mm: hwpoison: support recovery from ksm_might_need_to_copy()

When the kernel copies a page from ksm_might_need_to_copy(), but runs into
an uncorrectable error, it will crash since poisoned page is consumed by
kernel, this is similar to the issue recently fixed by Copy-on-write
poison recovery.

When an error is detected during the page copy, return VM_FAULT_HWPOISON
in do_swap_page(), and install a hwpoison entry in unuse_pte() when
swapoff, which help us to avoid system crash.  Note, memory failure on a
KSM page will be skipped, but still call memory_failure_queue() to be
consistent with general memory failure process, and we could support KSM
page recovery in the feature.

[wangkefeng.wang@huawei.com: enhance unuse_pte(), fix issue found by lkp]
  Link: https://lkml.kernel.org/r/20221213120523.141588-1-wangkefeng.wang@huawei.com
[wangkefeng.wang@huawei.com: update changelog, alter ksm_might_need_to_copy(), restore unlikely() in unuse_pte()]
  Link: https://lkml.kernel.org/r/20230201074433.96641-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20221209072801.193221-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index dd02780c387f..addf490da146 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2629,8 +2629,11 @@ struct page *ksm_might_need_to_copy(struct page *page,
 		new_page = NULL;
 	}
 	if (new_page) {
-		copy_user_highpage(new_page, page, address, vma);
-
+		if (copy_mc_user_highpage(new_page, page, address, vma)) {
+			put_page(new_page);
+			memory_failure_queue(page_to_pfn(page), 0);
+			return ERR_PTR(-EHWPOISON);
+		}
 		SetPageDirty(new_page);
 		__SetPageUptodate(new_page);
 		__SetPageLocked(new_page);