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SubjectRe: [PATCH] arch: um: kernel: skas: mmu: remove pmd_free() and pud_free() for failure processing in init_stub_pte()
On 11/13/2013 05:07 PM, Richard Weinberger wrote:
> Am 13.11.2013 06:06, schrieb Chen Gang:
>> Unfortunately, p?d_alloc() and p?d_free() are not pair!! If p?d_alloc()
>> succeed, they may be used, so in the next failure, we have to skip them
>> to let exit_mmap() or do_munmap() to process it.
>>
>> According to "Documentation/vm/locking", 'mm->page_table_lock' is for
>> using vma list, so not need it when its related vmas are detached or
>> unmapped from using vma list.
>>
>> The related work flow:
>>
>> exit_mmap() ->
>> unmap_vmas(); /* so not need mm->page_table_lock */
>> free_pgtables();
>>
>> do_munmap()->
>> detach_vmas_to_be_unmapped(); /* so not need mm->page_table_lock */
>> unmap_region() ->
>> free_pgtables();
>>
>> free_pgtables() ->
>> free_pgd_range() ->
>> free_pud_range() ->
>> free_pmd_range() ->
>> free_pte_range() ->
>> pmd_clear();
>> pte_free_tlb();
>> pud_clear();
>> pmd_free_tlb();
>> pgd_clear();
>> pud_free_tlb();
>>
>>
>> Signed-off-by: Chen Gang <gang.chen@asianux.com>
>
> Sounds reasonable to me.
> *But* there are patches you from out there that tried to fix similar issues and got reverted later.
> Now I'm a bit nervous and want a ACK from mm folks to have this verified.
> It's not that I don't trust you, but I really don't trust you. ;-)
>

OK, thanks.

> Thanks,
> //richard
>
>

--
Chen Gang


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