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Commit 560bc4b3 authored by Josef Bacik's avatar Josef Bacik Committed by Jens Axboe
Browse files

nbd: handle dead connections 



Sometimes we like to upgrade our server without making all of our
clients freak out and reconnect.  This patch provides a way to specify a
dead connection timeout to allow us to pause all requests and wait for
new connections to be opened.  With this in place I can take down the
nbd server for less than the dead connection timeout time and bring it
back up and everything resumes gracefully.

Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 2516ab15

drivers/block/nbd.c

+59 −4
Original line number Diff line number Diff line
@@ -77,9 +77,12 @@ struct link_dead_args { 
struct nbd_config {

	u32 flags;

	unsigned long runtime_flags;

	u64 dead_conn_timeout;



	struct nbd_sock **socks;

	int num_connections;

	atomic_t live_connections;

	wait_queue_head_t conn_wait;



	atomic_t recv_threads;

	wait_queue_head_t recv_wq;
@@ -178,8 +181,10 @@ static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock, 
			queue_work(system_wq, &args->work);

		}

	}

	if (!nsock->dead)

	if (!nsock->dead) {

		kernel_sock_shutdown(nsock->sock, SHUT_RDWR);

		atomic_dec(&nbd->config->live_connections);

	}

	nsock->dead = true;

	nsock->pending = NULL;

	nsock->sent = 0;
@@ -257,6 +262,14 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, 
		return BLK_EH_HANDLED;

	}



	/* If we are waiting on our dead timer then we could get timeout

	 * callbacks for our request.  For this we just want to reset the timer

	 * and let the queue side take care of everything.

	 */

	if (!completion_done(&cmd->send_complete)) {

		nbd_config_put(nbd);

		return BLK_EH_RESET_TIMER;

	}

	config = nbd->config;



	if (config->num_connections > 1) {
@@ -665,6 +678,19 @@ static int find_fallback(struct nbd_device *nbd, int index) 
	return new_index;

}



static int wait_for_reconnect(struct nbd_device *nbd)

{

	struct nbd_config *config = nbd->config;

	if (!config->dead_conn_timeout)

		return 0;

	if (test_bit(NBD_DISCONNECTED, &config->runtime_flags))

		return 0;

	wait_event_interruptible_timeout(config->conn_wait,

					 atomic_read(&config->live_connections),

					 config->dead_conn_timeout);

	return atomic_read(&config->live_connections);

}



static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)

{

	struct request *req = blk_mq_rq_from_pdu(cmd);
@@ -691,12 +717,24 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) 
	nsock = config->socks[index];

	mutex_lock(&nsock->tx_lock);

	if (nsock->dead) {

		int old_index = index;

		index = find_fallback(nbd, index);

		mutex_unlock(&nsock->tx_lock);

		if (index < 0) {

			ret = -EIO;

			goto out;

			if (wait_for_reconnect(nbd)) {

				index = old_index;

				goto again;

			}

			/* All the sockets should already be down at this point,

			 * we just want to make sure that DISCONNECTED is set so

			 * any requests that come in that were queue'ed waiting

			 * for the reconnect timer don't trigger the timer again

			 * and instead just error out.

			 */

			sock_shutdown(nbd);

			nbd_config_put(nbd);

			return -EIO;

		}

		mutex_unlock(&nsock->tx_lock);

		goto again;

	}
@@ -809,6 +847,7 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, 
	nsock->sent = 0;

	nsock->cookie = 0;

	socks[config->num_connections++] = nsock;

	atomic_inc(&config->live_connections);



	return 0;

}
@@ -860,6 +899,9 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg) 
		 * need to queue_work outside of the tx_mutex.

		 */

		queue_work(recv_workqueue, &args->work);



		atomic_inc(&config->live_connections);

		wake_up(&config->conn_wait);

		return 0;

	}

	sockfd_put(sock);
@@ -1137,7 +1179,9 @@ static struct nbd_config *nbd_alloc_config(void) 
		return NULL;

	atomic_set(&config->recv_threads, 0);

	init_waitqueue_head(&config->recv_wq);

	init_waitqueue_head(&config->conn_wait);

	config->blksize = 1024;

	atomic_set(&config->live_connections, 0);

	try_module_get(THIS_MODULE);

	return config;

}
@@ -1448,6 +1492,7 @@ static struct nla_policy nbd_attr_policy[NBD_ATTR_MAX + 1] = { 
	[NBD_ATTR_SERVER_FLAGS]		=	{ .type = NLA_U64 },

	[NBD_ATTR_CLIENT_FLAGS]		=	{ .type = NLA_U64 },

	[NBD_ATTR_SOCKETS]		=	{ .type = NLA_NESTED},

	[NBD_ATTR_DEAD_CONN_TIMEOUT]	=	{ .type = NLA_U64 },

};



static struct nla_policy nbd_sock_policy[NBD_SOCK_MAX + 1] = {
@@ -1534,6 +1579,11 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) 
		nbd->tag_set.timeout = timeout * HZ;

		blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);

	}

	if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {

		config->dead_conn_timeout =

			nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);

		config->dead_conn_timeout *= HZ;

	}

	if (info->attrs[NBD_ATTR_SERVER_FLAGS])

		config->flags =

			nla_get_u64(info->attrs[NBD_ATTR_SERVER_FLAGS]);
@@ -1654,6 +1704,11 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) 
		nbd->tag_set.timeout = timeout * HZ;

		blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);

	}

	if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {

		config->dead_conn_timeout =

			nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);

		config->dead_conn_timeout *= HZ;

	}



	if (info->attrs[NBD_ATTR_SOCKETS]) {

		struct nlattr *attr;

include/uapi/linux/nbd-netlink.h

+1 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ enum { 
	NBD_ATTR_SERVER_FLAGS,

	NBD_ATTR_CLIENT_FLAGS,

	NBD_ATTR_SOCKETS,

	NBD_ATTR_DEAD_CONN_TIMEOUT,

	__NBD_ATTR_MAX,

};

#define NBD_ATTR_MAX (__NBD_ATTR_MAX - 1)