BTRFS subvolumes

[Frank Steinberg]

Hi Kerim,

> Am 06.10.2016 um 17:33 schrieb Kerim Güney <kerim at gueney.org>:
> 
> Hey Frank,
> 
> I remember that Thomas and I had specifically decided against implementing that functionality. setup-storage is supposed to only create a single subvolume per btrfs partition.

I respect the developers’ decision. But is there a reason? This would make FAI not that fully automated. ;-)

> The unnecessary mkfs calls do surprise me, though. I probably won't be able to check it out until the weekend but could you please email me a sample configuration similar to what you initially tried to use?

disk_config disk1 disklabel:msdos bootable:1
primary	/boot		512			ext4	rw
primary	swap		4G			swap	rw
primary	-		20G-			-	-

disk_config btrfs
btrfs single	/			disk1.3		subvol=@root,defaults,noatime,compress=lzo
btrfs single  	/opt			disk1.3		subvol=@opt,defaults,noatime,compress=lzo
btrfs single  	/var/lib/mysql		disk1.3		subvol=@mysql,defaults,noatime,nodatacow





> 
> Best regards 
> 
> Am 6. Oktober 2016 10:49:44 MESZ, schrieb Frank Steinberg <steinberg at ibr.cs.tu-bs.de>:
> Hi,
> 
> I intend to switch my FAI setups from using ext4 to btrfs, with no RAID levels („single“), but with subvolumes (on a common toplevel volume). With the current setup-storage code, I could not get this working. The main reason is that each volume under the btrfs config section causes a new mkfs.btrfs command, so that subsequent volumes cause unneeded mkfs calls which also override previously created subvolumes.
> 
> I am not very familiar with the setup-storage code and its concepts and I am not at all a perl programmer, however the following patch seems to solve my problem as a quick workaround. Maybe it could be useful to others, and maybe it could give Thomas an idea to improve his code.
> 
>  -frank
> 
> 
> --- Commands.pm 2016-07-01 17:31:38.000000000 +0200
> +++ Commands.pm.ibr 2016-10-06 10:29:51.462135735 +0200
> @@ -354,11 +354,24 @@
>      }
>      # creates the BTRFS volume/RAID
>      if ($raidlevel eq 'single') {
> -          &FAI::push_command("mkfs.btrfs -d single $createopts ". join(" ", at devs),
> + my $first = 1;
> + my $c = "mkfs.btrfs -d single $createopts ".join(" ", at devs);
> + my $ii = 1; while ($ii < $FAI::n_c_i) {
> +   if ($FAI::commands{$ii}{cmd} eq $c) {
> +     $first = 0;
> +   }
> +   $ii++;
> + }
> + if ($first == 0) {
> +          &FAI::push_command("true",
>                               "$pre_req",
>                               "btrfs_built_raid_$id");
> -
>          } else {
> +          &FAI::push_command("mkfs.btrfs -d single $createopts ". join(" ", at devs),
> +                             "$pre_req",
> +                             "btrfs_built_raid_$id");
> + }
> +      } else {
>            &FAI::push_command("mkfs.btrfs -d raid$raidlevel $createopts ". join(" ", at devs),
>                               "$pre_req",
>                               "btrfs_built_raid_$id“);
> 
> 
> 
> 
> 
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