[PATCH v3 08/21] mm/vmemmap: Initialize page table lock for vmemmap

[Muchun Song]

In the register_page_bootmem_memmap, the slab allocator is not ready
yet. So when ALLOC_SPLIT_PTLOCKS, we use init_mm.page_table_lock.
otherwise we use per page table lock(page->ptl). In the later patch,
we will use the vmemmap page table lock to guard the splitting of
the vmemmap huge PMD.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 arch/x86/mm/init_64.c |  2 ++
 include/linux/mm.h    | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0435bee2e172..a010101bbe24 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1610,6 +1610,8 @@ void register_page_bootmem_memmap(unsigned long section_nr,
 		}
 		get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
 
+		vmemmap_ptlock_init(pud_page(*pud));
+
 		if (!boot_cpu_has(X86_FEATURE_PSE)) {
 			next = (addr + PAGE_SIZE) & PAGE_MASK;
 			pmd = pmd_offset(pud, addr);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a12354e63e49..ce429614d1ab 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2169,6 +2169,26 @@ static inline bool ptlock_init(struct page *page)
 	return true;
 }
 
+#if ALLOC_SPLIT_PTLOCKS
+static inline void vmemmap_ptlock_init(struct page *page)
+{
+}
+#else
+static inline void vmemmap_ptlock_init(struct page *page)
+{
+	/*
+	 * prep_new_page() initialize page->private (and therefore page->ptl)
+	 * with 0. Make sure nobody took it in use in between.
+	 *
+	 * It can happen if arch try to use slab for page table allocation:
+	 * slab code uses page->{s_mem, counters}, which share storage with
+	 * page->ptl.
+	 */
+	VM_BUG_ON_PAGE(*(unsigned long *)&page->ptl, page);
+	spin_lock_init(ptlock_ptr(page));
+}
+#endif
+
 #else	/* !USE_SPLIT_PTE_PTLOCKS */
 /*
  * We use mm->page_table_lock to guard all pagetable pages of the mm.
@@ -2180,6 +2200,7 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
 static inline void ptlock_cache_init(void) {}
 static inline bool ptlock_init(struct page *page) { return true; }
 static inline void ptlock_free(struct page *page) {}
+static inline void vmemmap_ptlock_init(struct page *page) {}
 #endif /* USE_SPLIT_PTE_PTLOCKS */
 
 static inline void pgtable_init(void)
@@ -2244,6 +2265,18 @@ static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
 	return ptlock_ptr(pmd_to_page(pmd));
 }
 
+#if ALLOC_SPLIT_PTLOCKS
+static inline spinlock_t *vmemmap_pmd_lockptr(pmd_t *pmd)
+{
+	return &init_mm.page_table_lock;
+}
+#else
+static inline spinlock_t *vmemmap_pmd_lockptr(pmd_t *pmd)
+{
+	return ptlock_ptr(pmd_to_page(pmd));
+}
+#endif
+
 static inline bool pmd_ptlock_init(struct page *page)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -2269,6 +2302,11 @@ static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
 	return &mm->page_table_lock;
 }
 
+static inline spinlock_t *vmemmap_pmd_lockptr(pmd_t *pmd)
+{
+	return &init_mm.page_table_lock;
+}
+
 static inline bool pmd_ptlock_init(struct page *page) { return true; }
 static inline void pmd_ptlock_free(struct page *page) {}
 
@@ -2283,6 +2321,13 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
 	return ptl;
 }
 
+static inline spinlock_t *vmemmap_pmd_lock(pmd_t *pmd)
+{
+	spinlock_t *ptl = vmemmap_pmd_lockptr(pmd);
+	spin_lock(ptl);
+	return ptl;
+}
+
 static inline bool pgtable_pmd_page_ctor(struct page *page)
 {
 	if (!pmd_ptlock_init(page))
-- 
2.11.0