Re: [PATCH v2] docs: pagemap: fix flags location, member name and sample code

[Lorenzo Stoakes]

On Sat, Jun 27, 2026 at 12:27:10AM +0800, Zenghui Yu wrote:
> The userland visible page flags (KPF_*) were initially moved to
> include/linux/kernel-page-flags.h in commit 1a9b5b7fe0c5 ("mm: export
> stable page flags"), and later moved to
> include/uapi/linux/kernel-page-flags.h in commit 607ca46e97a1 ("UAPI:
> (Scripted) Disintegrate include/linux").  Update the doc to reflect the
> current location of these flags.
>
> The member @walk_end of struct pm_scan_arg {} was wrongly written as
> "end_walk".
>
> The first sample code of the PAGEMAP_SCAN ioctl wrongly used the
> PM_SCAN_CHECK_WPASYNC flag twice, instead of the PM_SCAN_WP_MATCHING flag.
> The second one included the wrong category in the required mask -
> PAGE_IS_FILE should be used instead of PAGE_IS_SWAPPED as per the
> intention.
>
> Fix them all together.
>
> Signed-off-by: Zenghui Yu <zenghui.yu@xxxxxxxxx>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

> ---
>
> * From v1 [1]:
>   - drop PAGE_IS_SWAPPED in .category_mask (David)
>   - fix typo in commit message (David)
>   - didn't collect SeongJae's R-b (as the content has changed anyway) but
>     thank you for that!
>
> [1] https://lore.kernel.org/20260625174447.24292-1-zenghui.yu@xxxxxxxxx
>
>  Documentation/admin-guide/mm/pagemap.rst | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
> index c57e61b5d8aa..20e3fe76f099 100644
> --- a/Documentation/admin-guide/mm/pagemap.rst
> +++ b/Documentation/admin-guide/mm/pagemap.rst
> @@ -67,7 +67,7 @@ number of times a page is mapped.
>   * ``/proc/kpageflags``.  This file contains a 64-bit set of flags for each
>     page, indexed by PFN.
>
> -   The flags are (from ``fs/proc/page.c``, above kpageflags_read):
> +   The flags are (from ``include/uapi/linux/kernel-page-flags.h``):
>
>      0. LOCKED
>      1. ERROR
> @@ -264,7 +264,7 @@ The ``struct pm_scan_arg`` is used as the argument of the IOCTL.
>      provided or not.
>   3. The range is specified through ``start`` and ``end``.
>   4. The walk can abort before visiting the complete range such as the user buffer
> -    can get full etc. The walk ending address is specified in``end_walk``.
> +    can get full etc. The walk ending address is specified in ``walk_end``.
>   5. The output buffer of ``struct page_region`` array and size is specified in
>      ``vec`` and ``vec_len``.
>   6. The optional maximum requested pages are specified in the ``max_pages``.
> @@ -275,7 +275,7 @@ Find pages which have been written and WP them as well::
>
>     struct pm_scan_arg arg = {
>     .size = sizeof(arg),
> -   .flags = PM_SCAN_CHECK_WPASYNC | PM_SCAN_CHECK_WPASYNC,
> +   .flags = PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC,
>     ..
>     .category_mask = PAGE_IS_WRITTEN,
>     .return_mask = PAGE_IS_WRITTEN,
> @@ -288,7 +288,7 @@ present or huge::
>     .size = sizeof(arg),
>     .flags = 0,
>     ..
> -   .category_mask = PAGE_IS_WRITTEN | PAGE_IS_SWAPPED,
> +   .category_mask = PAGE_IS_WRITTEN | PAGE_IS_FILE,
>     .category_inverted = PAGE_IS_SWAPPED,
>     .category_anyof_mask = PAGE_IS_PRESENT | PAGE_IS_HUGE,
>     .return_mask = PAGE_IS_WRITTEN | PAGE_IS_SWAPPED |
> --
> 2.53.0
>