[PATCH] mm/mm_slot.h: add a helper function mm_slot_remove

[xu xin]

Both khugepaged (THP collapsing) and KSM manage per-mm scanning slots
using the mm_slot structure. The slot is kept in a hash table and a
list, and removal from both containers requires the same two operations:
hash_del() and list_del().

Currently, this twoâ??step removal is openâ??coded in multiple places
across khugepaged.c and ksm.c. This duplication makes the code slightly
harder to read and maintain, and creates the risk that future changes to
the removal logic might miss one of the call sites.

Introduce a helper function mm_slot_remove() that encapsulates both
deletions. This reduces redundancy, improves code clarity, and ensures
that the removal sequence stays consistent.

No functional change is intended.

Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
---
 mm/khugepaged.c | 6 ++----
 mm/ksm.c        | 9 +++------
 mm/mm_slot.h    | 7 +++++++
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 58e14d1543ec..5f6eb1bd9a67 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -606,8 +606,7 @@ void __khugepaged_exit(struct mm_struct *mm)
 	spin_lock(&khugepaged_mm_lock);
 	slot = mm_slot_lookup(mm_slots_hash, mm);
 	if (slot && khugepaged_scan.mm_slot != slot) {
-		hash_del(&slot->hash);
-		list_del(&slot->mm_node);
+		mm_slot_remove(slot);
 		free = 1;
 	}
 	spin_unlock(&khugepaged_mm_lock);
@@ -1802,8 +1801,7 @@ static void collect_mm_slot(struct mm_slot *slot)

 	if (collapse_test_exit(mm)) {
 		/* free mm_slot */
-		hash_del(&slot->hash);
-		list_del(&slot->mm_node);
+		mm_slot_remove(slot);

 		/*
 		 * Not strictly needed because the mm exited already.
diff --git a/mm/ksm.c b/mm/ksm.c
index 2791ce5bd44b..443dab513da6 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1257,8 +1257,7 @@ static int unmerge_and_remove_all_rmap_items(void)
 				  struct mm_slot, mm_node);
 		ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
 		if (ksm_test_exit(mm)) {
-			hash_del(&mm_slot->slot.hash);
-			list_del(&mm_slot->slot.mm_node);
+			mm_slot_remove(&mm_slot->slot);
 			spin_unlock(&ksm_mmlist_lock);

 			mm_slot_free(mm_slot_cache, mm_slot);
@@ -2772,8 +2771,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 		 * or when all VM_MERGEABLE areas have been unmapped (and
 		 * mmap_lock then protects against race with MADV_MERGEABLE).
 		 */
-		hash_del(&mm_slot->slot.hash);
-		list_del(&mm_slot->slot.mm_node);
+		mm_slot_remove(&mm_slot->slot);
 		spin_unlock(&ksm_mmlist_lock);

 		mm_slot_free(mm_slot_cache, mm_slot);
@@ -3116,8 +3114,7 @@ void __ksm_exit(struct mm_struct *mm)
 	if (ksm_scan.mm_slot == mm_slot)
 		goto unlock;
 	if (!mm_slot->rmap_list) {
-		hash_del(&slot->hash);
-		list_del(&slot->mm_node);
+		mm_slot_remove(slot);
 		easy_to_free = 1;
 	} else {
 		list_move(&slot->mm_node,
diff --git a/mm/mm_slot.h b/mm/mm_slot.h
index 83f18ed1c4bd..bc3b9ae8fdbc 100644
--- a/mm/mm_slot.h
+++ b/mm/mm_slot.h
@@ -52,4 +52,11 @@ static inline void mm_slot_free(struct kmem_cache *cache, void *objp)
 	hash_add(_hashtable, &_mm_slot->hash, (unsigned long)_mm);	       \
 })

+static inline void mm_slot_remove(struct mm_slot *_mm_slot)
+{
+	hash_del(&_mm_slot->hash);
+	list_del(&_mm_slot->mm_node);
+}
+
+
 #endif /* _LINUX_MM_SLOT_H */
-- 
2.25.1