get_dev_pagemap
struct dev_pagemap *get_dev_pagemap(unsigned long pfn);
pgmap = get_dev_pagemap(pfn);
pgmap = get_dev_pagemap(pfn);
conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->start));
conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->end));
EXPORT_SYMBOL_GPL(get_dev_pagemap);