Comment 0 for bug 1976248

[Impact]

 * A change of kernel symbol license allows to drop a PPC specific workaround in zfs-dkms to use the regular (better) code paths.

 * See details in:

https://git.launchpad.net/ubuntu/+source/zfs-linux/tree/debian/patches/4900-ppc-get-user-workaround.patch

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1009242

[Test Plan]

 * linux: apply https://github.com/torvalds/linux/commit/d9e5c3e9e75162f845880535957b7fd0b4637d23

 * zfs-dkms: revert https://git.launchpad.net/ubuntu/+source/zfs-linux/tree/debian/patches/4900-ppc-get-user-workaround.patch

 * Build on kernel with zfs module on ppc

 * Ensure that zfs.ko successfully loads and works

 * Test that root on zfs installations work on ppc (however, Ubuntu currently doesn't provide an installation method to achieve this, so this bit of verification might be hard to complete)

[Where problems could occur]

 * The PPC workaround patch is known to be buggy, and the new arch-independent codepath may now use optimized codepaths inside kernel resulting in a different behavior as observed by user-space (operation successful, EFAULT not returned) matching the behavior of all other architectures.