2 files changed, 133 insertions, 0 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c5f866bcfea6..cb45d799bc5c 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -45,6 +45,7 @@
 
 static DEFINE_IDR(nbd_index_idr);
 static DEFINE_MUTEX(nbd_index_mutex);
+static int nbd_total_devices = 0;
 
 struct nbd_sock {
         struct socket *sock;
@@ -130,6 +131,7 @@ 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 int nbd_genl_status(struct sk_buff *skb, struct genl_info *info);
 static void nbd_dead_link_work(struct work_struct *work);
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
@@ -1457,6 +1459,7 @@ static int nbd_dev_add(int index)
         sprintf(disk->disk_name, "nbd%d", index);
         nbd_reset(nbd);
         add_disk(disk);
+        nbd_total_devices++;
         return index;
 
 out_free_tags:
@@ -1493,12 +1496,22 @@ static struct nla_policy nbd_attr_policy[NBD_ATTR_MAX + 1] = {
         [NBD_ATTR_CLIENT_FLAGS]         =       { .type = NLA_U64 },
         [NBD_ATTR_SOCKETS]              =       { .type = NLA_NESTED},
         [NBD_ATTR_DEAD_CONN_TIMEOUT]    =       { .type = NLA_U64 },
+        [NBD_ATTR_DEVICE_LIST]          =       { .type = NLA_NESTED},
 };
 
 static struct nla_policy nbd_sock_policy[NBD_SOCK_MAX + 1] = {
         [NBD_SOCK_FD]                   =       { .type = NLA_U32 },
 };
 
+/* We don't use this right now since we don't parse the incoming list, but we
+ * still want it here so userspace knows what to expect.
+ */
+static struct nla_policy __attribute__((unused))
+nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
+        [NBD_DEVICE_INDEX]              =       { .type = NLA_U32 },
+        [NBD_DEVICE_CONNECTED]          =       { .type = NLA_U8 },
+};
+
 static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 {
         struct nbd_device *nbd = NULL;
@@ -1764,6 +1777,11 @@ static const struct genl_ops nbd_connect_genl_ops[] = {
                 .policy = nbd_attr_policy,
                 .doit   = nbd_genl_reconfigure,
         },
+        {
+                .cmd    = NBD_CMD_STATUS,
+                .policy = nbd_attr_policy,
+                .doit   = nbd_genl_status,
+        },
 };
 
 static const struct genl_multicast_group nbd_mcast_grps[] = {
@@ -1782,6 +1800,96 @@ static struct genl_family nbd_genl_family __ro_after_init = {
         .n_mcgrps       = ARRAY_SIZE(nbd_mcast_grps),
 };
 
