Re: [PATCH] mm/Kconfig: add MMU dependency for MIGRATION.

[Michal Hocko <mhocko@suse.cz>]

On Mon 05-08-13 16:46:14, Chen Gang F T wrote:
> On 08/05/2013 03:32 PM, Michal Hocko wrote:
> > On Thu 01-08-13 10:39:57, Chen Gang wrote:
> >> MIGRATION need depend on MMU, or allmodconfig for sh architecture which
> >> without MMU will be fail for compiling.
> >>
> >> The related error: 
> >>
> >>     CC      mm/migrate.o
> >>   mm/migrate.c: In function 'remove_migration_pte':
> >>   mm/migrate.c:134:3: error: implicit declaration of function 'pmd_trans_huge' [-Werror=implicit-function-declaration]
> >>      if (pmd_trans_huge(*pmd))
> >>      ^
> >>   mm/migrate.c:149:2: error: implicit declaration of function 'is_swap_pte' [-Werror=implicit-function-declaration]
> >>     if (!is_swap_pte(pte))
> >>     ^
> >>   ...
> >>
> >>
> >> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> >> ---
> >>  mm/Kconfig |    4 ++--
> >>  1 files changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/mm/Kconfig b/mm/Kconfig
> >> index 256bfd0..e847f19 100644
> >> --- a/mm/Kconfig
> >> +++ b/mm/Kconfig
> >> @@ -245,7 +245,7 @@ config COMPACTION
> >>  config MIGRATION
> >>  	bool "Page migration"
> >>  	def_bool y
> >> -	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
> >> +	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
> >>  	help
> >>  	  Allows the migration of the physical location of pages of processes
> >>  	  while the virtual addresses are not changed. This is useful in
> >> @@ -522,7 +522,7 @@ config MEM_SOFT_DIRTY
> >>  
> >>  config CMA
> >>  	bool "Contiguous Memory Allocator"
> >> -	depends on HAVE_MEMBLOCK
> >> +	depends on HAVE_MEMBLOCK && MMU
> > 
> > Why CMA has to depend on MMU as well? The MIGRATION part should be
> > sufficient.
> > 
> 
> MIGRATION need depend on MMU, when NOMMU, if select CMA, it will select
> MIGRATION by force.

Ohh, I wasn't aware of this Kcofing limitation. You are right then and
CMA needs a dependency as well.

> e.g. for allmodconfig with sh architecture, if we only let MIGRATION
> depend on MMU, not let CMA depend on MMU, it will report the warning
> below:
> 
>   scripts/kconfig/conf --allmodconfig Kconfig
>   warning: (COMPACTION && CMA) selects MIGRATION which has unmet direct dependencies ((NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU)
> 
> And for the final config file, MIGRATION is still enabled, although MMU
> is not defined.
> 
> 
> >>  	select MIGRATION
> >>  	select MEMORY_ISOLATION
> >>  	help
> > 
> 
> Thanks.
> -- 
> Chen Gang
> 
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-- 
Michal Hocko
SUSE Labs

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