| /* |
| * background writeback - scan btree for dirty data and write it to the backing |
| * device |
| * |
| * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com> |
| * 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) |
| { |
| if (atomic_read(&dc->disk.detaching) || |
| !dc->writeback_percent) |
| return 0; |
| |
| return next_delay(&dc->writeback_rate, sectors * 10000000ULL); |
| } |
| |
| /* 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; |
| 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); |
| |
| 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); |
| atomic_dec_bug(&dc->in_flight); |
| |
| closure_wake_up(&dc->writeback_wait); |
| |
| 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, dirty_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, dirty_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)) { |
| w->private = NULL; |
| |
| closure_delay(&dc->writeback, delay); |
| continue_at(cl, read_dirty, dirty_wq); |
| } |
| |
| 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 (bio_alloc_pages(&io->bio, GFP_KERNEL)) |
| goto err_free; |
| |
| pr_debug("%s", pkey(&w->key)); |
| |
| closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl); |
| |
| delay = writeback_delay(dc, KEY_SIZE(&w->key)); |
| |
| atomic_inc(&dc->in_flight); |
| |
| if (!closure_wait_event(&dc->writeback_wait, cl, |
| atomic_read(&dc->in_flight) < 64)) |
| continue_at(cl, read_dirty, dirty_wq); |
| } |
| |
| if (0) { |
| err_free: |
| kfree(w->private); |
| err: |
| bch_keybuf_del(&dc->writeback_keys, w); |
| } |
| |
| refill_dirty(cl); |
| } |
| |
| void bch_writeback_init_cached_dev(struct cached_dev *dc) |
| { |
| 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_singlethread_workqueue("bcache_writeback"); |
| if (!dirty_wq) |
| return -ENOMEM; |
| |
| return 0; |
| } |