On Tue, 28 Sep 2010 22:41:42 +0100 Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, Sep 28, 2010 at 02:32:39PM -0700, Andrew Morton wrote: > > > +#define ZT_SHIFT(gfp) ((__force int) (gfp) * ZONES_SHIFT) > > > #define GFP_ZONE_TABLE ( \ > > > - (ZONE_NORMAL << 0 * ZONES_SHIFT) \ > > > - | (OPT_ZONE_DMA << __GFP_DMA * ZONES_SHIFT) \ > > > - | (OPT_ZONE_HIGHMEM << __GFP_HIGHMEM * ZONES_SHIFT) \ > > > - | (OPT_ZONE_DMA32 << __GFP_DMA32 * ZONES_SHIFT) \ > > > - | (ZONE_NORMAL << __GFP_MOVABLE * ZONES_SHIFT) \ > > > - | (OPT_ZONE_DMA << (__GFP_MOVABLE | __GFP_DMA) * ZONES_SHIFT) \ > > > - | (ZONE_MOVABLE << (__GFP_MOVABLE | __GFP_HIGHMEM) * ZONES_SHIFT)\ > > > - | (OPT_ZONE_DMA32 << (__GFP_MOVABLE | __GFP_DMA32) * ZONES_SHIFT)\ > > > + (ZONE_NORMAL << ZT_SHIFT(0)) \ > > > + | (OPT_ZONE_DMA << ZT_SHIFT(__GFP_DMA)) \ > > > + | (OPT_ZONE_HIGHMEM << ZT_SHIFT(__GFP_HIGHMEM)) \ > > > + | (OPT_ZONE_DMA32 << ZT_SHIFT(__GFP_DMA32)) \ > > > + | (ZONE_NORMAL << ZT_SHIFT(__GFP_MOVABLE)) \ > > > + | (OPT_ZONE_DMA << ZT_SHIFT(__GFP_MOVABLE | __GFP_DMA)) \ > > > + | (ZONE_MOVABLE << ZT_SHIFT(__GFP_MOVABLE | __GFP_HIGHMEM)) \ > > > + | (OPT_ZONE_DMA32 << ZT_SHIFT(__GFP_MOVABLE | __GFP_DMA32)) \ > > > ) > > > > hm. I hope these sparse warnings are sufficiently useful to justify > > all the gunk we're adding to support them. > > > > Is it actually finding any bugs? > > FWIW, bitwise or done in the right-hand argumet of shift looks ugly as hell; > what the hell is that code _doing_? There's a nice fat comment a few lines up... /* * GFP_ZONE_TABLE is a word size bitstring that is used for looking up the * zone to use given the lowest 4 bits of gfp_t. Entries are ZONE_SHIFT long * and there are 16 of them to cover all possible combinations of * __GFP_DMA, __GFP_DMA32, __GFP_MOVABLE and __GFP_HIGHMEM. * * The zone fallback order is MOVABLE=>HIGHMEM=>NORMAL=>DMA32=>DMA. * But GFP_MOVABLE is not only a zone specifier but also an allocation * policy. Therefore __GFP_MOVABLE plus another zone selector is valid. * Only 1 bit of the lowest 3 bits (DMA,DMA32,HIGHMEM) can be set to "1". * * bit result * ================= * 0x0 => NORMAL * 0x1 => DMA or NORMAL * 0x2 => HIGHMEM or NORMAL * 0x3 => BAD (DMA+HIGHMEM) * 0x4 => DMA32 or DMA or NORMAL * 0x5 => BAD (DMA+DMA32) * 0x6 => BAD (HIGHMEM+DMA32) * 0x7 => BAD (HIGHMEM+DMA32+DMA) * 0x8 => NORMAL (MOVABLE+0) * 0x9 => DMA or NORMAL (MOVABLE+DMA) * 0xa => MOVABLE (Movable is valid only if HIGHMEM is set too) * 0xb => BAD (MOVABLE+HIGHMEM+DMA) * 0xc => DMA32 (MOVABLE+HIGHMEM+DMA32) * 0xd => BAD (MOVABLE+DMA32+DMA) * 0xe => BAD (MOVABLE+DMA32+HIGHMEM) * 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA) * * ZONES_SHIFT must be <= 2 on 32 bit platforms. */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>