[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 <[e-mail]>

arch/s390/include/asm/page.h

···
 #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"
···
 		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;

arch/s390/include/asm/pgtable.h

···
 #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.
  */
···
 #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)
···
 	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);
···
 {
 	int dirty;
 	unsigned long *pgste;
+	unsigned long pfn;
 	struct page *page;
 	unsigned int skey;
 
···
 		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);
···
 	}
 	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;
 }
···
 					    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);
···
 	}								\
 	__changed;							\
 })
-
-/*
- * 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,

include/asm-generic/pgtable.h

···
 #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

include/linux/page-flags.h

···
 {
 #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,

mm/rmap.c

···
 			unlock_page(page);
 	}
 out:
-	if (page_test_and_clear_young(page))
+	if (page_test_and_clear_young(page_to_pfn(page)))
 		referenced++;
 
 	return referenced;
···
 		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;
-			}
 		}
 	}
 
···
 	 * 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.