[PATCH v7 06/15] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

From: Muchun Song <songmuchun@bytedance.com>
To: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
	dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, viro@zeniv.linux.org.uk,
	akpm@linux-foundation.org, paulmck@kernel.org,
	mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com,
	rdunlap@infradead.org, oneukum@suse.com,
	anshuman.khandual@arm.com, jroedel@suse.de,
	almasrymina@google.com, rientjes@google.com, willy@infradead.org,
	osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com
Cc: duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org,
	Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v7 06/15] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two
Date: Mon, 30 Nov 2020 23:18:29 +0800	[thread overview]
Message-ID: <20201130151838.11208-7-songmuchun@bytedance.com> (raw)
In-Reply-To: <20201130151838.11208-1-songmuchun@bytedance.com>

We only can free the tail vmemmap pages of HugeTLB to the buddy allocator
when the size of struct page is a power of two.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/hugetlb_vmemmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 51152e258f39..ad8fc61ea273 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -111,6 +111,11 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
 	unsigned int nr_pages = pages_per_huge_page(h);
 	unsigned int vmemmap_pages;
 
+	if (!is_power_of_2(sizeof(struct page))) {
+		pr_info("disable freeing vmemmap pages for %s\n", h->name);
+		return;
+	}
+
 	vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;
 	/*
 	 * The head page and the first tail page are not to be freed to buddy
-- 
2.11.0

