[PATCH v4 4/8] mm: Add PG_arch_3 page flag

[Steven Price]

On 21/09/2022 04:51, Peter Collingbourne wrote:
> As with PG_arch_2, this flag is only allowed on 64-bit architectures due
> to the shortage of bits available. It will be used by the arm64 MTE code
> in subsequent patches.

NIT: It's now controlled by CONFIG_ARCH_USES_PG_ARCH_X and not
technically tied to 64-bit (although in practise obviously 32-bit
architectures won't have spare bits).

> 
> Signed-off-by: Peter Collingbourne <pcc at google.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Steven Price <steven.price at arm.com>
> [catalin.marinas at arm.com: added flag preserving in __split_huge_page_tail()]
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>

Reviewed-by: Steven Price <steven.price at arm.com>

> ---
>  fs/proc/page.c                    | 1 +
>  include/linux/kernel-page-flags.h | 1 +
>  include/linux/page-flags.h        | 1 +
>  include/trace/events/mmflags.h    | 1 +
>  mm/huge_memory.c                  | 1 +
>  5 files changed, 5 insertions(+)
> 
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 6f4b4bcb9b0d..43d371e6b366 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -220,6 +220,7 @@ u64 stable_page_flags(struct page *page)
>  	u |= kpf_copy_bit(k, KPF_ARCH,		PG_arch_1);
>  #ifdef CONFIG_ARCH_USES_PG_ARCH_X
>  	u |= kpf_copy_bit(k, KPF_ARCH_2,	PG_arch_2);
> +	u |= kpf_copy_bit(k, KPF_ARCH_3,	PG_arch_3);
>  #endif
>  
>  	return u;
> diff --git a/include/linux/kernel-page-flags.h b/include/linux/kernel-page-flags.h
> index eee1877a354e..859f4b0c1b2b 100644
> --- a/include/linux/kernel-page-flags.h
> +++ b/include/linux/kernel-page-flags.h
> @@ -18,5 +18,6 @@
>  #define KPF_UNCACHED		39
>  #define KPF_SOFTDIRTY		40
>  #define KPF_ARCH_2		41
> +#define KPF_ARCH_3		42
>  
>  #endif /* LINUX_KERNEL_PAGE_FLAGS_H */
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 5dc7977edf9d..c50ce2812f17 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -134,6 +134,7 @@ enum pageflags {
>  #endif
>  #ifdef CONFIG_ARCH_USES_PG_ARCH_X
>  	PG_arch_2,
> +	PG_arch_3,
>  #endif
>  #ifdef CONFIG_KASAN_HW_TAGS
>  	PG_skip_kasan_poison,
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 4673e58a7626..9db52bc4ce19 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -130,6 +130,7 @@ IF_HAVE_PG_HWPOISON(PG_hwpoison,	"hwpoison"	)		\
>  IF_HAVE_PG_IDLE(PG_young,		"young"		)		\
>  IF_HAVE_PG_IDLE(PG_idle,		"idle"		)		\
>  IF_HAVE_PG_ARCH_X(PG_arch_2,		"arch_2"	)		\
> +IF_HAVE_PG_ARCH_X(PG_arch_3,		"arch_3"	)		\
>  IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
>  
>  #define show_page_flags(flags)						\
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 24974a4ce28f..c7c5f9fb226d 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2446,6 +2446,7 @@ static void __split_huge_page_tail(struct page *head, int tail,
>  			 (1L << PG_unevictable) |
>  #ifdef CONFIG_ARCH_USES_PG_ARCH_X
>  			 (1L << PG_arch_2) |
> +			 (1L << PG_arch_3) |
>  #endif
>  			 (1L << PG_dirty) |
>  			 LRU_GEN_MASK | LRU_REFS_MASK));