bcache: Track dirty data by stripe

To make background writeback aware of raid5/6 stripes, we first need to
track the amount of dirty data within each stripe - we do this by
breaking up the existing sectors_dirty into per stripe atomic_ts

Signed-off-by: Kent Overstreet <koverstreet@google.com>
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 6954699..017c95f 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -10,6 +10,7 @@
 #include "btree.h"
 #include "debug.h"
 #include "request.h"
+#include "writeback.h"
 
 #include <linux/cgroup.h>
 #include <linux/module.h>
@@ -1044,7 +1045,7 @@
 		closure_bio_submit(bio, cl, s->d);
 	} else {
 		s->op.cache_bio = bio;
-		bch_writeback_add(dc, bio_sectors(bio));
+		bch_writeback_add(dc);
 	}
 out:
 	closure_call(&s->op.cl, bch_insert_data, NULL, cl);