Re: [PATCH v3 4/5] fs: hugetlbfs: support poison recover from hugetlbfs_migrate_folio()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2024/5/28 23:41, Luck, Tony wrote:
> +	if (unlikely(folio_mc_copy(dst, src))) {
> +		folio_ref_unfreeze(src, expected_count);
> +		return -EFAULT;
> 
> It doesn't look like any code takes action to avoid re-using the poisoned page.
> 
> So you survived, hurrah! But left the problem page for some other code to trip over.

Hi Tony, thanks for your review,

We tried to avoid calling memory_failure_queue() after 
copy_mc_{user_}highpage(), and I think the memory_failure() should be
called by  ARCH's code(eg, mce in x86)[1] to handle the poisoned page,
but for current mainline, the x86 mce don't do that, so yes, we need a
memory_failure_queue() for x86, but it is not true for upcoming
arm64, the poisoned page is handled by apei_claim_sea()，and a new
memory_failure_queue() is unnecessary(no issue since the
TestSetPageHWPoison() check in memory_failure()).

It seems that the khugepaged[3][4] should do the same thing, we could
call memory_failure_queue() in copy_mc_{user_}highpage(), and remove
it from each caller, is that OK?

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 00341b56d291..6b0d6f3c8580 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -352,6 +352,9 @@ static inline int copy_mc_user_highpage(struct page 
*to, struct page *from,
         kunmap_local(vto);
         kunmap_local(vfrom);

+       if (ret)
+               memory_failure_queue(page_to_pfn(from), 0);
+
         return ret;
  }

@@ -368,6 +371,9 @@ static inline int copy_mc_highpage(struct page *to, 
struct page *from)
         kunmap_local(vto);
         kunmap_local(vfrom);

+       if (ret)
+               memory_failure_queue(page_to_pfn(from), 0);
+
         return ret;
  }

Thanks.




[1] 
https://lore.kernel.org/linux-mm/20240204082627.3892816-3-tongtiangen@huawei.com/
[2] 
https://lore.kernel.org/linux-mm/20240528085915.1955987-1-tongtiangen@huawei.com/
[3] 12904d953364 mm/khugepaged: recover from poisoned file-backed memory
[4] 6efc7afb5cc9 mm/hwpoison: introduce copy_mc_highpage



> 
> -Tony