linux-kernel - Re: fs: lockup on rename

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Date:	Sun, 26 Oct 2014 16:33:11 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: fs: lockup on rename_mutex in fs/dcache.c:1035

On Sun, Oct 26, 2014 at 2:57 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>  .. snip ..
> in d_walk(), __list_del() instead of list_del() in __dentry_kill(), d_u.d_child
> turning into d_child everywhere, while d_alias turns into d_u.d_alias...
>
> It looks like that way we would get no retries on the second pass.  Comments?

Since I missed the whole issue with d_child.next, I'm not sure any
comments from me would be helpful.

It does sound like trying to be more careful with d_child and using
d_alias instead is a good idea. d_alias is only used under the dentry
lock, and not in any horribly subtle situations, right? So that sounds
like a good change regardless of this particular fix - making the
union happen in a less nasty place..

                     Linus
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