4 files changed, 24 insertions, 5 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 04536ebc5ac4..bf21dc6d0dbd 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1177,13 +1177,27 @@ void touch_atime(struct vfsmount *mnt, struct dentry *dentry)
                         return;
                 if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
                         return;
+
+                if (mnt->mnt_flags & MNT_RELATIME) {
+                        /*
+                         * With relative atime, only update atime if the
+                         * previous atime is earlier than either the ctime or
+                         * mtime.
+                         */
+                        if (timespec_compare(&inode->i_mtime,
+                                                &inode->i_atime) < 0 &&
+                            timespec_compare(&inode->i_ctime,
+                                                &inode->i_atime) < 0)
+                                return;
+                }
         }
 
         now = current_fs_time(inode->i_sb);
-        if (!timespec_equal(&inode->i_atime, &now)) {
-                inode->i_atime = now;
-                mark_inode_dirty_sync(inode);
-        }
+        if (timespec_equal(&inode->i_atime, &now))
+                return;
+
+        inode->i_atime = now;
+        mark_inode_dirty_sync(inode);
 }
 EXPORT_SYMBOL(touch_atime);
 
diff --git a/fs/namespace.c b/fs/namespace.c
index fde8553faa76..5ef336c1103c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -368,6 +368,7 @@ static int show_vfsmnt(struct seq_file *m, void *v)
                 { MNT_NOEXEC, ",noexec" },
                 { MNT_NOATIME, ",noatime" },
                 { MNT_NODIRATIME, ",nodiratime" },
+                { MNT_RELATIME, ",relatime" },
                 { 0, NULL }
         };
         struct proc_fs_info *fs_infop;
@@ -1405,9 +1406,11 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
                 mnt_flags |= MNT_NOATIME;
         if (flags & MS_NODIRATIME)
                 mnt_flags |= MNT_NODIRATIME;
+        if (flags & MS_RELATIME)
+                mnt_flags |= MNT_RELATIME;
 
         flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
-                   MS_NOATIME | MS_NODIRATIME);
+                   MS_NOATIME | MS_NODIRATIME | MS_RELATIME);
 
         /* ... and get the mountpoint */
         retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index adce6e1d70c2..186da813541e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -120,6 +120,7 @@ extern int dir_notify_enable;
 #define MS_PRIVATE      (1<<18) /* change to private */
 #define MS_SLAVE        (1<<19) /* change to slave */
 #define MS_SHARED       (1<<20) /* change to shared */
+#define MS_RELATIME     (1<<21) /* Update atime relative to mtime/ctime. */
 #define MS_ACTIVE       (1<<30)
 #define MS_NOUSER       (1<<31)
 
diff --git a/include/linux/mount.h b/include/linux/mount.h
index e357dc86a4de..1b7e178b0d84 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -27,6 +27,7 @@ struct mnt_namespace;
 #define MNT_NOEXEC      0x04
 #define MNT_NOATIME     0x08
 #define MNT_NODIRATIME  0x10
+#define MNT_RELATIME    0x20
 
 #define MNT_SHRINKABLE  0x100