I could reproduce the issue by adding a single "sync". It seems the umount in original script flushes data to loopdevice. When the caches are already flushed you will be able to reproduce the dataloss!
Btw..fsck seems unable to detect the broken filesystem!? PS: I changed from mdadm to normal mounting the loopback device ** Attachment added: "modified script" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1381968/+attachment/4238892/+files/repro -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1381968 Title: Fstrim destroys data on loopback device Status in “linux” package in Ubuntu: Confirmed Bug description: 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1381968/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
