Re: Driver retries disk errors.

[Romano Giannetti <romano@dea.icai.upco.es>]

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 


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