1 files changed, 323 insertions, 18 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 6f163e0f0509..7f3fa79f25c0 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1,8 +1,11 @@
 
 #include <linux/wait.h>
 #include <linux/backing-dev.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
+#include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/writeback.h>
@@ -22,8 +25,18 @@ struct backing_dev_info default_backing_dev_info = {
 EXPORT_SYMBOL_GPL(default_backing_dev_info);
 
 static struct class *bdi_class;
-DEFINE_MUTEX(bdi_lock);
+DEFINE_SPINLOCK(bdi_lock);
 LIST_HEAD(bdi_list);
+LIST_HEAD(bdi_pending_list);
+
+static struct task_struct *sync_supers_tsk;
+static struct timer_list sync_supers_timer;
+
+static int bdi_sync_supers(void *);
+static void sync_supers_timer_fn(unsigned long);
+static void arm_supers_timer(void);
+
+static void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
 
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
@@ -187,6 +200,13 @@ static int __init default_bdi_init(void)
 {
         int err;
 
+        sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
+        BUG_ON(IS_ERR(sync_supers_tsk));
+
+        init_timer(&sync_supers_timer);
+        setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
+        arm_supers_timer();
+
         err = bdi_init(&default_backing_dev_info);
         if (!err)
                 bdi_register(&default_backing_dev_info, NULL, "default");
@@ -195,6 +215,242 @@ static int __init default_bdi_init(void)
 }
 subsys_initcall(default_bdi_init);
 
