Btrfs: make metadata chunks smaller

Btrfs: make metadata chunks smaller

commit 83d3c9696fed237a3d96fce18299e2fcf112109f upstream.

This patch makes us a bit less zealous about making sure we have enough free
metadata space by pearing down the size of new metadata chunks to 256mb instead
of 1gb.  Also, we used to try an allocate metadata chunks when allocating data,
but that sort of thing is done elsewhere now so we can just remove it.  With my
-ENOSPC test I used to have 3gb reserved for metadata out of 75gb, now I have
1.7gb.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>