Re: 5.14-0-rc5, splat in block_group_cache_tree_search while __btrfs_unlink_inode

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Aug 16, 2021 at 10:43:54PM +0200, David Sterba wrote:
> On Mon, Aug 16, 2021 at 05:11:55PM +0200, Peter Zijlstra wrote:
> > Something a little like the *completely* untested below....
> > 
> > Then I imagine someone could do something like:
> > 
> > struct my_tree_node {
> > 	...
> > 	spinlock_t lock;
> 
> Is this meant to work only for spinlocks or does it work for rwsem too?
> I guess with lockdep it does not matter but we use rwsem for tree locks.

Anything with a ->dep_map member works; courtesy of macros :-) That very
much includes rwsems.

> > @@ -4920,6 +4962,15 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
> >  
> >  	class_idx = class - lock_classes;
> >  
> > +	if (nest_lock) {
> > +		if (!__lock_is_held(nest_lock, -1)) {
> > +			print_lock_nested_lock_not_held(curr, hlock, ip);
> > +			return 0;
> > +		}
> > +		if (nest_lock->type == LD_LOCK_NEST_FUNC)
> 
> That's probably nest_lock->lock_type, does not compile otherwise.

Yes, sorry, typing so hard :-)