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netdev: fold name hash properly (v3)

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The full_name_hash function does not produce well distributed values in
the lower bits, so most code uses hash_32() to fold it.  This is really
a bug introduced when name hashing was added, back in 2.5 when I added
name hashing.

hash_32 is all that is needed since full_name_hash returns unsigned int
which is only 32 bits on 64 bit platforms.

Also, there is no point in using hash_32 on ifindex, because the is naturally
sequential and usually well distributed.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
stephen hemminger 2009-11-10 07:20:34 +00:00 committed by David S. Miller
parent 7e5ca6a22d
commit 08e9897d51
1 changed files with 2 additions and 1 deletions
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3
net/core/dev.c
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@ -79,6 +79,7 @@
#include <linux/cpu.h> #include <linux/cpu.h>
#include <linux/types.h> #include <linux/types.h>
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/hash.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/mutex.h> #include <linux/mutex.h>
#include <linux/string.h> #include <linux/string.h>
@ -196,7 +197,7 @@ EXPORT_SYMBOL(dev_base_lock);
static inline struct hlist_head *dev_name_hash(struct net *net, const char *name) static inline struct hlist_head *dev_name_hash(struct net *net, const char *name)
{ {
unsigned hash = full_name_hash(name, strnlen(name, IFNAMSIZ)); unsigned hash = full_name_hash(name, strnlen(name, IFNAMSIZ));
return &net->dev_name_head[hash & (NETDEV_HASHENTRIES - 1)]; return &net->dev_name_head[hash_32(hash, NETDEV_HASHBITS)];
} }
static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex) static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)