On Fri, Jan 2, 2015 at 10:35 AM, Thomas Graf <tg...@noironetworks.com> wrote:
> This patch effectively reverts commit 500f80872645 ("net: ovs: use CRC32
> accelerated flow hash if available"), and other remaining arch_fast_hash()
> users such as from nfsd via commit 6282cd565553 ("NFSD: Don't hand out
> delegations for 30 seconds after recalling them.") where it has been used
> as a hash function for bloom filtering.
>
> While we think that these users are actually not much of concern, it has
> been requested to remove the arch_fast_hash() library bits that arose
> from [1] entirely as per recent discussion [2]. The main argument is that
> using it as a hash may introduce bias due to its linearity (see avalanche
> criterion) and thus makes it less clear (though we tried to document that)
> when this security/performance trade-off is actually acceptable for a
> general purpose library function.
>
> Lets therefore avoid any further confusion on this matter and remove it to
> prevent any future accidental misuse of it. For the time being, this is
> going to make hashing of flow keys a bit more expensive in the ovs case,
> but future work could reevaluate a different hashing discipline.
>
> [1] https://patchwork.ozlabs.org/patch/299369/
> [2] https://patchwork.ozlabs.org/patch/418756/
>
> Upstream: 8754589 ("net: replace remaining users of arch_fast_hash with
> jhash")
> Signed-off-by: Thomas Graf <tg...@noironetworks.com>
LGTM.
Acked-by: Pravin B Shelar <pshe...@nicira.com>
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