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 /*
36  * page->flags layout:
37  *
38  * There are five possibilities for how page->flags get laid out.  The first
39  * pair is for the normal case without sparsemem. The second pair is for
40  * sparsemem when there is plenty of space for node and section information.
41  * The last is when there is insufficient space in page->flags and a separate
42  * lookup is necessary.
43  *
44  * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE |             ... | FLAGS |
45  *      " plus space for last_cpupid: |       NODE     | ZONE | LAST_CPUPID ... | FLAGS |
46  * classic sparse with space for node:| SECTION | NODE | ZONE |             ... | FLAGS |
47  *      " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
48  * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
49  */
50 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
51 #define SECTIONS_WIDTH		SECTIONS_SHIFT
52 #else
53 #define SECTIONS_WIDTH		0
54 #endif
55 
56 #define ZONES_WIDTH		ZONES_SHIFT
57 
58 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
59 #define NODES_WIDTH		NODES_SHIFT
60 #else
61 #ifdef CONFIG_SPARSEMEM_VMEMMAP
62 #error "Vmemmap: No space for nodes field in page flags"
63 #endif
64 #define NODES_WIDTH		0
65 #endif
66 
67 #ifdef CONFIG_NUMA_BALANCING
68 #define LAST__PID_SHIFT 8
69 #define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
70 
71 #define LAST__CPU_SHIFT NR_CPUS_BITS
72 #define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
73 
74 #define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
75 #else
76 #define LAST_CPUPID_SHIFT 0
77 #endif
78 
79 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
80 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
81 #else
82 #define LAST_CPUPID_WIDTH 0
83 #endif
84 
85 /*
86  * We are going to use the flags for the page to node mapping if its in
87  * there.  This includes the case where there is no node, so it is implicit.
88  */
89 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
90 #define NODE_NOT_IN_PAGE_FLAGS
91 #endif
92 
93 #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
94 #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
95 #endif
96 
97 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */
98