btrfs subvolume as an iSCSI target?

[Dan Mossor]

I've been combing the web for a couple days, and most hits I'm finding 
regarding using a btrfs subvolume as an iSCSI target are posts from the 
2009/2010 timeframe stating that that functionality is broken.

I'm working on a couple projects here, and one of those involves the 
research into iSCSI targets and initiators, and the testing thereof. I 
have an F20 system with a 1.3TB btrfs master subvolume (across three 
dissimilar devices), and want to create a subvolume within that to serve 
as an iSCSI target.

The traditional methods, specifically those mentioned in the Fedora Wiki 
and the tgtadm man pages, place the emphasis on using devices (/dev/sdx) 
or files (dd if=/dev/zero of=/array/target1 bs=1k count=1). I realize 
that using the file is probably the easiest thing to do in this 
instance, but that's not the point of my project - I am intentionally 
trying to designate the btrfs subvolume as the target.

The issue I believe that is going to stop me is that tgtadm expects a 
block device as the target, and btrfs does not provide that. Is there a 
workaround, other than using a file in the subvolume as the target? Is 
there work in progress to enable this feature, either in the 
scsi-target-utils package or within the btrfs framework?
-- 
Dan Mossor
Systems Engineer at Large
Fedora QA Team Volunteer FAS: dmossor IRC: danofsatx
San Antonio, Texas, USA