linux-kernel - Re: [PATCH] Use proper lock in fscache_objlist

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Message-ID: <20161004155417.GC19785@shodan.usersys.redhat.com>
Date:   Tue, 4 Oct 2016 17:54:17 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-cachefs@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Use proper lock in fscache_objlist_config.

On Tue, Oct 04, 2016 at 04:43:31PM +0100, David Howells wrote:
> Artem Savkov <asavkov@...hat.com> 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.

-- 
Regards,
  Artem