+static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+{
+        memset(wb, 0, sizeof(*wb));
+
+        wb->bdi = bdi;
+        wb->last_old_flush = jiffies;
+        INIT_LIST_HEAD(&wb->b_dirty);
+        INIT_LIST_HEAD(&wb->b_io);
+        INIT_LIST_HEAD(&wb->b_more_io);
+}
+
+static void bdi_task_init(struct backing_dev_info *bdi,
+                          struct bdi_writeback *wb)
+{
+        struct task_struct *tsk = current;
+
+        spin_lock(&bdi->wb_lock);
+        list_add_tail_rcu(&wb->list, &bdi->wb_list);
+        spin_unlock(&bdi->wb_lock);
+
+        tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
+        set_freezable();
+
+        /*
+         * Our parent may run at a different priority, just set us to normal
+         */
+        set_user_nice(tsk, 0);
+}
+
+static int bdi_start_fn(void *ptr)
+{
+        struct bdi_writeback *wb = ptr;
+        struct backing_dev_info *bdi = wb->bdi;
+        int ret;
+
+        /*
+         * Add us to the active bdi_list
+         */
+        spin_lock(&bdi_lock);
+        list_add(&bdi->bdi_list, &bdi_list);
+        spin_unlock(&bdi_lock);
+
+        bdi_task_init(bdi, wb);
+
+        /*
+         * Clear pending bit and wakeup anybody waiting to tear us down
+         */
+        clear_bit(BDI_pending, &bdi->state);
+        smp_mb__after_clear_bit();
+        wake_up_bit(&bdi->state, BDI_pending);
+
+        ret = bdi_writeback_task(wb);
+
+        /*
+         * Remove us from the list
+         */
+        spin_lock(&bdi->wb_lock);
+        list_del_rcu(&wb->list);
+        spin_unlock(&bdi->wb_lock);
+
+        /*
+         * Flush any work that raced with us exiting. No new work
+         * will be added, since this bdi isn't discoverable anymore.
+         */
+        if (!list_empty(&bdi->work_list))
+                wb_do_writeback(wb, 1);
+
+        wb->task = NULL;
+        return ret;
+}
+
+int bdi_has_dirty_io(struct backing_dev_info *bdi)
+{
+        return wb_has_dirty_io(&bdi->wb);
+}
+
+static void bdi_flush_io(struct backing_dev_info *bdi)
+{
+        struct writeback_control wbc = {
+                .bdi                    = bdi,
+                .sync_mode              = WB_SYNC_NONE,
+                .older_than_this        = NULL,
+                .range_cyclic           = 1,
+                .nr_to_write            = 1024,
+        };
+
+        writeback_inodes_wbc(&wbc);
+}
+
+/*
+ * kupdated() used to do this. We cannot do it from the bdi_forker_task()
+ * or we risk deadlocking on ->s_umount. The longer term solution would be
+ * to implement sync_supers_bdi() or similar and simply do it from the
+ * bdi writeback tasks individually.
+ */
+static int bdi_sync_supers(void *unused)
+{
+        set_user_nice(current, 0);
+
+        while (!kthread_should_stop()) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                schedule();
+
+                /*
+                 * Do this periodically, like kupdated() did before.
+                 */
+                sync_supers();
+        }
+
+        return 0;
+}
+
+static void arm_supers_timer(void)
+{
+        unsigned long next;
+
+        next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
+        mod_timer(&sync_supers_timer, round_jiffies_up(next));
+}
+
+static void sync_supers_timer_fn(unsigned long unused)
+{
+        wake_up_process(sync_supers_tsk);
+        arm_supers_timer();
+}
+
+static int bdi_forker_task(void *ptr)
+{
+        struct bdi_writeback *me = ptr;
+
+        bdi_task_init(me->bdi, me);
+
+        for (;;) {
+                struct backing_dev_info *bdi, *tmp;
+                struct bdi_writeback *wb;
+
+                /*
+                 * Temporary measure, we want to make sure we don't see
+                 * dirty data on the default backing_dev_info
+                 */
+                if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
+                        wb_do_writeback(me, 0);
+
+                spin_lock(&bdi_lock);
+
+                /*
+                 * Check if any existing bdi's have dirty data without
+                 * a thread registered. If so, set that up.
+                 */
+                list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
+                        if (bdi->wb.task)
+                                continue;
+                        if (list_empty(&bdi->work_list) &&
+                            !bdi_has_dirty_io(bdi))
+                                continue;
+
+                        bdi_add_default_flusher_task(bdi);
+                }
+
+                set_current_state(TASK_INTERRUPTIBLE);
+
+                if (list_empty(&bdi_pending_list)) {
+                        unsigned long wait;
+
+                        spin_unlock(&bdi_lock);
+                        wait = msecs_to_jiffies(dirty_writeback_interval * 10);
+                        schedule_timeout(wait);
+                        try_to_freeze();
+                        continue;
+                }
+
+                __set_current_state(TASK_RUNNING);
+
+                /*
+                 * This is our real job - check for pending entries in
+                 * bdi_pending_list, and create the tasks that got added
+                 */
+                bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
+                                 bdi_list);
+                list_del_init(&bdi->bdi_list);
+                spin_unlock(&bdi_lock);
+
+                wb = &bdi->wb;
+                wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
+                                        dev_name(bdi->dev));
+                /*
+                 * If task creation fails, then readd the bdi to
+                 * the pending list and force writeout of the bdi
+                 * from this forker thread. That will free some memory
+                 * and we can try again.
+                 */
+                if (IS_ERR(wb->task)) {
+                        wb->task = NULL;
+
+                        /*
+                         * Add this 'bdi' to the back, so we get
+                         * a chance to flush other bdi's to free
+                         * memory.
+                         */
+                        spin_lock(&bdi_lock);
+                        list_add_tail(&bdi->bdi_list, &bdi_pending_list);
+                        spin_unlock(&bdi_lock);
+
+                        bdi_flush_io(bdi);
+                }
+        }
+
+        return 0;
+}
+
+/*
+ * Add the default flusher task that gets created for any bdi
+ * that has dirty data pending writeout
+ */
+void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
+{
+        if (!bdi_cap_writeback_dirty(bdi))
+                return;
+
+        /*
+         * Check with the helper whether to proceed adding a task. Will only
+         * abort if we two or more simultanous calls to
+         * bdi_add_default_flusher_task() occured, further additions will block
+         * waiting for previous additions to finish.
+         */
+        if (!test_and_set_bit(BDI_pending, &bdi->state)) {
+                list_move_tail(&bdi->bdi_list, &bdi_pending_list);
+
+                /*
+                 * We are now on the pending list, wake up bdi_forker_task()
+                 * to finish the job and add us back to the active bdi_list
+                 */
+                wake_up_process(default_backing_dev_info.wb.task);
+        }
+}
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                 const char *fmt, ...)
 {
@@ -213,13 +469,34 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                 goto exit;
         }
 
