[issue1082] dfly-2.0.0-REL: panic: hammer: insufficient undo FIFO space!

[Matthew Dillon]

    Ok I've tracked it down.  There are two issues, both related to the
    fact that the filesystem is really small.

    The main bug is actually with newfs_hammer.  When a small filesystem
    is created newfs_hammer reserves way too small a space for the UNDO
    FIFO.  A 6G filesystem only reserves 8M of undo space!  That isn't
    enough.  100M is really the minimum.  I am going to change newfs_hammer
    to enforce that.

    The second issue is that the filesystem is really too small.  I don't
    want to disallow the creation of small filesystem but I think I will
    also change newfs_hammer to spit out a bunch of warnings when people
    create such small filesystems.

    Finally, keep in mind that you may hit up against serious free space
    issues and may have to run 'hammer prune-everything ...' as well
    as 'hammer reblock ...' quite often on such a small filesystem,
    depending on use.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>