Re: [PATCH v2 1/2] iova: Remove some magazine pointer NULL checks

[Ethan Zhao]

John,

在 2022/9/6 18:50, John Garry 写道:
> On 06/09/2022 10:28, Ethan Zhao wrote:
>
> Hi Ethan,
>
> > > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> > > Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
> > > ---
> > >   drivers/iommu/iova.c | 7 ++-----
> > >   1 file changed, 2 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> > > index 47d1983dfa2a..580fdf669922 100644
> > > --- a/drivers/iommu/iova.c
> > > +++ b/drivers/iommu/iova.c
> > > @@ -661,9 +661,6 @@ iova_magazine_free_pfns(struct iova_magazine 
> > > *mag, struct iova_domain *iovad)
> > >       unsigned long flags;
> > >       int i;
> > > -    if (!mag)
> > > -        return;
> > > -
> >
> > iommu_probe_device
> >    ops->probe_finalize(dev);
> >      intel_iommu_probe_finalize
> >         iommu_setup_dma_ops
> >           iommu_dma_init_domain(domain, dma_base, dma_limit, dev)
> >             iova_domain_init_rcaches
> >               {
> >               ...
> >               cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
> >               cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
> >             if (!cpu_rcache->loaded || !cpu_rcache->prev) {
> >                  ret = -ENOMEM;
> >                        goto out_err;
> >
> > Do you mean iova_magazine_alloc() is impossible to fail ?
>
> No, iova_magazine_alloc() may fail and return NULL. But if it does 
> then we set iovad rcache pointer = NULL in the error path and don't 
> use the rcache.

Yup,  if iova_magazine_alloc() failed ,

iovad->rcaches = NULL;

was set by free_iova_rcaches()

in error path of iova_domain_init_rcache().

and checked in

alloc_iova_fast()->iova_rcache_get().

More comment in code would wipe off my curiosity.


Thanks,

Ethan

> However we have a !iovad->rcache check on the "fast" alloc but not 
> "insert". I need to check why that is again.
>
> Thanks,
> john

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