page-flags-layout.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef PAGE_FLAGS_LAYOUT_H
  3#define PAGE_FLAGS_LAYOUT_H
  4
  5#include <linux/numa.h>
  6#include <generated/bounds.h>
  7
  8/*
  9 * When a memory allocation must conform to specific limitations (such
 10 * as being suitable for DMA) the caller will pass in hints to the
 11 * allocator in the gfp_mask, in the zone modifier bits.  These bits
 12 * are used to select a priority ordered list of memory zones which
 13 * match the requested limits. See gfp_zone() in include/linux/gfp.h
 14 */
 15#if MAX_NR_ZONES < 2
 16#define ZONES_SHIFT 0
 17#elif MAX_NR_ZONES <= 2
 18#define ZONES_SHIFT 1
 19#elif MAX_NR_ZONES <= 4
 20#define ZONES_SHIFT 2
 21#elif MAX_NR_ZONES <= 8
 22#define ZONES_SHIFT 3
 23#else
 24#error ZONES_SHIFT "Too many zones configured"
 25#endif
 26
 27#define ZONES_WIDTH		ZONES_SHIFT
 28
 29#ifdef CONFIG_SPARSEMEM
 30#include <asm/sparsemem.h>
 31#define SECTIONS_SHIFT	(MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
 32#else
 33#define SECTIONS_SHIFT	0
 34#endif
 35
 36#ifndef BUILD_VDSO32_64
 37/*
 38 * page->flags layout:
 39 *
 40 * There are five possibilities for how page->flags get laid out.  The first
 41 * pair is for the normal case without sparsemem. The second pair is for
 42 * sparsemem when there is plenty of space for node and section information.
 43 * The last is when there is insufficient space in page->flags and a separate
 44 * lookup is necessary.
 45 *
 46 * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE |             ... | FLAGS |
 47 *      " plus space for last_cpupid: |       NODE     | ZONE | LAST_CPUPID ... | FLAGS |
 48 * classic sparse with space for node:| SECTION | NODE | ZONE |             ... | FLAGS |
 49 *      " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
 50 * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
 51 */
 52#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
 53#define SECTIONS_WIDTH		SECTIONS_SHIFT
 54#else
 55#define SECTIONS_WIDTH		0
 56#endif
 57
 58#if ZONES_WIDTH + LRU_GEN_WIDTH + SECTIONS_WIDTH + NODES_SHIFT \
 59	<= BITS_PER_LONG - NR_PAGEFLAGS
 60#define NODES_WIDTH		NODES_SHIFT
 61#elif defined(CONFIG_SPARSEMEM_VMEMMAP)
 62#error "Vmemmap: No space for nodes field in page flags"
 63#else
 64#define NODES_WIDTH		0
 65#endif
 66
 67/*
 68 * Note that this #define MUST have a value so that it can be tested with
 69 * the IS_ENABLED() macro.
 70 */
 71#if NODES_SHIFT != 0 && NODES_WIDTH == 0
 72#define NODE_NOT_IN_PAGE_FLAGS	1
 73#endif
 74
 75#if defined(CONFIG_KASAN_SW_TAGS)
 76#define KASAN_TAG_WIDTH 8
 77#elif defined(CONFIG_KASAN_HW_TAGS)
 78#define KASAN_TAG_WIDTH 4
 79#else
 80#define KASAN_TAG_WIDTH 0
 81#endif
 82
 83#ifdef CONFIG_NUMA_BALANCING
 84#define LAST__PID_SHIFT 8
 85#define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
 86
 87#define LAST__CPU_SHIFT NR_CPUS_BITS
 88#define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
 89
 90#define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
 91#else
 92#define LAST_CPUPID_SHIFT 0
 93#endif
 94
 95#if ZONES_WIDTH + LRU_GEN_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \
 96	KASAN_TAG_WIDTH + LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
 97#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
 98#else
 99#define LAST_CPUPID_WIDTH 0
100#endif
101
102#if LAST_CPUPID_SHIFT != 0 && LAST_CPUPID_WIDTH == 0
103#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
104#endif
105
106#if ZONES_WIDTH + LRU_GEN_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \
107	KASAN_TAG_WIDTH + LAST_CPUPID_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
108#error "Not enough bits in page flags"
109#endif
110
111/* see the comment on MAX_NR_TIERS */
112#define LRU_REFS_WIDTH	min(__LRU_REFS_WIDTH, BITS_PER_LONG - NR_PAGEFLAGS - \
113			    ZONES_WIDTH - LRU_GEN_WIDTH - SECTIONS_WIDTH - \
114			    NODES_WIDTH - KASAN_TAG_WIDTH - LAST_CPUPID_WIDTH)
115
116#define NR_NON_PAGEFLAG_BITS	(SECTIONS_WIDTH + NODES_WIDTH + ZONES_WIDTH + \
117				LAST_CPUPID_SHIFT + KASAN_TAG_WIDTH + \
118				LRU_GEN_WIDTH + LRU_REFS_WIDTH)
119
120#define NR_UNUSED_PAGEFLAG_BITS	(BITS_PER_LONG - \
121				(NR_NON_PAGEFLAG_BITS + NR_PAGEFLAGS))
122
123#endif
124#endif /* _LINUX_PAGE_FLAGS_LAYOUT */