Re: btrfs says no errors, but booting gives lots of errors

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

covici posted on Sat, 10 Oct 2015 19:08:16 -0400 as excerpted:

> covici@ccs.covici.com wrote:
> 
>> Lionel Bouton <lionel+ceph@bouton.name> wrote:
>> 
>> > Le 10/10/2015 18:55, covici@ccs.covici.com a écrit :
>> > > [...]
>> > > But do you folks have any idea about my original question, this
>> > > leads me to think that btrfs is too new or something.
>> > 
>> > I've seen a recent report of a problem with btrfs-progs 4.2 confirmed
>> > as a bug in mkfs. As you created the filesystem with it, it could be
>> > the problem.
> 
> I do have 4.2.2, I could go to, would that be better?

btrfs-progs-4.2.2 does indeed have the mkfs.btrfs fixes for the bug in 
question.  You should be fine remaking the filesystem with it.

If you created the filesystem with the buggy mkfs.btrfs, AFAIK, current 
4.2.2 btrfs check can detect the error, but can't fix it.  Blowing away 
the filesystem and recreating is the only known fix at this time, and 
filesystems created with the buggy version are not safe and could blow up 
at any time, so it's best to be rid of them and onto something more 
stable as soon as possible.

I can't help with the subvolumes bit, however, because while I'm on 
gentoo/~amd64 here too, also with systemd...

I don't use subvolumes, as to me it's simply putting too many eggs in one 
filesystem basket.  Instead, I prefer multiple separate btrfs 
filesystems, each on their own partitions.  My / includes most of what 
packages install, including /usr and /var but not /var/log.  It's 8 GiB 
in size, under half used.  /home is separate, the repos tree (gentoo and 
overlays) along with ccache, binpackages, the kernel tree, etc, are 
together on a separate partition, /var/log is separate (and tiny, half a 
GiB), etc.  I keep / mounted read-only by default, so have the parts of /
var/lib that must be runtime-writable symlinked to subdirs of /home/var, 
with /home of course mounted writable, but other than that and some /var/
log/ subdirs, anything that's installed by a package is on /, a lesson I 
learned the hard way when I had to recover from backups where /, /usr 
and /var were from backups taken on different dates and thus not 
synchronized with what portage /thought/ was installed based on /var/db/
pkg.

Not saying that's best for you, but it's a solution that I've found works 
very well for me, and the relative small 8 GiB size of / makes it easy to 
have backup copies of it that I can boot, should my working / take a 
dump.  But if it's all on the same filesystem, as it is with subvolumes, 
and that filesystem takes a dump... it's all gone at once!  That's not 
something I want to happen, so I vastly prefer the independent 
filesystems, but with everything (but the limited exceptions mentioned 
above) the package manager deals with on the same one, so it all stays 
synced and is backed up as a single unit, which after all remains 
reasonably small, 8 GiB, less than half used.

-- 
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