[PATCH mm-unstable v1 3/5] mm/khugepaged: define COLLAPSE_MAX_PTES_LIMIT as HPAGE_PMD_NR - 1

Nico Pache
2026-02-12T02:19:27Z

The value (HPAGE_PMD_NR - 1) is used often in the khugepaged code to
signify the limit of the max_ptes_* values. Add a define for this to
increase code readability and reuse.

Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c362b3b2e08a..3dcce6018f20 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -85,6 +85,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
*
* Note that these are only respected if collapse was initiated by khugepaged.
*/
+#define COLLAPSE_MAX_PTES_LIMIT (HPAGE_PMD_NR - 1)
unsigned int khugepaged_max_ptes_none __read_mostly;
static unsigned int khugepaged_max_ptes_swap __read_mostly;
static unsigned int khugepaged_max_ptes_shared __read_mostly;
@@ -252,7 +253,7 @@ static ssize_t max_ptes_none_store(struct kobject *kobj,
unsigned long max_ptes_none;

err = kstrtoul(buf, 10, &max_ptes_none);
- if (err || max_ptes_none > HPAGE_PMD_NR - 1)
+ if (err || max_ptes_none > COLLAPSE_MAX_PTES_LIMIT)
return -EINVAL;

khugepaged_max_ptes_none = max_ptes_none;
@@ -277,7 +278,7 @@ static ssize_t max_ptes_swap_store(struct kobject *kobj,
unsigned long max_ptes_swap;

err = kstrtoul(buf, 10, &max_ptes_swap);
- if (err || max_ptes_swap > HPAGE_PMD_NR - 1)
+ if (err || max_ptes_swap > COLLAPSE_MAX_PTES_LIMIT)
return -EINVAL;

khugepaged_max_ptes_swap = max_ptes_swap;
@@ -303,7 +304,7 @@ static ssize_t max_ptes_shared_store(struct kobject *kobj,
unsigned long max_ptes_shared;

err = kstrtoul(buf, 10, &max_ptes_shared);
- if (err || max_ptes_shared > HPAGE_PMD_NR - 1)
+ if (err || max_ptes_shared > COLLAPSE_MAX_PTES_LIMIT)
return -EINVAL;

khugepaged_max_ptes_shared = max_ptes_shared;
@@ -384,7 +385,7 @@ int __init khugepaged_init(void)
return -ENOMEM;

khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
- khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
+ khugepaged_max_ptes_none = COLLAPSE_MAX_PTES_LIMIT;
khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;

@@ -1869,7 +1870,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
bool is_shmem = shmem_file(file);

VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
- VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
+ VM_BUG_ON(start & (COLLAPSE_MAX_PTES_LIMIT));

result = alloc_charge_folio(&new_folio, mm, cc);
if (result != SCAN_SUCCEED)
@@ -2209,7 +2210,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
* unwritten page.
*/
folio_mark_uptodate(new_folio);
- folio_ref_add(new_folio, HPAGE_PMD_NR - 1);
+ folio_ref_add(new_folio, COLLAPSE_MAX_PTES_LIMIT);

if (is_shmem)
folio_mark_dirty(new_folio);
@@ -2303,7 +2304,7 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
rcu_read_lock();
- xas_for_each(&xas, folio, start + HPAGE_PMD_NR - 1) {
+ xas_for_each(&xas, folio, start + COLLAPSE_MAX_PTES_LIMIT) {
if (xas_retry(&xas, folio))
continue;

--
2.53.0