gfp_zone analysis

I have three zones on my system, DMA, NORMAL, HIGHMEM, Let's figure out how gfp_zone works:

assume that the allocation flags is 0x421 which can be tranlate to:

__GFP_DMA | GFP_HIGH | GFP_REPEAT

which means allocate memory from ZONE_DMA, Will gfp_zone be able to get ZONE_DMA from gfp flags?

Let's continue:

#define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE)

The GFP_ZONEMASK on my system would be:

GFP_ZONEMASK = 0x03


We have total three zones, so

ZONES_SHIFT = 0x02

GFP_ZONE_TABLE would be:
2 << 0x02 =33=100001

bit = (__GFP_DMA | __GFP_HIGH | __GFP_REPEAT ) & 0x03 = 0x01

static inline enum zone_type gfp_zone(gfp_t flags)
{
       enum zone_type z;
       int bit = flags & GFP_ZONEMASK;

       z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) &
                                        ((1 <<>> bit) & 1);
       else {
#ifdef CONFIG_DEBUG_VM
               BUG_ON((GFP_ZONE_BAD >> bit) & 1);
#endif
       }
       return z;
}

z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) & ((1 << ZONES_SHIFT) - 1)
= (100001 >> (0x01 * 0x02)) & (( 1 << 0x02 -1 )
= 1000 & 0011
= 0
= ZONE_DMA