linux-kernel - [PATCH v4 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

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Date:   Fri, 13 Nov 2020 18:59:52 +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
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 v4 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

We only can free the unused vmemmap to the buddy system when the
size of struct page is a power of two.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/hugetlb_vmemmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index f67aec6e3bb1..a0a5df9dba6b 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -635,7 +635,8 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
 	unsigned int order = huge_page_order(h);
 	unsigned int vmemmap_pages;
 
-	if (hugetlb_free_vmemmap_disabled) {
+	if (hugetlb_free_vmemmap_disabled ||
+	    !is_power_of_2(sizeof(struct page))) {
 		h->nr_free_vmemmap_pages = 0;
 		pr_info("disable free vmemmap pages for %s\n", h->name);
 		return;
-- 
2.11.0