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

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Date:   Mon, 19 Jul 2021 15:47:27 -0300
From:   Leonardo Brás <leobras.c@...il.com>
To:     Frederic Barrat <fbarrat@...ux.ibm.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 Mon, 2021-07-19 at 16:04 +0200, Frederic Barrat wrote:
> 
> 
> 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>
> 
> 

Thanks for the tip and review!

Best regards,
Leonardo Bras


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