Details
-
Bug
-
Resolution: Fixed
-
Blocker
-
Lustre 2.10.0
-
None
-
3
-
9223372036854775807
Description
Now that kmods are being produced, they need to be limited to the kernel of the RHEL minor release they were created for.
This is because RHEL kernels have a kabi "whitelist". That means, that only a subset of kernel interfaces are guaranteed to be stable by RHEL's kabi and it's only those interfaces that are put into a kernel's list of "kernel(...) = ..." Provides: and a kmod's Requires:. This means that a kmod produced for RHEL 7.3 will look compatible with a RHEL 7.4 kernel (because the whitelisted kabi will not have changed across those releases) even though it is not because the Lustre kmods use interfaces that are not on the whitelist and can change from one minor release to another, even though the whitelisted kabi has not changed.
While Red Hat guarantees that these non-whitelisted interfaces will not change within a minor release (i.e. 7.3 to 7.4) there is no such guarantee across minor releases and in practice they probably almost always change across minor releases so a kmod using non-whitelisted interfaces needs to limit itself to the kernel provided in a RHEL minor release.
For a kmod produced on a RHEL 7.3 kernel that means adding a Requires: kernel >= 3.10.0-514, kernel <= 3.10.0-514 to the kmod RPM.
If this is not done, the kmod will install on to a RHEL 7.4 machine, which has an incompatible kernel by default and a compatible kernel (kernel-3.10.0-514*) will not be installed even if it's available in a Yum repo, even though it should be.
