Slow RAID6 with > 16 drives

[andrei-marinache]

There is an issue in the 5.4.229 kernel with more than 16 drives in a RAID array:
Reported here: https://lore.kernel.org/linux-raid/CAFDAVznKiKC7YrCTJ4oj6NimXrhnY-=PUnJhFopw6Ur5LvOCjg@mail.gmail.com/
Patch is here: https://lore.kernel.org/linux-raid/CAPhsuW7R=8XyU5wU1-NT-Eo=Hir7gV_b7+_MB+bUFx3bEecbDw@mail.gmail.com/