Re: Fwd: Cloning a Btrfs partition

[Jan Schmidt <list.btrfs@jan-o-sch.net>]

Hi BJ,

[original message rewrapped]

On Thu, July 25, 2013 at 18:32 (+0200), BJ Quinn wrote:
> (Apologies for the double post -- forgot to send as plain text the first time
> around, so the list rejected it.)
> 
> I see that there's now a btrfs send / receive and I've tried using it, but
> I'm getting the oops I've pasted below, after which the FS becomes
> unresponsive (no I/O to the drive, no CPU usage, but all attempts to access
> the FS results in a hang). I have an internal drive (single drive) that
> contains 82GB of compressed data with a couple hundred snapshots. I tried
> taking the first snapshot and making a read only copy (btrfs subvolume
> snapshot -r) and then I connected an external USB drive and ran btrfs send /
> receive to that external drive. It starts working and gets a couple of GB in
> (I'd expect the first snapshot to be about 20GB) and then gets the following
> error. I had to use the latest copy of btrfs-progs from git, because the
> package installed on my system (btrfs-progs-0.20-0.2.git91d9eec) simply
> returned "invalid argument" when trying to run btrfs send / receive. Thanks
> in advance for any info you may have.

The problem has been introduced with rbtree ulists in 3.10, commit

    Btrfs: add a rb_tree to improve performance of ulist search

You should be safe to revert that commit, it's a performance optimization
attempt. Alternatively, you can apply the published fix

    Btrfs: fix crash regarding to ulist_add_merge

It has not made it into 3.10 stable or 3.11, yet, but is contained in Josef's
btrfs-next

    git://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-next.git

Thanks,
-Jan