Re: [PATCH v10 1/6] RDMA/umem: Support importing dma-buf as user memory region

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Nov 10, 2020 at 01:41:12PM -0800, Jianxin Xiong wrote:
> +struct ib_umem *ib_umem_dmabuf_get(struct ib_device *device,
> +				   unsigned long offset, size_t size,
> +				   int fd, int access,
> +				   const struct dma_buf_attach_ops *ops)
> +{
> +	struct dma_buf *dmabuf;
> +	struct ib_umem_dmabuf *umem_dmabuf;
> +	struct ib_umem *umem;
> +	unsigned long end;
> +	long ret;
> +
> +	if (check_add_overflow(offset, (unsigned long)size, &end))
> +		return ERR_PTR(-EINVAL);
> +
> +	if (unlikely(PAGE_ALIGN(end) < PAGE_SIZE))
> +		return ERR_PTR(-EINVAL);

This is weird, what does it do?

> +
> +	if (unlikely(!ops || !ops->move_notify))
> +		return ERR_PTR(-EINVAL);
> +
> +	umem_dmabuf = kzalloc(sizeof(*umem_dmabuf), GFP_KERNEL);
> +	if (!umem_dmabuf)
> +		return ERR_PTR(-ENOMEM);
> +
> +	umem = &umem_dmabuf->umem;
> +	umem->ibdev = device;
> +	umem->length = size;
> +	umem->address = offset;
> +	umem->writable = ib_access_writable(access);
> +	umem->is_dmabuf = 1;
> +
> +	if (unlikely(!ib_umem_num_pages(umem))) {
> +		ret = -EINVAL;
> +		goto out_free_umem;
> +	}
> +
> +	dmabuf = dma_buf_get(fd);
> +	if (IS_ERR(dmabuf)) {
> +		ret = PTR_ERR(dmabuf);
> +		goto out_free_umem;
> +	}
> +
> +	if (dmabuf->size < offset + size) {
> +		ret = -EINVAL;
> +		goto out_release_dmabuf;

offset + size == end, already computed, in fact move this above the
kzalloc

Jason