include/linux/gfp.h: get rid of GFP_ZONE_TABLE/BAD
Subsystems (3)
RFC PATCH v3 1/9 include/linux/gfp.h: get rid of GFP_ZONE_TABLE/BAD
From: Huaisheng Ye <[email protected]>
Replace GFP_ZONE_TABLE and GFP_ZONE_BAD with encoded zone number.
Delete ___GFP_DMA, ___GFP_HIGHMEM and ___GFP_DMA32 from GFP bitmasks, the bottom three bits of GFP mask is reserved for storing encoded zone number.
The encoding method is XOR. Get zone number from enum zone_type, then encode the number with ZONE_NORMAL by XOR operation. The goal is to make sure ZONE_NORMAL can be encoded to zero. So, the compatibility can be guaranteed, such as GFP_KERNEL and GFP_ATOMIC can be used as before.
Reserve __GFP_MOVABLE in bit 3, so that it can continue to be used as a flag. Same as before, __GFP_MOVABLE respresents movable migrate type for ZONE_DMA, ZONE_DMA32, and ZONE_NORMAL. But when it is enabled with __GFP_HIGHMEM, ZONE_MOVABLE shall be returned instead of ZONE_HIGHMEM. __GFP_ZONE_MOVABLE is created to realize it.
With this patch, just enabling __GFP_MOVABLE and __GFP_HIGHMEM is not enough to get ZONE_MOVABLE from gfp_zone. All subsystems should use GFP_HIGHUSER_MOVABLE directly to achieve that.
Decode zone number directly from bottom three bits of flags in gfp_zone. The theory of encoding and decoding is,
A ^ B ^ B = A
Suggested-by Matthew Wilcox <[email protected]>
Signed-off-by Huaisheng Ye <[email protected]>
Cc Andrew Morton <akpm-de/[email protected]>
Cc Vlastimil Babka <[email protected]>
Cc Michal Hocko <mhocko-IBi9RG/[email protected]>
Cc Mel Gorman <[email protected]>
Cc Kate Stewart <[email protected]>
Cc "Levin, Alexander (Sasha Levin)" <[email protected]>
Cc Greg Kroah-Hartman <[email protected]>
Cc Christoph Hellwig <[email protected]>
--- include/linux/gfp.h | 107 ++++++++++------------------------------------------ 1 file changed, 20 insertions(+), 87 deletions(-)
include/linux/gfp.h +20 -87
@@ -16,9 +16,7 @@*/ /* Plain integer GFP bitmasks. Do not use this directly. */ -#define ___GFP_DMA 0x01u -#define ___GFP_HIGHMEM 0x02u -#define ___GFP_DMA32 0x04u +#define ___GFP_ZONE_MASK 0x07u#define ___GFP_MOVABLE 0x08u#define ___GFP_RECLAIMABLE 0x10u#define ___GFP_HIGH 0x20u
@@ -53,11 +51,15 @@* without the underscores and use them consistently. The definitions here may * be used in bit comparisons. */ -#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)OPT_ZONE_HIGHMEM ^ ZONE_NORMAL) +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL)#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE)/* ZONE_MOVABLE allowed */ -#define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE) +#define GFP_ZONEMASK ((__force gfp_t)___GFP_ZONE_MASK | ___GFP_MOVABLE) +/* bottom 3 bits of GFP bitmasks are used for zone number encoded*/ +#define __GFP_ZONE_MASK ((__force gfp_t)___GFP_ZONE_MASK) +#define __GFP_ZONE_MOVABLE \ + ((__force gfp_t)(ZONE_MOVABLE ^ ZONE_NORMAL) | ___GFP_MOVABLE)/* * Page mobility and placement hints
@@ -268,6 +270,13 @@* available and will not wake kswapd/kcompactd on failure. The _LIGHT * version does not attempt reclaim/compaction at all and is by default used * in page fault path, while the non-light is used by khugepaged. +* +* GFP_NORMAL() is used to clear bottom 3 bits of GFP bitmask. Actually it +* returns encoded ZONE_NORMAL bits. +* +* GFP_NORMAL_UNMOVABLE() is similar to GFP_NORMAL, but it clear bottom 4 bits +* of GFP bitmask. Excepting the encoded ZONE_NORMAL bits, it clears MOVABLE +* flags as well. */ #define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM)#define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS)
@@ -279,10 +288,12 @@#define GFP_DMA __GFP_DMA#define GFP_DMA32 __GFP_DMA32#define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) +#define GFP_HIGHUSER_MOVABLE (GFP_USER | __GFP_ZONE_MOVABLE)#define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM)#define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) +#define GFP_NORMAL (gfp) ((gfp) & ~__GFP_ZONE_MASK) +#define GFP_NORMAL_UNMOVABLE (gfp) ((gfp) & ~GFP_ZONEMASK)/* Convert GFP flags to their corresponding migrate type */ #define GFP_MOVABLE_MASK (__GFP_RECLAIMABLE|__GFP_MOVABLE)
@@ -326,87 +337,9 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)#define OPT_ZONE_DMA32 ZONE_NORMAL#endif -/* -* 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 GFP_ZONES_SHIFT -* bits 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+DMA32) -* 0xd => BAD (MOVABLE+DMA32+DMA) -* 0xe => BAD (MOVABLE+DMA32+HIGHMEM) -* 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA) -* -* GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms. -*/ - -#if defined(CONFIG_ZONE_DEVICE ) && (MAX_NR_ZONES -1 ) <=4 -/* ZONE_DEVICE is not a valid GFP zone specifier */ -#define GFP_ZONES_SHIFT 2 -#else -#define GFP_ZONES_SHIFT ZONES_SHIFT -#endif - -#if 16 *GFP_ZONES_SHIFT >BITS_PER_LONG -#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer -#endif - -#define GFP_ZONE_TABLE ( \ - (ZONE_NORMAL << 0 * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA << ___GFP_DMA * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << ___GFP_DMA32 * GFP_ZONES_SHIFT) \ - | (ZONE_NORMAL << ___GFP_MOVABLE * GFP_ZONES_SHIFT) \ - | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * GFP_ZONES_SHIFT) \ - | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * GFP_ZONES_SHIFT)\ - | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * GFP_ZONES_SHIFT)\ -) - -/* -* GFP_ZONE_BAD is a bitmap for all combinations of __GFP_DMA, __GFP_DMA32 -* __GFP_HIGHMEM and __GFP_MOVABLE that are not permitted. One flag per -* entry starting with bit 0. Bit is set if the combination is not -* allowed. -*/ -#define GFP_ZONE_BAD ( \ - 1 << (___GFP_DMA | ___GFP_HIGHMEM) \ - | 1 << (___GFP_DMA | ___GFP_DMA32) \ - | 1 << (___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_DMA | ___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_MOVABLE | ___GFP_HIGHMEM | ___GFP_DMA) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_HIGHMEM) \ - | 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA | ___GFP_HIGHMEM) \ -) -static inline enum zone_type gfp_zone (gfp_t flags) { -enum zone_type z; -int bit = (__force int ) (flags &GFP_ZONEMASK ); - - z = (GFP_ZONE_TABLE >> (bit *GFP_ZONES_SHIFT )) & - ((1 <<GFP_ZONES_SHIFT ) -1 ); -VM_BUG_ON ((GFP_ZONE_BAD >> bit) &1 ); -return z; +return ((__force unsigned int )flags & __GFP_ZONE_MASK) ^ZONE_NORMAL ; }/*
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1.8.3.1