4 files changed, 95 insertions, 10 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e907052eeadb..32a8bbd7a9ad 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -53,6 +53,18 @@ struct wb_writeback_work {
         struct completion *done;        /* set if the caller waits */
 };
 
+/*
+ * If an inode is constantly having its pages dirtied, but then the
+ * updates stop dirtytime_expire_interval seconds in the past, it's
+ * possible for the worst case time between when an inode has its
+ * timestamps updated and when they finally get written out to be two
+ * dirtytime_expire_intervals.  We set the default to 12 hours (in
+ * seconds), which means most of the time inodes will have their
+ * timestamps written to disk after 12 hours, but in the worst case a
+ * few inodes might not their timestamps updated for 24 hours.
+ */
+unsigned int dirtytime_expire_interval = 12 * 60 * 60;
+
 /**
  * writeback_in_progress - determine whether there is writeback in progress
  * @bdi: the device's backing_dev_info structure.
@@ -275,8 +287,8 @@ static int move_expired_inodes(struct list_head *delaying_queue,
 
         if ((flags & EXPIRE_DIRTY_ATIME) == 0)
                 older_than_this = work->older_than_this;
-        else if ((work->reason == WB_REASON_SYNC) == 0) {
-                expire_time = jiffies - (HZ * 86400);
+        else if (!work->for_sync) {
+                expire_time = jiffies - (dirtytime_expire_interval * HZ);
                 older_than_this = &expire_time;
         }
         while (!list_empty(delaying_queue)) {
@@ -458,6 +470,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
                  */
                 redirty_tail(inode, wb);
         } else if (inode->i_state & I_DIRTY_TIME) {
+                inode->dirtied_when = jiffies;
                 list_move(&inode->i_wb_list, &wb->b_dirty_time);
         } else {
                 /* The inode is clean. Remove from writeback lists. */
@@ -505,12 +518,17 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
         spin_lock(&inode->i_lock);
 
         dirty = inode->i_state & I_DIRTY;
-        if (((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) &&
-             (inode->i_state & I_DIRTY_TIME)) ||
-            (inode->i_state & I_DIRTY_TIME_EXPIRED)) {
-                dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
-                trace_writeback_lazytime(inode);
-        }
+        if (inode->i_state & I_DIRTY_TIME) {
+                if ((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) ||
+                    unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
+                    unlikely(time_after(jiffies,
+                                        (inode->dirtied_time_when +
+                                         dirtytime_expire_interval * HZ)))) {
+                        dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
+                        trace_writeback_lazytime(inode);
+                }
+        } else
+                inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
         inode->i_state &= ~dirty;
 
         /*
@@ -1131,6 +1149,56 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
         rcu_read_unlock();
 }
 
+/*
+ * Wake up bdi's periodically to make sure dirtytime inodes gets
+ * written back periodically.  We deliberately do *not* check the
+ * b_dirtytime list in wb_has_dirty_io(), since this would cause the
+ * kernel to be constantly waking up once there are any dirtytime
+ * inodes on the system.  So instead we define a separate delayed work
+ * function which gets called much more rarely.  (By default, only
+ * once every 12 hours.)
+ *
+ * If there is any other write activity going on in the file system,
+ * this function won't be necessary.  But if the only thing that has
+ * happened on the file system is a dirtytime inode caused by an atime
+ * update, we need this infrastructure below to make sure that inode
+ * eventually gets pushed out to disk.
+ */
+static void wakeup_dirtytime_writeback(struct work_struct *w);
+static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
+
+static void wakeup_dirtytime_writeback(struct work_struct *w)
+{
+        struct backing_dev_info *bdi;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
+                if (list_empty(&bdi->wb.b_dirty_time))
+                        continue;
+                bdi_wakeup_thread(bdi);
+        }
+        rcu_read_unlock();
+        schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
+}
+
+static int __init start_dirtytime_writeback(void)
+{
+        schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
+        return 0;
+}
+__initcall(start_dirtytime_writeback);
+
+int dirtytime_interval_handler(struct ctl_table *table, int write,
+                               void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        int ret;
+
+        ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+        if (ret == 0 && write)
+                mod_delayed_work(system_wq, &dirtytime_work, 0);
+        return ret;
+}
+
 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
 {
         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
@@ -1269,8 +1337,13 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                         }
 
                         inode->dirtied_when = jiffies;
-                        list_move(&inode->i_wb_list, dirtytime ?
-                                  &bdi->wb.b_dirty_time : &bdi->wb.b_dirty);
+                        if (dirtytime)
+                                inode->dirtied_time_when = jiffies;
+                        if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES))
+                                list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
+                        else
+                                list_move(&inode->i_wb_list,
+                                          &bdi->wb.b_dirty_time);
                         spin_unlock(&bdi->wb.list_lock);
                         trace_writeback_dirty_inode_enqueue(inode);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b4d71b5e1ff2..f4131e8ead74 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -604,6 +604,7 @@ struct inode {
         struct mutex            i_mutex;
 
         unsigned long           dirtied_when;   /* jiffies of first dirtying */
+        unsigned long           dirtied_time_when;
 
         struct hlist_node       i_hash;
         struct list_head        i_wb_list;      /* backing dev IO list */
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 00048339c23e..b2dd371ec0ca 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -130,6 +130,7 @@ extern int vm_dirty_ratio;
 extern unsigned long vm_dirty_bytes;
 extern unsigned int dirty_writeback_interval;
 extern unsigned int dirty_expire_interval;
+extern unsigned int dirtytime_expire_interval;
 extern int vm_highmem_is_dirtyable;
 extern int block_dump;
 extern int laptop_mode;
@@ -146,6 +147,8 @@ extern int dirty_ratio_handler(struct ctl_table *table, int write,
 extern int dirty_bytes_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos);
+int dirtytime_interval_handler(struct ctl_table *table, int write,
+                               void __user *buffer, size_t *lenp, loff_t *ppos);
 
 struct ctl_table;
 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 88ea2d6e0031..ce410bb9f2e1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1228,6 +1228,14 @@ static struct ctl_table vm_table[] = {
                 .extra1         = &zero,
         },
         {
+                .procname       = "dirtytime_expire_seconds",
+                .data           = &dirtytime_expire_interval,
+                .maxlen         = sizeof(dirty_expire_interval),
+                .mode           = 0644,
+                .proc_handler   = dirtytime_interval_handler,
+                .extra1         = &zero,
+        },
+        {
                 .procname       = "nr_pdflush_threads",
                 .mode           = 0444 /* read-only */,
                 .proc_handler   = pdflush_proc_obsolete,