Can't enable writeback

Can't enable writeback

[Nick Payne]

I've installed kernel 3.10.7 on Ubuntu 13.04 amd64, and bcache-tools 
from 
https://launchpad.net/~mighost/+archive/ppa/+build/4767454/+files/bcache-tools_1.0-1ppa1%7Eraring_amd64.deb. 
I can create a bcache volume and mount and use it without any problems 
using writethrough (120GB Intel 330 SSD caching a WD 2GB HDD), but when 
I try to enable writeback:

   sudo echo writeback > /sys/block/bcache0/cache_mode

it returns the error

   bash: /sys/block/bcache0/cache_mode: No such file or directory

/sys/block/bcache0 exists as a link:

   ls -l /sys/block/bc*
   lrwxrwxrwx 1 root root 0 Aug 17 15:58 /sys/block/bcache0 -> 
../devices/virtual/block/bcache0

Suggestions on how to enable writeback?

Nick Payne

Re: Can't enable writeback

[Gabriel de Perthuis]

> I try to enable writeback:
> 
>    sudo echo writeback > /sys/block/bcache0/cache_mode
> 
> it returns the error
> 
>    bash: /sys/block/bcache0/cache_mode: No such file or directory

You're confusing bcache0 with bcache0/bcache

    echo writeback |sudo tee -a /sys/block/bcache0/bcache/cache_mode

will work.

Re: Can't enable writeback

[Nick Payne]

On 17/08/13 22:56, Gabriel de Perthuis wrote:
>> I try to enable writeback:
>>
>>     sudo echo writeback > /sys/block/bcache0/cache_mode
>>
>> it returns the error
>>
>>     bash: /sys/block/bcache0/cache_mode: No such file or directory
> You're confusing bcache0 with bcache0/bcache
>
>      echo writeback |sudo tee -a /sys/block/bcache0/bcache/cache_mode
>
> will work.

Thanks, that works. The command I was originally trying to use is what 
is shown in the documentation at 
http://evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt. 
It has

     # echo writeback > /sys/block/bcache0/cache_mode

as the command to run.