linux-kernel - Re: [PATCH v5 03/11] powerpc/pseries/iommu: Add iommu_pseries_alloc

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Date:   Mon, 19 Jul 2021 16:04:33 +0200
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        kernel test robot <lkp@...el.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 03/11] powerpc/pseries/iommu: Add
 iommu_pseries_alloc_table() helper



On 16/07/2021 10:27, Leonardo Bras wrote:
> Creates a helper to allow allocating a new iommu_table without the need
> to reallocate the iommu_group.
> 
> This will be helpful for replacing the iommu_table for the new DMA window,
> after we remove the old one with iommu_tce_table_put().
> 
> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> Reviewed-by: Alexey Kardashevskiy <aik@...abs.ru>
> ---
>   arch/powerpc/platforms/pseries/iommu.c | 25 ++++++++++++++-----------
>   1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index b1b8d12bab39..33d82865d6e6 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -53,28 +53,31 @@ enum {
>   	DDW_EXT_QUERY_OUT_SIZE = 2
>   };
>   
> -static struct iommu_table_group *iommu_pseries_alloc_group(int node)
> +static struct iommu_table *iommu_pseries_alloc_table(int node)
>   {
> -	struct iommu_table_group *table_group;
>   	struct iommu_table *tbl;
>   
> -	table_group = kzalloc_node(sizeof(struct iommu_table_group), GFP_KERNEL,
> -			   node);
> -	if (!table_group)
> -		return NULL;
> -
>   	tbl = kzalloc_node(sizeof(struct iommu_table), GFP_KERNEL, node);
>   	if (!tbl)
> -		goto free_group;
> +		return NULL;
>   
>   	INIT_LIST_HEAD_RCU(&tbl->it_group_list);
>   	kref_init(&tbl->it_kref);
> +	return tbl;
> +}
>   
> -	table_group->tables[0] = tbl;
> +static struct iommu_table_group *iommu_pseries_alloc_group(int node)
> +{
> +	struct iommu_table_group *table_group;
> +
> +	table_group = kzalloc_node(sizeof(*table_group), GFP_KERNEL, node);
> +	if (!table_group)
> +		return NULL;
>   
> -	return table_group;
> +	table_group->tables[0] = iommu_pseries_alloc_table(node);
> +	if (table_group->tables[0])
> +		return table_group;


Nitpick: for readability, we'd usually expect the error path to be 
detected with the if statement and keep going on the good path, and here 
the code does the opposite. No big deal though, so

Reviewed-by: Frederic Barrat <fbarrat@...ux.ibm.com>


>   
> -free_group:
>   	kfree(table_group);
>   	return NULL;
>   }
>