include/linux/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) || defined(CONFIG_KASAN_HW_TAGS)
  76 #define KASAN_TAG_WIDTH 8
  77 #else
  78 #define KASAN_TAG_WIDTH 0
  79 #endif
  80
  81 #ifdef CONFIG_NUMA_BALANCING
  82 #define LAST__PID_SHIFT 8
  83 #define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
  84
  85 #define LAST__CPU_SHIFT NR_CPUS_BITS
  86 #define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
  87
  88 #define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
  89 #else
  90 #define LAST_CPUPID_SHIFT 0
  91 #endif
  92
  93 #if ZONES_WIDTH + LRU_GEN_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \
  94         KASAN_TAG_WIDTH + LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  95 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
  96 #else
  97 #define LAST_CPUPID_WIDTH 0
  98 #endif
  99
 100 #if LAST_CPUPID_SHIFT != 0 && LAST_CPUPID_WIDTH == 0
 101 #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
 102 #endif
 103
 104 #if ZONES_WIDTH + LRU_GEN_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \
 105         KASAN_TAG_WIDTH + LAST_CPUPID_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
 106 #error "Not enough bits in page flags"
 107 #endif
 108
 109 /* see the comment on MAX_NR_TIERS */
 110 #define LRU_REFS_WIDTH  min(__LRU_REFS_WIDTH, BITS_PER_LONG - NR_PAGEFLAGS - \
 111                             ZONES_WIDTH - LRU_GEN_WIDTH - SECTIONS_WIDTH - \
 112                             NODES_WIDTH - KASAN_TAG_WIDTH - LAST_CPUPID_WIDTH)
 113
 114 #endif
 115 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */