proc_entry("fs/nfsfs", NULL);
> +	remove_proc_entry("nfsfs", net->proc_net);
>  }
>  
>  /*