Re: [PATCH v4 04/10] nfsd: Fix delegation revocation

["J. Bruce Fields" <bfields@fieldses.org>]

On Fri, Jul 18, 2014 at 11:13:30AM -0400, Jeff Layton wrote:
> Ensure that the delegations cannot be found by the laundromat etc once
> we add them to the various 'revoke' lists.

So if I understand right, the big mutex protects all of this right now,
so this is all just moving the unhashing under a finer-grained lock to
prevent that in-between state being exposed after the big lock's
dropped.  Looks reasonable.

--b.

> 
> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> Signed-off-by: Jeff Layton <jlayton@primarydata.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/nfsd/nfs4state.c | 37 +++++++++++++++++++++----------------
>  1 file changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 60ae21abce00..7c5233427c9b 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -650,13 +650,13 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
>  	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
>  }
>  
> -/* Called under the state lock. */
>  static void
> -unhash_delegation(struct nfs4_delegation *dp)
> +unhash_delegation_locked(struct nfs4_delegation *dp)
>  {
>  	struct nfs4_file *fp = dp->dl_file;
>  
> -	spin_lock(&state_lock);
> +	lockdep_assert_held(&state_lock);
> +
>  	dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
>  	spin_lock(&fp->fi_lock);
>  	list_del_init(&dp->dl_perclnt);
> @@ -665,7 +665,6 @@ unhash_delegation(struct nfs4_delegation *dp)
>  	spin_unlock(&fp->fi_lock);
>  	if (fp)
>  		nfs4_put_deleg_lease(fp);
> -	spin_unlock(&state_lock);
>  }
>  
>  static void destroy_revoked_delegation(struct nfs4_delegation *dp)
> @@ -676,7 +675,9 @@ static void destroy_revoked_delegation(struct nfs4_delegation *dp)
>  
>  static void destroy_delegation(struct nfs4_delegation *dp)
>  {
> -	unhash_delegation(dp);
> +	spin_lock(&state_lock);
> +	unhash_delegation_locked(dp);
> +	spin_unlock(&state_lock);
>  	nfs4_put_delegation(dp);
>  }
>  
> @@ -685,11 +686,10 @@ static void revoke_delegation(struct nfs4_delegation *dp)
>  	struct nfs4_client *clp = dp->dl_stid.sc_client;
>  
>  	if (clp->cl_minorversion == 0)
> -		destroy_delegation(dp);
> +		destroy_revoked_delegation(dp);
>  	else {
> -		unhash_delegation(dp);
>  		dp->dl_stid.sc_type = NFS4_REVOKED_DELEG_STID;
> -		list_add(&dp->dl_recall_lru, &clp->cl_revoked);
> +		list_move(&dp->dl_recall_lru, &clp->cl_revoked);
>  	}
>  }
>  
> @@ -1447,15 +1447,16 @@ destroy_client(struct nfs4_client *clp)
>  	spin_lock(&state_lock);
>  	while (!list_empty(&clp->cl_delegations)) {
>  		dp = list_entry(clp->cl_delegations.next, struct nfs4_delegation, dl_perclnt);
> -		list_del_init(&dp->dl_perclnt);
> +		unhash_delegation_locked(dp);
>  		/* Ensure that deleg break won't try to requeue it */
>  		++dp->dl_time;
> -		list_move(&dp->dl_recall_lru, &reaplist);
> +		list_add(&dp->dl_recall_lru, &reaplist);
>  	}
>  	spin_unlock(&state_lock);
>  	while (!list_empty(&reaplist)) {
>  		dp = list_entry(reaplist.next, struct nfs4_delegation, dl_recall_lru);
> -		destroy_delegation(dp);
> +		list_del_init(&dp->dl_recall_lru);
> +		nfs4_put_delegation(dp);
>  	}
>  	list_splice_init(&clp->cl_revoked, &reaplist);
>  	while (!list_empty(&reaplist)) {
> @@ -3655,7 +3656,7 @@ nfs4_open_delegation(struct net *net, struct svc_fh *fh,
>  	open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
>  	return;
>  out_free:
> -	destroy_delegation(dp);
> +	nfs4_put_delegation(dp);
>  out_no_deleg:
>  	open->op_delegate_type = NFS4_OPEN_DELEGATE_NONE;
>  	if (open->op_claim_type == NFS4_OPEN_CLAIM_PREVIOUS &&
> @@ -3894,7 +3895,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>  			new_timeo = min(new_timeo, t);
>  			break;
>  		}
> -		list_move(&dp->dl_recall_lru, &reaplist);
> +		unhash_delegation_locked(dp);
> +		list_add(&dp->dl_recall_lru, &reaplist);
>  	}
>  	spin_unlock(&state_lock);
>  	list_for_each_safe(pos, next, &reaplist) {
> @@ -5369,7 +5371,8 @@ static u64 nfsd_find_all_delegations(struct nfs4_client *clp, u64 max,
>  			 * don't monkey with it now that we are.
>  			 */
>  			++dp->dl_time;
> -			list_move(&dp->dl_recall_lru, victims);
> +			unhash_delegation_locked(dp);
> +			list_add(&dp->dl_recall_lru, victims);
>  		}
>  		if (++count == max)
>  			break;
> @@ -5624,12 +5627,14 @@ nfs4_state_shutdown_net(struct net *net)
>  	spin_lock(&state_lock);
>  	list_for_each_safe(pos, next, &nn->del_recall_lru) {
>  		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
> -		list_move(&dp->dl_recall_lru, &reaplist);
> +		unhash_delegation_locked(dp);
> +		list_add(&dp->dl_recall_lru, &reaplist);
>  	}
>  	spin_unlock(&state_lock);
>  	list_for_each_safe(pos, next, &reaplist) {
>  		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
> -		destroy_delegation(dp);
> +		list_del_init(&dp->dl_recall_lru);
> +		nfs4_put_delegation(dp);
>  	}
>  
>  	nfsd4_client_tracking_exit(net);
> -- 
> 1.9.3
>