[PATCH v4 06/21] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page()

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
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 v4 06/21] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page()
Date: Fri, 13 Nov 2020 18:59:37 +0800	[thread overview]
Message-ID: <20201113105952.11638-7-songmuchun@bytedance.com> (raw)
In-Reply-To: <20201113105952.11638-1-songmuchun@bytedance.com>

In the later patch, we can use the free_vmemmap_page() to free the
unused vmemmap pages and initialize a page for vmemmap page using
via prepare_vmemmap_page().

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/bootmem_info.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
index 4ed6dee1adc9..239e3cc8f86c 100644
--- a/include/linux/bootmem_info.h
+++ b/include/linux/bootmem_info.h
@@ -3,6 +3,7 @@
 #define __LINUX_BOOTMEM_INFO_H
 
 #include <linux/mmzone.h>
+#include <linux/mm.h>
 
 /*
  * Types for free bootmem stored in page->lru.next. These have to be in
@@ -22,6 +23,29 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat);
 void get_page_bootmem(unsigned long info, struct page *page,
 		      unsigned long type);
 void put_page_bootmem(struct page *page);
+
+static inline void free_vmemmap_page(struct page *page)
+{
+	VM_WARN_ON(!PageReserved(page) || page_ref_count(page) != 2);
+
+	/* bootmem page has reserved flag in the reserve_bootmem_region */
+	if (PageReserved(page)) {
+		unsigned long magic = (unsigned long)page->freelist;
+
+		if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
+			put_page_bootmem(page);
+		else
+			WARN_ON(1);
+	}
+}
+
+static inline void prepare_vmemmap_page(struct page *page)
+{
+	unsigned long section_nr = pfn_to_section_nr(page_to_pfn(page));
+
+	get_page_bootmem(section_nr, page, SECTION_INFO);
+	mark_page_reserved(page);
+}
 #else
 static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
 {
-- 
2.11.0

