mm/mm_slot.h: add a helper function mm_slot_remove

Patch series "Two small patches to clean up mm/mm_slot.h", v3.

mm_slot.h is mainly used by THP and KSM.

Patch 1 introduces mm_slot_remove() to abstract the common
hash_del() + list_del() sequence used in both khugepaged and KSM.

Patch 2 adds a comment explaining why mm_slot_lookup/insert cannot
be converted to static inline functions.


This patch (of 2):

Both THP 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().

Introduce mm_slot_remove() to abstract the common hash_del() + list_del()
sequence used in both khugepaged and KSM.

No functional change is intended.

Link: https://lore.kernel.org/202607140924549782dUh3YBPmy8g1NDMK2zIW@zte.com.cn
Link: https://lore.kernel.org/20260714092622583ayzGzGYSjAareKKHt_T91@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Nico Pache <npache@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Cc: Qi Zheng <qi.zheng@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 10 insertions, 10 deletions

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 45e8245d80da..27e8f3077e80 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 14550f69cf02..47006f494fcb 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1257,8 +1257,7 @@ mm_exiting:
 				  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 @@ no_vmas:
 		 * 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..5de3e91d86b4 100644
--- a/mm/mm_slot.h
+++ b/mm/mm_slot.h
@@ -52,4 +52,9 @@ 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 *slot)
+{
+	hash_del(&slot->hash);
+	list_del(&slot->mm_node);
+}
 #endif /* _LINUX_MM_SLOT_H */