-        mutex_lock(&bdi_lock);
+        spin_lock(&bdi_lock);
         list_add_tail(&bdi->bdi_list, &bdi_list);
-        mutex_unlock(&bdi_lock);
+        spin_unlock(&bdi_lock);
 
         bdi->dev = dev;
-        bdi_debug_register(bdi, dev_name(dev));
 
+        /*
+         * Just start the forker thread for our default backing_dev_info,
+         * and add other bdi's to the list. They will get a thread created
+         * on-demand when they need it.
+         */
+        if (bdi_cap_flush_forker(bdi)) {
+                struct bdi_writeback *wb = &bdi->wb;
+
+                wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
+                                                dev_name(dev));
+                if (IS_ERR(wb->task)) {
+                        wb->task = NULL;
+                        ret = -ENOMEM;
+
+                        spin_lock(&bdi_lock);
+                        list_del(&bdi->bdi_list);
+                        spin_unlock(&bdi_lock);
+                        goto exit;
+                }
+        }
+
+        bdi_debug_register(bdi, dev_name(dev));
 exit:
         return ret;
 }
@@ -231,17 +508,42 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 }
 EXPORT_SYMBOL(bdi_register_dev);
 
-static void bdi_remove_from_list(struct backing_dev_info *bdi)
+/*
+ * Remove bdi from the global list and shutdown any threads we have running
+ */
+static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 {
-        mutex_lock(&bdi_lock);
+        struct bdi_writeback *wb;
+
+        if (!bdi_cap_writeback_dirty(bdi))
+                return;
+
+        /*
+         * If setup is pending, wait for that to complete first
+         */
+        wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
+                        TASK_UNINTERRUPTIBLE);
+
+        /*
+         * Make sure nobody finds us on the bdi_list anymore
+         */
+        spin_lock(&bdi_lock);
         list_del(&bdi->bdi_list);
-        mutex_unlock(&bdi_lock);
+        spin_unlock(&bdi_lock);
+
+        /*
+         * Finally, kill the kernel threads. We don't need to be RCU
+         * safe anymore, since the bdi is gone from visibility.
+         */
+        list_for_each_entry(wb, &bdi->wb_list, list)
+                kthread_stop(wb->task);
 }
 
 void bdi_unregister(struct backing_dev_info *bdi)
 {
         if (bdi->dev) {
-                bdi_remove_from_list(bdi);
+                if (!bdi_cap_flush_forker(bdi))
+                        bdi_wb_shutdown(bdi);
                 bdi_debug_unregister(bdi);
                 device_unregister(bdi->dev);
                 bdi->dev = NULL;
@@ -251,18 +553,25 @@ EXPORT_SYMBOL(bdi_unregister);
 
 int bdi_init(struct backing_dev_info *bdi)
 {
-        int i;
-        int err;
+        int i, err;
 
         bdi->dev = NULL;
 
         bdi->min_ratio = 0;
         bdi->max_ratio = 100;
         bdi->max_prop_frac = PROP_FRAC_BASE;
+        spin_lock_init(&bdi->wb_lock);
         INIT_LIST_HEAD(&bdi->bdi_list);
-        INIT_LIST_HEAD(&bdi->b_io);
-        INIT_LIST_HEAD(&bdi->b_dirty);
-        INIT_LIST_HEAD(&bdi->b_more_io);
+        INIT_LIST_HEAD(&bdi->wb_list);
+        INIT_LIST_HEAD(&bdi->work_list);
+
+        bdi_wb_init(&bdi->wb, bdi);
+
+        /*
+         * Just one thread support for now, hard code mask and count
+         */
+        bdi->wb_mask = 1;
+        bdi->wb_cnt = 1;
 
         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
@@ -277,8 +586,6 @@ int bdi_init(struct backing_dev_info *bdi)
 err:
                 while (i--)
                         percpu_counter_destroy(&bdi->bdi_stat[i]);
-
-                bdi_remove_from_list(bdi);
         }
 
         return err;
@@ -289,9 +596,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
 {
         int i;
 
-        WARN_ON(!list_empty(&bdi->b_dirty));
-        WARN_ON(!list_empty(&bdi->b_io));
-        WARN_ON(!list_empty(&bdi->b_more_io));
+        WARN_ON(bdi_has_dirty_io(bdi));
 
         bdi_unregister(bdi);