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-rw-r--r--mm/backing-dev.c1003
1 files changed, 1003 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
new file mode 100644
index 000000000..bf5525c2e
--- /dev/null
+++ b/mm/backing-dev.c
@@ -0,0 +1,1003 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/blkdev.h>
+#include <linux/wait.h>
+#include <linux/rbtree.h>
+#include <linux/kthread.h>
+#include <linux/backing-dev.h>
+#include <linux/blk-cgroup.h>
+#include <linux/freezer.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/writeback.h>
+#include <linux/device.h>
+#include <trace/events/writeback.h>
+
+struct backing_dev_info noop_backing_dev_info;
+EXPORT_SYMBOL_GPL(noop_backing_dev_info);
+
+static struct class *bdi_class;
+static const char *bdi_unknown_name = "(unknown)";
+
+/*
+ * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
+ * reader side locking.
+ */
+DEFINE_SPINLOCK(bdi_lock);
+static u64 bdi_id_cursor;
+static struct rb_root bdi_tree = RB_ROOT;
+LIST_HEAD(bdi_list);
+
+/* bdi_wq serves all asynchronous writeback tasks */
+struct workqueue_struct *bdi_wq;
+
+#define K(x) ((x) << (PAGE_SHIFT - 10))
+
+#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 wb_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_io_list)
+ nr_dirty++;
+ list_for_each_entry(inode, &wb->b_io, i_io_list)
+ nr_io++;
+ list_for_each_entry(inode, &wb->b_more_io, i_io_list)
+ nr_more_io++;
+ list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
+ if (inode->i_state & I_DIRTY_TIME)
+ nr_dirty_time++;
+ spin_unlock(&wb->list_lock);
+
+ global_dirty_limits(&background_thresh, &dirty_thresh);
+ wb_thresh = wb_calc_thresh(wb, dirty_thresh);
+
+ 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(wb_stat(wb, WB_WRITEBACK)),
+ (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
+ K(wb_thresh),
+ K(dirty_thresh),
+ K(background_thresh),
+ (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
+ (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
+ (unsigned long) K(wb->write_bandwidth),
+ nr_dirty,
+ nr_io,
+ nr_more_io,
+ nr_dirty_time,
+ !list_empty(&bdi->bdi_list), bdi->wb.state);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
+
+static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
+{
+ bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
+
+ 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_recursive(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 BDI_SHOW(name, expr) \
+static ssize_t name##_show(struct device *dev, \
+ struct device_attribute *attr, char *buf) \
+{ \
+ struct backing_dev_info *bdi = dev_get_drvdata(dev); \
+ \
+ return sysfs_emit(buf, "%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 *buf)
+{
+ dev_warn_once(dev,
+ "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
+ return sysfs_emit(buf, "%d\n", 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)
+{
+ bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
+ WQ_SYSFS, 0);
+ if (!bdi_wq)
+ return -ENOMEM;
+ return 0;
+}
+subsys_initcall(default_bdi_init);
+
+/*
+ * This function is used when the first inode for this wb 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 wb_wakeup_delayed(struct bdi_writeback *wb)
+{
+ unsigned long timeout;
+
+ timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ spin_lock_irq(&wb->work_lock);
+ if (test_bit(WB_registered, &wb->state))
+ queue_delayed_work(bdi_wq, &wb->dwork, timeout);
+ spin_unlock_irq(&wb->work_lock);
+}
+
+static void wb_update_bandwidth_workfn(struct work_struct *work)
+{
+ struct bdi_writeback *wb = container_of(to_delayed_work(work),
+ struct bdi_writeback, bw_dwork);
+
+ wb_update_bandwidth(wb);
+}
+
+/*
+ * Initial write bandwidth: 100 MB/s
+ */
+#define INIT_BW (100 << (20 - PAGE_SHIFT))
+
