linux-kernel - Re: processes hung after sys_renameat, and 'missing' processes

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Message-ID: <CA+55aFx3QT0AA+s=M+QyJFKqQNh0cHiunwZ=fyrc1eneJTtarQ@mail.gmail.com>
Date:	Wed, 6 Jun 2012 18:45:35 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: processes hung after sys_renameat, and 'missing' processes

On Wed, Jun 6, 2012 at 6:31 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> And you want to check i_mutex on old parent, not the file being moved
> itself.  IOW, the second one should be
>
> if (dentry->d_parent != dentry)
>        WARN_ON_ONCE(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));

Do you even need the "dentry->d_parent != dentry" test? When do we
even rename root dentries?

I do notice that we have that IS_ROOT() test in __d_move(), but now
that I look at it I wonder *why* we have it..

Anyway, Dave, you should probably trust Al over me here - that test
obviously won't hurt, even if I can't see immediately when it would
trigger either.

              Linus
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