kernel: backport fib_trie improvements/fixes from 4.0-rc

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 44695

1 files changed, 72 insertions, 0 deletions

diff --git a/target/linux/generic/patches-3.18/080-01-fib_trie-Fix-trie-balancing-issue-if-new-node-pushes.patch b/target/linux/generic/patches-3.18/080-01-fib_trie-Fix-trie-balancing-issue-if-new-node-pushes.patch
new file mode 100644
index 0000000000..4e09f8a189
--- /dev/null
+++ b/target/linux/generic/patches-3.18/080-01-fib_trie-Fix-trie-balancing-issue-if-new-node-pushes.patch
@@ -0,0 +1,72 @@
+From: Alexander Duyck <alexander.h.duyck@redhat.com>
+Date: Wed, 10 Dec 2014 21:49:22 -0800
+Subject: [PATCH] fib_trie: Fix trie balancing issue if new node pushes down
+ existing node
+
+This patch addresses an issue with the level compression of the fib_trie.
+Specifically in the case of adding a new leaf that triggers a new node to
+be added that takes the place of the old node.  The result is a trie where
+the 1 child tnode is on one side and one leaf is on the other which gives
+you a very deep trie.  Below is the script I used to generate a trie on
+dummy0 with a 10.X.X.X family of addresses.
+
+  ip link add type dummy
+  ipval=184549374
+  bit=2
+  for i in `seq 1 23`
+  do
+    ifconfig dummy0:$bit $ipval/8
+    ipval=`expr $ipval - $bit`
+    bit=`expr $bit \* 2`
+  done
+  cat /proc/net/fib_triestat
+
+Running the script before the patch:
+
+	Local:
+		Aver depth:     10.82
+		Max depth:      23
+		Leaves:         29
+		Prefixes:       30
+		Internal nodes: 27
+		  1: 26  2: 1
+		Pointers: 56
+	Null ptrs: 1
+	Total size: 5  kB
+
+After applying the patch and repeating:
+
+	Local:
+		Aver depth:     4.72
+		Max depth:      9
+		Leaves:         29
+		Prefixes:       30
+		Internal nodes: 12
+		  1: 3  2: 2  3: 7
+		Pointers: 70
+	Null ptrs: 30
+	Total size: 4  kB
+
+What this fix does is start the rebalance at the newly created tnode
+instead of at the parent tnode.  This way if there is a gap between the
+parent and the new node it doesn't prevent the new tnode from being
+coalesced with any pre-existing nodes that may have been pushed into one
+of the new nodes child branches.
+
+Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+
+--- a/net/ipv4/fib_trie.c
++++ b/net/ipv4/fib_trie.c
+@@ -1143,8 +1143,9 @@ static struct list_head *fib_insert_node
+ 			put_child(tp, cindex, (struct rt_trie_node *)tn);
+ 		} else {
+ 			rcu_assign_pointer(t->trie, (struct rt_trie_node *)tn);
+-			tp = tn;
+ 		}
++
++		tp = tn;
+ 	}
+ 
+ 	if (tp && tp->pos + tp->bits > 32)