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SubjectRe: [PATCH v2] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas
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> On Apr 18, 2017, at 3:59 PM, Michal Hocko <mhocko@kernel.org> wrote:
>
>> On Tue 18-04-17 14:48:39, Hoeun Ryu wrote:
>> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
>> during boot process and those virtually mapped areas are never unmapped.
>> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
>> existing vmlist entries and prevent those areas from being removed from the
>> rbtree by accident.
>
> Has this been a problem in the past or currently so that it is worth
> handling?
>
>> This flags can be also used by other vmalloc APIs to
>> specify that the area will never go away.
>
> Do we have a user for that?
>
>> This makes remove_vm_area() more robust against other kind of errors (eg.
>> programming errors).
>
> Well, yes it will help to prevent from vfree(early_mem) but we have 4
> users of vm_area_register_early so I am really wondering whether this is
> worth additional code. It would really help to understand your
> motivation for the patch if we were explicit about the problem you are
> trying to solve.

I just think that it would be good to make it robust against various kind of errors.
You might think that's not an enough reason to do so though.

>
> Thanks
>
> --
> Michal Hocko
> SUSE Labs

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