#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> void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) { } EXPORT_SYMBOL(default_unplug_io_fn); 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, .unplug_io_fn = default_unplug_io_fn, }; EXPORT_SYMBOL_GPL(default_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); static void arm_supers_timer(void); static void bdi_add_default_flusher_task(struct backing_dev_info *bdi); #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; unsigned long background_thresh; unsigned long dirty_thresh; unsigned long bdi_thresh; unsigned long nr_dirty, nr_io, nr_more_io, nr_wb; struct inode *inode; /* * inode lock is enough here, the bdi->wb_list is protected by * RCU on the reader side */ nr_wb = nr_dirty = nr_io = nr_more_io = 0; spin_lock(&inode_lock); list_for_each_entry(wb, &bdi->wb_list, list) { nr_wb++; list_for_each_entry(inode, &wb->b_dirty, i_list) nr_dirty++; list_for_each_entry(inode, &wb->b_io, i_list) nr_io++; list_for_each_entry(inode, &wb->b_more_io, i_list) nr_more_io++; } spin_unlock(&inode_lock); get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi); #define K(x) ((x) << (PAGE_SHIFT - 10)) seq_printf(m, "BdiWriteback: %8lu kB\n" "BdiReclaimable: %8lu kB\n" "BdiDirtyThresh: %8lu kB\n" "DirtyThresh: %8lu kB\n" "BackgroundThresh: %8lu kB\n" "WriteBack threads:%8lu\n" "b_dirty: %8lu\n" "b_io: %8lu\n" "b_more_io: %8lu\n" "bdi_list: %8u\n" "state: %8lx\n" "wb_mask: %8lx\n" "wb_list: %8u\n" "wb_cnt: %8u\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), nr_wb, nr_dirty, nr_io, nr_more_io, !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask, !list_empty(&bdi->wb_list), bdi->wb_cnt); #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"); bdi_class->dev_attrs = bdi_dev_attrs; bdi_debug_init(); return 0; } postcore_initcall(bdi_class_init); static int __init default_bdi_init(void) { int err; sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers"); BUG_ON(IS_ERR(sync_supers_tsk)); init_timer(&sync_supers_timer); setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0); arm_supers_timer(); err = bdi_init(&default_backing_dev_info); if (!err) bdi_register(&default_backing_dev_info, NULL, "default"); return err; } subsys_initcall(default_bdi_init); 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); } static void bdi_task_init(struct backing_dev_info *bdi, struct bdi_writeback *wb) { struct task_struct *tsk = current; spin_lock(&bdi->wb_lock); list_add_tail_rcu(&wb->list, &bdi->wb_list); spin_unlock(&bdi->wb_lock); tsk->flags |= PF_FLUSHER | PF_SWAPWRITE; set_freezable(); /* * Our parent may run at a different priority, just set us to normal */ set_user_nice(tsk, 0); } static int bdi_start_fn(void *ptr) { struct bdi_writeback *wb = ptr; struct backing_dev_info *bdi = wb->bdi; int ret; /* * Add us to the active bdi_list */ spin_lock_bh(&bdi_lock); list_add_rcu(&bdi->bdi_list, &bdi_list); spin_unlock_bh(&bdi_lock); bdi_task_init(bdi, wb); /* * 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); ret = bdi_writeback_task(wb); /* * Remove us from the list */ spin_lock(&bdi->wb_lock); list_del_rcu(&wb->list); spin_unlock(&bdi->wb_lock); /* * Flush any work that raced with us exiting. No new work * will be added, since this bdi isn't discoverable anymore. */ if (!list_empty(&bdi->work_list)) wb_do_writeback(wb, 1); wb->task = NULL; return ret; } int bdi_has_dirty_io(struct backing_dev_info *bdi) { return wb_has_dirty_io(&bdi->wb); } static void bdi_flush_io(struct backing_dev_info *bdi) { struct writeback_control wbc = { .bdi = bdi, .sync_mode = WB_SYNC_NONE, .older_than_this = NULL, .range_cyclic = 1, .nr_to_write = 1024, }; writeback_inodes_wbc(&wbc); } /* * kupdated() used to do this. We cannot do it from the bdi_forker_task() * 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 tasks 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; } static void arm_supers_timer(void) { unsigned long next; 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); arm_supers_timer(); } static int bdi_forker_task(void *ptr) { struct bdi_writeback *me = ptr; bdi_task_init(me->bdi, me); for (;;) { struct backing_dev_info *bdi, *tmp; struct bdi_writeback *wb; /* * 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)) wb_do_writeback(me, 0); spin_lock_bh(&bdi_lock); /* * Check if any existing bdi's have dirty data without * a thread registered. If so, set that up. */ list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) { if (bdi->wb.task) continue; if (list_empty(&bdi->work_list) && !bdi_has_dirty_io(bdi)) continue; bdi_add_default_flusher_task(bdi); } set_current_state(TASK_INTERRUPTIBLE); if (list_empty(&bdi_pending_list)) { unsigned long wait; spin_unlock_bh(&bdi_lock); wait = msecs_to_jiffies(dirty_writeback_interval * 10); schedule_timeout(wait); try_to_freeze(); continue; } __set_current_state(TASK_RUNNING); /* * This is our real job - check for pending entries in * bdi_pending_list, and create the tasks that got added */ bdi = list_entry(bdi_pending_list.next, struct backing_dev_info, bdi_list); list_del_init(&bdi->bdi_list); spin_unlock_bh(&bdi_lock); wb = &bdi->wb; wb->task = kthread_run(bdi_start_fn, wb, "flush-%s", dev_name(bdi->dev)); /* * If task creation fails, then readd the bdi to * the pending list and force writeout of the bdi * from this forker thread. That will free some memory * and we can try again. */ if (IS_ERR(wb->task)) { wb->task = NULL; /* * Add this 'bdi' to the back, so we get * a chance to flush other bdi's to free * memory. */ spin_lock_bh(&bdi_lock); list_add_tail(&bdi->bdi_list, &bdi_pending_list); spin_unlock_bh(&bdi_lock); bdi_flush_io(bdi); } } return 0; } static void bdi_add_to_pending(struct rcu_head *head) { struct backing_dev_info *bdi; bdi = container_of(head, struct backing_dev_info, rcu_head); INIT_LIST_HEAD(&bdi->bdi_list); spin_lock(&bdi_lock); list_add_tail(&bdi->bdi_list, &bdi_pending_list); spin_unlock(&bdi_lock); /* * We are now on the pending list, wake up bdi_forker_task() * to finish the job and add us back to the active bdi_list */ wake_up_process(default_backing_dev_info.wb.task); } /* * Add the default flusher task that gets created for any bdi * that has dirty data pending writeout */ void static bdi_add_default_flusher_task(struct backing_dev_info *bdi) { if (!bdi_cap_writeback_dirty(bdi)) return; if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) { printk(KERN_ERR "bdi %p/%s is not registered!\n", bdi, bdi->name); return; } /* * Check with the helper whether to proceed adding a task. Will only * abort if we two or more simultanous calls to * bdi_add_default_flusher_task() occured, further additions will block * waiting for previous additions to finish. */ if (!test_and_set_bit(BDI_pending, &bdi->state)) { list_del_rcu(&bdi->bdi_list); /* * We must wait for the current RCU period to end before * moving to the pending list. So schedule that operation * from an RCU callback. */ call_rcu(&bdi->rcu_head, bdi_add_to_pending); } } /* * 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(); } int bdi_register(struct backing_dev_info *bdi, struct device *parent, const char *fmt, ...) { va_list args; int ret = 0; struct device *dev; if (bdi->dev) /* The driver needs to use separate queues per device */ goto exit; va_start(args, fmt); dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args); va_end(args); if (IS_ERR(dev)) { ret = PTR_ERR(dev); goto exit; } spin_lock_bh(&bdi_lock); list_add_tail_rcu(&bdi->bdi_list, &bdi_list); spin_unlock_bh(&bdi_lock); 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_task, wb, "bdi-%s", dev_name(dev)); if (IS_ERR(wb->task)) { wb->task = NULL; ret = -ENOMEM; bdi_remove_from_list(bdi); goto exit; } } bdi_debug_register(bdi, dev_name(dev)); set_bit(BDI_registered, &bdi->state); exit: return ret; } EXPORT_SYMBOL(bdi_register); int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev) { return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev)); } EXPORT_SYMBOL(bdi_register_dev); /* * Remove bdi from the global list and shutdown any threads we have running */ static void bdi_wb_shutdown(struct backing_dev_info *bdi) { struct bdi_writeback *wb; if (!bdi_cap_writeback_dirty(bdi)) return; /* * If setup is pending, wait for that to complete first */ wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait, TASK_UNINTERRUPTIBLE); /* * Make sure nobody finds us on the bdi_list anymore */ bdi_remove_from_list(bdi); /* * Finally, kill the kernel threads. We don't need to be RCU * safe anymore, since the bdi is gone from visibility. */ list_for_each_entry(wb, &bdi->wb_list, list) kthread_stop(wb->task); } void bdi_unregister(struct backing_dev_info *bdi) { if (bdi->dev) { 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); 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_RCU_HEAD(&bdi->rcu_head); INIT_LIST_HEAD(&bdi->bdi_list); INIT_LIST_HEAD(&bdi->wb_list); INIT_LIST_HEAD(&bdi->work_list); bdi_wb_init(&bdi->wb, bdi); /* * Just one thread support for now, hard code mask and count */ bdi->wb_mask = 1; bdi->wb_cnt = 1; 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; err = prop_local_init_percpu(&bdi->completions); if (err) { err: while (i--) percpu_counter_destroy(&bdi->bdi_stat[i]); } return err; } EXPORT_SYMBOL(bdi_init); void bdi_destroy(struct backing_dev_info *bdi) { int i; /* * Splice our entries to the default_backing_dev_info, if this * bdi disappears */ if (bdi_has_dirty_io(bdi)) { struct bdi_writeback *dst = &default_backing_dev_info.wb; spin_lock(&inode_lock); 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(&inode_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); static wait_queue_head_t congestion_wqh[2] = { __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]), __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1]) }; 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; clear_bit(bit, &bdi->state); smp_mb__after_clear_bit(); if (waitqueue_active(wqh)) wake_up(wqh); } EXPORT_SYMBOL(clear_bdi_congested); void set_bdi_congested(struct backing_dev_info *bdi, int sync) { enum bdi_state bit; bit = sync ? BDI_sync_congested : BDI_async_congested; set_bit(bit, &bdi->state); } 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; 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); return ret; } EXPORT_SYMBOL(congestion_wait);