[S390] merge page_test_dirty and page_clear_dirty

The page_clear_dirty primitive always sets the default storage key
which resets the access control bits and the fetch protection bit.
That will surprise a KVM guest that sets non-zero access control
bits or the fetch protection bit. Merge page_test_dirty and
page_clear_dirty back to a single function and only clear the
dirty bit from the storage key.

In addition move the function page_test_and_clear_dirty and
page_test_and_clear_young to page.h where they belong. This
requires to change the parameter from a struct page * to a page
frame number.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

5 files changed, 68 insertions, 71 deletions

diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 3c987e9ec8d..81ee2776088 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -107,8 +107,8 @@ typedef pte_t *pgtable_t;
 #define __pgd(x)        ((pgd_t) { (x) } )
 #define __pgprot(x)     ((pgprot_t) { (x) } )
 
-static inline void
-page_set_storage_key(unsigned long addr, unsigned int skey, int mapped)
+static inline void page_set_storage_key(unsigned long addr,
+                                        unsigned char skey, int mapped)
 {
         if (!mapped)
                 asm volatile(".insn rrf,0xb22b0000,%0,%1,8,0"
@@ -117,15 +117,59 @@ page_set_storage_key(unsigned long addr, unsigned int skey, int mapped)
                 asm volatile("sske %0,%1" : : "d" (skey), "a" (addr));
 }
 
-static inline unsigned int
-page_get_storage_key(unsigned long addr)
+static inline unsigned char page_get_storage_key(unsigned long addr)
 {
-        unsigned int skey;
+        unsigned char skey;
 
-        asm volatile("iske %0,%1" : "=d" (skey) : "a" (addr), "0" (0));
+        asm volatile("iske %0,%1" : "=d" (skey) : "a" (addr));
         return skey;
 }
 
+static inline int page_reset_referenced(unsigned long addr)
+{
+        unsigned int ipm;
+
+        asm volatile(
+                "       rrbe    0,%1\n"
+                "       ipm     %0\n"
+                : "=d" (ipm) : "a" (addr) : "cc");
+        return !!(ipm & 0x20000000);
+}
+
+/* Bits int the storage key */
+#define _PAGE_CHANGED           0x02    /* HW changed bit               */
+#define _PAGE_REFERENCED        0x04    /* HW referenced bit            */
+#define _PAGE_FP_BIT            0x08    /* HW fetch protection bit      */
+#define _PAGE_ACC_BITS          0xf0    /* HW access control bits       */
+
+/*
+ * Test and clear dirty bit in storage key.
+ * We can't clear the changed bit atomically. This is a potential
+ * race against modification of the referenced bit. This function
+ * should therefore only be called if it is not mapped in any
+ * address space.
+ */
+#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
+static inline int page_test_and_clear_dirty(unsigned long pfn, int mapped)
+{
+        unsigned char skey;
+
+        skey = page_get_storage_key(pfn << PAGE_SHIFT);
+        if (!(skey & _PAGE_CHANGED))
+                return 0;
+        page_set_storage_key(pfn << PAGE_SHIFT, skey & ~_PAGE_CHANGED, mapped);
+        return 1;
+}
+
+/*
+ * Test and clear referenced bit in storage key.
+ */
+#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
+static inline int page_test_and_clear_young(unsigned long pfn)
+{
+        return page_reset_referenced(pfn << PAGE_SHIFT);
+}
+
 struct page;
 void arch_free_page(struct page *page, int order);
 void arch_alloc_page(struct page *page, int order);
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 763620ec792..4ca4dd2b329 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -373,10 +373,6 @@ extern unsigned long VMALLOC_START;
 #define _ASCE_USER_BITS         (_ASCE_SPACE_SWITCH | _ASCE_PRIVATE_SPACE | \
                                  _ASCE_ALT_EVENT)
 
-/* Bits int the storage key */
-#define _PAGE_CHANGED    0x02          /* HW changed bit                   */
-#define _PAGE_REFERENCED 0x04          /* HW referenced bit                */
-
 /*
  * Page protection definitions.
  */
@@ -555,8 +551,6 @@ static inline void rcp_unlock(pte_t *ptep)
 #endif
 }
 
-/* forward declaration for SetPageUptodate in page-flags.h*/
-static inline void page_clear_dirty(struct page *page, int mapped);
 #include <linux/page-flags.h>
 
 static inline void ptep_rcp_copy(pte_t *ptep)
@@ -566,7 +560,7 @@ static inline void ptep_rcp_copy(pte_t *ptep)
         unsigned int skey;
         unsigned long *pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
 
-        skey = page_get_storage_key(page_to_phys(page));
+        skey = page_get_storage_key(pte_val(*ptep) >> PAGE_SHIFT);
         if (skey & _PAGE_CHANGED) {
                 set_bit_simple(RCP_GC_BIT, pgste);
                 set_bit_simple(KVM_UD_BIT, pgste);
@@ -760,6 +754,7 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
 {
         int dirty;
         unsigned long *pgste;
+        unsigned long pfn;
         struct page *page;
         unsigned int skey;
 
