Comment 16 for bug 1526537

Joseph, I encounter this problem also in ubuntu 15.04 with a linux-image-3.19.0-15-generic.

I can append some additional information how to reproduce this issue. After my analysis I found dependence: drive filesystem vs backing file filesystem:

Create backing file on a drive that is formatted to NTFS
dd if=/dev/zero of=./Test.img bs=1M count=1024

Find free loop device
losetup -f

Connect backing file with a loop device [ losetup -f ], for example: /dev/loop3
losetup /dev/loop3 ./Test.img

Create filesystem on backing file via loop device
mkfs.ext4 /dev/loop3

Mount backing file via loop device into /mnt directory
mount -t ext4 /dev/loop3 /mnt/

Write some data on backing file via loop device
dd if=/dev/zero of=/mnt/Test.file bs=1M count=512

After this procedure you will be see errors on a kernel log:
[ 1370.381087] blk_update_request: I/O error, dev loop3, sector 25864
[ 1370.789277] blk_update_request: I/O error, dev loop3, sector 29960
[ 1371.193360] blk_update_request: I/O error, dev loop3, sector 34056