SCSI check sense bit not getting back to st driver

[Kevin Fenzi <kevin-linux-kernel@scrye.com>]

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[ reposted under this subject instead of the old one about end of tape
handling]

I (and several others at least) have been seeing a problem with end of
tape error handling under linux. Instead of getting a ENOSPC, you get
a EIO error when you hit the end of the tape. This makes multivolume
backups kinda difficult.

Some more information on this problem was discovered by Tim Jones
<tjones@tolisgroup.com>:

Tim> Additional news.

Tim> This is actually related to the check sense bit not being
Tim> propagated up to the ST driver.  A simpler test (beats writing
Tim> 40GB to a tape ...):

Tim> use a 2.2.19/20/21 or 22 kernel, or a 2.4.9-34 kernel Remove the
Tim> tape from the tape device execute:

Tim>   tar -cvvf /dev/nst0 /etc

Tim> You will receive a "No medium found" message

Tim> Replace the kernel with 2.4.11+ and repeat the tar write test.
Tim> This time, you will receive a write failure.

Tim> This is caused by the check sense not being set and the ST driver
Tim> sending up a EIO instead of the ENOMEDIUM.

So, it looks like this problem is _not_ in the st driver itself, but
somewhere in the SCSI layer. 

Anyone have any ideas how to better track it down?

Happy to run debug code/test cases here. 

kevin
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