Issue (as expected) when upgrading from 3.12 to 3.13.7

[Francis Moreau <francis.moro@gmail.com>]

Hello,

As I was expecting I'm getting new issues with bcache after upgrading my
kernel:

[Mar30 12:24] INFO: task bcache_writebac:155 blocked for more than 120
seconds.
[  +0.000007]       Not tainted 3.13.7-1-ARCH #1
[  +0.000002] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[  +0.000003] bcache_writebac D 0000000000000000     0   155      2
0x00000000
[  +0.000006]  ffff8804049c5eb8 0000000000000046 ffff880405816c00
ffff8804049c5fd8
[  +0.000005]  0000000000014440 0000000000014440 ffff880405816c00
ffff8804049c5e38
[  +0.000004]  ffffffff810925fa 24448b48e0d83524 fa83ffffee31e918
0000000000000046
[  +0.000004] Call Trace:
[  +0.000010]  [<ffffffff810925fa>] ? try_to_wake_up+0x1fa/0x2c0
[  +0.000006]  [<ffffffff81092712>] ? default_wake_function+0x12/0x20
[  +0.000005]  [<ffffffff810a2538>] ? __wake_up_common+0x58/0x90
[  +0.000023]  [<ffffffffa03c7470>] ? read_dirty_endio+0x60/0x60 [bcache]
[  +0.000005]  [<ffffffff81516239>] schedule+0x29/0x70
[  +0.000006]  [<ffffffff8108358d>] kthread+0xad/0xf0
[  +0.000005]  [<ffffffff810834e0>] ? kthread_create_on_node+0x180/0x180
[  +0.000005]  [<ffffffff81521abc>] ret_from_fork+0x7c/0xb0
[  +0.000005]  [<ffffffff810834e0>] ? kthread_create_on_node+0x180/0x180

That's just sad to see how unstable was/is bcache sub system and I still
don't understand why it was not marked as experimental.

3.12 was/is buggy when used with writeback mode, and I just had to live
with cache-through. I tried to get some helps (and others too) but no
answers.

I read there were issue with 3.13, so I delayed my kernel upgrade as far
I could due to this. I was hoping that issues were fixed in 3.13.x
stable tree but apparently not.

Hopefully this one will not be ignored.

Thanks