8 ms·

Interesting article. So is the “unfriendliness” of Linux kernel developers towards ZFS that is mentioned strictly due to licensing issues or are there other po

Interesting article. So is the “unfriendliness” of Linux kernel developers towards ZFS that is mentioned strictly due to licensing issues or are there other points of contention?

tux3 8y ago
The recent Linux 5.0 GPL symbol incident (https://marc.info/?l=linux-kernel&m=154722999728768&w=2 https://marc.info/?l=linux-kernel&m=154722999728768&w=2) probably didn't help that perception.
- pierrebai 8y ago
  In the context of Linus stance that the kernel must never, ever break userland, I find it strange that he has not slapped the change of a function to GPL-only callers as incorrect and reverted it. You have a policy that you can't break users' programs, but borking their whole file-system is fine? Keep feeding end-users fears of open source petty feuds making people miserable. That works.
  - chaosite 8y ago
    Because... That's not userspace, that's kernelspace. Linux's policy on kernelspace API breakage is famously, "we do what we like, and if you're not in-kernel, then you get to keep both pieces when it breaks". If ZFS wanted to live in userspace (and get Linux's userspace API guarantees) then they could have made a FUSE filesystem instead.
    - DiabloD3 8y ago
      ZFS-FUSE existed before ZoL did. The reason they moved to their SPL-based solution is because FUSE didn't want to make the required changes to support high performance file systems. SPL now handles the guarantee to separate ZFS's userland components from Linux's constant internal kernelspace API churn. ZFS, internally, doesn't really know what a Linux is beyond a few little bits here and there.
      - kzrdude 8y ago
        That sounds like a missed opportunity, who doesn't want higher performance fuse filesystems?
        ianschenck 8y ago
        Glad you brought this up. It feels, at least to me, like FUSE is only for...hmm...gimmick or science-fare projects. Maybe something useful on your development machine. Indeed, at a previous employer, several problems were addressed using a handful of FUSE filesystems, quite elegantly. Of course the caveat was "this ain't prod, duh, it's FUSE". But this doesn't NEED to be the case. Tangentially, microkernels pop up here often, and arguable, moving some filesystems to user space makes sense in a related vein. I'll admit, I'm all talk and if it really mattered, pull requests are probably welcome.
      - Conan_Kudo 8y ago
        > ZFS-FUSE existed before ZoL did. The reason they moved to their SPL-based solution is because FUSE didn't want to make the required changes to support high performance file systems. These changes were made years later, but the developer of ZFS-FUSE disappeared, so they were never used. The FUSE v3 API further builds on that, and today, it's definitely possible to build a high-performance filesystem using FUSE. In fact, there are many examples of this in the wild: GlusterFS, Ceph, NTFS-3G, and so on. Today, there's absolutely _no_ reason ZFS would not sensibly work as high performance filesystem entirely from userspace. In fact, it still remains an open issue and a desirable target for ZoL: https://github.com/zfsonlinux/zfs/issues/8 https://github.com/zfsonlinux/zfs/issues/8
    - pierrebai 8y ago
      You're confirming what I just said. End-user dont'care about splitting hairs. Iwas using Linux in the mid-90's and that kind of stance is what turned me off. The sound card would brek, the networking would break, configuring the modem would be hell after each upgrade. The attitude that you must not break LibreOffice is not okey but breaking the file-system okay 'because it's a driver!' is just untenable. Making people's computer fail will turn users away. It's not just a Linux thing. When Windows breaks stuff, all hell break loose on the Internet. The problem with OSS, is that its maintainers have no direct, immediate monetary incentive to amend. The long-term loss of confidence is hard to measure, but it's real.
