On 11/09/2018 12:17 PM, Naoya Horiguchi wrote:
> Currently madvise_inject_error() pins the target page when calling
> memory error handler, but it's not good because the refcount is just
> an artifact of error injector and mock nothing about hw error itself.
> IOW, pinning the error page is part of error handler's task, so
> let's stop doing it.
Did not get that. Could you please kindly explain how an incremented
ref count through get_user_pages_fast() was a mocking the HW error
previously ? Though I might be missing the some context here.
>
> Signed-off-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
> ---
> mm/madvise.c | 25 +++++++++++--------------
> 1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git v4.19-mmotm-2018-10-30-16-08/mm/madvise.c
> v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c
> index 6cb1ca9..9fa0225 100644
> --- v4.19-mmotm-2018-10-30-16-08/mm/madvise.c
> +++ v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c
> @@ -637,6 +637,16 @@ static int madvise_inject_error(int behavior,
> ret = get_user_pages_fast(start, 1, 0, &page);
> if (ret != 1)
> return ret;
> + /*
> + * The get_user_pages_fast() is just to get the pfn of the
> + * given address, and the refcount has nothing to do with
> + * what we try to test, so it should be released immediately.
> + * This is racy but it's intended because the real hardware
> + * errors could happen at any moment and memory error handlers
> + * must properly handle the race.
> + */
> + put_page(page);
> +
> pfn = page_to_pfn(page);
>
> /*
> @@ -646,16 +656,11 @@ static int madvise_inject_error(int behavior,
> */
> order = compound_order(compound_head(page));
>
> - if (PageHWPoison(page)) {
> - put_page(page);
> - continue;
> - }
> -
> if (behavior == MADV_SOFT_OFFLINE) {
> pr_info("Soft offlining pfn %#lx at process virtual
> address %#lx\n",
> pfn, start);
>
> - ret = soft_offline_page(page, MF_COUNT_INCREASED);
> + ret = soft_offline_page(page, 0);
Probably something defined as a new "ignored" in the memory faults flag
enumeration instead of passing '0' directly.
