/* * background writeback - scan btree for dirty data and write it to the backing * device * * Copyright 2010, 2011 Kent Overstreet * Copyright 2012 Google, Inc. */ #include "bcache.h" #include "btree.h" #include "debug.h" static struct workqueue_struct *dirty_wq; static void read_dirty(struct closure *); struct dirty_io { struct closure cl; struct cached_dev *dc; struct bio bio; }; /* Rate limiting */ static void __update_writeback_rate(struct cached_dev *dc) { struct cache_set *c = dc->disk.c; uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size; uint64_t cache_dirty_target = div_u64(cache_sectors * dc->writeback_percent, 100); int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev), c->cached_dev_sectors); /* PD controller */ int change = 0; int64_t error; int64_t dirty = atomic_long_read(&dc->disk.sectors_dirty); int64_t derivative = dirty - dc->disk.sectors_dirty_last; dc->disk.sectors_dirty_last = dirty; derivative *= dc->writeback_rate_d_term; derivative = clamp(derivative, -dirty, dirty); derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative, dc->writeback_rate_d_smooth, 0); /* Avoid divide by zero */ if (!target) goto out; error = div64_s64((dirty + derivative - target) << 8, target); change = div_s64((dc->writeback_rate.rate * error) >> 8, dc->writeback_rate_p_term_inverse); /* Don't increase writeback rate if the device isn't keeping up */ if (change > 0 && time_after64(local_clock(), dc->writeback_rate.next + 10 * NSEC_PER_MSEC)) change = 0; dc->writeback_rate.rate = clamp_t(int64_t, dc->writeback_rate.rate + change, 1, NSEC_PER_MSEC); out: dc->writeback_rate_derivative = derivative; dc->writeback_rate_change = change; dc->writeback_rate_target = target; schedule_delayed_work(&dc->writeback_rate_update, dc->writeback_rate_update_seconds * HZ); } static void update_writeback_rate(struct work_struct *work) { struct cached_dev *dc = container_of(to_delayed_work(work), struct cached_dev, writeback_rate_update); down_read(&dc->writeback_lock); if (atomic_read(&dc->has_dirty) && dc->writeback_percent) __update_writeback_rate(dc); up_read(&dc->writeback_lock); } static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors) { uint64_t ret; if (atomic_read(&dc->disk.detaching) || !dc->writeback_percent) return 0; ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL); return min_t(uint64_t, ret, HZ); } /* Background writeback */ static bool dirty_pred(struct keybuf *buf, struct bkey *k) { return KEY_DIRTY(k); } static void dirty_init(struct keybuf_key *w) { struct dirty_io *io = w->private; struct bio *bio = &io->bio; bio_init(bio); if (!io->dc->writeback_percent) bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)); bio->bi_size = KEY_SIZE(&w->key) << 9; bio->bi_max_vecs = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS); bio->bi_private = w; bio->bi_io_vec = bio->bi_inline_vecs; bch_bio_map(bio, NULL); } static void refill_dirty(struct closure *cl) { struct cached_dev *dc = container_of(cl, struct cached_dev, writeback.cl); struct keybuf *buf = &dc->writeback_keys; bool searched_from_start = false; struct bkey end = MAX_KEY; SET_KEY_INODE(&end, dc->disk.id); if (!atomic_read(&dc->disk.detaching) && !dc->writeback_running) closure_return(cl); down_write(&dc->writeback_lock); if (!atomic_read(&dc->has_dirty)) { SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN); bch_write_bdev_super(dc, NULL); up_write(&dc->writeback_lock); closure_return(cl); } if (bkey_cmp(&buf->last_scanned, &end) >= 0) { buf->last_scanned = KEY(dc->disk.id, 0, 0); searched_from_start = true; } bch_refill_keybuf(dc->disk.c, buf, &end); if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) { /* Searched the entire btree - delay awhile */ if (RB_EMPTY_ROOT(&buf->keys)) { atomic_set(&dc->has_dirty, 0); cached_dev_put(dc); } if (!atomic_read(&dc->disk.detaching)) closure_delay(&dc->writeback, dc->writeback_delay * HZ); } up_write(&dc->writeback_lock); bch_ratelimit_reset(&dc->writeback_rate); /* Punt to workqueue only so we don't recurse and blow the stack */ continue_at(cl, read_dirty, dirty_wq); } void bch_writeback_queue(struct cached_dev *dc) { if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) { if (!atomic_read(&dc->disk.detaching)) closure_delay(&dc->writeback, dc->writeback_delay * HZ); continue_at(&dc->writeback.cl, refill_dirty, dirty_wq); } } void bch_writeback_add(struct cached_dev *dc, unsigned sectors) { atomic_long_add(sectors, &dc->disk.sectors_dirty); if (!atomic_read(&dc->has_dirty) && !atomic_xchg(&dc->has_dirty, 1)) { atomic_inc(&dc->count); if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) { SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY); /* XXX: should do this synchronously */ bch_write_bdev_super(dc, NULL); } bch_writeback_queue(dc); if (dc->writeback_percent) schedule_delayed_work(&dc->writeback_rate_update, dc->writeback_rate_update_seconds * HZ); } } /* Background writeback - IO loop */ static void dirty_io_destructor(struct closure *cl) { struct dirty_io *io = container_of(cl, struct dirty_io, cl); kfree(io); } static void write_dirty_finish(struct closure *cl) { struct dirty_io *io = container_of(cl, struct dirty_io, cl); struct keybuf_key *w = io->bio.bi_private; struct cached_dev *dc = io->dc; struct bio_vec *bv = bio_iovec_idx(&io->bio, io->bio.bi_vcnt); while (bv-- != io->bio.bi_io_vec) __free_page(bv->bv_page); /* This is kind of a dumb way of signalling errors. */ if (KEY_DIRTY(&w->key)) { unsigned i; struct btree_op op; bch_btree_op_init_stack(&op); op.type = BTREE_REPLACE; bkey_copy(&op.replace, &w->key); SET_KEY_DIRTY(&w->key, false); bch_keylist_add(&op.keys, &w->key); for (i = 0; i < KEY_PTRS(&w->key); i++) atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin); pr_debug("clearing %s", pkey(&w->key)); bch_btree_insert(&op, dc->disk.c); closure_sync(&op.cl); atomic_long_inc(op.insert_collision ? &dc->disk.c->writeback_keys_failed : &dc->disk.c->writeback_keys_done); } bch_keybuf_del(&dc->writeback_keys, w); up(&dc->in_flight); closure_return_with_destructor(cl, dirty_io_destructor); } static void dirty_endio(struct bio *bio, int error) { struct keybuf_key *w = bio->bi_private; struct dirty_io *io = w->private; if (error) SET_KEY_DIRTY(&w->key, false); closure_put(&io->cl); } static void write_dirty(struct closure *cl) { struct dirty_io *io = container_of(cl, struct dirty_io, cl); struct keybuf_key *w = io->bio.bi_private; dirty_init(w); io->bio.bi_rw = WRITE; io->bio.bi_sector = KEY_START(&w->key); io->bio.bi_bdev = io->dc->bdev; io->bio.bi_end_io = dirty_endio; trace_bcache_write_dirty(&io->bio); closure_bio_submit(&io->bio, cl, &io->dc->disk); continue_at(cl, write_dirty_finish, system_wq); } static void read_dirty_endio(struct bio *bio, int error) { struct keybuf_key *w = bio->bi_private; struct dirty_io *io = w->private; bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0), error, "reading dirty data from cache"); dirty_endio(bio, error); } static void read_dirty_submit(struct closure *cl) { struct dirty_io *io = container_of(cl, struct dirty_io, cl); trace_bcache_read_dirty(&io->bio); closure_bio_submit(&io->bio, cl, &io->dc->disk); continue_at(cl, write_dirty, system_wq); } static void read_dirty(struct closure *cl) { struct cached_dev *dc = container_of(cl, struct cached_dev, writeback.cl); unsigned delay = writeback_delay(dc, 0); struct keybuf_key *w; struct dirty_io *io; /* * XXX: if we error, background writeback just spins. Should use some * mempools. */ while (1) { w = bch_keybuf_next(&dc->writeback_keys); if (!w) break; BUG_ON(ptr_stale(dc->disk.c, &w->key, 0)); if (delay > 0 && (KEY_START(&w->key) != dc->last_read || jiffies_to_msecs(delay) > 50)) delay = schedule_timeout_uninterruptible(delay); dc->last_read = KEY_OFFSET(&w->key); io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec) * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), GFP_KERNEL); if (!io) goto err; w->private = io; io->dc = dc; dirty_init(w); io->bio.bi_sector = PTR_OFFSET(&w->key, 0); io->bio.bi_bdev = PTR_CACHE(dc->disk.c, &w->key, 0)->bdev; io->bio.bi_rw = READ; io->bio.bi_end_io = read_dirty_endio; if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL)) goto err_free; pr_debug("%s", pkey(&w->key)); down(&dc->in_flight); closure_call(&io->cl, read_dirty_submit, NULL, cl); delay = writeback_delay(dc, KEY_SIZE(&w->key)); } if (0) { err_free: kfree(w->private); err: bch_keybuf_del(&dc->writeback_keys, w); } /* * Wait for outstanding writeback IOs to finish (and keybuf slots to be * freed) before refilling again */ continue_at(cl, refill_dirty, dirty_wq); } void bch_cached_dev_writeback_init(struct cached_dev *dc) { sema_init(&dc->in_flight, 64); closure_init_unlocked(&dc->writeback); init_rwsem(&dc->writeback_lock); bch_keybuf_init(&dc->writeback_keys, dirty_pred); dc->writeback_metadata = true; dc->writeback_running = true; dc->writeback_percent = 10; dc->writeback_delay = 30; dc->writeback_rate.rate = 1024; dc->writeback_rate_update_seconds = 30; dc->writeback_rate_d_term = 16; dc->writeback_rate_p_term_inverse = 64; dc->writeback_rate_d_smooth = 8; INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); schedule_delayed_work(&dc->writeback_rate_update, dc->writeback_rate_update_seconds * HZ); } void bch_writeback_exit(void) { if (dirty_wq) destroy_workqueue(dirty_wq); } int __init bch_writeback_init(void) { dirty_wq = create_workqueue("bcache_writeback"); if (!dirty_wq) return -ENOMEM; return 0; }