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 <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index ca00039471152eae75bb8321a129a4edfc6f580e..f7b7692c05edee78faf951778bb3909143ac9ac1 100644 (file)
--- 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
index a26bccd44ccb0a907662c08135399462bd816b9c..7a7325ee1d089696a8073a84d2f748f326124805 100644 (file)
--- 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
index 94722a4d6b438311de1d1690d81a0d598a907339..a3af058f68e4d9f434337d0dcd6127d5d8c6d039 100644 (file)
--- 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++;
                }