diff options
Diffstat (limited to 'mm/backing-dev.c')
| -rw-r--r-- | mm/backing-dev.c | 1098 |
1 files changed, 1098 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c new file mode 100644 index 000000000..67431d02a --- /dev/null +++ b/mm/backing-dev.c @@ -0,0 +1,1098 @@ + +#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> + +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; +static const char *bdi_unknown_name = "(unknown)"; + +/* + * 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 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); + +#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(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); +#undef K + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats); + +static int bdi_debug_register(struct backing_dev_info *bdi, const char *name) +{ + if (!bdi_debug_root) + return -ENOMEM; + + bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); + if (!bdi->debug_dir) + return -ENOMEM; + + bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir, + bdi, &bdi_debug_stats_fops); + if (!bdi->debug_stats) { + debugfs_remove(bdi->debug_dir); + bdi->debug_dir = NULL; + return -ENOMEM; + } + + return 0; +} + +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 int bdi_debug_register(struct backing_dev_info *bdi, + const char *name) +{ + return 0; +} +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 bdi_init(struct backing_dev_info *bdi); + +static int __init default_bdi_init(void) +{ + int err; + + bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND | + WQ_SYSFS, 0); + if (!bdi_wq) + return -ENOMEM; + + err = bdi_init(&noop_backing_dev_info); + + return err; +} +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_bh(&wb->work_lock); + if (test_bit(WB_registered, &wb->state)) + queue_delayed_work(bdi_wq, &wb->dwork, timeout); + spin_unlock_bh(&wb->work_lock); +} + +/* + * 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, + int blkcg_id, gfp_t gfp) +{ + int i, err; + + memset(wb, 0, sizeof(*wb)); + + if (wb != &bdi->wb) + bdi_get(bdi); + 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); + + 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); + wb->dirty_sleep = jiffies; + + wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp); + if (!wb->congested) { + err = -ENOMEM; + goto out_put_bdi; + } + + err = fprop_local_init_percpu(&wb->completions, gfp); + if (err) + goto out_put_cong; + + 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); +out_put_cong: + wb_congested_put(wb->congested); +out_put_bdi: + if (wb != &bdi->wb) + bdi_put(bdi); + 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_bh(&wb->work_lock); + if (!test_and_clear_bit(WB_registered, &wb->state)) { + spin_unlock_bh(&wb->work_lock); + return; + } + spin_unlock_bh(&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)); +} + +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); + wb_congested_put(wb->congested); + if (wb != &wb->bdi->wb) + bdi_put(wb->bdi); +} + +#ifdef CONFIG_CGROUP_WRITEBACK + +#include <linux/memcontrol.h> + +/* + * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree, + * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU + * protected. + */ +static DEFINE_SPINLOCK(cgwb_lock); +static struct workqueue_struct *cgwb_release_wq; + +/** + * wb_congested_get_create - get or create a wb_congested + * @bdi: associated bdi + * @blkcg_id: ID of the associated blkcg + * @gfp: allocation mask + * + * Look up the wb_congested for @blkcg_id on @bdi. If missing, create one. + * The returned wb_congested has its reference count incremented. Returns + * NULL on failure. + */ +struct bdi_writeback_congested * +wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp) +{ + struct bdi_writeback_congested *new_congested = NULL, *congested; + struct rb_node **node, *parent; + unsigned long flags; +retry: + spin_lock_irqsave(&cgwb_lock, flags); + + node = &bdi->cgwb_congested_tree.rb_node; + parent = NULL; + + while (*node != NULL) { + parent = *node; + congested = rb_entry(parent, struct bdi_writeback_congested, + rb_node); + if (congested->blkcg_id < blkcg_id) + node = &parent->rb_left; + else if (congested->blkcg_id > blkcg_id) + node = &parent->rb_right; + else + goto found; + } + + if (new_congested) { + /* !found and storage for new one already allocated, insert */ + congested = new_congested; + rb_link_node(&congested->rb_node, parent, node); + rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree); + spin_unlock_irqrestore(&cgwb_lock, flags); + return congested; + } + + spin_unlock_irqrestore(&cgwb_lock, flags); + + /* allocate storage for new one and retry */ + new_congested = kzalloc(sizeof(*new_congested), gfp); + if (!new_congested) + return NULL; + + refcount_set(&new_congested->refcnt, 1); + new_congested->__bdi = bdi; + new_congested->blkcg_id = blkcg_id; + goto retry; + +found: + refcount_inc(&congested->refcnt); + spin_unlock_irqrestore(&cgwb_lock, flags); + kfree(new_congested); + return congested; +} + +/** + * wb_congested_put - put a wb_congested + * @congested: wb_congested to put + * + * Put @congested and destroy it if the refcnt reaches zero. + */ +void wb_congested_put(struct bdi_writeback_congested *congested) +{ + unsigned long flags; + + if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags)) + return; + + /* bdi might already have been destroyed leaving @congested unlinked */ + if (congested->__bdi) { + rb_erase(&congested->rb_node, + &congested->__bdi->cgwb_congested_tree); + congested->__bdi = NULL; + } + + spin_unlock_irqrestore(&cgwb_lock, flags); + kfree(congested); +} + +static void cgwb_release_workfn(struct work_struct *work) +{ + struct bdi_writeback *wb = container_of(work, struct bdi_writeback, + release_work); + struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css); + + 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 cgwb_refcnt becomes zero */ + blkcg_cgwb_put(blkcg); + + fprop_local_destroy_percpu(&wb->memcg_completions); + percpu_ref_exit(&wb->refcnt); + wb_exit(wb); + kfree_rcu(wb, 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); + 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 blkcg *blkcg; + 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); + blkcg = css_to_blkcg(blkcg_css); + memcg_cgwb_list = &memcg->cgwb_list; + blkcg_cgwb_list = &blkcg->cgwb_list; + + /* 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, blkcg_css->id, 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_WORK(&wb->release_work, cgwb_release_workfn); + set_bit(WB_registered, &wb->state); + + /* + * 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_cgwb_get(blkcg); + 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: + 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_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. 