Re: [PATCH] Fix suspicious RCU usage in nfs_idmap_get_key.

From: David Howells
Date: Tue Oct 04 2016 - 11:45:22 EST

Artem Savkov <asavkov@xxxxxxxxxx> wrote:

> nfs_idmap_get_key doesn't hold rkey->sem when calling user_key_payload
> resulting in a "suspicious RCU usage" lockdep splat. It does, however hold
> rcu_read_lock, so it either needs to use unprotected rcu_dereference, or take
> rkey->sem instead of rcu_read_lock.

This shouldn't be using rkey->sem. user_key_payload() should do sufficient
RCU magic that rcu_read_lock() is sufficient. Can you please include the RCU
splat? It's possible user_key_payload() is wrong.