+ mm-hwposion-support-recovery-from-ksm_might_need_to_copy.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: hwpoison: support recovery from ksm_might_need_to_copy()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-hwposion-support-recovery-from-ksm_might_need_to_copy.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hwposion-support-recovery-from-ksm_might_need_to_copy.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: mm: hwpoison: support recovery from ksm_might_need_to_copy()
Date: Fri, 9 Dec 2022 15:28:01 +0800

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

When an error is detected during the page copy, return VM_FAULT_HWPOISON,
which helps us to avoid the 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 processes.

Link: https://lkml.kernel.org/r/20221209072801.193221-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c      |    8 ++++++--
 mm/memory.c   |    3 +++
 mm/swapfile.c |    2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

--- a/mm/ksm.c~mm-hwposion-support-recovery-from-ksm_might_need_to_copy
+++ a/mm/ksm.c
@@ -2602,8 +2602,12 @@ struct page *ksm_might_need_to_copy(stru
 		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);
+			new_page = ERR_PTR(-EHWPOISON);
+			memory_failure_queue(page_to_pfn(page), 0);
+			return new_page;
+		}
 		SetPageDirty(new_page);
 		__SetPageUptodate(new_page);
 		__SetPageLocked(new_page);
--- a/mm/memory.c~mm-hwposion-support-recovery-from-ksm_might_need_to_copy
+++ a/mm/memory.c
@@ -3878,6 +3878,9 @@ vm_fault_t do_swap_page(struct vm_fault
 		if (unlikely(!page)) {
 			ret = VM_FAULT_OOM;
 			goto out_page;
+		} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
+			ret = VM_FAULT_HWPOISON;
+			goto out_page;
 		}
 		folio = page_folio(page);
 
--- a/mm/swapfile.c~mm-hwposion-support-recovery-from-ksm_might_need_to_copy
+++ a/mm/swapfile.c
@@ -1768,7 +1768,7 @@ static int unuse_pte(struct vm_area_stru
 
 	swapcache = page;
 	page = ksm_might_need_to_copy(page, vma, addr);
-	if (unlikely(!page))
+	if (IS_ERR_OR_NULL(page))
 		return -ENOMEM;
 
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
_

Patches currently in -mm which might be from wangkefeng.wang@huawei.com are

mm-hwposion-support-recovery-from-ksm_might_need_to_copy.patch
mm-add-cond_resched-in-swapin_walk_pmd_entry.patch