On Fri, Dec 15, 2017 at 6:09 AM, Christoph Hellwig [off-list ref] wrote:

This is a pretty big function, which should be out of line in general,
and a no-op stub if CONFIG_ZONE_DEVIC=D0=95 is not set.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>

[..]

+/**
+ * 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 =3D pgmap ? pgmap->res : NULL;
+       resource_size_t phys =3D 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 >=3D res->start && phys <=3D res->end) {
+               percpu_ref_get(pgmap->ref);
+               return pgmap;
+       }

I was going to say keep the cached case in the static inline, but with
the optimization to the calling convention in the following patch I
think that makes this moot.

So,

Reviewed-by: Dan Williams <redacted>