Re: [PATCH v6 06/16] xfs: Factor out xfs_attr_leaf_addname helper

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Jan 18, 2020 at 03:50:25PM -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, and move the commit into
> the calling function.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c | 83 ++++++++++++++++++++++++++++--------------------
>  1 file changed, 49 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index b0ec25b..9ed7e94 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -305,10 +305,30 @@ xfs_attr_set_args(
>  		}
>  	}
>  
> -	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
> +	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
>  		error = xfs_attr_leaf_addname(args);
> -	else
> -		error = xfs_attr_node_addname(args);
> +		if (error != -ENOSPC)
> +			return error;
> +
> +		/*
> +		 * Commit that transaction so that the node_addname()
> +		 * call can manage its own transactions.
> +		 */
> +		error = xfs_defer_finish(&args->trans);
> +		if (error)
> +			return error;
> +
> +		/*
> +		 * Commit the current trans (including the inode) and
> +		 * start a new one.
> +		 */
> +		error = xfs_trans_roll_inode(&args->trans, dp);
> +		if (error)
> +			return error;
> +
> +	}
> +
> +	error = xfs_attr_node_addname(args);
>  	return error;
>  }
>  
> @@ -607,21 +627,12 @@ 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).
> - */

These functions are complicated enough as they are now, please make sure
they all have comments laying out the expected input metadata states and
what output states result from them.

I /think/ this function takes an inode whose attr data is in leaf
format, and tries to add a new entry.  If that succeeds then we exit
with dirty inode and transaction.  If ENOSPC then we convert the attr
data to node format and exit w/ dirty inode + transaction, presuming
that the caller will try again with xfs_attr_node_addname?

>  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;
> -
> -	trace_xfs_attr_leaf_addname(args);
> +	int			retval, error;
>  
>  	/*
>  	 * Look up the given attribute in the leaf block.  Figure out if
> @@ -667,31 +678,35 @@ 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.
> +		 * Unless an error occurs, retain the -ENOSPC retval
>  		 */
>  		error = xfs_attr3_leaf_to_node(args);
>  		if (error)
>  			return error;
> -		error = xfs_defer_finish(&args->trans);
> -		if (error)
> -			return error;
> +	}
> +	return retval;
> +}
>  
> -		/*
> -		 * Commit the current trans (including the inode) and start
> -		 * a new one.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, dp);
> -		if (error)
> -			return error;
>  
> -		/*
> -		 * Fob the whole rest of the problem off on the Btree code.
> -		 */
> -		error = xfs_attr_node_addname(args);
> +/*
> + * 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)

STATIC int
xfs_attr_leaf_addname(
	struct xfs_da_args	*args)
{

Please fix the inconsistent style things as you touch them.

--D

> +{
> +	int			error, forkoff;
> +	struct xfs_buf		*bp = NULL;
> +	struct xfs_inode	*dp = args->dp;
> +
> +	trace_xfs_attr_leaf_addname(args);
> +
> +	error = xfs_attr_leaf_try_add(args, bp);
> +	if (error)
>  		return error;
> -	}
>  
>  	/*
>  	 * Commit the transaction that added the attr name so that
> -- 
> 2.7.4
>