@@ -767,8 +762,9 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
                 return -EINVAL;
         rcp_lock(ptep);
         pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
-        page = virt_to_page(pte_val(*ptep));
-        skey = page_get_storage_key(page_to_phys(page));
+        pfn = pte_val(*ptep) >> PAGE_SHIFT;
+        page = pfn_to_page(pfn);
+        skey = page_get_storage_key(pfn);
         if (skey & _PAGE_CHANGED) {
                 set_bit_simple(RCP_GC_BIT, pgste);
                 set_bit_simple(KVM_UD_BIT, pgste);
@@ -779,7 +775,7 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
         }
         dirty = test_and_clear_bit_simple(KVM_UD_BIT, pgste);
         if (skey & _PAGE_CHANGED)
-                page_clear_dirty(page, 1);
+                page_set_storage_key(pfn, skey & ~_PAGE_CHANGED, 1);
         rcp_unlock(ptep);
         return dirty;
 }
@@ -790,16 +786,16 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
                                             unsigned long addr, pte_t *ptep)
 {
 #ifdef CONFIG_PGSTE
-        unsigned long physpage;
+        unsigned long pfn;
         int young;
         unsigned long *pgste;
 
         if (!vma->vm_mm->context.has_pgste)
                 return 0;
-        physpage = pte_val(*ptep) & PAGE_MASK;
+        pfn = pte_val(*ptep) >> PAGE_SHIFT;
         pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
 
-        young = ((page_get_storage_key(physpage) & _PAGE_REFERENCED) != 0);
+        young = ((page_get_storage_key(pfn) & _PAGE_REFERENCED) != 0);
         rcp_lock(ptep);
         if (young)
                 set_bit_simple(RCP_GR_BIT, pgste);
@@ -937,42 +933,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 })
 
 /*
- * Test and clear dirty bit in storage key.
- * We can't clear the changed bit atomically. This is a potential
- * race against modification of the referenced bit. This function
- * should therefore only be called if it is not mapped in any
- * address space.
- */
-#define __HAVE_ARCH_PAGE_TEST_DIRTY
-static inline int page_test_dirty(struct page *page)
-{
-        return (page_get_storage_key(page_to_phys(page)) & _PAGE_CHANGED) != 0;
-}
-
-#define __HAVE_ARCH_PAGE_CLEAR_DIRTY
-static inline void page_clear_dirty(struct page *page, int mapped)
-{
-        page_set_storage_key(page_to_phys(page), PAGE_DEFAULT_KEY, mapped);
-}
-
-/*
- * Test and clear referenced bit in storage key.
- */
-#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
-static inline int page_test_and_clear_young(struct page *page)
-{
-        unsigned long physpage = page_to_phys(page);
-        int ccode;
-
-        asm volatile(
-                "       rrbe    0,%1\n"
-                "       ipm     %0\n"
-                "       srl     %0,28\n"
-                : "=d" (ccode) : "a" (physpage) : "cc" );
-        return ccode & 2;
-}
-
-/*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  */
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index b4bfe338ea0..e9b8e5926be 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -184,22 +184,18 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
-#ifndef __HAVE_ARCH_PAGE_TEST_DIRTY
-#define page_test_dirty(page)           (0)
+#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
+#define page_test_and_clear_dirty(pfn, mapped)  (0)
 #endif
 
-#ifndef __HAVE_ARCH_PAGE_CLEAR_DIRTY
-#define page_clear_dirty(page, mapped)  do { } while (0)
-#endif
-
-#ifndef __HAVE_ARCH_PAGE_TEST_DIRTY
+#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
 #define pte_maybe_dirty(pte)            pte_dirty(pte)
 #else
 #define pte_maybe_dirty(pte)            (1)
 #endif
 
 #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
-#define page_test_and_clear_young(page) (0)
+#define page_test_and_clear_young(pfn) (0)
 #endif
 
 #ifndef __HAVE_ARCH_PGD_OFFSET_GATE
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 811183de1ef..79a6700b716 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -308,7 +308,7 @@ static inline void SetPageUptodate(struct page *page)
 {
 #ifdef CONFIG_S390
         if (!test_and_set_bit(PG_uptodate, &page->flags))
-                page_clear_dirty(page, 0);
+                page_set_storage_key(page_to_pfn(page), PAGE_DEFAULT_KEY, 0);
 #else
         /*
          * Memory barrier must be issued before setting the PG_uptodate bit,
diff --git a/mm/rmap.c b/mm/rmap.c
index 8da044a1db0..522e4a93cad 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -719,7 +719,7 @@ int page_referenced(struct page *page,
                         unlock_page(page);
         }
 out:
-        if (page_test_and_clear_young(page))
+        if (page_test_and_clear_young(page_to_pfn(page)))
                 referenced++;
 
         return referenced;
@@ -785,10 +785,8 @@ int page_mkclean(struct page *page)
                 struct address_space *mapping = page_mapping(page);
                 if (mapping) {
                         ret = page_mkclean_file(mapping, page);
-                        if (page_test_dirty(page)) {
-                                page_clear_dirty(page, 1);
+                        if (page_test_and_clear_dirty(page_to_pfn(page), 1))
                                 ret = 1;
-                        }
                 }
         }
 
@@ -981,10 +979,9 @@ void page_remove_rmap(struct page *page)
          * not if it's in swapcache - there might be another pte slot
          * containing the swap entry, but page not yet written to swap.
          */
-        if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) {
-                page_clear_dirty(page, 1);
+        if ((!PageAnon(page) || PageSwapCache(page)) &&
+            page_test_and_clear_dirty(page_to_pfn(page), 1))
                 set_page_dirty(page);
-        }
         /*
          * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
          * and not charged by memcg for now.