Re: [PATCH V4 2/4] mm: introduce memory type MEMORY_DEVICE_DEV_DAX

[Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

> 
> Currently, NVDIMM pages will be marked 'PageReserved'. However, unlike
> other reserved PFNs, pages on NVDIMM shall still behave like normal ones
> in many cases, i.e. when used as backend memory of KVM guest. This patch
> introduces a new memory type, MEMORY_DEVICE_DEV_DAX. And set this flag
> while dax driver hotplug the device memory.
> 
> Signed-off-by: Zhang Yi <yi.z.zhang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Signed-off-by: Zhang Yu <yu.c.zhang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Reviewed-by: Jan Kara suse.cz>
> ---
>  drivers/dax/pmem.c       | 1 +
>  include/linux/memremap.h | 8 ++++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
> index fd49b24..fb3f363 100644
> --- a/drivers/dax/pmem.c
> +++ b/drivers/dax/pmem.c
> @@ -111,6 +111,7 @@ static int dax_pmem_probe(struct device *dev)
>                  return rc;
>  
>          dax_pmem->pgmap.ref = &dax_pmem->ref;
> +        dax_pmem->pgmap.type = MEMORY_DEVICE_DEV_DAX;
>          addr = devm_memremap_pages(dev, &dax_pmem->pgmap);
>          if (IS_ERR(addr))
>                  return PTR_ERR(addr);
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index f91f9e7..cd07ca8 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -53,11 +53,19 @@ struct vmem_altmap {
>   * wakeup event whenever a page is unpinned and becomes idle. This
>   * wakeup is used to coordinate physical address space management (ex:
>   * fs truncate/hole punch) vs pinned pages (ex: device dma).
> + *
> + * MEMORY_DEVICE_DEV_DAX:
> + * Device memory that support raw access to persistent memory. Without need
> + * of an intervening filesystem, it could be directed mapped via an mmap
> + * capable character device. Together with the type MEMORY_DEVICE_FS_DAX,
> + * we could distinguish the persistent memory pages from normal ZONE_DEVICE
> + * pages.
>   */
>  enum memory_type {
>          MEMORY_DEVICE_PRIVATE = 1,
>          MEMORY_DEVICE_PUBLIC,
>          MEMORY_DEVICE_FS_DAX,
> +        MEMORY_DEVICE_DEV_DAX,
>  };
>  
>  /*
> --

Reviewed-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

> 2.7.4
> 
>