On 12/09/18 08:22 PM, Dan Williams wrote: > devm_memremap_pages() is a facility that can create struct page entries > for any arbitrary range and give drivers the ability to subvert core > aspects of page management. > > Specifically the facility is tightly integrated with the kernel's memory > hotplug functionality. It injects an altmap argument deep into the > architecture specific vmemmap implementation to allow allocating from > specific reserved pages, and it has Linux specific assumptions about > page structure reference counting relative to get_user_pages() and > get_user_pages_fast(). It was an oversight and a mistake that this was > not marked EXPORT_SYMBOL_GPL from the outset. > > Again, devm_memremap_pagex() exposes and relies upon core kernel > internal assumptions and will continue to evolve along with 'struct > page', memory hotplug, and support for new memory types / topologies. > Only an in-kernel GPL-only driver is expected to keep up with this > ongoing evolution. This interface, and functionality derived from this > interface, is not suitable for kernel-external drivers. > > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Mostly to say that I agree with you and Christoph on this debate and that the change to GPL does not affect my P2PDMA work. Logan
