Note I didn't see the intermediate comments (my previous comment was open and uncommitted in my browser), but I think my comments still stand. It makes the most sense to add/update the series for the latest kernels of each series, but IMHO it doesn't make sense to add series for older kernels. It is unlikely that sites starting with a brand new Lustre 2.16.0 install will be installing one of the older Ubuntu 20.04 5.4 kernels with it, but rather the latest Ubuntu kernel.
It would be good to understand the overarching approach here. Looking at recent additions to ldiskfs/, I see:
Jan 18th 2024: 20.04.5 5.15 support (not EOL until April 2025)
Jan 13th 2024: 20.04.5 5.11 support (not EOL until April 2025)
Jan 4th 2024: RHEL 9.3 support (not EOL until May 2027)
Nov 20th 2023: RHEL 8.9 support (EOL next month)
Oct 18th 2023: RHEL 9.2 support (not EOL until May 2027)
Aug 15th 2023: SUSE 15 SP3 support (EOL well before this commit)
This is driven by what is in use at customer sites, and what developers are willing to maintain. Shaun Tancheff has been doing a lot of the work to add newer ldiskfs series, but we have also recently been pruning old series (el7.8- and el8.3-) from the tree before the 2.16 release, since they are untested and unmaintained.
If the desired approach is to merge this to an earlier release (e.g., 2.15.next, or 2.16), that's fine by me too. I thought the model was to merge to master and then backport as-needed. Let me know which release would be most useful (we are on 2.15.4 now, so at least this series would be good, and we're considering moving to 2.16.* shortly after its release depending on the contents, so I'd ideally like that one as well).
Typically the addition of new kernel/distro support happens incrementally during the development cycle, but is largely driven by the needs of users/maintainers. IMHO, updating the 5.4.0 kernels in b2_15 would be OK, but adding e.g. el9.3 or Ubuntu 5.15 server kernel support there would be very dependent on how intrusive such patches are to the existing code. It is of course still possible to keep a local fork with b2_15 + older ldiskfs patch series as you've been doing so far.
One last thing – Ubuntu 22.04 is on Linux 6.5, and Ubuntu 24.04 is on Linux 6.8. I was under the impression that these two were not yet supported in ldiskfs patches. If that is not the case, please let me know!
I don't follow this closely, but AFAIK Ubuntu 22.04 was using kernel 5.15? Maybe that is a recent "advanced" kernel in preparation for 24.04, but I think most systems were running 5.15 over the past couple of years?
As for Ubuntu 24.04 and Linux 6.8, somebody has to do the work to port the kernel patch series to these new kernels, and I don't think anyone has had a desire/demand to take on that effort yet, since the servers are usually a bit isolated and maintained by the vendors, while users have a free-for-all with the clients (much moreso in cloud than on-prem). We are running only RHEL server kernels locally, so that is where our development efforts are focused. If you are running Ubuntu on the servers, then it makes sense to start with the latest ldiskfs kernel series and work forward from that.
Note I didn't see the intermediate comments (my previous comment was open and uncommitted in my browser), but I think my comments still stand. It makes the most sense to add/update the series for the latest kernels of each series, but IMHO it doesn't make sense to add series for older kernels. It is unlikely that sites starting with a brand new Lustre 2.16.0 install will be installing one of the older Ubuntu 20.04 5.4 kernels with it, but rather the latest Ubuntu kernel.
This is driven by what is in use at customer sites, and what developers are willing to maintain. Shaun Tancheff has been doing a lot of the work to add newer ldiskfs series, but we have also recently been pruning old series (el7.8- and el8.3-) from the tree before the 2.16 release, since they are untested and unmaintained.
Typically the addition of new kernel/distro support happens incrementally during the development cycle, but is largely driven by the needs of users/maintainers. IMHO, updating the 5.4.0 kernels in b2_15 would be OK, but adding e.g. el9.3 or Ubuntu 5.15 server kernel support there would be very dependent on how intrusive such patches are to the existing code. It is of course still possible to keep a local fork with b2_15 + older ldiskfs patch series as you've been doing so far.
I don't follow this closely, but AFAIK Ubuntu 22.04 was using kernel 5.15? Maybe that is a recent "advanced" kernel in preparation for 24.04, but I think most systems were running 5.15 over the past couple of years?
As for Ubuntu 24.04 and Linux 6.8, somebody has to do the work to port the kernel patch series to these new kernels, and I don't think anyone has had a desire/demand to take on that effort yet, since the servers are usually a bit isolated and maintained by the vendors, while users have a free-for-all with the clients (much moreso in cloud than on-prem). We are running only RHEL server kernels locally, so that is where our development efforts are focused. If you are running Ubuntu on the servers, then it makes sense to start with the latest ldiskfs kernel series and work forward from that.