  - vetinari 8y ago
    Using internal kernel APIs is a pretty long way to being userland. Internal APIs are guaranteed to be broken, and for in-tree modules, the breakage is fixed by those, who break it. External modules have to do fixes themselves, thus motivating them to become in-tree.
- imhoguy 8y ago
  "v5.0 removes the ability from non-GPL modules to use the FPU or SIMD instructions" Any reason why?
  - anon1385 8y ago
    Well you can read the thread on the mailing list but to put it bluntly - because they wanted to stop ZoL from working. They view non-GPL kernel modules as a violation of the GPL. "My tolerance for ZFS is pretty non-existant" Greg Kroah-Hartman "please switch to FreeBSD instead of advocating to violate the copyright and licensing rule on my and others work." Christoph Hellwig
    - shawnz 8y ago
      > They view non-GPL kernel modules as a violation of the GPL. But then why allow them?
      - bluGill 8y ago
        users demand it. If the kernel devs pushed too hard legally a lot of users would switch to BSD (probably freebsd, but there are other good candidates). Linux is slightly better for desktop users, but if you cannot use your graphics hardware for legal reasons BSD will still work and is the lesser evil.
        shawnz 8y ago
        So basically NVIDIA gets a monopoly on the ability to release non-GPL linux kernel modules so that Linux can have a better reputation among desktop users (which is only a small fraction of Linux use in the first place)? I don't get it -- do they care more about what the users want, or about enforcing copyleft? If it's the latter, then they should be happy if those users who don't care about the GPL move to BSD. If it's the former then they should stop playing games and implement a fair policy for all non-GPL module authors.
        8y ago
dspillett 8y ago
BTRFS is being positioned as an alternative to ZFS (amongst others) without the licensing issues (and less rational concerns like the current/past politics of it all), so perhaps there is a "why do we X it when Y is close" with a bit of extra NIH syndrome mixed in?
- CrLf 8y ago
  Isn't btrfs also at risk? I was under the impression that it lost some steam in the recent past and was on its way to become the next Hurd.
  - vetinari 8y ago
    btrfs has a problem with it's image as being unreliable (some well deserved). Redhat obsoleted it, because they use kernel 3.10 in RHEL7 and they were doing nothing but backporting, without having any btrfs expertise in house anyway. Btrfs continues to be developed by Oracle, Suse, Facebook, Fujitsu and the rest of the usual suspects.
    - walrus01 8y ago
      RHEL is famous for using kernels that are ancient, even by the notoriously conservative and risk averse debian-stable standards. I can't even imagine the hassle of backporting stuff from much newer kernels into 3.10 to make btrfs work. If you want to use btrfs in production (not the best idea, IMHO, but orgs such as facebook do it) you absolutely need to be running a 4.9.x or better kernel.
      - snuxoll 8y ago
        Calling them ancient is a bit unfair, they regularly backport hardware support and select other features from newer kernels. Unlike other distributions, however, they have a stable kernel ABI for an entire release, so they can’t bring in changes that break white listed symbols.
  - ajross 8y ago

