linux-kernel - Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory

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Message-ID: <CAPcyv4gXso2W0gxaeTsc7g9nTQnkO3WFNZfsdS95NvfYJupnxg@mail.gmail.com>
Date:   Mon, 3 Jul 2017 16:49:18 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jérôme Glisse <jglisse@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        John Hubbard <jhubbard@...dia.com>,
        David Nellans <dnellans@...dia.com>,
        Balbir Singh <bsingharora@...il.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum
 memory_type one

On Mon, Jul 3, 2017 at 2:14 PM, Jérôme Glisse <jglisse@...hat.com> wrote:
> Use consistent name between IORES_DESC and enum memory_type, rename
> MEMORY_DEVICE_PUBLIC to MEMORY_DEVICE_PERSISTENT. This is to free up
> the public name for CDM (cache coherent device memory) for which the
> term public is a better match.
>
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> ---
>  include/linux/memremap.h | 4 ++--
>  kernel/memremap.c        | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 57546a07a558..2299cc2d387d 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -41,7 +41,7 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
>   * Specialize ZONE_DEVICE memory into multiple types each having differents
>   * usage.
>   *
> - * MEMORY_DEVICE_PUBLIC:
> + * MEMORY_DEVICE_PERSISTENT:
>   * Persistent device memory (pmem): struct page might be allocated in different
>   * memory and architecture might want to perform special actions. It is similar
>   * to regular memory, in that the CPU can access it transparently. However,
> @@ -59,7 +59,7 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
>   * include/linux/hmm.h and Documentation/vm/hmm.txt.
>   */
>  enum memory_type {
> -       MEMORY_DEVICE_PUBLIC = 0,
> +       MEMORY_DEVICE_PERSISTENT = 0,
>         MEMORY_DEVICE_PRIVATE,
>  };
>
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index b9baa6c07918..e82456c39a6a 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -350,7 +350,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
>         }
>         pgmap->ref = ref;
>         pgmap->res = &page_map->res;
> -       pgmap->type = MEMORY_DEVICE_PUBLIC;
> +       pgmap->type = MEMORY_DEVICE_PERSISTENT;
>         pgmap->page_fault = NULL;
>         pgmap->page_free = NULL;
>         pgmap->data = NULL;

I think we need a different name. There's nothing "persistent" about
the devm_memremap_pages() path. Why can't they share name, is the only
difference coherence? I'm thinking something like:

MEMORY_DEVICE_PRIVATE
MEMORY_DEVICE_COHERENT /* persistent memory and coherent devices */
MEMORY_DEVICE_IO /* "public", but not coherent */