Re: [PATCH] Revert "mm: remove __GFP_NO_KSWAPD"

Andrew Morton
2012-11-20T20:18:20Z

On Tue, 20 Nov 2012 13:18:19 +0400
Glauber Costa <glommer@parallels.com> wrote:

> On 11/12/2012 03:37 PM, Mel Gorman wrote:
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index 02c1c971..d0a7967 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -31,6 +31,7 @@ struct vm_area_struct;
> > #define ___GFP_THISNODE 0x40000u
> > #define ___GFP_RECLAIMABLE 0x80000u
> > #define ___GFP_NOTRACK 0x200000u
> > +#define ___GFP_NO_KSWAPD 0x400000u
> > #define ___GFP_OTHER_NODE 0x800000u
> > #define ___GFP_WRITE 0x1000000u
>
> Keep in mind that this bit has been reused in -mm.
> If this patch needs to be reverted, we'll need to first change
> the definition of __GFP_KMEMCG (and __GFP_BITS_SHIFT as a result), or it
> would break things.

I presently have

/* Plain integer GFP bitmasks. Do not use this directly. */
#define ___GFP_DMA 0x01u
#define ___GFP_HIGHMEM 0x02u
#define ___GFP_DMA32 0x04u
#define ___GFP_MOVABLE 0x08u
#define ___GFP_WAIT 0x10u
#define ___GFP_HIGH 0x20u
#define ___GFP_IO 0x40u
#define ___GFP_FS 0x80u
#define ___GFP_COLD 0x100u
#define ___GFP_NOWARN 0x200u
#define ___GFP_REPEAT 0x400u
#define ___GFP_NOFAIL 0x800u
#define ___GFP_NORETRY 0x1000u
#define ___GFP_MEMALLOC 0x2000u
#define ___GFP_COMP 0x4000u
#define ___GFP_ZERO 0x8000u
#define ___GFP_NOMEMALLOC 0x10000u
#define ___GFP_HARDWALL 0x20000u
#define ___GFP_THISNODE 0x40000u
#define ___GFP_RECLAIMABLE 0x80000u
#define ___GFP_KMEMCG 0x100000u
#define ___GFP_NOTRACK 0x200000u
#define ___GFP_NO_KSWAPD 0x400000u
#define ___GFP_OTHER_NODE 0x800000u
#define ___GFP_WRITE 0x1000000u

and

#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))

Which I think is OK?

I'd forgotten about __GFP_BITS_SHIFT. Should we do this?

--- a/include/linux/gfp.h~a
+++ a/include/linux/gfp.h
@@ -35,6 +35,7 @@ struct vm_area_struct;
#define ___GFP_NO_KSWAPD 0x400000u
#define ___GFP_OTHER_NODE 0x800000u
#define ___GFP_WRITE 0x1000000u
+/* If the above are modified, __GFP_BITS_SHIFT may need updating */

/*
* GFP bitmasks..
_