Re: [PATCH] Use proper lock in fscache_objlist_config.

From: Artem Savkov
Date: Tue Oct 04 2016 - 11:54:24 EST

On Tue, Oct 04, 2016 at 04:43:31PM +0100, David Howells wrote:
> Artem Savkov <asavkov@xxxxxxxxxx> wrote:
> > fscache_objlist_config doesn't hold rkey->sem when calling user_key_payload,
> > that can result in a "suspicious RCU usage" warning. It does hold
> > rcu_read_lock, so it either needs to use unprotected rcu_dereference,
> > or take rkey->sem instead of rcu_read_lock.
> It shouldn't take key->sem. The RCU lock should be necessary as
> user_key_payload() wraps a call to rcu_dereference().
> Did you encounter a lockdep report or did you visually inspect this?

I didn't see a lockdep report for this one, I just assumed it would be
the same as with the nfs_idmap_get_key case.