diff options
Diffstat (limited to 'mm/backing-dev.c')
| -rw-r--r-- | mm/backing-dev.c | 888 |
1 files changed, 888 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c new file mode 100644 index 00000000..dd8e2aaf --- /dev/null +++ b/mm/backing-dev.c @@ -0,0 +1,888 @@ + +#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> +#include <linux/device.h> +#include <trace/events/writeback.h> + +static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); + +struct backing_dev_info default_backing_dev_info = { + .name = "default", + .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE, + .state = 0, + .capabilities = BDI_CAP_MAP_COPY, +}; +EXPORT_SYMBOL_GPL(default_backing_dev_info); + +struct backing_dev_info noop_backing_dev_info = { + .name = "noop", + .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK, +}; +EXPORT_SYMBOL_GPL(noop_backing_dev_info); + +static struct class *bdi_class; + +/* + * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as + * reader side protection for bdi_pending_list. bdi_list has RCU reader side + * locking. + */ +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); + +void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2) +{ + if (wb1 < wb2) { + spin_lock(&wb1->list_lock); + spin_lock_nested(&wb2->list_lock, 1); + } else { + spin_lock(&wb2->list_lock); + spin_lock_nested(&wb1->list_lock, 1); + } +} + +#ifdef CONFIG_DEBUG_FS +#include <linux/debugfs.h> +#include <linux/seq_file.h> + +static struct dentry *bdi_debug_root; + +static void bdi_debug_init(void) +{ + bdi_debug_root = debugfs_create_dir("bdi", NULL); +} + +static int bdi_debug_stats_show(struct seq_file *m, void *v) +{ + struct backing_dev_info *bdi = m->private; + struct bdi_writeback *wb = &bdi->wb; + unsigned long background_thresh; + unsigned long dirty_thresh; + unsigned long bdi_thresh; + unsigned long nr_dirty, nr_io, nr_more_io; + struct inode *inode; + + nr_dirty = nr_io = nr_more_io = 0; + spin_lock(&wb->list_lock); + list_for_each_entry(inode, &wb->b_dirty, i_wb_list) + nr_dirty++; + list_for_each_entry(inode, &wb->b_io, i_wb_list) + nr_io++; + list_for_each_entry(inode, &wb->b_more_io, i_wb_list) + nr_more_io++; + spin_unlock(&wb->list_lock); + + global_dirty_limits(&background_thresh, &dirty_thresh); + bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); + +#define K(x) ((x) << (PAGE_SHIFT - 10)) + seq_printf(m, + "BdiWriteback: %10lu kB\n" + "BdiReclaimable: %10lu kB\n" + "BdiDirtyThresh: %10lu kB\n" + "DirtyThresh: %10lu kB\n" + "BackgroundThresh: %10lu kB\n" + "BdiDirtied: %10lu kB\n" + "BdiWritten: %10lu kB\n" + "BdiWriteBandwidth: %10lu kBps\n" + "b_dirty: %10lu\n" + "b_io: %10lu\n" + "b_more_io: %10lu\n" + "bdi_list: %10u\n" + "state: %10lx\n", + (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)), + (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)), + K(bdi_thresh), + K(dirty_thresh), + K(background_thresh), + (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)), + (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)), + (unsigned long) K(bdi->write_bandwidth), + nr_dirty, + nr_io, + nr_more_io, + !list_empty(&bdi->bdi_list), bdi->state); +#undef K + + return 0; +} + +static int bdi_debug_stats_open(struct inode *inode, struct file *file) +{ + return single_open(file, bdi_debug_stats_show, inode->i_private); +} + +static const struct file_operations bdi_debug_stats_fops = { + .open = bdi_debug_stats_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static void bdi_debug_register(struct backing_dev_info *bdi, const char *name) +{ + bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); + bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir, + bdi, &bdi_debug_stats_fops); +} + +static void bdi_debug_unregister(struct backing_dev_info *bdi) +{ + debugfs_remove(bdi->debug_stats); + debugfs_remove(bdi->debug_dir); +} +#else +static inline void bdi_debug_init(void) +{ +} +static inline void bdi_debug_register(struct backing_dev_info *bdi, + const char *name) +{ +} +static inline void bdi_debug_unregister(struct backing_dev_info *bdi) +{ +} +#endif + +static ssize_t read_ahead_kb_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct backing_dev_info *bdi = dev_get_drvdata(dev); + char *end; + unsigned long read_ahead_kb; + ssize_t ret = -EINVAL; + + read_ahead_kb = simple_strtoul(buf, &end, 10); + if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { + bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); + ret = count; + } + return ret; +} + +#define K(pages) ((pages) << (PAGE_SHIFT - 10)) + +#define BDI_SHOW(name, expr) \ +static ssize_t name##_show(struct device *dev, \ + struct device_attribute *attr, char *page) \ +{ \ + struct backing_dev_info *bdi = dev_get_drvdata(dev); \ + \ + return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \ +} + +BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) + +static ssize_t min_ratio_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + struct backing_dev_info *bdi = dev_get_drvdata(dev); + char *end; + unsigned int ratio; + ssize_t ret = -EINVAL; + + ratio = simple_strtoul(buf, &end, 10); + if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { + ret = bdi_set_min_ratio(bdi, ratio); + if (!ret) + ret = count; + } + return ret; +} +BDI_SHOW(min_ratio, bdi->min_ratio) + +static ssize_t max_ratio_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + struct backing_dev_info *bdi = dev_get_drvdata(dev); + char *end; + unsigned int ratio; + ssize_t ret = -EINVAL; + + ratio = simple_strtoul(buf, &end, 10); + if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { + ret = bdi_set_max_ratio(bdi, ratio); + if (!ret) + ret = count; + } + return ret; +} +BDI_SHOW(max_ratio, bdi->max_ratio) + +#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store) + +static struct device_attribute bdi_dev_attrs[] = { + __ATTR_RW(read_ahead_kb), + __ATTR_RW(min_ratio), + __ATTR_RW(max_ratio), + __ATTR_NULL, +}; + +static __init int bdi_class_init(void) +{ + bdi_class = class_create(THIS_MODULE, "bdi"); + if (IS_ERR(bdi_class)) + return PTR_ERR(bdi_class); + + bdi_class->dev_attrs = bdi_dev_attrs; + bdi_debug_init(); + return 0; +} +postcore_initcall(bdi_class_init); + +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)); + + setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0); + bdi_arm_supers_timer(); + + err = bdi_init(&default_backing_dev_info); + if (!err) + bdi_register(&default_backing_dev_info, NULL, "default"); + err = bdi_init(&noop_backing_dev_info); + + return err; +} +subsys_initcall(default_bdi_init); + +int bdi_has_dirty_io(struct backing_dev_info *bdi) +{ + return wb_has_dirty_io(&bdi->wb); +} + +/* + * 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 thread 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; +} + +void bdi_arm_supers_timer(void) +{ + unsigned long next; + + if (!dirty_writeback_interval) + return; + + 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); + bdi_arm_supers_timer(); +} + +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 if (bdi->dev) { + /* + * 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); +} + +/* + * Clear pending bit and wakeup anybody waiting for flusher thread creation or + * shutdown + */ +static void bdi_clear_pending(struct backing_dev_info *bdi) +{ + clear_bit(BDI_pending, &bdi->state); + smp_mb__after_clear_bit(); + wake_up_bit(&bdi->state, BDI_pending); +} + +static int bdi_forker_thread(void *ptr) +{ + struct bdi_writeback *me = ptr; + + current->flags |= PF_SWAPWRITE; + set_freezable(); + + /* + * Our parent may run at a different priority, just set us to normal + */ + set_user_nice(current, 0); + + for (;;) { + 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)) { + del_timer(&me->wakeup_timer); + wb_do_writeback(me, 0); + } + + spin_lock_bh(&bdi_lock); + /* + * In the following loop we are going to check whether we have + * some work to do without any synchronization with tasks + * waking us up to do work for them. Set the task state here + * so that we don't miss wakeups after verifying conditions. + */ + set_current_state(TASK_INTERRUPTIBLE); + + 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; + + WARN(!test_bit(BDI_registered, &bdi->state), + "bdi %p/%s is not registered!