[PATCH v2] mm/hwpoison: Retry with shake_page() for unhandlable pages

[PATCH v2] mm/hwpoison: Retry with shake_page() for unhandlable pages

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

HWPoisonHandlable() sometimes returns false for typical user pages
due to races with average memory events like transfers over LRU lists.
This causes failures in hwpoison handling.

There's retry code for such a case but does not work because the retry
loop reaches the retry limit too quickly before the page settles down to
handlable state. Let get_any_page() call shake_page() to fix it.

Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation")
Reported-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: stable@vger.kernel.org # 5.13
---
ChangeLog v2:
- get_any_page() return -EIO when retry limit reached (by Yang Shi)
---
 mm/memory-failure.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git v5.14-rc6/mm/memory-failure.c v5.14-rc6_patched/mm/memory-failure.c
index eefd823deb67..470400cc7513 100644
--- v5.14-rc6/mm/memory-failure.c
+++ v5.14-rc6_patched/mm/memory-failure.c
@@ -1146,7 +1146,7 @@ static int __get_hwpoison_page(struct page *page)
 	 * unexpected races caused by taking a page refcount.
 	 */
 	if (!HWPoisonHandlable(head))
-		return 0;
+		return -EBUSY;
 
 	if (PageTransHuge(head)) {
 		/*
@@ -1199,9 +1199,15 @@ static int get_any_page(struct page *p, unsigned long flags)
 			}
 			goto out;
 		} else if (ret == -EBUSY) {
-			/* We raced with freeing huge page to buddy, retry. */
-			if (pass++ < 3)
+			/*
+			 * We raced with (possibly temporary) unhandlable
+			 * page, retry.
+			 */
+			if (pass++ < 3) {
+				shake_page(p, 1);
 				goto try_again;
+			}
+			ret = -EIO;
 			goto out;
 		}
 	}
-- 
2.25.1

Re: [PATCH v2] mm/hwpoison: Retry with shake_page() for unhandlable pages

[Yang Shi]

On Wed, Aug 18, 2021 at 5:20 PM Naoya Horiguchi
<naoya.horiguchi@linux.dev> wrote:
>
> From: Naoya Horiguchi <naoya.horiguchi@nec.com>
>
> HWPoisonHandlable() sometimes returns false for typical user pages
> due to races with average memory events like transfers over LRU lists.
> This causes failures in hwpoison handling.
>
> There's retry code for such a case but does not work because the retry
> loop reaches the retry limit too quickly before the page settles down to
> handlable state. Let get_any_page() call shake_page() to fix it.
>
> Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation")
> Reported-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> Cc: stable@vger.kernel.org # 5.13
> ---
> ChangeLog v2:
> - get_any_page() return -EIO when retry limit reached (by Yang Shi)

Thanks for taking this. The fix looks good to me. Reviewed-by: Yang
Shi <shy828301@gmail.com>

> ---
>  mm/memory-failure.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git v5.14-rc6/mm/memory-failure.c v5.14-rc6_patched/mm/memory-failure.c
> index eefd823deb67..470400cc7513 100644
> --- v5.14-rc6/mm/memory-failure.c
> +++ v5.14-rc6_patched/mm/memory-failure.c
> @@ -1146,7 +1146,7 @@ static int __get_hwpoison_page(struct page *page)
>          * unexpected races caused by taking a page refcount.
>          */
>         if (!HWPoisonHandlable(head))
> -               return 0;
> +               return -EBUSY;
>
>         if (PageTransHuge(head)) {
>                 /*
> @@ -1199,9 +1199,15 @@ static int get_any_page(struct page *p, unsigned long flags)
>                         }
>                         goto out;
>                 } else if (ret == -EBUSY) {
> -                       /* We raced with freeing huge page to buddy, retry. */
> -                       if (pass++ < 3)
> +                       /*
> +                        * We raced with (possibly temporary) unhandlable
> +                        * page, retry.
> +                        */
> +                       if (pass++ < 3) {
> +                               shake_page(p, 1);
>                                 goto try_again;
> +                       }
> +                       ret = -EIO;
>                         goto out;
>                 }
>         }
> --
> 2.25.1
>
>