Disabling bcache from boot when it crashes?

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/