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Date:   Thu, 7 Jul 2022 10:12:41 -0700
From:   Nicolin Chen <nicolinc@nvidia.com>
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Subject: Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void
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On Thu, Jul 07, 2022 at 08:42:28AM +0000, Tian, Kevin wrote:
> External email: Use caution opening links or attachments
> 
> 
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Wednesday, July 6, 2022 2:28 PM
> >
> > There's only one caller that checks its return value with a WARN_ON_ONCE,
> > while all other callers do not check return value at all. So simplify the
> > API to return void by embedding similar WARN_ON_ONCEs.
> 
> While this change keeps the similar effect as before it leads to different
> policy for same type of errors between pin and unpin paths:

I think it's because of the policy that an undo function should not
fail. Meanwhile, indulging faulty inputs isn't good either.

> e.g.
> 
> vfio_unpin_pages():
>         if (WARN_ON_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))
>                 return;
> 
> vfio_pin_pages():
>         if (!user_pfn || !phys_pfn || !npage ||
>             !vfio_assert_device_open(device))
>                 return -EINVAL;
> 
> It sounds a bit weird when reading related code...

Any better way to handle this?