mm: migration: do not lose soft dirty bit if page is in migration state

If page migration is turned on in config and the page is migrating, we may lose the soft dirty bit. If fork and mprotect are called on migrating pages (once migration is complete) pages do not obtain the soft dirty bit in the correspond pte entries. Fix it adding an appropriate test on swap entries. Signed-off-by: Cyrill Gorcunov <[email protected]> Cc: Pavel Emelyanov <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Matt Mackall <[email protected]> Cc: Xiao Guangrong <[email protected]> Cc: Marcelo Tosatti <[email protected]> Cc: KOSAKI Motohiro <[email protected]> Cc: Stephen Rothwell <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: "Aneesh Kumar K.V" <[email protected]> Cc: Naoya Horiguchi <[email protected]> Cc: Mel Gorman <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Oct 17, 2013 · c3d16e1 · c3d16e1
1 parent d8e2162
commit c3d16e1
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Showing 3 changed files with 9 additions and 2 deletions.
diff --git a/mm/memory.c b/mm/memory.c
@@ -837,6 +837,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 					 */
 					make_migration_entry_read(&entry);
 					pte = swp_entry_to_pte(entry);
+					if (pte_swp_soft_dirty(*src_pte))
+						pte = pte_swp_mksoft_dirty(pte);
 					set_pte_at(src_mm, addr, src_pte, pte);
 				}
 			}

diff --git a/mm/migrate.c b/mm/migrate.c
@@ -161,6 +161,8 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 
 	get_page(new);
 	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
+	if (pte_swp_soft_dirty(*ptep))
+		pte = pte_mksoft_dirty(pte);
 	if (is_write_migration_entry(entry))
 		pte = pte_mkwrite(pte);
 #ifdef CONFIG_HUGETLB_PAGE

diff --git a/mm/mprotect.c b/mm/mprotect.c
@@ -94,13 +94,16 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 			swp_entry_t entry = pte_to_swp_entry(oldpte);
 
 			if (is_write_migration_entry(entry)) {
+				pte_t newpte;
 				/*
 				 * A protection check is difficult so
 				 * just be safe and disable write
 				 */
 				make_migration_entry_read(&entry);
-				set_pte_at(mm, addr, pte,
-					swp_entry_to_pte(entry));
+				newpte = swp_entry_to_pte(entry);
+				if (pte_swp_soft_dirty(oldpte))
+					newpte = pte_swp_mksoft_dirty(newpte);
+				set_pte_at(mm, addr, pte, newpte);
 			}
 			pages++;
 		}