[PATCH 1/9] mm/resource: return real error codes from walk failures

Dave Hansen
2018-10-22T20:18:37Z

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 is,
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.

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>

---

b/kernel/resource.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN kernel/resource.c~memory-hotplug-walk_system_ram_range-returns-neg-1 kernel/resource.c
--- a/kernel/resource.c~memory-hotplug-walk_system_ram_range-returns-neg-1 2018-10-22 13:12:21.000930395 -0700
+++ b/kernel/resource.c 2018-10-22 13:12:21.003930395 -0700
@@ -375,7 +375,7 @@ static int __walk_iomem_res_desc(resourc
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)) {
@@ -453,7 +453,7 @@ int walk_system_ram_range(unsigned long
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;
_