mm/page_alloc: Use cmdline to disable "place pages to tail"

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4EG0R
CVE: NA

-----------------------------------------------

Add cmdline to disable "place pages to tail" when online memory.
Signed-off-by: NPeng Liu <liupeng256@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -1254,6 +1254,15 @@
 			Warning: use of this parameter will taint the kernel
 			and may cause unknown problems.
 
+	fpi_to_tail=off
+			[KNL] Place pages to front in __free_pages_core().
+			This kernel start-up parameter can be just used as
+			"fpi_to_tail=off", which means memory is online to
+			the front of freelist. Dynamic open is not supportted,
+			in other words, "fpi_to_tail=on" will be ignored by
+			kernel. This is just an ugly solution for circumvention
+			for some latent bugs revealed by "place pages to tail".
+
 	ftrace=[tracer]
 			[FTRACE] will set and start the specified tracer
 			as early as possible in order to facilitate early

mm/page_alloc.c

@@ -102,6 +102,17 @@ typedef int __bitwise fpi_t;
  */
 #define FPI_TO_TAIL		((__force fpi_t)BIT(1))
 
+static bool fpi_to_tail = true;
+
+static int __init early_fpi_to_tail(char *str)
+{
+	if (str && !strcmp(str, "off"))
+		fpi_to_tail = false;
+
+	return 0;
+}
+early_param("fpi_to_tail", early_fpi_to_tail);
+
 /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
 static DEFINE_MUTEX(pcp_batch_high_lock);
 #define MIN_PERCPU_PAGELIST_FRACTION	(8)
@@ -1342,12 +1353,16 @@ void __free_pages_core(struct page *page, unsigned int order)
 	}
 	__ClearPageReserved(p);
 	set_page_count(p, 0);
-
-	/*
-	 * Bypass PCP and place fresh pages right to the tail, primarily
-	 * relevant for memory onlining.
-	 */
-	__free_pages_ok(page, order, FPI_TO_TAIL);
+	if (fpi_to_tail) {
+		/*
+		 * Bypass PCP and place fresh pages right to the tail, primarily
+		 * relevant for memory onlining.
+		 */
+		__free_pages_ok(page, order, FPI_TO_TAIL);
+	} else {
+		set_page_refcounted(page);
+		__free_pages(page, order);
+	}
 }
 
 #if defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) || \