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    SubjectRe: [PATCH 5/6] firewire: SBP-2 highlevel driver
    I wrote:
    > Christoph Hellwig wrote:
    >>> + /* Convert the scatterlist to an sbp2 page table. If any
    >>> + * scatterlist entries are too big for sbp2 we split the as we go. */
    >> Please set the max_sectors value in your host template so that the
    >> block layer doesn't build sg entries too big for you.
    >
    > Hmm, what about this:
    >
    > James Bottomley wrote on 2007-01-15:
    > | Actually, there's one unfortunate case where Linux won't respect this:
    > | an IOMMU that can do virtual merging. This parameter is a block queue
    > | parameter, so block will happily make sure the request segments obey it.
    > | However, when you get to dma_map_rq() it doesn't see the segment limits,
    > | so, if the iommu merges, you can end up with SG elements the other side
    > | that violate this. I've been meaning to do something about this for
    > | ages (IDE is the other subsystem that has an absolute requirement for a
    > | fixed maximum segment size) but never found an excuse to fix it.
    >
    > http://marc.info/?l=linux-scsi&m=116889641203397

    PS:
    Nonetheless, yes, fw-sbp2.c is curiously missing to set the template's
    max_sectors.
    --
    Stefan Richter
    -=====-=-=== -=-= ---==
    http://arcgraph.de/sr/
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