Re: WARNING: locking bug in split_huge_page_to_list

[Matthew Wilcox]

On Tue, Apr 23, 2019 at 09:13:06AM -0700, syzbot wrote:
> DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS)
> WARNING: CPU: 0 PID: 1553 at kernel/locking/lockdep.c:3673
> __lock_acquire+0x1887/0x3fb0 kernel/locking/lockdep.c:3673
>  down_write+0x38/0x90 kernel/locking/rwsem.c:70
>  anon_vma_lock_write include/linux/rmap.h:120 [inline]

All anon_vmas share the same lockdep map, so I think this is just a
victim of someone else who's taken all the lockdep classes.