#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>
-int bdi_init(struct backing_dev_info *bdi)
+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"
+ "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_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 i, j;
int err;
- for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
- err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
- if (err) {
- for (j = 0; j < i; j++)
- percpu_counter_destroy(&bdi->bdi_stat[i]);
+ 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 {
+ /*
+ * 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;
+
+ 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);
+ 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);
+ } 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);
+ }
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_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
+ try_to_freeze();
+ /* 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;
+}
+
+/*
+ * 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)
+{
+ 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. Force
+ * unfreeze of the thread before calling kthread_stop(), otherwise
+ * it would never exet if it is currently stuck in the refrigerator.
+ */
+ if (bdi->wb.task) {
+ thaw_process(bdi->wb.task);
+ kthread_stop(bdi->wb.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)
+{
+ if (bdi->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);
+ device_unregister(bdi->dev);
+ bdi->dev = NULL;
+ }
+}
+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->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;
{
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);
+
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 rw)
+void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
enum bdi_state bit;
- wait_queue_head_t *wqh = &congestion_wqh[rw];
+ wait_queue_head_t *wqh = &congestion_wqh[sync];
- bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
- clear_bit(bit, &bdi->state);
+ 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 rw)
+void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
enum bdi_state bit;
- bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
- set_bit(bit, &bdi->state);
+ 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
- * @rw: READ or WRITE
+ * @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 rw, long timeout)
+long congestion_wait(int sync, long timeout)
{
long ret;
+ unsigned long start = jiffies;
DEFINE_WAIT(wait);
- wait_queue_head_t *wqh = &congestion_wqh[rw];
+ 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);
Code Review / linux-2.6.git / blobdiff