Subject: [PATCH v2 net-next 5/7] ipv6: Refactor fib6_drop_pcpu_from

From: David Ahern <[email-masked]>
Date: Sat, 27 Apr 2019 19:27:32 -0700

From: David Ahern <[email-masked]>

Move the existing pcpu walk in fib6_drop_pcpu_from to a new
helper, __fib6_drop_pcpu_from, that can be invoked per fib6_nh
with a reference to the from entries that need to be evicted. If
the passed in from is non-NULL then only entries associated with
that fib6_info are removed (fib entry is deleted); if the from
is NULL are entries are flushed (nexthop is deleted).

For fib6_info entries with builtin fib6_nh (ie., current code)
there is no change in behavior.

Signed-off-by: David Ahern <[email-masked]>
---
 net/ipv6/ip6_fib.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 793830b2965d..aaffe4a653d8 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -874,10 +874,10 @@ static struct fib6_node *fib6_add_1(struct net *net,
 	return ln;
 }
 
-static void fib6_drop_pcpu_from(struct fib6_info *f6i,
-				const struct fib6_table *table)
+static void __fib6_drop_pcpu_from(struct fib6_nh *fib6_nh,
+				  const struct fib6_info *from,
+				  const struct fib6_table *table)
 {
-	struct fib6_nh *fib6_nh = &f6i->fib6_nh;
 	int cpu;
 
 	if (!rcu_access_pointer(fib6_nh->rt6i_pcpu))
@@ -892,17 +892,27 @@ static void fib6_drop_pcpu_from(struct fib6_info *f6i,
 
 		ppcpu_rt = per_cpu_ptr(fib6_nh->rt6i_pcpu, cpu);
 		pcpu_rt = *ppcpu_rt;
-		if (pcpu_rt) {
-			struct fib6_info *from;
+		if (pcpu_rt &&
+		    (!from || rcu_access_pointer(pcpu_rt->from) == from)) {
+			struct fib6_info *pfrom;
 
-			from = rcu_dereference_protected(pcpu_rt->from,
+			pfrom = rcu_dereference_protected(pcpu_rt->from,
 					     lockdep_is_held(&table->tb6_lock));
 			rcu_assign_pointer(pcpu_rt->from, NULL);
-			fib6_info_release(from);
+			fib6_info_release(pfrom);
 		}
 	}
 }
 
+static void fib6_drop_pcpu_from(struct fib6_info *f6i,
+				const struct fib6_table *table)
+{
+	struct fib6_nh *fib6_nh;
+
+	fib6_nh = &f6i->fib6_nh;
+	__fib6_drop_pcpu_from(fib6_nh, f6i, table);
+}
+
 static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
 			  struct net *net)
 {
@@ -930,8 +940,7 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
 				    lockdep_is_held(&table->tb6_lock));
 		}
 
-		if (rt->fib6_nh.rt6i_pcpu)
-			fib6_drop_pcpu_from(rt, table);
+		fib6_drop_pcpu_from(rt, table);
 	}
 }
 
-- 
2.11.0