+static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
+ gfp_t gfp)
+{
+ int i, err;
+
+ 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);
+
+ atomic_set(&wb->writeback_inodes, 0);
+ wb->bw_time_stamp = jiffies;
+ wb->balanced_dirty_ratelimit = INIT_BW;
+ wb->dirty_ratelimit = INIT_BW;
+ wb->write_bandwidth = INIT_BW;
+ wb->avg_write_bandwidth = INIT_BW;
+
+ spin_lock_init(&wb->work_lock);
+ INIT_LIST_HEAD(&wb->work_list);
+ INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
+ INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
+ wb->dirty_sleep = jiffies;
+
+ err = fprop_local_init_percpu(&wb->completions, gfp);
+ if (err)
+ return err;
+
+ for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
+ err = percpu_counter_init(&wb->stat[i], 0, gfp);
+ if (err)
+ goto out_destroy_stat;
+ }
+
+ return 0;
+
+out_destroy_stat:
+ while (i--)
+ percpu_counter_destroy(&wb->stat[i]);
+ fprop_local_destroy_percpu(&wb->completions);
+ return err;
+}
+
+static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
+
+/*
+ * Remove bdi from the global list and shutdown any threads we have running
+ */
+static void wb_shutdown(struct bdi_writeback *wb)
+{
+ /* Make sure nobody queues further work */
+ spin_lock_irq(&wb->work_lock);
+ if (!test_and_clear_bit(WB_registered, &wb->state)) {
+ spin_unlock_irq(&wb->work_lock);
+ return;
+ }
+ spin_unlock_irq(&wb->work_lock);
+
+ cgwb_remove_from_bdi_list(wb);
+ /*
+ * Drain work list and shutdown the delayed_work. !WB_registered
+ * tells wb_workfn() that @wb is dying and its work_list needs to
+ * be drained no matter what.
+ */
+ mod_delayed_work(bdi_wq, &wb->dwork, 0);
+ flush_delayed_work(&wb->dwork);
+ WARN_ON(!list_empty(&wb->work_list));
+ flush_delayed_work(&wb->bw_dwork);
+}
+
+static void wb_exit(struct bdi_writeback *wb)
+{
+ int i;
+
+ WARN_ON(delayed_work_pending(&wb->dwork));
+
+ for (i = 0; i < NR_WB_STAT_ITEMS; i++)
+ percpu_counter_destroy(&wb->stat[i]);
+
+ fprop_local_destroy_percpu(&wb->completions);
+}
+
+#ifdef CONFIG_CGROUP_WRITEBACK
+
+#include <linux/memcontrol.h>
+
+/*
+ * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
+ * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
+ */
+static DEFINE_SPINLOCK(cgwb_lock);
+static struct workqueue_struct *cgwb_release_wq;
+
+static LIST_HEAD(offline_cgwbs);
+static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
+static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
+
+static void cgwb_free_rcu(struct rcu_head *rcu_head)
+{
+ struct bdi_writeback *wb = container_of(rcu_head,
+ struct bdi_writeback, rcu);
+
+ percpu_ref_exit(&wb->refcnt);
+ kfree(wb);
+}
+
+static void cgwb_release_workfn(struct work_struct *work)
+{
+ struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
+ release_work);
+ struct backing_dev_info *bdi = wb->bdi;
+
+ mutex_lock(&wb->bdi->cgwb_release_mutex);
+ wb_shutdown(wb);
+
+ css_put(wb->memcg_css);
+ css_put(wb->blkcg_css);
+ mutex_unlock(&wb->bdi->cgwb_release_mutex);
+
+ /* triggers blkg destruction if no online users left */
+ blkcg_unpin_online(wb->blkcg_css);
+
+ fprop_local_destroy_percpu(&wb->memcg_completions);
+
+ spin_lock_irq(&cgwb_lock);
+ list_del(&wb->offline_node);
+ spin_unlock_irq(&cgwb_lock);
+
+ wb_exit(wb);
+ bdi_put(bdi);
+ WARN_ON_ONCE(!list_empty(&wb->b_attached));
+ call_rcu(&wb->rcu, cgwb_free_rcu);
+}
+
+static void cgwb_release(struct percpu_ref *refcnt)
+{
+ struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
+ refcnt);
+ queue_work(cgwb_release_wq, &wb->release_work);
+}
+
+static void cgwb_kill(struct bdi_writeback *wb)
+{
+ lockdep_assert_held(&cgwb_lock);
+
+ WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
+ list_del(&wb->memcg_node);
+ list_del(&wb->blkcg_node);
+ list_add(&wb->offline_node, &offline_cgwbs);
