[PATCH v2 2/9] mm/huge: avoid big else branch in zap_huge_pmd()

Lorenzo Stoakes (Oracle)
2026-03-19T13:00:29Z

We don't need to have an extra level of indentation, we can simply exit
early in the first two branches.

Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
---
mm/huge_memory.c | 87 +++++++++++++++++++++++++-----------------------
1 file changed, 45 insertions(+), 42 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f76edfa91e96..4ebe1f19341e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2421,8 +2421,10 @@ static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr)
{
- pmd_t orig_pmd;
+ struct folio *folio = NULL;
+ int flush_needed = 1;
spinlock_t *ptl;
+ pmd_t orig_pmd;

tlb_change_page_size(tlb, HPAGE_PMD_SIZE);

@@ -2443,59 +2445,60 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
if (arch_needs_pgtable_deposit())
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
- } else if (is_huge_zero_pmd(orig_pmd)) {
+ return 1;
+ }
+ if (is_huge_zero_pmd(orig_pmd)) {
if (!vma_is_dax(vma) || arch_needs_pgtable_deposit())
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
- } else {
- struct folio *folio = NULL;
- int flush_needed = 1;
+ return 1;
+ }

- if (pmd_present(orig_pmd)) {
- struct page *page = pmd_page(orig_pmd);
+ if (pmd_present(orig_pmd)) {
+ struct page *page = pmd_page(orig_pmd);

- folio = page_folio(page);
- folio_remove_rmap_pmd(folio, page, vma);
- WARN_ON_ONCE(folio_mapcount(folio) < 0);
- VM_BUG_ON_PAGE(!PageHead(page), page);
- } else if (pmd_is_valid_softleaf(orig_pmd)) {
- const softleaf_t entry = softleaf_from_pmd(orig_pmd);
+ folio = page_folio(page);
+ folio_remove_rmap_pmd(folio, page, vma);
+ WARN_ON_ONCE(folio_mapcount(folio) < 0);
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+ } else if (pmd_is_valid_softleaf(orig_pmd)) {
+ const softleaf_t entry = softleaf_from_pmd(orig_pmd);

- folio = softleaf_to_folio(entry);
- flush_needed = 0;
+ folio = softleaf_to_folio(entry);
+ flush_needed = 0;

- if (!thp_migration_supported())
- WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
- }
+ if (!thp_migration_supported())
+ WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+ }

- if (folio_test_anon(folio)) {
+ if (folio_test_anon(folio)) {
+ zap_deposited_table(tlb->mm, pmd);
+ add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
+ } else {
+ if (arch_needs_pgtable_deposit())
zap_deposited_table(tlb->mm, pmd);
- add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
- } else {
- if (arch_needs_pgtable_deposit())
- zap_deposited_table(tlb->mm, pmd);
- add_mm_counter(tlb->mm, mm_counter_file(folio),
- -HPAGE_PMD_NR);
-
- /*
- * Use flush_needed to indicate whether the PMD entry
- * is present, instead of checking pmd_present() again.
- */
- if (flush_needed && pmd_young(orig_pmd) &&
- likely(vma_has_recency(vma)))
- folio_mark_accessed(folio);
- }
+ add_mm_counter(tlb->mm, mm_counter_file(folio),
+ -HPAGE_PMD_NR);

- if (folio_is_device_private(folio)) {
- folio_remove_rmap_pmd(folio, &folio->page, vma);
- WARN_ON_ONCE(folio_mapcount(folio) < 0);
- folio_put(folio);
- }
+ /*
+ * Use flush_needed to indicate whether the PMD entry
+ * is present, instead of checking pmd_present() again.
+ */
+ if (flush_needed && pmd_young(orig_pmd) &&
+ likely(vma_has_recency(vma)))
+ folio_mark_accessed(folio);
+ }

- spin_unlock(ptl);
- if (flush_needed)
- tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
+ if (folio_is_device_private(folio)) {
+ folio_remove_rmap_pmd(folio, &folio->page, vma);
+ WARN_ON_ONCE(folio_mapcount(folio) < 0);
+ folio_put(folio);
}
+
+ spin_unlock(ptl);
+ if (flush_needed)
+ tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
+
return 1;
}

--
2.53.0