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Date:   Tue, 13 Jul 2021 16:27:41 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Xie Yongji <xieyongji@bytedance.com>,
        Jason Wang <jasowang@redhat.com>
Cc:     mst@redhat.com, stefanha@redhat.com, sgarzare@redhat.com,
        parav@nvidia.com, hch@infradead.org,
        christian.brauner@canonical.com, rdunlap@infradead.org,
        willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk,
        bcrl@kvack.org, corbet@lwn.net, mika.penttila@nextfour.com,
        joro@8bytes.org, gregkh@linuxfoundation.org, zhe.he@windriver.com,
        xiaodong.liu@intel.com, songmuchun@bytedance.com,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 16/17] vduse: Introduce VDUSE - vDPA Device in
 Userspace
Message-ID: <20210713132741.GM1954@kadam>
References: <20210713084656.232-1-xieyongji@bytedance.com>
 <20210713084656.232-17-xieyongji@bytedance.com>
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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 *name)
> +{
> +	struct vduse_vdpa *vdev;
> +	int ret;
> +
> +	if (dev->vdev)
> +		return -EEXIST;
> +
> +	vdev = 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.

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.

regards,
dan carpenter