[PATCH 1/5] mm/resource: return real error codes from walk failures

[Dave Hansen]

From: Dave Hansen <dave.hansen at linux.intel.com>

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.

This changes both the generic mm/ and powerpc-specific
implementations to have the same return value.

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

 b/arch/powerpc/mm/mem.c |    2 +-
 b/kernel/resource.c     |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff -puN arch/powerpc/mm/mem.c~memory-hotplug-walk_system_ram_range-returns-neg-1 arch/powerpc/mm/mem.c
--- a/arch/powerpc/mm/mem.c~memory-hotplug-walk_system_ram_range-returns-neg-1	2019-02-25 10:56:47.452908034 -0800
+++ b/arch/powerpc/mm/mem.c	2019-02-25 10:56:47.458908034 -0800
@@ -189,7 +189,7 @@ walk_system_ram_range(unsigned long star
 	struct memblock_region *reg;
 	unsigned long end_pfn = start_pfn + nr_pages;
 	unsigned long tstart, tend;
-	int ret = -1;
+	int ret = -EINVAL;
 
 	for_each_memblock(memory, reg) {
 		tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
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	2019-02-25 10:56:47.454908034 -0800
+++ b/kernel/resource.c	2019-02-25 10:56:47.459908034 -0800
@@ -382,7 +382,7 @@ 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)) {
@@ -462,7 +462,7 @@ 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;
_