5.2-BETA: file system bugs considered harmful (was: 5.2-BETA:
giving up on 4 buffers)
ma at dt.e-technik.uni-dortmund.de
Sat Nov 29 04:59:04 PST 2003
Bruce Evans <bde at zeta.org.au> writes:
> I'm not sure if the problem is known for the read-only case. It is
> the same problem as in the read-write case. ext2fs hangs onto buffers,
> so shutdown cannot tell if it can look at the buffers and considers
> them to be busy. Then since shutdown cannot tell if it synced all dirty
> buffers or which buffers are associated with which file systems, it
> doesn't unmount any file systems and all dirty file systems that aren't
> unmounted before shutdown are left dirty. Read-only-mounted ext2fs file
> systems aren't left dirty but they break cleaning of other file systems.
Either way, I consider the underlying bugs harmful.
I tried to modify ext2 files, could read-write mount the partition,
could modify the files and sync, but when I tried to mount -u -r the
ext2 partition or umount it, I got a busy condition, and after reboot,
the changes were lost, and a while later (an hour or so) the machine
panicked in vinvalbuf().
Needless to say that after that, the machine fsck'd the whole disk (all
partitions) and, worse, my root partition was damaged, files missing. I
had run make installworld prior to the panic. My root partition is a
regular noasync UFS1, /usr and /var are softupdates UFS2.
Because of this damage, I consider the underlying file system bugs,
whether in ext2fs or outside, to be harmful. I'm not claiming they're IN
ext2fs (because of the ufs single-user fsck, reboot problem) but they
can be triggered through ext2fs. Something's not quite right.
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