nbd: add a reconfigure netlink command

We want to be able to reconnect dead connections to existing block
devices, so add a reconfigure netlink command.  We will also allow users
to change their timeout on the fly, but everything else will require a
disconnect and reconnect.  You won't be able to add more connections
either, simply replace dead connections with new more lively
connections.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

2 files changed, 142 insertions, 0 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index efd2eba37c69..394ea891d909 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -785,6 +785,59 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
         return 0;
 }
 
+static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
+{
+        struct nbd_config *config = nbd->config;
+        struct socket *sock, *old;
+        struct recv_thread_args *args;
+        int i;
+        int err;
+
+        sock = sockfd_lookup(arg, &err);
+        if (!sock)
+                return err;
+
+        args = kzalloc(sizeof(*args), GFP_KERNEL);
+        if (!args) {
+                sockfd_put(sock);
+                return -ENOMEM;
+        }
+
+        for (i = 0; i < config->num_connections; i++) {
+                struct nbd_sock *nsock = config->socks[i];
+
+                if (!nsock->dead)
+                        continue;
+
+                mutex_lock(&nsock->tx_lock);
+                if (!nsock->dead) {
+                        mutex_unlock(&nsock->tx_lock);
+                        continue;
+                }
+                sk_set_memalloc(sock->sk);
+                atomic_inc(&config->recv_threads);
+                refcount_inc(&nbd->config_refs);
+                old = nsock->sock;
+                nsock->fallback_index = -1;
+                nsock->sock = sock;
+                nsock->dead = false;
+                INIT_WORK(&args->work, recv_work);
+                args->index = i;
+                args->nbd = nbd;
+                mutex_unlock(&nsock->tx_lock);
+                sockfd_put(old);
+
+                /* We take the tx_mutex in an error path in the recv_work, so we
+                 * need to queue_work outside of the tx_mutex.
+                 */
+                queue_work(recv_workqueue, &args->work);
+                return 0;
+        }
+        sockfd_put(sock);
+        kfree(args);
+        return -ENOSPC;
+}
+
 /* Reset all properties of an NBD device */
 static void nbd_reset(struct nbd_device *nbd)
 {
@@ -1528,6 +1581,89 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
         return 0;
 }
 
+static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
+{
+        struct nbd_device *nbd = NULL;
+        struct nbd_config *config;
+        int index;
+        int ret = -EINVAL;
+
+        if (!netlink_capable(skb, CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (!info->attrs[NBD_ATTR_INDEX]) {
+                printk(KERN_ERR "nbd: must specify a device to reconfigure\n");
+                return -EINVAL;
+        }
+        index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
+        mutex_lock(&nbd_index_mutex);
+        nbd = idr_find(&nbd_index_idr, index);
+        mutex_unlock(&nbd_index_mutex);
+        if (!nbd) {
+                printk(KERN_ERR "nbd: couldn't find a device at index %d\n",
+                       index);
+                return -EINVAL;
+        }
+
+        if (!refcount_inc_not_zero(&nbd->config_refs)) {
+                dev_err(nbd_to_dev(nbd),
+                        "not configured, cannot reconfigure\n");
+                return -EINVAL;
+        }
+
+        mutex_lock(&nbd->config_lock);
+        config = nbd->config;
+        if (!test_bit(NBD_BOUND, &config->runtime_flags) ||
+            !nbd->task_recv) {
+                dev_err(nbd_to_dev(nbd),
+                        "not configured, cannot reconfigure\n");
+                goto out;
+        }
+
+        if (info->attrs[NBD_ATTR_TIMEOUT]) {
+                u64 timeout = nla_get_u64(info->attrs[NBD_ATTR_TIMEOUT]);
+                nbd->tag_set.timeout = timeout * HZ;
+                blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);
+        }
+
+        if (info->attrs[NBD_ATTR_SOCKETS]) {
+                struct nlattr *attr;
+                int rem, fd;
+
+                nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS],
+                                    rem) {
+                        struct nlattr *socks[NBD_SOCK_MAX+1];
+
+                        if (nla_type(attr) != NBD_SOCK_ITEM) {
+                                printk(KERN_ERR "nbd: socks must be embedded in a SOCK_ITEM attr\n");
+                                ret = -EINVAL;
+                                goto out;
+                        }
+                        ret = nla_parse_nested(socks, NBD_SOCK_MAX, attr,
+                                               nbd_sock_policy);
+                        if (ret != 0) {
+                                printk(KERN_ERR "nbd: error processing sock list\n");
+                                ret = -EINVAL;
+                                goto out;
+                        }
+                        if (!socks[NBD_SOCK_FD])
+                                continue;
+                        fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
+                        ret = nbd_reconnect_socket(nbd, fd);
+                        if (ret) {
+                                if (ret == -ENOSPC)
+                                        ret = 0;
+                                goto out;
+                        }
+                        dev_info(nbd_to_dev(nbd), "reconnected socket\n");
+                }
+        }
+out:
+        mutex_unlock(&nbd->config_lock);
+        nbd_config_put(nbd);
+        return ret;
+}
+
 static const struct genl_ops nbd_connect_genl_ops[] = {
         {
                 .cmd    = NBD_CMD_CONNECT,
@@ -1539,6 +1675,11 @@ static const struct genl_ops nbd_connect_genl_ops[] = {
                 .policy = nbd_attr_policy,
                 .doit   = nbd_genl_disconnect,
         },
+        {
+                .cmd    = NBD_CMD_RECONFIGURE,
+                .policy = nbd_attr_policy,
+                .doit   = nbd_genl_reconfigure,
+        },
 };
 
 static struct genl_family nbd_genl_family __ro_after_init = {
diff --git a/include/uapi/linux/nbd-netlink.h b/include/uapi/linux/nbd-netlink.h
index fd0f4e45f03e..f932f96a7c2f 100644
--- a/include/uapi/linux/nbd-netlink.h
+++ b/include/uapi/linux/nbd-netlink.h
@@ -62,6 +62,7 @@ enum {
         NBD_CMD_UNSPEC,
         NBD_CMD_CONNECT,
         NBD_CMD_DISCONNECT,
+        NBD_CMD_RECONFIGURE,
         __NBD_CMD_MAX,
 };
 #define NBD_CMD_MAX     (__NBD_CMD_MAX - 1)