Bcachefs goes DKMS after Torvalds' kernel banishment
(2025/09/25)
- Reference: 1758797991
- News link: https://www.theregister.co.uk/2025/09/25/bcachefs_dkms_modules/
- Source link:
The bcachefs file system, now "externally maintained" outside the Linux kernel codebase, offers packages of its first version to be loadable on the fly.
The development of bcachefs has been officially jettisoned from that of the Linux kernel itself. At present, the work-in-progress kernel 6.17 still contains bcachefs code, but unmodified from the 6.16 release. In response, the project has published its [1]first set of packages of a version that can be dynamically loaded as a DKMS module, as promised a couple of weeks ago in [2]an email from project lead Kent Overstreet.
It's available as an APT repository, which for the time being limits it to the Ubuntu and Debian family of distros.
[3]
This is the code that would have been the newer revision inside kernel 6.17 – but [4]Linus Torvalds banished it last month. This means that if you test on the current release candidate of kernel 6.17, there are two different versions of bcachefs available: the built-in one, which is the same code as in kernel 6.16, and alternatively the newer version available in the dynamically loaded DKMS code.
[5]
[6]
Linux benchmarking site Phoronix recently ran a [7]set of performance tests comparing all the built-in file systems in 6.17, and bcachefs did not fare well. We counted 16 tests across five pages of graphs, and bcachefs was the slowest or next-to-last in all of them. Phoronix [8]repeated the tests with the new DKMS version, and it does comparatively better. In multiple tests, the new version is about twice as fast, and ranks in the middle of the pack.
So moving to DKMS has not directly harmed it, and the new version is performing considerably better. There's still room for improvement, but this young and not yet highly optimized code is progressing nicely.
openSUSE changes position
Since we [9]reported that openSUSE was dropping bcachefs support , Overstreet has talked to the kernel maintainers there too. It looks like the company's hard-line stance has been toned down. For now, there is a [10]patch to the openSUSE kernel that prints a warning message:
bcachefs will be removed from the SUSE kernel in 6.18.
This kernel may be missing critical bcachefs fixes, due to its mainline transition to "externally maintained" status.
See also: [11]https://bugzilla.opensuse.org/show_bug.cgi?id=1248109
[12]I'm out, says OpenSUSE: We're dropping bcachefs support from next kernel version
[13]Linus Torvalds hints bcachefs may get dropped from the Linux kernel
[14]SystemRescue 12 lands with added bcachefs support
[15]Public developer spats put bcachefs at risk in Linux
The comments in the [16]openSUSE bugzilla entry listed there show that the change is under consideration. After Overstreet [17]chimed in on the [18]openSUSE Factory mailing list , it now looks like openSUSE Tumbleweed won't remove bcachefs when kernel 6.17 ships. Developer Jiří Slabý [19]said :
After discussing with Kent, I am for disabling only in 6.18. They should be ready having DKMS, someone could have a KMP packaged at that point.
This is good news for Tumbleweed users, as well as for bcachefs itself.
There may be trouble ahead…
Not all the news trickling out is good, though. Long-time kernel developer Christoph Hellwig submitted a [20]patch to linux-next that would remove support for the [21]write_cache_pages API from kernel 6.18 and later.
The proposed change is that with the removal of bcachefs, nothing uses it any more. NTFS3 is [22]now built in and OpenZFS [23]can't be included and never will, unless Oracle decides to re-license it – which is unlikely.
[24]
Hellwig has occasionally featured on The Register for a decade or more, since he [25]accused VMware of ripping off Linux kernel source code in 2015. In a [26]2016 follow-up , we referred to him as an "ace kernel developer."
It could be said, though, he's no diplomat. More recently, [27]The Reg reported that he likened mixing Rust and C in the Linux kernel to cancer.
It does look like removing this API would make life very much more difficult for file systems whose code does not form part of the kernel source code. Even if no built-in code uses it, we'd prefer not to see OpenZFS and bcachefs crippled by its removal.
