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

commit c3d16e16522fe3fe8759735850a0676da18f4b1d upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index af84bc0ec17c213054b023815ae197fefde7ffb6..440986e572180c88a268d70bc45fd386c291a8d5 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -861,6 +861,8 @@ 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 25ca7caf9092a37cbc46e90c275b2a3a6773a8a5..81af4e678101e99727d952df3f5589354532a8ab 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -157,6 +157,8 @@ 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++;
                }