linux-kernel - Re: [PATCH v2 7/9] arm64: kdump: No need to mark crashkernel pages manually PG

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Date:   Mon, 14 Jan 2019 21:22:49 +0530
From:   Bhupesh Sharma <bhsharma@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-m68k@...ts.linux-m68k.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        James Morse <james.morse@....com>,
        Mark Rutland <mark.rutland@....com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Stefan Agner <stefan@...er.ch>,
        Laura Abbott <labbott@...hat.com>,
        Greg Hackmann <ghackmann@...roid.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Kristina Martsenko <kristina.martsenko@....com>,
        CHANDAN VN <chandan.vn@...sung.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: Re: [PATCH v2 7/9] arm64: kdump: No need to mark crashkernel pages
 manually PG_reserved

Hi David,

On Mon, Jan 14, 2019 at 6:30 PM David Hildenbrand <david@...hat.com> wrote:
>
> The crashkernel is reserved via memblock_reserve(). memblock_free_all()
> will call free_low_memory_core_early(), which will go over all reserved
> memblocks, marking the pages as PG_reserved.
>
> So manually marking pages as PG_reserved is not necessary, they are
> already in the desired state (otherwise they would have been handed over
> to the buddy as free pages and bad things would happen).
>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: James Morse <james.morse@....com>
> Cc: Bhupesh Sharma <bhsharma@...hat.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Dave Kleikamp <dave.kleikamp@...cle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Florian Fainelli <f.fainelli@...il.com>
> Cc: Stefan Agner <stefan@...er.ch>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Greg Hackmann <ghackmann@...roid.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Kristina Martsenko <kristina.martsenko@....com>
> Cc: CHANDAN VN <chandan.vn@...sung.com>
> Cc: AKASHI Takahiro <takahiro.akashi@...aro.org>
> Cc: Logan Gunthorpe <logang@...tatee.com>
> Reviewed-by: Matthias Brugger <mbrugger@...e.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/arm64/kernel/machine_kexec.c |  2 +-
>  arch/arm64/mm/init.c              | 27 ---------------------------
>  2 files changed, 1 insertion(+), 28 deletions(-)
>
> diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> index 6f0587b5e941..66b5d697d943 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -321,7 +321,7 @@ void crash_post_resume(void)
>   * but does not hold any data of loaded kernel image.
>   *
>   * Note that all the pages in crash dump kernel memory have been initially
> - * marked as Reserved in kexec_reserve_crashkres_pages().
> + * marked as Reserved as memory was allocated via memblock_reserve().
>   *
>   * In hibernation, the pages which are Reserved and yet "nosave" are excluded
>   * from the hibernation iamge. crash_is_nosave() does thich check for crash
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 7205a9085b4d..c38976b70069 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -118,35 +118,10 @@ static void __init reserve_crashkernel(void)
>         crashk_res.start = crash_base;
>         crashk_res.end = crash_base + crash_size - 1;
>  }
> -
> -static void __init kexec_reserve_crashkres_pages(void)
> -{
> -#ifdef CONFIG_HIBERNATION
> -       phys_addr_t addr;
> -       struct page *page;
> -
> -       if (!crashk_res.end)
> -               return;
> -
> -       /*
> -        * To reduce the size of hibernation image, all the pages are
> -        * marked as Reserved initially.
> -        */
> -       for (addr = crashk_res.start; addr < (crashk_res.end + 1);
> -                       addr += PAGE_SIZE) {
> -               page = phys_to_page(addr);
> -               SetPageReserved(page);
> -       }
> -#endif
> -}
>  #else
>  static void __init reserve_crashkernel(void)
>  {
>  }
> -
> -static void __init kexec_reserve_crashkres_pages(void)
> -{
> -}
>  #endif /* CONFIG_KEXEC_CORE */
>
>  #ifdef CONFIG_CRASH_DUMP
> @@ -586,8 +561,6 @@ void __init mem_init(void)
>         /* this will put all unused low memory onto the freelists */
>         memblock_free_all();
>
> -       kexec_reserve_crashkres_pages();
> -
>         mem_init_print_info(NULL);
>
>         /*
> --
> 2.17.2

LGTM, so:
Reviewed-by: Bhupesh Sharma <bhsharma@...hat.com>