Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260

[Peter Zijlstra]

On Sun, Mar 27, 2016 at 05:03:44AM -0700, Linus Torvalds wrote:
> Anyway, I don't think that DEBUG_LOCKS_WARN_ON() in
> 
>   kernel/locking/lockdep.c:2017 __lock_acquire
> 
> would be an ext4 issue, it looks more like an internal lockdep issue.
> 
> Adding in the lockdep people, who will set me right.

You are right; this is lockdep running into a hash collision; which is a
new DEBUG_LOCKDEP test. See 9e4e7554e755 ("locking/lockdep: Detect
chain_key collisions").