thp: prepare for DAX huge pages

Add a vma_is_dax() helper macro to test whether the VMA is DAX, and use it
in zap_huge_pmd() and __split_huge_page_pmd().

[akpm@linux-foundation.org: fix build]
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 4f27d3d..9b51f9d 100644 (file)
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -18,4 +18,8 @@ int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb, iod)         dax_fault(vma, vmf, gb, iod)
 #define __dax_mkwrite(vma, vmf, gb, iod)       __dax_fault(vma, vmf, gb, iod)
 
+static inline bool vma_is_dax(struct vm_area_struct *vma)
+{
+       return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
+}
 #endif

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ca475df..9057241 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -16,6 +16,7 @@
 #include <linux/swap.h>
 #include <linux/shrinker.h>
 #include <linux/mm_inline.h>
+#include <linux/dax.h>
 #include <linux/kthread.h>
 #include <linux/khugepaged.h>
 #include <linux/freezer.h>
@@ -794,7 +795,7 @@ static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 }
 
 /* Caller must hold page table lock. */
-static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
                struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
                struct page *zero_page)
 {
@@ -1421,7 +1422,6 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
        int ret = 0;
 
        if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
-               struct page *page;
                pgtable_t pgtable;
                pmd_t orig_pmd;
                /*
@@ -1433,13 +1433,22 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
                orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
                                                        tlb->fullmm);
                tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
-               pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
+               if (vma_is_dax(vma)) {
+                       if (is_huge_zero_pmd(orig_pmd)) {
+                               pgtable = NULL;
+                       } else {
+                               spin_unlock(ptl);
+                               return 1;
+                       }
+               } else {
+                       pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
+               }
                if (is_huge_zero_pmd(orig_pmd)) {
                        atomic_long_dec(&tlb->mm->nr_ptes);
                        spin_unlock(ptl);
                        put_huge_zero_page();
                } else {
-                       page = pmd_page(orig_pmd);
+                       struct page *page = pmd_page(orig_pmd);
                        page_remove_rmap(page);
                        VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
                        add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
@@ -1448,7 +1457,8 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
                        spin_unlock(ptl);
                        tlb_remove_page(tlb, page);
                }
-               pte_free(tlb->mm, pgtable);
+               if (pgtable)
+                       pte_free(tlb->mm, pgtable);
                ret = 1;
        }
        return ret;
@@ -2914,7 +2924,7 @@ void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
                pmd_t *pmd)
 {
        spinlock_t *ptl;
-       struct page *page;
+       struct page *page = NULL;
        struct mm_struct *mm = vma->vm_mm;
        unsigned long haddr = address & HPAGE_PMD_MASK;
        unsigned long mmun_start;       /* For mmu_notifiers */
@@ -2927,25 +2937,25 @@ void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
 again:
        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
        ptl = pmd_lock(mm, pmd);
-       if (unlikely(!pmd_trans_huge(*pmd))) {
-               spin_unlock(ptl);
-               mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
-               return;
-       }
-       if (is_huge_zero_pmd(*pmd)) {
+       if (unlikely(!pmd_trans_huge(*pmd)))
+               goto unlock;
+       if (vma_is_dax(vma)) {
+               pmdp_huge_clear_flush(vma, haddr, pmd);
+       } else if (is_huge_zero_pmd(*pmd)) {
                __split_huge_zero_page_pmd(vma, haddr, pmd);
-               spin_unlock(ptl);
-               mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
-               return;
+       } else {
+               page = pmd_page(*pmd);
+               VM_BUG_ON_PAGE(!page_count(page), page);
+               get_page(page);
        }
-       page = pmd_page(*pmd);
-       VM_BUG_ON_PAGE(!page_count(page), page);
-       get_page(page);
+ unlock:
        spin_unlock(ptl);
        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 
-       split_huge_page(page);
+       if (!page)
+               return;
 
+       split_huge_page(page);
        put_page(page);
 
        /*