On 2022/7/12 11:28, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
>
> When handling memory error on a hugetlb page, the error handler tries to
> dissolve and turn it into 4kB pages. If it's successfully dissolved,
> PageHWPoison flag is moved to the raw error page, so that's all right.
> However, dissolve sometimes fails, then the error page is left as
> hwpoisoned hugepage. It's useful if we can retry to dissolve it to save
> healthy pages, but that's not possible now because the information about
> where the raw error pages is lost.
>
> Use the private field of a few tail pages to keep that information. The
> code path of shrinking hugepage pool uses this info to try delayed dissolve.
> In order to remember multiple errors in a hugepage, a singly-linked list
> originated from SUBPAGE_INDEX_HWPOISON-th tail page is constructed. Only
> simple operations (adding an entry or clearing all) are required and the
> list is assumed not to be very long, so this simple data structure should
> be enough.
>
> If we failed to save raw error info, the hwpoison hugepage has errors on
> unknown subpage, then this new saving mechanism does not work any more,
> so disable saving new raw error info and freeing hwpoison hugepages.
>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
This patch looks good to me with some nits below.
> ---
...
> +static int hugetlb_set_page_hwpoison(struct page *hpage, struct page *page)
> +{
> + struct llist_head *head;
> + struct raw_hwp_page *raw_hwp;
> + struct llist_node *t, *tnode;
> + int ret = TestSetPageHWPoison(hpage) ? -EHWPOISON : 0;
> +
> + /*
> + * Once the hwpoison hugepage has lost reliable raw error info,
> + * there is little meaning to keep additional error info precisely,
> + * so skip to add additional raw error info.
> + */
> + if (HPageRawHwpUnreliable(hpage))
> + return -EHWPOISON;
> + head = raw_hwp_list_head(hpage);
> + llist_for_each_safe(tnode, t, head->first) {
> + struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
> +
> + if (p->page == page)
> + return -EHWPOISON;
> + }
> +
> + raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
> + if (raw_hwp) {
> + raw_hwp->page = page;
> + llist_add(&raw_hwp->node, head);
> + /* the first error event will be counted in action_result(). */
> + if (ret)
> + num_poisoned_pages_inc();
> + } else {
> + /*
> + * Failed to save raw error info. We no longer trace all
> + * hwpoisoned subpages, and we need refuse to free/dissolve
> + * this hwpoisoned hugepage.
> + */
> + SetHPageRawHwpUnreliable(hpage);
IMHO, when HPageRawHwpUnreliable is set, we can simply free the raw_hwp_list here
to save some memory as they're not used anymore.
> + }
> + return ret;
> +}
> +
> +void hugetlb_clear_page_hwpoison(struct page *hpage)
> +{
> + struct llist_head *head;
> + struct llist_node *t, *tnode;
> +
> + if (!HPageRawHwpUnreliable(hpage))
> + ClearPageHWPoison(hpage);
> + head = raw_hwp_list_head(hpage);
> + llist_for_each_safe(tnode, t, head->first) {
> + struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
> +
> + SetPageHWPoison(p->page);
> + kfree(p);
> + }
> + llist_del_all(head);
> +}
> +
> /*
> * Called from hugetlb code with hugetlb_lock held.
> *
> @@ -1698,7 +1771,7 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
> goto out;
> }
>
> - if (TestSetPageHWPoison(head)) {
> + if (hugetlb_set_page_hwpoison(head, page)) {
> ret = -EHWPOISON;
> goto out;
> }
> @@ -1710,7 +1783,6 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
> return ret;
> }
>
> -#ifdef CONFIG_HUGETLB_PAGE
> /*
> * Taking refcount of hugetlb pages needs extra care about race conditions
> * with basic operations like hugepage allocation/free/demotion.
> @@ -1751,7 +1823,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
> lock_page(head);
>
> if (hwpoison_filter(p)) {
> - ClearPageHWPoison(head);
> + hugetlb_clear_page_hwpoison(head);
If the code reach here, the hugetlb page should be poisoned first time or it will return
in above "res == -EHWPOISON" case. So ClearPageHWPoison should be fine here. But this change
will do the same thing while making the code more consistent. So it should be fine. :)
> res = -EOPNOTSUPP;
> goto out;
> }
>
Anyway, for what it worth,
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Thanks!
