Dear Stable Maintainers,
When a bugfix is backported to stable kernels, should we be backporting the associated selftest(s)?
eg.
9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes") was backported to stable, but the selftest was not: 5777d1871bf6 ("selftests: net: add test for variable PMTU in broadcast routes")
Does stable policy say whether it should be?
It does not fix a bug, per se, but it does enable those of us running stable kernel tests to more thoroughly test stable RCs.
Should mainline authors be encouraged to mark related tests for backporting?
Cheers,
Brett
On Sat, Aug 23, 2025 at 03:05:46PM +0200, Brett Sheffield wrote:
Dear Stable Maintainers,
When a bugfix is backported to stable kernels, should we be backporting the associated selftest(s)?
If you want to, sure!
eg.
9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes") was backported to stable, but the selftest was not: 5777d1871bf6 ("selftests: net: add test for variable PMTU in broadcast routes")
Does stable policy say whether it should be?
It's up to the subsystem/maintainer/developer/whomever if they wish to do that or not. Some subsystems want to do this, others don't, others don't care.
It does not fix a bug, per se, but it does enable those of us running stable kernel tests to more thoroughly test stable RCs.
Note that you should always be running the latest selftests for older kernels, and I think that's what many of the CI systems are already doing, so maybe that's why you don't notice stuff like this?
That's the only "rule" we have, all new selftests need to work properly for older kernels.
Should mainline authors be encouraged to mark related tests for backporting?
Again, it's up to them if they want to or not. I will point out mptcp as one subsystem that does mark selftests to backport, and provides backports for when they do not apply correctly.
hope this helps,
greg k-h
On 2025-08-23 15:51, Greg KH wrote:
On Sat, Aug 23, 2025 at 03:05:46PM +0200, Brett Sheffield wrote:
Dear Stable Maintainers,
When a bugfix is backported to stable kernels, should we be backporting the associated selftest(s)?
If you want to, sure!
eg.
9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes") was backported to stable, but the selftest was not: 5777d1871bf6 ("selftests: net: add test for variable PMTU in broadcast routes")
Does stable policy say whether it should be?
It's up to the subsystem/maintainer/developer/whomever if they wish to do that or not. Some subsystems want to do this, others don't, others don't care.
It does not fix a bug, per se, but it does enable those of us running stable kernel tests to more thoroughly test stable RCs.
Note that you should always be running the latest selftests for older kernels, and I think that's what many of the CI systems are already doing, so maybe that's why you don't notice stuff like this?
That's the only "rule" we have, all new selftests need to work properly for older kernels.
Should mainline authors be encouraged to mark related tests for backporting?
Again, it's up to them if they want to or not. I will point out mptcp as one subsystem that does mark selftests to backport, and provides backports for when they do not apply correctly.
hope this helps,
Thanks Greg. It does.
Brett
linux-stable-mirror@lists.linaro.org
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Brett A C Sheffield -
Brett Sheffield -
Greg KH