Re: [PATCH 2/7] mark root hnode explicitly

[Jamal Hadi Salim]

On 2018-09-06 6:59 a.m., Al Viro wrote:

On Thu, Sep 06, 2018 at 06:34:00AM -0400, Jamal Hadi Salim wrote:

On 2018-09-06 6:28 a.m., Jamal Hadi Salim wrote:

[..]

Point, and that one is IMO enough to give up on using ->flags for
that.  How about simply

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 3f985f29ef30..d14048e38b5c 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -84,6 +84,7 @@ struct tc_u_hnode {
        int                     refcnt;
        unsigned int            divisor;
        struct idr              handle_idr;
+       bool                    is_root;
        struct rcu_head         rcu;
        u32                     flags;
        /* The 'ht' field MUST be the last field in structure to allow for
@@ -377,6 +378,7 @@ static int u32_init(struct tcf_proto *tp)
        root_ht->refcnt++;
        root_ht->handle = tp_c ? gen_new_htid(tp_c, root_ht) : 0x80000000;
        root_ht->prio = tp->prio;
+       root_ht->is_root = true;
        idr_init(&root_ht->handle_idr);

if (tp_c == NULL) {

@@ -693,7 +695,7 @@ static int u32_delete(struct tcf_proto *tp, void *arg, bool 
*last,
                goto out;
        }

- if (root_ht == ht) {

+       if (ht->is_root) {
                NL_SET_ERR_MSG_MOD(extack, "Not allowed to delete root node");
                return -EINVAL;
        }
@@ -795,6 +797,10 @@ static int u32_set_parms(struct net *net, struct tcf_proto 
*tp,
                                NL_SET_ERR_MSG_MOD(extack, "Link hash table not 
found");
                                return -EINVAL;
                        }
+                       if (ht_down->is_root) {
+                               NL_SET_ERR_MSG_MOD(extack, "Not linking to root 
node");
+                               return -EINVAL;
+                       }
                        ht_down->refcnt++;

Looks good to me ;->

cheers,
jamal