[PATCHv4 11/12] mm: Use updated pmdp_invalidate() interface to track dirty/accessed bits

Kirill A. Shutemov
2017-12-13T10:57:55Z

This patch uses modifed pmdp_invalidate(), that return previous value of pmd,
to transfer dirty and accessed bits.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/proc/task_mmu.c | 8 ++++----
mm/huge_memory.c | 29 ++++++++++++-----------------
2 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 339e4c1c044d..b4408c642fec 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -977,14 +977,14 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)
{
- pmd_t pmd = *pmdp;
+ pmd_t old, pmd = *pmdp;

if (pmd_present(pmd)) {
/* See comment in change_huge_pmd() */
- pmdp_invalidate(vma, addr, pmdp);
- if (pmd_dirty(*pmdp))
+ old = pmdp_invalidate(vma, addr, pmdp);
+ if (pmd_dirty(old))
pmd = pmd_mkdirty(pmd);
- if (pmd_young(*pmdp))
+ if (pmd_young(old))
pmd = pmd_mkyoung(pmd);

pmd = pmd_wrprotect(pmd);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2f2f5e774902..10278d03d60f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1910,17 +1910,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
* pmdp_invalidate() is required to make sure we don't miss
* dirty/young flags set by hardware.
*/
- entry = *pmd;
- pmdp_invalidate(vma, addr, pmd);
-
- /*
- * Recover dirty/young flags. It relies on pmdp_invalidate to not
- * corrupt them.
- */
- if (pmd_dirty(*pmd))
- entry = pmd_mkdirty(entry);
- if (pmd_young(*pmd))
- entry = pmd_mkyoung(entry);
+ entry = pmdp_invalidate(vma, addr, pmd);

entry = pmd_modify(entry, newprot);
if (preserve_write)
@@ -2073,8 +2063,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
struct mm_struct *mm = vma->vm_mm;
struct page *page;
pgtable_t pgtable;
- pmd_t _pmd;
- bool young, write, dirty, soft_dirty, pmd_migration = false;
+ pmd_t old, _pmd;
+ bool young, write, soft_dirty, pmd_migration = false;
unsigned long addr;
int i;

@@ -2130,7 +2120,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
page_ref_add(page, HPAGE_PMD_NR - 1);
write = pmd_write(*pmd);
young = pmd_young(*pmd);
- dirty = pmd_dirty(*pmd);
soft_dirty = pmd_soft_dirty(*pmd);

pmdp_huge_split_prepare(vma, haddr, pmd);
@@ -2160,8 +2149,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
if (soft_dirty)
entry = pte_mksoft_dirty(entry);
}
- if (dirty)
- SetPageDirty(page + i);
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
@@ -2210,7 +2197,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
* and finally we write the non-huge version of the pmd entry with
* pmd_populate.
*/
- pmdp_invalidate(vma, haddr, pmd);
+ old = pmdp_invalidate(vma, haddr, pmd);
+
+ /*
+ * Transfer dirty bit using value returned by pmd_invalidate() to be
+ * sure we don't race with CPU that can set the bit under us.
+ */
+ if (pmd_dirty(old))
+ SetPageDirty(page);
+
pmd_populate(mm, pmd, pgtable);

if (freeze) {
--
2.15.0

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