Re: [PATCH 26/70] NFSd: Fix delegation revocation

[Bruce Fields <bfields@fieldses.org>]

On Fri, Apr 18, 2014 at 02:44:20PM -0400, Trond Myklebust wrote:
> Ensure that the delegations cannot be found by the laundromat etc once
> we add them to the various 'revoke' lists.

The current code does already attempt to do that...  I guess the point
is that there's a race in that it leaves a window after a delegation is
added to one of the local lists but before it's actually unhashed, as
here:

> @@ -3612,7 +3620,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>  				test_val = u;
>  			break;
>  		}
> -		list_move(&dp->dl_recall_lru, &reaplist);
> +		unhash_delegation_locked(dp);
> +		list_add(&dp->dl_recall_lru, &reaplist);
>  	}
>  	spin_unlock(&state_lock);

where we've been dropping a lock with the thing still hashed.

OK, good, but maybe the changelog could be a little more precise about
what's being fixed.

Also it would be nice if this could be done earlier in the series as
it's a bugfix that people will probably want backported.

--b.