Loop device corruption

Jim Nance (jnance@nortelnetworks.com)
Tue, 10 Aug 1999 07:52:28 -0400


Hello All,
I found what I think may be a bug in the loop device driver in 2.3.12
last night. I was trying to back up some data to CD, and I did this:

insmod loop.o
dd bs=1M count=620 </dev/zero >/mnt/tmp/loop
/sbin/mke2fs -b 2048 /mnt/tmp/loop
mount -t ext2 -o loop=/dev/loop1 /mnt/tmp/loop /mnt/backup
(cd some/directory; tar cf - .) | (cd /mnt/backup; tar xvf -)
umount /mnt/backup
rmmod loop

At this point I should have an ext2 filesystem in the file /mnt/tmp/loop.
Just for grins I decided to run e2fsck on the file, and it found errors.
At this point I blew away the loop file and repeated the steps above.
I still had errors when I ran e2fsck.

If I use a hd partition instead of a looped back file, I get no errors,
which is what makes me suspect the loopback device driver.

FWIW: 2.3.12 kernel, IDE hard drives with ide-scsi emulation for CD burner,
128M ram, 400 MHz K6-III.

Jim

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