Bootnote
When it looked like bcachefs would be excommunicated, we [28]reported on criticism by Meta kernel developer [29]Josef Bacik , who praised Btrfs and whose criticisms of Overstreet we felt were among the more savage. The personality clashes to which we referred were not only those between Torvalds and Overstreet.
Just a couple of weeks later, Bacik [30]announced on Mastodon that he was leaving Meta and stopping his kernel development efforts. Instead, he's going to work for [31]cash bonfire owners Anthropic . ®
Get our [32]Tech Resources
[1] https://apt.bcachefs.org/
[2] https://lore.kernel.org/linux-bcachefs/yokpt2d2g2lluyomtqrdvmkl3amv3kgnipmenobkpgx537kay7@xgcgjviv3n7x/T/#u
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://www.theregister.com/2025/08/15/sad_end_of_bcachefs/
[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[7] https://www.phoronix.com/review/linux-617-filesystems
[8] https://www.phoronix.com/review/bcachefs-617-dkms
[9] https://www.theregister.com/2025/09/12/opensuse_to_drop_bcachefs_support/
[10] https://github.com/openSUSE/kernel-source/blob/stable/patches.suse/bcachefs-print-message-at-mount-time-regarding-immin.patch
[11] https://bugzilla.opensuse.org/show_bug.cgi?id=1248109
[12] https://www.theregister.com/2025/09/12/opensuse_to_drop_bcachefs_support/
[13] https://www.theregister.com/2025/07/01/bcachefs_may_get_dropped/
[14] https://www.theregister.com/2025/03/20/systemrescue_12_bcachefs/
[15] https://www.theregister.com/2024/11/22/bcachefs_linux/
[16] https://bugzilla.suse.com/show_bug.cgi?id=1248109
[17] https://lists.opensuse.org/archives/list/factory@lists.opensuse.org/message/ALQHDZ6YXNKWLFMPCJOSNGFMBC5SFXRC/
[18] https://lists.opensuse.org/archives/list/factory@lists.opensuse.org/
[19] https://bugzilla.suse.com/show_bug.cgi?id=1248109#c13
[20] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=9c5518f1bacf98b20c3ad0fa5873b4da92122ced
[21] https://static.lwn.net/kerneldoc/core-api/mm-api.html#c.write_cache_pages
[22] https://www.theregister.com/2021/10/13/how_ntfs_finally_made_it/
[23] https://www.theregister.com/2020/01/13/zfs_linux/
[24] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[25] https://www.theregister.com/2015/03/05/vmware_sued_for_gpl_violation_by_linux_kernel_developer/
[26] https://www.theregister.com/2016/03/01/vmwares_gpl_violation_case_rolls_into_german_court/
[27] https://www.theregister.com/2025/02/05/mixing_rust_and_c_linux/
[28] https://www.theregister.com/2025/08/15/sad_end_of_bcachefs/
[29] https://github.com/josefbacik
[30] https://hachyderm.io/@josefbacik/115111769723183990
[31] https://www.theregister.com/2025/09/03/anthropic_funding/
[32] https://whitepapers.theregister.com/
The development of bcachefs has been officially jettisoned from that of the Linux kernel itself. At present, the work-in-progress kernel 6.17 still contains bcachefs code, but unmodified from the 6.16 release. In response, the project has published its [1]first set of packages of a version that can be dynamically loaded as a DKMS module, as promised a couple of weeks ago in [2]an email from project lead Kent Overstreet.
It's available as an APT repository, which for the time being limits it to the Ubuntu and Debian family of distros.
[3]
This is the code that would have been the newer revision inside kernel 6.17 – but [4]Linus Torvalds banished it last month. This means that if you test on the current release candidate of kernel 6.17, there are two different versions of bcachefs available: the built-in one, which is the same code as in kernel 6.16, and alternatively the newer version available in the dynamically loaded DKMS code.
[5]
[6]
Linux benchmarking site Phoronix recently ran a [7]set of performance tests comparing all the built-in file systems in 6.17, and bcachefs did not fare well. We counted 16 tests across five pages of graphs, and bcachefs was the slowest or next-to-last in all of them. Phoronix [8]repeated the tests with the new DKMS version, and it does comparatively better. In multiple tests, the new version is about twice as fast, and ranks in the middle of the pack.
