linux-kernel - Re: [PATCH v8 23/24] nvme-pci: convert to blk_rq_dma

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Message-ID: <20250422050050.GB28077@lst.de>
Date: Tue, 22 Apr 2025 07:00:50 +0200
From: Christoph Hellwig <hch@....de>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
	Keith Busch <kbusch@...nel.org>, Jake Edge <jake@....net>,
	Jonathan Corbet <corbet@....net>, Jason Gunthorpe <jgg@...pe.ca>,
	Zhu Yanjun <zyjzyj2000@...il.com>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Sagi Grimberg <sagi@...mberg.me>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Jérôme Glisse <jglisse@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, linux-rdma@...r.kernel.org,
	iommu@...ts.linux.dev, linux-nvme@...ts.infradead.org,
	linux-pci@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
	Niklas Schnelle <schnelle@...ux.ibm.com>,
	Chuck Lever <chuck.lever@...cle.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Kanchan Joshi <joshi.k@...sung.com>,
	Chaitanya Kulkarni <kch@...dia.com>,
	Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH v8 23/24] nvme-pci: convert to blk_rq_dma_map

> +	dma_len = min_t(u32, length, NVME_CTRL_PAGE_SIZE - (dma_addr & (NVME_CTRL_PAGE_SIZE - 1)));

And overly long line slipped in here during one of the rebases.

> +		/*
> +		 * We are in this mode as IOVA path wasn't taken and DMA length
> +		 * is morethan two sectors. In such case, mapping was perfoormed
> +		 * per-NVME_CTRL_PAGE_SIZE, so unmap accordingly.
> +		 */

Where does this comment come from?  Lots of spelling errors, and I
also don't understand what it is talking about as setors are entirely
irrelevant here.

> +	if (!blk_rq_dma_unmap(req, dev->dev, &iod->dma_state, iod->total_len)) {
> +		if (iod->cmd.common.flags & NVME_CMD_SGL_METABUF)
> +			nvme_free_sgls(dev, req);

With the addition of metadata SGL support this also needs to check
NVME_CMD_SGL_METASEG.

The commit message should also really mentioned that someone
significantly altered the patch for merging with latest upstream,
as I as the nominal author can't recognize some of that code.

> +	unsigned int entries = req->nr_integrity_segments;
>  	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
>  
> +	if (!blk_rq_dma_unmap(req, dev->dev, &iod->dma_meta_state,
> +			      iod->total_meta_len)) {
> +		if (entries == 1) {
> +			dma_unmap_page(dev->dev, iod->meta_dma,
> +				       rq_integrity_vec(req).bv_len,
> +				       rq_dma_dir(req));
> +			return;
>  		}
>  	}
>  
> +	dma_pool_free(dev->prp_small_pool, iod->meta_list, iod->meta_dma);

This now doesn't unmap for entries > 1 in the non-IOVA case.