From: NeilBrown <neilb@cse.unsw.edu.au>
Date: Fri, 6 Jan 2006 08:09:49 +0000 (-0800)
Subject: [PATCH] knfsd: fix hash function for IP addresses on 64bit little-endian machines.
X-Git-Tag: v2.6.16-rc1~936^2~285
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1f1e030bf75774b6a283518e1534d598e14147d4;p=pandora-kernel.git

[PATCH] knfsd: fix hash function for IP addresses on 64bit little-endian machines.

The hash.h hash_long function, when used on a 64 bit machine, ignores many
of the middle-order bits.  (The prime chosen it too bit-sparse).

IP addresses for clients of an NFS server are very likely to differ only in
the low-order bits.  As addresses are stored in network-byte-order, these
bits become middle-order bits in a little-endian 64bit 'long', and so do
not contribute to the hash.  Thus you can have the situation where all
clients appear on one hash chain.

So, until hash_long is fixed (or maybe forever), us a hash function that
works well on IP addresses - xor the bytes together.

Thanks to "Iozone" <capps@iozone.org> for identifying this problem.

Cc: "Iozone" <capps@iozone.org>

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

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