linux-kernel - Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL

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Message-ID: <4e336c7e-207b-31fa-806e-c4e8028524a5@deltatee.com>
Date:   Mon, 9 Nov 2020 09:47:11 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Stephen Bates <sbates@...thlin.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA
 segments in an SGL



On 2020-11-09 2:12 a.m., Christoph Hellwig wrote:
> On Fri, Nov 06, 2020 at 10:00:25AM -0700, Logan Gunthorpe wrote:
>> We make use of the top bit of the dma_length to indicate a P2PDMA
>> segment.
> 
> I don't think "we" can.  There is nothing limiting the size of a SGL
> segment.

Yes, I expected this would be the unacceptable part. Any alternative ideas?

Logan