long-term stable backports of NFSD patches

[Chuck Lever <chuck.lever@oracle.com>]

It's apparent that a number of distributions and their customers
remain on long-term stable kernels. We are aware of the scalability
problems and other bugs in NFSD in kernels between v5.4 and v6.1.

To address the filecache and other scalability problems in those
kernels, I'm preparing backported patches of NFSD fixes for several
popular LTS kernels. These backports are destined for the official
LTS kernel branches so that distributions can easily integrate them
into their products.

Once this effort is complete, Greg and Sasha will continue to be
responsible for backporting NFSD-related fixes from upstream into
the LTS kernels.

---

I've pushed the NFSD backports to branches in this repo:

https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git

If you are able, I encourage you to pull these, review them or try
them out, and report any issues or successes. I'm currently using
the NFS workflows in kdevops as the testing platform, but am
planning to include other tests.


LTS v5.10.y

The bulk of this work is now in v5.10.220. There were a handful of
missing forward fixes discovered that I've now submitted to stable@
for inclusion in an upcoming release of 5.10.y.

You can find this series in the "nfsd-5.10.y" branch in the above
repo.


Out-of-kernel follow-up work

Amir Goldstein made these review requests:

- Adjust the LTP test fanotify09 to update the comment with the
appropriate 5.15.y version
- Update fanotify_init(2) "FAN_REPORT_TARGET_FID (since Linux 5.17)"
- Update fanotify_mark(2) "FAN_MARK_EVICTABLE (since Linux 5.19)"
- Update fanotify_mark(2) "FAN_RENAME (since Linux 5.17)"
- Update fanotify_mark(2) "FAN_FS_ERROR (since Linux 5.16 and 5.15.???)"
- Update fanotify_mark(2) "FAN_MARK_IGNORE (since Linux 6.0)"

I plan to provide these updates once the NFSD filecache backports
have been completed.


-- 
Chuck Lever