On Fri 22-09-17 15:13:56, Reza Arbab wrote:
> The move_pages() syscall can be used to find the numa node where a page
> currently resides. This is not working for device public memory pages,
> which erroneously report -EFAULT (unmapped or zero page).
>
> Enable by adding a FOLL_DEVICE flag for follow_page(), which
> move_pages() will use. This could be done unconditionally, but adding a
> flag seems like a safer change.
I do not understand purpose of this patch. What is the numa node of a
device memory?
> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
> Signed-off-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 1 +
> mm/gup.c | 2 +-
> mm/migrate.c | 2 +-
> 3 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f8c10d3..783cb57 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2368,6 +2368,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
> #define FOLL_MLOCK 0x1000 /* lock present pages */
> #define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
> #define FOLL_COW 0x4000 /* internal GUP flag */
> +#define FOLL_DEVICE 0x8000 /* return device pages */
>
> static inline int vm_fault_to_errno(int vm_fault, int foll_flags)
> {
> diff --git a/mm/gup.c b/mm/gup.c
> index b2b4d42..6fbad70 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -110,7 +110,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
> return NULL;
> }
>
> - page = vm_normal_page(vma, address, pte);
> + page = _vm_normal_page(vma, address, pte, flags & FOLL_DEVICE);
> if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
> /*
> * Only return device mapping pages in the FOLL_GET case since
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 6954c14..dea0ceb 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1690,7 +1690,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
> goto set_status;
>
> /* FOLL_DUMP to ignore special (like zero) pages */
> - page = follow_page(vma, addr, FOLL_DUMP);
> + page = follow_page(vma, addr, FOLL_DUMP | FOLL_DEVICE);
>
> err = PTR_ERR(page);
> if (IS_ERR(page))
> --
> 1.8.3.1
>
--
Michal Hocko
SUSE Labs
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