Subject: Re: [PATCH v3] mm/kasan: dump alloc and free stack for page allocator

From: Vlastimil Babka <[email-masked]>
Date: Tue, 17 Sep 2019 10:19:15 +0200

On 9/16/19 5:57 PM, Andrey Ryabinin wrote:
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -710,8 +710,12 @@ static int __init early_debug_pagealloc(char *buf)
>>  	if (kstrtobool(buf, &enable))
>>  		return -EINVAL;
>>  
>> -	if (enable)
>> +	if (enable) {
>>  		static_branch_enable(&_debug_pagealloc_enabled);
>> +#ifdef CONFIG_PAGE_OWNER
>> +		page_owner_free_stack_disabled = false;
> 
> I think this won't work with CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y

Good point, thanks.

>> +#endif
>> +	}
>>  
>>  	return 0;
>>  }
>> diff --git a/mm/page_owner.c b/mm/page_owner.c
>> index dee931184788..b589bfbc4795 100644
>> --- a/mm/page_owner.c
>> +++ b/mm/page_owner.c
>> @@ -24,13 +24,15 @@ struct page_owner {
>>  	short last_migrate_reason;
>>  	gfp_t gfp_mask;
>>  	depot_stack_handle_t handle;
>> -#ifdef CONFIG_DEBUG_PAGEALLOC
>> +#ifdef CONFIG_PAGE_OWNER_FREE_STACK
>>  	depot_stack_handle_t free_handle;
>>  #endif
>>  };
>>  
>>  static bool page_owner_disabled = true;
>> +bool page_owner_free_stack_disabled = true;
>>  DEFINE_STATIC_KEY_FALSE(page_owner_inited);
>> +static DEFINE_STATIC_KEY_FALSE(page_owner_free_stack);
>>  
>>  static depot_stack_handle_t dummy_handle;
>>  static depot_stack_handle_t failure_handle;
>> @@ -46,6 +48,9 @@ static int __init early_page_owner_param(char *buf)
>>  	if (strcmp(buf, "on") == 0)
>>  		page_owner_disabled = false;
>>  
>> +	if (!page_owner_disabled && IS_ENABLED(CONFIG_KASAN))
> 
> I'd rather keep all logic in one place, i.e. "if (!page_owner_disabled && (IS_ENABLED(CONFIG_KASAN) || debug_pagealloc_enabled())"
> With this no changes in early_debug_pagealloc() required and CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y should also work correctly.

In this function it would not work if the debug_pagealloc param gets
processed later than page_owner, but should be doable in
init_page_owner(), I'll try, thanks.

> 
>> +		page_owner_free_stack_disabled = false;
>> +
>>  	return 0;
>>  }
>>  early_param("page_owner", early_page_owner_param);
>  
> 

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