[PATCH v4 08/21] mm/hugetlb: Initialize page table lock for vmemmap

[Muchun Song <songmuchun@bytedance.com>]

In the later patch, we will use the vmemmap page table lock to
guard the splitting of the vmemmap PMD. So initialize the vmemmap
page table lock.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/hugetlb_vmemmap.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index b7dfa97b4ea9..332c131c01a8 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -71,6 +71,8 @@
  */
 #define pr_fmt(fmt)	"HugeTLB Vmemmap: " fmt
 
+#include <linux/pagewalk.h>
+#include <linux/mmzone.h>
 #include <linux/list.h>
 #include <asm/pgalloc.h>
 #include "hugetlb_vmemmap.h"
@@ -179,3 +181,70 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
 	pr_debug("can free %d vmemmap pages for %s\n", h->nr_free_vmemmap_pages,
 		 h->name);
 }
+
+static int __init vmemmap_pud_entry(pud_t *pud, unsigned long addr,
+				    unsigned long next, struct mm_walk *walk)
+{
+	struct page *page = pud_page(*pud);
+
+	/*
+	 * The page->private shares storage with page->ptl. So make sure
+	 * that the PG_private is not set and initialize page->private to
+	 * zero.
+	 */
+	VM_BUG_ON_PAGE(PagePrivate(page), page);
+	set_page_private(page, 0);
+
+	BUG_ON(!pmd_ptlock_init(page));
+
+	return 0;
+}
+
+static void __init vmemmap_ptlock_init_section(unsigned long start_pfn)
+{
+	unsigned long section_nr;
+	struct mem_section *ms;
+	struct page *memmap, *memmap_end;
+	struct mm_struct *mm = &init_mm;
+
+	const struct mm_walk_ops ops = {
+		.pud_entry	= vmemmap_pud_entry,
+	};
+
+	section_nr = pfn_to_section_nr(start_pfn);
+	ms = __nr_to_section(section_nr);
+	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
+	memmap_end = memmap + PAGES_PER_SECTION;
+
+	mmap_read_lock(mm);
+	BUG_ON(walk_page_range_novma(mm, (unsigned long)memmap,
+				     (unsigned long)memmap_end,
+				     &ops, NULL, NULL));
+	mmap_read_unlock(mm);
+}
+
+static void __init vmemmap_ptlock_init_node(int nid)
+{
+	unsigned long pfn, end_pfn;
+	struct pglist_data *pgdat = NODE_DATA(nid);
+
+	pfn = pgdat->node_start_pfn;
+	end_pfn = pgdat_end_pfn(pgdat);
+
+	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
+		vmemmap_ptlock_init_section(pfn);
+}
+
+static int __init vmemmap_ptlock_init(void)
+{
+	int nid;
+
+	if (!hugepages_supported())
+		return 0;
+
+	for_each_online_node(nid)
+		vmemmap_ptlock_init_node(nid);
+
+	return 0;
+}
+core_initcall(vmemmap_ptlock_init);
-- 
2.11.0