[PATCH 2/2] mm: support poison recovery from copy_present_page()

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

Similar to other poison recovery, use copy_mc_user_highpage() to
avoid potentially kernel panic during copy page in copy_present_page()
from fork, once copy failed due to hwpoison in source page, we need
to break out of copy in copy_pte_range() and release prealloc folio,
so copy_mc_user_highpage() is moved ahead before set *prealloc to NULL.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 mm/memory.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d310c073a1b3..6e7b78e49d1a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -926,8 +926,11 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma
 	 * We have a prealloc page, all good!  Take it
 	 * over and copy the page & arm it.
 	 */
+
+	if (copy_mc_user_highpage(&new_folio->page, page, addr, src_vma))
+		return -EHWPOISON;
+
 	*prealloc = NULL;
-	copy_user_highpage(&new_folio->page, page, addr, src_vma);
 	__folio_mark_uptodate(new_folio);
 	folio_add_new_anon_rmap(new_folio, dst_vma, addr, RMAP_EXCLUSIVE);
 	folio_add_lru_vma(new_folio, dst_vma);
@@ -1166,8 +1169,9 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 		/*
 		 * If we need a pre-allocated page for this pte, drop the
 		 * locks, allocate, and try again.
+		 * If copy failed due to hwpoison in source page, break out.
 		 */
-		if (unlikely(ret == -EAGAIN))
+		if (unlikely(ret == -EAGAIN || ret == -EHWPOISON))
 			break;
 		if (unlikely(prealloc)) {
 			/*
@@ -1197,7 +1201,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 			goto out;
 		}
 		entry.val = 0;
-	} else if (ret == -EBUSY) {
+	} else if (ret == -EBUSY || unlikely(ret == -EHWPOISON)) {
 		goto out;
 	} else if (ret ==  -EAGAIN) {
 		prealloc = folio_prealloc(src_mm, src_vma, addr, false);
-- 
2.27.0