diff options
Diffstat (limited to 'mm/backing-dev.c')
| -rw-r--r-- | mm/backing-dev.c | 69 |
1 files changed, 58 insertions, 11 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index e104e32c2ee8..9c1c199f88ce 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 |