On 11/21/2017, 08:24 AM, Michal Hocko wrote:

On Thu 16-11-17 20:46:01, Pavel Tatashin wrote:

quoted

There is no need to have ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT,
as all the page initialization code is in common code.

Also, there is no need to depend on MEMORY_HOTPLUG, as initialization code
does not really use hotplug memory functionality. So, we can remove this
requirement as well.

This patch allows to use deferred struct page initialization on all
platforms with memblock allocator.

Tested on x86, arm64, and sparc. Also, verified that code compiles on
PPC with CONFIG_MEMORY_HOTPLUG disabled.

There is slight risk that we will encounter corner cases on some
architectures with weird memory layout/topology

Which x86_32-pae seems to be. Many bad page state errors are emitted
during boot when this patch is applied:
BUG: Bad page state in process swapper  pfn:3c01c
page:f566c3f0 count:0 mapcount:1 mapping:00000000 index:0x0
flags: 0x0()
raw: 00000000 00000000 00000000 00000000 00000000 00000100 00000200 00000000
raw: 00000000
page dumped because: nonzero mapcount
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Tainted: G    B
4.17.1-4.gdf028bb-pae #1 openSUSE Tumbleweed (unreleased)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.0.0-prebuilt.qemu-project.org 04/01/2014
Call Trace:
 dump_stack+0x7d/0xbd
 bad_page.cold.111+0x90/0xc7
 free_pages_check_bad+0x52/0x70
 free_pcppages_bulk+0x37d/0x570
 free_unref_page_commit+0x9a/0xc0
 free_unref_page+0x6a/0xa0
 __free_pages+0x17/0x30
 free_highmem_page+0x1e/0x50
 add_highpages_with_active_regions+0xd6/0x113
 set_highmem_pages_init+0x67/0x7d
 mem_init+0x23/0x1d9
 start_kernel+0x1c2/0x437
 i386_start_kernel+0x98/0x9c
 startup_32_smp+0x164/0x168

free_pages_check_bad expects mapcount == -1, but it is 1 with this patch.

Reverting the patch makes the BUGs go away -- the config diff is then:

@@ -617,7 +617,7 @@
 # CONFIG_PGTABLE_MAPPING is not set
 # CONFIG_ZSMALLOC_STAT is not set
 CONFIG_GENERIC_EARLY_IOREMAP=y
-CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
+CONFIG_ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT=y
 # CONFIG_IDLE_PAGE_TRACKING is not set
 CONFIG_FRAME_VECTOR=y
 # CONFIG_PERCPU_STATS is not set

quoted

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -148,7 +148,6 @@ config PPC
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_SUPPORTS_ATOMIC_RMW
-	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_WANT_IPC_PARSE_VERSION

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 863a62a6de3c..525c2e3df6f5 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -108,7 +108,6 @@ config S390
 	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 	select ARCH_SAVE_PAGE_KEYS if HIBERNATION
 	select ARCH_SUPPORTS_ATOMIC_RMW
-	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index df3276d6bfe3..00a5446de394 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -69,7 +69,6 @@ config X86
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_SUPPORTS_ATOMIC_RMW
-	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_QUEUED_RWLOCKS

diff --git a/mm/Kconfig b/mm/Kconfig
index 9c4bdddd80c2..c6bd0309ce7a 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig

@@ -639,15 +639,10 @@ config MAX_STACK_SIZE_MB
 
 	  A sane initial value is 80 MB.
 
-# For architectures that support deferred memory initialisation
-config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
-	bool
-
 config DEFERRED_STRUCT_PAGE_INIT
 	bool "Defer initialisation of struct pages to kthreads"
 	default n
-	depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
-	depends on NO_BOOTMEM && MEMORY_HOTPLUG
+	depends on NO_BOOTMEM
 	depends on !FLATMEM
 	help
 	  Ordinarily all struct pages are initialised during early boot in a

thanks,
-- 
js
suse labs