mm: save soft-dirty bits on file pages

Andy reported that if file page get reclaimed we lose the soft-dirty bit
if it was there, so save _PAGE_BIT_SOFT_DIRTY bit when page address get
encoded into pte entry.  Thus when #pf happens on such non-present pte
we can restore it back.

Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/include/asm/pgtable-2level.h b/arch/x86/include/asm/pgtable-2level.h
index f2b489c..3bf2dd0 100644 (file)
--- a/arch/x86/include/asm/pgtable-2level.h
+++ b/arch/x86/include/asm/pgtable-2level.h
@@ -55,9 +55,53 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
 #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
 #endif
 
+#ifdef CONFIG_MEM_SOFT_DIRTY
+
+/*
+ * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE, _PAGE_BIT_SOFT_DIRTY and
+ * _PAGE_BIT_PROTNONE are taken, split up the 28 bits of offset
+ * into this range.
+ */
+#define PTE_FILE_MAX_BITS      28
+#define PTE_FILE_SHIFT1                (_PAGE_BIT_PRESENT + 1)
+#define PTE_FILE_SHIFT2                (_PAGE_BIT_FILE + 1)
+#define PTE_FILE_SHIFT3                (_PAGE_BIT_PROTNONE + 1)
+#define PTE_FILE_SHIFT4                (_PAGE_BIT_SOFT_DIRTY + 1)
+#define PTE_FILE_BITS1         (PTE_FILE_SHIFT2 - PTE_FILE_SHIFT1 - 1)
+#define PTE_FILE_BITS2         (PTE_FILE_SHIFT3 - PTE_FILE_SHIFT2 - 1)
+#define PTE_FILE_BITS3         (PTE_FILE_SHIFT4 - PTE_FILE_SHIFT3 - 1)
+
+#define pte_to_pgoff(pte)                                              \
+       ((((pte).pte_low >> (PTE_FILE_SHIFT1))                          \
+         & ((1U << PTE_FILE_BITS1) - 1)))                              \
+       + ((((pte).pte_low >> (PTE_FILE_SHIFT2))                        \
+           & ((1U << PTE_FILE_BITS2) - 1))                             \
+          << (PTE_FILE_BITS1))                                         \
+       + ((((pte).pte_low >> (PTE_FILE_SHIFT3))                        \
+           & ((1U << PTE_FILE_BITS3) - 1))                             \
+          << (PTE_FILE_BITS1 + PTE_FILE_BITS2))                        \
+       + ((((pte).pte_low >> (PTE_FILE_SHIFT4)))                       \
+           << (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3))
+
+#define pgoff_to_pte(off)                                              \
+       ((pte_t) { .pte_low =                                           \
+        ((((off)) & ((1U << PTE_FILE_BITS1) - 1)) << PTE_FILE_SHIFT1)  \
+        + ((((off) >> PTE_FILE_BITS1)                                  \
+            & ((1U << PTE_FILE_BITS2) - 1))                            \
+           << PTE_FILE_SHIFT2)                                         \
+        + ((((off) >> (PTE_FILE_BITS1 + PTE_FILE_BITS2))               \
+            & ((1U << PTE_FILE_BITS3) - 1))                            \
+           << PTE_FILE_SHIFT3)                                         \
+        + ((((off) >>                                                  \
+             (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3)))      \
+           << PTE_FILE_SHIFT4)                                         \
+        + _PAGE_FILE })
+
+#else /* CONFIG_MEM_SOFT_DIRTY */
+
 /*
  * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE and _PAGE_BIT_PROTNONE are taken,
- * split up the 29 bits of offset into this range:
+ * split up the 29 bits of offset into this range.
  */
 #define PTE_FILE_MAX_BITS      29
 #define PTE_FILE_SHIFT1                (_PAGE_BIT_PRESENT + 1)
@@ -88,6 +132,8 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
            << PTE_FILE_SHIFT3)                                         \
         + _PAGE_FILE })
 
+#endif /* CONFIG_MEM_SOFT_DIRTY */
+
 /* Encode and de-code a swap entry */
 #if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE
 #define SWP_TYPE_BITS (_PAGE_BIT_FILE - _PAGE_BIT_PRESENT - 1)

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 4cc9f2b..81bb91b 100644 (file)
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -179,6 +179,9 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 /*
  * Bits 0, 6 and 7 are taken in the low part of the pte,
  * put the 32 bits of offset into the high part.
+ *
+ * For soft-dirty tracking 11 bit is taken from
+ * the low part of pte as well.
  */
 #define pte_to_pgoff(pte) ((pte).pte_high)
 #define pgoff_to_pte(off)                                              \

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index bd0518a..1c00631 100644 (file)
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -329,6 +329,21 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
        return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY);
 }
 
+static inline pte_t pte_file_clear_soft_dirty(pte_t pte)
+{
+       return pte_clear_flags(pte, _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_file_mksoft_dirty(pte_t pte)
+{
+       return pte_set_flags(pte, _PAGE_SOFT_DIRTY);
+}
+
+static inline int pte_file_soft_dirty(pte_t pte)
+{
+       return pte_flags(pte) & _PAGE_SOFT_DIRTY;
+}
+
 /*
  * Mask out unsupported bits in a present pgprot.  Non-present pgprots
  * can use those bits for other purposes, so leave them be.

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 5e8442f..f4843e0 100644 (file)
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -61,8 +61,10 @@
  * they do not conflict with each other.
  */
 
+#define _PAGE_BIT_SOFT_DIRTY   _PAGE_BIT_HIDDEN
+
 #ifdef CONFIG_MEM_SOFT_DIRTY
-#define _PAGE_SOFT_DIRTY       (_AT(pteval_t, 1) << _PAGE_BIT_HIDDEN)
+#define _PAGE_SOFT_DIRTY       (_AT(pteval_t, 1) << _PAGE_BIT_SOFT_DIRTY)
 #else
 #define _PAGE_SOFT_DIRTY       (_AT(pteval_t, 0))
 #endif

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e2d9bdc..a117207 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -736,6 +736,8 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
                ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY);
        } else if (is_swap_pte(ptent)) {
                ptent = pte_swp_clear_soft_dirty(ptent);
+       } else if (pte_file(ptent)) {
+               ptent = pte_file_clear_soft_dirty(ptent);
        }
 
        set_pte_at(vma->vm_mm, addr, pte, ptent);

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 2a7e0d1..0807ddf 100644 (file)
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -432,6 +432,21 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 {
        return pte;
 }
+
+static inline pte_t pte_file_clear_soft_dirty(pte_t pte)
+{
+       return pte;
+}
+
+static inline pte_t pte_file_mksoft_dirty(pte_t pte)
+{
+       return pte;
+}
+
+static inline int pte_file_soft_dirty(pte_t pte)
+{
+       return 0;
+}
 #endif
 
 #ifndef __HAVE_PFNMAP_TRACKING

diff --git a/mm/fremap.c b/mm/fremap.c
index 87da359..5bff081 100644 (file)
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -57,17 +57,22 @@ static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
                unsigned long addr, unsigned long pgoff, pgprot_t prot)
 {
        int err = -ENOMEM;
-       pte_t *pte;
+       pte_t *pte, ptfile;
        spinlock_t *ptl;
 
        pte = get_locked_pte(mm, addr, &ptl);
        if (!pte)
                goto out;
 
-       if (!pte_none(*pte))
+       ptfile = pgoff_to_pte(pgoff);
+
+       if (!pte_none(*pte)) {
+               if (pte_present(*pte) && pte_soft_dirty(*pte))
+                       pte_file_mksoft_dirty(ptfile);
                zap_pte(mm, vma, addr, pte);
+       }
 
-       set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
+       set_pte_at(mm, addr, pte, ptfile);
        /*
         * We don't need to run update_mmu_cache() here because the "file pte"
         * being installed by install_file_pte() is not a real pte - it's a

diff --git a/mm/memory.c b/mm/memory.c
index e98ecad..4026841 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1141,9 +1141,12 @@ again:
                                continue;
                        if (unlikely(details) && details->nonlinear_vma
                            && linear_page_index(details->nonlinear_vma,
-                                               addr) != page->index)
-                               set_pte_at(mm, addr, pte,
-                                          pgoff_to_pte(page->index));
+                                               addr) != page->index) {
+                               pte_t ptfile = pgoff_to_pte(page->index);
+                               if (pte_soft_dirty(ptent))
+                                       pte_file_mksoft_dirty(ptfile);
+                               set_pte_at(mm, addr, pte, ptfile);
+                       }
                        if (PageAnon(page))
                                rss[MM_ANONPAGES]--;
                        else {
@@ -3410,6 +3413,8 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                entry = mk_pte(page, vma->vm_page_prot);
                if (flags & FAULT_FLAG_WRITE)
                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+               else if (pte_file(orig_pte) && pte_file_soft_dirty(orig_pte))
+                       pte_mksoft_dirty(entry);
                if (anon) {
                        inc_mm_counter_fast(mm, MM_ANONPAGES);
                        page_add_new_anon_rmap(page, vma, address);

diff --git a/mm/rmap.c b/mm/rmap.c
index 83325b8..b2e29ac 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1405,8 +1405,12 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
                pteval = ptep_clear_flush(vma, address, pte);
 
                /* If nonlinear, store the file page offset in the pte. */
-               if (page->index != linear_page_index(vma, address))
-                       set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
+               if (page->index != linear_page_index(vma, address)) {
+                       pte_t ptfile = pgoff_to_pte(page->index);
+                       if (pte_soft_dirty(pteval))
+                               pte_file_mksoft_dirty(ptfile);
+                       set_pte_at(mm, address, pte, ptfile);
+               }
 
                /* Move the dirty bit to the physical page now the pte is gone. */
                if (pte_dirty(pteval))