Re: [PATCH 11/17] mm: move get_dev_pagemap out of line

This is a pretty big function, which should be out of line in general, and a no-op stub if CONFIG_ZONE_DEVICЕ is not set. Signed-off-by: Christoph Hellwig <hch(a)lst.de&gt; Reviewed-by: Logan Gunthorpe <logang(a)deltatee.com&gt;

+/** + * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn + * @pfn: page frame number to lookup page_map + * @pgmap: optional known pgmap that already has a reference + * + * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the + * same mapping. + */ +struct dev_pagemap *get_dev_pagemap(unsigned long pfn, + struct dev_pagemap *pgmap) +{ + const struct resource *res = pgmap ? pgmap->res : NULL; + resource_size_t phys = PFN_PHYS(pfn); + + /* + * In the cached case we're already holding a live reference so + * we can simply do a blind increment + */ + if (res && phys >= res->start && phys <= res->end) { + percpu_ref_get(pgmap->ref); + return pgmap; + }