On Fri, Jun 09, 2017 at 01:53:01AM +0000, Eric Wheeler wrote:

quoted

gargamel:/sys/block/bcache1# l ../md8/bcache
ls: cannot access '../md8/bcache': No such file or directory

Don't trust ../ to link correctly with so many symlinks floating around.  
Sometimes ../ will be interpreted correctly via a link path, other times 
it will use the '..' inode's content which may not be the way you came in.  
I'm not saying thats the problem, but perhaps...

 
Right, but basically it wasn't an issue here, it was just making cut and
paste shorter.

quoted

 echo /dev/md8 > 4a46e74d-0376-41e7-aff4-0a0497b9e3c5/unregister 

Try echo 1 > uuid/unregister

I'll try next time if there is one.
Sadly, I couldn't wait anymore and have already rebooted.

quoted

gargamel:/sys/block/bcache1/bcache# echo /dev/md8 >  /sys/fs/bcache/register 
bcache: register_bcache() error opening /dev/md8: device already registered

Looks like stop doesn't unregister the device, I can't re-register it,
nor restart it.

Or am I missing something?
I'd love not to have to reboot to recover :)

Is /dev/md8 the cache or bdev?

 
It was the cache. I pasted:
lrwxrwxrwx  1 root root    0 Jun  4 18:53 bcache -> ../md8/bcache
lrwxrwxrwx  1 root root    0 Jun  4 18:53 bdi -> ../../bdi/252:16/

Did you stop the cache, too, in /sys/fs/bcache/uuid/stop? 

Stopping via /sys/block/bcache0/bcache/stop doesn't stop the cache IIRC.

I wasn't trying to stop the cache, just to re-assign it to the backing
device it had just been removed from for testing as per your request.

Marc
-- 
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Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901