diff --git a/include/linux/mm.h b/include/linux/mm.h
index 84988d4ff8fb2..93eb291181f79 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -691,6 +691,11 @@ static bool __is_vma_write_locked(struct vm_area_struct *vma, int *mm_lock_seq)
 	return (vma->vm_lock_seq == *mm_lock_seq);
 }
 
+/*
+ * Begin writing to a VMA.
+ * Exclude concurrent readers under the per-VMA lock until the currently
+ * write-locked mmap_lock is dropped or downgraded.
+ */
 static inline void vma_start_write(struct vm_area_struct *vma)
 {
 	int mm_lock_seq;
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index a5c63b6d7d46c..8d38dcb6d044c 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -73,6 +73,14 @@ static inline void mmap_assert_write_locked(struct mm_struct *mm)
 }
 
 #ifdef CONFIG_PER_VMA_LOCK
+/*
+ * Drop all currently-held per-VMA locks.
+ * This is called from the mmap_lock implementation directly before releasing
+ * a write-locked mmap_lock (or downgrading it to read-locked).
+ * This should normally NOT be called manually from other places.
+ * If you want to call this manually anyway, keep in mind that this will release
+ * *all* VMA write locks, including ones from further up the stack.
+ */
 static inline void vma_end_write_all(struct mm_struct *mm)
 {
 	mmap_assert_write_locked(mm);
diff --git a/mm/mmap.c b/mm/mmap.c
index 7bd1caa09dddf..4a9466b766483 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3642,6 +3642,12 @@ int mm_take_all_locks(struct mm_struct *mm)
 
 	mutex_lock(&mm_all_locks_mutex);
 
+	/*
+	 * vma_start_write() does not have a complement in mm_drop_all_locks()
+	 * because vma_start_write() is always asymmetrical; it marks a VMA as
+	 * being written to until mmap_write_unlock() or mmap_write_downgrade()
+	 * is reached.
+	 */
 	mas_for_each(&mas, vma, ULONG_MAX) {
 		if (signal_pending(current))
 			goto out_unlock;
@@ -3738,7 +3744,6 @@ void mm_drop_all_locks(struct mm_struct *mm)
 		if (vma->vm_file && vma->vm_file->f_mapping)
 			vm_unlock_mapping(vma->vm_file->f_mapping);
 	}
-	vma_end_write_all(mm);
 
 	mutex_unlock(&mm_all_locks_mutex);
 }