mm/z3fold: fix the comment for __encode_handle()

The comment is confusing that Pool lock should be held as this function
accesses first_num above the __encode_handle() because first_num is the
element of z3fold_header which is protected by z3fold_header->page_lock.

I found the same comment for encode_handle() in zbud.c by accident ,Pool
lock should be held as this function accesses first|last_chunks, which is
the element of zbud_header and it does not have any lock, so pool lock
should be held.

Z3fold is based on zbud, maybe the comment come from zbud, but it was
wrong, so fix it.

Link: https://lkml.kernel.org/r/20240219024453.2240147-1-hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 7c76b396b74cfdb39b761124556ee4e428510fdf..7ab05621052dc5a4b5f3add96a92ca54e76b10c2 100644 (file)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -364,8 +364,9 @@ static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 }
 
 /*
- * Encodes the handle of a particular buddy within a z3fold page
- * Pool lock should be held as this function accesses first_num
+ * Encodes the handle of a particular buddy within a z3fold page.
+ * Zhdr->page_lock should be held as this function accesses first_num
+ * if bud != HEADLESS.
  */
 static unsigned long __encode_handle(struct z3fold_header *zhdr,
                                struct z3fold_buddy_slots *slots,