1 #ifndef PAGE_FLAGS_LAYOUT_H 2 #define PAGE_FLAGS_LAYOUT_H 3 4 #include <linux/numa.h> 5 #include <generated/bounds.h> 6 7 /* 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 13 */ 14 #if MAX_NR_ZONES < 2 15 #define ZONES_SHIFT 0 16 #elif MAX_NR_ZONES <= 2 17 #define ZONES_SHIFT 1 18 #elif MAX_NR_ZONES <= 4 19 #define ZONES_SHIFT 2 20 #else 21 #error ZONES_SHIFT -- too many zones configured adjust calculation 22 #endif 23 24 #ifdef CONFIG_SPARSEMEM 25 #include <asm/sparsemem.h> 26 27 /* SECTION_SHIFT #bits space required to store a section # */ 28 #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) 29 30 #endif /* CONFIG_SPARSEMEM */ 31 32 /* 33 * page->flags layout: 34 * 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. 41 * 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 | 45 */ 46 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) 47 #define SECTIONS_WIDTH SECTIONS_SHIFT 48 #else 49 #define SECTIONS_WIDTH 0 50 #endif 51 52 #define ZONES_WIDTH ZONES_SHIFT 53 54 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS 55 #define NODES_WIDTH NODES_SHIFT 56 #else 57 #ifdef CONFIG_SPARSEMEM_VMEMMAP 58 #error "Vmemmap: No space for nodes field in page flags" 59 #endif 60 #define NODES_WIDTH 0 61 #endif 62 63 /* 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. 66 */ 67 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0) 68 #define NODE_NOT_IN_PAGE_FLAGS 69 #endif 70 71 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */ 72