On Fri, Nov 13, 2020 at 03:30:04AM +0000, Xiong, Jianxin wrote:
> > From: Jason Gunthorpe <jgg@xxxxxxxx>
> > Sent: Thursday, November 12, 2020 4:31 PM
> > To: Xiong, Jianxin <jianxin.xiong@xxxxxxxxx>
> > Cc: linux-rdma@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Doug Ledford <dledford@xxxxxxxxxx>; Leon Romanovsky
> > <leon@xxxxxxxxxx>; Sumit Semwal <sumit.semwal@xxxxxxxxxx>; Christian Koenig <christian.koenig@xxxxxxx>; Vetter, Daniel
> > <daniel.vetter@xxxxxxxxx>
> > Subject: Re: [PATCH v10 1/6] RDMA/umem: Support importing dma-buf as user memory region
> >
> > 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?
>
> This sequence is modeled after the following code from ib_umem_init_odp():
>
> if (check_add_overflow(umem_odp->umem.address,
> (unsigned long)umem_odp->umem.length,
> &end))
> return -EOVERFLOW;
> end = ALIGN(end, page_size);
> if (unlikely(end < page_size))
> return -EOVERFLOW;
>
> The weird part seems to be checking if 'end' is 0, but that should have been covered
> by check_add_overflow() already.
I think the
+ if (unlikely(!ib_umem_num_pages(umem))) {
Catches the same condition, no need to do it twice
Jason
