On 2024/9/10 10:19, Miaohe Lin wrote:
On 2024/9/6 10:42, Kefeng Wang wrote:
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@xxxxxxxxxx>
---
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))
Will it be better to put checking ret against -EHWPOISON in a new line? -EAGAIN case will enter the
loop again but -EHWPOISON case never does.
Maybe not a newline since we will recheck the ret in the below and
return directly from copy_present_page().
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)) {
The caller of copy_pte_range() always set errno to -ENOMEM. So fork will failed with ENOMEM even if the real
cause is failed to copy due to hwpoison in source page. It's a pity.
Yes, it's not just the new -EHWPOISON, all other errnos(ENOENT/EIO) will
be ignored and return -ENOMEM instead.
Thanks.
.
