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From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Wed, 14 Jul 2021 13:45:10 +0800
Message-ID: <CACycT3vNiAdOLVRhjqUjZGBfPnCti+_5+vdkgtbJ4XyRsYfrPg@mail.gmail.com>
Subject: Re: [PATCH v9 16/17] vduse: Introduce VDUSE - vDPA Device in Userspace
To:     Jason Wang <jasowang@redhat.com>
Cc:     Dan Carpenter <dan.carpenter@oracle.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Parav Pandit <parav@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Christian Brauner <christian.brauner@canonical.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, bcrl@kvack.org,
        Jonathan Corbet <corbet@lwn.net>,
        =?UTF-8?Q?Mika_Penttil=C3=A4?= <mika.penttila@nextfour.com>,
        joro@8bytes.org, Greg KH <gregkh@linuxfoundation.org>,
        He Zhe <zhe.he@windriver.com>,
        Liu Xiaodong <xiaodong.liu@intel.com>,
        songmuchun@bytedance.com,
        virtualization <virtualization@lists.linux-foundation.org>,
        netdev@vger.kernel.org, kvm <kvm@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Wed, Jul 14, 2021 at 10:54 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> =E5=9C=A8 2021/7/13 =E4=B8=8B=E5=8D=889:27, Dan Carpenter =E5=86=99=E9=81=
=93:
> > On Tue, Jul 13, 2021 at 04:46:55PM +0800, Xie Yongji wrote:
> >> +static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *nam=
e)
> >> +{
> >> +    struct vduse_vdpa *vdev;
> >> +    int ret;
> >> +
> >> +    if (dev->vdev)
> >> +            return -EEXIST;
> >> +
> >> +    vdev =3D vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> >> +                             &vduse_vdpa_config_ops, name, true);
> >> +    if (!vdev)
> >> +            return -ENOMEM;
> > This should be an IS_ERR() check instead of a NULL check.
>
>
> Yes.
>
>
> >
> > The vdpa_alloc_device() macro is doing something very complicated but
> > I'm not sure what.  It calls container_of() and that looks buggy until
> > you spot the BUILD_BUG_ON_ZERO() compile time assert which ensures that
> > the container_of() is a no-op.
> >
> > Only one of the callers checks for error pointers correctly so maybe
> > it's too complicated or maybe there should be better documentation.
>
>
> We need better documentation for this macro and fix all the buggy callers=
.
>
> Yong Ji, want to do that?
>

Sure, I will send the fix soon.

Thanks,
Yongji