btrfs: convert btrfs_inc_block_group_ro to accept fs_info

btrfs_inc_block_group_ro is either passed the extent root or the dev
root, but it doesn't do anything with the dev tree.  Let's convert
to passing an fs_info and using the extent root.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -2729,7 +2729,7 @@ int btrfs_cond_migrate_bytes(struct btrfs_fs_info *fs_info,
 void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
 			     struct btrfs_block_rsv *block_rsv,
 			     u64 num_bytes);
-int btrfs_inc_block_group_ro(struct btrfs_root *root,
+int btrfs_inc_block_group_ro(struct btrfs_fs_info *fs_info,
 			     struct btrfs_block_group_cache *cache);
 void btrfs_dec_block_group_ro(struct btrfs_block_group_cache *cache);
 void btrfs_put_block_group_cache(struct btrfs_fs_info *info);

fs/btrfs/extent-tree.c

@@ -9359,17 +9359,16 @@ static int inc_block_group_ro(struct btrfs_block_group_cache *cache, int force)
 	return ret;
 }
 
-int btrfs_inc_block_group_ro(struct btrfs_root *root,
+int btrfs_inc_block_group_ro(struct btrfs_fs_info *fs_info,
 			     struct btrfs_block_group_cache *cache)
 
 {
-	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_trans_handle *trans;
 	u64 alloc_flags;
 	int ret;
 
 again:
-	trans = btrfs_join_transaction(root);
+	trans = btrfs_join_transaction(fs_info->extent_root);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);
 

fs/btrfs/relocation.c

@@ -4334,7 +4334,7 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 	rc->block_group = btrfs_lookup_block_group(fs_info, group_start);
 	BUG_ON(!rc->block_group);
 
-	ret = btrfs_inc_block_group_ro(extent_root, rc->block_group);
+	ret = btrfs_inc_block_group_ro(fs_info, rc->block_group);
 	if (ret) {
 		err = ret;
 		goto out;

fs/btrfs/scrub.c

@@ -3582,7 +3582,7 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 		 * -> btrfs_scrub_pause()
 		 */
 		scrub_pause_on(fs_info);
-		ret = btrfs_inc_block_group_ro(root, cache);
+		ret = btrfs_inc_block_group_ro(fs_info, cache);
 		if (!ret && is_dev_replace) {
 			/*
 			 * If we are doing a device replace wait for any tasks