From 5c3746a0fe380ae7ec5ee0e4aaef19b68b51d903 Mon Sep 17 00:00:00 2001
From: xu xin <xu.xin16@zte.com.cn>
Date: Tue, 14 Jul 2026 09:28:15 +0800
Subject: [PATCH] mm/mm_slot.h: add comments for mm_slot_lookup/insert

mm_slot_lookup() and mm_slot_insert() are the only helpers in this header
that are implemented as macros rather than static inline functions.  This
may look inconsistent without explanation.

Explain they must be macros because hash_for_each_possible() needs the
table as an array (for sizeof), not a pointer.

Link: https://lore.kernel.org/20260714092815120Wv-CFDlLKtsTmda--97Qw@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Qi Zheng <qi.zheng@linux.dev>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
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: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/mm_slot.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/mm_slot.h b/mm/mm_slot.h
index 5de3e91d86b4..9b09b68e5742 100644
--- a/mm/mm_slot.h
+++ b/mm/mm_slot.h
@@ -33,6 +33,12 @@ static inline void mm_slot_free(struct kmem_cache *cache, void *objp)
 	kmem_cache_free(cache, objp);
 }
 
+/*
+ * Note: mm_slot_lookup and mm_slot_insert cannot be converted to static inline
+ * functions because the hash helpers (hash_for_each_possible and hash_add) rely
+ * on the actual array argument 'hashtable' for sizeof() instead of pointers.
+ */
+
 #define mm_slot_lookup(_hashtable, _mm) 				       \
 ({									       \
 	struct mm_slot *tmp_slot, *mm_slot = NULL;			       \