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_create(struct backing_dev_info *bdi, + struct cgroup_subsys_state *memcg_css, + gfp_t gfp) +{ + struct bdi_writeback *wb; + + might_sleep_if(gfpflags_allow_blocking(gfp)); + + if (!memcg_css->parent) + return &bdi->wb; + + do { + 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(); + } 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); + bdi->cgwb_congested_tree = RB_ROOT; + mutex_init(&bdi->cgwb_release_mutex); + init_rwsem(&bdi->wb_switch_rwsem); + + ret = wb_init(&bdi->wb, bdi, 1, 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); +} + +/** + * 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); +} + +/** + * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined + * @blkcg: blkcg being offlined + * + * Also prevents creation of any new wb's associated with @blkcg. + */ +void wb_blkcg_offline(struct blkcg *blkcg) +{ + struct bdi_writeback *wb, *next; + + spin_lock_irq(&cgwb_lock); + list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node) + cgwb_kill(wb); + blkcg->cgwb_list.next = NULL; /* prevent new wb's */ + spin_unlock_irq(&cgwb_lock); +} + +static void cgwb_bdi_exit(struct backing_dev_info *bdi) +{ + struct rb_node *rbn; + + spin_lock_irq(&cgwb_lock); + while ((rbn = rb_first(&bdi->cgwb_congested_tree))) { + struct bdi_writeback_congested *congested = + rb_entry(rbn, struct bdi_writeback_congested, rb_node); + + rb_erase(rbn, &bdi->cgwb_congested_tree); + congested->__bdi = NULL; /* mark @congested unlinked */ + } + 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) +{ + int err; + + bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL); + if (!bdi->wb_congested) + return -ENOMEM; + + refcount_set(&bdi->wb_congested->refcnt, 1); + + err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); + if (err) { + wb_congested_put(bdi->wb_congested); + return err; + } + return 0; +} + +static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { } + +static void cgwb_bdi_exit(struct backing_dev_info *bdi) +{ + wb_congested_put(bdi->wb_congested); +} + +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 */ + +static int bdi_init(struct backing_dev_info *bdi) +{ + int ret; + + 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); + + ret = cgwb_bdi_init(bdi); + + return ret; +} + +struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id) +{ + struct backing_dev_info *bdi; + + bdi = kmalloc_node(sizeof(struct backing_dev_info), + gfp_mask | __GFP_ZERO, node_id); + if (!bdi) + return NULL; + + if (bdi_init(bdi)) { + kfree(bdi); + return NULL; + } + return bdi; +} +EXPORT_SYMBOL(bdi_alloc_node); + +int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) +{ + struct device *dev; + + 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); + 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_va); + +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); + +int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner) +{ + int rc; + + rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt)); + if (rc) + return rc; + /* Leaking owner reference... */ + WARN_ON(bdi->owner); + bdi->owner = owner; + get_device(owner); + return 0; +} +EXPORT_SYMBOL(bdi_register_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); + list_del_rcu(&bdi->bdi_list); + spin_unlock_bh(&bdi_lock); + + synchronize_rcu_expedited(); +} + +void bdi_unregister(struct backing_dev_info *bdi) +{ + /* 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; + } +} + +static void release_bdi(struct kref *ref) +{ + struct backing_dev_info *bdi = + container_of(ref, struct backing_dev_info, refcnt); + + if (test_bit(WB_registered, &bdi->wb.state)) + bdi_unregister(bdi); + WARN_ON_ONCE(bdi->dev); + wb_exit(&bdi->wb); + cgwb_bdi_exit(bdi); + kfree(bdi); +} + +void bdi_put(struct backing_dev_info *bdi) +{ + kref_put(&bdi->refcnt, release_bdi); +} +EXPORT_SYMBOL(bdi_put); + +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); + +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_wb_congested[2]; + +void clear_wb_congested(struct bdi_writeback_congested *congested, int sync) +{ + wait_queue_head_t *wqh = &congestion_wqh[sync]; + enum wb_congested_state bit; + + bit = sync ? WB_sync_congested : WB_async_congested; + if (test_and_clear_bit(bit, &congested->state)) + atomic_dec(&nr_wb_congested[sync]); + smp_mb__after_atomic(); + if (waitqueue_active(wqh)) + wake_up(wqh); +} +EXPORT_SYMBOL(clear_wb_congested); + +void set_wb_congested(struct bdi_writeback_congested *congested, int sync) +{ + enum wb_congested_state bit; + + bit = sync ? WB_sync_congested : WB_async_congested; + if (!test_and_set_bit(bit, &congested->state)) + atomic_inc(&nr_wb_congested[sync]); +} +EXPORT_SYMBOL(set_wb_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 pgdat to complete writes + * @sync: SYNC or ASYNC IO + * @timeout: timeout in jiffies + * + * In the event of a congested backing_dev (any backing_dev) this waits + * for up to @timeout jiffies for either a BDI to exit congestion of the + * given @sync queue or a write to complete. + * + * 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(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, yield if necessary instead + * of sleeping on the congestion queue + */ + if (atomic_read(&nr_wb_congested[sync]) == 0) { + 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); |