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    SubjectRe: Driver retries disk errors.
    On Tue, Aug 31, 2004 at 05:12:50PM +0100, Alan Cox wrote:
    > > (1) Imagine an application doing a linear read on a file with an 8
    > > block read ahead and the last block being bad. The kernel will try to
    > > read that bad block 16 times, but because the IDE driver also has 8
    > > retries, the kernel will try to read that bad block *64* times. It
    > > usually takes an IDE drive about 2 seconds to figure out a block is
    > > bad, so the application gets stuck for 2 minutes in that single bad
    > > block.
    > Right now I know of no way to tell which is readahead for a failed
    > command or of telling the block layer to forget them. Fix this at the
    > block layer and IDE can abort the readahead sequence happily enough
    > because IDE is too dumb to have issued further commands to the drive at
    > this point.

    Just a question from a kernel-almost-illiterate. Could this explain the
    behavior of my laptop yesterday, reading a damaged DVD? I had to wait almost
    one full minute of retry until being able to kill xine...

    If maintaining the retries, it could be nice to allow at least kill -9
    between them. I do not know if that's foolish and/or impossible, so please
    do not bash too hard...

    Have a nice day,

    Romano Giannetti - Univ. Pontificia Comillas (Madrid, Spain)
    Electronic Engineer - phone +34 915 422 800 ext 2416 fax +34 915 596 569
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