+ percpu_ref_kill(&wb->refcnt);
+}
+
+static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
+{
+ spin_lock_irq(&cgwb_lock);
+ list_del_rcu(&wb->bdi_node);
+ spin_unlock_irq(&cgwb_lock);
+}
+
+static int cgwb_create(struct backing_dev_info *bdi,
+ struct cgroup_subsys_state *memcg_css, gfp_t gfp)
+{
+ struct mem_cgroup *memcg;
+ struct cgroup_subsys_state *blkcg_css;
+ struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
+ struct bdi_writeback *wb;
+ unsigned long flags;
+ int ret = 0;
+
+ memcg = mem_cgroup_from_css(memcg_css);
+ blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
+ memcg_cgwb_list = &memcg->cgwb_list;
+ blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
+
+ /* look up again under lock and discard on blkcg mismatch */
+ spin_lock_irqsave(&cgwb_lock, flags);
+ wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ if (wb && wb->blkcg_css != blkcg_css) {
+ cgwb_kill(wb);
+ wb = NULL;
+ }
+ spin_unlock_irqrestore(&cgwb_lock, flags);
+ if (wb)
+ goto out_put;
+
+ /* need to create a new one */
+ wb = kmalloc(sizeof(*wb), gfp);
+ if (!wb) {
+ ret = -ENOMEM;
+ goto out_put;
+ }
+
+ ret = wb_init(wb, bdi, gfp);
+ if (ret)
+ goto err_free;
+
+ ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
+ if (ret)
+ goto err_wb_exit;
+
+ ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
+ if (ret)
+ goto err_ref_exit;
+
+ wb->memcg_css = memcg_css;
+ wb->blkcg_css = blkcg_css;
+ INIT_LIST_HEAD(&wb->b_attached);
+ INIT_WORK(&wb->release_work, cgwb_release_workfn);
+ set_bit(WB_registered, &wb->state);
+ bdi_get(bdi);
+
+ /*
+ * The root wb determines the registered state of the whole bdi and
+ * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
+ * whether they're still online. Don't link @wb if any is dead.
+ * See wb_memcg_offline() and wb_blkcg_offline().
+ */
+ ret = -ENODEV;
+ spin_lock_irqsave(&cgwb_lock, flags);
+ if (test_bit(WB_registered, &bdi->wb.state) &&
+ blkcg_cgwb_list->next && memcg_cgwb_list->next) {
+ /* we might have raced another instance of this function */
+ ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
+ if (!ret) {
+ list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
+ list_add(&wb->memcg_node, memcg_cgwb_list);
+ list_add(&wb->blkcg_node, blkcg_cgwb_list);
+ blkcg_pin_online(blkcg_css);
+ css_get(memcg_css);
+ css_get(blkcg_css);
+ }
+ }
+ spin_unlock_irqrestore(&cgwb_lock, flags);
+ if (ret) {
+ if (ret == -EEXIST)
+ ret = 0;
+ goto err_fprop_exit;
+ }
+ goto out_put;
+
+err_fprop_exit:
+ bdi_put(bdi);
+ fprop_local_destroy_percpu(&wb->memcg_completions);
+err_ref_exit:
+ percpu_ref_exit(&wb->refcnt);
+err_wb_exit:
+ wb_exit(wb);
+err_free:
+ kfree(wb);
+out_put:
+ css_put(blkcg_css);
+ return ret;
+}
+
+/**
+ * wb_get_lookup - get wb for a given memcg
+ * @bdi: target bdi
+ * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
+ *
+ * Try to get the wb for @memcg_css on @bdi. The returned wb has its
+ * refcount incremented.
+ *
+ * This function uses css_get() on @memcg_css and thus expects its refcnt
+ * to be positive on invocation. IOW, rcu_read_lock() protection on
+ * @memcg_css isn't enough. try_get it before calling this function.
+ *
+ * A wb is keyed by its associated memcg. As blkcg implicitly enables
+ * memcg on the default hierarchy, memcg association is guaranteed to be
+ * more specific (equal or descendant to the associated blkcg) and thus can
+ * identify both the memcg and blkcg associations.
+ *
+ * Because the blkcg associated with a memcg may change as blkcg is enabled
+ * and disabled closer to root in the hierarchy, each wb keeps track of
+ * both the memcg and blkcg associated with it and verifies the blkcg on
+ * each lookup. On mismatch, the existing wb is discarded and a new one is
+ * created.
+ */
+struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
+ struct cgroup_subsys_state *memcg_css)
+{
+ struct bdi_writeback *wb;
+
+ if (!memcg_css->parent)
+ return &bdi->wb;
+
+ rcu_read_lock();
+ wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ if (wb) {
+ struct cgroup_subsys_state *blkcg_css;
+
+ /* see whether the blkcg association has changed */
+ blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
+ if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
+ wb = NULL;
+ css_put(blkcg_css);
+ }
+ rcu_read_unlock();
+
+ return wb;
+}
+
+/**
+ * wb_get_create - get wb for a given memcg, create if necessary
+ * @bdi: target bdi
+ * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
+ * @gfp: allocation mask to use
+ *
+ * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
+ * create one. See wb_get_lookup() for more details.
+ */
+struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
+ struct cgroup_subsys_state *memcg_css,
+ gfp_t gfp)
+{
+ struct bdi_writeback *wb;
+
+ might_alloc(gfp);
+
+ if (!memcg_css->parent)
+ return &bdi->wb;
+
+ do {
+ wb = wb_get_lookup(bdi, memcg_css);
+ } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
+
+ return wb;
+}
+
+static int cgwb_bdi_init(struct backing_dev_info *bdi)
+{
+ int ret;
+
+ INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
+ mutex_init(&bdi->cgwb_release_mutex);
+ init_rwsem(&bdi->wb_switch_rwsem);
+
+ ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
+ if (!ret) {
+ bdi->wb.memcg_css = &root_mem_cgroup->css;
+ bdi->wb.blkcg_css = blkcg_root_css;
+ }
+ return ret;
+}
+
+static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ struct bdi_writeback *wb;
+
+ WARN_ON(test_bit(WB_registered, &bdi->wb.state));
+
+ spin_lock_irq(&cgwb_lock);
+ radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
+ cgwb_kill(*slot);
+ spin_unlock_irq(&cgwb_lock);
+
+ mutex_lock(&bdi->cgwb_release_mutex);
+ spin_lock_irq(&cgwb_lock);
+ while (!list_empty(&bdi->wb_list)) {
+ wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
+ bdi_node);
+ spin_unlock_irq(&cgwb_lock);
+ wb_shutdown(wb);
+ spin_lock_irq(&cgwb_lock);
+ }
+ spin_unlock_irq(&cgwb_lock);
+ mutex_unlock(&bdi->cgwb_release_mutex);
+}
+
+/*
+ * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
+ *
+ * Try to release dying cgwbs by switching attached inodes to the nearest
+ * living ancestor's writeback. Processed wbs are placed at the end
+ * of the list to guarantee the forward progress.
+ */
+static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
+{
+ struct bdi_writeback *wb;
+ LIST_HEAD(processed);
+
+ spin_lock_irq(&cgwb_lock);
+
+ while (!list_empty(&offline_cgwbs)) {
+ wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
+ offline_node);
+ list_move(&wb->offline_node, &processed);
+
+ /*
+ * If wb is dirty, cleaning up the writeback by switching
+ * attached inodes will result in an effective removal of any
+ * bandwidth restrictions, which isn't the goal. Instead,
+ * it can be postponed until the next time, when all io
+ * will be likely completed. If in the meantime some inodes
+ * will get re-dirtied, they should be eventually switched to
+ * a new cgwb.
+ */
+ if (wb_has_dirty_io(wb))
+ continue;
+
+ if (!wb_tryget(wb))
+ continue;
+
+ spin_unlock_irq(&cgwb_lock);
+ while (cleanup_offline_cgwb(wb))
+ cond_resched();
+ spin_lock_irq(&cgwb_lock);
+
+ wb_put(wb);
+ }
+
+ if (!list_empty(&processed))
+ list_splice_tail(&processed, &offline_cgwbs);
+
+ spin_unlock_irq(&cgwb_lock);
+}
+
+/**
+ * wb_memcg_offline - kill all wb's associated with a memcg being offlined
+ * @memcg: memcg being offlined
+ *
+ * Also prevents creation of any new wb's associated with @memcg.
