Re: [PATCH 1/2] btrfs: free fs roots on failed mount

[David Sterba <dsterba@suse.cz>]

On Wed, Jul 22, 2020 at 12:07:21PM -0400, Josef Bacik wrote:
> While testing a weird problem with -o degraded, I noticed I was getting
> leaked root errors
> 
> BTRFS warning (device loop0): writable mount is not allowed due to too many missing devices
> BTRFS error (device loop0): open_ctree failed
> BTRFS error (device loop0): leaked root -9-0 refcount 1
> 
> This is the DATA_RELOC root, which gets read before the other fs roots,
> but is included in the fs roots radix tree, and thus gets freed by
> btrfs_free_fs_roots.  Fix this by moving the call into fail_tree_roots:
> in open_ctree.  With this fix we no longer leak that root on mount
> failure.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/disk-io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index c850d7f44fbe..f1fdbdd44c02 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3421,7 +3421,6 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
>  fail_trans_kthread:
>  	kthread_stop(fs_info->transaction_kthread);
>  	btrfs_cleanup_transaction(fs_info);
> -	btrfs_free_fs_roots(fs_info);
>  fail_cleaner:
>  	kthread_stop(fs_info->cleaner_kthread);
>  
> @@ -3441,6 +3440,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
>  	btrfs_put_block_group_cache(fs_info);
>  
>  fail_tree_roots:
> +	btrfs_free_fs_roots(fs_info);
>  	free_root_pointers(fs_info, true);

The data reloc tree is freed inside free_root_pointers, that it's also
in the radix tree is for convenience so I'd rather fix it inside
free_root_pointers and not reorder btrfs_free_fs_roots.

>  	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
>  
> -- 
> 2.24.1