[arch-general] [signoff] btrfs-progs

[Tom Gundersen]

On Aug 5, 2012 6:04 AM, "C Anthony Risinger" <anthony at xtfx.me> wrote:
>
> 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}"

This makes a lot of sense. Please verify.

Tom