Messages in this thread | | | Date | Thu, 5 Jan 2012 10:36:02 -0800 | From | Tejun Heo <> | Subject | Re: Revoking filesystems [was Re: Sysfs attributes racing with unregistration] |
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Hello, Ted.
On Thu, Jan 05, 2012 at 01:27:52PM -0500, Ted Ts'o wrote: > So it's really more of a filesystem force-umount method. I could > imagine that this could also be used to extend the functionality of > umount(2) so that the MNT_FORCE flag could be used with non-NFS file > systems as well as NFS file systems.
I think these are two separate mechanisms. Filesystems need to be able to handle IO errors no matter what and underlying device going away is the same situation. There's no reason to mix that with force unmount. That's a separate feature and whether to force unmount filesystem on device removal or permanent failure is a policy decision which belongs to userland - ie. if such behavior is desired, it should be implemented via udev/udisk instead of hard coded logic in kernel.
I don't know enough to decide whether such forced unmount is a useful feature tho. It can be neat for development but is there any real necessity for the feature?
> [1] Interesting question: do we convert an mmap region to an anonymous > region and perhaps notify the user out of band this has happened? Or > do we just make the mapping disappear and nuke the process with a SEGV > if it attempts to access it?
FWIW, I vote for SIGBUS similarly to the way we handle mmap vs. truncate.
Thanks.
-- tejun
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