On Fri, 22 Nov 2019 at 12:26, <glider@xxxxxxxxxx> wrote: > > This flag is to be used by KMSAN runtime to mark that newly created > memory pages don't need KMSAN metadata backing them. > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > To: Alexander Potapenko <glider@xxxxxxxxxx> > Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > > --- > We can't decide what to do here: > - do we need to conditionally define ___GFP_NO_KMSAN_SHADOW depending on > CONFIG_KMSAN like LOCKDEP does? > - if KMSAN is defined, and LOCKDEP is not, do we want to "compactify" the GFP > bits? A maintainer would know the real answer, but this is my guess: making the behaviour not change without KMSAN would probably be better. It would require some ifdef trickery to deal with LOCKDEP on/off case though. > Change-Id: If5d0352fd5711ad103328e2c185eb885e826423a > --- > include/linux/gfp.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index fb07b503dc45..b4e7963cd94b 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -44,6 +44,7 @@ struct vm_area_struct; > #else > #define ___GFP_NOLOCKDEP 0 > #endif Since this change unconditionally changes GFP_BITS_SHIFT to 25, the #ifdef for GFP_NOLOCKDEP could also go away -- but: see above. > +#define ___GFP_NO_KMSAN_SHADOW 0x1000000u > /* If the above are modified, __GFP_BITS_SHIFT may need updating */ > > /* > @@ -212,12 +213,13 @@ struct vm_area_struct; > #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) > #define __GFP_COMP ((__force gfp_t)___GFP_COMP) > #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) > +#define __GFP_NO_KMSAN_SHADOW ((__force gfp_t)___GFP_NO_KMSAN_SHADOW) Should this be ordered after __GFP_NOLOCKDEP with a brief comment what it does? All of these up to __GFP_ZERO have a doc comment above. > /* Disable lockdep for GFP context tracking */ > #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) > > /* Room for N __GFP_FOO bits */ > -#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP)) > +#define __GFP_BITS_SHIFT (25) > #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) > > /** > -- > 2.24.0.432.g9d3f5f5b63-goog >