\n", bdi, bdi->name); + + have_dirty_io = !list_empty(&bdi->work_list) || + wb_has_dirty_io(&bdi->wb); + + /* + * 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); + + /* 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_create(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. Hopefully 1024 is + * large enough for efficient IO. + */ + writeback_inodes_wb(&bdi->wb, 1024, + WB_REASON_FORKER_THREAD); + } else { + /* + * The spinlock makes sure we do not lose + * wake-ups when racing with 'bdi_queue_work()'. + * And as soon as the bdi thread is visible, we + * can start it. + */ + spin_lock_bh(&bdi->wb_lock); + bdi->wb.task = task; + spin_unlock_bh(&bdi->wb_lock); + wake_up_process(task); + } + bdi_clear_pending(bdi); + break; + + case KILL_THREAD: + __set_current_state(TASK_RUNNING); + kthread_stop(task); + bdi_clear_pending(bdi); + 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_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); + try_to_freeze(); + break; + } + } + + return 0; +} + +/* + * Remove bdi from bdi_list, and ensure that it is no longer visible + */ +static void bdi_remove_from_list(struct backing_dev_info *bdi) +{ + spin_lock_bh(&bdi_lock); + list_del_rcu(&bdi->bdi_list); + spin_unlock_bh(&bdi_lock); + + synchronize_rcu_expedited(); +} + +int bdi_register(struct backing_dev_info *bdi, struct device *parent, + const char *fmt, ...) +{ + va_list args; + struct device *dev; + + if (bdi->dev) /* The driver needs to use separate queues per device */ + 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)) + return PTR_ERR(dev); + + bdi->dev = 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_thread, wb, "bdi-%s", + dev_name(dev)); + if (IS_ERR(wb->task)) + return PTR_ERR(wb->task); + } + + bdi_debug_register(bdi, dev_name(dev)); + set_bit(BDI_registered, &bdi->state); + + 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); + +int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev) +{ + return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev)); +} +EXPORT_SYMBOL(bdi_register_dev); + +/* + * Remove bdi from the global list and shutdown any threads we have running + */ +static void bdi_wb_shutdown(struct backing_dev_info *bdi) +{ + struct task_struct *task; + + if (!bdi_cap_writeback_dirty(bdi)) + return; + + /* + * Make sure nobody finds us on the bdi_list anymore + */ + bdi_remove_from_list(bdi); + + /* + * If setup is pending, wait for that to complete first + */ + wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait, + TASK_UNINTERRUPTIBLE); + + /* + * Finally, kill the kernel thread. We don't need to be RCU + * safe anymore, since the bdi is gone from visibility. + */ + spin_lock_bh(&bdi->wb_lock); + task = bdi->wb.task; + bdi->wb.task = NULL; + spin_unlock_bh(&bdi->wb_lock); + + if (task) + kthread_stop(task); +} + +/* + * This bdi is going away now, make sure that no super_blocks point to it + */ +static void bdi_prune_sb(struct backing_dev_info *bdi) +{ + struct super_block *sb; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_bdi == bdi) + sb->s_bdi = &default_backing_dev_info; + } + spin_unlock(&sb_lock); +} + +void bdi_unregister(struct backing_dev_info *bdi) +{ + struct device *dev = bdi->dev; + + if (dev) { + bdi_set_min_ratio(bdi, 0); + 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); + bdi_debug_unregister(bdi); + + spin_lock_bh(&bdi->wb_lock); + bdi->dev = NULL; + spin_unlock_bh(&bdi->wb_lock); + + device_unregister(dev); + } +} +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); + spin_lock_init(&wb->list_lock); + setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi); +} + +/* + * Initial write bandwidth: 100 MB/s + */ +#define INIT_BW (100 << (20 - PAGE_SHIFT)) + +int bdi_init(struct backing_dev_info *bdi) +{ + 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->work_list); + + bdi_wb_init(&bdi->wb, bdi); + + for (i = 0; i < NR_BDI_STAT_ITEMS; i++) { + err = percpu_counter_init(&bdi->bdi_stat[i], 0); + if (err) + goto err; + } + + bdi->dirty_exceeded = 0; + + bdi->bw_time_stamp = jiffies; + bdi->written_stamp = 0; + + bdi->balanced_dirty_ratelimit = INIT_BW; + bdi->dirty_ratelimit = INIT_BW; + bdi->write_bandwidth = INIT_BW; + bdi->avg_write_bandwidth = INIT_BW; + + err = prop_local_init_percpu(&bdi->completions); + + if (err) { +err: + while (i--) + percpu_counter_destroy(&bdi->bdi_stat[i]); + } + + return err; +} +EXPORT_SYMBOL(bdi_init); + +void bdi_destroy(struct backing_dev_info *bdi) +{ + int i; + + /* + * Splice our entries to the default_backing_dev_info, if this + * bdi disappears + */ + if (bdi_has_dirty_io(bdi)) { + struct bdi_writeback *dst = &default_backing_dev_info.wb; + + bdi_lock_two(&bdi->wb, dst); + list_splice(&bdi->wb.b_dirty, &dst->b_dirty); + list_splice(&bdi->wb.b_io, &dst->b_io); + list_splice(&bdi->wb.b_more_io, &dst->b_more_io); + spin_unlock(&bdi->wb.list_lock); + spin_unlock(&dst->list_lock); + } + + bdi_unregister(bdi); + + /* + * If