Re: [RFC PATCH 1/3] RDMA/umem: Support importing dma-buf as user memory region

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Apr 16, 2020 at 07:41:33PM +0000, Xiong, Jianxin wrote:
> > > +void ib_umem_dmabuf_release(struct ib_umem_dmabuf *umem_dmabuf) {
> > > +	enum dma_data_direction dir;
> > > +
> > > +	dir = umem_dmabuf->umem.writable ? DMA_BIDIRECTIONAL :
> > > +DMA_FROM_DEVICE;
> > > +
> > > +	/*
> > > +	 * Only use the original sgt returned from dma_buf_map_attachment(),
> > > +	 * otherwise the scatterlist may be freed twice due to the map caching
> > > +	 * mechanism.
> > > +	 */
> > > +	dma_buf_unmap_attachment(umem_dmabuf->attach, umem_dmabuf->sgt, dir);
> > > +	dma_buf_detach(umem_dmabuf->dmabuf, umem_dmabuf->attach);
> > > +	dma_buf_put(umem_dmabuf->dmabuf);
> > > +	mmdrop(umem_dmabuf->umem.owning_mm);
> > > +	kfree(umem_dmabuf);
> > > +}
> > > +EXPORT_SYMBOL(ib_umem_dmabuf_release);
> > 
> > Why is this an EXPORT_SYMBOL?
> 
> It is called from ib_umem_release() which is in a different file.

export is only required to call outside the current module, which is
is not.

> > > diff --git a/include/rdma/ib_umem_dmabuf.h
> > > b/include/rdma/ib_umem_dmabuf.h new file mode 100644 index
> > > 0000000..e82b205
> > > +++ b/include/rdma/ib_umem_dmabuf.h
> > 
> > This should not be a public header
> 
> It's put there to be consistent with similar headers such as "ib_umem_odp.h". Can be changed.

ib_umem_odp is needed by drivers, this is not.

Jason