init,mm: fold late call to page_ext_init() to page_alloc_init_late()

When deferred initialization of struct pages is enabled, page_ext_init()
must be called after all the deferred initialization is done, but there is
no point to keep it a separate call from kernel_init_freeable() right
after page_alloc_init_late().

Fold the call to page_ext_init() into page_alloc_init_late() and localize
deferred_struct_pages variable.

Link: https://lkml.kernel.org/r/20230321170513.2401534-11-rppt@kernel.org
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/page_ext.h

@@ -29,8 +29,6 @@ struct page_ext_operations {
 	bool need_shared_flags;
 };
 
-extern bool deferred_struct_pages;
-
 #ifdef CONFIG_PAGE_EXTENSION
 
 /*

init/main.c

@@ -62,7 +62,6 @@
 #include <linux/rmap.h>
 #include <linux/mempolicy.h>
 #include <linux/key.h>
-#include <linux/page_ext.h>
 #include <linux/debug_locks.h>
 #include <linux/debugobjects.h>
 #include <linux/lockdep.h>
@@ -1565,9 +1564,6 @@ static noinline void __init kernel_init_freeable(void)
 
 	padata_init();
 	page_alloc_init_late();
-	/* Initialize page ext after all struct pages are initialized. */
-	if (deferred_struct_pages)
-		page_ext_init();
 
 	do_basic_setup();
 

mm/mm_init.c

@@ -225,7 +225,7 @@ static unsigned long nr_kernel_pages __initdata;
 static unsigned long nr_all_pages __initdata;
 static unsigned long dma_reserve __initdata;
 
-bool deferred_struct_pages __meminitdata;
+static bool deferred_struct_pages __meminitdata;
 
 static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
@@ -2358,6 +2358,10 @@ void __init page_alloc_init_late(void)
 
 	for_each_populated_zone(zone)
 		set_zone_contiguous(zone);
+
+	/* Initialize page ext after all struct pages are initialized. */
+	if (deferred_struct_pages)
+		page_ext_init();
 }
 
 #ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES