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authorAlexander Duyck <alexander.h.duyck@redhat.com>2014-12-11 08:49:22 +0300
committerDavid S. Miller <davem@davemloft.net>2014-12-12 18:58:53 +0300
commite962f30297491fddc55a432d5d37df33c83e06f2 (patch)
tree713878612914b7d98a233925ccd45fdf4f34ee99 /net
parent53f6b708f89668cfb5eb9e49384b64b237bae0b2 (diff)
downloadlinux-e962f30297491fddc55a432d5d37df33c83e06f2.tar.xz
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/fib_trie.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index e9cb2588e416..18bcaf2ff2fd 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1143,8 +1143,9 @@ static struct list_head *fib_insert_node(struct trie *t, u32 key, int plen)
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)