Hello, On Fri, Oct 06, 2017 at 11:06:04AM +0200, Michal Hocko wrote: > On Fri 06-10-17 16:59:18, Jia-Ju Bai wrote: > > According to fs/super.c, the kernel may sleep under a spinlock. > > The function call path is: > > put_super (acquire the spinlock) > > __put_super > > destroy_super > > list_lru_destroy > > list_lru_unregister > > mutex_lock --> may sleep > > memcg_get_cache_ids > > down_read --> may sleep > > > > This bug is found by my static analysis tool and my code review.
This is false-positive: by the time we get to destroy_super(), the lru lists have already been destroyed - see deactivate_locked_super() - so list_lru_destroy() will retrun right away without attempting to take any locks. That's why there's no lockdep warnings regarding this issue. I think we can move list_lru_destroy() to destroy_super_work() to suppress this warning. Not sure if it's really worth the trouble though. Thanks, Vladimir
