[Libguestfs] nbdkit build failure in Koji

[Richard W.M. Jones]

On Fri, Jul 31, 2020 at 09:11:51AM -0500, Eric Blake wrote:
> Growing a small amount but still being sparse is different from
> growing a huge amount to be non-sparse altogether.  I'll have to
> double-check what the test is actually doing (the size of the files
> involved) and see if we can relax the test into allowing a range of
> sizes that show a file is still reasonably sparse.  But knowing what
> filesystem koji is using may matter (for example, if this is
> something that shows up on btrfs but not ext4, that would explain
> why koji fails when I pass locally...)

So about btrfs: While Fedora is planning to use btrfs for desktop
installs in future, that hasn't happened so far, isn't planned for the
server editions, and I doubt will ever affect Koji because that uses
RHEL.  Nevertheless I thought it'd be interesting to try it because I
don't think I've ever used btrfs for this.

$ nbdkit memory 4G allocator=zstd

# modprobe nbd
# nbd-client -b 512 localhost /dev/nbd0
# mkfs.btrfs /dev/nbd0
# mount /dev/nbd0 /tmp/mnt
# chown rjones.users /tmp/mnt

I built nbdkit from git on this filesystem and ran the tests and it
was all fine.

After the tests:

$ stat -f /tmp/mnt
  File: "/tmp/mnt"
    ID: 842a95913d293347 Namelen: 255     Type: btrfs
Block size: 4096       Fundamental block size: 4096
Blocks: Total: 1048576    Free: 801634     Available: 736710
Inodes: Total: 0          Free: 0
$ df -h /tmp/mnt
Filesystem      Size  Used Avail Use% Mounted on
/dev/nbd0       4.0G  968M  2.9G  26% /tmp/mnt

Rich.

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