Re: [PATCH 2/2] mm/mm_init: drop overlap_memmap_init()

[Mike Rapoport <rppt@kernel.org>]

Hi Wei,

On Thu, Jun 25, 2026 at 09:58:47AM +0000, Wei Yang wrote:
> On Thu, Jun 25, 2026 at 10:39:40AM +0300, Mike Rapoport wrote:
> >From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> >
> >When ZONE_NORMAL and ZONE_MOVABLE could overlap because kernelcore=mirror
> >didn't reduce the span of ZONE_NORMAL, initialization of the memory map had
> >to skip overlapping pages during initialization of ZONE_MOVABLE to avoid
> >double initialization of the same struct pages.
> >
> >Since kernelcore=mirror works now the same way as other variants of
> >kernelcore=/movablecore=, and adjusts the span of ZONE_NORMAL, there can't
> >be an overlap between ZONE_NORMAL and ZONE_MOVABLE.
> >
> >Remove overlap_memmap_init().
> >
> 
> Do you think this is valuable to mention the double init for the overlapped
> range?

Not sure I follow.
We had this weird overlap_memmap_init() exactly to avoid double init.
 
> >Co-developed-by: Wei Yang <richard.weiyang@gmail.com>
> >Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> >Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> >---
> > mm/mm_init.c | 24 ------------------------
> > 1 file changed, 24 deletions(-)
> >
> >diff --git a/mm/mm_init.c b/mm/mm_init.c
> >index dce9dc9f2302..6f0a71ccca30 100644
> >--- a/mm/mm_init.c
> >+++ b/mm/mm_init.c
> >@@ -783,28 +783,6 @@ void __meminit init_deferred_page(unsigned long pfn, int nid)
> > 	__init_deferred_page(pfn, nid);
> > }
> > 
> >-/* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped init */
> >-static bool __meminit
> >-overlap_memmap_init(unsigned long zone, unsigned long *pfn)
> >-{
> >-	static struct memblock_region *r __meminitdata;
> >-
> >-	if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
> >-		if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
> >-			for_each_mem_region(r) {
> >-				if (*pfn < memblock_region_memory_end_pfn(r))
> >-					break;
> >-			}
> >-		}
> >-		if (*pfn >= memblock_region_memory_base_pfn(r) &&
> >-		    memblock_is_mirror(r)) {
> >-			*pfn = memblock_region_memory_end_pfn(r);
> >-			return true;
> >-		}
> >-	}
> >-	return false;
> >-}
> >-
> > /*
> >  * Only struct pages that correspond to ranges defined by memblock.memory
> >  * are zeroed and initialized by going through __init_single_page() during
> >@@ -891,8 +869,6 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
> > 		 * function.  They do not exist on hotplugged memory.
> > 		 */
> > 		if (context == MEMINIT_EARLY) {
> >-			if (overlap_memmap_init(zone, &pfn))
> >-				continue;
> > 			if (defer_init(nid, pfn, zone_end_pfn)) {
> > 				deferred_struct_pages = true;
> > 				break;
> >-- 
> >2.53.0
> 
> -- 
> Wei Yang
> Help you, Help me

-- 
Sincerely yours,
Mike.