mm: softdirty: clear VM_SOFTDIRTY flag inside clear_refs_write() instead of clear_soft_dirty()

clear_refs_write() is called earlier than clear_soft_dirty() and it is
more natural to clear VM_SOFTDIRTY (which belongs to VMA entry but not
PTEs) that early instead of clearing it a way deeper inside call chain.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 442177b1119a..2101ce46a5d2 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -737,9 +737,6 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
                 ptent = pte_file_clear_soft_dirty(ptent);
         }
 
-        if (vma->vm_flags & VM_SOFTDIRTY)
-                vma->vm_flags &= ~VM_SOFTDIRTY;
-
         set_pte_at(vma->vm_mm, addr, pte, ptent);
 #endif
 }
@@ -807,8 +804,9 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 
         if (type == CLEAR_REFS_SOFT_DIRTY) {
                 soft_dirty_cleared = true;
-                pr_warn_once("The pagemap bits 55-60 has changed their meaning! "
-                                "See the linux/Documentation/vm/pagemap.txt for details.\n");
+                pr_warn_once("The pagemap bits 55-60 has changed their meaning!"
+                             " See the linux/Documentation/vm/pagemap.txt for "
+                             "details.\n");
         }
 
         task = get_proc_task(file_inode(file));
@@ -839,11 +837,17 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                          *
                          * Writing 3 to /proc/pid/clear_refs only affects file
                          * mapped pages.
+                         *
+                         * Writing 4 to /proc/pid/clear_refs affects all pages.
                          */
                         if (type == CLEAR_REFS_ANON && vma->vm_file)
                                 continue;
                         if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
                                 continue;
+                        if (type == CLEAR_REFS_SOFT_DIRTY) {
+                                if (vma->vm_flags & VM_SOFTDIRTY)
+                                        vma->vm_flags &= ~VM_SOFTDIRTY;
+                        }
                         walk_page_range(vma->vm_start, vma->vm_end,
                                         &clear_refs_walk);
                 }