On Mon, Feb 01, 2021 at 10:30:17AM -0800, Jianxiong Gao wrote:
> @@ -868,12 +871,24 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev,
> struct request *req,
> if (!iod->nents)
> goto out_free_sg;
>
> + offset_ret = dma_set_min_align_mask(dev->dev, NVME_CTRL_PAGE_SIZE - 1);
> + if (offset_ret) {
> + dev_warn(dev->dev, "dma_set_min_align_mask failed to set
> offset\n");
> + goto out_free_sg;
> + }
> +
> if (is_pci_p2pdma_page(sg_page(iod->sg)))
> nr_mapped = pci_p2pdma_map_sg_attrs(dev->dev, iod->sg,
> iod->nents, rq_dma_dir(req), DMA_ATTR_NO_WARN);
> else
> nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents,
> rq_dma_dir(req), DMA_ATTR_NO_WARN);
> +
> + offset_ret = dma_set_min_align_mask(dev->dev, 0);
> + if (offset_ret) {
> + dev_warn(dev->dev, "dma_set_min_align_mask failed to reset
> offset\n");
> + goto out_free_sg;
> + }
> if (!nr_mapped)
> goto out_free_sg;
Why is this setting being done and undone on each IO? Wouldn't it be
more efficient to set it once during device initialization?
And more importantly, this isn't thread safe: one CPU may be setting the
device's dma alignment mask to 0 while another CPU is expecting it to be
NVME_CTRL_PAGE_SIZE - 1.
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