Re: [v2 2/2] device-dax: "Hotremove" persistent memory that is used like normal RAM

> > +static int > > +offline_memblock_cb(struct memory_block *mem, void *arg) > > Function name suggests that you are actually trying to offline memory > here. Maybe check_memblocks_offline_cb(), just like we have in > mm/memory_hotplug.c.

> > + lock_device_hotplug(); > > + rc = walk_memory_range(start_pfn, end_pfn, dev, offline_memblock_cb); > > + unlock_device_hotplug(); > > + > > + /* > > + * If admin has not offlined memory beforehand, we cannot hotremove dax. > > + * Unfortunately, because unbind will still succeed there is no way for > > + * user to hotremove dax after this. > > + */ > > + if (rc) > > + return rc; > > Can't it happen that there is a race between you checking if memory is > offline and an admin onlining memory again? maybe pull the > remove_memory() into the locked region, using __remove_memory() instead. I think the race is ok. The admin gets to keep the pieces of allowing racing updates to the state and the kernel will keep the range active until the next reboot.