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[Launchpad Bug Tracker <1381968@xxxxxxxxxxxxxxxxxx>]

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I've upgraded Ubuntu Server 12.04 LTS to 14.04 LTS.

The setup contains a loopback device (/dev/loop3) mounted into a
software raid 1 (/dev/md2).

After the weekly cronjob (/etc/cron.weekly/fstrim) ran, I've discovered
that it wiped all data on the loopback device from the raid.

fstrim-all skips check because the loopback device is part of device mapper raid.
if [ "${REALDEV#/dev/dm-}" != "$REALDEV" ]; then
        echo "device $DEV is on devmapper, skipping TRIM feature check"

Issue can be reproduced on raid setup and plain loopback mount setup!

Here is step-by-step how to reproduce the issue:

1.) create sparse image file
dd of=/sparse-file bs=1k seek=1024000

2.) losetup loopback device
losetup /dev/loop3 /sparse-file

3.) create raid1
mdadm --create /dev/md2 --auto md --level=1 --raid-devices=1 /dev/loop3

4.) create fs
mkfs.ext4 /dev/md2

4.1.) check sparse-file size
ls -lash /sparse-file

5.) mount and copy data
mount /dev/md2 /mnt
copy some random files on /mnt

5.1.) check sparse-file size again
ls -lash /sparse-file -> size indicates it contains the copied data

6.) destroy loopback via fstrim
fstrim -v /mnt

7.) data is wiped
umount /mnt
ls -lash /sparse-file -> size indicates that all data is wiped out!
fsck -v -f /dev/md2 -> will report infinite errors on filesystem

I could not find any similiar bugreport.

Best Regards
Daniel

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: dataloss fstrim kernel-bug loopback
-- 
Fstrim destroys data on loopback device
https://bugs.launchpad.net/bugs/1381968
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