upgrade/downgrade race

Commit Message

Andrew W Elble Sept. 9, 2015, 3:58 p.m. UTC

Or, put into really half-baked (I've only spent an evening looking at
nfs client code) terms, isn't something like this required?

Patch

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 11fe5d7..15b8150 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1923,8 +1923,16 @@  static void nfs4_open_done(struct rpc_task *task, void *calldata)
 		renew_lease(data->o_res.server, data->timestamp);
 		if (!(data->o_res.rflags & NFS4_OPEN_RESULT_CONFIRM))
 			nfs_confirm_seqid(&data->owner->so_seqid, 0);
+
+		if (nfs4_stateid_is_newer(&data->state->open_stateid, &data->o_res.stateid) &&
+		    !can_open_cached(data->state, data->o_arg.fmode, data->o_arg.open_flags)) {
+		    rpc_restart_call_prepare(task);
+		    goto out;
+	        }
 	}
 	data->rpc_done = 1;
+out:
+	return;
 }
 
 static void nfs4_open_release(void *calldata)