[RFCv2 11/13] mm: Replace hwpoison entry with present PTE if page got unpoisoned

Kirill A. Shutemov
2021-04-16T15:42:06Z

If the page got unpoisoned we can replace hwpoison entry with a present
PTE on page fault instead of delivering SIGBUS.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/memory.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index b15b0c582186..56f93e8e98f9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3280,7 +3280,43 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
vmf->page = device_private_entry_to_page(entry);
ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
} else if (is_hwpoison_entry(entry)) {
- ret = VM_FAULT_HWPOISON;
+ page = hwpoison_entry_to_page(entry);
+
+ locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);
+ if (!locked) {
+ ret = VM_FAULT_RETRY;
+ goto out;
+ }
+
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+
+ if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
+ ret = 0;
+ } else if (PageHWPoison(page)) {
+ ret = VM_FAULT_HWPOISON;
+ } else {
+ /*
+ * The page is unpoisoned. Replace hwpoison
+ * entry with a present PTE.
+ */
+
+ inc_mm_counter(vma->vm_mm, mm_counter(page));
+ pte = mk_pte(page, vma->vm_page_prot);
+
+ if (PageAnon(page)) {
+ page_add_anon_rmap(page, vma,
+ vmf->address, false);
+ } else {
+ page_add_file_rmap(page, false);
+ }
+
+ set_pte_at(vma->vm_mm, vmf->address,
+ vmf->pte, pte);
+ }
+
+ pte_unmap_unlock(vmf->pte, vmf->ptl);
+ unlock_page(page);
} else {
print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
ret = VM_FAULT_SIGBUS;
--
2.26.3