[issue1504] hammer crash on cleanups

[Matthew Dillon]

:Hi!
:
:I had something very similar on 95% full hammer FS with version of FS =3D 1=
:.
:After upgrading it to v2 panics vent away.
:
:...
:Also here are some interesting lines in /var/log/messages, possibly
:indicating corrupted media:
:
:Sep 16 01:22:42 dfly kernel: ad4: WARNING - WRITE_DMA UDMA ICRC error
:(retrying request) LBA=3D92046464
:Sep 16 01:26:18 dfly syslogd: kernel boot file is /boot/kernel
:Sep 16 01:26:18 dfly kernel: ad4: FAILURE - device detached
:Sep 16 01:26:18 dfly kernel: subdisk4: detached
:Sep 16 01:26:18 dfly kernel: HAMMER(Share_Big): Critical error
:...
:--=20
:Dennis Melentyev

    Gotta be two different things.  Basically ad4 had a DMA error and
    detached and the HAMMER filesystem, being unable to write, threw a fit.
    That would be an issue with NATA.  HAMMER was just saving itself.

    That sort of UDMA failure is usually indicative of an IDE wiring
    issue.

    We did fix a bug in HAMMER related to very rare incorrect B-Tree
    deletions which would lead to lost inodes and potentially panics.
    Anything like that should no longer occur.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>