Re: [nfsv4] RFC 7530: Filehandle of opened file after the REMOVE

[Christoph Hellwig <hch@lst.de>]

On Wed, Jan 04, 2017 at 12:42:45PM -0500, Bruce James Fields wrote:
> Dumb question: don't local filesystems have the ability to do some sort
> of emergency conversion to read-only on detecting corruption?

Yes.

> Does that
> prevent any open-file cleanup?

Yes, at least before the reboot.

> If not that, is there some other
> mechanism nfsd could use to crash the filesystem on shutdown if
> appropriate (so if it's holding opens on a filesystem and if the
> filesystem was mounted with the new option)?
> 
> Possibly better would be if we could keep a separate list of
> unlinked-but-still-held-by-nfsd files that was managed diferently than
> the existing list.
> 
> But, I don't have the local filesystem knowledge to know where the
> nightmares are here.

Maybe I shouldn't have called it a nighmare, but it's significantly
more effort.  We'll need a way for NFSD to mark a file as not being
allowed to cleaned up before the final iput for the reboot case
mostly.

I'll try to come up with a prototype later this month, but it might not
be pretty.