On Fri 20-05-16 08:41:09, Shi, Yang wrote:

On 5/20/2016 6:16 AM, Michal Hocko wrote:

quoted

On Thu 19-05-16 15:13:26, Yang Shi wrote:
[...]

quoted

diff --git a/init/main.c b/init/main.c
index b3c6e36..2075faf 100644
--- a/init/main.c
+++ b/init/main.c

@@ -606,7 +606,6 @@ asmlinkage __visible void __init start_kernel(void)
 		initrd_start = 0;
 	}
 #endif
-	page_ext_init();
 	debug_objects_mem_init();
 	kmemleak_init();
 	setup_per_cpu_pageset();

@@ -1004,6 +1003,8 @@ static noinline void __init kernel_init_freeable(void)
 	sched_init_smp();

 	page_alloc_init_late();
+	/* Initialize page ext after all struct pages are initializaed */
+	page_ext_init();

 	do_basic_setup();

I might be missing something but don't we have the same problem with
CONFIG_FLATMEM? page_ext_init_flatmem is called way earlier. Or
CONFIG_DEFERRED_STRUCT_PAGE_INIT is never enabled for CONFIG_FLATMEM?

Yes, CONFIG_DEFERRED_STRUCT_PAGE_INIT depends on MEMORY_HOTPLUG which
depends on SPARSEMEM. So, this config is not valid for FLATMEM at all.

Well
config MEMORY_HOTPLUG
        bool "Allow for memory hot-add"
	depends on SPARSEMEM || X86_64_ACPI_NUMA
	depends on ARCH_ENABLE_MEMORY_HOTPLUG

I wasn't really sure about X86_64_ACPI_NUMA dependency branch which
depends on X86_64 && NUMA && ACPI && PCI and that didn't sound like
SPARSEMEM only. If the FLATMEM shouldn't exist with
CONFIG_DEFERRED_STRUCT_PAGE_INIT can we make that explicit please?
-- 
Michal Hocko
SUSE Labs

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