I have a bit of a grievance to file. :) I'm seeing "Cannot create slab..." panic()s coming from kmem_cache_open() when trying to create memory cgroups on a Fedora system running 5.2-rc's. The panic()s happen when failing to create memcg-specific slabs because the memcg code passes through the root_cache->flags, which can include SLAB_PANIC. I haven't tracked down the root cause yet, or where this behavior started. But, the end-user experience is that systemd tries to create a cgroup and ends up with a kernel panic. That's rather sad, especially for the poor sod that's trying to debug it. Should memcg_create_kmem_cache() be, perhaps filtering out SLAB_PANIC from root_cache->flags, for instance? That might make the system a bit less likely to turn into a doorstop if and when something goes mildly wrong. I've hacked out the panic()s and the system actually seems to boot OK. BTW, this particular system has some persistent memory in it. I suspect there's something wrong where the slab code is trying to create slabs for pmem-only nodes. But,
