1 #ifndef PAGE_FLAGS_LAYOUT_H
2 #define PAGE_FLAGS_LAYOUT_H
4 #include <linux/numa.h>
5 #include <generated/bounds.h>
8 * When a memory allocation must conform to specific limitations (such
9 * as being suitable for DMA) the caller will pass in hints to the
10 * allocator in the gfp_mask, in the zone modifier bits. These bits
11 * are used to select a priority ordered list of memory zones which
12 * match the requested limits. See gfp_zone() in include/linux/gfp.h
16 #elif MAX_NR_ZONES <= 2
18 #elif MAX_NR_ZONES <= 4
21 #error ZONES_SHIFT -- too many zones configured adjust calculation
24 #ifdef CONFIG_SPARSEMEM
25 #include <asm/sparsemem.h>
27 /* SECTION_SHIFT #bits space required to store a section # */
28 #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
30 #endif /* CONFIG_SPARSEMEM */
35 * There are three possibilities for how page->flags get
36 * laid out. The first is for the normal case, without
37 * sparsemem. The second is for sparsemem when there is
38 * plenty of space for node and section. The last is when
39 * we have run out of space and have to fall back to an
40 * alternate (slower) way of determining the node.
42 * No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
43 * classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
44 * classic sparse no space for node: | SECTION | ZONE | ... | FLAGS |
46 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
47 #define SECTIONS_WIDTH SECTIONS_SHIFT
49 #define SECTIONS_WIDTH 0
52 #define ZONES_WIDTH ZONES_SHIFT
54 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
55 #define NODES_WIDTH NODES_SHIFT
57 #ifdef CONFIG_SPARSEMEM_VMEMMAP
58 #error "Vmemmap: No space for nodes field in page flags"
64 * We are going to use the flags for the page to node mapping if its in
65 * there. This includes the case where there is no node, so it is implicit.
67 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
68 #define NODE_NOT_IN_PAGE_FLAGS
71 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */