On Mon, Jun 16, 2025 at 01:20:55PM +0100, Lorenzo Stoakes wrote:

On Mon, Jun 16, 2025 at 09:14:28AM -0300, Jason Gunthorpe wrote:

quoted

Also, probably 'aligned' is not the right name. This new function
should be called by VMA owners that know they have pgoff aligned high
order folios/pfns inside their mapping. The 'align' argument is the
max order of their pgoff aligned folio/pfns.

The purpose of the function is to adjust the resulting area to
optimize for the high order folios that are present while following
the uAPI rules for mmap.

Maybe call it something like _order and document it like the above?

Right, if it were made clear this is explicitly related to higher order
folios that would go a long way to making the generalisation more
acceptable.

But we definitely need to have it not filter errors if it's generic.

quoted

quoted

I also am not okay to export it for no reason.

The next patches are the reason.

Regardless exporting it like this raises the bar for quality here.

Yes, it is also possible we have the wrong op, I know
get_unmapped_area() pre-exists, but if we are really cleaning this
stuff then something like get_max_pte_order() is probably a saner op.

It would return the size of the biggest pgoff aligned folio/pfn within
the file. Then the core code would do the special logic without
exporting this function.

Jason