On Fri, May 10, 2024 at 12:26:02AM -0600, Jane Chu wrote:
> When handle hwpoison in a RDMA longterm pinned thp page,
> try_to_split_thp_page() will fail. And at this point, there is
> little else the kernel could do except sending a SIGBUS to
> the user process, thus give it a chance to recover.
Well, it does need to be a RDMA longterm pinned, right?
Anything holding an extra refcount can already make us bite the dust, so
I would not make it that specific.
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
> ---
> mm/memory-failure.c | 31 ++++++++++++++++++++++++++-----
> 1 file changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 2fa884d8b5a3..15bb1c0c42e8 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1697,7 +1697,7 @@ 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)
> +static int try_to_split_thp_page(struct page *page, bool release)
> {
> int ret;
>
> @@ -1705,7 +1705,7 @@ 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);
I would document whhen and when not we can release the page.
E.g: we cannot release it if there are still processes mapping the thp.
> +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;
You are returning -EHWPOISON here,
> +}
> +
> /**
> * memory_failure - Handle memory failure of a page.
> * @pfn: Page Number of the corrupted page
> @@ -2313,8 +2331,11 @@ 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) {
> + pr_err("%#lx: thp split failed\n", pfn);
> + res = kill_procs_now(p, pfn, flags, folio);
> + put_page(p);
> + res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_FAILED);
just to overwrite it here with action_result(). Which one do we need?
I think we would need -EBUSY here, right? So I would drop the retcode
from kill_procs_now.
Also, do we want the extra pr_err() here.
action_result() will already provide us the pfn and the
action_page_types which will be "unsplit thp". Is not that clear enough?
I would drop that.
--
Oscar Salvador
SUSE Labs
