btrfs: hold a ref on the root in scrub_print_warning_inode

We look up the root for the bytenr that is failing, so we need to hold a
ref on the root for that operation.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/scrub.c

@@ -658,6 +658,10 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 		ret = PTR_ERR(local_root);
 		goto err;
 	}
+	if (!btrfs_grab_fs_root(local_root)) {
+		ret = -ENOENT;
+		goto err;
+	}
 
 	/*
 	 * this makes the path point to (inum INODE_ITEM ioff)
@@ -668,6 +672,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 
 	ret = btrfs_search_slot(NULL, local_root, &key, swarn->path, 0, 0);
 	if (ret) {
+		btrfs_put_fs_root(local_root);
 		btrfs_release_path(swarn->path);
 		goto err;
 	}
@@ -688,6 +693,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 	ipath = init_ipath(4096, local_root, swarn->path);
 	memalloc_nofs_restore(nofs_flag);
 	if (IS_ERR(ipath)) {
+		btrfs_put_fs_root(local_root);
 		ret = PTR_ERR(ipath);
 		ipath = NULL;
 		goto err;
@@ -711,6 +717,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 				  min(isize - offset, (u64)PAGE_SIZE), nlink,
 				  (char *)(unsigned long)ipath->fspath->val[i]);
 
+	btrfs_put_fs_root(local_root);
 	free_ipath(ipath);
 	return 0;