From: Yang Shi <yang.shi@xxxxxxxxxx> Subject: mm: make CONFIG_DEFERRED_STRUCT_PAGE_INIT depends on !FLATMEM explicitly 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.GD2278@xxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1464027356-32282-1-git-send-email-yang.shi@xxxxxxxxxx Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/Kconfig | 1 + 1 file changed, 1 insertion(+) diff -puN mm/Kconfig~mm-make-config_deferred_struct_page_init-depends-on-flatmem-explicitly mm/Kconfig --- a/mm/Kconfig~mm-make-config_deferred_struct_page_init-depends-on-flatmem-explicitly +++ a/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 _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
