Building a brtfs filesystem < 70M?

[Saul Wold <sgw@linux.intel.com>]

Hi There

There seems to be an issue if we try to build a btrfs based FS that is 
less than 70M, we get the following assertion failure:

mkfs.btrfs: extent-tree.c:2682: btrfs_reserve_extent: Assertion `!(ret)' 
failed.

I tried to do a search on this and did not find anything obvious.

Further, if I do build a 70M image, it will not mount until I get to I 
increase  the about 100M!

# mount -o loop -v rootfs.btrfs mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
        missing codepage or helper program, or other error

        In some cases useful info is found in syslog - try
        dmesg | tail or so.

I can provide a small rootfs (~4M) example if needed

Builds and mounts correct:
mkfs.btrfs -b 104857600 -r rootfs rootfs.btrfs

Builds, but does not mount:
mkfs.btrfs -b 73400320 -r rootfs rootfs.btrfs

Does not build, gives the above assertion error:
mkfs.btrfs -b 10889216 -r rootfs rootfs.btrfs


Thanks


-- 
     Sau!

Saul Wold
Yocto Component Wrangler @ Intel
Yocto Project / Poky Build System