> From: owner-linux-mm@xxxxxxxxx [mailto:owner-linux-mm@xxxxxxxxx] On Behalf Of Matthew > Wilcox > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > No, you've made gfp_zone even more complex than it already is. > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > Dear Matthew, The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be equal to ZONE_NORMAL. For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it means that ZONE_MOVABLE shall be returned. That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. I was thinking... Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM or ZONE_MOVABLE shall be returned from gfp_zone. Sincerely, Huaisheng Ye > > static inline enum zone_type gfp_zone(gfp_t flags) > > { > > enum zone_type z; > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > + > > + if (z > OPT_ZONE_HIGHMEM) > > + z = OPT_ZONE_HIGHMEM + > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > - ((1 << GFP_ZONES_SHIFT) - 1); > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > + VM_BUG_ON(z > ZONE_MOVABLE); > > return z; > > }
