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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: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Josef Bacik 2017-04-06 17:02:04 -04:00 committed by Jens Axboe
parent 2516ab1543
commit 560bc4b399
2 changed files with 61 additions and 5 deletions
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65
drivers/block/nbd.c
View File

@ -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 @@ again:
nsock = config->socks[index];
mutex_lock(&nsock->tx_lock);
if (nsock->dead) {
int old_index = index;
index = find_fallback(nbd, index);
if (index < 0) {
ret = -EIO;
goto out;
}
mutex_unlock(&nsock->tx_lock);
if (index < 0) {
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;
}
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 @@ again:
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;

1
include/uapi/linux/nbd-netlink.h
View File

@ -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)