[PATCH] s390: lost dirty bits

The SetPageUptodate function is called for pages that are already up to
date.  The arch_set_page_uptodate function of s390 may not clear the dirty
bit in that case otherwise a dirty bit which is set between the start of an
i/o for a writeback and a following call to SetPageUptodate is lost.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-s390/pgtable.h

@@ -654,9 +654,11 @@ static inline pte_t mk_pte_phys(unsigned long physpage, pgprot_t pgprot)
 	__pte;                                                            \
 })
 
-#define arch_set_page_uptodate(__page)					  \
+#define SetPageUptodate(_page) \
 	do {								  \
-		asm volatile ("sske %0,%1" : : "d" (0),			  \
+		struct page *__page = (_page);				  \
+		if (!test_and_set_bit(PG_uptodate, &__page->flags))	  \
+			asm volatile ("sske %0,%1" : : "d" (0),		  \
 			      "a" (__pa((__page-mem_map) << PAGE_SHIFT)));\
 	} while (0)
 

include/linux/page-flags.h

@@ -194,16 +194,10 @@ extern unsigned long __read_page_state(unsigned offset);
 #define ClearPageReferenced(page)	clear_bit(PG_referenced, &(page)->flags)
 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
 
-#ifndef arch_set_page_uptodate
-#define arch_set_page_uptodate(page) do { } while (0)
-#endif
-
 #define PageUptodate(page)	test_bit(PG_uptodate, &(page)->flags)
-#define SetPageUptodate(page) \
-	do {								\
-		arch_set_page_uptodate(page);				\
-		set_bit(PG_uptodate, &(page)->flags);			\
-	} while (0)
+#ifndef SetPageUptodate
+#define SetPageUptodate(page)	set_bit(PG_uptodate, &(page)->flags)
+#endif
 #define ClearPageUptodate(page)	clear_bit(PG_uptodate, &(page)->flags)
 
 #define PageDirty(page)		test_bit(PG_dirty, &(page)->flags)