[PATCH v1 net 1/2] ipv6: Remove permanent routes from tb6_gc_hlist when all exceptions expire.

[Kuniyuki Iwashima <kuniyu@google.com>]

Commit 5eb902b8e719 ("net/ipv6: Remove expired routes with a
separated list of routes.") introduced a per-table GC list and
changed GC to iterate over that list instead of traversing
the entire route table.

However, it forgot to add permanent routes to tb6_gc_hlist
when exception routes are added.

Commit cfe82469a00f ("ipv6: add exception routes to GC list
in rt6_insert_exception") fixed that issue but introduced
another one.

Even after all exception routes expire, the permanent routes
remain in tb6_gc_hlist, potentially negating the performance
benefits intended by the initial change.

Let's count gc_args->more before and after rt6_age_exceptions()
and remove the permanent route when the delta is 0.

Note that the next patch will reuse fib6_age_exceptions().

Fixes: cfe82469a00f ("ipv6: add exception routes to GC list in rt6_insert_exception")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/ipv6/ip6_fib.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 9058e71241dc..fadfca49d6b1 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -2348,6 +2348,17 @@ static void fib6_flush_trees(struct net *net)
 /*
  *	Garbage collection
  */
+static void fib6_age_exceptions(struct fib6_info *rt, struct fib6_gc_args *gc_args,
+				unsigned long now)
+{
+	bool may_expire = rt->fib6_flags & RTF_EXPIRES && rt->expires;
+	int old_more = gc_args->more;
+
+	rt6_age_exceptions(rt, gc_args, now);
+
+	if (!may_expire && old_more == gc_args->more)
+		fib6_remove_gc_list(rt);
+}
 
 static int fib6_age(struct fib6_info *rt, struct fib6_gc_args *gc_args)
 {
@@ -2370,7 +2381,7 @@ static int fib6_age(struct fib6_info *rt, struct fib6_gc_args *gc_args)
 	 *	Note, that clones are aged out
 	 *	only if they are not in use now.
 	 */
-	rt6_age_exceptions(rt, gc_args, now);
+	fib6_age_exceptions(rt, gc_args, now);
 
 	return 0;
 }
-- 
2.53.0.473.g4a7958ca14-goog