bdi_unregister() had already been called earlier, the + * wakeup_timer could still be armed because bdi_prune_sb() + * can race with the bdi_wakeup_thread_delayed() calls from + * __mark_inode_dirty(). + */ + del_timer_sync(&bdi->wb.wakeup_timer); + + for (i = 0; i < NR_BDI_STAT_ITEMS; i++) + percpu_counter_destroy(&bdi->bdi_stat[i]); + + prop_local_destroy_percpu(&bdi->completions); +} +EXPORT_SYMBOL(bdi_destroy); + +/* + * For use from filesystems to quickly init and register a bdi associated + * with dirty writeback + */ +int bdi_setup_and_register(struct backing_dev_info *bdi, char *name, + unsigned int cap) +{ + char tmp[32]; + int err; + + bdi->name = name; + bdi->capabilities = cap; + err = bdi_init(bdi); + if (err) + return err; + + sprintf(tmp, "%.28s%s", name, "-%d"); + err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq)); + if (err) { + bdi_destroy(bdi); + return err; + } + + return 0; +} +EXPORT_SYMBOL(bdi_setup_and_register); + +static wait_queue_head_t congestion_wqh[2] = { + __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]), + __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1]) + }; +static atomic_t nr_bdi_congested[2]; + +void clear_bdi_congested(struct backing_dev_info *bdi, int sync) +{ + enum bdi_state bit; + wait_queue_head_t *wqh = &congestion_wqh[sync]; + + bit = sync ? BDI_sync_congested : BDI_async_congested; + if (test_and_clear_bit(bit, &bdi->state)) + atomic_dec(&nr_bdi_congested[sync]); + smp_mb__after_clear_bit(); + if (waitqueue_active(wqh)) + wake_up(wqh); +} +EXPORT_SYMBOL(clear_bdi_congested); + +void set_bdi_congested(struct backing_dev_info *bdi, int sync) +{ + enum bdi_state bit; + + bit = sync ? BDI_sync_congested : BDI_async_congested; + if (!test_and_set_bit(bit, &bdi->state)) + atomic_inc(&nr_bdi_congested[sync]); +} +EXPORT_SYMBOL(set_bdi_congested); + +/** + * congestion_wait - wait for a backing_dev to become uncongested + * @sync: SYNC or ASYNC IO + * @timeout: timeout in jiffies + * + * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit + * write congestion. If no backing_devs are congested then just wait for the + * next write to be completed. + */ +long congestion_wait(int sync, long timeout) +{ + long ret; + unsigned long start = jiffies; + DEFINE_WAIT(wait); + wait_queue_head_t *wqh = &congestion_wqh[sync]; + + prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); + ret = io_schedule_timeout(timeout); + finish_wait(wqh, &wait); + + trace_writeback_congestion_wait(jiffies_to_usecs(timeout), + jiffies_to_usecs(jiffies - start)); + + return ret; +} +EXPORT_SYMBOL(congestion_wait); + +/** + * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes + * @zone: A zone to check if it is heavily congested + * @sync: SYNC or ASYNC IO + * @timeout: timeout in jiffies + * + * In the event of a congested backing_dev (any backing_dev) and the given + * @zone has experienced recent congestion, this waits for up to @timeout + * jiffies for either a BDI to exit congestion of the given @sync queue + * or a write to complete. + * + * In the absence of zone congestion, cond_resched() is called to yield + * the processor if necessary but otherwise does not sleep. + * + * The return value is 0 if the sleep is for the full timeout. Otherwise, + * it is the number of jiffies that were still remaining when the function + * returned. return_value == timeout implies the function did not sleep. + */ +long wait_iff_congested(struct zone *zone, int sync, long timeout) +{ + long ret; + unsigned long start = jiffies; + DEFINE_WAIT(wait); + wait_queue_head_t *wqh = &congestion_wqh[sync]; + + /* + * If there is no congestion, or heavy congestion is not being + * encountered in the current zone, yield if necessary instead + * of sleeping on the congestion queue + */ + if (atomic_read(&nr_bdi_congested[sync]) == 0 || + !zone_is_reclaim_congested(zone)) { + cond_resched(); + + /* In case we scheduled, work out time remaining */ + ret = timeout - (jiffies - start); + if (ret < 0) + ret = 0; + + goto out; + } + + /* Sleep until uncongested or a write happens */ + prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); + ret = io_schedule_timeout(timeout); + finish_wait(wqh, &wait); + +out: + trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout), + jiffies_to_usecs(jiffies - start)); + + return ret; +} +EXPORT_SYMBOL(wait_iff_congested); |