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nbd: multicast dead link notifications
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Provide a mechanism to notify userspace that there's been a link problem
on a NBD device.  This will allow userspace to re-establish a connection
and provide the new socket to the device without disrupting the device.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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Josef Bacik authored and Jens Axboe committed Apr 17, 2017
1 parent b7aa3d3 commit 799f9a3
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Showing 2 changed files with 81 additions and 14 deletions.
89 changes: 77 additions & 12 deletions drivers/block/nbd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@ struct nbd_sock {
int sent;
bool dead;
int fallback_index;
int cookie;
};

struct recv_thread_args {
Expand All @@ -61,6 +62,11 @@ struct recv_thread_args {
int index;
};

struct link_dead_args {
struct work_struct work;
int index;
};

#define NBD_TIMEDOUT 0
#define NBD_DISCONNECT_REQUESTED 1
#define NBD_DISCONNECTED 2
Expand Down Expand Up @@ -100,6 +106,7 @@ struct nbd_device {
struct nbd_cmd {
struct nbd_device *nbd;
int index;
int cookie;
struct completion send_complete;
};

Expand All @@ -120,6 +127,7 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd);
static void nbd_dev_dbg_close(struct nbd_device *nbd);
static void nbd_config_put(struct nbd_device *nbd);
static void nbd_connect_reply(struct genl_info *info, int index);
static void nbd_dead_link_work(struct work_struct *work);

static inline struct device *nbd_to_dev(struct nbd_device *nbd)
{
Expand Down Expand Up @@ -152,8 +160,24 @@ static struct device_attribute pid_attr = {
.show = pid_show,
};

static void nbd_mark_nsock_dead(struct nbd_sock *nsock)
static int nbd_disconnected(struct nbd_config *config)
{
return test_bit(NBD_DISCONNECTED, &config->runtime_flags) ||
test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags);
}

static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock,
int notify)
{
if (!nsock->dead && notify && !nbd_disconnected(nbd->config)) {
struct link_dead_args *args;
args = kmalloc(sizeof(struct link_dead_args), GFP_NOIO);
if (args) {
INIT_WORK(&args->work, nbd_dead_link_work);
args->index = nbd->index;
queue_work(system_wq, &args->work);
}
}
if (!nsock->dead)
kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
nsock->dead = true;
Expand Down Expand Up @@ -215,8 +239,7 @@ static void sock_shutdown(struct nbd_device *nbd)
for (i = 0; i < config->num_connections; i++) {
struct nbd_sock *nsock = config->socks[i];
mutex_lock(&nsock->tx_lock);
kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
nbd_mark_nsock_dead(nsock);
nbd_mark_nsock_dead(nbd, nsock, 0);
mutex_unlock(&nsock->tx_lock);
}
dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
Expand Down Expand Up @@ -248,7 +271,14 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
struct nbd_sock *nsock =
config->socks[cmd->index];
mutex_lock(&nsock->tx_lock);
nbd_mark_nsock_dead(nsock);
/* We can have multiple outstanding requests, so
* we don't want to mark the nsock dead if we've
* already reconnected with a new socket, so
* only mark it dead if its the same socket we
* were sent out on.
*/
if (cmd->cookie == nsock->cookie)
nbd_mark_nsock_dead(nbd, nsock, 1);
mutex_unlock(&nsock->tx_lock);
}
blk_mq_requeue_request(req, true);
Expand Down Expand Up @@ -370,6 +400,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
iov_iter_advance(&from, sent);
}
cmd->index = index;
cmd->cookie = nsock->cookie;
request.type = htonl(type);
if (type != NBD_CMD_FLUSH) {
request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
Expand Down Expand Up @@ -458,12 +489,6 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
return 0;
}

static int nbd_disconnected(struct nbd_config *config)
{
return test_bit(NBD_DISCONNECTED, &config->runtime_flags) ||
test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags);
}

