Re: [PATCH v2 3/7] mm: Add PG_arch_3 page flag

[Marc Zyngier <maz@kernel.org>]

On Fri, 22 Jul 2022 02:50:29 +0100,
Peter Collingbourne <pcc@google.com> 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.
> 
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Steven Price <steven.price@arm.com>
> [catalin.marinas@arm.com: added flag preserving in __split_huge_page_tail()]
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> ---
>  fs/proc/page.c                 | 1 +
>  include/linux/page-flags.h     | 1 +
>  include/trace/events/mmflags.h | 7 ++++---
>  mm/huge_memory.c               | 1 +
>  4 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index a2873a617ae8..438b8aa7249d 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_64BIT
>  	u |= kpf_copy_bit(k, KPF_ARCH_2,	PG_arch_2);
> +	u |= kpf_copy_bit(k, KPF_ARCH_2,	PG_arch_3);

Are PG_arch_2 and PG_arch_3 supposed to share the same user bit in
/proc/kpageflags? This seems odd.

	M.

-- 
Without deviation from the norm, progress is not possible.

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