[RFC PATCH 4/6] mm/memory: Add tree limit to free_pgtables()

[David Hildenbrand]

On 03.09.25 22:19, Liam R. Howlett wrote:
> * Lorenzo Stoakes <lorenzo.stoakes at oracle.com> [250819 15:14]:
>> On Fri, Aug 15, 2025 at 03:10:29PM -0400, Liam R. Howlett wrote:
>>> The ceiling and tree search limit need to be different arguments for the
>>> future change in the failed fork attempt.
>>>
>>> No functional changes intended.
>>>
>>> Signed-off-by: Liam R. Howlett <Liam.Howlett at oracle.com>
>>
>> (Obv. in addition to comment about broken VMA tests :P)
>>
>> I guess intent is that if we discover any page tables beyond tree_max then
>> we ought to just wipe them all out so, in effect, we don't consider
>> mappings at or past tree_max to be valid?
> 
> Actually... there are some archs that map outside the vma and they are
> valid.. I think mips? and I think lower, but yeah.. it's needed.  This
> is why prev->vm_end and next->vm_start are used as page table limits,
> afaik.  This is a serious annoyance because it frequently adds walks
> that are infrequently necessary to the vma tree.

Hm, does that still exist?

I recall something odd ... was it that gate area thingy (in_gate_area) 
we also have to handle in GUP code? The is x86/arm though, not mips.

-- 
Cheers

David / dhildenb