[PATCH RFC 05/13] mm/huge_memory: consolidate irq and locking for folio split

Let each split helper handle its own locking instead of relying on
the caller, so both paths follow the same convention and __folio_split()
can drop its local irq handling and fail label, preparing for further
cleanup.

Signed-off-by: Kairui Song <[email protected]>
---
 mm/huge_memory.c | 52 ++++++++++++++++++++++++----------------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 56a356c30f30..ca9430a6f8d1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3947,6 +3947,8 @@ static int __folio_freeze_split_unmapped_anon(struct folio *folio, unsigned int
 	bool dequeue_deferred;
 	int ret = 0;
 
+	local_irq_disable();
+
 	/*
 	 * If this folio can be on the deferred split queue, lock out
 	 * the shrinker before freezing the ref. If the shrinker sees
@@ -3969,6 +3971,7 @@ static int __folio_freeze_split_unmapped_anon(struct folio *folio, unsigned int
 			list_lru_unlock(lru);
 			rcu_read_unlock();
 		}
+		local_irq_enable();
 		return -EAGAIN;
 	}
 
@@ -4020,6 +4023,7 @@ static int __folio_freeze_split_unmapped_anon(struct folio *folio, unsigned int
 		lruvec_unlock(lruvec);
 	if (ci)
 		swap_cluster_unlock(ci);
+	local_irq_enable();
 
 	return ret;
 }
@@ -4035,8 +4039,21 @@ static int __folio_freeze_split_unmapped_file(struct folio *folio, unsigned int
 	struct lruvec *lruvec;
 	int ret;
 
-	if (!folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1))
-		return -EAGAIN;
+	xas_lock_irq(xas);
+
+	/*
+	 * Check if the folio is present in page cache.
+	 * We assume all tail are present too, if folio is there.
+	 */
+	if (xas_load(xas) != folio) {
+		ret = -EAGAIN;
+		goto fail;
+	}
+
+	if (!folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1)) {
+		ret = -EAGAIN;
+		goto fail;
+	}
 
 	if (folio_test_pmd_mappable(folio) &&
 	    new_order < HPAGE_PMD_ORDER) {
@@ -4107,6 +4124,8 @@ static int __folio_freeze_split_unmapped_file(struct folio *folio, unsigned int
 	if (do_lru)
 		lruvec_unlock(lruvec);
 
+fail:
+	xas_unlock_irq(xas);
 	return ret;
 }
 
@@ -4246,19 +4265,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 
 	unmap_folio(folio);
 
-	/* block interrupt reentry in xa_lock and spinlock */
-	local_irq_disable();
-	if (mapping) {
-		/*
-		 * Check if the folio is present in page cache.
-		 * We assume all tail are present too, if folio is there.
-		 */
-		xas_lock(&xas);
-		xas_reset(&xas);
-		if (xas_load(&xas) != folio) {
-			ret = -EAGAIN;
-			goto fail;
-		}
+	if (!is_anon) {
 		ret = __folio_freeze_split_unmapped_file(folio, new_order, split_at, &xas, mapping,
 							 true, list, split_type, end,
 							 &nr_shmem_dropped);
@@ -4267,12 +4274,6 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 							 list, split_type);
 	}
 
-fail:
-	if (mapping)
-		xas_unlock(&xas);
-
-	local_irq_enable();
-
 	if (nr_shmem_dropped)
 		shmem_uncharge(mapping->host, nr_shmem_dropped);
 
@@ -4355,8 +4356,6 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
  */
 int folio_split_unmapped(struct folio *folio, unsigned int new_order)
 {
-	int ret = 0;
-
 	VM_WARN_ON_ONCE_FOLIO(folio_mapped(folio), folio);
 	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
 	VM_WARN_ON_ONCE_FOLIO(!folio_test_large(folio), folio);
@@ -4365,11 +4364,8 @@ int folio_split_unmapped(struct folio *folio, unsigned int new_order)
 	if (folio_expected_ref_count(folio) != folio_ref_count(folio) - 1)
 		return -EAGAIN;
 
-	local_irq_disable();
-	ret = __folio_freeze_split_unmapped_anon(folio, new_order, &folio->page,
-						 false, NULL, SPLIT_TYPE_UNIFORM);
-	local_irq_enable();
-	return ret;
+	return __folio_freeze_split_unmapped_anon(folio, new_order, &folio->page,
+						  false, NULL, SPLIT_TYPE_UNIFORM);
 }
 
 /*

-- 
2.55.0