[Bug 264789] Re: USB Hard Drive Not Accessible, vol_id hangs

Tim Wright timw at splhi.com
Mon Dec 29 17:15:06 UTC 2008

Please do NOT do this. That is not the correct fix. The bug is with the USB/SCSI retry logic (which changed between 2.6.26 and 2.6.27 and causes an infinite retry loop in this case).
I tried the adding ENV{DEVTYPE}=partition workaround a while ago and rendered my system unbootable and I got to spend a merry time with the live CD undoing the change. If you use dmraid (fakeraid) support, then the vol_id line NEEDS to occur for the whole disk, not for a partition only. If your udev changes don't break dm/fakeraid, then that's much better, but it's still papering over the real underlying problem.

The kernel retry code needs to be fixed, and to avoid getting any I/O
error at all from vol_id, all the broken devices which return
(last_sector + 1) from the call to find the capacity, instead of
last_sector need to have an UNUSUAL_DEV entry with US_FL_FIX_CAPACITY in
the flags. Sadly, this seems to be a very large number of devices.

The kernel fix that Alan Stern provided should prevent the infinite
retry logic and so you should see a handful of failures and then
everything should carry on. I haven't yet downloaded the Ubuntu -11
kernel source to see why this isn't happening.

USB Hard Drive Not Accessible, vol_id hangs
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