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 */
116