Date: Mon, 10 Apr 1995 00:50:01 -0700 From: edward@edcom.com To: freebsd-bugs Subject: kern/331: SCSI tape short-read failure Message-ID: <199504100750.AAA00666@freefall.cdrom.com> In-Reply-To: Your message of Mon, 10 Apr 1995 00:45:50 -0700 <199504100745.AAA01711@edcom.com>
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>Number: 331
>Category: kern
>Synopsis: a read that returns short on a SCSI tape fails
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs (FreeBSD bugs mailing list)
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Apr 10 00:50:00 1995
>Originator: Edward Wang
>Organization:
feh!
>Release: FreeBSD 2.1.0-Development i386
>Environment:
2.0-950322-SNAP
>Description:
On a SCSI tape (and really other devices with similar
characteristics), a read of a record smaller than
the request size always fails.
>How-To-Repeat:
find a SCSI tape drive
put a tape in
do
dd if=/dev/zero of=/dev/rst0 bs=1b count=1
dd if=/dev/rst0 of=/dev/null bs=1k count=1
the read fails when it should return 512 bytes
>Fix:
*** scsi_base.c.dist Tue Mar 21 03:21:01 1995
--- scsi_base.c Sun Apr 9 22:56:52 1995
***************
*** 593,604 ****
xs->flags &= ~ITSDONE;
goto retry;
}
}
- retval = EIO; /* Too many retries */
if (bp) {
bp->b_error = 0;
- bp->b_resid = 0;
if (retval) {
bp->b_flags |= B_ERROR;
bp->b_error = retval;
--- 593,603 ----
xs->flags &= ~ITSDONE;
goto retry;
}
+ retval = EIO; /* Too many retries */
}
if (bp) {
bp->b_error = 0;
if (retval) {
bp->b_flags |= B_ERROR;
bp->b_error = retval;
The first change (position of retval = EIO) is the bug.
The second change is to return the correct b_resid.
The second problem seems to be in the 1.1.5.1 code as well.
It's less used so possibly nobody noticed. I can't be sure
it doesn't affect something else -- something that doesn't
set b_resid correctly and relies on this to clear it.
However, I'm running this on a machine with SCSI disks and tapes.
They seem to work.
>Audit-Trail:
>Unformatted:
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