Interesting article. So is the “unfriendliness” of Linux kernel developers towards ZFS that is mentioned strictly due to licensing issues or are there other points of contention?

tux3 8y ago

The recent Linux 5.0 GPL symbol incident (https://marc.info/?l=linux-kernel&m=154722999728768&w=2 https://marc.info/?l=linux-kernel&m=154722999728768&w=2) probably didn't help that perception.

pierrebai 8y ago
In the context of Linus stance that the kernel must never, ever break userland, I find it strange that he has not slapped the change of a function to GPL-only callers as incorrect and reverted it. You have a policy that you can't break users' programs, but borking their whole file-system is fine? Keep feeding end-users fears of open source petty feuds making people miserable. That works.
- chaosite 8y ago
  Because... That's not userspace, that's kernelspace. Linux's policy on kernelspace API breakage is famously, "we do what we like, and if you're not in-kernel, then you get to keep both pieces when it breaks". If ZFS wanted to live in userspace (and get Linux's userspace API guarantees) then they could have made a FUSE filesystem instead.
  - DiabloD3 8y ago
    ZFS-FUSE existed before ZoL did. The reason they moved to their SPL-based solution is because FUSE didn't want to make the required changes to support high performance file systems. SPL now handles the guarantee to separate ZFS's userland components from Linux's constant internal kernelspace API churn. ZFS, internally, doesn't really know what a Linux is beyond a few little bits here and there.
    - kzrdude 8y ago
      That sounds like a missed opportunity, who doesn't want higher performance fuse filesystems?
      - ianschenck 8y ago
        Glad you brought this up. It feels, at least to me, like FUSE is only for...hmm...gimmick or science-fare projects. Maybe something useful on your development machine. Indeed, at a previous employer, several problems were addressed using a handful of FUSE filesystems, quite elegantly. Of course the caveat was "this ain't prod, duh, it's FUSE". But this doesn't NEED to be the case. Tangentially, microkernels pop up here often, and arguable, moving some filesystems to user space makes sense in a related vein. I'll admit, I'm all talk and if it really mattered, pull requests are probably welcome.
    - Conan_Kudo 8y ago
      > ZFS-FUSE existed before ZoL did. The reason they moved to their SPL-based solution is because FUSE didn't want to make the required changes to support high performance file systems. These changes were made years later, but the developer of ZFS-FUSE disappeared, so they were never used. The FUSE v3 API further builds on that, and today, it's definitely possible to build a high-performance filesystem using FUSE. In fact, there are many examples of this in the wild: GlusterFS, Ceph, NTFS-3G, and so on. Today, there's absolutely _no_ reason ZFS would not sensibly work as high performance filesystem entirely from userspace. In fact, it still remains an open issue and a desirable target for ZoL: https://github.com/zfsonlinux/zfs/issues/8 https://github.com/zfsonlinux/zfs/issues/8
  - pierrebai 8y ago
    You're confirming what I just said. End-user dont'care about splitting hairs. Iwas using Linux in the mid-90's and that kind of stance is what turned me off. The sound card would brek, the networking would break, configuring the modem would be hell after each upgrade. The attitude that you must not break LibreOffice is not okey but breaking the file-system okay 'because it's a driver!' is just untenable. Making people's computer fail will turn users away. It's not just a Linux thing. When Windows breaks stuff, all hell break loose on the Internet. The problem with OSS, is that its maintainers have no direct, immediate monetary incentive to amend. The long-term loss of confidence is hard to measure, but it's real.
- vetinari 8y ago
  Using internal kernel APIs is a pretty long way to being userland. Internal APIs are guaranteed to be broken, and for in-tree modules, the breakage is fixed by those, who break it. External modules have to do fixes themselves, thus motivating them to become in-tree.
imhoguy 8y ago
"v5.0 removes the ability from non-GPL modules to use the FPU or SIMD instructions" Any reason why?
- anon1385 8y ago
  Well you can read the thread on the mailing list but to put it bluntly - because they wanted to stop ZoL from working. They view non-GPL kernel modules as a violation of the GPL. "My tolerance for ZFS is pretty non-existant" Greg Kroah-Hartman "please switch to FreeBSD instead of advocating to violate the copyright and licensing rule on my and others work." Christoph Hellwig
  - shawnz 8y ago
    > They view non-GPL kernel modules as a violation of the GPL. But then why allow them?
    - bluGill 8y ago
      users demand it. If the kernel devs pushed too hard legally a lot of users would switch to BSD (probably freebsd, but there are other good candidates). Linux is slightly better for desktop users, but if you cannot use your graphics hardware for legal reasons BSD will still work and is the lesser evil.
      - shawnz 8y ago
        So basically NVIDIA gets a monopoly on the ability to release non-GPL linux kernel modules so that Linux can have a better reputation among desktop users (which is only a small fraction of Linux use in the first place)? I don't get it -- do they care more about what the users want, or about enforcing copyleft? If it's the latter, then they should be happy if those users who don't care about the GPL move to BSD. If it's the former then they should stop playing games and implement a fair policy for all non-GPL module authors.
        8y ago

dspillett 8y ago

BTRFS is being positioned as an alternative to ZFS (amongst others) without the licensing issues (and less rational concerns like the current/past politics of it all), so perhaps there is a "why do we X it when Y is close" with a bit of extra NIH syndrome mixed in?

CrLf 8y ago
Isn't btrfs also at risk? I was under the impression that it lost some steam in the recent past and was on its way to become the next Hurd.
- vetinari 8y ago
  btrfs has a problem with it's image as being unreliable (some well deserved). Redhat obsoleted it, because they use kernel 3.10 in RHEL7 and they were doing nothing but backporting, without having any btrfs expertise in house anyway. Btrfs continues to be developed by Oracle, Suse, Facebook, Fujitsu and the rest of the usual suspects.
  - walrus01 8y ago
    RHEL is famous for using kernels that are ancient, even by the notoriously conservative and risk averse debian-stable standards. I can't even imagine the hassle of backporting stuff from much newer kernels into 3.10 to make btrfs work. If you want to use btrfs in production (not the best idea, IMHO, but orgs such as facebook do it) you absolutely need to be running a 4.9.x or better kernel.
    - snuxoll 8y ago
      Calling them ancient is a bit unfair, they regularly backport hardware support and select other features from newer kernels. Unlike other distributions, however, they have a stable kernel ABI for an entire release, so they can’t bring in changes that break white listed symbols.
- ajross 8y ago