Bug#840184: df and du shows different size

[Андрей Василишин <a.vasilishin@kpi.ua>]

Package: linux-image-3.16.0-4-amd64
Version: 3.16.36-1+deb8u1

Hello!
Usually df -h  and du -hs shows the same used space. But now I have a 
problem. I am using two SSD for a cache. Script using df command, all 
time writes and deletes files. There are no such problem with wheezy 
kernels.

df -h
/dev/sdc1          237G         178G   47G           80% /megastorage1
/dev/sdb1          237G         177G   48G           79% /megastorage2

du -hs /megastorage1
24G     /megastorage1

du -hs /megastorage2
23G     /megastorage2


 mount | grep megastorage
/dev/sdc1 on /megastorage1 type ext4 (rw,noatime,data=ordered)
/dev/sdb1 on /megastorage2 type ext4 (rw,noatime,data=ordered)