[PATCH v5 24/38] mm/vma: enforce that mm-managed mappings may not set VMA_IO_BIT

[David Hildenbrand (Arm)]

On 10/12/26 20:48, Lorenzo Stoakes (ARM) wrote:
> On Mon, Oct 12, 2026 at 08:39:35PM +0200, David Hildenbrand (Arm) wrote:
>> On 10/12/26 20:35, Lorenzo Stoakes (ARM) wrote:
>>>
>>> That gets removed.
>>>
>>>
>>> I mean we do that in a subsequent commit, I think even the next one?
>>>
>>>
>>>
>>> Yeah, but to do that the code would now be something like:
>>>
>>> 	vma_flags_t masked = flags;
>>>
>>> 	/*
>>> 	  * vma_flags_is_mm_managed() tests VMA_IO_BIT, which will be removed
>>> 	 * in the next commit.
>>> 	 */
>>> 	vma_flags_clear(&flags, VMA_IO_BIT);
>>> 	if (!vma_flags_is_mm_managed(masked)) {
>>> 		...
>>> 	}
>>>
>>> Is that really worth it?
>>>
>>> I don't think there's really too much confusion intra-patch about that is there?
>>
>> I would do it as above (- the comment, as that is the next patch indeed) and
>> only remove the vma_flags_clear() in the next patch.
>>
>> But in any case, you should spell out that this is only temporary in the patch
>> description :)
> 
> And then there's a 'masked' variable that is unused?
> 
> You need to have two vma_flags_t variables to be able both clear VMA_IO_BIT
> and use vma_flags_is_mm_managed().
> 
> So the change would have to be
> 
> + 	vma_flags_t masked = *flags;
> +
> + 	vma_flags_clear(&flags, VMA_IO_BIT);
> + 	if (!vma_flags_is_mm_managed(&masked)) {
> + 		...
> + 	}
> 
> Then:
> 
> - 	vma_flags_t masked = *flags;
> -
> - 	vma_flags_clear(&flags, VMA_IO_BIT);
> - 	if (!vma_flags_is_mm_managed(&masked)) {
> + 	if (!vma_flags_is_mm_managed(flags)) {
>  		...
>  	}
> 
> Which doesn't really seem worth it for somebody who is confused between two
> patches mid-series.
> 
> But if you feel strongly I can make the change like that?

Whatever you prefer. Most important thing for me was finding it in the next
patch and being pleasantly surprised ;)

-- 
Cheers,

David