diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fceddbd..dac6653 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -351,6 +351,7 @@
 #define BTRFS_FS_STATE_ERROR		0
 #define BTRFS_FS_STATE_REMOUNTING	1
 #define BTRFS_FS_STATE_TRANS_ABORTED	2
+#define BTRFS_FS_STATE_DEV_REPLACING	3
 
 /* Super block flags */
 /* Errors detected */
@@ -1674,6 +1675,9 @@
 
 	atomic_t mutually_exclusive_operation_running;
 
+	struct percpu_counter bio_counter;
+	wait_queue_head_t replace_wait;
+
 	struct semaphore uuid_tree_rescan_sem;
 	unsigned int update_uuid_tree_gen:1;
 };
@@ -4008,6 +4012,11 @@
 int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
 			 struct btrfs_scrub_progress *progress);
 
+/* dev-replace.c */
+void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info);
+void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info);
+void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info);
+
 /* reada.c */
 struct reada_control {
 	struct btrfs_root	*root;		/* tree to prefetch */