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From: Al Viro <viro@zeniv.linux.org.uk>
To: Wenbin Zeng <wenbin.zeng@gmail.com>
Cc: davem@davemloft.net, bfields@fieldses.org, jlayton@kernel.org,
	trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
	wenbinzeng@tencent.com, dsahern@gmail.com,
	nicolas.dichtel@6wind.com, willy@infradead.org,
	edumazet@google.com, jakub.kicinski@netronome.com,
	tyhicks@canonical.com, chuck.lever@oracle.com, neilb@suse.com,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/3] nsfs: add evict callback into struct proc_ns_operations
Date: Thu, 2 May 2019 04:04:06 +0100	[thread overview]
Message-ID: <20190502030406.GT23075@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1556692945-3996-2-git-send-email-wenbinzeng@tencent.com>

On Wed, May 01, 2019 at 02:42:23PM +0800, Wenbin Zeng wrote:
> The newly added evict callback shall be called by nsfs_evict(). Currently
> only put() callback is called in nsfs_evict(), it is not able to release
> all netns refcount, for example, a rpc client holds two netns refcounts,
> these refcounts are supposed to be released when the rpc client is freed,
> but the code to free rpc client is normally triggered by put() callback
> only when netns refcount gets to 0, specifically:
>     refcount=0 -> cleanup_net() -> ops_exit_list -> free rpc client
> But netns refcount will never get to 0 before rpc client gets freed, to
> break the deadlock, the code to free rpc client can be put into the newly
> added evict callback.
> 
> Signed-off-by: Wenbin Zeng <wenbinzeng@tencent.com>
> ---
>  fs/nsfs.c               | 2 ++
>  include/linux/proc_ns.h | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index 60702d6..5939b12 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -49,6 +49,8 @@ static void nsfs_evict(struct inode *inode)
>  	struct ns_common *ns = inode->i_private;
>  	clear_inode(inode);
>  	ns->ops->put(ns);
> +	if (ns->ops->evict)
> +		ns->ops->evict(ns);

What's to guarantee that ns will not be freed by ->put()?
Confused...

  reply	other threads:[~2019-05-02  3:05 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01  6:42 [PATCH 0/3] auth_gss: netns refcount leaks when use-gss-proxy==1 Wenbin Zeng
2019-05-01  6:42 ` [PATCH 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-05-02  3:04   ` Al Viro [this message]
2019-05-04 16:08     ` Wenbin Zeng
2019-05-01  6:42 ` [PATCH 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-05-04  4:10   ` David Miller
2019-05-01  6:42 ` [PATCH 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-05-09 20:52 ` [PATCH 0/3] auth_gss: netns refcount leaks " J. Bruce Fields
2019-05-10  5:09   ` Wenbin Zeng
2019-05-10  6:36 ` [PATCH v2 " Wenbin Zeng
2019-05-10  6:36   ` [PATCH v2 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-05-10  6:36   ` [PATCH v2 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-05-10 22:13     ` David Miller
2019-05-10  6:36   ` [PATCH v2 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-05-15  1:03   ` [PATCH v2 0/3] auth_gss: netns refcount leaks " J. Bruce Fields
2019-06-12  8:37     ` Wenbin Zeng
2019-06-12 15:52       ` J. Bruce Fields
2021-09-07 14:48         ` wanghai (M)
2021-09-08 20:51           ` J. Bruce Fields
2021-09-09  2:52             ` wanghai (M)
2021-09-09 19:52               ` J. Bruce Fields
2019-06-12 12:09 ` [PATCH v3 " Wenbin Zeng
2019-06-12 12:09   ` [PATCH v3 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-06-12 12:09   ` [PATCH v3 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-06-12 12:09   ` [PATCH v3 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-08-01 19:53   ` [PATCH v3 0/3] auth_gss: netns refcount leaks " J. Bruce Fields
2021-08-28 11:26     ` wanghai (M)

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