/* NULL returned = something went wrong, inform userspace */
static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
{
Expand Down Expand Up @@ -564,7 +589,7 @@ static void recv_work(struct work_struct *work)
struct nbd_sock *nsock = config->socks[args->index];

mutex_lock(&nsock->tx_lock);
nbd_mark_nsock_dead(nsock);
nbd_mark_nsock_dead(nbd, nsock, 1);
mutex_unlock(&nsock->tx_lock);
ret = PTR_ERR(cmd);
break;
Expand Down Expand Up @@ -691,7 +716,7 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
if (ret == -EAGAIN) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Request send failed trying another connection\n");
nbd_mark_nsock_dead(nsock);
nbd_mark_nsock_dead(nbd, nsock, 1);
mutex_unlock(&nsock->tx_lock);
goto again;
}
Expand Down Expand Up @@ -780,6 +805,7 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
nsock->sock = sock;
nsock->pending = NULL;
nsock->sent = 0;
nsock->cookie = 0;
socks[config->num_connections++] = nsock;

return 0;
Expand Down Expand Up @@ -824,6 +850,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
INIT_WORK(&args->work, recv_work);
args->index = i;
args->nbd = nbd;
nsock->cookie++;
mutex_unlock(&nsock->tx_lock);
sockfd_put(old);

Expand Down Expand Up @@ -1682,6 +1709,10 @@ static const struct genl_ops nbd_connect_genl_ops[] = {
},
};

static const struct genl_multicast_group nbd_mcast_grps[] = {
{ .name = NBD_GENL_MCAST_GROUP_NAME, },
};

static struct genl_family nbd_genl_family __ro_after_init = {
.hdrsize = 0,
.name = NBD_GENL_FAMILY_NAME,
Expand All @@ -1690,6 +1721,8 @@ static struct genl_family nbd_genl_family __ro_after_init = {
.ops = nbd_connect_genl_ops,
.n_ops = ARRAY_SIZE(nbd_connect_genl_ops),
.maxattr = NBD_ATTR_MAX,
.mcgrps = nbd_mcast_grps,
.n_mcgrps = ARRAY_SIZE(nbd_mcast_grps),
};

static void nbd_connect_reply(struct genl_info *info, int index)
Expand All @@ -1716,6 +1749,38 @@ static void nbd_connect_reply(struct genl_info *info, int index)
genlmsg_reply(skb, info);
}

static void nbd_mcast_index(int index)
{
struct sk_buff *skb;
void *msg_head;
int ret;

skb = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
if (!skb)
return;
msg_head = genlmsg_put(skb, 0, 0, &nbd_genl_family, 0,
NBD_CMD_LINK_DEAD);
if (!msg_head) {
nlmsg_free(skb);
return;
}
ret = nla_put_u32(skb, NBD_ATTR_INDEX, index);
if (ret) {
nlmsg_free(skb);
return;
}
genlmsg_end(skb, msg_head);
genlmsg_multicast(&nbd_genl_family, skb, 0, 0, GFP_KERNEL);
}

static void nbd_dead_link_work(struct work_struct *work)
{
struct link_dead_args *args = container_of(work, struct link_dead_args,
work);
nbd_mcast_index(args->index);
kfree(args);
}

static int __init nbd_init(void)
{
int i;
Expand Down
6 changes: 4 additions & 2 deletions include/uapi/linux/nbd-netlink.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,9 @@
#ifndef _UAPILINUX_NBD_NETLINK_H
#define _UAPILINUX_NBD_NETLINK_H

#define NBD_GENL_FAMILY_NAME "nbd"
#define NBD_GENL_VERSION 0x1
#define NBD_GENL_FAMILY_NAME "nbd"
#define NBD_GENL_VERSION 0x1
#define NBD_GENL_MCAST_GROUP_NAME "nbd_mc_group"

/* Configuration policy attributes, used for CONNECT */
enum {
Expand Down Expand Up @@ -63,6 +64,7 @@ enum {
NBD_CMD_CONNECT,
NBD_CMD_DISCONNECT,
NBD_CMD_RECONFIGURE,
NBD_CMD_LINK_DEAD,
__NBD_CMD_MAX,
};
#define NBD_CMD_MAX (__NBD_CMD_MAX - 1)
Expand Down

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