resource: report parent to walk_iomem_res_desc() callback

In support of detecting whether a resource might have been been claimed,
report the parent to the walk_iomem_res_desc() callback.  For example, the
ACPI HMAT parser publishes "hmem" platform devices per target range.
However, if the HMAT is disabled / missing a fallback driver can attach
devices to the raw memory ranges as a fallback if it sees unclaimed /
orphan "Soft Reserved" resources in the resource tree.

Otherwise, find_next_iomem_res() returns a resource with garbage data from
the stack allocation in __walk_iomem_res_desc() for the res->parent field.

There are currently no users that expect ->child and ->sibling to be
valid, and the resource_lock would be needed to traverse them.  Use a
compound literal to implicitly zero initialize the fields that are not
being returned in addition to setting ->parent.

Signed-off-by: Dan Williams <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brice Goglin <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: David Airlie <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Jia He <[email protected]>
Cc: Joao Martins <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Hulk Robot <[email protected]>
Cc: Jason Yan <[email protected]>
Cc: "Jérôme Glisse" <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Stefano Stabellini <[email protected]>
Cc: Vivek Goyal <[email protected]>
Link: https://lkml.kernel.org/r/159643097166.4062302.11875688887228572793.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Linus Torvalds <[email protected]>

kernel/resource.c

@@ -382,10 +382,13 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 
 	if (p) {
 		/* copy data */
-		res->start = max(start, p->start);
-		res->end = min(end, p->end);
-		res->flags = p->flags;
-		res->desc = p->desc;
+		*res = (struct resource) {
+			.start = max(start, p->start),
+			.end = min(end, p->end),
+			.flags = p->flags,
+			.desc = p->desc,
+			.parent = p->parent,
+		};
 	}
 
 	read_unlock(&resource_lock);