linux-kernel - Re: [PATCH v4 02/25] mm/memory_hotplug: Allow check_hotplug_memory

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Date:   Wed, 1 Apr 2020 01:48:16 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Alastair D'Silva" <alastair@...ilva.org>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH v4 02/25] mm/memory_hotplug: Allow check_hotplug_memory_addressable
 to be called from drivers

On Sun, Mar 29, 2020 at 10:23 PM Alastair D'Silva <alastair@...ilva.org> wrote:
>
> When setting up OpenCAPI connected persistent memory, the range check may
> not be performed until quite late (or perhaps not at all, if the user does
> not establish a DAX device).
>
> This patch makes the range check callable so we can perform the check while
> probing the OpenCAPI Persistent Memory device.
>
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> Reviewed-by: Andrew Donnellan <ajd@...ux.ibm.com>
> ---
>  include/linux/memory_hotplug.h | 5 +++++
>  mm/memory_hotplug.c            | 4 ++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index f4d59155f3d4..9a19ae0d7e31 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -337,6 +337,11 @@ static inline void __remove_memory(int nid, u64 start, u64 size) {}
>  extern void set_zone_contiguous(struct zone *zone);
>  extern void clear_zone_contiguous(struct zone *zone);
>
> +#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
> +int check_hotplug_memory_addressable(unsigned long pfn,
> +                                    unsigned long nr_pages);
> +#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

Let's move this to include/linux/memory.h with the other
CONFIG_MEMORY_HOTPLUG_SPARSE declarations, and add a dummy
implementation for the CONFIG_MEMORY_HOTPLUG_SPARSE=n case.

Also, this patch can be squashed with the next one, no need for it to
be stand alone.


> +
>  extern void __ref free_area_init_core_hotplug(int nid);
>  extern int __add_memory(int nid, u64 start, u64 size);
>  extern int add_memory(int nid, u64 start, u64 size);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0a54ffac8c68..14945f033594 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -276,8 +276,8 @@ static int check_pfn_span(unsigned long pfn, unsigned long nr_pages,
>         return 0;
>  }
>
> -static int check_hotplug_memory_addressable(unsigned long pfn,
> -                                           unsigned long nr_pages)
> +int check_hotplug_memory_addressable(unsigned long pfn,
> +                                    unsigned long nr_pages)
>  {
>         const u64 max_addr = PFN_PHYS(pfn + nr_pages) - 1;
>
> --
> 2.24.1
>