linux-kernel - Re: [PATCH 05/11] pidns: Make the pidns proc mount/umount logic obvious.

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Date:	Mon, 19 Nov 2012 19:02:23 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Linux Containers <containers@...ts.linux-foundation.org>,
	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...sign.ru>,
	Serge Hallyn <serge@...lyn.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 05/11] pidns: Make the pidns proc mount/umount logic obvious.

于 2012年11月17日 00:35, Eric W. Biederman 写道:
> From: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> Track the number of pids in the proc hash table.  When the number of
> pids goes to 0 schedule work to unmount the kernel mount of proc.
> 
> Move the mount of proc into alloc_pid when we allocate the pid for
> init.
> 
> Remove the surprising calls of pid_ns_release proc in fork and
> proc_flush_task.  Those code paths really shouldn't know about proc
> namespace implementation details and people have demonstrated several
> times that finding and understanding those code paths is difficult and
> non-obvious.
> 
> Because of the call path detach pid is alwasy called with the
> rtnl_lock held free_pid is not allowed to sleep, so the work to
> unmounting proc is moved to a work queue.  This has the side benefit
> of not blocking the entire world waiting for the unnecessary
> rcu_barrier in deactivate_locked_super.
> 
> In the process of making the code clear and obvious this fixes a bug
> reported by Gao feng <gaofeng@...fujitsu.com> where we would leak a
> mount of proc during clone(CLONE_NEWPID|CLONE_NEWNET) if copy_pid_ns
> succeeded and copy_net_ns failed.
> 
> Acked-by: "Serge E. Hallyn" <serge@...lyn.com>
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---

Acked-by: Gao feng <gaofeng@...fujitsu.com>
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