Re: F21 fails to mount root part, btrfs check: Couldn't open file system

[Kai Krakow <hurikhan77@gmail.com>]

Kai Krakow <hurikhan77@gmail.com> schrieb:

> Chris Murphy <lists@colorremedies.com> schrieb:
> 
>> On Tue, Mar 31, 2015 at 2:09 PM, Chris Murphy <lists@colorremedies.com>
>> wrote:
>> 
>>> Well you have to rule that out before anyone on this list can really
>>> help. Try booting Fedora 21 install media, and using smartctl -x on
>>> the drive.
>> 
>> While you're at it, try to mount the Btrfs volume in question normally
>> and report kernel messages. If mount fails, try it with -o recovery
>> mount option, and also report kernel messages and whether that fails.
> 
> I had this happen, too, lately. It's quite often happening after an
> unclean shutdown (which currently quite often happend to me due to the
> xorg intel driver having GPU freezes). SysRq+W shows that the mount
> process is locked somewhere in the btrfs code path and won't quit if
> Ctrl+C'd...
> 
> Only way to fix it was to btrfs-zero-log. But it still took some reboots
> from initramfs until it successfully mounted again (I could mount it in
> initramfs right after zero-log but upon reboot it hung again though at a
> different stage probably).
> 
> So I guess there's some race on the one hand (happens from time to time
> non- related to fixing it with zero-log), and a deadlock on the other hand
> after some unclean shutdowns (more or less random).
> 
> My setup is 3-device btrfs-mraid1-draid0 on bcache. Bcache wasn't involved
> in the backtrace of SysRq+W, however. Apparently I don't have a screenshot
> of it because my smart phone is currently fried...

BTW: I tried all kernels from current 3.19.x back to 3.18.0 which still live 
on my boot partition - each with the same result and very similar backtrace 
(SysRq+W)...

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