Re: [PATCH] mm: mempolicy: use VM_BUG_ON_VMA in queue_pages_test_walk()

["Li Xinhai" <lixinhai.lxh@gmail.com>]

On 2020-01-16 at 01:27 Yang Shi wrote:
>
>
>On 1/15/20 4:08 AM, Li Xinhai wrote:
>> On 2020-01-15 at 14:09 Yang Shi wrote:
>>> The VM_BUG_ON() is already used by queue_pages_test_walk(), it sounds
>>> better to dump more debug information by using VM_BUG_ON_VMA() to help
>>> debugging.
>>>
>>> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
>> The .test_walk() is to be called from pagewalk with the rule that 'start'
>> and 'end' must within range of vma, in case the rule is broke, we detect
>> it. This is not quite relevant to a bug of particular vma.
>
>But when you run into VMA range check failure, isn't it helpful to dump
>the VMA range information to ease debugging? And, VM_BUG_ON is already
>used in the code, I'm supposed the users may prefer more debug
>information dumped for debug kernel.
> 
Got your point, it is already used better put more information.
>>
>>> ---
>>> mm/mempolicy.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>>> index 067cf7d..801d45d 100644
>>> --- a/mm/mempolicy.c
>>> +++ b/mm/mempolicy.c
>>> @@ -621,7 +621,7 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
>>> unsigned long flags = qp->flags;
>>>
>>> /* range check first */
>>> -	VM_BUG_ON((vma->vm_start > start) || (vma->vm_end < end));
>>> +	VM_BUG_ON_VMA((vma->vm_start > start) || (vma->vm_end < end), vma);
>>>
>>> if (!qp->first) {
>>> qp->first = vma;
>>> --
>>> 1.8.3.1
>>>
>> >
>