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[1/2] mm: Introduce common STRUCT_PAGE_MAX_SHIFT define

Message ID 20181107173859.24096-2-logang@deltatee.com (mailing list archive)
State New, archived
Headers show
Series Introduce common code for risc-v sparsemem support | expand

Commit Message

Logan Gunthorpe Nov. 7, 2018, 5:38 p.m. UTC 
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.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
---
 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(-)

Comments

Andrew Morton Nov. 7, 2018, 8:11 p.m. UTC | #1 
On Wed,  7 Nov 2018 10:38:58 -0700 Logan Gunthorpe <logang@deltatee.com> wrote:

> 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.
> 
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -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

Well that was lame.

> --- a/include/linux/mm_types.h
> +++ b/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)))

Much better.

Acked-by: Andrew Morton <akpm@linux-foundation.org>
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b96442960aea..f0a5c9531e8b 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -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
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9d9582cac6c4..1a3e411a1d08 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -612,14 +612,6 @@  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;
 		/*
diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
index 827e4d3bbc7a..8cc7b09c1bc7 100644
--- a/include/asm-generic/fixmap.h
+++ b/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)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5ed8f6292a53..2c471a2c43fa 100644
--- a/include/linux/mm_types.h
+++ b/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)