mm/swapfile: fix lost swap bits in unuse_pte()

This is observed by code review only but not any real report.

When we turn off swapping we could have lost the bits stored in the swap
ptes.  The new rmap-exclusive bit is fine since that turned into a page
flag, but not for soft-dirty and uffd-wp.  Add them.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Suggested-by: Peter Xu <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: David Howells <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: NeilBrown <[email protected]>
Cc: Ralph Campbell <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 7 insertions, 3 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index b86d1cc8d00b..e45874fb2ec7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1774,7 +1774,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 {
 	struct page *swapcache;
 	spinlock_t *ptl;
-	pte_t *pte;
+	pte_t *pte, new_pte;
 	int ret = 1;
 
 	swapcache = page;
@@ -1823,8 +1823,12 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 		page_add_new_anon_rmap(page, vma, addr);
 		lru_cache_add_inactive_or_unevictable(page, vma);
 	}
-	set_pte_at(vma->vm_mm, addr, pte,
-		   pte_mkold(mk_pte(page, vma->vm_page_prot)));
+	new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot));
+	if (pte_swp_soft_dirty(*pte))
+		new_pte = pte_mksoft_dirty(new_pte);
+	if (pte_swp_uffd_wp(*pte))
+		new_pte = pte_mkuffd_wp(new_pte);
+	set_pte_at(vma->vm_mm, addr, pte, new_pte);
 	swap_free(entry);
 out:
 	pte_unmap_unlock(pte, ptl);