linux-kernel - Re: VFS deadlock ?

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Message-ID: <CA+55aFyvwJK99YvDLDsazD4tWT6sNQO6kGM_1WyDdvwPNDxbLw@mail.gmail.com>
Date:	Thu, 21 Mar 2013 13:15:08 -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>
Subject: Re: VFS deadlock ?

On Thu, Mar 21, 2013 at 12:29 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> #0 oddity aside, that looks very much like directory aliased by two different
> dentries.  Try to add
>         BUG_ON(p1->d_inode == p2->d_inode);
> just before
>         mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
> and see if it triggers.

Don't do a BUG_ON(), instead do something like

   if (WARN_ON_ONCE(p1->d_inode == p2->d_inode)) {
        printk("pi=%s p2=%s\n", pi->d_name, p2->d_name);
        mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
        return NULL;
   }

so that we actually see where it is. I'm assuming it's some sysfs oddity again..

            Linus
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