From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
DAX wants to use the 'special' bit to mark PMD entries that are not backed
by struct page, just as for PTEs. Add pmd_special() and pmd_mkspecial
for x86 (nb: also need to be added for other architectures). Prepare
do_huge_pmd_wp_page(), zap_huge_pmd() and __split_huge_page_pmd() to
handle pmd_special entries.
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/pgtable.h | 10 +++++++++
mm/huge_memory.c | 51 ++++++++++++++++++++++++++----------------
2 files changed, 42 insertions(+), 19 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index aa97a07..f4f42f2 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -302,6 +302,11 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
return pmd_clear_flags(pmd, _PAGE_PRESENT);
}
+static inline pmd_t pmd_mkspecial(pmd_t pmd)
+{
+ return pmd_set_flags(pmd, _PAGE_SPECIAL);
+}
+
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
static inline int pte_soft_dirty(pte_t pte)
{
@@ -504,6 +509,11 @@ static inline int pmd_none(pmd_t pmd)
return (unsigned long)native_pmd_val(pmd) == 0;
}
+static inline int pmd_special(pmd_t pmd)
+{
+ return (pmd_flags(pmd) & _PAGE_SPECIAL) && pmd_present(pmd);
+}
+
static inline unsigned long pmd_page_vaddr(pmd_t pmd)
{
return (unsigned long)__va(pmd_val(pmd) & PTE_PFN_MASK);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a56ddd..ad09fc1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1096,7 +1096,6 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long mmun_end; /* For mmu_notifiers */
ptl = pmd_lockptr(mm, pmd);
- VM_BUG_ON(!vma->anon_vma);
haddr = address & HPAGE_PMD_MASK;
if (is_huge_zero_pmd(orig_pmd))
goto alloc;
@@ -1104,9 +1103,20 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (unlikely(!pmd_same(*pmd, orig_pmd)))
goto out_unlock;
- page = pmd_page(orig_pmd);
- VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
- if (page_mapcount(page) == 1) {
+ if (pmd_special(orig_pmd)) {
+ /* VM_MIXEDMAP !pfn_valid() case */
+ if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) !=
+ (VM_WRITE|VM_SHARED)) {
+ pmdp_clear_flush(vma, haddr, pmd);
+ ret = VM_FAULT_FALLBACK;
+ goto out_unlock;
+ }
+ } else {
+ VM_BUG_ON(!vma->anon_vma);
+ page = pmd_page(orig_pmd);
+ VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
+ }
+ if (!page || page_mapcount(page) == 1) {
pmd_t entry;
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
@@ -1391,7 +1401,6 @@ 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;
/*
@@ -1402,13 +1411,17 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
*/
orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ if (pmd_special(orig_pmd)) {
+ spin_unlock(ptl);
+ return 1;
+ }
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);
@@ -2860,7 +2873,7 @@ 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 */
@@ -2873,25 +2886,25 @@ 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 (unlikely(!pmd_trans_huge(*pmd)))
+ goto unlock;
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 if (pmd_special(*pmd)) {
+ pmdp_clear_flush(vma, haddr, pmd);
+ } 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);
/*
--
2.1.0
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