Hi, On Tue, Apr 14, 2015 at 10:12:18AM -0700, Noel Burton-Krahn wrote: > I'm tracking a kernel panic after umounting an nbd device. Have you see > this before? I didn't see this before. > > > Description > ----------- > > Mount an nbd device, start a process reading a file in it, umount, call > qemu-nbd -d, kill the process, kernel panic. > > This can also happen after the reading process exits, maybe when a > buffer gets flushed? We see it when a [jbd2/nbdXXX] process remains > running after a umount and the [nbdXXX] process has quit with no other > processes using the nbd device. > > > Tested Versions > --------------- > 3.13, 3.18 > > > Steps to Reproduce > ------------------ > > qemu-img create f.img 1G > yes | mkfs.ext4 f.img > modprobe nbd > qemu-nbd -c /dev/nbd1 f.img > sleep 1 > mkdir -p /mnt/1 > mount /dev/nbd1 /mnt/1 > date > /mnt/1/date > ip netns add ns > ip netns exec ns tail -f /mnt/1/date >/dev/null 2>&1 & # NOTE1 > #mount -o remount,ro /mnt/1 # NOTE2 > umount /mnt/1 > qemu-nbd -d /dev/nbd1 > sleep 1 > kill %- > > NOTE1: umount will fail with device busy is the proc is not in a netns > NOTE2: remounting readonly avoids the bug Thanks. I will try to reproduce this bug. Best Regards, Markus -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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