[PATCH] zoned vm counters: remove useless struct wbs

Remove writeback state

We can remove some functions now that were needed to calculate the page state
for writeback control since these statistics are now directly available.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/page-writeback.c

@@ -99,23 +99,6 @@ EXPORT_SYMBOL(laptop_mode);
 
 static void background_writeout(unsigned long _min_pages);
 
-struct writeback_state
-{
-	unsigned long nr_dirty;
-	unsigned long nr_unstable;
-	unsigned long nr_mapped;
-	unsigned long nr_writeback;
-};
-
-static void get_writeback_state(struct writeback_state *wbs)
-{
-	wbs->nr_dirty = global_page_state(NR_FILE_DIRTY);
-	wbs->nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-	wbs->nr_mapped = global_page_state(NR_FILE_MAPPED) +
-				global_page_state(NR_ANON_PAGES);
-	wbs->nr_writeback = global_page_state(NR_WRITEBACK);
-}
-
 /*
  * Work out the current dirty-memory clamping and background writeout
  * thresholds.
@@ -134,8 +117,8 @@ static void get_writeback_state(struct writeback_state *wbs)
  * clamping level.
  */
 static void
-get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
-		struct address_space *mapping)
+get_dirty_limits(long *pbackground, long *pdirty,
+					struct address_space *mapping)
 {
 	int background_ratio;		/* Percentages */
 	int dirty_ratio;
@@ -145,8 +128,6 @@ get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
 	unsigned long available_memory = total_pages;
 	struct task_struct *tsk;
 
-	get_writeback_state(wbs);
-
 #ifdef CONFIG_HIGHMEM
 	/*
 	 * If this mapping can only allocate from low memory,
@@ -157,7 +138,9 @@ get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
 #endif
 
 
-	unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages;
+	unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) +
+				global_page_state(NR_ANON_PAGES)) * 100) /
+					total_pages;
 
 	dirty_ratio = vm_dirty_ratio;
 	if (dirty_ratio > unmapped_ratio / 2)
@@ -190,7 +173,6 @@ get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
  */
 static void balance_dirty_pages(struct address_space *mapping)
 {
-	struct writeback_state wbs;
 	long nr_reclaimable;
 	long background_thresh;
 	long dirty_thresh;
@@ -208,11 +190,12 @@ static void balance_dirty_pages(struct address_space *mapping)
 			.range_cyclic	= 1,
 		};
 
-		get_dirty_limits(&wbs, &background_thresh,
-					&dirty_thresh, mapping);
-		nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
-		if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
-			break;
+		get_dirty_limits(&background_thresh, &dirty_thresh, mapping);
+		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+					global_page_state(NR_UNSTABLE_NFS);
+		if (nr_reclaimable + global_page_state(NR_WRITEBACK) <=
+			dirty_thresh)
+				break;
 
 		if (!dirty_exceeded)
 			dirty_exceeded = 1;
@@ -225,11 +208,14 @@ static void balance_dirty_pages(struct address_space *mapping)
 		 */
 		if (nr_reclaimable) {
 			writeback_inodes(&wbc);
-			get_dirty_limits(&wbs, &background_thresh,
-					&dirty_thresh, mapping);
-			nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
-			if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
-				break;
+			get_dirty_limits(&background_thresh,
+					 	&dirty_thresh, mapping);
+			nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+					global_page_state(NR_UNSTABLE_NFS);
+			if (nr_reclaimable +
+				global_page_state(NR_WRITEBACK)
+					<= dirty_thresh)
+						break;
 			pages_written += write_chunk - wbc.nr_to_write;
 			if (pages_written >= write_chunk)
 				break;		/* We've done our duty */
@@ -237,8 +223,9 @@ static void balance_dirty_pages(struct address_space *mapping)
 		blk_congestion_wait(WRITE, HZ/10);
 	}
 
-	if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded)
-		dirty_exceeded = 0;
+	if (nr_reclaimable + global_page_state(NR_WRITEBACK)
+		<= dirty_thresh && dirty_exceeded)
+			dirty_exceeded = 0;
 
 	if (writeback_in_progress(bdi))
 		return;		/* pdflush is already working this queue */
@@ -300,12 +287,11 @@ EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
 
 void throttle_vm_writeout(void)
 {
-	struct writeback_state wbs;
 	long background_thresh;
 	long dirty_thresh;
 
         for ( ; ; ) {
-		get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
+		get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
 
                 /*
                  * Boost the allowable dirty threshold a bit for page
@@ -313,8 +299,9 @@ void throttle_vm_writeout(void)
                  */
                 dirty_thresh += dirty_thresh / 10;      /* wheeee... */
 
-                if (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh)
-                        break;
+                if (global_page_state(NR_UNSTABLE_NFS) +
+			global_page_state(NR_WRITEBACK) <= dirty_thresh)
+                        	break;
                 blk_congestion_wait(WRITE, HZ/10);
         }
 }
@@ -337,12 +324,12 @@ static void background_writeout(unsigned long _min_pages)
 	};
 
 	for ( ; ; ) {
-		struct writeback_state wbs;
 		long background_thresh;
 		long dirty_thresh;
 
-		get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
-		if (wbs.nr_dirty + wbs.nr_unstable < background_thresh
+		get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
+		if (global_page_state(NR_FILE_DIRTY) +
+			global_page_state(NR_UNSTABLE_NFS) < background_thresh
 				&& min_pages <= 0)
 			break;
 		wbc.encountered_congestion = 0;
@@ -366,12 +353,9 @@ static void background_writeout(unsigned long _min_pages)
  */
 int wakeup_pdflush(long nr_pages)
 {
-	if (nr_pages == 0) {
-		struct writeback_state wbs;
-
-		get_writeback_state(&wbs);
-		nr_pages = wbs.nr_dirty + wbs.nr_unstable;
-	}
+	if (nr_pages == 0)
+		nr_pages = global_page_state(NR_FILE_DIRTY) +
+				global_page_state(NR_UNSTABLE_NFS);
 	return pdflush_operation(background_writeout, nr_pages);
 }
 
@@ -402,7 +386,6 @@ static void wb_kupdate(unsigned long arg)
 	unsigned long start_jif;
 	unsigned long next_jif;
 	long nr_to_write;
-	struct writeback_state wbs;
 	struct writeback_control wbc = {
 		.bdi		= NULL,
 		.sync_mode	= WB_SYNC_NONE,
@@ -415,11 +398,11 @@ static void wb_kupdate(unsigned long arg)
 
 	sync_supers();
 
-	get_writeback_state(&wbs);
 	oldest_jif = jiffies - dirty_expire_interval;
 	start_jif = jiffies;
 	next_jif = start_jif + dirty_writeback_interval;
-	nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
+	nr_to_write = global_page_state(NR_FILE_DIRTY) +
+			global_page_state(NR_UNSTABLE_NFS) +
 			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
 	while (nr_to_write > 0) {
 		wbc.encountered_congestion = 0;