Re: Persistent memory file system development in Rust

[Matthew Wilcox <willy@infradead.org>]

... This time with the correct email address for the Rust list.

On Wed, Jan 26, 2022 at 10:35:19PM +0000, Matthew Wilcox wrote:
> On Tue, Jan 25, 2022 at 04:02:56PM -0600, Hayley Leblanc wrote:
> > I'm a PhD student at UT Austin advised by Vijay Chidambaram (cc'ed).
> > We are interested in building a file system for persistent memory in
> > Rust, as recent research [1] has indicated that Rust's safety features
> > could eliminate some classes of crash consistency bugs in PM systems.
> > In doing so, we'd like to build a system that has the potential to be
> > adopted beyond the research community. I have a few questions (below)
> > about the direction of work in this area within the Linux community,
> > and would be interested in hearing your thoughts on the general idea
> > of this project as well.
> 
> Hi Hayley,
> 
> Thanks for reaching out to us.
> 
> First, my standard advice for anyone thinking of writing a Linux
> filesystem: Absolutely do it; you'll learn so much, and it's a great deal
> of fun.  Then my standard advice for anyone thinking about releasing a
> Linux filesystem: Think very carefully about whether you want to do it.
> If you're lucky, it's only about as much work as adopting a puppy.
> If you're unlucky, it's like adopting a parrot; far more work and it
> may outlive you.
> 
> In particular, the demands of academia (generate novel insights, write
> as many papers as possible, get your PhD) are at odds with the demands
> of a production filesystem (move slowly, don't break anything, DON'T
> LOSE USER DATA).  You wouldn't be the first person to try to do both,
> but I think you might be the first person to be successful.
> 
> There's nothing wrong with having written an academic filesystem
> that you learned things from.  I think I've written three filesystems
> myself that have never seen a public release -- and I'm totally fine
> with that.
> 
> > 1. What is the state of PM file system development in the kernel? I
> > know that there was some effort to merge NOVA [2] and nvfs [3] in the
> > last few years, but neither seems to have panned out.
> 
> Correct.  I'm not aware of anything else currently under development.
> I'd file both those filesystems under "Things people tried and learned
> things from", although maybe there'll be a renewed push to get one
> or the other merged.
> 
> > 2. What is the state of file system work, if any, on the Rust for
> > Linux side of things?
> 
> I only have a toe in Rust development, but I'm not aware of
> any work being done specifically for filesystems, that said ...
> 
> > 3. We're interested in using a framework called Bento [4] as the basis
> > for our file system development. Is this project on Linux devs' radar?
> > What are the rough chances that this work (or something similar) could
> > end up in the kernel at some point?
> 
> Bento seems like a good approach (based on a 30 second scan of their
> git repo).  It wasn't on my radar before, so thanks for bringing it up.
> I think basing your work on Bento is a defensible choice; it might be
> wrong, but the only way to find out is to try.
> 
> All this is just my opinion, and it's worth exactly what you're paying
> for it.  I have no say in what gets merged and what doesn't, and I
> decided academia was not for me after getting my BSc.  I hope it all
> works out for you, and we end up seeing your paper(s) in FAST.