kernel 2.4 status page - loopback mount option still has problems even in 2.4.0-test7-final.

From: William Stearns (
Date: Sun Aug 27 2000 - 12:52:50 EST

Good day, Ted and all,
        The loopback mount option is still not 100% there for me in
2.4.0-test7; there appears to be some kind of deadlock still there (thenks
arjan and cesarb!). Here's the line from your 2.4 status page:

- Loop device hangs (Peter Enderborg can duplicate by writing large file
to dosfs mounted via loop device; Steve Dodd reports deadlock issues;
Linus says fixed in test6)

        I do quite a bit of work with creating a 50-200M file, making an
ext2 filesystem on it, then loading it with rpms for User Mode Linux. On
a 256M machine with other apps running, I find I can do this 3 to 5 times
before the machine hangs (no oops, some apps still run, nothing from
dmesg, apps stuck in the "D" state according to ps, unable to shutdown or
halt, unable to unmount the loopback'ed filesystem).

        I should briefly add that my two most recent kernels have been
2.4.0-test7-pre4 with Rik's vm patch and 2.4.0-test7-final with Ingo's low
latency patch, but this problem has existed for a long time; I'd say at
least as long as the 2.4.0-test series. I'll try to come up with a
pristine 2.4.0-test7 as another test, but I'm not terribly optimistic.
        The problem shows up whether X is running or not.

        Here's a simplified version of the script I use. This one can
reliably hang the system up to and including 2.4.0-test7. If it doesn't
hang the system on first pass, keep running it a few times. Make sure
you've saved your work first. :-)

---- [snip] ----

if [ ! -d mnt ]; then mkdir mnt ; fi

dd if=/dev/zero of=testroot bs=$((1024 * 1024)) count=130 || exit 1
sudo mke2fs -F testroot || exit 1

sudo umount mnt || true
sudo mount -o loop testroot mnt || exit 1

cd mnt
cp -pR /usr/src/linux .
cd ..
sudo umount mnt || exit 1
---- [snip] ----

        I would sincerely like to hear if this is repeatable on anyone
else's system. Please: 1) save your work first, and 2) let me know
off-list if you can reproduce the problem or not. I'll summarize to the
list in a few days.
        - Bill

        "After being a technician for 2 years, I've discovered if people
took care of their health with the same reckless abandon as their
computers, half would be at the kitchen table on the phone with the
hospital, trying to remove their appendix with a butter knife."
(Courtesy of Brian Jones <>)
William Stearns ( Mason, Buildkernel, named2hosts,
and ipfwadm2ipchains are at:
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