--- /dev/null
+
+#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 noop_backing_dev_info = {
+ .name = "noop",
+ .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
+};
+
+static struct class *bdi_class;
+
+/*
+ * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
+ * locking.
+ */
+DEFINE_SPINLOCK(bdi_lock);
+LIST_HEAD(bdi_list);
+
+/* bdi_wq serves all asynchronous writeback tasks */
+struct workqueue_struct *bdi_wq;
+
+#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, nr_dirty_time;
+ struct inode *inode;
+
+ nr_dirty = nr_io = nr_more_io = nr_dirty_time = 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++;
+ list_for_each_entry(inode, &wb->b_dirty_time, i_wb_list)
+ if (inode->i_state & I_DIRTY_TIME)
+ nr_dirty_time++;
+ 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"
+ "b_dirty_time: %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,
+ nr_dirty_time,
+ !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);
+ unsigned long read_ahead_kb;
+ ssize_t ret;
+
+ ret = kstrtoul(buf, 10, &read_ahead_kb);
+ if (ret < 0)
+ return ret;
+
+ bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
+
+ return count;
+}
+
+#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); \
+} \
+static DEVICE_ATTR_RW(name);
+
+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);
+ unsigned int ratio;
+ ssize_t ret;
+
+ ret = kstrtouint(buf, 10, &ratio);
+ if (ret < 0)
+ return ret;
+
+ 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);
+ unsigned int ratio;
+ ssize_t ret;
+
+ ret = kstrtouint(buf, 10, &ratio);
+ if (ret < 0)
+ return ret;
+
+ ret = bdi_set_max_ratio(bdi, ratio);
+ if (!ret)
+ ret = count;
+
+ return ret;
+}
+BDI_SHOW(max_ratio, bdi->max_ratio)
+
+static ssize_t stable_pages_required_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, "%d\n",
+ bdi_cap_stable_pages_required(bdi) ? 1 : 0);
+}
+static DEVICE_ATTR_RO(stable_pages_required);
+
+static struct attribute *bdi_dev_attrs[] = {
+ &dev_attr_read_ahead_kb.attr,
+ &dev_attr_min_ratio.attr,
+ &dev_attr_max_ratio.attr,
+ &dev_attr_stable_pages_required.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(bdi_dev);
+
+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_groups = bdi_dev_groups;
+ bdi_debug_init();
+ return 0;
+}
+postcore_initcall(bdi_class_init);
+
+static int __init default_bdi_init(void)
+{
+ int err;
+
+ bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
+ WQ_UNBOUND | WQ_SYSFS, 0);
+ if (!bdi_wq)
+ return -ENOMEM;
+
+ 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);
+}
+
+/*
+ * 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.
+ *
+ * We have to be careful not to postpone flush work if it is scheduled for
+ * earlier. Thus we use queue_delayed_work().
+ */
+void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
+{
+ unsigned long timeout;
+
+ timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ spin_lock_bh(&bdi->wb_lock);
+ if (test_bit(BDI_registered, &bdi->state))
+ queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
+ spin_unlock_bh(&bdi->wb_lock);
+}
+
+/*
+ * 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;
+
+ 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)
+{
+ /* Make sure nobody queues further work */
+ spin_lock_bh(&bdi->wb_lock);
+ if (!test_and_clear_bit(BDI_registered, &bdi->state)) {
+ spin_unlock_bh(&bdi->wb_lock);
+ return;
+ }
+ spin_unlock_bh(&bdi->wb_lock);
+
+ /*
+ * Make sure nobody finds us on the bdi_list anymore
+ */
+ bdi_remove_from_list(bdi);
+
+ /*
+ * Drain work list and shutdown the delayed_work. At this point,
+ * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
+ * is dying and its work_list needs to be drained no matter what.
+ */
+ mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+ flush_delayed_work(&bdi->wb.dwork);
+}
+
+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);
+ INIT_LIST_HEAD(&wb->b_dirty_time);
+ spin_lock_init(&wb->list_lock);
+ INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
+}
+
+/*
+ * 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 = FPROP_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, GFP_KERNEL);
+ 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 = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
+
+ 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;
+
+ bdi_wb_shutdown(bdi);
+ bdi_set_min_ratio(bdi, 0);
+
+ WARN_ON(!list_empty(&bdi->work_list));
+ WARN_ON(delayed_work_pending(&bdi->wb.dwork));
+
+ if (bdi->dev) {
+ bdi_debug_unregister(bdi);
+ device_unregister(bdi->dev);
+ bdi->dev = NULL;
+ }
+
+ for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
+ percpu_counter_destroy(&bdi->bdi_stat[i]);
+ fprop_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)
+{
+ int err;
+
+ bdi->name = name;
+ bdi->capabilities = 0;
+ err = bdi_init(bdi);
+ if (err)
+ return err;
+
+ err = bdi_register(bdi, NULL, "%.28s-%ld", name,
+ 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_atomic();
+ 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 ||
+ !test_bit(ZONE_CONGESTED, &zone->flags)) {
+ 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);
+
+int pdflush_proc_obsolete(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ char kbuf[] = "0\n";
+
+ if (*ppos || *lenp < sizeof(kbuf)) {
+ *lenp = 0;
+ return 0;
+ }
+
+ if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
+ return -EFAULT;
+ printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
+ table->procname);
+
+ *lenp = 2;
+ *ppos += *lenp;
+ return 2;
+}
Code Review / kvmfornfv.git / blobdiff