[PATCH v6 6/8] nbd: factor out a nbd_genl_foreach_sock

The NBD_ATTR_SOCKETS walk is duplicated in nbd_genl_connect (add sockets)
and nbd_genl_reconfigure (reconnect).  Factor out a single helper that
walks the list and calls a callback per fd; with a NULL callback it is a
pure counter, used by a later patch to learn nr_hw_queues before the
device exists.  Returns the number of fds walked (>= 0) or a negative
errno; a callback >0 will stops early.

Signed-off-by: Yang Erkun <[email protected]>
---
 drivers/block/nbd.c | 131 ++++++++++++++++++++++----------------------
 1 file changed, 66 insertions(+), 65 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 66f1b3263b94..c080bb95653b 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1399,11 +1399,12 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
 
 		atomic_inc(&config->live_connections);
 		wake_up(&config->conn_wait);
+		dev_info(nbd_to_dev(nbd), "reconnected socket\n");
 		return 0;
 	}
 	sockfd_put(sock);
 	kfree(args);
-	return -ENOSPC;
+	return 1;
 }
 
 static void nbd_bdev_reset(struct nbd_device *nbd)
@@ -2109,6 +2110,58 @@ static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd)
 	return 0;
 }
 
+/*
+ * Walk the NBD_ATTR_SOCKETS nested list can call @cb for each socket fd.
+ *
+ * Return the number of fds walked, or a negative errno.
+ */
+static int nbd_genl_foreach_sock(struct genl_info *info,
+		int (*cb)(struct nbd_device *nbd, int fd),
+		struct nbd_device *nbd)
+{
+	struct nlattr *attr;
+	int rem, count = 0;
+
+	if (!info->attrs[NBD_ATTR_SOCKETS])
+		return 0;
+
+	nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS], rem) {
+		struct nlattr *socks[NBD_SOCK_MAX + 1];
+		int ret;
+
+		if (nla_type(attr) != NBD_SOCK_ITEM) {
+			pr_err("socks must be embedded in a SOCK_ITEM attr\n");
+			return -EINVAL;
+		}
+
+		if (nla_parse_nested_deprecated(socks, NBD_SOCK_MAX,
+						attr,
+						nbd_sock_policy,
+						info->extack)) {
+			pr_err("error processing sock list\n");
+			return -EINVAL;
+		}
+
+		if (!socks[NBD_SOCK_FD])
+			continue;
+
+		count++;
+		if (cb) {
+			ret = cb(nbd, (int)nla_get_u32(socks[NBD_SOCK_FD]));
+			if (ret > 0)
+				return count;
+			if (ret < 0)
+				return ret;
+		}
+	}
+	return count;
+}
+
+static int nbd_genl_connect_sock_cb(struct nbd_device *nbd, int fd)
+{
+	return nbd_add_socket(nbd, fd, true);
+}
+
 static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nbd_device *nbd;
@@ -2228,36 +2281,9 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 		}
 	}
 
-	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) {
-				pr_err("socks must be embedded in a SOCK_ITEM attr\n");
-				ret = -EINVAL;
-				goto out;
-			}
-			ret = nla_parse_nested_deprecated(socks, NBD_SOCK_MAX,
-							  attr,
-							  nbd_sock_policy,
-							  info->extack);
-			if (ret != 0) {
-				pr_err("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_add_socket(nbd, fd, true);
-			if (ret)
-				goto out;
-		}
-	}
+	ret = nbd_genl_foreach_sock(info, nbd_genl_connect_sock_cb, nbd);
+	if (ret < 0)
+		goto out;
 
 	if (info->attrs[NBD_ATTR_BACKEND_IDENTIFIER]) {
 		nbd->backend = nla_strdup(info->attrs[NBD_ATTR_BACKEND_IDENTIFIER],
@@ -2346,6 +2372,11 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
 	return 0;
 }
 
+static int nbd_genl_reconnect_sock_cb(struct nbd_device *nbd, int fd)
+{
+	return nbd_reconnect_socket(nbd, fd);
+}
+
 static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nbd_device *nbd = NULL;
@@ -2442,40 +2473,10 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
 		}
 	}
 
-	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) {
-				pr_err("socks must be embedded in a SOCK_ITEM attr\n");
-				ret = -EINVAL;
-				goto out;
-			}
-			ret = nla_parse_nested_deprecated(socks, NBD_SOCK_MAX,
-							  attr,
-							  nbd_sock_policy,
-							  info->extack);
-			if (ret != 0) {
-				pr_err("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");
-		}
-	}
+	ret = nbd_genl_foreach_sock(info, nbd_genl_reconnect_sock_cb, nbd);
+	/* foreach_sock returns a positive count on success; doit must return 0 */
+	if (ret >= 0)
+		ret = 0;
 out:
 	mutex_unlock(&nbd->config_lock);
 	nbd_config_put(nbd);
-- 
2.52.0