btrfs: add readonly flag

setting the readonly flag prevents writes in case an error is detected

Signed-off-by: Arne Jansen <sensille@gmx.net>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b7373b1..ee90466 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2657,7 +2657,7 @@
 
 /* scrub.c */
 int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
-		    struct btrfs_scrub_progress *progress);
+		    struct btrfs_scrub_progress *progress, int readonly);
 int btrfs_scrub_pause(struct btrfs_root *root);
 int btrfs_scrub_pause_super(struct btrfs_root *root);
 int btrfs_scrub_continue(struct btrfs_root *root);