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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@deltatee.com
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Logan Gunthorpe 2018-12-14 14:16:53 -08:00 committed by Linus Torvalds
parent 5b5260902a
commit d1402fc708
4 changed files with 6 additions and 17 deletions
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9
arch/arm64/include/asm/memory.h
View File

@ -34,15 +34,6 @@
*/
#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

8
arch/arm64/mm/init.c
View File

@ -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;
/*

1
include/asm-generic/fixmap.h
View File

@ -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)

5
include/linux/mm_types.h
View File

@ -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)