Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table()

[Alexey Kardashevskiy]

On 05/14/2015 09:27 AM, Gavin Shan wrote:
> On Wed, May 13, 2015 at 02:51:36PM +0200, Thomas Huth wrote:
> > On Wed, 13 May 2015 16:30:16 +1000
> > Alexey Kardashevskiy <aik@xxxxxxxxx> wrote:
> >
> > > On 05/13/2015 03:33 PM, Gavin Shan wrote:
> > > > On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote:
> > > > > At the moment iommu_free_table() only releases memory if
> > > > > the table was initialized for the platform code use, i.e. it had
> > > > > it_map initialized (which purpose is to track DMA memory space use).
> > > > >
> > > > > With dynamic DMA windows, we will need to be able to release
> > > > > iommu_table even if it was used for VFIO in which case it_map is NULL
> > > > > so does the patch.
> > > > >
> > > > > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > > >
> > > > Reviewed-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
> > > >
> > > > > ---
> > > > > arch/powerpc/kernel/iommu.c | 3 +--
> > > > > 1 file changed, 1 insertion(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> > > > > index 3d47eb3..2c02d4c 100644
> > > > > --- a/arch/powerpc/kernel/iommu.c
> > > > > +++ b/arch/powerpc/kernel/iommu.c
> > > > > @@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
> > > > > 	unsigned int order;
> > > > >
> > > > > 	if (!tbl || !tbl->it_map) {
> > > > > -		printk(KERN_ERR "%s: expected TCE map for %s\n", __func__,
> > > > > -				node_name);
> > > > > +		kfree(tbl);
> > > >
> > > > I'm not sure if the "tbl" needs to be checked against NULL as kfree() already
> > > > has the check. But it looks a bit strange to free NULL "tbl" from the code
> > > > itself.
> > >
> > > Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/...
> > > - they all check the passed pointer for NULL.
> >
> > But if tbl is NULL, the tbl->it_map check will fail, won't it? So in
> > this case, I think you have to keep it.
>
> If I understood your question correctly, "tbl->it_map" won't be checked
> when "tbl" is NULL because the connection ("||") for the two conditions.
> The code can be changed to something like below if Alexey want:
>
> 	if (!tbl)
> 		return;
> 	if (!tbl->itmap)
> 		kfree(tbl);

To be precise ;)

if (!tbl->itmap) {
	kfree(tbl);
	return;
}

> Thanks,
> Gavin


--
Alexey
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/