[PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[Sang-Heon Jeon]

zone_absent_pages_in_node() returns 0 when the zone is empty and
otherwise calls __absent_pages_in_range(), which already returns 0 for
an empty range.

So remove it and call __absent_pages_in_range() directly.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 mm/mm_init.c | 20 +++-----------------
 1 file changed, 3 insertions(+), 17 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index d87166a36ee8..1ead4d694099 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1192,22 +1192,9 @@ unsigned long __init absent_pages_in_range(unsigned long start_pfn,
 	return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
 }
 
-/* Return the number of page frames in holes in a zone on a node */
-static unsigned long __init zone_absent_pages_in_node(int nid,
-					unsigned long zone_type,
-					unsigned long zone_start_pfn,
-					unsigned long zone_end_pfn)
-{
-	/* zone is empty, we don't have any absent pages */
-	if (zone_start_pfn == zone_end_pfn)
-		return 0;
-
-	return __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
-}
-
 /*
  * Return the number of pages a zone spans in a node, including holes
- * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
+ * present_pages = zone_spanned_pages_in_node() - __absent_pages_in_range()
  */
 static unsigned long __init zone_spanned_pages_in_node(int nid,
 					unsigned long zone_type,
@@ -1297,9 +1284,8 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
 						     node_end_pfn,
 						     &zone_start_pfn,
 						     &zone_end_pfn);
-		absent = zone_absent_pages_in_node(pgdat->node_id, i,
-						   zone_start_pfn,
-						   zone_end_pfn);
+		absent = __absent_pages_in_range(pgdat->node_id, zone_start_pfn,
+						 zone_end_pfn);
 
 		real_size = spanned - absent;
 
-- 
2.43.0

Re: [PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[Mike Rapoport]

> zone_absent_pages_in_node() returns 0 when the zone is empty and
> otherwise calls __absent_pages_in_range(), which already returns 0 for
> an empty range.

Right, but it loops over memblock memory for an empty zone to get that 0

-- 
Sincerely yours,
Mike.

Re: [PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[Sang-Heon Jeon]

Hi,

On Mon, Aug 31, 2026 at 4:37 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> > zone_absent_pages_in_node() returns 0 when the zone is empty and
> > otherwise calls __absent_pages_in_range(), which already returns 0 for
> > an empty range.
>
> Right, but it loops over memblock memory for an empty zone to get that 0

Indeed. How about adding an early return in __absent_pages_in_range()
to avoid unnecessary iteration? I just want to remove the wrapper,
which never uses its zone_type argument since eb0e5b61369f
("mm/mm_init: don't overlap NORMAL and MOVABLE zones with
kernelcore=mirror")

        unsigned long nr_absent = range_end_pfn - range_start_pfn;
        unsigned long start_pfn, end_pfn;
        int i;

+       if (!nr_absent)
+               return 0;
+
        for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
                start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
                end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);

> --
> Sincerely yours,
> Mike.
>

Re: [PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[Mike Rapoport]

On Mon, Aug 31, 2026 at 08:30:40PM +0900, Sang-Heon Jeon wrote:
> Hi,
> 
> On Mon, Aug 31, 2026 at 4:37 PM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > > zone_absent_pages_in_node() returns 0 when the zone is empty and
> > > otherwise calls __absent_pages_in_range(), which already returns 0 for
> > > an empty range.
> >
> > Right, but it loops over memblock memory for an empty zone to get that 0
> 
> Indeed. How about adding an early return in __absent_pages_in_range()
> to avoid unnecessary iteration? I just want to remove the wrapper,
> which never uses its zone_type argument since eb0e5b61369f
> ("mm/mm_init: don't overlap NORMAL and MOVABLE zones with
> kernelcore=mirror")
> 
>         unsigned long nr_absent = range_end_pfn - range_start_pfn;
>         unsigned long start_pfn, end_pfn;
>         int i;
> 
> +       if (!nr_absent)

Yes, just please add a comment:
	
	/* range is empty, nothing to do */

> +               return 0;
> +
>         for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
>                 start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
>                 end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
> 
> > --
> > Sincerely yours,
> > Mike.
> >

-- 
Sincerely yours,
Mike.