+ */
+void wb_memcg_offline(struct mem_cgroup *memcg)
+{
+ struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
+ struct bdi_writeback *wb, *next;
+
+ spin_lock_irq(&cgwb_lock);
+ list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
+ cgwb_kill(wb);
+ memcg_cgwb_list->next = NULL; /* prevent new wb's */
+ spin_unlock_irq(&cgwb_lock);
+
+ queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
+}
+
+/**
+ * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
+ * @css: blkcg being offlined
+ *
+ * Also prevents creation of any new wb's associated with @blkcg.
+ */
+void wb_blkcg_offline(struct cgroup_subsys_state *css)
+{
+ struct bdi_writeback *wb, *next;
+ struct list_head *list = blkcg_get_cgwb_list(css);
+
+ spin_lock_irq(&cgwb_lock);
+ list_for_each_entry_safe(wb, next, list, blkcg_node)
+ cgwb_kill(wb);
+ list->next = NULL; /* prevent new wb's */
+ spin_unlock_irq(&cgwb_lock);
+}
+
+static void cgwb_bdi_register(struct backing_dev_info *bdi)
+{
+ spin_lock_irq(&cgwb_lock);
+ list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
+ spin_unlock_irq(&cgwb_lock);
+}
+
+static int __init cgwb_init(void)
+{
+ /*
+ * There can be many concurrent release work items overwhelming
+ * system_wq. Put them in a separate wq and limit concurrency.
+ * There's no point in executing many of these in parallel.
+ */
+ cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
+ if (!cgwb_release_wq)
+ return -ENOMEM;
+
+ return 0;
+}
+subsys_initcall(cgwb_init);
+
+#else /* CONFIG_CGROUP_WRITEBACK */
+
+static int cgwb_bdi_init(struct backing_dev_info *bdi)
+{
+ return wb_init(&bdi->wb, bdi, GFP_KERNEL);
+}
+
+static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
+
+static void cgwb_bdi_register(struct backing_dev_info *bdi)
+{
+ list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
+}
+
+static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
+{
+ list_del_rcu(&wb->bdi_node);
+}
+
+#endif /* CONFIG_CGROUP_WRITEBACK */
+
+int bdi_init(struct backing_dev_info *bdi)
+{
+ bdi->dev = NULL;
+
+ kref_init(&bdi->refcnt);
+ bdi->min_ratio = 0;
+ bdi->max_ratio = 100;
+ bdi->max_prop_frac = FPROP_FRAC_BASE;
+ INIT_LIST_HEAD(&bdi->bdi_list);
+ INIT_LIST_HEAD(&bdi->wb_list);
+ init_waitqueue_head(&bdi->wb_waitq);
+
+ return cgwb_bdi_init(bdi);
+}
+
+struct backing_dev_info *bdi_alloc(int node_id)
+{
+ struct backing_dev_info *bdi;
+
+ bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
+ if (!bdi)
+ return NULL;
+
+ if (bdi_init(bdi)) {
+ kfree(bdi);
+ return NULL;
+ }
+ bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
+ bdi->ra_pages = VM_READAHEAD_PAGES;
+ bdi->io_pages = VM_READAHEAD_PAGES;
+ timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
+ return bdi;
+}
+EXPORT_SYMBOL(bdi_alloc);
+
+static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
+{
+ struct rb_node **p = &bdi_tree.rb_node;
+ struct rb_node *parent = NULL;
+ struct backing_dev_info *bdi;
+
+ lockdep_assert_held(&bdi_lock);
+
+ while (*p) {
+ parent = *p;
+ bdi = rb_entry(parent, struct backing_dev_info, rb_node);
+
+ if (bdi->id > id)
+ p = &(*p)->rb_left;
+ else if (bdi->id < id)
+ p = &(*p)->rb_right;
+ else
+ break;
+ }
+
+ if (parentp)
+ *parentp = parent;
+ return p;
+}
+
+/**
+ * bdi_get_by_id - lookup and get bdi from its id
+ * @id: bdi id to lookup
+ *
+ * Find bdi matching @id and get it. Returns NULL if the matching bdi
+ * doesn't exist or is already unregistered.
