linux-kernel - Re: [PATCH] mm: mempolicy: use VM_BUG_ON_VMA in queue_pages_test

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Date:   Mon, 27 Jan 2020 08:59:59 -0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Li Xinhai <lixinhai.lxh@...il.com>,
        akpm <akpm@...ux-foundation.org>
Cc:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: mempolicy: use VM_BUG_ON_VMA in
 queue_pages_test_walk()



On 1/16/20 7:52 AM, Li Xinhai wrote:
> 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@...ux.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.

Hi Andrew,

Would you like to take this patch for v5.6 or v5.7? It looks Xinhai 
agrees with my point.

Thanks,
Yang

>>>> ---
>>>> 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
>>>>
>>>>
> >