Erhard Furtner [off-list ref] writes:

Greetings!

Basically bcachefs works on ppc32 but I get stack overflows like this one rather easy:

[...]
do_IRQ: stack overflow: 1072
CPU: 1 PID: 2114 Comm: bash Not tainted 6.10.5-gentoo-PMacG4 #1
Hardware name: PowerMac3,6 7455 0x80010303 PowerMac
Call Trace:
[effe3fc0] [c0785664] dump_stack_lvl+0x70/0x8c (unreliable)
[effe3fe0] [c00081fc] __do_irq+0x28/0x80
[effe3ff0] [c000873c] __do_IRQ+0x7c/0x84
[c8aec430] [c8aec610] 0xc8aec610

   ^ 
That's your lowest frame on the process stack. It should actually extend
down to c8aec000, so you had a little bit of space left.

CONFIG_DEBUG_STACKOVERFLOW warns when you have less than 1/4 of the stack
free. You could try turning it off and see if the system survives.

The other thing to try would be increasing the THREAD_SHIFT to 14.

cheers