kernel: add accidentally left out fib trie backport patch

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
SVN-Revision: 45650

diff --git a/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch b/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch
new file mode 100644 (file)
index 0000000..d5fc112
--- /dev/null
+++ b/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch
@@ -0,0 +1,52 @@
+From: Alexander Duyck <alexander.h.duyck@redhat.com>
+Date: Thu, 22 Jan 2015 15:51:08 -0800
+Subject: [PATCH] fib_trie: Use index & (~0ul << n->bits) instead of index >>
+ n->bits
+
+In doing performance testing and analysis of the changes I recently found
+that by shifting the index I had created an unnecessary dependency.
+
+I have updated the code so that we instead shift a mask by bits and then
+just test against that as that should save us about 2 CPU cycles since we
+can generate the mask while the key and pos are being processed.
+
+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
+@@ -961,12 +961,12 @@ static struct tnode *fib_find_node(struc
+                * prefix plus zeros for the bits in the cindex. The index
+                * is the difference between the key and this value.  From
+                * this we can actually derive several pieces of data.
+-               *   if !(index >> bits)
+-               *     we know the value is cindex
+-               *   else
++               *   if (index & (~0ul << bits))
+                *     we have a mismatch in skip bits and failed
++               *   else
++               *     we know the value is cindex
+                */
+-              if (index >> n->bits)
++              if (index & (~0ul << n->bits))
+                       return NULL;
+ 
+               /* we have found a leaf. Prefixes have already been compared */
+@@ -1301,12 +1301,12 @@ int fib_table_lookup(struct fib_table *t
+                * prefix plus zeros for the "bits" in the prefix. The index
+                * is the difference between the key and this value.  From
+                * this we can actually derive several pieces of data.
+-               *   if !(index >> bits)
+-               *     we know the value is child index
+-               *   else
++               *   if (index & (~0ul << bits))
+                *     we have a mismatch in skip bits and failed
++               *   else
++               *     we know the value is cindex
+                */
+-              if (index >> n->bits)
++              if (index & (~0ul << n->bits))
+                       break;
+ 
+               /* we have found a leaf. Prefixes have already been compared */