I ran into the same bug as Heiko Wundram reported a while back: after a
few (2-4) days of normal desktop usage, bcache hangs and dstat shows
continuous 50MB/s write to the cache SSD partition with one CPU core maxed
out in IO wait. I remembered Kent's answer to the later message, and at
least echoing 0 to writeback_running did nothing in my system. The bcache
device consists of an SSD partition and two disks in md raid0, and there
is dmcrypt on top of bcache.
The branch was bcache patched to a 3.7.10 (Gentoo) kernel. Is bcache the
correct branch, or should I be using bcache-for-upstream? (There are many
branches in the git repo, but I can't find any documentation/description
on what they are and who should use them.)
I had to revert back to the previous setup, which was bcache-3.2 patched
to a 3.6.11 kernel and which doesn't have the problem. But it looks like
bcache-3.2 cannot be trivially (i.e. without more detailed knowledge about
bcache and the bio subsystem) ported to 3.7 kernels, so I guess I'll be
stuck with 3.6 until the bug is fixed.
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