Re: [PATCH v3 07/19] xfs: Factor out xfs_attr_leaf_addname helper

[Brian Foster <bfoster@redhat.com>]

On Thu, Sep 05, 2019 at 03:18:25PM -0700, Allison Collins wrote:
> Factor out new helper function xfs_attr_leaf_try_add.
> Because new delayed attribute routines cannot roll
> transactions, we carve off the parts of
> xfs_attr_leaf_addname that we can use.  This will help
> to reduce repetitive code later when we introduce
> delayed attributes.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c | 43 +++++++++++++++++++++++++++++--------------
>  1 file changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 7a6dd37..f27e2c6 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -593,19 +593,12 @@ xfs_attr_shortform_addname(xfs_da_args_t *args)
>   * External routines when attribute list is one block
>   *========================================================================*/
>  
> -/*
> - * Add a name to the leaf attribute list structure
> - *
> - * 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).
> - */
>  STATIC int
> -xfs_attr_leaf_addname(
> -	struct xfs_da_args	*args)
> +xfs_attr_leaf_try_add(
> +	struct xfs_da_args	*args,
> +	struct xfs_buf		*bp)
>  {
> -	struct xfs_buf		*bp;
> -	int			retval, error, forkoff;
> -	struct xfs_inode	*dp = args->dp;
> +	int			retval, error;

It looks like we could pick either retval or error and use it
consistently throughout the new function.

>  
>  	trace_xfs_attr_leaf_addname(args);
>  

I also wonder if this tracepoint should remain in the caller.

> @@ -650,13 +643,35 @@ xfs_attr_leaf_addname(
>  	retval = xfs_attr3_leaf_add(bp, args);
>  	if (retval == -ENOSPC) {
>  		/*
> -		 * Promote the attribute list to the Btree format, then
> -		 * Commit that transaction so that the node_addname() call
> -		 * can manage its own transactions.
> +		 * Promote the attribute list to the Btree format.
>  		 */
>  		error = xfs_attr3_leaf_to_node(args);
>  		if (error)
>  			return error;
> +	}
> +	return retval;
> +}
> +
> +
> +/*
> + * Add a name to the leaf attribute list structure
> + *
> + * 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).
> + */
> +STATIC int
> +xfs_attr_leaf_addname(struct xfs_da_args	*args)
> +{
> +	int			retval, error, forkoff;
> +	struct xfs_buf		*bp = NULL;
> +	struct xfs_inode	*dp = args->dp;
> +
> +	retval = xfs_attr_leaf_try_add(args, bp);
> +	if (retval == -ENOSPC) {
> +		/*
> +		 * Commit that transaction so that the node_addname() call
> +		 * can manage its own transactions.
> +		 */
>  		error = xfs_defer_finish(&args->trans);
>  		if (error)
>  			return error;

Hmm.. I find this bit of factoring a little strange. We do part of the
-ENOSPC handling (leaf to node) in one place and another part
(xfs_defer_finish()) in the caller. I'm assuming we intentionally don't
finish dfops in the new helper because the delayed attr bits shouldn't
do that, but I'm wondering whether the helper should just return -ENOSPC
and the caller should be responsible for whatever needs to happen based
on that in the associated context. Hm?

Brian

> -- 
> 2.7.4
>