On Thu, Jan 24, 2019 at 5:21 PM Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
>
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> 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.
>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Ross Zwisler <zwisler@xxxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: linux-nvdimm@xxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Yaowei Bai <baiyaowei@xxxxxxxxxxxxxxxxxxxx>
> Cc: Takashi Iwai <tiwai@xxxxxxx>
> Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
> ---
>
> 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 2019-01-24 15:13:13.950199540 -0800
> +++ b/kernel/resource.c 2019-01-24 15:13:13.954199540 -0800
> @@ -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;
Can you either make a similar change to the powerpc version of
walk_system_ram_range() in arch/powerpc/mm/mem.c or explain why it's
not needed? It *seems* like we'd want both versions of
walk_system_ram_range() to behave similarly in this respect.
> start = (u64) start_pfn << PAGE_SHIFT;
> end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
> _
