Re: [PATCH 1/3] xfs: make attr lookup returns consistent

[Christoph Hellwig <hch@infradead.org>]

On Wed, Aug 28, 2019 at 02:23:48PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Shortform, leaf and remote value attr value retrieval return
> different values for success. This makes it more complex to handle
> actual errors xfs_attr_get() as some errors mean success and some
> mean failure. Make the return values consistent for success and
> failure consistent for all attribute formats.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c        | 57 +++++++++++++++++++++------------
>  fs/xfs/libxfs/xfs_attr_leaf.c   | 15 ++++++---
>  fs/xfs/libxfs/xfs_attr_remote.c |  2 ++
>  fs/xfs/scrub/attr.c             |  2 --
>  4 files changed, 49 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index d48fcf11cc35..776343c4f22b 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -97,7 +97,10 @@ xfs_inode_hasattr(
>   * Overall external interface routines.
>   *========================================================================*/
>  
> -/* Retrieve an extended attribute and its value.  Must have ilock. */
> +/*
> + * Retrieve an extended attribute and its value.  Must have ilock.
> + * Returns 0 on successful retrieval, otherwise an error.
> + */
>  int
>  xfs_attr_get_ilocked(
>  	struct xfs_inode	*ip,
> @@ -147,7 +150,7 @@ xfs_attr_get(
>  	xfs_iunlock(ip, lock_mode);
>  
>  	*valuelenp = args.valuelen;
> -	return error == -EEXIST ? 0 : error;
> +	return error;
>  }
>  
>  /*
> @@ -768,6 +771,8 @@ xfs_attr_leaf_removename(
>   *
>   * This leaf block cannot have a "remote" value, we only call this routine
>   * if bmap_one_block() says there is only one block (ie: no remote blks).
> + *
> + * Returns 0 on successful retrieval, otherwise an error.
>   */
>  STATIC int
>  xfs_attr_leaf_get(xfs_da_args_t *args)
> @@ -789,10 +794,15 @@ xfs_attr_leaf_get(xfs_da_args_t *args)
>  	}
>  	error = xfs_attr3_leaf_getvalue(bp, args);
>  	xfs_trans_brelse(args->trans, bp);
> -	if (!error && (args->rmtblkno > 0) && !(args->flags & ATTR_KERNOVAL)) {
> -		error = xfs_attr_rmtval_get(args);
> -	}
> -	return error;
> +	if (error)
> +		return error;
> +
> +	/* check if we have to retrieve a remote attribute to get the value */
> +	if (args->flags & ATTR_KERNOVAL)
> +		return 0;
> +	if (!args->rmtblkno)
> +		return 0;
> +	return xfs_attr_rmtval_get(args);
>  }
>  
>  /*========================================================================
> @@ -1268,11 +1278,13 @@ xfs_attr_refillstate(xfs_da_state_t *state)
>  }
>  
>  /*
> - * Look up a filename in a node attribute list.
> + * Retreive the attribute data from a node attribute list.
>   *
>   * This routine gets called for any attribute fork that has more than one
>   * block, ie: both true Btree attr lists and for single-leaf-blocks with
>   * "remote" values taking up more blocks.
> + *
> + * Returns 0 on successful retrieval, otherwise an error.
>   */
>  STATIC int
>  xfs_attr_node_get(xfs_da_args_t *args)
> @@ -1289,29 +1301,32 @@ xfs_attr_node_get(xfs_da_args_t *args)
>  	state->mp = args->dp->i_mount;
>  
>  	/*
> -	 * Search to see if name exists, and get back a pointer to it.
> +	  Search to see if name exists, and get back a pointer to it.
>  	 */
>  	error = xfs_da3_node_lookup_int(state, &retval);
>  	if (error) {
>  		retval = error;

Given that you are cleaning up this mess, can you check if there
is any point in the weird xfs_da3_node_lookup_int calling conventions?
It looks like it can return errnos in both the return value and
*revtval, and from a quick check it seems like all callers treat them
more or less the same.