Re: [PATCH 0/3] make pfn walker support ZONE_DEVICE

[Michal Hocko]

On Fri 08-11-19 00:08:03, Toshiki Fukasawa wrote:
> This patch set tries to make pfn walker support ZONE_DEVICE.
> This idea is from the TODO in below patch:
> 
>   commit aad5f69bc161af489dbb5934868bd347282f0764
>   Author: David Hildenbrand <david@xxxxxxxxxx>
>   Date:   Fri Oct 18 20:19:20 2019 -0700
> 
> 	fs/proc/page.c: don't access uninitialized memmaps in fs/proc/page.c
> 
> pfn walker's ZONE_DEVICE support requires capability to identify
> that a memmap has been initialized. The uninitialized cases are 
> as follows:
> 
> 	a) pages reserved for ZONE_DEVICE driver
> 	b) pages currently initializing
> 
> This patch set solves both of them.

Why do we want this? What is the usecase?

> 
> Toshiki Fukasawa (3):
>   procfs: refactor kpage_*_read() in fs/proc/page.c
>   mm: Introduce subsection_dev_map
>   mm: make pfn walker support ZONE_DEVICE
> 
>  fs/proc/page.c           | 155 ++++++++++++++++++++---------------------------
>  include/linux/memremap.h |   6 ++
>  include/linux/mmzone.h   |  19 ++++++
>  mm/memremap.c            |  31 ++++++++++
>  mm/sparse.c              |  32 ++++++++++
>  5 files changed, 154 insertions(+), 89 deletions(-)
> 
> -- 
> 1.8.3.1
> 

-- 
Michal Hocko
SUSE Labs