X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Fbacking-dev.c;h=08d357522e784c602205a988687eddbeb0f72c10;hb=062e27ec1b49d12bdb1ecc94d74b5fee5a5775db;hp=6c2a09c8922c1abdbaa49fca05387ee176120138;hpb=c1955ce32fdb0877b7a1b22feb2669358f65be76;p=firefly-linux-kernel-4.4.55.git diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 6c2a09c8922c..08d357522e78 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -10,6 +10,7 @@ #include #include #include +#include static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); @@ -49,8 +50,6 @@ static struct timer_list sync_supers_timer; static int bdi_sync_supers(void *); static void sync_supers_timer_fn(unsigned long); -static void bdi_add_default_flusher_task(struct backing_dev_info *bdi); - #ifdef CONFIG_DEBUG_FS #include #include @@ -237,7 +236,6 @@ static int __init default_bdi_init(void) 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); bdi_arm_supers_timer(); @@ -249,59 +247,6 @@ 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 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_bh(&bdi_lock); - list_add_rcu(&bdi->bdi_list, &bdi_list); - spin_unlock_bh(&bdi_lock); - - current->flags |= PF_FLUSHER | PF_SWAPWRITE; - set_freezable(); - - /* - * Our parent may run at a different priority, just set us to normal - */ - 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); - - ret = bdi_writeback_task(wb); - - wb->task = NULL; - - /* - * 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); - - return ret; -} - int bdi_has_dirty_io(struct backing_dev_info *bdi) { return wb_has_dirty_io(&bdi->wb); @@ -320,10 +265,10 @@ static void bdi_flush_io(struct backing_dev_info *bdi) } /* - * kupdated() used to do this. We cannot do it from the bdi_forker_task() + * kupdated() used to do this. We cannot do it from the bdi_forker_thread() * 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. + * bdi writeback thread individually. */ static int bdi_sync_supers(void *unused) { @@ -359,7 +304,58 @@ static void sync_supers_timer_fn(unsigned long unused) bdi_arm_supers_timer(); } -static int bdi_forker_task(void *ptr) +static void wakeup_timer_fn(unsigned long data) +{ + struct backing_dev_info *bdi = (struct backing_dev_info *)data; + + spin_lock_bh(&bdi->wb_lock); + if (bdi->wb.task) { + trace_writeback_wake_thread(bdi); + wake_up_process(bdi->wb.task); + } else { + /* + * When bdi tasks are inactive for long time, they are killed. + * In this case we have to wake-up the forker thread which + * should create and run the bdi thread. + */ + trace_writeback_wake_forker_thread(bdi); + wake_up_process(default_backing_dev_info.wb.task); + } + spin_unlock_bh(&bdi->wb_lock); +} + +/* + * This function is used when the first inode for this bdi is marked dirty. It + * wakes-up the corresponding bdi thread which should then take care of the + * periodic background write-out of dirty inodes. Since the write-out would + * starts only 'dirty_writeback_interval' centisecs from now anyway, we just + * set up a timer which wakes the bdi thread up later. + * + * Note, we wouldn't bother setting up the timer, but this function is on the + * fast-path (used by '__mark_inode_dirty()'), so we save few context switches + * by delaying the wake-up. + */ +void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi) +{ + unsigned long timeout; + + timeout = msecs_to_jiffies(dirty_writeback_interval * 10); + mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout); +} + +/* + * 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; @@ -372,137 +368,134 @@ static int bdi_forker_task(void *ptr) set_user_nice(current, 0); for (;;) { - struct backing_dev_info *bdi, *tmp; - struct bdi_writeback *wb; + 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; /* * 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)) + if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) { + del_timer(&me->wakeup_timer); wb_do_writeback(me, 0); + } 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_safe(bdi, tmp, &bdi_list, bdi_list) { - if (bdi->wb.task) - continue; - if (list_empty(&bdi->work_list) && - !bdi_has_dirty_io(bdi)) + list_for_each_entry(bdi, &bdi_list, bdi_list) { + bool have_dirty_io; + + if (!bdi_cap_writeback_dirty(bdi) || + bdi_cap_flush_forker(bdi)) continue; - bdi_add_default_flusher_task(bdi); - } + WARN(!test_bit(BDI_registered, &bdi->state), + "bdi %p/%s is not registered!