mm/resource: Return real error codes from walk failures

walk_system_ram_range() can return an error code either becuase
*it* failed, or because the 'func' that it calls returned an
error.  The memory hotplug does the following:

	ret = walk_system_ram_range(..., func);
        if (ret)
		return ret;

and 'ret' makes it out to userspace, eventually.  The problem
s, walk_system_ram_range() failues that result from *it* failing
(as opposed to 'func') return -1.  That leads to a very odd
-EPERM (-1) return code out to userspace.

Make walk_system_ram_range() return -EINVAL for internal
failures to keep userspace less confused.

This return code is compatible with all the callers that I
audited.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: linux-nvdimm@lists.01.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: Huang Ying <ying.huang@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

kernel/resource.c

@@ -382,7 +382,7 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
 				 int (*func)(struct resource *, void *))
 {
 	struct resource res;
-	int ret = -1;
+	int ret = -EINVAL;
 
 	while (start < end &&
 	       !find_next_iomem_res(start, end, flags, desc, first_lvl, &res)) {
@@ -462,7 +462,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 	unsigned long flags;
 	struct resource res;
 	unsigned long pfn, end_pfn;
-	int ret = -1;
+	int ret = -EINVAL;
 
 	start = (u64) start_pfn << PAGE_SHIFT;
 	end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;