[arch-general] [signoff] btrfs-progs

[C Anthony Risinger]

On Sat, Aug 4, 2012 at 7:53 AM, Jackson Alley <toomanymirrors at gmail.com> wrote:
>
> I've rebooted and confirmed the udev rule I found does not resolve the
> issue. I don't believe the problem lies with mkinitcpio as I'm not using
> a root btrfs system but rather in the init scripts
> (https://projects.archlinux.org/initscripts.git/commit/?id=13ca7f028ac775773a6685966d0faeee5cc55a9d).
> I've attached the boot log and dmesg output.
> dmesg: http://pastebin.com/PxfnYgAm
> boot log: http://pastebin.com/Pg9xY4u5

yeah i didn't think mkinitcpio was involved but you said it was
throwing an error about a missing btrfs hook, even though you have no
hook defined ... so i asked.

AFIAK the FS module is not loaded automatically until mount time --
dmesg shows the module being loaded at that time, not when scanned.
dracut loads the module just prior to calling `device scan`:

http://git.kernel.org/?p=boot/dracut/dracut.git;a=blob;f=modules.d/90btrfs/80-btrfs.rules;h=e74f9a6af647e465d9367e95b37aef2e57ddfdbe;hb=HEAD

... and since scanning requires /dev/btrfs-control, which is not
created until the btrfs module is loaded, the module MUST be loaded to
properly register the device.  i was able to confirm that `btrfs
device scan` DOES NOT automatically load the required `btrfs` module.

your dmesg shows required devices loading at this time:

[    4.058562] sd 9:0:0:0: [sde] 976773168 512-byte logical blocks:
(500 GB/465 GiB)

... but the module is not loaded until after all devices fire:

[    4.171028] Btrfs loaded

... therefore probably nothing was registered, and thus a few seconds
later you see:

[    6.081051] btrfs: failed to read the system array on sde1

... try this (tested for one device, unverified for more):

# cat /usr/lib/udev/rules.d/70-btrfs.rules
ACTION!="remove", SUBSYSTEM=="block", ENV{ID_FS_TYPE}=="btrfs",
RUN+="/sbin/modprobe btrfs", RUN+="/usr/bin/btrfs device scan
$env{DEVNAME}"

-- 

C Anthony