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.

[sj@kernel.org: provide lvalue to pmd_present()]
  Link: https://lkml.kernel.org/r/20251117154415.11041-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20251112154114.66053-4-sj@kernel.org
Link: https://lore.kernel.org/296c2b3f-6748-158f-b85d-2952165c0588@google.com [1]
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 13 insertions, 35 deletions

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 7e834467b2d8..83d9b09c86a8 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -307,24 +307,16 @@ 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;
-		}
+	ptl = pmd_trans_huge_lock(pmd, walk->vma);
+	if (ptl) {
+		pmd_t pmde = pmdp_get(pmd);
 
-		if (pmd_trans_huge(pmde)) {
+		if (pmd_present(pmde))
 			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 +438,12 @@ 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 +457,6 @@ huge_out:
 		spin_unlock(ptl);
 		return 0;
 	}
-
-regular_page:
 #endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
 
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
@@ -910,13 +891,10 @@ 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;