Re: [PATCH] [Request for inclusion] Filesystem in Userspace

Miklos Szeredi
2004-11-18T18:26:24Z

> Why do you think it would kill the FUSE process? And why do you think
> killing _any_ process would make the system come back to life? After all,
> memory wasn't filled by process usage, it was filled by dirty FS pages.

Well, killing the fuse process _will_ make the system come back to
life, since then all the dirty pages belonging to the filesystem will
be discarded.

> I really do believe that user-space filesystems have problems. There's a
> reason we tend to do them in kernel space.

Well, NFS with a network failure has the same problem. It's not the
userspace that's the problem, it's the non-reliability.

> But limiting the outstanding writes some way may at least hide the thing.

Currently shared writable mappings aren't allowed for non-root by
default in FUSE. And since non-mmap writes do not dirty pages on the
long run, it's harder to run out of space with them: you need a new
filedescriptor for each page you want to steal, and you will run out
of them sooner than of pages.

So I believe that FUSE is quite secure in this respect. Please prove
me wrong!

Thanks,
Miklos