mm: vmalloc: Let user to control huge vmalloc default behavior

maillist inclusion
category: Feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4NDAW
CVE: NA

Reference: https://lore.kernel.org/lkml/20211226083912.166512-4-wangkefeng.wang@huawei.com/t/

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

Add HUGE_VMALLOC_DEFAULT_ENABLED to let user to choose whether or
not enable huge vmalloc mappings by default, and this could make
more architectures to enable huge vmalloc mappings feature but
don't want to enable it by default.

Add hugevmalloc=on/off parameter to enable or disable this feature
at boot time, nohugevmalloc is still supported and equivalent to
hugevmalloc=off.
Signed-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NWang Wensheng <wangwensheng4@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -1587,6 +1587,17 @@
 			on:  enable the feature
 			off: disable the feature
 
+	hugevmalloc	[PPC] Requires CONFIG_HAVE_ARCH_HUGE_VMALLOC
+			Format: { on | off }
+			Default set by CONFIG_HUGE_VMALLOC_DEFAULT_ENABLED.
+
+			This parameter enables/disables kernel huge vmalloc
+			mappings at boot time.
+
+			on:  Enable the feature
+			off: Disable the feature
+			     Equivalent to: nohugevmalloc
+
 	hung_task_panic=
 			[KNL] Should the hung task detector generate panics.
 			Format: 0 | 1

arch/powerpc/Kconfig

@@ -180,6 +180,7 @@ config PPC
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
 	select HAVE_ARCH_HUGE_VMALLOC		if HAVE_ARCH_HUGE_VMAP
+	select HUGE_VMALLOC_DEFAULT_ENABLED	if HAVE_ARCH_HUGE_VMALLOC
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
 	select HAVE_ARCH_KASAN_VMALLOC		if PPC32 && PPC_PAGE_SHIFT <= 14

mm/Kconfig

@@ -284,6 +284,13 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
 config ARCH_ENABLE_THP_MIGRATION
 	bool
 
+config HUGE_VMALLOC_DEFAULT_ENABLED
+	bool "Enable huge vmalloc mappings by default"
+	depends on HAVE_ARCH_HUGE_VMALLOC
+	help
+	  Enable huge vmalloc mappings by default, this value could be overridden
+	  by hugevmalloc=off|on.
+
 config CONTIG_ALLOC
 	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 

mm/vmalloc.c

@@ -43,7 +43,7 @@
 #include "pgalloc-track.h"
 
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC
-static bool __ro_after_init vmap_allow_huge = true;
+static bool __ro_after_init vmap_allow_huge = IS_ENABLED(CONFIG_HUGE_VMALLOC_DEFAULT_ENABLED);
 
 static int __init set_nohugevmalloc(char *str)
 {
@@ -51,6 +51,22 @@ static int __init set_nohugevmalloc(char *str)
 	return 0;
 }
 early_param("nohugevmalloc", set_nohugevmalloc);
+
+static int __init set_hugevmalloc(char *str)
+{
+	if (!str)
+		return -EINVAL;
+
+	if (!strcmp(str, "on"))
+		vmap_allow_huge = true;
+	else if (!strcmp(str, "off"))
+		vmap_allow_huge = false;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+early_param("hugevmalloc", set_hugevmalloc);
 #else /* CONFIG_HAVE_ARCH_HUGE_VMALLOC */
 static const bool vmap_allow_huge = false;
 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMALLOC */