Re: [PATCH] mm/pgtable/debug: Fix test validating architecture page table helpers

[Christophe Leroy]

Le 13/09/2019 Ã 08:58, Anshuman Khandual a ÃcritÂ:
> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
> > Fix build failure on powerpc.
> >
> > Fix preemption imbalance.
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> >   mm/arch_pgtable_test.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
> > index 8b4a92756ad8..f2b3c9ec35fa 100644
> > --- a/mm/arch_pgtable_test.c
> > +++ b/mm/arch_pgtable_test.c
> > @@ -24,6 +24,7 @@
> >   #include <linux/swap.h>
> >   #include <linux/swapops.h>
> >   #include <linux/sched/mm.h>
> > +#include <linux/highmem.h>
>
> This is okay.
>
> >   #include <asm/pgalloc.h>
> >   #include <asm/pgtable.h>
> >   
> > @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
> >   	p4d_clear_tests(p4dp);
> >   	pgd_clear_tests(mm, pgdp);
> >   
> > +	pte_unmap(ptep);
> > +
>
> Now the preemption imbalance via pte_alloc_map() path i.e
>
> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
>
> Is not this very much powerpc 32 specific or this will be applicable
> for all platform which uses kmap_XXX() to map high memory ?

See 
https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91

I think it applies at least to all arches using the generic implementation.

Applies also to arm:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52

Applies also to mips:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47

Same on sparc:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52

Same on x86:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34

I have not checked others, but I guess it is like that for all.

Christophe