Re: [PATCH] mm: kill kmemcheck again

[Michal Hocko]

On Sat 30-09-17 20:02:41, Sasha Levin wrote:
> On Sat, Sep 30, 2017 at 03:57:27PM +0200, Vegard Nossum wrote:
> >On 30 September 2017 at 11:48, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> >> On Wed, 27 Sep 2017 17:02:07 +0200
> >> Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> >>
> >>> > Now that 2 years have passed, and all distros provide gcc that supports
> >>> > KASAN, kill kmemcheck again for the very same reasons.
> >>>
> >>> This is just too large to review manually. How have you generated the
> >>> patch?
> >>
> >> I agree. This needs to be taken out piece by piece, not in one go,
> >> where there could be unexpected fallout.
> >
> >I have a patch from earlier this year that starts by removing the core
> >code and defining all the helpers/flags as no-ops so they can be
> >removed bit by bit at a later time. See the attachment. Pekka signed
> >off on it too.
> >e
> >I never actually submitted this because I was waiting for MSAN to be
> 
> I'm not sure how much value there is in doing it this way. I agree
> that the patch is big, but most of it is simply removing code under
> arch/x86/mm/kmemcheck.
>
> The difference between Vegard's patch and mine is about 300 lines
> (out of 2800+), where those 300 lines are simply removing calls to
> kmemcheck. There are no logic changes. (so something very similar to
> 's/*kmemcheck*//g' would do the trick).

Maybe splitting the patch into three: 1) remove all callers of kmemleak
API and 2) remove arch/x86/mm/kmemcheck/ and 3) remove leftovers would
be slightly easier to review. Maybe 2 and 3 would have some dependencies
so they would have to end up in the same path.

Just my 2c

-- 
Michal Hocko
SUSE Labs