Current limitations are that disc accounting is not done correctly yet so be carefull not to run out of space on disc and that writing to metadata partitions is not implemented yet. Also fsck_udf(8) is not yet finished, but will be added later.''

[Tags: filesystem, udf]

Another project that was started by Antti after his work to run filesystem code in userland is "rump". The project allows to use "ordinary" filesystems that usually run inside the kernel, and mimic an environment similar to what's available inside the kernel, and move the whole filesystem into userland - verbatime, with no code changes! This allows to develop filesystem code in userland, and later on move it inside the kernel with no further changes - a bit step forward for filesystem development!

This all sounds rather easy, but as filesystems need to move data between storage and memory, a big issue in filesystems is interfacing with the virtual memory subsystem, and adding interfaces like puffs and ReFUSE also needs to consider VM for efficient transfers and caching.

Work in this area is still ongoing, and I've asked Antti about his recent achievements in this area[1]. While the only user-visible change is caching and performance improvements in the Secure Shell filesystem's handler "mount_psshfs", most of the changes are on the inside. Antti wrote me: ``The interesting ones from a programmer's perspective are probably:

• Splitting userspace transport out of puffs in the kernel (putter)
• Using putter to implement support for userspace block/char device drivers (pud). pud does still not have a userspace library similar to libpuffs. libpuffs needs to become libputter and lib{puffs,pud}.

• Removing special case handling for the puffs user/kernel protocol transport. This means that file system requests can now be read/written like any other protocol. This is covered in the AsiaBSDCon 2008 paper "Send and Receive of File System Protocols: Userspace Approach With puffs"

  With some minor work in libpuffs, it possible to e.g. do an ffs mount from a remote site with the help of rump.

With puffs and rump, there are two very interesting and active projects doing research in filesystems on NetBSD, which may lead to changes in the way filesystems are understood in the Unix world. While there, a third project that may be worth watching in this regards is this year's Google hurdt Summer of Code project by Marek Dopiera, which aims at implementing Hurd translators for NetBSD,

Update: Antti dropped me a note that another project related to filesystems is this year's "fs-utils" SoC project. The goal is to create a userland tool to manipulate filesystem images, and the idea is to reuse kernel code with the ukfs library. That way, no redundancy between kernel sources and userland sources are created, and both areas benefit from mutual testing and code maturity.

[Tags: filesystem, fuse, google-soc, kernel, puffs, refuse]

Now while having a new interface for filesystems in userspace is all nice and dandy, there's already such a thing which (of course) differs in details and is not compatible with the puffs interface: Linux' Filesystem in Userspace (FUSE). Alistair Crooks has sat down and implemented "refuse", a FUSE-compat library for puffs that allows using Linux FUSE filesystems with NetBSD's puffs.

After compatibility with Linux on the source level was realized, FUSE-based filesystems can be ported to NetBSD easily, and a separate category was created for them in NetBSD's Packages System: pkgsrc/filesystems (link will work shortly ;). Packages that are available right now:

• fuse: Filesystem in Userspace (compat headers, pkg-config files, etc.), needed for pkgsrc on Linux
• fuse-archivemount: FUSE gateway to libarchive
• fuse-cddfs: FUSE filesystem that uses libparanoia for audio CDs
• fuse-cryptofs: FUSE encrypted filesystem
• fuse-curlftpfs: FUSE filesystem for acessing FTP hosts
• fuse-httpfs: FUSE HTTP filesystem
• fuse-lzofs: Filesystem which allows you to transparently use compressed files

Please note that this is an area where heavy development is still going on, and that this work is only available on NetBSD-current. Upcoming work that we can look forward for are improvements on FUSE compatibility and a port of the ntfs-3g filesystem, an open source, freely available NTFS driver for Linux with read and write support. Many more FUSE modules/filesystems are available, so it can be expected that there's more to come.

[Tags: filesystem, fuse, puffs]

See his mail to tech-kern for more information!

[Tags: filesystem, kernel, udf]

[After mounting knowfs], all VOP_RENAMEs to the smart folder will be intercepted by KFS. The use of the mv program to drop files into the smart folder will result in the data getting sorted automatically. For example one can just state that all pdfs go into a pdf/ folder, and all mp3s are to be parsed by a mp3.s script. A drag and drop into this folder, will cause the action to be taken on the file. '' See the homepage for a lot more data and nice graphs. Reminds me a bit of the NetBSD/Summer-of-Code "userfs" project, but I may be wrong. Good to see the tradition of research being carried out on NetBSD continuing!

[Tags: compsci, filesystem]