On 2024/5/22 7:54, Jane Chu wrote:
> While handling hwpoison in a THP page, it is possible that
> try_to_split_thp_page() fails. For example, when the THP page has
> been RDMA pinned. At this point, the kernel cannot isolate the
> poisoned THP page, all it could do is to send a SIGBUS to the user
> process with meaningful payload to give user-level recovery a chance.
>
Thanks for your patch.
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
> ---
> mm/memory-failure.c | 35 ++++++++++++++++++++++++++++++-----
> 1 file changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 794196951a04..a14d56e66902 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1706,7 +1706,12 @@ static int identify_page_state(unsigned long pfn, struct page *p,
> return page_action(ps, p, pfn);
> }
>
> -static int try_to_split_thp_page(struct page *page)
> +/*
> + * When 'release' is 'false', it means that if thp split has failed,
> + * there is still more to do, hence the page refcount we took earlier
> + * is still needed.
> + */
> +static int try_to_split_thp_page(struct page *page, bool release)
> {
> int ret;
>
> @@ -1714,7 +1719,7 @@ static int try_to_split_thp_page(struct page *page)
> ret = split_huge_page(page);
> unlock_page(page);
>
> - if (unlikely(ret))
> + if (ret && release)
> put_page(page);
Is "unlikely" still needed?
>
> return ret;
> @@ -2187,6 +2192,24 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> return rc;
> }
>
> +/*
> + * The calling condition is as such: thp split failed, page might have
> + * been RDMA pinned, not much can be done for recovery.
> + * But a SIGBUS should be delivered with vaddr provided so that the user
> + * application has a chance to recover. Also, application processes'
> + * election for MCE early killed will be honored.
> + */
> +static int kill_procs_now(struct page *p, unsigned long pfn, int flags,
> + struct folio *folio)
> +{
> + LIST_HEAD(tokill);
> +
> + collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
> + kill_procs(&tokill, true, pfn, flags);
> +
> + return -EHWPOISON;
> +}
> +
> /**
> * memory_failure - Handle memory failure of a page.
> * @pfn: Page Number of the corrupted page
> @@ -2328,8 +2351,10 @@ int memory_failure(unsigned long pfn, int flags)
> * page is a valid handlable page.
> */
> folio_set_has_hwpoisoned(folio);
> - if (try_to_split_thp_page(p) < 0) {
> - res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
> + if (try_to_split_thp_page(p, false) < 0) {
> + res = kill_procs_now(p, pfn, flags, folio);
No strong opinion but we might remove the return value of kill_procs_now as
it always return -EHWPOISON? We could simply set res to -EHWPOISON here.
Besides from above possible nits, this patch looks good to me.
Acked-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Thanks.
.
