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

Marc Zyngier
2022-07-22T14:16:42Z

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.