Re: [PATCH v2 06/14] init: fold build_all_zonelists() and page_alloc_init_cpuhp() to mm_init()

[Vlastimil Babka]

On 3/22/23 21:26, Mike Rapoport wrote:
> On Wed, Mar 22, 2023 at 05:10:10PM +0100, Vlastimil Babka wrote:
>> On 3/21/23 18:05, Mike Rapoport wrote:
>> > From: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
>> > 
>> > Both build_all_zonelists() and page_alloc_init_cpuhp() must be called
>> > after SMP setup is complete but before the page allocator is set up.
>> > 
>> > Still, they both are a part of memory management initialization, so move
>> > them to mm_init().
>> 
>> Well, logic grouping is one thing, but not breaking a functional order is
>> more important. So this moves both calls to happen later than theyw ere. I
>> guess it could only matter for page_alloc_init_cpuhp() in case cpu hotplugs
>> would be processed in some of the calls we "skipped" over by moving this
>> later. And one of them is setup_arch()... so are we sure no arch does some
>> cpu hotplug for non-boot cpus there?
> 
> mm_init() happens after the point build_all_zonelists() and
> page_alloc_init_cpuhp() were originally, so they are essentially moved
> later in the init sequence and in either case called after setup_arch().

Right, I looked at a wrong place in start_kernel() for the original location
of the calls, sorry for the noise.

> We skip the code below and it does not do neither cpu hotplug nor
> non-memblock allocations.
> 
> 	jump_label_init();
> 	parse_early_param();
> 	after_dashes = parse_args("Booting kernel",
> 				  static_command_line, __start___param,
> 				  __stop___param - __start___param,
> 				  -1, -1, NULL, &unknown_bootoption);
> 	print_unknown_bootoptions();
> 	if (!IS_ERR_OR_NULL(after_dashes))
> 		parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
> 			   NULL, set_init_arg);
> 	if (extra_init_args)
> 		parse_args("Setting extra init args", extra_init_args,
> 			   NULL, 0, -1, -1, NULL, set_init_arg);
> 
> 	/* Architectural and non-timekeeping rng init, before allocator init */
> 	random_init_early(command_line);
> 
> 	/*
> 	 * These use large bootmem allocations and must precede
> 	 * kmem_cache_init()
> 	 */
> 	setup_log_buf(0);
> 	vfs_caches_init_early();
> 	sort_main_extable();
> 	trap_init();
> 

Yeah, that looks safe.

>> > Signed-off-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
>> > Acked-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>