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Date:   Tue, 20 Oct 2020 08:47:10 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
CC:     Maor Gottlieb <maorg@nvidia.com>, Christoph Hellwig <hch@lst.de>,
        "Gal Pressman" <galpress@amazon.com>,
        Bob Pearson <rpearsonhpe@gmail.com>,
        "Leon Romanovsky" <leonro@nvidia.com>, <linux-rdma@vger.kernel.org>
Subject: Re: dynamic-sg patch has broken rdma_rxe
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On Tue, Oct 20, 2020 at 12:37:05PM +0100, Tvrtko Ursulin wrote:

> > Why put this confusing code in every caller? Especially for something
> > a driver is supposed to call. Will just make bugs
> 
> For max_segment to be aligned is a requirement today so callers are
> ready.

No, it turns out all the RDMA drivers were became broken when they
converted to use the proper U32_MAX for their DMA max_segment size,
then they couldn't form SGLs anymore.

I don't want to see nonsense code like this:

        dma_set_max_seg_size(dev->dev, min_t(unsigned int, U32_MAX & PAGE_MASK,
                                             SCATTERLIST_MAX_SEGMENT));

In drivers.

dma_set_max_seg_size is the *hardware* capability, and mixing in
things like PAG_MASK here is just nonsense.

Jason