Re: [RFC PATCH] Introduce filesystem type tracking

From: Christoph Hellwig
Date: Tue May 20 2008 - 09:57:47 EST

On Tue, May 20, 2008 at 02:43:06PM +0100, Al Viro wrote:
> No, you have not and no, doing that anywhere near that layer is hopeless.
> a) Instances of filesystem can easily outlive all vfsmounts,
> let alone their attachment to namespaces.
> b) What should happen if init is done in the middle of exit?
> c) Why do we need to bother, anyway?

We had a discussion about filesystems starting threads without an
active instance. I suggested tracking instances and add ->init / ->exit
methods to struct file_system_type for these kinds of instances.

But we should track superblock instances, not vfsmount instances of
course. Tom, you probably don't even need a counter, emptyness
of file_system_type.fs_supers should be indication enough. And yes
we'd need locking to prevent init racing with exit.

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