Per the suggestion from Michal Hocko [1], DEFERRED_STRUCT_PAGE_INIT requires
some ordering wrt other initialization operations, e.g. page_ext_init has to
happen after the whole memmap is initialized properly. For SPARSEMEM this
requires to wait for page_alloc_init_late. Other memory models (e.g. flatmem)
might have different initialization layouts (page_ext_init_flatmem). Currently
DEFERRED_STRUCT_PAGE_INIT depends on MEMORY_HOTPLUG which in turn
depends on SPARSEMEM || X86_64_ACPI_NUMA
depends on ARCH_ENABLE_MEMORY_HOTPLUG
and X86_64_ACPI_NUMA depends on NUMA which in turn disable FLATMEM
memory model:
config ARCH_FLATMEM_ENABLE
def_bool y
depends on X86_32 && !NUMA
so FLATMEM is ruled out via dependency maze. Be explicit and disable
FLATMEM for DEFERRED_STRUCT_PAGE_INIT so that we do not reintroduce
subtle initialization bugs
[1] http://lkml.kernel.org/r/20160523073157.gd2...@dhcp22.suse.cz
CC: Michal Hocko <mho...@kernel.org>
Signed-off-by: Yang Shi <yang....@linaro.org>
---
v2:
Adopted Michal's comments for the commit log
mm/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/Kconfig b/mm/Kconfig
index 2664c11..22fa818 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -649,6 +649,7 @@ config DEFERRED_STRUCT_PAGE_INIT
default n
depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
depends on MEMORY_HOTPLUG
+ depends on !FLATMEM
help
Ordinarily all struct pages are initialised during early boot in a
single thread. On very large machines this can take a considerable
--
2.0.2
