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-rw-r--r--fs/fs-writeback.c54
-rw-r--r--mm/backing-dev.c69
2 files changed, 70 insertions, 53 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 9f5cab75c15..905f3ea3848 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -78,21 +78,17 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
spin_lock(&bdi->wb_lock);
list_add_tail(&work->list, &bdi->work_list);
- spin_unlock(&bdi->wb_lock);
-
- /*
- * If the default thread isn't there, make sure we add it. When
- * it gets created and wakes up, we'll run this work.
- */
- if (unlikely(!bdi->wb.task)) {
+ if (bdi->wb.task) {
+ wake_up_process(bdi->wb.task);
+ } else {
+ /*
+ * The bdi thread isn't there, wake up the forker thread which
+ * will create and run it.
+ */
trace_writeback_nothread(bdi, work);
wake_up_process(default_backing_dev_info.wb.task);
- } else {
- struct bdi_writeback *wb = &bdi->wb;
-
- if (wb->task)
- wake_up_process(wb->task);
}
+ spin_unlock(&bdi->wb_lock);
}
static void
@@ -800,7 +796,6 @@ int bdi_writeback_thread(void *data)
{
struct bdi_writeback *wb = data;
struct backing_dev_info *bdi = wb->bdi;
- unsigned long wait_jiffies = -1UL;
long pages_written;
current->flags |= PF_FLUSHER | PF_SWAPWRITE;
@@ -812,13 +807,6 @@ int bdi_writeback_thread(void *data)
*/
set_user_nice(current, 0);
- /*
- * 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);
-
trace_writeback_thread_start(bdi);
while (!kthread_should_stop()) {
@@ -828,18 +816,6 @@ int bdi_writeback_thread(void *data)
if (pages_written)
wb->last_active = jiffies;
- else if (wait_jiffies != -1UL) {
- unsigned long max_idle;
-
- /*
- * Longest period of inactivity that we tolerate. If we
- * see dirty data again later, the thread will get
- * recreated automatically.
- */
- max_idle = max(5UL * 60 * HZ, wait_jiffies);
- if (time_after(jiffies, max_idle + wb->last_active))
- break;
- }
set_current_state(TASK_INTERRUPTIBLE);
if (!list_empty(&bdi->work_list)) {
@@ -847,21 +823,15 @@ int bdi_writeback_thread(void *data)
continue;
}
- if (dirty_writeback_interval) {
- wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
- schedule_timeout(wait_jiffies);
- } else
+ if (dirty_writeback_interval)
+ schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
+ else
schedule();
try_to_freeze();
}
- wb->task = NULL;
-
- /*
- * Flush any work that raced with us exiting. No new work
- * will be added, since this bdi isn't discoverable anymore.
- */
+ /* Flush any work that raced with us exiting */
if (!list_empty(&bdi->work_list))
wb_do_writeback(wb, 1);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e104e32c2ee..9c1c199f88c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -316,6 +316,18 @@ static void sync_supers_timer_fn(unsigned long unused)
bdi_arm_supers_timer();
}
+/*
+ * Calculate the longest interval (jiffies) bdi threads are allowed to be
+ * inactive.
+ */
+static unsigned long bdi_longest_inactive(void)
+{
+ unsigned long interval;
+
+ interval = msecs_to_jiffies(dirty_writeback_interval * 10);
+ return max(5UL * 60 * HZ, interval);
+}
+
static int bdi_forker_thread(void *ptr)
{
struct bdi_writeback *me = ptr;
@@ -329,11 +341,12 @@ static int bdi_forker_thread(void *ptr)
set_user_nice(current, 0);
for (;;) {
- struct task_struct *task;
+ struct task_struct *task = NULL;
struct backing_dev_info *bdi;
enum {
NO_ACTION, /* Nothing to do */
FORK_THREAD, /* Fork bdi thread */
+ KILL_THREAD, /* Kill inactive bdi thread */
} action = NO_ACTION;
/*
@@ -346,10 +359,6 @@ static int bdi_forker_thread(void *ptr)
spin_lock_bh(&bdi_lock);
set_current_state(TASK_INTERRUPTIBLE);
- /*
- * Check if any existing bdi's have dirty data without
- * a thread registered. If so, set that up.
- */
list_for_each_entry(bdi, &bdi_list, bdi_list) {
bool have_dirty_io;
@@ -376,6 +385,25 @@ static int bdi_forker_thread(void *ptr)
action = FORK_THREAD;
break;
}
+
+ spin_lock(&bdi->wb_lock);
+ /*
+ * If there is no work to do and the bdi thread was
+ * inactive long enough - kill it. The wb_lock is taken
+ * to make sure no-one adds more work to this bdi and
+ * wakes the bdi thread up.
+ */
+ if (bdi->wb.task && !have_dirty_io &&
+ time_after(jiffies, bdi->wb.last_active +
+ bdi_longest_inactive())) {
+ task = bdi->wb.task;
+ bdi->wb.task = NULL;
+ spin_unlock(&bdi->wb_lock);
+ set_bit(BDI_pending, &bdi->state);
+ action = KILL_THREAD;
+ break;
+ }
+ spin_unlock(&bdi->wb_lock);
}
spin_unlock_bh(&bdi_lock);
@@ -394,8 +422,20 @@ static int bdi_forker_thread(void *ptr)
* the bdi from the thread.
*/
bdi_flush_io(bdi);
- } else
+ } else {
+ /*
+ * The spinlock makes sure we do not lose
+ * wake-ups when racing with 'bdi_queue_work()'.
+ */
+ spin_lock(&bdi->wb_lock);
bdi->wb.task = task;
+ spin_unlock(&bdi->wb_lock);
+ }
+ break;
+
+ case KILL_THREAD:
+ __set_current_state(TASK_RUNNING);
+ kthread_stop(task);
break;
case NO_ACTION:
@@ -407,6 +447,13 @@ static int bdi_forker_thread(void *ptr)
/* Back to the main loop */
continue;
}
+
+ /*
+ * 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);
}
return 0;
@@ -490,15 +537,15 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
return;
/*
- * If setup is pending, wait for that to complete first
+ * Make sure nobody finds us on the bdi_list anymore
*/
- wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
- TASK_UNINTERRUPTIBLE);
+ bdi_remove_from_list(bdi);
/*
- * Make sure nobody finds us on the bdi_list anymore
+ * If setup is pending, wait for that to complete first
*/
- bdi_remove_from_list(bdi);
+ wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
/*
* Finally, kill the kernel thread. We don't need to be RCU