+static int populate_nbd_status(struct nbd_device *nbd, struct sk_buff *reply)
+{
+        struct nlattr *dev_opt;
+        u8 connected = 0;
+        int ret;
+
+        /* This is a little racey, but for status it's ok.  The
+         * reason we don't take a ref here is because we can't
+         * take a ref in the index == -1 case as we would need
+         * to put under the nbd_index_mutex, which could
+         * deadlock if we are configured to remove ourselves
+         * once we're disconnected.
+         */
+        if (refcount_read(&nbd->config_refs))
+                connected = 1;
+        dev_opt = nla_nest_start(reply, NBD_DEVICE_ITEM);
+        if (!dev_opt)
+                return -EMSGSIZE;
+        ret = nla_put_u32(reply, NBD_DEVICE_INDEX, nbd->index);
+        if (ret)
+                return -EMSGSIZE;
+        ret = nla_put_u8(reply, NBD_DEVICE_CONNECTED,
+                         connected);
+        if (ret)
+                return -EMSGSIZE;
+        nla_nest_end(reply, dev_opt);
+        return 0;
+}
+
+static int status_cb(int id, void *ptr, void *data)
+{
+        struct nbd_device *nbd = ptr;
+        return populate_nbd_status(nbd, (struct sk_buff *)data);
+}
+
+static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info)
+{
+        struct nlattr *dev_list;
+        struct sk_buff *reply;
+        void *reply_head;
+        size_t msg_size;
+        int index = -1;
+        int ret = -ENOMEM;
+
+        if (info->attrs[NBD_ATTR_INDEX])
+                index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
+
+        mutex_lock(&nbd_index_mutex);
+
+        msg_size = nla_total_size(nla_attr_size(sizeof(u32)) +
+                                  nla_attr_size(sizeof(u8)));
+        msg_size *= (index == -1) ? nbd_total_devices : 1;
+
+        reply = genlmsg_new(msg_size, GFP_KERNEL);
+        if (!reply)
+                goto out;
+        reply_head = genlmsg_put_reply(reply, info, &nbd_genl_family, 0,
+                                       NBD_CMD_STATUS);
+        if (!reply_head) {
+                nlmsg_free(reply);
+                goto out;
+        }
+
+        dev_list = nla_nest_start(reply, NBD_ATTR_DEVICE_LIST);
+        if (index == -1) {
+                ret = idr_for_each(&nbd_index_idr, &status_cb, reply);
+                if (ret) {
+                        nlmsg_free(reply);
+                        goto out;
+                }
+        } else {
+                struct nbd_device *nbd;
+                nbd = idr_find(&nbd_index_idr, index);
+                if (nbd) {
+                        ret = populate_nbd_status(nbd, reply);
+                        if (ret) {
+                                nlmsg_free(reply);
+                                goto out;
+                        }
+                }
+        }
+        nla_nest_end(reply, dev_list);
+        genlmsg_end(reply, reply_head);
+        genlmsg_reply(reply, info);
+        ret = 0;
+out:
+        mutex_unlock(&nbd_index_mutex);
+        return ret;
+}
+
 static void nbd_connect_reply(struct genl_info *info, int index)
 {
         struct sk_buff *skb;
diff --git a/include/uapi/linux/nbd-netlink.h b/include/uapi/linux/nbd-netlink.h
index c2209c75626c..6f7ca3d63a65 100644
--- a/include/uapi/linux/nbd-netlink.h
+++ b/include/uapi/linux/nbd-netlink.h
@@ -33,11 +33,35 @@ enum {
         NBD_ATTR_CLIENT_FLAGS,
         NBD_ATTR_SOCKETS,
         NBD_ATTR_DEAD_CONN_TIMEOUT,
+        NBD_ATTR_DEVICE_LIST,
         __NBD_ATTR_MAX,
 };
 #define NBD_ATTR_MAX (__NBD_ATTR_MAX - 1)
 
 /*
+ * This is the format for multiple devices with NBD_ATTR_DEVICE_LIST
+ *
+ * [NBD_ATTR_DEVICE_LIST]
+ *   [NBD_DEVICE_ITEM]
+ *     [NBD_DEVICE_INDEX]
+ *     [NBD_DEVICE_CONNECTED]
+ */
+enum {
+        NBD_DEVICE_ITEM_UNSPEC,
+        NBD_DEVICE_ITEM,
+        __NBD_DEVICE_ITEM_MAX,
+};
+#define NBD_DEVICE_ITEM_MAX (__NBD_DEVICE_ITEM_MAX - 1)
+
+enum {
+        NBD_DEVICE_UNSPEC,
+        NBD_DEVICE_INDEX,
+        NBD_DEVICE_CONNECTED,
+        __NBD_DEVICE_MAX,
+};
+#define NBD_DEVICE_ATTR_MAX (__NBD_DEVICE_MAX - 1)
+
+/*
  * This is the format for multiple sockets with NBD_ATTR_SOCKETS
  *
  * [NBD_ATTR_SOCKETS]
@@ -66,6 +90,7 @@ enum {
         NBD_CMD_DISCONNECT,
         NBD_CMD_RECONFIGURE,
         NBD_CMD_LINK_DEAD,
+        NBD_CMD_STATUS,
         __NBD_CMD_MAX,
 };
 #define NBD_CMD_MAX     (__NBD_CMD_MAX - 1)