On 28.08.25 09:21, Mike Rapoport wrote:

On Thu, Aug 28, 2025 at 12:01:17AM +0200, David Hildenbrand wrote:

quoted

We can now safely iterate over all pages in a folio, so no need for the
pfn_to_page().

Also, as we already force the refcount in __init_single_page() to 1,
we can just set the refcount to 0 and avoid page_ref_freeze() +
VM_BUG_ON. Likely, in the future, we would just want to tell
__init_single_page() to which value to initialize the refcount.

Further, adjust the comments to highlight that we are dealing with an
open-coded prep_compound_page() variant, and add another comment explaining
why we really need the __init_single_page() only on the tail pages.

Note that the current code was likely problematic, but we never ran into
it: prep_compound_tail() would have been called with an offset that might
exceed a memory section, and prep_compound_tail() would have simply
added that offset to the page pointer -- which would not have done the
right thing on sparsemem without vmemmap.

Signed-off-by: David Hildenbrand <redacted>
---
  mm/hugetlb.c | 20 ++++++++++++--------
  1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4a97e4f14c0dc..1f42186a85ea4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c

@@ -3237,17 +3237,18 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
  {
  	enum zone_type zone = zone_idx(folio_zone(folio));
  	int nid = folio_nid(folio);
+	struct page *page = folio_page(folio, start_page_number);
  	unsigned long head_pfn = folio_pfn(folio);
  	unsigned long pfn, end_pfn = head_pfn + end_page_number;
-	int ret;
-
-	for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) {
-		struct page *page = pfn_to_page(pfn);
  
+	/*
+	 * We mark all tail pages with memblock_reserved_mark_noinit(),
+	 * so these pages are completely uninitialized.

                              ^ not? ;-)

Can you elaborate?

-- 
Cheers

David / dhildenb