+ */
+struct backing_dev_info *bdi_get_by_id(u64 id)
+{
+ struct backing_dev_info *bdi = NULL;
+ struct rb_node **p;
+
+ spin_lock_bh(&bdi_lock);
+ p = bdi_lookup_rb_node(id, NULL);
+ if (*p) {
+ bdi = rb_entry(*p, struct backing_dev_info, rb_node);
+ bdi_get(bdi);
+ }
+ spin_unlock_bh(&bdi_lock);
+
+ return bdi;
+}
+
+int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
+{
+ struct device *dev;
+ struct rb_node *parent, **p;
+
+ if (bdi->dev) /* The driver needs to use separate queues per device */
+ return 0;
+
+ vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
+ dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
+ if (IS_ERR(dev))
+ return PTR_ERR(dev);
+
+ cgwb_bdi_register(bdi);
+ bdi->dev = dev;
+
+ bdi_debug_register(bdi, dev_name(dev));
+ set_bit(WB_registered, &bdi->wb.state);
+
+ spin_lock_bh(&bdi_lock);
+
+ bdi->id = ++bdi_id_cursor;
+
+ p = bdi_lookup_rb_node(bdi->id, &parent);
+ rb_link_node(&bdi->rb_node, parent, p);
+ rb_insert_color(&bdi->rb_node, &bdi_tree);
+
+ list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
+
+ spin_unlock_bh(&bdi_lock);
+
+ trace_writeback_bdi_register(bdi);
+ return 0;
+}
+
+int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
+{
+ va_list args;
+ int ret;
+
+ va_start(args, fmt);
+ ret = bdi_register_va(bdi, fmt, args);
+ va_end(args);
+ return ret;
+}
+EXPORT_SYMBOL(bdi_register);
+
+void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
+{
+ WARN_ON_ONCE(bdi->owner);
+ bdi->owner = owner;
+ get_device(owner);
+}
+
+/*
+ * 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);
+ rb_erase(&bdi->rb_node, &bdi_tree);
+ list_del_rcu(&bdi->bdi_list);
+ spin_unlock_bh(&bdi_lock);
+
+ synchronize_rcu_expedited();
+}
+
+void bdi_unregister(struct backing_dev_info *bdi)
+{
+ del_timer_sync(&bdi->laptop_mode_wb_timer);
+
+ /* make sure nobody finds us on the bdi_list anymore */
+ bdi_remove_from_list(bdi);
+ wb_shutdown(&bdi->wb);
+ cgwb_bdi_unregister(bdi);
+
+ /*
+ * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
+ * update the global bdi_min_ratio.
+ */
+ if (bdi->min_ratio)
+ bdi_set_min_ratio(bdi, 0);
+
+ if (bdi->dev) {
+ bdi_debug_unregister(bdi);
+ device_unregister(bdi->dev);
+ bdi->dev = NULL;
+ }
+
+ if (bdi->owner) {
+ put_device(bdi->owner);
+ bdi->owner = NULL;
+ }
+}
+EXPORT_SYMBOL(bdi_unregister);
+
+static void release_bdi(struct kref *ref)
+{
+ struct backing_dev_info *bdi =
+ container_of(ref, struct backing_dev_info, refcnt);
+
+ WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
+ WARN_ON_ONCE(bdi->dev);
+ wb_exit(&bdi->wb);
+ kfree(bdi);
+}
+
+void bdi_put(struct backing_dev_info *bdi)
+{
+ kref_put(&bdi->refcnt, release_bdi);
+}
+EXPORT_SYMBOL(bdi_put);
+
+struct backing_dev_info *inode_to_bdi(struct inode *inode)
+{
+ struct super_block *sb;
+
+ if (!inode)
+ return &noop_backing_dev_info;
+
+ sb = inode->i_sb;
+#ifdef CONFIG_BLOCK
+ if (sb_is_blkdev_sb(sb))
+ return I_BDEV(inode)->bd_disk->bdi;
+#endif
+ return sb->s_bdi;
+}
+EXPORT_SYMBOL(inode_to_bdi);
+
+const char *bdi_dev_name(struct backing_dev_info *bdi)
+{
+ if (!bdi || !bdi->dev)
+ return bdi_unknown_name;
+ return bdi->dev_name;
+}
+EXPORT_SYMBOL_GPL(bdi_dev_name);