[issue1729] Hammer REDO recovery panic

[Matthew Dillon]

:New submission from Venkatesh Srinivas <me at acm.jhu.edu>:
:
:Restarting my system after an earlier panic from running fsstress on HAMMER, 
:fsync_mode=2. Running DragonFly 2.6.0-gfa1ae. Will try to have a dump tomorrow.
:
:Mounting root from hammer:serno/G3H3DSKC.s1d
:tryroot serno/G3H2DSKC.s1d
:HAMMER(ROOT) recovery check seqno=023f0d60
:HAMMER(ROOT) recovery range 3000000003838438-3000000003fee500
:HAMMER(ROOT) recovery nexto 3000000003fee500 endseqno=023f6204
:HAMMER(ROOT) recovery undo 3000000003838438-30000000003fee500 (8085704 
:bytes)(RW)
:HAMMER(ROOT) Continuing recovery
:HAMMER(ROOT) Continuing recovery
:HAMMER(ROOT) Continuing recovery
:HAMMER(ROOT) Continuing recovery
:HAMMER(ROOT) Found REDO_SYNC 30000000025c4a38
:HAMMER(ROOT) recovery complete
:HAMMER(ROOT) recovery redo 3000000003838438-30000000003fee500 (80857604 
:bytes)(RW)
:HAMMER(ROOT) Find extended redo  30000000025c4a38, 19347968 extbytes
:HAMMER(ROOT) Find extended redo failed 34, unable to run REDO
:HAMMER(ROOT) End redo recovery
:panic: hammer_ref_interlock_true: bad lock 0xc758a688 00000001
:
:Trace beginning at frame 0xc05d4af4
:panic(c05d4b18,50000001,c758a680,c02ed226,c05d4b24) at panic+0x8c
:...

    Ok, I found the bug related to the panic.  I have committed a
    fix to head and will MFC to 2.6.x.

    The REDO error itself is another problem.  That error is not supposed
    to happen.  Please run the command 'hammer -f <device> show-undo' and
    put the output on your leaf account.  How large is the HAMMER filesystem?
    (Hopefully the data hasn't been lost since that time, I'm crossing my
    fingers).

    You may have issues booting.  You need to boot with a fixed kernel to
    get past the panic and that may require booting from a USB stick or
    something

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>