On Mon 23-05-16 09:54:31, Yang Shi wrote: > Per the suggestion from Michal Hocko [1], CONFIG_DEFERRED_STRUCT_PAGE_INIT > should be incompatible with FLATMEM, make this explicitly in Kconfig. I guess the changelog could benefit from some clarification. What do you think about the following: " 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 > > Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx> > --- > 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 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>