On 10/9/25 17:12, David Hildenbrand wrote:

On 09.10.25 06:21, Balbir Singh wrote:

quoted

On 8/22/25 06:06, David Hildenbrand wrote:

quoted

Let's reject them early, which in turn makes folio_alloc_gigantic() reject
them properly.

To avoid converting from order to nr_pages, let's just add MAX_FOLIO_ORDER
and calculate MAX_FOLIO_NR_PAGES based on that.

Signed-off-by: David Hildenbrand <redacted>
---
  include/linux/mm.h | 6 ++++--
  mm/page_alloc.c    | 5 ++++-
  2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 00c8a54127d37..77737cbf2216a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -2055,11 +2055,13 @@ static inline long folio_nr_pages(const struct folio *folio)

    /* Only hugetlbfs can allocate folios larger than MAX_ORDER */
  #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-#define MAX_FOLIO_NR_PAGES    (1UL << PUD_ORDER)
+#define MAX_FOLIO_ORDER        PUD_ORDER

Do we need to check for CONTIG_ALLOC as well with CONFIG_ARCH_HAS_GIGANTIC_PAGE?

I don't think so, can you elaborate?

The only way to allocate a gigantic page is to use CMA, IIRC, which is covered by CONTIG_ALLOC

quoted

quoted

  #else
-#define MAX_FOLIO_NR_PAGES    MAX_ORDER_NR_PAGES
+#define MAX_FOLIO_ORDER        MAX_PAGE_ORDER
  #endif
  +#define MAX_FOLIO_NR_PAGES    (1UL << MAX_FOLIO_ORDER)
+
  /*
   * compound_nr() returns the number of pages in this potentially compound
   * page.  compound_nr() can be called on a tail page, and is defined to

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ca9e6b9633f79..1e6ae4c395b30 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -6833,6 +6833,7 @@ static int __alloc_contig_verify_gfp_mask(gfp_t gfp_mask, gfp_t *gfp_cc_mask)

  int alloc_contig_range_noprof(unsigned long start, unsigned long end,
                    acr_flags_t alloc_flags, gfp_t gfp_mask)
  {
+    const unsigned int order = ilog2(end - start);

Do we need a VM_WARN_ON(end < start)?

I don't think so.

end - start being < 0, completely breaks ilog2. But we would error out because ilog2 > MAX_FOLIO_ORDER, so we should fine

quoted

quoted

      unsigned long outer_start, outer_end;
      int ret = 0;
  @@ -6850,6 +6851,9 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
                          PB_ISOLATE_MODE_CMA_ALLOC :
                          PB_ISOLATE_MODE_OTHER;
  +    if (WARN_ON_ONCE((gfp_mask & __GFP_COMP) && order > MAX_FOLIO_ORDER))
+        return -EINVAL;
+
      gfp_mask = current_gfp_context(gfp_mask);
      if (__alloc_contig_verify_gfp_mask(gfp_mask, (gfp_t *)&cc.gfp_mask))
          return -EINVAL;

@@ -6947,7 +6951,6 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,

              free_contig_range(end, outer_end - end);
      } else if (start == outer_start && end == outer_end && is_power_of_2(end - start)) {
          struct page *head = pfn_to_page(start);
-        int order = ilog2(end - start);
            check_new_pages(head, order);
          prep_new_page(head, order, gfp_mask, 0);

Acked-by: Balbir Singh <redacted>

Thanks for the review, but note that this is already upstream.

Sorry, this showed up in my updated mm thread and I ended up reviewing it, please ignore if it's upstream

Balbir