[Devel] [PATCH rh7] x86: arch_free_page() introduced

[Konstantin Khorenko]

Stas, please put reviewer to CC.

Volodya, please review.

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 11/12/2015 09:01 PM, Stanislav Kinsburskiy wrote:
> This patch defines arch_free_page() callback to x86 architecture. The only
> thing it does is pages contents zeroing.
> It's disabled by default. To enable it one should add "zero-free-pages"
> kernel option to kernel boot parameters.
> Note, that kernel boot option handling and enabling of pages zeroing are
> divided. The reason for this is that static keys initialization can't be
> performed during kernel parameters parsing (can't specify, what is the exact
> reason, but kernel just doesn't boot, if static key is incremented on
> parameter callback). Because of this split, actual zeroing is enabled later
> during kernel boot, but still early enough.
> Another thing to notice, is that code is moved to a separate source and header
> files. The reason for source file is all other are not really suitable. The
> reason for header is that asm/page.h cna't be used for this (compile
> dependences).
>
> https://jira.sw.ru/browse/PSBM-33071
>
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> ---
>   arch/x86/include/asm/free_page.h   |   23 +++++++++++++++++++++++
>   arch/x86/include/asm/thread_info.h |    1 +
>   arch/x86/mm/Makefile               |    2 +-
>   arch/x86/mm/free_page.c            |   28 ++++++++++++++++++++++++++++
>   4 files changed, 53 insertions(+), 1 deletion(-)
>   create mode 100644 arch/x86/include/asm/free_page.h
>   create mode 100644 arch/x86/mm/free_page.c
>
> diff --git a/arch/x86/include/asm/free_page.h b/arch/x86/include/asm/free_page.h
> new file mode 100644
> index 0000000..f1be780
> --- /dev/null
> +++ b/arch/x86/include/asm/free_page.h
> @@ -0,0 +1,23 @@
> +#ifndef _ASM_X86_FREE_PAGE_H
> +#define _ASM_X86_FREE_PAGE_H
> +
> +#ifdef __KERNEL__
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <linux/jump_label.h>
> +
> +#define HAVE_ARCH_FREE_PAGE
> +
> +extern struct static_key zero_free_pages;
> +extern void do_zero_pages(struct page *page, int order);
> +
> +static __always_inline void arch_free_page(struct page *page, int order)
> +{
> +	if (static_key_false(&zero_free_pages))
> +		do_zero_pages(page, order);
> +}
> +
> +#endif	// __ASSEMBLY__
> +#endif	// __KERNEL__
> +#endif	// _ASM_X86_FREE_PAGE_H
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index f9513ef..4275318 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -9,6 +9,7 @@
>
>   #include <linux/compiler.h>
>   #include <asm/page.h>
> +#include <asm/free_page.h>
>   #include <asm/types.h>
>
>   /*
> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
> index ac9ca65..5527581 100644
> --- a/arch/x86/mm/Makefile
> +++ b/arch/x86/mm/Makefile
> @@ -1,5 +1,5 @@
>   obj-y	:=  init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
> -	    pat.o pgtable.o physaddr.o gup.o setup_nx.o
> +	    pat.o pgtable.o physaddr.o gup.o setup_nx.o free_page.o
>
>   # Make sure __phys_addr has no stackprotector
>   nostackp := $(call cc-option, -fno-stack-protector)
> diff --git a/arch/x86/mm/free_page.c b/arch/x86/mm/free_page.c
> new file mode 100644
> index 0000000..d5d7e53
> --- /dev/null
> +++ b/arch/x86/mm/free_page.c
> @@ -0,0 +1,28 @@
> +#include <linux/highmem.h>
> +#include <asm/free_page.h>
> +
> +static int zero_data_pages_enabled;
> +struct static_key __initdata zero_free_pages = STATIC_KEY_INIT_FALSE;
> +
> +void do_zero_pages(struct page *page, int order)
> +{
> +	int i;
> +
> +	for (i = 0; i < (1 << order); i++)
> +		clear_highpage(page + i);
> +}
> +
> +static int __init enable_zero_free_pages(char *__unused)
> +{
> +	zero_data_pages_enabled = 1;
> +	return 1;
> +}
> +__setup("zero-free-pages", enable_zero_free_pages);
> +
> +static int __init setup_zero_free_pages(void)
> +{
> +	if (zero_data_pages_enabled)
> +		static_key_slow_inc(&zero_free_pages);
> +	return 0;
> +}
> +early_initcall(setup_zero_free_pages);
>
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