"Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> writes:
> * Michael Ellerman <mpe@xxxxxxxxxxxxxx> [240807 08:41]:
>> Add an optional close() callback to struct vm_special_mapping. It will
>> be used, by powerpc at least, to handle unmapping of the VDSO.
>>
>> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
>> ---
>> include/linux/mm_types.h | 2 ++
>> mm/mmap.c | 3 +++
>> 2 files changed, 5 insertions(+)
>>
>> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
>> index 485424979254..ef32d87a3adc 100644
>> --- a/include/linux/mm_types.h
>> +++ b/include/linux/mm_types.h
>> @@ -1313,6 +1313,8 @@ struct vm_special_mapping {
>>
>> int (*mremap)(const struct vm_special_mapping *sm,
>> struct vm_area_struct *new_vma);
>
> nit: missing new line?
Ack.
>> + void (*close)(const struct vm_special_mapping *sm,
>> + struct vm_area_struct *vma);
>> };
>>
>> enum tlb_flush_reason {
>> diff --git a/mm/mmap.c b/mm/mmap.c
>> index d0dfc85b209b..24bd6aa9155c 100644
>> --- a/mm/mmap.c
>> +++ b/mm/mmap.c
>> @@ -3624,6 +3624,9 @@ static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
>> */
>
> The above comment should probably be expanded to explain what this is
> about, or removed.
I expanded it slightly, happy for others to wordsmith it further.
>> static void special_mapping_close(struct vm_area_struct *vma)
>> {
>> + const struct vm_special_mapping *sm = vma->vm_private_data;
>> + if (sm->close)
>> + sm->close(sm, vma);
>
> Right now we have the same sort of situation for mremap calls on
> special: we have a call to the specific vma mremap() function.
> ...
> So, are we missing an opportunity to avoid every arch having the same
> implementation here (that will evolve into random bugs existing in some
> archs for years before someone realises the cloned code wasn't fixed)?
> Do we already have a fix in ppc for the size checking that doesn't exist
> in the other archs in the case of mremap?
I took this as more of a meta comment/rant :)
Yes I agree the implementation should eventually be generic, but this series
is just about moving the existing powerpc behaviour from arch_unmap()
into this hook.
cheers
