On Fri, Feb 26, 2016 at 04:55:02AM +0000, Eric Wheeler wrote:

According to Documentation/bcache.txt:
	"" If you're booting up and your cache device is gone and never
	coming back, you can force run the backing device:
	  echo 1 > /sys/block/sdb/bcache/running
	[...]
	The backing device will still use that cache set if it shows up
	in the future, but all the cached data will be invalidated.  ""

So it seems that you are safe.  (It would be interesting to know how it 
invalidates the cache.  Maybe bumps the Set UUID?  Not sure.)

 
Yeah, that was  my understanding too, but I wanted to make sure.
Strangely (worringly so?) the cache was replayed at boot, and this time
nothing crashed, or any traceback.

Now I'm wondering if it pushed garbage onto my filesystem :-/

Again, no netconsole, sorry, this happens before my ethernet interface
comes up.
https://goo.gl/photos/suqp9sHyijdt9iUG7

sda6 was the partition I hid and just came back.
sdb1 is the bcache linked to it.

On the plus side, no crash, although this didn't get to exercise your
new code either.

Either way, I'm really starting to have mixed feelings about using
writeback if it's going to give me random crashes and subsequent
corruption (which is a risk listed in the doc, admittedly).

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901