From: Logan Gunthorpe <logang@xxxxxxxxxxxx> Subject: mm: introduce common STRUCT_PAGE_MAX_SHIFT define This define is used by arm64 to calculate the size of the vmemmap region. It is defined as the log2 of the upper bound on the size of a struct page. We move it into mm_types.h so it can be defined properly instead of set and checked with a build bug. This also allows us to use the same define for riscv. Link: http://lkml.kernel.org/r/20181107205433.3875-2-logang@xxxxxxxxxxxx Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Acked-by: Will Deacon <will.deacon@xxxxxxx> Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/arm64/include/asm/memory.h | 9 --------- arch/arm64/mm/init.c | 8 -------- include/asm-generic/fixmap.h | 1 + include/linux/mm_types.h | 5 +++++ 4 files changed, 6 insertions(+), 17 deletions(-) --- a/arch/arm64/include/asm/memory.h~mm-introduce-common-struct_page_max_shift-define +++ a/arch/arm64/include/asm/memory.h @@ -35,15 +35,6 @@ #define PCI_IO_SIZE SZ_16M /* - * Log2 of the upper bound of the size of a struct page. Used for sizing - * the vmemmap region only, does not affect actual memory footprint. - * We don't use sizeof(struct page) directly since taking its size here - * requires its definition to be available at this point in the inclusion - * chain, and it may not be a power of 2 in the first place. - */ -#define STRUCT_PAGE_MAX_SHIFT 6 - -/* * VMEMMAP_SIZE - allows the whole linear region to be covered by * a struct page array */ --- a/arch/arm64/mm/init.c~mm-introduce-common-struct_page_max_shift-define +++ a/arch/arm64/mm/init.c @@ -610,14 +610,6 @@ void __init mem_init(void) BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64); #endif -#ifdef CONFIG_SPARSEMEM_VMEMMAP - /* - * Make sure we chose the upper bound of sizeof(struct page) - * correctly when sizing the VMEMMAP array. - */ - BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT)); -#endif - if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) { extern int sysctl_overcommit_memory; /* --- a/include/asm-generic/fixmap.h~mm-introduce-common-struct_page_max_shift-define +++ a/include/asm-generic/fixmap.h @@ -16,6 +16,7 @@ #define __ASM_GENERIC_FIXMAP_H #include <linux/bug.h> +#include <linux/mm_types.h> #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT) --- a/include/linux/mm_types.h~mm-introduce-common-struct_page_max_shift-define +++ a/include/linux/mm_types.h @@ -206,6 +206,11 @@ struct page { #endif } _struct_page_alignment; +/* + * Used for sizing the vmemmap region on some architectures + */ +#define STRUCT_PAGE_MAX_SHIFT (order_base_2(sizeof(struct page))) + #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK) #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE) _
