[PATCH 5.15.y 1/5] ipv4: remove fib_devindex_hashfn()

[Sasha Levin <sashal@kernel.org>]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 8a0f62fdeb9ea66ad3d0e959c7c4addbabeac1be ]

fib_devindex_hashfn() converts a 32bit ifindex value to a 8bit hash.

It makes no sense doing this from fib_info_hashfn() and
fib_find_info_nh().

It is better to keep as many bits as possible to let
fib_info_hashfn_result() have better spread.

Only fib_info_devhash_bucket() needs to make this operation,
we can 'inline' trivial fib_devindex_hashfn() in it.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20241004134720.579244-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 8d6cd1885085 ("ipv6: flowlabel: cap duplicate leases per socket")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv4/fib_semantics.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index ccc59b4ca019e..f82d1d93c1b55 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -320,17 +320,12 @@ static inline int nh_comp(struct fib_info *fi, struct fib_info *ofi)
 	return 0;
 }
 
-static inline unsigned int fib_devindex_hashfn(unsigned int val)
-{
-	return hash_32(val, DEVINDEX_HASHBITS);
-}
-
 static struct hlist_head *
 fib_info_devhash_bucket(const struct net_device *dev)
 {
 	u32 val = net_hash_mix(dev_net(dev)) ^ dev->ifindex;
 
-	return &fib_info_devhash[fib_devindex_hashfn(val)];
+	return &fib_info_devhash[hash_32(val, DEVINDEX_HASHBITS)];
 }
 
 static unsigned int fib_info_hashfn_1(int init_val, u8 protocol, u8 scope,
@@ -361,10 +356,10 @@ static inline unsigned int fib_info_hashfn(struct fib_info *fi)
 				fi->fib_priority);
 
 	if (fi->nh) {
-		val ^= fib_devindex_hashfn(fi->nh->id);
+		val ^= fi->nh->id;
 	} else {
 		for_nexthops(fi) {
-			val ^= fib_devindex_hashfn(nh->fib_nh_oif);
+			val ^= nh->fib_nh_oif;
 		} endfor_nexthops(fi)
 	}
 
@@ -379,7 +374,7 @@ static struct fib_info *fib_find_info_nh(struct net *net,
 	struct fib_info *fi;
 	unsigned int hash;
 
-	hash = fib_info_hashfn_1(fib_devindex_hashfn(cfg->fc_nh_id),
+	hash = fib_info_hashfn_1(cfg->fc_nh_id,
 				 cfg->fc_protocol, cfg->fc_scope,
 				 (__force u32)cfg->fc_prefsrc,
 				 cfg->fc_priority);
-- 
2.53.0