@mihalicyn update: I did some tests and even if we're missing d24b8a547be1 ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay") in kernels >= 6.2 I'm able to use overlayfs on top of shiftfs (using the shiftfs mount-point as lower). I even tried the test case mentioned in the commit and I couldn't trigger any obvious failure. So I guess we don't need this patch anymore in kernels >= 6.2, I'll try to understand better why we don't need it...
@mihalicyn update: I did some tests and even if we're missing d24b8a547be1 ("UBUNTU: SAUCE: overlayfs: allow with shiftfs as underlay") in kernels >= 6.2 I'm able to use overlayfs on top of shiftfs (using the shiftfs mount-point as lower). I even tried the test case mentioned in the commit and I couldn't trigger any obvious failure. So I guess we don't need this patch anymore in kernels >= 6.2, I'll try to understand better why we don't need it...