2023-07-08 09:15:13

by Miaohe Lin

Subject: [PATCH 1/8] mm: memory-failure: fix potential permanently locked hpage

If hpage isn't Hugetlb page, MF_DELAYED is returned without unlock hpage
leading to hpage permanently locked. But this shouldn't trigger in the
real world because this PageHuge() check is just for potential problems.

Signed-off-by: Miaohe Lin <[email protected]>
---
mm/memory-failure.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a6221a4bc5ea..d21ee27ad412 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1187,8 +1187,10 @@ static int me_huge_page(struct page_state *ps, struct page *p)
struct address_space *mapping;
bool extra_pins = false;

- if (!PageHuge(hpage))
+ if (!PageHuge(hpage)) {
+ unlock_page(hpage);
return MF_DELAYED;
+ }

mapping = page_mapping(hpage);
if (mapping) {
--
2.33.0

2023-07-10 08:10:59

by Naoya Horiguchi

Subject: Re: [PATCH 1/8] mm: memory-failure: fix potential permanently locked hpage

On Sat, Jul 08, 2023 at 04:57:37PM +0800, Miaohe Lin wrote:
> If hpage isn't Hugetlb page, MF_DELAYED is returned without unlock hpage
> leading to hpage permanently locked. But this shouldn't trigger in the
> real world because this PageHuge() check is just for potential problems.

Right, so this if-block is dead code, how about simply removing it?

Thanks,
Naoya Horiguchi

>
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> mm/memory-failure.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index a6221a4bc5ea..d21ee27ad412 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1187,8 +1187,10 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> struct address_space *mapping;
> bool extra_pins = false;
>
> - if (!PageHuge(hpage))
> + if (!PageHuge(hpage)) {
> + unlock_page(hpage);
> return MF_DELAYED;
> + }
>
> mapping = page_mapping(hpage);
> if (mapping) {
> --
> 2.33.0
>
>
>

2023-07-10 08:39:17

by Miaohe Lin

Subject: Re: [PATCH 1/8] mm: memory-failure: fix potential permanently locked hpage

On 2023/7/10 15:56, Naoya Horiguchi wrote:
> On Sat, Jul 08, 2023 at 04:57:37PM +0800, Miaohe Lin wrote:
>> If hpage isn't Hugetlb page, MF_DELAYED is returned without unlock hpage
>> leading to hpage permanently locked. But this shouldn't trigger in the
>> real world because this PageHuge() check is just for potential problems.
>
> Right, so this if-block is dead code, how about simply removing it?

From the current code of view, I think this if-block is actually dead code and won't catch
anything too. So removing it makes sense to me. Will do it in v2.

Thanks Naoya.