So moving to DKMS has not directly harmed it, and the new version is performing considerably better. There's still room for improvement, but this young and not yet highly optimized code is progressing nicely.
openSUSE changes position
Since we [9]reported that openSUSE was dropping bcachefs support , Overstreet has talked to the kernel maintainers there too. It looks like the company's hard-line stance has been toned down. For now, there is a [10]patch to the openSUSE kernel that prints a warning message:
bcachefs will be removed from the SUSE kernel in 6.18.
This kernel may be missing critical bcachefs fixes, due to its mainline transition to "externally maintained" status.
See also: [11]https://bugzilla.opensuse.org/show_bug.cgi?id=1248109
[12]I'm out, says OpenSUSE: We're dropping bcachefs support from next kernel version
[13]Linus Torvalds hints bcachefs may get dropped from the Linux kernel
[14]SystemRescue 12 lands with added bcachefs support
[15]Public developer spats put bcachefs at risk in Linux
The comments in the [16]openSUSE bugzilla entry listed there show that the change is under consideration. After Overstreet [17]chimed in on the [18]openSUSE Factory mailing list , it now looks like openSUSE Tumbleweed won't remove bcachefs when kernel 6.17 ships. Developer Jiří Slabý [19]said :
After discussing with Kent, I am for disabling only in 6.18. They should be ready having DKMS, someone could have a KMP packaged at that point.
This is good news for Tumbleweed users, as well as for bcachefs itself.
There may be trouble ahead…
Not all the news trickling out is good, though. Long-time kernel developer Christoph Hellwig submitted a [20]patch to linux-next that would remove support for the [21]write_cache_pages API from kernel 6.18 and later.
The proposed change is that with the removal of bcachefs, nothing uses it any more. NTFS3 is [22]now built in and OpenZFS [23]can't be included and never will, unless Oracle decides to re-license it – which is unlikely.
[24]
Hellwig has occasionally featured on The Register for a decade or more, since he [25]accused VMware of ripping off Linux kernel source code in 2015. In a [26]2016 follow-up , we referred to him as an "ace kernel developer."
It could be said, though, he's no diplomat. More recently, [27]The Reg reported that he likened mixing Rust and C in the Linux kernel to cancer.
It does look like removing this API would make life very much more difficult for file systems whose code does not form part of the kernel source code. Even if no built-in code uses it, we'd prefer not to see OpenZFS and bcachefs crippled by its removal.
Bootnote
When it looked like bcachefs would be excommunicated, we [28]reported on criticism by Meta kernel developer [29]Josef Bacik , who praised Btrfs and whose criticisms of Overstreet we felt were among the more savage. The personality clashes to which we referred were not only those between Torvalds and Overstreet.
Just a couple of weeks later, Bacik [30]announced on Mastodon that he was leaving Meta and stopping his kernel development efforts. Instead, he's going to work for [31]cash bonfire owners Anthropic . ®
Get our [32]Tech Resources
[1] https://apt.bcachefs.org/
[2] https://lore.kernel.org/linux-bcachefs/yokpt2d2g2lluyomtqrdvmkl3amv3kgnipmenobkpgx537kay7@xgcgjviv3n7x/T/#u
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://www.theregister.com/2025/08/15/sad_end_of_bcachefs/
[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[7] https://www.phoronix.com/review/linux-617-filesystems
[8] https://www.phoronix.com/review/bcachefs-617-dkms
[9] https://www.theregister.com/2025/09/12/opensuse_to_drop_bcachefs_support/
[10] https://github.com/openSUSE/kernel-source/blob/stable/patches.suse/bcachefs-print-message-at-mount-time-regarding-immin.patch
[11] https://bugzilla.opensuse.org/show_bug.cgi?id=1248109
[12] https://www.theregister.com/2025/09/12/opensuse_to_drop_bcachefs_support/
[13] https://www.theregister.com/2025/07/01/bcachefs_may_get_dropped/
[14] https://www.theregister.com/2025/03/20/systemrescue_12_bcachefs/
[15] https://www.theregister.com/2024/11/22/bcachefs_linux/
