linux-kernel - Re: [PATCH] autofs4 - fix get_next_positive

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Message-ID: <1337758248.2225.9.camel@perseus.themaw.net>
Date:	Wed, 23 May 2012 15:30:48 +0800
From:	Ian Kent <ikent@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	autofs mailing list <autofs@...ux.kernel.org>
Subject: Re: [PATCH] autofs4 - fix get_next_positive_subdir()

On Wed, 2012-05-23 at 15:22 +0800, Ian Kent wrote:
> On Tue, 2012-05-22 at 19:53 -0700, Linus Torvalds wrote:
> > On Tue, May 22, 2012 at 7:49 PM, Ian Kent <ikent@...hat.com> wrote:
> > >
> > > The locking for the list traversal in get_next_positive_subdir() is
> > > wrong, so fix it.
> > 
> > As an explanation, this kind of thing is totally useless. It doesn't
> > actually give any information at all. It's like saying "change
> > locking"
> > 
> > What happened, and why? Why is the new nested spinlock ok and won't
> > deadlock against other nested users? Wazzup?
> 
> It's good that you questioned this Linus.
> 
> Looking again at dput() I think the traversal still isn't quite right.
> 
> For a start the test for d_count 0 or positive and hashed can never be

Correction, that second check is actually !(positive and hashed) in the
code.

> true since the point of the change was to take the d_lock of the
> d_subdirs dentry for the traversal.
> 
> I'll need to work on this some more, thanks.
> Ian


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