[PATCH v3 01/14] mm: thp: make __split_huge_pmd_locked visible.

[Zi Yan]

From: Zi Yan <ziy@xxxxxxxxxx>

It allows splitting huge pmd while you are holding the pmd lock.
It is prepared for future zap_pmd_range() use.

Signed-off-by: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
---
 include/linux/huge_mm.h |  2 ++
 mm/huge_memory.c        | 22 ++++++++++++----------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a3762d49ba39..2036f69c8284 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -120,6 +120,8 @@ static inline int split_huge_page(struct page *page)
 }
 void deferred_split_huge_page(struct page *page);
 
+void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
+		unsigned long haddr, bool freeze);
 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long address, bool freeze, struct page *page);
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 03e4566fc226..cd66532ef667 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1877,8 +1877,8 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
 	pmd_populate(mm, pmd, pgtable);
 }
 
-static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
-		unsigned long haddr, bool freeze)
+void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
+		unsigned long address, bool freeze)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct page *page;
@@ -1887,6 +1887,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 	bool young, write, dirty, soft_dirty;
 	unsigned long addr;
 	int i;
+	unsigned long haddr = address & HPAGE_PMD_MASK;
 
 	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
 	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
@@ -1895,6 +1896,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 
 	count_vm_event(THP_SPLIT_PMD);
 
+	mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
+
 	if (!vma_is_anonymous(vma)) {
 		_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
 		/*
@@ -1904,16 +1907,17 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		if (arch_needs_pgtable_deposit())
 			zap_deposited_table(mm, pmd);
 		if (vma_is_dax(vma))
-			return;
+			goto out;
 		page = pmd_page(_pmd);
 		if (!PageReferenced(page) && pmd_young(_pmd))
 			SetPageReferenced(page);
 		page_remove_rmap(page, true);
 		put_page(page);
 		add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
-		return;
+		goto out;
 	} else if (is_huge_zero_pmd(*pmd)) {
-		return __split_huge_zero_page_pmd(vma, haddr, pmd);
+		__split_huge_zero_page_pmd(vma, haddr, pmd);
+		goto out;
 	}
 
 	page = pmd_page(*pmd);
@@ -2010,6 +2014,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 			put_page(page + i);
 		}
 	}
+out:
+	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
 }
 
 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
@@ -2017,11 +2023,8 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 {
 	spinlock_t *ptl;
 	struct mm_struct *mm = vma->vm_mm;
-	unsigned long haddr = address & HPAGE_PMD_MASK;
 
-	mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
 	ptl = pmd_lock(mm, pmd);
-
 	/*
 	 * If caller asks to setup a migration entries, we need a page to check
 	 * pmd against. Otherwise we can end up replacing wrong page.
@@ -2036,10 +2039,9 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			clear_page_mlock(page);
 	} else if (!pmd_devmap(*pmd))
 		goto out;
-	__split_huge_pmd_locked(vma, pmd, haddr, freeze);
+	__split_huge_pmd_locked(vma, pmd, address, freeze);
 out:
 	spin_unlock(ptl);
-	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
 }
 
 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
-- 
2.11.0