Comment # 5 on bug 1068707 from Ruediger Oertel

hm, different error message but still does not work:

s390p21:~ # echo /dev/zram0 > /sys/fs/bcache/register
-bash: echo: write error: Invalid argument

[4830275.525506] zram: Added device: zram0
[4830291.485844] zram0: detected capacity change from 0 to 8589934592
[4830321.315018] bcache: register_bcache() error opening /dev/dm-2: Bad
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[4830328.502621] bcache: register_bcache() error opening /dev/zram0: Bad
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