alinux: introduce deferred_meminit boot parameter

fix #27418285

We introduce a boot parametter 'deferred_meminit' for defer
page init feature. Default it is disabled, and we can pass
'deferred_meminit' to enable it.
Signed-off-by: Nchenxiangzuo <cxz18821786681@linux.alibaba.com>
Reviewed-by: NXu Yu <xuyu@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NShile Zhang <shile.zhang@linux.alibaba.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -818,6 +818,11 @@
 			Defaults to the default architecture's huge page size
 			if not specified.
 
+	deferred_meminit
+			[KNL] When CONFIG_DEFERRED_STRUCT_PAGE_INIT is set,
+			this parameter enables the deferred page struct
+			initialization at boot time. In default, it is disabled.
+
 	deferred_probe_timeout=
 			[KNL] Debugging option to set a timeout in seconds for
 			deferred probe to give up waiting on dependencies to

mm/page_alloc.c

@@ -296,6 +296,7 @@ EXPORT_SYMBOL(nr_online_nodes);
 int page_group_by_mobility_disabled __read_mostly;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+static bool deferred_mem_init_enabled __meminitdata;
 /*
  * During boot we initialize deferred pages on-demand, as needed, but once
  * page_alloc_init_late() has finished, the deferred pages are all initialized,
@@ -341,6 +342,9 @@ static inline bool update_defer_init(pg_data_t *pgdat,
 				unsigned long pfn, unsigned long zone_end,
 				unsigned long *nr_initialised)
 {
+	if (!deferred_mem_init_enabled)
+		return true;
+
 	/* Always populate low zones for address-constrained allocations */
 	if (zone_end < pgdat_end_pfn(pgdat))
 		return true;
@@ -353,6 +357,17 @@ static inline bool update_defer_init(pg_data_t *pgdat,
 
 	return true;
 }
+
+static int __init setup_deferred_mem_init(char *str)
+{
+	if (!str)
+		deferred_mem_init_enabled = true;
+
+	return 0;
+}
+
+early_param("deferred_meminit", setup_deferred_mem_init);
+
 #else
 #define kasan_free_nondeferred_pages(p, o)	kasan_free_pages(p, o)