[PATCH mm-unstable v1 2/5] mm: introduce is_pmd_order helper

Nico Pache
2026-02-12T02:19:18Z

In order to add mTHP support to khugepaged, we will often be checking if a
given order is (or is not) a PMD order. Some places in the kernel already
use this check, so lets create a simple helper function to keep the code
clean and readable.

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Nico Pache <npache@redhat.com>

arches# pick b3ace8be204f # mm/khugepaged: rename hpage_collapse_* to collapse_*
---
include/linux/huge_mm.h | 5 +++++
mm/huge_memory.c | 2 +-
mm/khugepaged.c | 4 ++--
mm/mempolicy.c | 2 +-
mm/page_alloc.c | 2 +-
5 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a4d9f964dfde..bd7f0e1d8094 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -771,6 +771,11 @@ static inline bool pmd_is_huge(pmd_t pmd)
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

+static inline bool is_pmd_order(unsigned int order)
+{
+ return order == HPAGE_PMD_ORDER;
+}
+
static inline int split_folio_to_list_to_order(struct folio *folio,
struct list_head *list, int new_order)
{
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 44ff8a648afd..5eae85818635 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4097,7 +4097,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
i_mmap_unlock_read(mapping);
out:
xas_destroy(&xas);
- if (old_order == HPAGE_PMD_ORDER)
+ if (is_pmd_order(old_order))
count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
count_mthp_stat(old_order, !ret ? MTHP_STAT_SPLIT : MTHP_STAT_SPLIT_FAILED);
return ret;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fa1e57fd2c46..c362b3b2e08a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2000,7 +2000,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
* we locked the first folio, then a THP might be there already.
* This will be discovered on the first iteration.
*/
- if (folio_order(folio) == HPAGE_PMD_ORDER &&
+ if (is_pmd_order(folio_order(folio)) &&
folio->index == start) {
/* Maybe PMD-mapped */
result = SCAN_PTE_MAPPED_HUGEPAGE;
@@ -2329,7 +2329,7 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
continue;
}

- if (folio_order(folio) == HPAGE_PMD_ORDER &&
+ if (is_pmd_order(folio_order(folio)) &&
folio->index == start) {
/* Maybe PMD-mapped */
result = SCAN_PTE_MAPPED_HUGEPAGE;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index dbd48502ac24..3802e52b01fc 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2450,7 +2450,7 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order,

if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
/* filter "hugepage" allocation, unless from alloc_pages() */
- order == HPAGE_PMD_ORDER && ilx != NO_INTERLEAVE_INDEX) {
+ is_pmd_order(order) && ilx != NO_INTERLEAVE_INDEX) {
/*
* For hugepage allocation and non-interleave policy which
* allows the current node (or other explicitly preferred
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c2e96ac35636..2acf22f97ae5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -719,7 +719,7 @@ static inline bool pcp_allowed_order(unsigned int order)
if (order <= PAGE_ALLOC_COSTLY_ORDER)
return true;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- if (order == HPAGE_PMD_ORDER)
+ if (is_pmd_order(order))
return true;
#endif
return false;
--
2.53.0