Re: System crash while scrubbing on 3.18.x

[Duncan <1i5t5.duncan@cox.net>]

Cameron Berkenpas posted on Tue, 17 Mar 2015 10:26:10 -0700 as excerpted:

> I've figured out at least part of the issue.
> 
> I had blk-mq enabled by default (SCSI_MQ_DEFAULT=y). I've since set
> SCSI_MQ_DEFAULT=n, and now I'm completely stable with 4.0-rc4, 3.18.9,
> and presumably all the others. This is on both the bcache and non-bcache
> systems.
> 
> All of my systems with btrfs and SCSI_MQ_DEFAULT=y are stable unless
> they're using a 3ware 9750 controller (which I believe is the 3w-sas
> driver from the top of my head). So either there's a bug with
> blk-mq+3w-sas+btrfs, or just blk-mq+3w-sas. I suspect the latter, but if
> I can find the time, I'll try to test with another filesystem.
> 
> I suspect other controllers/drivers could be affected as well.
> 
> Are any btrfs devs interested in me looking into this further?
> 
> As a side note, in spite of all the crashes I've had through out my
> testing etc, bcache+btrfs hasn't given me any issues like I've seen in
> the past. This is just a few weeks worth of testing, but it seems
> there's at least some sort of basic stability with bcache+btrfs now.

Wow.  Thanks!

I'm not a dev so won't attempt to answer whether they have further 
interest or not, but thanks for keeping with this until you found the 
scsi-mq and 32-sas connection and reported it.  It'll very possibly be of 
use to someone else later, and meanwhile, that's one less instability-
mystery hanging over btrfs alone, now, which surely lets all regulars 
here rest easier. =:^)

And that despite all the crashes during testing, bcache+btrfs didn't 
demonstrate any filesystem instabilities, demonstrates how far both of 
those components has come, each on its own and working together, as 
well.  I know we get bcache+btrfs questions from time to time and the 
stability here even under repeated crashes triggered by unrelated factors 
is something I'm sure many will find reassuring. =:^)

So thanks, again! =:^)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman