fs: dlm: change handling of reconnects (ba3ab3ca) · Commits · 戴 / test

This patch changes the handling of reconnects. At first we only close the connection related to the communication failure. If we get a new connection for an already existing connection we close the existing connection and take the new one. This patch improves significantly the stability of tcp connections while running "tcpkill -9 -i $IFACE port 21064" while generating a lot of dlm messages e.g. on a gfs2 mount with many files. My test setup shows that a deadlock is "more" unlikely. Before this patch I wasn't able to get not a deadlock after 5 seconds. After this patch my observation is that it's more likely to survive after 5 seconds and more, but still a deadlock occurs after certain time. My guess is that there are still "segments" inside the tcp writequeue or retransmit queue which get dropped when receiving a tcp reset [1]. Hard to reproduce because the right message need to be inside these queues, which might even be in the 5 first seconds with this patch. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ipv4/tcp_input.c?h=v5.8-rc6#n4122 Signed-off-by:

Alexander Aring <aahringo@redhat.com> Signed-off-by:

David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

+10 −15

Original line number	Diff line number	Diff line
		@@ -713,7 +713,7 @@ out_resched:
		out_close:
		mutex_unlock(&con->sock_mutex);
		if (ret != -EAGAIN) {
		close_connection(con, true, true, false);
		close_connection(con, false, true, false);
		/* Reconnect when there is something to send */
		}
		/* Don't return success if we really got EOF */
		@@ -804,22 +804,17 @@ static int accept_from_sock(struct connection *con)
		INIT_WORK(&othercon->swork, process_send_sockets);
		INIT_WORK(&othercon->rwork, process_recv_sockets);
		set_bit(CF_IS_OTHERCON, &othercon->flags);
		} else {
		/* close other sock con if we have something new */
		close_connection(othercon, false, true, false);
		}

		mutex_lock_nested(&othercon->sock_mutex, 2);
		if (!othercon->sock) {
		newcon->othercon = othercon;
		add_sock(newsock, othercon);
		addcon = othercon;
		mutex_unlock(&othercon->sock_mutex);
		}
		else {
		printk("Extra connection from node %d attempted\n", nodeid);
		result = -EAGAIN;
		mutex_unlock(&othercon->sock_mutex);
		mutex_unlock(&newcon->sock_mutex);
		goto accept_err;
		}
		}
		else {
		newcon->rx_action = receive_from_sock;
		/* accept copies the sk after we've saved the callbacks, so we
		@@ -1415,7 +1410,7 @@ out:

		send_error:
		mutex_unlock(&con->sock_mutex);
		close_connection(con, true, false, true);
		close_connection(con, false, false, true);
		/* Requeue the send work. When the work daemon runs again, it will try
		a new connection, then call this function again. */
		queue_work(send_workqueue, &con->swork);

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