On Fri, Nov 29, 2019 at 4:09 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> On Fri, Nov 22, 2019 at 12:27 PM <glider@xxxxxxxxxx> wrote:
> >
> > This is a hack to reduce stackdepot pressure.
>
> I think this patch needs a better description :) Like in the comment below.
>
> >
> > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> > To: Alexander Potapenko <glider@xxxxxxxxxx>
> > Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> > Cc: linux-mm@xxxxxxxxx
> >
> > ---
> >
> > Change-Id: I22a201e7e4f67ed74f8129072f12e5351b26103a
> > ---
> > mm/mmu_gather.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
> > index 7d70e5c78f97..8c5ea2d2e7d5 100644
> > --- a/mm/mmu_gather.c
> > +++ b/mm/mmu_gather.c
> > @@ -1,6 +1,7 @@
> > #include <linux/gfp.h>
> > #include <linux/highmem.h>
> > #include <linux/kernel.h>
> > +#include <linux/kmsan-checks.h>
> > #include <linux/mmdebug.h>
> > #include <linux/mm_types.h>
> > #include <linux/pagemap.h>
> > @@ -206,6 +207,15 @@ void tlb_flush_mmu(struct mmu_gather *tlb)
> > void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
> > unsigned long start, unsigned long end)
> > {
> > + /*
> > + * TODO(glider): struct mmu_gather contains 7 1-bit fields packed into a
>
> Remove TODO?
Will do, thanks!
> > + * 32-bit unsigned int value. The remaining 25 bits remain uninitialized
> > + * and are never used, but KMSAN updates the origin for them in
> > + * zap_pXX_range() in mm/memory.c, thus creating very long origin
> > + * chains. This is technically correct, but consumes too much memory.
> > + * Unpoisoning the whole structure will prevent creating such chains.
> > + */
> > + kmsan_unpoison_shadow(tlb, sizeof(*tlb));
> > tlb->mm = mm;
> >
> > /* Is it from 0 to ~0? */
> > --
> > 2.24.0.432.g9d3f5f5b63-goog
> >
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
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Sitz der Gesellschaft: Hamburg
