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    SubjectRe: Make RCU dcache work with CONFIG_SECURITY=y
    On Fri, 2011-04-22 at 11:26 -0700, Linus Torvalds wrote:
    > On Thu, Apr 21, 2011 at 5:23 PM, Andi Kleen <> wrote:
    > >
    > > I didn't find good test suites for the security modules, so
    > > there wasn't a lot of testing on this unfortunately
    > > (the selinux one for LTP doesn't seem to work). Some close
    > > review of these changes is needed.
    > >
    > > On the other hand the VFS changes itself are very straight forward
    > > and the 1/1 patch is very straight forward (and a win in itself)
    > >
    > > The bottom line is with this patchkit a CONFIG_SECURITY=y
    > > kernel has as good VFS performance as a kernel with CONFIG_SECURITY
    > > disabled.
    > Gaah. My immediate reaction to the patch-series was "This is great, I
    > was really hoping we could get all those annoying cases sorted out,
    > and I'll queue them for the next merge window".
    > Having then actually read through the patches a bit more, I then got
    > convinced that at least the first patch should probably be applied
    > right away and be marked for stable, since it looks pretty damn
    > obvious to me, and it might already on its own fix the performance
    > regression for some configurations (although realistically I guess few
    > enough people really do the "selinux=0" thing, so the big advantage is
    > making easier to backport the other patches later if we don't do them
    > now).
    > And now I'm vacillating about the two later patches too. They look
    > fine to me, but I really have _zero_ familiarity with selinux and
    > smack internals, so unlike the first patch, I can't go "that looks
    > like the obviously right thing, and it clearly catches all the RCU
    > cases".
    > The "we can't use all the nifty RCU pathwalk in the config that most
    > distros ship by default" is clearly a performance regression, and has
    > meant that it's not been really showing its real advantages for most
    > people. So in that sense, it's a regression fix and thus valid even
    > though we're pretty late in the -rc series.
    > But at the same time, it's also a bit scary.
    > Comments? I'd really like to see/hear feedback like "yeah, this looks
    > really obviously safe" vs "yeah, looks good, but I really don't feel
    > very comfortable with it" from the security people.

    >From an SELinux PoV (And I feel semi confident about SMACK) patch 1/3
    can and should go in as soon as you want. 2/3 looked safe on first
    glance, but I think I can make it smaller and better. I'll try to get a
    version of 2/3 on list in the next couple of days. My first thought was
    that it should probably go in via my SELinux tree next window......


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