\n", bdi, bdi->name); - set_current_state(TASK_INTERRUPTIBLE); + have_dirty_io = !list_empty(&bdi->work_list) || + wb_has_dirty_io(&bdi->wb); - if (list_empty(&bdi_pending_list)) { - unsigned long wait; + /* + * If the bdi has work to do, but the thread does not + * exist - create it. + */ + if (!bdi->wb.task && have_dirty_io) { + /* + * Set the pending bit - if someone will try to + * unregister this bdi - it'll wait on this bit. + */ + set_bit(BDI_pending, &bdi->state); + 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); - spin_unlock_bh(&bdi_lock); - wait = msecs_to_jiffies(dirty_writeback_interval * 10); - if (wait) - schedule_timeout(wait); + /* Keep working if default bdi still has things to do */ + if (!list_empty(&me->bdi->work_list)) + __set_current_state(TASK_RUNNING); + + switch (action) { + case FORK_THREAD: + __set_current_state(TASK_RUNNING); + task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s", + dev_name(bdi->dev)); + if (IS_ERR(task)) { + /* + * If thread creation fails, force writeout of + * the bdi from the thread. + */ + bdi_flush_io(bdi); + } else { + /* + * The spinlock makes sure we do not lose + * wake-ups when racing with 'bdi_queue_work()'. + */ + spin_lock_bh(&bdi->wb_lock); + bdi->wb.task = task; + spin_unlock_bh(&bdi->wb_lock); + } + break; + + case KILL_THREAD: + __set_current_state(TASK_RUNNING); + kthread_stop(task); + break; + + case NO_ACTION: + if (!wb_has_dirty_io(me) || !dirty_writeback_interval) + /* + * There are no dirty data. The only thing we + * should now care about is checking for + * inactive bdi threads and killing them. Thus, + * let's sleep for longer time, save energy and + * be friendly for battery-driven devices. + */ + schedule_timeout(bdi_longest_inactive()); else - schedule(); + schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); try_to_freeze(); + /* Back to the main loop */ 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_bh(&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. + * Clear pending bit and wakeup anybody waiting to tear us down. */ - 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_bh(&bdi_lock); - list_add_tail(&bdi->bdi_list, &bdi_pending_list); - spin_unlock_bh(&bdi_lock); - - bdi_flush_io(bdi); - } + clear_bit(BDI_pending, &bdi->state); + smp_mb__after_clear_bit(); + wake_up_bit(&bdi->state, BDI_pending); } return 0; } -static void bdi_add_to_pending(struct rcu_head *head) -{ - struct backing_dev_info *bdi; - - bdi = container_of(head, struct backing_dev_info, rcu_head); - INIT_LIST_HEAD(&bdi->bdi_list); - - spin_lock(&bdi_lock); - list_add_tail(&bdi->bdi_list, &bdi_pending_list); - spin_unlock(&bdi_lock); - - /* - * 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); -} - -/* - * 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; - - if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) { - printk(KERN_ERR "bdi %p/%s is not registered!\n", - bdi, bdi->name); - 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_del_rcu(&bdi->bdi_list); - - /* - * We must wait for the current RCU period to end before - * moving to the pending list. So schedule that operation - * from an RCU callback. - */ - call_rcu(&bdi->rcu_head, bdi_add_to_pending); - } -} - /* * Remove bdi from bdi_list, and ensure that it is no longer visible */ @@ -519,23 +512,16 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent, const char *fmt, ...) { va_list args; - int ret = 0; struct device *dev; if (bdi->dev) /* The driver needs to use separate queues per device */ - goto exit; + return 0; va_start(args, fmt); dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args); va_end(args); - if (IS_ERR(dev)) { - ret = PTR_ERR(dev); - goto exit; - } - - spin_lock_bh(&bdi_lock); - list_add_tail_rcu(&bdi->bdi_list, &bdi_list); - spin_unlock_bh(&bdi_lock); + if (IS_ERR(dev)) + return PTR_ERR(dev); bdi->dev = dev; @@ -547,21 +533,21 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent, if (bdi_cap_flush_forker(bdi)) { struct bdi_writeback *wb = &bdi->wb; - wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s", + wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s", dev_name(dev)); - if (IS_ERR(wb->task)) { - wb->task = NULL; - ret = -ENOMEM; - - bdi_remove_from_list(bdi); - goto exit; - } + if (IS_ERR(wb->task)) + return PTR_ERR(wb->task); } bdi_debug_register(bdi, dev_name(dev)); set_bit(BDI_registered, &bdi->state); -exit: - return ret; + + spin_lock_bh(&bdi_lock); + list_add_tail_rcu(&bdi->bdi_list, &bdi_list); + spin_unlock_bh(&bdi_lock); + + trace_writeback_bdi_register(bdi); + return 0; } EXPORT_SYMBOL(bdi_register); @@ -580,15 +566,15 @@ 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 @@ -620,7 +606,9 @@ static void bdi_prune_sb(struct backing_dev_info *bdi) void bdi_unregister(struct backing_dev_info *bdi) { if (bdi->dev) { + trace_writeback_bdi_unregister(bdi); bdi_prune_sb(bdi); + del_timer_sync(&bdi->wb.wakeup_timer); if (!bdi_cap_flush_forker(bdi)) bdi_wb_shutdown(bdi); @@ -631,6 +619,18 @@ void bdi_unregister(struct backing_dev_info *bdi) } EXPORT_SYMBOL(bdi_unregister); +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); + setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi); +} + int bdi_init(struct backing_dev_info *bdi) { int i, err; @@ -641,7 +641,6 @@ int bdi_init(struct backing_dev_info *bdi) bdi->max_ratio = 100; bdi->max_prop_frac = PROP_FRAC_BASE; spin_lock_init(&bdi->wb_lock); - INIT_RCU_HEAD(&bdi->rcu_head); INIT_LIST_HEAD(&bdi->bdi_list); INIT_LIST_HEAD(&bdi->work_list);