drbd: Bugfix: rs_in_flight could become wrong if read_for_csum() requested reschedule later

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_worker.c

@@ -512,7 +512,7 @@ int w_make_resync_request(struct drbd_conf *mdev,
 	sector_t sector;
 	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
 	int max_segment_size;
-	int number, i, size, pe, mx;
+	int number, i, rollback_i, size, pe, mx;
 	int align, queued, sndbuf;
 
 	if (unlikely(cancel))
@@ -613,6 +613,7 @@ int w_make_resync_request(struct drbd_conf *mdev,
 		 * be prepared for all stripe sizes of software RAIDs.
 		 */
 		align = 1;
+		rollback_i = i;
 		for (;;) {
 			if (size + BM_BLOCK_SIZE > max_segment_size)
 				break;
@@ -654,6 +655,7 @@ int w_make_resync_request(struct drbd_conf *mdev,
 			case 2: /* Allocation failed */
 				drbd_rs_complete_io(mdev, sector);
 				mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
+				i = rollback_i;
 				goto requeue;
 			/* case 1: everything ok */
 			}