Re: [PATCH v4] btrfs: Fix transaction abort during failure in btrfs_rm_dev_item

[Edmund Nadolski <enadolski@suse.de>]

On 10/23/2017 12:58 AM, Nikolay Borisov wrote:
> btrfs_rm_dev_item calls several function under an activa transaction, however
                                                    ^^
active

> it fails to abort it if an error happens. Fix this by adding explicit
> btrfs_abort_transaction/btrfs_end_transaction calls
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
> V4:
>  * Reorder the code a bit to prevent duplication of btrfs_free_path 
>  invocation. 
> 
>  * Collapse the handling of btrfs_search_slot return value in a single if
>  branch rather than having it spread across 2 branches 
> 
> V3:
>  * The path needs to be freed before the the transaction is comitted otherwise 
>   we will deadlock.
>  fs/btrfs/volumes.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 0e8f16c305df..8b139d203f8c 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1765,20 +1765,24 @@ static int btrfs_rm_dev_item(struct btrfs_fs_info *fs_info,
>  	key.offset = device->devid;
>  
>  	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
> -	if (ret < 0)
> -		goto out;
> -
> -	if (ret > 0) {
> -		ret = -ENOENT;
> +	if (ret) {
> +		if (ret > 0)
> +			ret = -ENOENT;
> +		btrfs_abort_transaction(trans, ret);
> +		btrfs_end_transaction(trans);
>  		goto out;
>  	}
>  
>  	ret = btrfs_del_item(trans, root, path);
> -	if (ret)
> -		goto out;
> +	if (ret) {
> +		btrfs_abort_transaction(trans, ret);
> +		btrfs_end_transaction(trans);
> +	}
> +
>  out:
>  	btrfs_free_path(path);
> -	btrfs_commit_transaction(trans);
> +	if (!ret)
> +		ret = btrfs_commit_transaction(trans);
>  	return ret;
>  }
>  
> 

Perhaps slightly simpler (and the 'out:' label maybe goes away):

	.....
	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0)
		ret = -ENOENT;
	else if (!ret)
		ret = btrfs_del_item(trans, root, path);

	if (ret) {
		btrfs_abort_transaction(trans, ret);
		btrfs_end_transaction(trans);
	}
out:
	.....


Ed