Re: Linux, ISOFS, multi-extent files: what's the status?

[Bill Davidsen]

Volker Kuhlmann wrote:
On Sun 10 Jan 2010 10:15:10 NZDT +1300, Bill Davidsen wrote:

  
There was another error having to do with reading data at the end of an 
image. Due to read ahead settings a read past end of data occurred and the 
(valid) partial data was not returned to the user program. Might that be 
what you are remembering?
    

Thanks for mentioning it. Since the mid-90s the kernel produces I/O
errors reading the last blocks of an ISO image from actual disk because
of a read-ahead function. Turning off read-ahead is not sufficient to
prevent this error, turning off DMA is also necessary (presumably that
has its own read-ahead too). This problem because suddenly worse again a
few years ago when DVDs arrived (larger block size, larger read-ahead). 
I can't say whether it's ever been fixed completely, I always use a
workaround for my own disks, but haven't seen it much on other disks any
more.
  

I have just turned down readahead in blockdev and my issues have gone 
away, but like you I don't see it much if a while.


--
Bill Davidsen <david...@tmr.com>
 "We can't solve today's problems by using the same thinking we
  used in creating them." - Einstein


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