[RFC net-next 5/9] genetlink: add a structure for dump state

[Jakub Kicinski]

Whenever netlink dump uses more than 2 cb->args[] entries
code gets hard to read. We're about to add more state to
ctrl_dumppolicy() so create a structure.

Since the structure is typed and clearly named we can remove
the local fam_id variable and use ctx->fam_id directly.

Signed-off-by: Jakub Kicinski <k...@kernel.org>
---
 net/netlink/genetlink.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 38d8f353dba1..a8001044d8cd 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1102,13 +1102,18 @@ static int genl_ctrl_event(int event, const struct 
genl_family *family,
        return 0;
 }
 
+struct ctrl_dump_policy_ctx {
+       unsigned long state;
+       unsigned int fam_id;
+};
+
 static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
 {
+       struct ctrl_dump_policy_ctx *ctx = (void *)cb->args;
        const struct genl_family *rt;
-       unsigned int fam_id = cb->args[0];
        int err;
 
-       if (!fam_id) {
+       if (!ctx->fam_id) {
                struct nlattr *tb[CTRL_ATTR_MAX + 1];
 
                err = genlmsg_parse(cb->nlh, &genl_ctrl, tb,
@@ -1121,28 +1126,28 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct 
netlink_callback *cb)
                        return -EINVAL;
 
                if (tb[CTRL_ATTR_FAMILY_ID]) {
-                       fam_id = nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
+                       ctx->fam_id = nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
                } else {
                        rt = genl_family_find_byname(
                                nla_data(tb[CTRL_ATTR_FAMILY_NAME]));
                        if (!rt)
                                return -ENOENT;
-                       fam_id = rt->id;
+                       ctx->fam_id = rt->id;
                }
        }
 
-       rt = genl_family_find_byid(fam_id);
+       rt = genl_family_find_byid(ctx->fam_id);
        if (!rt)
                return -ENOENT;
 
        if (!rt->policy)
                return -ENODATA;
 
-       err = netlink_policy_dump_start(rt->policy, rt->maxattr, &cb->args[1]);
+       err = netlink_policy_dump_start(rt->policy, rt->maxattr, &ctx->state);
        if (err)
                return err;
 
-       while (netlink_policy_dump_loop(&cb->args[1])) {
+       while (netlink_policy_dump_loop(&ctx->state)) {
                void *hdr;
                struct nlattr *nest;
 
@@ -1159,7 +1164,7 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct 
netlink_callback *cb)
                if (!nest)
                        goto nla_put_failure;
 
-               if (netlink_policy_dump_write(skb, cb->args[1]))
+               if (netlink_policy_dump_write(skb, ctx->state))
                        goto nla_put_failure;
 
                nla_nest_end(skb, nest);
@@ -1172,7 +1177,6 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct 
netlink_callback *cb)
                break;
        }
 
-       cb->args[0] = fam_id;
        return skb->len;
 }
 
-- 
2.26.2