[PATCH] NVMe: Add rw_page support

[Keith Busch]

On Fri, 14 Nov 2014, Andrey Kuzmin wrote:
> On Nov 14, 2014 3:13 AM, "Keith Busch" <keith.busch at intel.com> wrote:
> > +static void pgwr_completion(struct nvme_queue *nvmeq, void *ctx,
> > +                                               struct nvme_completion *cqe)
> > +{
> > +       struct request *req = ctx;
> > +       struct nvme_cmd_info *cmd_rq = blk_mq_rq_to_pdu(req);
> > +       struct page *page = req->special;
> > +       u16 status = le16_to_cpup(&cqe->status) >> 1;
> > +
> > +       dma_unmap_page(nvmeq->q_dmadev, cmd_rq->dma, PAGE_CACHE_SIZE, DMA_TO_DEVICE);
> > +       page_endio(page, WRITE, status != NVME_SC_SUCCESS);
> > +       blk_put_request(req);
> > +}
> > +
> 
> As you have access to the nvme_cmd_info - and thus command opcode - in the
> completion handler, having separate completion handlers for read and write
> operations looks like unnecessary code duplication. Just my .02 :).

But nvme_cmd_info does not contain the opcode. I do have the struct
request here, and I can certainly pull the data direction from its
cmd_flags, so thanks for the suggestion!

Now I wonder if there's something else unused in a request that I
can repurpose to save the dma_addr_t in so I don't add it in the
nvme_cmd_info...

> Best regards,
> Andrey