linux-kernel - [PATCH v7 15/15] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page

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Message-Id: <20201130151838.11208-16-songmuchun@bytedance.com>
Date:   Mon, 30 Nov 2020 23:18:38 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
        oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
        almasrymina@...gle.com, rientjes@...gle.com, willy@...radead.org,
        osalvador@...e.de, mhocko@...e.com, song.bao.hua@...ilicon.com
Cc:     duanxiongchun@...edance.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v7 15/15] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page

There are only `RESERVE_VMEMMAP_SIZE / sizeof(struct page)` struct pages
can be used when CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, so add a BUILD_BUG_ON
to catch this invalid usage of tail struct page.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/hugetlb_vmemmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index ebc710d148e4..3328de88819e 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -340,6 +340,9 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
 	unsigned int nr_pages = pages_per_huge_page(h);
 	unsigned int vmemmap_pages;
 
+	BUILD_BUG_ON(NR_USED_SUBPAGE >=
+		     RESERVE_VMEMMAP_SIZE / sizeof(struct page));
+
 	if (!is_power_of_2(sizeof(struct page)) ||
 	    !hugetlb_free_vmemmap_enabled) {
 		pr_info("disable freeing vmemmap pages for %s\n", h->name);
-- 
2.11.0