Re: [v2 PATCH] mm: move page_ext_init after all struct pages are initialized

[Shi, Yang]

On 5/20/2016 6:16 AM, Michal Hocko wrote:
On Thu 19-05-16 15:13:26, Yang Shi wrote:
[...]
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.

Thanks,
Yang