mm: cleanup ifdef guards for vmem_altmap

Now that ZONE_DEVICE depends on SPARSEMEM_VMEMMAP we can simplify some
ifdef guards to just ZONE_DEVICE.

Link: http://lkml.kernel.org/r/146687646788.39261.8020536391978771940.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Eric Sandeen <sandeen@redhat.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memremap.h

@@ -26,7 +26,7 @@ struct vmem_altmap {
 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
 
-#if defined(CONFIG_SPARSEMEM_VMEMMAP) && defined(CONFIG_ZONE_DEVICE)
+#ifdef CONFIG_ZONE_DEVICE
 struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start);
 #else
 static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)

kernel/memremap.c

@@ -308,12 +308,6 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 	if (is_ram == REGION_INTERSECTS)
 		return __va(res->start);
 
-	if (altmap && !IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) {
-		dev_err(dev, "%s: altmap requires CONFIG_SPARSEMEM_VMEMMAP=y\n",
-				__func__);
-		return ERR_PTR(-ENXIO);
-	}
-
 	if (!ref)
 		return ERR_PTR(-EINVAL);
 
@@ -401,7 +395,6 @@ void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
 	altmap->alloc -= nr_pfns;
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
 struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
 {
 	/*
@@ -427,5 +420,4 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
 
 	return pgmap ? pgmap->altmap : NULL;
 }
-#endif /* CONFIG_SPARSEMEM_VMEMMAP */
 #endif /* CONFIG_ZONE_DEVICE */