[PATCH v3 02/14] mm: thp: create new __zap_huge_pmd_locked function.

[Zi Yan]

From: Zi Yan <z...@nvidia.com>

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

Signed-off-by: Zi Yan <zi....@cs.rutgers.edu>
---
 include/linux/huge_mm.h |  3 +++
 mm/huge_memory.c        | 27 ++++++++++++++++++---------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2036f69c8284..44ee130c7207 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -26,6 +26,9 @@ extern struct page *follow_trans_huge_pmd(struct 
vm_area_struct *vma,
 extern bool madvise_free_huge_pmd(struct mmu_gather *tlb,
                        struct vm_area_struct *vma,
                        pmd_t *pmd, unsigned long addr, unsigned long next);
+extern int __zap_huge_pmd_locked(struct mmu_gather *tlb,
+                       struct vm_area_struct *vma,
+                       pmd_t *pmd, unsigned long addr);
 extern int zap_huge_pmd(struct mmu_gather *tlb,
                        struct vm_area_struct *vma,
                        pmd_t *pmd, unsigned long addr);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cd66532ef667..d8e15fd817b0 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1590,17 +1590,12 @@ static inline void zap_deposited_table(struct mm_struct 
*mm, pmd_t *pmd)
        atomic_long_dec(&mm->nr_ptes);
 }
 
-int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+int __zap_huge_pmd_locked(struct mmu_gather *tlb, struct vm_area_struct *vma,
                 pmd_t *pmd, unsigned long addr)
 {
        pmd_t orig_pmd;
-       spinlock_t *ptl;
 
        tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
-
-       ptl = __pmd_trans_huge_lock(pmd, vma);
-       if (!ptl)
-               return 0;
        /*
         * For architectures like ppc64 we look at deposited pgtable
         * when calling pmdp_huge_get_and_clear. So do the
@@ -1611,13 +1606,11 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct 
vm_area_struct *vma,
                        tlb->fullmm);
        tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
        if (vma_is_dax(vma)) {
-               spin_unlock(ptl);
                if (is_huge_zero_pmd(orig_pmd))
                        tlb_remove_page_size(tlb, pmd_page(orig_pmd), 
HPAGE_PMD_SIZE);
        } else if (is_huge_zero_pmd(orig_pmd)) {
                pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
                atomic_long_dec(&tlb->mm->nr_ptes);
-               spin_unlock(ptl);
                tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
        } else {
                struct page *page = pmd_page(orig_pmd);
@@ -1635,9 +1628,25 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct 
vm_area_struct *vma,
                                zap_deposited_table(tlb->mm, pmd);
                        add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
                }
-               spin_unlock(ptl);
                tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
        }
+
+       return 1;
+}
+
+int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+                pmd_t *pmd, unsigned long addr)
+{
+       spinlock_t *ptl;
+
+
+       ptl = __pmd_trans_huge_lock(pmd, vma);
+       if (!ptl)
+               return 0;
+
+       __zap_huge_pmd_locked(tlb, vma, pmd, addr);
+
+       spin_unlock(ptl);
        return 1;
 }
 
-- 
2.11.0