| /* |
| * 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" |
| #include "writeback.h" |
| |
| #include <linux/delay.h> |
| #include <linux/kthread.h> |
| #include <trace/events/bcache.h> |
| |
| /* 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 */ |
| |
| int64_t dirty = bcache_dev_sectors_dirty(&dc->disk); |
| int64_t derivative = dirty - dc->disk.sectors_dirty_last; |
| int64_t proportional = dirty - target; |
| int64_t change; |
| |
| dc->disk.sectors_dirty_last = dirty; |
| |
| /* Scale to sectors per second */ |
| |
| proportional *= dc->writeback_rate_update_seconds; |
| proportional = div_s64(proportional, dc->writeback_rate_p_term_inverse); |
| |
| derivative = div_s64(derivative, dc->writeback_rate_update_seconds); |
| |
| derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative, |
| (dc->writeback_rate_d_term / |
| dc->writeback_rate_update_seconds) ?: 1, 0); |
| |
| derivative *= dc->writeback_rate_d_term; |
| derivative = div_s64(derivative, dc->writeback_rate_p_term_inverse); |
| |
| change = proportional + derivative; |
| |
| /* Don't increase writeback rate if the device isn't keeping up */ |
| if (change > 0 && |
| time_after64(local_clock(), |
| dc->writeback_rate.next + NSEC_PER_MSEC)) |
| change = 0; |
| |
| dc->writeback_rate.rate = |
| clamp_t(int64_t, (int64_t) dc->writeback_rate.rate + change, |
| 1, NSEC_PER_MSEC); |
| |
| dc->writeback_rate_proportional = proportional; |
| dc->writeback_rate_derivative = derivative; |
| dc->writeback_rate_change = change; |
| dc->writeback_rate_target = target; |
| } |
| |
| 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); |
| |
| schedule_delayed_work(&dc->writeback_rate_update, |
| dc->writeback_rate_update_seconds * HZ); |
| } |
| |
| static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors) |
| { |
| if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || |
| !dc->writeback_percent) |
| return 0; |
| |
| return bch_next_delay(&dc->writeback_rate, sectors); |
| } |
| |
| struct dirty_io { |
| struct closure cl; |
| struct cached_dev *dc; |
| struct bio bio; |
| }; |
| |
| static void dirty_init(struct keybuf_key *w) |
| { |
| struct dirty_io *io = w->private; |
| struct bio *bio = &io->bio; |
| |
| bio_init(bio, bio->bi_inline_vecs, |
| DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)); |
| if (!io->dc->writeback_percent) |
| bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)); |
| |
| bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9; |
| bio->bi_private = w; |
| bch_bio_map(bio, NULL); |
| } |
| |
| 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; |
| |
| bio_free_pages(&io->bio); |
| |
| /* This is kind of a dumb way of signalling errors. */ |
| if (KEY_DIRTY(&w->key)) { |
| int ret; |
| unsigned i; |
| struct keylist keys; |
| |
| bch_keylist_init(&keys); |
| |
| bkey_copy(keys.top, &w->key); |
| SET_KEY_DIRTY(keys.top, false); |
| bch_keylist_push(&keys); |
| |
| for (i = 0; i < KEY_PTRS(&w->key); i++) |
| atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin); |
| |
| ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key); |
| |
| if (ret) |
| trace_bcache_writeback_collision(&w->key); |
| |
| atomic_long_inc(ret |
| ? &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) |
| { |
| struct keybuf_key *w = bio->bi_private; |
| struct dirty_io *io = w->private; |
| |
| if (bio->bi_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); |
| bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0); |
| io->bio.bi_iter.bi_sector = KEY_START(&w->key); |
| io->bio.bi_bdev = io->dc->bdev; |
| io->bio.bi_end_io = dirty_endio; |
| |
| closure_bio_submit(&io->bio, cl); |
| |
| continue_at(cl, write_dirty_finish, system_wq); |
| } |
| |
| static void read_dirty_endio(struct bio *bio) |
| { |
| 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), |
