zone gfp_flags generate from ZONE_ constants

PATCH In review Andy Whitcroft 2 participants 2 messages Jan 17, 2006

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Memory management MM core Page allocator MGLRU

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Andy Whitcroft

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2006-01-17 15:52 UTC #0 lore raw

PATCH 1/1 zone gfp_flags generate from ZONE_ constants

zone gfp_flags generate from ZONE_ constants

Change the allocation of the __GFP_zone style zone modifiers so that they are generated from the values of the ZONE_zone definitions. Note that when no zone modifiers are specified select the default zone, typically ZONE_NORMAL.

Signed-off-by Andy Whitcroft <[email protected]>

---
 gfp.h    |   22 ++++++++++++++++------
 mmzone.h |    2 ++
 2 files changed, 18 insertions(+), 6 deletions(-)

include/linux/gfp.h +16 -6

diff -upN reference/include/linux/gfp.h current/include/linux/gfp.h
@@ -11,15 +11,25 @@ struct vm_area_struct;
 /*
  * GFP bitmasks..
  */
-/* Zone modifiers in GFP_ZONEMASK (see linux/mmzone.h - low three bits) */
-#define __GFP_DMA	((__force gfp_t)0x01u)
-#define __GFP_HIGHMEM	((__force gfp_t)0x02u)
+
+/*
+ * Generate the zone modifier bit.  Zone ZONE_DEFAULT doesn't require a bit
+ * as the absence of all zone modifiers implies this zone.  Renormalise the
+ * zone number such that ZONE_DEFAULT is at the bottom and discard it.
+ * These must fit within the bitmask GFP_ZONEMASK defined in linux/mmzone.h.
+ */
+#define __ZONE_BIT(x) (((x) ^ ZONE_DEFAULT) - 1)
+#define ZONE_MODIFIER(x) ((__force gfp_t)(((x) == ZONE_DEFAULT)? (0) : \
+							1UL << __ZONE_BIT(x)))
+
+#define __GFP_DMA	ZONE_MODIFIER(ZONE_DMA)
+#define __GFP_HIGHMEM	ZONE_MODIFIER(ZONE_HIGHMEM)
 #ifdef CONFIG_DMA_IS_DMA32
-#define __GFP_DMA32	((__force gfp_t)0x01)	/* ZONE_DMA is ZONE_DMA32 */
+#define __GFP_DMA32	ZONE_MODIFIER(ZONE_DMA)	/* ZONE_DMA is ZONE_DMA32 */
 #elif BITS_PER_LONG < 64
-#define __GFP_DMA32	((__force gfp_t)0x00)	/* ZONE_NORMAL is ZONE_DMA32 */
+#define __GFP_DMA32	ZONE_MODIFIER(ZONE_NORMAL) /* ZONE_NORMAL is ZONE_DMA32 */
 #else
-#define __GFP_DMA32	((__force gfp_t)0x04)	/* Has own ZONE_DMA32 */
+#define __GFP_DMA32	ZONE_MODIFIER(ZONE_DMA32) /* Has own ZONE_DMA32 */
 #endif
 
 /*

include/linux/mmzone.h +2 -0

diff -upN reference/include/linux/mmzone.h current/include/linux/mmzone.h
@@ -77,6 +77,8 @@ struct per_cpu_pageset {
 #define MAX_NR_ZONES		4	/* Sync this with ZONES_SHIFT */
 #define ZONES_SHIFT		2	/* ceil(log2(MAX_NR_ZONES)) */
 
+/* Select the zone to use when no __GFP flags are selected. */
+#define ZONE_DEFAULT           ZONE_NORMAL
 
 /*
  * When a memory allocation must conform to specific limitations (such

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Andrew Morton

2006-01-17 21:22 UTC #1 lore raw

Quoted 15 lines · Andy Whitcroft

+/*
+ * Generate the zone modifier bit. Zone ZONE_DEFAULT doesn't require a bit
+ * as the absence of all zone modifiers implies this zone. Renormalise the
+ * zone number such that ZONE_DEFAULT is at the bottom and discard it.
+ * These must fit within the bitmask GFP_ZONEMASK defined in linux/mmzone.h.
+ */
+#define __ZONE_BIT(x) (((x) ^ ZONE_DEFAULT) - 1)
+#define ZONE_MODIFIER(x) ((__force gfp_t)(((x) == ZONE_DEFAULT)? (0) : \
+ 1UL << __ZONE_BIT(x)))
+
+#define __GFP_DMA ZONE_MODIFIER(ZONE_DMA)
+#define __GFP_HIGHMEM ZONE_MODIFIER(ZONE_HIGHMEM)
#ifdef CONFIG_DMA_IS_DMA32
-#define __GFP_DMA32 ((__force gfp_t)0x01) /* ZONE_DMA is ZONE_DMA32 */

Quoted 8 lines

+#define __GFP_DMA32 ZONE_MODIFIER(ZONE_DMA) /* ZONE_DMA is ZONE_DMA32 */
#elif BITS_PER_LONG < 64
-#define __GFP_DMA32 ((__force gfp_t)0x00) /* ZONE_NORMAL is ZONE_DMA32 */
+#define __GFP_DMA32 ZONE_MODIFIER(ZONE_NORMAL) /* ZONE_NORMAL is ZONE_DMA32 */
#else
-#define __GFP_DMA32 ((__force gfp_t)0x04) /* Has own ZONE_DMA32 */
+#define __GFP_DMA32 ZONE_MODIFIER(ZONE_DMA32) /* Has own ZONE_DMA32 */
#endif

eek. We often look at the hex value of gfp flags in debug output to work out what sort of allocation is being attempted.

I guess we could print out the values of these things at boot time..