Re: [PATCH v4 06/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in migration and thp tests

[Gavin Shan]

Hi Anshuman,

On 7/28/21 9:08 PM, Anshuman Khandual wrote:
> On 7/27/21 11:43 AM, Gavin Shan wrote:
> > This uses struct pgtable_debug_args in the migration and thp test
> > functions. It's notable that the pre-allocated page is used in
> > swap_migration_tests() as set_pte_at() is used there.
> >
> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   mm/debug_vm_pgtable.c | 28 ++++++++++++++--------------
> >   1 file changed, 14 insertions(+), 14 deletions(-)
> >
> > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> > index bc153cad9045..9136195efde3 100644
> > --- a/mm/debug_vm_pgtable.c
> > +++ b/mm/debug_vm_pgtable.c
> > @@ -845,7 +845,7 @@ static void __init pmd_swap_tests(struct pgtable_debug_args *args)
> >   static void __init pmd_swap_tests(struct pgtable_debug_args *args) { }
> >   #endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
> >   
> > -static void __init swap_migration_tests(void)
> > +static void __init swap_migration_tests(struct pgtable_debug_args *args)
> >   {
> >   	struct page *page;
> >   	swp_entry_t swp;
> > @@ -861,9 +861,10 @@ static void __init swap_migration_tests(void)
> >   	 * problematic. Lets allocate a dedicated page explicitly for this
> >   	 * purpose that will be freed subsequently.
> >   	 */
> > -	page = alloc_page(GFP_KERNEL);
> > +	page = (args->pte_pfn != ULONG_MAX) ?
> > +	       pfn_to_page(args->pte_pfn) : NULL;
> >   	if (!page) {
> > -		pr_err("page allocation failed\n");
> > +		pr_err("no page available\n");
> >   		return;
> >   	}
>
> Please check for a valid page earlier in the function and return. Otherwise
> this calls out the page unavailability (after starting the test), which is
> inconsistent with all other functions like pxx_advanced_tests().
>
> [    1.051633] debug_vm_pgtable: [pte_swap_tests           ]: Validating PTE swap
> [    1.052697] debug_vm_pgtable: [pmd_swap_tests           ]: Validating PMD swap
> [    1.053765] debug_vm_pgtable: [swap_migration_tests     ]: Validating swap migration <=====
> [    1.054900] debug_vm_pgtable: [swap_migration_tests     ]: no page available         <=====
>
> Should do this just before pr_info("Validating swap migration\n").
>
> ......
> page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL;
> if (!page)
> 	return;
> .....

Yes. The order of error messages are sticky to original implementation, but
it'd better to be consistent with the new order we have in this series. I
will adjust in v5.

Thanks,
Gavin