| bio->bi_error, "reading dirty data from cache"); |
| |
| dirty_endio(bio); |
| } |
| |
| static void read_dirty_submit(struct closure *cl) |
| { |
| struct dirty_io *io = container_of(cl, struct dirty_io, cl); |
| |
| closure_bio_submit(&io->bio, cl); |
| |
| continue_at(cl, write_dirty, system_wq); |
| } |
| |
| static void read_dirty(struct cached_dev *dc) |
| { |
| unsigned delay = 0; |
| struct keybuf_key *w; |
| struct dirty_io *io; |
| struct closure cl; |
| |
| closure_init_stack(&cl); |
| |
| /* |
| * XXX: if we error, background writeback just spins. Should use some |
| * mempools. |
| */ |
| |
| while (!kthread_should_stop()) { |
| |
| w = bch_keybuf_next(&dc->writeback_keys); |
| if (!w) |
| break; |
| |
| BUG_ON(ptr_stale(dc->disk.c, &w->key, 0)); |
| |
| if (KEY_START(&w->key) != dc->last_read || |
| jiffies_to_msecs(delay) > 50) |
| while (!kthread_should_stop() && delay) |
| delay = schedule_timeout_interruptible(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); |
| bio_set_op_attrs(&io->bio, REQ_OP_READ, 0); |
| io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0); |
| io->bio.bi_bdev = PTR_CACHE(dc->disk.c, |
| &w->key, 0)->bdev; |
| io->bio.bi_end_io = read_dirty_endio; |
| |
| if (bio_alloc_pages(&io->bio, GFP_KERNEL)) |
| goto err_free; |
| |
| trace_bcache_writeback(&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 |
| */ |
| closure_sync(&cl); |
| } |
| |
| /* Scan for dirty data */ |
| |
| void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode, |
| uint64_t offset, int nr_sectors) |
| { |
| struct bcache_device *d = c->devices[inode]; |
| unsigned stripe_offset, stripe, sectors_dirty; |
| |
| if (!d) |
| return; |
| |
| stripe = offset_to_stripe(d, offset); |
| stripe_offset = offset & (d->stripe_size - 1); |
| |
| while (nr_sectors) { |
| int s = min_t(unsigned, abs(nr_sectors), |
| d->stripe_size - stripe_offset); |
| |
| if (nr_sectors < 0) |
| s = -s; |
| |
| if (stripe >= d->nr_stripes) |
| return; |
| |
| sectors_dirty = atomic_add_return(s, |
| d->stripe_sectors_dirty + stripe); |
| if (sectors_dirty == d->stripe_size) |
| set_bit(stripe, d->full_dirty_stripes); |
| else |
| clear_bit(stripe, d->full_dirty_stripes); |
| |
| nr_sectors -= s; |
| stripe_offset = 0; |
| stripe++; |
| } |
| } |
| |
| static bool dirty_pred(struct keybuf *buf, struct bkey *k) |
| { |
| struct cached_dev *dc = container_of(buf, struct cached_dev, writeback_keys); |
| |
| BUG_ON(KEY_INODE(k) != dc->disk.id); |
| |
| return KEY_DIRTY(k); |
| } |
| |
| static void refill_full_stripes(struct cached_dev *dc) |
| { |
| struct keybuf *buf = &dc->writeback_keys; |
| unsigned start_stripe, stripe, next_stripe; |
| bool wrapped = false; |
| |
| stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned)); |
| |
| if (stripe >= dc->disk.nr_stripes) |
| stripe = 0; |
| |
| start_stripe = stripe; |
| |
| while (1) { |
| stripe = find_next_bit(dc->disk.full_dirty_stripes, |
| dc->disk.nr_stripes, stripe); |
| |
| if (stripe == dc->disk.nr_stripes) |
| goto next; |
| |
| next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes, |
| dc->disk.nr_stripes, stripe); |
| |
| buf->last_scanned = KEY(dc->disk.id, |
| stripe * dc->disk.stripe_size, 0); |
| |
| bch_refill_keybuf(dc->disk.c, buf, |
| &KEY(dc->disk.id, |
| next_stripe * dc->disk.stripe_size, 0), |
| dirty_pred); |
| |
| if (array_freelist_empty(&buf->freelist)) |
| return; |
| |
| stripe = next_stripe; |
| next: |
| if (wrapped && stripe > start_stripe) |
| return; |
| |
| if (stripe == dc->disk.nr_stripes) { |
| stripe = 0; |
| wrapped = true; |
| } |
| } |
| } |
| |
| /* |
| * Returns true if we scanned the entire disk |
| */ |
| static bool refill_dirty(struct cached_dev *dc) |
| { |
| struct keybuf *buf = &dc->writeback_keys; |
| struct bkey start = KEY(dc->disk.id, 0, 0); |
| struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0); |
| struct bkey start_pos; |
| |
| /* |
| * make sure keybuf pos is inside the range for this disk - at bringup |
| * we might not be attached yet so this disk's inode nr isn't |
| * initialized then |
| */ |
| if (bkey_cmp(&buf->last_scanned, &start) < 0 || |
| bkey_cmp(&buf->last_scanned, &end) > 0) |
| buf->last_scanned = start; |
| |
| if (dc->partial_stripes_expensive) { |
| refill_full_stripes(dc); |
| if (array_freelist_empty(&buf->freelist)) |
| return false; |
| } |
| |
| start_pos = buf->last_scanned; |
| bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred); |
| |
| if (bkey_cmp(&buf->last_scanned, &end) < 0) |
| return false; |
| |
| /* |
| * If we get to the end start scanning again from the beginning, and |
| * only scan up to where we initially started scanning from: |
| */ |
| buf->last_scanned = start; |
| bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred); |
| |
| return bkey_cmp(&buf->last_scanned, &start_pos) >= 0; |
| } |
| |
| static int bch_writeback_thread(void *arg) |
| { |
| struct cached_dev *dc = arg; |
| bool searched_full_index; |
| |
| while (!kthread_should_stop()) { |
| down_write(&dc->writeback_lock); |
| if (!atomic_read(&dc->has_dirty) || |
| (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && |
| !dc->writeback_running)) { |
| up_write(&dc->writeback_lock); |
| set_current_state(TASK_INTERRUPTIBLE); |
| |
| if (kthread_should_stop()) |
| return 0; |
| |
| schedule(); |
| continue; |
| } |
| |
| searched_full_index = refill_dirty(dc); |
| |
| if (searched_full_index && |
| RB_EMPTY_ROOT(&dc->writeback_keys.keys)) { |
| atomic_set(&dc->has_dirty, 0); |
| cached_dev_put(dc); |
| SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN); |
| bch_write_bdev_super(dc, NULL); |
| } |
| |
| up_write(&dc->writeback_lock); |
| |
| bch_ratelimit_reset(&dc->writeback_rate); |
| read_dirty(dc); |
| |
| if (searched_full_index) { |
| unsigned delay = dc->writeback_delay * HZ; |
| |
| while (delay && |
| !kthread_should_stop() && |
| !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) |
| delay = schedule_timeout_interruptible(delay); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* Init */ |
| |
| struct sectors_dirty_init { |
| struct btree_op op; |
| unsigned inode; |
| }; |
| |
| static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b, |
| struct bkey *k) |
| { |
| struct sectors_dirty_init *op = container_of(_op, |
| struct sectors_dirty_init, op); |
| if (KEY_INODE(k) > op->inode) |
| return MAP_DONE; |
| |
| if (KEY_DIRTY(k)) |
| bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k), |
| KEY_START(k), KEY_SIZE(k)); |
| |
| return MAP_CONTINUE; |
| } |
| |
| void bch_sectors_dirty_init(struct cached_dev *dc) |
| { |
| struct sectors_dirty_init op; |
| |
| bch_btree_op_init(&op.op, -1); |
| op.inode = dc->disk.id; |
| |
| bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0), |
| sectors_dirty_init_fn, 0); |
| |
| dc->disk.sectors_dirty_last = bcache_dev_sectors_dirty(&dc->disk); |
| } |
| |
| void bch_cached_dev_writeback_init(struct cached_dev *dc) |
| { |
| sema_init(&dc->in_flight, 64); |
| init_rwsem(&dc->writeback_lock); |
| bch_keybuf_init(&dc->writeback_keys); |
| |
| 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 = 5; |
| dc->writeback_rate_d_term = 30; |
| dc->writeback_rate_p_term_inverse = 6000; |
| |
| INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); |
| } |
| |
| int bch_cached_dev_writeback_start(struct cached_dev *dc) |
| { |
| dc->writeback_thread = kthread_create(bch_writeback_thread, dc, |
| "bcache_writeback"); |
| if (IS_ERR(dc->writeback_thread)) |
| return PTR_ERR(dc->writeback_thread); |
| |
| schedule_delayed_work(&dc->writeback_rate_update, |
| dc->writeback_rate_update_seconds * HZ); |
| |
| bch_writeback_queue(dc); |
| |
| return 0; |
| } |