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