On Tue, Sep 14, 2021 at 11:37:18AM -0700, Yang Shi wrote:
> Currently hwpoison doesn't handle non-anonymous THP, but since v4.8 THP
> support for tmpfs and read-only file cache has been added. They could
> be offlined by split THP, just like anonymous THP.
>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> ---
> mm/memory-failure.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 3e06cb9d5121..6f72aab8ec4a 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1150,13 +1150,16 @@ static int __get_hwpoison_page(struct page *page)
>
> if (PageTransHuge(head)) {
> /*
> - * Non anonymous thp exists only in allocation/free time. We
> - * can't handle such a case correctly, so let's give it up.
> - * This should be better than triggering BUG_ON when kernel
> - * tries to touch the "partially handled" page.
> + * We can't handle allocating or freeing THPs, so let's give
> + * it up. This should be better than triggering BUG_ON when
> + * kernel tries to touch the "partially handled" page.
> + *
> + * page->mapping won't be initialized until the page is added
> + * to rmap or page cache. Use this as an indicator for if
> + * this is an instantiated page.
> */
> - if (!PageAnon(head)) {
> - pr_err("Memory failure: %#lx: non anonymous thp\n",
> + if (!head->mapping) {
> + pr_err("Memory failure: %#lx: non instantiated thp\n",
> page_to_pfn(page));
> return 0;
> }
How about cleaning up this whole "PageTransHuge()" block? As explained in
commit 415c64c1453a (mm/memory-failure: split thp earlier in memory error
handling), this check was introduced to avoid that non-anonymous thp is
considered as hugetlb and code for hugetlb is executed (resulting in crash).
With recent improvement in __get_hwpoison_page(), this confusion never
happens (because hugetlb check is done before this check), so this check
seems to finish its role.
Thanks,
Naoya Horiguchi
> @@ -1415,12 +1418,12 @@ static int identify_page_state(unsigned long pfn, struct page *p,
> static int try_to_split_thp_page(struct page *page, const char *msg)
> {
> lock_page(page);
> - if (!PageAnon(page) || unlikely(split_huge_page(page))) {
> + if (!page->mapping || unlikely(split_huge_page(page))) {
> unsigned long pfn = page_to_pfn(page);
>
> unlock_page(page);
> - if (!PageAnon(page))
> - pr_info("%s: %#lx: non anonymous thp\n", msg, pfn);
> + if (!page->mapping)
> + pr_info("%s: %#lx: not instantiated thp\n", msg, pfn);
> else
> pr_info("%s: %#lx: thp split failed\n", msg, pfn);
> put_page(page);
> --
> 2.26.2
>
