On 08/28/2017 03:34 PM, Mel Gorman wrote:
> Wendy Wang reported off-list that a RAS HWPOISON-SOFT test case failed and
> bisected it to the commit 479f854a207c ("mm, page_alloc: defer debugging
> checks of pages allocated from the PCP"). The problem is that a page that
> was poisoned with madvise() is reused. The commit removed a check that
> would trigger if DEBUG_VM was enabled but re-enabling the check only
> fixes the problem as a side-effect by printing a bad_page warning and
> recovering.
>
> The root of the problem is that a madvise() can leave a poisoned on
> the per-cpu list. This patch drains all per-cpu lists after pages are
> poisoned so that they will not be reused. Wendy reports that the test case
> in question passes with this patch applied. While this could be done in
> a targeted fashion, it is over-complicated for such a rare operation.
>
> Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages
> allocated from the PCP")
> Reported-and-tested-by: Wang, Wendy <[email protected]>
> Cc: [email protected]
> Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
> ---
> mm/madvise.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 23ed525bc2bc..4d7d1e5ddba9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -613,6 +613,7 @@ static int madvise_inject_error(int behavior,
> unsigned long start, unsigned long end)
> {
> struct page *page;
> + struct zone *zone;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
> @@ -646,6 +647,11 @@ static int madvise_inject_error(int behavior,
> if (ret)
> return ret;
> }
> +
> + /* Ensure that all poisoned pages are removed from per-cpu lists */
> + for_each_populated_zone(zone)
> + drain_all_pages(zone);
> +
> return 0;
> }
> #endif
>
> --
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