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@suse.com Cc: "Jérôme Glisse" jglisse@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Dan Williams dan.j.williams@intel.com --- kernel/memremap.c | 2 +- tools/testing/nvdimm/test/iomap.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/memremap.c b/kernel/memremap.c index 9eced2cc9f94..61dbcaa95530 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -233,7 +233,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) err_array: return ERR_PTR(error); } -EXPORT_SYMBOL(devm_memremap_pages); +EXPORT_SYMBOL_GPL(devm_memremap_pages);
unsigned long vmem_altmap_offset(struct vmem_altmap *altmap) { diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c index ff9d3a5825e1..ed18a0cbc0c8 100644 --- a/tools/testing/nvdimm/test/iomap.c +++ b/tools/testing/nvdimm/test/iomap.c @@ -113,7 +113,7 @@ void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) return nfit_res->buf + offset - nfit_res->res.start; return devm_memremap_pages(dev, pgmap); } -EXPORT_SYMBOL(__wrap_devm_memremap_pages); +EXPORT_SYMBOL_GPL(__wrap_devm_memremap_pages);
pfn_t __wrap_phys_to_pfn_t(phys_addr_t addr, unsigned long flags) {