From: Miaohe Lin <linmiaohe@huawei.com>
Date: Thu, 1 Sep 2022 12:00:28 +0000 (+0800)
Subject: hugetlb: add comment for subtle SetHPageVmemmapOptimized()
X-Git-Tag: v6.1-rc1~68^2~424
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a9e1eab241bdaadd56b6cfdc481cff6a24c4799b;p=thirdparty%2Flinux.git

hugetlb: add comment for subtle SetHPageVmemmapOptimized()

The SetHPageVmemmapOptimized() called here seems unnecessary as it's
assumed to be set when calling this function. But it's indeed cleared
by above set_page_private(page, 0). Add a comment to avoid possible
future confusion.

Link: https://lkml.kernel.org/r/20220901120030.63318-9-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 29c3478d1bf37..fe7b69a970aa7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1504,6 +1504,10 @@ static void add_hugetlb_page(struct hstate *h, struct page *page,
 
 	set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
 	set_page_private(page, 0);
+	/*
+	 * We have to set HPageVmemmapOptimized again as above
+	 * set_page_private(page, 0) cleared it.
+	 */
 	SetHPageVmemmapOptimized(page);
 
 	/*