[16] https://bugzilla.suse.com/show_bug.cgi?id=1248109
[17] https://lists.opensuse.org/archives/list/factory@lists.opensuse.org/message/ALQHDZ6YXNKWLFMPCJOSNGFMBC5SFXRC/
[18] https://lists.opensuse.org/archives/list/factory@lists.opensuse.org/
[19] https://bugzilla.suse.com/show_bug.cgi?id=1248109#c13
[20] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=9c5518f1bacf98b20c3ad0fa5873b4da92122ced
[21] https://static.lwn.net/kerneldoc/core-api/mm-api.html#c.write_cache_pages
[22] https://www.theregister.com/2021/10/13/how_ntfs_finally_made_it/
[23] https://www.theregister.com/2020/01/13/zfs_linux/
[24] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aNVnCPiujF4Kvpz4voBRnAAAAkU&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[25] https://www.theregister.com/2015/03/05/vmware_sued_for_gpl_violation_by_linux_kernel_developer/
[26] https://www.theregister.com/2016/03/01/vmwares_gpl_violation_case_rolls_into_german_court/
[27] https://www.theregister.com/2025/02/05/mixing_rust_and_c_linux/
[28] https://www.theregister.com/2025/08/15/sad_end_of_bcachefs/
[29] https://github.com/josefbacik
[30] https://hachyderm.io/@josefbacik/115111769723183990
[31] https://www.theregister.com/2025/09/03/anthropic_funding/
[32] https://whitepapers.theregister.com/
zimzam
It's not going to happen. There've always been the likes of Hellwig in the kernel. ReiserFS was only removed from the kernel last year. They never remove stuff just to make things tidy or pretty.
Mockup1974
bcachefs, openzfs, .... i've never had any issue with btrfs and dont see a reason to change my file system
that one in the corner
I've never had any issues using Linux with ext4 and don't see any reason to change my file system.
Then again, I've never actually tried running anything else. Even my Apache/Subversion/Bugzilla Linux VMs are using ext4, it was the default.
The file, VM host & database server boxes, OTOH, all run the actual real hard drives using ZFS on FreeBSD.
So maybe my anecdote isn't actually of any relevance to anyone else.
Liam Proven
> i've never had any issue with btrfs and dont see a reason to change my file system
Tell you what. Want to see it fail?
FFS don't do this to your live OS. Bung openSUSE or Fedora in a VM. Give it a modest sized virtual disk, say 20GB or something.
Update it, make it happy. Doesn't matter if it has a GUI or not.
Now, make a nice big file.
dd if=/dev/urandom of=1GB.bin bs=64M count=16 iflag=fullblock
Something like that. (Grabbed off Stack Exchange.)
Now copy it.
Repeat until the disk is full.
Now, reboot. Try to write a file.
Bye-bye root partition. Bye-bye OS. `btrfs repair` will not help you.
seven of five
impatient, are we? Just use it on a real server (think SAP HANA [1]) and wait, it will fubar the machine soon enough...
[1] yes, btrfs is (now) verboten for HANA. Guess why...
btrfs after filling disk
David Newall
As I recall, you fix it by adding more space. Only then can you remove some files, and then remove the space you added. A full Btrfs induces panic (in the sysop, not the kernel.) Mind you, I didn't reboot. Does that truly make it worse?
As I recall, that's why I swapped Btrfs with ZFS, which just works. It also has online dedup, which really rocks.
If write_cache_pages is necessary for ZFS to work, or give good performance, as implied in the article, then removing it be a wonderful result for BSD.
While I personally don't give a beep about what filesystems are included in the kernel, I feel that at least some of the kernel developers have lost the plot on what is important. The kernel itself is not what is important, it's what it enables that is... So if removing something from the kernel just to make it prettier breaks / makes it slower / harder for other non kernel stuff to do things they are in the wrong (most of the time, there may be legitimate reasons for that as well sometimes). For a while it felt like we were moving away from the playground attitudes and to something more adult, but it feels like we are back in the safety of thee playground again.
icon because pirates are definitely a part of the playground.