Disabling bcache from boot when it crashes?

[Marc MERLIN <marc@merlins.org>]

On Wed, Feb 24, 2016 at 06:53:05AM +0000, Eric Wheeler wrote:
> Do you have the bcache stability patches? 4.3.3 might be missing some 
> critical patches.
> 
> Be sure to cherry-pick these from linux 4.5-rc1:
> 	git cherry-pick 2ef9ccbf~1..627ccd20
> or use one of the 4.1 or 3.18 longterm kernels.
> 
> I've not see any memory allocation issues before in bcache, but you 
> definitely want those patches for general stability.

I'm running 4.4.2, so I'm assuming I don't have those fixes, thanks for the
heads up.

Well, your message is timely, just as you wrote this, I got bcache that
crashed my system as I was shutting down, and then I was unable to ever
reboot because bcache would detect my partitions, start bcache, and crash
before I could do anything to fix it.

A few questions though:
1) is there any bcache boot option I can give to disable bcache at boot
time?

2) I had to boot from rescue media and sadly the version of wipefs there
wasn't good enough to find the bcache sig and remove it.
I then tried to change the bcache cache partition type to 0, but that didn't
help either.
Eventually I had to shrink the bcache cache partition to 1 cylinder and
finally then it stopped being detected at boot and the crashes stopped.
(dd of /dev/zero would have worked, but it's an ssd, and I didn't want to
allocate blocks on the flash that had not been used yet to give more room
for garbage collection).

Was there a better way of doing this?

Thanks,
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/