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    SubjectRe: [patch] cache flush bug in mm/filemap.c (all kernels >= 2.5.30(at least))
    On Fri, May 23, 2003 at 11:29:26AM -0700, Andrew Morton wrote:
    > Vague statement of principle: The device driver layer takes care of these
    > issues for DMA transfers, and hence should also take care of them for PIO.
    > Is this sensible and/or possible?

    I'd err on the side of caution about extending this principle. The
    device driver layer's issue for DMA transfers seems to cover the device <->
    kernel cache consistency, not the device <-> user space or kernel <->
    user space cache consistency.

    The kernel <-> user space consistency issue seems to be one for the MM
    layer to deal with. There are other situations where this view can go
    out of sync - for instance, when you have a page of a file mmap'd, and
    you use sys_write() to that page of file. This is the issue which
    flush_dcache_page() seems to be addressing, and it's the same issue
    with PIO from IDE.

    So no, I don't think it is a device driver issue at all.


    Russell King ( The developer of ARM Linux

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