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 adjust calculation
  25 #endif
  26
  27 #ifdef CONFIG_SPARSEMEM
  28 #include <asm/sparsemem.h>
  29
  30 /* SECTION_SHIFT        #bits space required to store a section # */
  31 #define SECTIONS_SHIFT  (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
  32
  33 #endif /* CONFIG_SPARSEMEM */
  34
  35 #ifndef BUILD_VDSO32_64
  36 /*
  37  * page->flags layout:
  38  *
  39  * There are five possibilities for how page->flags get laid out.  The first
  40  * pair is for the normal case without sparsemem. The second pair is for
  41  * sparsemem when there is plenty of space for node and section information.
  42  * The last is when there is insufficient space in page->flags and a separate
  43  * lookup is necessary.
  44  *
  45  * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE |             ... | FLAGS |
  46  *      " plus space for last_cpupid: |       NODE     | ZONE | LAST_CPUPID ... | FLAGS |
  47  * classic sparse with space for node:| SECTION | NODE | ZONE |             ... | FLAGS |
  48  *      " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
  49  * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
  50  */
  51 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
  52 #define SECTIONS_WIDTH          SECTIONS_SHIFT
  53 #else
  54 #define SECTIONS_WIDTH          0
  55 #endif
  56
  57 #define ZONES_WIDTH             ZONES_SHIFT
  58
  59 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  60 #define NODES_WIDTH             NODES_SHIFT
  61 #else
  62 #ifdef CONFIG_SPARSEMEM_VMEMMAP
  63 #error "Vmemmap: No space for nodes field in page flags"
  64 #endif
  65 #define NODES_WIDTH             0
  66 #endif
  67
  68 #ifdef CONFIG_NUMA_BALANCING
  69 #define LAST__PID_SHIFT 8
  70 #define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
  71
  72 #define LAST__CPU_SHIFT NR_CPUS_BITS
  73 #define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
  74
  75 #define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
  76 #else
  77 #define LAST_CPUPID_SHIFT 0
  78 #endif
  79
  80 #ifdef CONFIG_KASAN_SW_TAGS
  81 #define KASAN_TAG_WIDTH 8
  82 #else
  83 #define KASAN_TAG_WIDTH 0
  84 #endif
  85
  86 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
  87         <= BITS_PER_LONG - NR_PAGEFLAGS
  88 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
  89 #else
  90 #define LAST_CPUPID_WIDTH 0
  91 #endif
  92
  93 #if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \
  94         > BITS_PER_LONG - NR_PAGEFLAGS
  95 #error "Not enough bits in page flags"
  96 #endif
  97
  98 /*
  99  * We are going to use the flags for the page to node mapping if its in
 100  * there.  This includes the case where there is no node, so it is implicit.
 101  */
 102 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
 103 #define NODE_NOT_IN_PAGE_FLAGS
 104 #endif
 105
 106 #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
 107 #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
 108 #endif
 109
 110 #endif
 111 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */