Re: [PATCH] mm/gup: restore the ability to pin more than 2GB at a time

[Christoph Hellwig]

On Tue, Oct 29, 2024 at 08:01:16PM -0700, John Hubbard wrote:
> A user-visible consequence has now appeared: user space can no longer
> pin more than 2GB of memory anymore on x86_64. That's because, on a 4KB
> PAGE_SIZE system, when user space tries to (indirectly, via a device
> driver that calls pin_user_pages()) pin 2GB, this requires an allocation
> of a folio pointers array of MAX_PAGE_ORDER size, which is the limit for
> kmalloc().

Do you have a report whee someone tries to pin that much memor in a
single call?  What driver is this?  Because it seems like a not very
smart thing to do.