lkml.org 
[lkml]   [2016]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] mm/memory-failure: fix race with compound page split/merge
Date
# CCed Andrew,

On Mon, Apr 18, 2016 at 02:43:45PM +0300, Konstantin Khlebnikov wrote:
> Get_hwpoison_page() must recheck relation between head and tail pages.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>

Looks good to me. Without this recheck, the race causes kernel to pin
an irrelevant page, and finally makes kernel crash for refcount mismcach...

Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

> ---
> mm/memory-failure.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 78f5f2641b91..ca5acee53b7a 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -888,7 +888,15 @@ int get_hwpoison_page(struct page *page)
> }
> }
>
> - return get_page_unless_zero(head);
> + if (get_page_unless_zero(head)) {
> + if (head == compound_head(page))
> + return 1;
> +
> + pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page));

Recently Chen Yucong replaced the label "MCE:" with "Memory failure:",
but the resolution is trivial, I think.

Thanks,
Naoya Horiguchi

> + put_page(head);
> + }
> +
> + return 0;
> }
> EXPORT_SYMBOL_GPL(get_hwpoison_page);
>
>

\
 
 \ /
  Last update: 2016-04-19 01:41    [W:1.974 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site