Doug White wrote: > On Sun, 20 Nov 2005, [UTF-8] Václav Haisman wrote: > > >>Hi, >>I got this panic on freshly installed FreeBSD 6. I did this df -h and >>noticed that /mnt/oldroot/home is somewhat mangled. The /mnt/oldroot is >>root of FreeBSD 4.11 system. I successfully copied some settings and all >>user accounts from that /mnt/oldroot/home earlier today. This is what I >>did before the panic: > > > [...] > > I discovered this by accident with a CDROM the other day. In 6.0 you can > overlay read-only mounts (i.e., mount the same R/O FS on top of itself) > but unmounting it will cause GEOM to tear down the underlying device while > leaving the first mount behind. Next access to the mountpoint will panic > the system. > > You can't mount a read/write mount on top of itself, or a r/o mount on a > r/w mount -- you get an error. A quick discussion with phk points to a > faulty or missing access check in GEOM. I'm not familiar with the VFS > operations required to mount a filesystem, though, so I'm not sure where > to look to put in the fix. > > In the interim, be careful not to mount a read-only FS multiple times. >
Thanks, I will remember this. Though it really was not my intention to mount it twice. I did so because I got confused by the mangled `/mnt/oldroot/hom' name in the df output and thought it was not mounted. Vaclav Haisman
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