mm: fix faulty initialization in vmalloc_init()

[KyongHo Cho]

On Fri, May 25, 2012 at 7:12 AM, Andrew Morton <akpm at linux-foundation.org>
wrote:
> On Thu, 24 May 2012 17:32:56 +0900
> KyongHo <pullip.cho at samsung.com> wrote:
>
>> vmalloc_init() adds 'vmap_area's for early 'vm_struct's.
>> This patch fixes vmalloc_init() to correctly initialize
>> vmap_area for the given vm_struct.
>>
>
> <daily message>
> Insufficient information.  When fixing a bug please always always
> always describe the user-visible effects of the bug.  Does the kernel
> instantly crash?  Is it a comestic cleanliness thing which has no
> effect?  Something in between?  I have simply no idea, and am dependent
> upon you to tell me.

Sorry for unkind commit message :)
Why this patch is needed is described by Olav
in the previous replies.

>
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -1185,9 +1185,10 @@ void __init vmalloc_init(void)
>>       /* Import existing vmlist entries. */
>>       for (tmp = vmlist; tmp; tmp = tmp->next) {
>>               va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
>> -             va->flags = tmp->flags | VM_VM_AREA;
>> +             va->flags = VM_VM_AREA;
>
> This change is a mystery.  Why do we no longer transfer ->flags?
>
>>               va->va_start = (unsigned long)tmp->addr;
>>               va->va_end = va->va_start + tmp->size;
>> +             va->vm = tmp;
>
> OK, I can see how this might be important.  But why did you find it
> necessary?  Why was this change actually needed?

If it is not set, find_vm_area() with the early vm regions will always fail.

If the early vm regions must be neither found by find_vm_area()
nor removed by remove_vm_area(), va->vm must be NULL.

Please advise me what is right value for va->vm here :)

>
>>               __insert_vmap_area(va);
>>       }
>
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