NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
the ->state_owners rbtree so that it will no longer be used.

If any stateids attached to this open-owner are still in use, and if a
request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.

The state is marked as needing recovery and the nfs4_state_manager()
is scheduled to clean up.  nfs4_state_manager() finds states to be
recovered by walking the state_owners rbtree.  As the open-owner is
not in the rbtree, the bad state is not found so nfs4_state_manager()
completes having done nothing.  The request is then retried, with a
predicatable result (indefinite retries).

If the stateid is for a delegation, this open_owner will be used
to open files when the delegation is returned.  For that to work,
a new open-owner needs to be presented to the server.

This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
in the rbtree but updates the 'create_time' so it looks like a new
open-owner.  With this the indefinite retries no longer happen.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4state.c

@@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 }
 
 static void
-nfs4_drop_state_owner(struct nfs4_state_owner *sp)
-{
-	struct rb_node *rb_node = &sp->so_server_node;
-
-	if (!RB_EMPTY_NODE(rb_node)) {
-		struct nfs_server *server = sp->so_server;
-		struct nfs_client *clp = server->nfs_client;
-
-		spin_lock(&clp->cl_lock);
-		if (!RB_EMPTY_NODE(rb_node)) {
-			rb_erase(rb_node, &server->state_owners);
-			RB_CLEAR_NODE(rb_node);
-		}
-		spin_unlock(&clp->cl_lock);
-	}
+nfs4_reset_state_owner(struct nfs4_state_owner *sp)
+{
+	/* This state_owner is no longer usable, but must
+	 * remain in place so that state recovery can find it
+	 * and the opens associated with it.
+	 * It may also be used for new 'open' request to
+	 * return a delegation to the server.
+	 * So update the 'create_time' so that it looks like
+	 * a new state_owner.  This will cause the server to
+	 * request an OPEN_CONFIRM to start a new sequence.
+	 */
+	sp->so_seqid.create_time = ktime_get();
 }
 
 static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
@@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
 
 	sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
 	if (status == -NFS4ERR_BAD_SEQID)
-		nfs4_drop_state_owner(sp);
+		nfs4_reset_state_owner(sp);
 	if (!nfs4_has_session(sp->so_server->nfs_client))
 		nfs_increment_seqid(status, seqid);
 }