I can confirm that the error messages on Ubuntu 16.04 (daily) still exist but it seems that it is not as bad as it looks.
I followed the steps which Marcin described in comment #16. Instead of > Write some data on backing file via loop device > dd if=/dev/zero of=/mnt/Test.file bs=1M count=512 I copied a known iso file to the created loop device dd if=lubuntu-14.04.4-desktop-amd64.iso of=/mnt/Test.file bs=1M I got also some error messages as described in previous comments but md5sum said md5sum lubuntu-14.04.4-desktop-amd64.iso && md5sum /mnt/Test.file 0b0fc8652afe0761edc3ed33e1b199f0 lubuntu-14.04.4-desktop-amd64.iso 0b0fc8652afe0761edc3ed33e1b199f0 /mnt/Test.file Then I unmounted the test image and checked it for errors. umount /mnt/ fsck -pvcf ./Test.img ...and I got: fsck from util-linux 2.27.1 ./Test.img: Updating bad block inode. 12 inodes used (0.02%, out of 65536) 0 non-contiguous files (0.0%) 0 non-contiguous directories (0.0%) # of inodes with ind/dind/tind blocks: 0/0/0 Extent depth histogram: 3/1 201308 blocks used (76.79%, out of 262144) 0 bad blocks 1 large file 1 regular file 2 directories 0 character device files 0 block device files 0 fifos 0 links 0 symbolic links (0 fast symbolic links) 0 sockets ------------ 3 files -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1526537 Title: blk_update_request: I/O error To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1526537/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs