[PATCH 5/8] mm/huge_memory: add a common exit path to zap_huge_pmd()

["Lorenzo Stoakes (Oracle)" <ljs@kernel.org>]

Other than when we acquire the PTL, we always need to unlock the PTL, and
optionally need to flush on exit.

The code is currently very duplicated in this respect, so default
flush_needed to false, set it true in the case in which it's required, then
share the same logic for all exit paths.

This also makes flush_needed make more sense as a function-scope value (we
don't need to flush for the PFN map/mixed map, zero huge, error cases for
instance).

Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
---
 mm/huge_memory.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8e6b7ba11448..724e1de74367 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2431,7 +2431,8 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		 pmd_t *pmd, unsigned long addr)
 {
 	struct folio *folio = NULL;
-	bool flush_needed = true;
+	bool flush_needed = false;
+	bool ret = true;
 	spinlock_t *ptl;
 	pmd_t orig_pmd;
 
@@ -2453,19 +2454,18 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	if (vma_is_special_huge(vma)) {
 		if (arch_needs_pgtable_deposit())
 			zap_deposited_table(tlb->mm, pmd);
-		spin_unlock(ptl);
-		return true;
+		goto out;
 	}
 	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);
-		return true;
+		goto out;
 	}
 
 	if (pmd_present(orig_pmd)) {
 		struct page *page = pmd_page(orig_pmd);
 
+		flush_needed = true;
 		folio = page_folio(page);
 		folio_remove_rmap_pmd(folio, page, vma);
 		WARN_ON_ONCE(folio_mapcount(folio) < 0);
@@ -2474,14 +2474,13 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		const softleaf_t entry = softleaf_from_pmd(orig_pmd);
 
 		folio = softleaf_to_folio(entry);
-		flush_needed = false;
 
 		if (!thp_migration_supported())
 			WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
 	} else {
 		WARN_ON_ONCE(true);
-		spin_unlock(ptl);
-		return false;
+		ret = false;
+		goto out;
 	}
 
 	if (folio_test_anon(folio)) {
@@ -2508,11 +2507,11 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		folio_put(folio);
 	}
 
+out:
 	spin_unlock(ptl);
 	if (flush_needed)
 		tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
-
-	return true;
+	return ret;
 }
 
 #ifndef pmd_move_must_withdraw
-- 
2.53.0