Date: Fri, 31 Dec 1999 09:02:45 +0800 From: Peter Wemm <peter@netplex.com.au> To: Guido van Rooij <guido@gvr.org> Cc: Hidetoshi Shimokawa <simokawa@sat.t.u-tokyo.ac.jp>, vsilyaev@mindspring.com, dillon@freebsd.org, freebsd-emulation@FreeBSD.ORG, dbutter@wireless.net Subject: Re: VMware: Questions... Message-ID: <19991231010245.C630E1CA0@overcee.netplex.com.au> In-Reply-To: Message from Guido van Rooij <guido@gvr.org> of "Wed, 22 Dec 1999 22:48:03 %2B0100." <19991222224803.A410@gvr.gvr.org>
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Guido van Rooij wrote:
> On Mon, Dec 20, 1999 at 11:31:49PM +0800, Peter Wemm wrote:
> > >
> > > This is because mmaped file is written every 30 second by sync daemon.
> > > The file is usually named /var/tmp/ram0 but it's unlinked right after
> > > opened so you cannot see it by 'ls' although it exits.
> >
> > It would be nice if the VFS/VM system detected this automatically and
> > switched on NOSYNC for files that got unlinked... I wouldn't be suprised i
f
> > this is what Linux does. Matt, is this possible?
> >
>
> I havent seen an answer to this question yet. If it is possible, that
> would be very nice. I doubt it though, but my knowledge on that part
> of the system is rather limited.
> A quick workaround could be to look at the ref count of the underlying
> inode of the fd passed to the linux mmap
> If the refcount is one then clearly the inode is no being referenced through
> a directory entry in the file system. This could even be done for the general
> mmap call (provided a regular file of course). But it might be a very
> specific situation because one usually would not used a file backed
> mmap in FreeBSD, yet use an anonymous mmap.
I had a go, it turned out to be quite easy (so far). I haven't finished
verifying that it's doing everything exactly as expected yet though.
Cheers,
-Peter
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