linux-kernel - [PATCH 3/9] mm/damon/vaddr: cleanup using pmd_trans_huge

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Message-ID: <20251112154114.66053-4-sj@kernel.org>
Date: Wed, 12 Nov 2025 07:41:06 -0800
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
	damon@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Hugh Dickins <hughd@...gle.com>
Subject: [PATCH 3/9] mm/damon/vaddr: cleanup using pmd_trans_huge_lock()

Three pmd walk functions in vaddr.c are using pmd_trans_huge() and
pmd_lock() to handle THPs.  Simplify the code by replacing the two
function calls with a single pmd_trans_huge_lock() call.

Note that this cleanup is not only reducing the lines of code, but also
simplifies code execution flows for migration entries case, as kindly
explained [1] by Hugh, who suggested this cleanup.

[1] https://lore.kernel.org/296c2b3f-6748-158f-b85d-2952165c0588@google.com

Suggested-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/damon/vaddr.c | 48 ++++++++++++------------------------------------
 1 file changed, 12 insertions(+), 36 deletions(-)

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 7e834467b2d8..0ad1ce120aa1 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -307,24 +307,14 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
 		unsigned long next, struct mm_walk *walk)
 {
 	pte_t *pte;
-	pmd_t pmde;
 	spinlock_t *ptl;
 
-	if (pmd_trans_huge(pmdp_get(pmd))) {
-		ptl = pmd_lock(walk->mm, pmd);
-		pmde = pmdp_get(pmd);
-
-		if (!pmd_present(pmde)) {
-			spin_unlock(ptl);
-			return 0;
-		}
-
-		if (pmd_trans_huge(pmde)) {
+	ptl = pmd_trans_huge_lock(pmd, walk->vma);
+	if (ptl) {
+		if (pmd_present(pmdp_get(pmd)))
 			damon_pmdp_mkold(pmd, walk->vma, addr);
-			spin_unlock(ptl);
-			return 0;
-		}
 		spin_unlock(ptl);
+		return 0;
 	}
 
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
@@ -446,21 +436,12 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
 	struct damon_young_walk_private *priv = walk->private;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (pmd_trans_huge(pmdp_get(pmd))) {
-		pmd_t pmde;
-
-		ptl = pmd_lock(walk->mm, pmd);
-		pmde = pmdp_get(pmd);
+	ptl = pmd_trans_huge_lock(pmd, walk->vma);
+	if (ptl) {
+		pmd_t pmde = pmdp_get(pmd);
 
-		if (!pmd_present(pmde)) {
-			spin_unlock(ptl);
-			return 0;
-		}
-
-		if (!pmd_trans_huge(pmde)) {
-			spin_unlock(ptl);
-			goto regular_page;
-		}
+		if (!pmd_present(pmde))
+			goto huge_out;
 		folio = damon_get_folio(pmd_pfn(pmde));
 		if (!folio)
 			goto huge_out;
@@ -474,8 +455,6 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
 		spin_unlock(ptl);
 		return 0;
 	}
-
-regular_page:
 #endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
 
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
@@ -910,13 +889,10 @@ static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr,
 	int nr;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (pmd_trans_huge(*pmd)) {
-		pmd_t pmde;
+	ptl = pmd_trans_huge_lock(pmd, vma);
+	if (ptl) {
+		pmd_t pmde = pmdp_get(pmd);
 
-		ptl = pmd_trans_huge_lock(pmd, vma);
-		if (!ptl)
-			return 0;
-		pmde = pmdp_get(pmd);
 		if (!pmd_present(pmde))
 			goto huge_unlock;
 
-- 
2.47.3