bcache: A block layer cache

Does writethrough and writeback caching, handles unclean shutdown, and
has a bunch of other nifty features motivated by real world usage.

See the wiki at http://bcache.evilpiepirate.org for more.

Signed-off-by: Kent Overstreet <koverstreet@google.com>

1 files changed, 785 insertions, 0 deletions

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
new file mode 100644
index 000000000000..c871ffaabbb0
--- /dev/null
+++ b/drivers/md/bcache/journal.c
@@ -0,0 +1,785 @@
+/*
+ * bcache journalling code, for btree insertions
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+/*
+ * Journal replay/recovery:
+ *
+ * This code is all driven from run_cache_set(); we first read the journal
+ * entries, do some other stuff, then we mark all the keys in the journal
+ * entries (same as garbage collection would), then we replay them - reinserting
+ * them into the cache in precisely the same order as they appear in the
+ * journal.
+ *
+ * We only journal keys that go in leaf nodes, which simplifies things quite a
+ * bit.
+ */
+
+static void journal_read_endio(struct bio *bio, int error)
+{
+	struct closure *cl = bio->bi_private;
+	closure_put(cl);
+}
+
+static int journal_read_bucket(struct cache *ca, struct list_head *list,
+			       struct btree_op *op, unsigned bucket_index)
+{
+	struct journal_device *ja = &ca->journal;
+	struct bio *bio = &ja->bio;
+
+	struct journal_replay *i;
+	struct jset *j, *data = ca->set->journal.w[0].data;
+	unsigned len, left, offset = 0;
+	int ret = 0;
+	sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
+
+	pr_debug("reading %llu", (uint64_t) bucket);
+
+	while (offset < ca->sb.bucket_size) {
+reread:		left = ca->sb.bucket_size - offset;
+		len = min_t(unsigned, left, PAGE_SECTORS * 8);
+
+		bio_reset(bio);
+		bio->bi_sector	= bucket + offset;
+		bio->bi_bdev	= ca->bdev;
+		bio->bi_rw	= READ;
+		bio->bi_size	= len << 9;
+
+		bio->bi_end_io	= journal_read_endio;
+		bio->bi_private = &op->cl;
+		bio_map(bio, data);
+
+		closure_bio_submit(bio, &op->cl, ca);
+		closure_sync(&op->cl);
+
+		/* This function could be simpler now since we no longer write
+		 * journal entries that overlap bucket boundaries; this means
+		 * the start of a bucket will always have a valid journal entry
+		 * if it has any journal entries at all.
+		 */
+
+		j = data;
+		while (len) {
+			struct list_head *where;
+			size_t blocks, bytes = set_bytes(j);
+
+			if (j->magic != jset_magic(ca->set))
+				return ret;
+
+			if (bytes > left << 9)
+				return ret;
+
+			if (bytes > len << 9)
+				goto reread;
+
+			if (j->csum != csum_set(j))
+				return ret;
+
+			blocks = set_blocks(j, ca->set);
+
+			while (!list_empty(list)) {
+				i = list_first_entry(list,
+					struct journal_replay, list);
+				if (i->j.seq >= j->last_seq)
+					break;
+				list_del(&i->list);
+				kfree(i);
+			}
+
+			list_for_each_entry_reverse(i, list, list) {
+				if (j->seq == i->j.seq)
+					goto next_set;
+
+				if (j->seq < i->j.last_seq)
+					goto next_set;
+
+				if (j->seq > i->j.seq) {
+					where = &i->list;
+					goto add;
+				}
+			}
+
+			where = list;
+add:
+			i = kmalloc(offsetof(struct journal_replay, j) +
+				    bytes, GFP_KERNEL);
+			if (!i)
+				return -ENOMEM;
+			memcpy(&i->j, j, bytes);
+			list_add(&i->list, where);
+			ret = 1;
+
+			ja->seq[bucket_index] = j->seq;
+next_set:
+			offset	+= blocks * ca->sb.block_size;
+			len	-= blocks * ca->sb.block_size;
+			j = ((void *) j) + blocks * block_bytes(ca);
+		}
+	}
+
+	return ret;
+}
+
+int bch_journal_read(struct cache_set *c, struct list_head *list,
+			struct btree_op *op)
+{
+#define read_bucket(b)							\
+	({								\
+		int ret = journal_read_bucket(ca, list, op, b);		\
+		__set_bit(b, bitmap);					\
+		if (ret < 0)						\
+			return ret;					\
+		ret;							\
+	})
+
+	struct cache *ca;
+	unsigned iter;
+
+	for_each_cache(ca, c, iter) {
+		struct journal_device *ja = &ca->journal;
+		unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
+		unsigned i, l, r, m;
+		uint64_t seq;
+
+		bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
+		pr_debug("%u journal buckets", ca->sb.njournal_buckets);
+
+		/* Read journal buckets ordered by golden ratio hash to quickly
+		 * find a sequence of buckets with valid journal entries
+		 */
+		for (i = 0; i < ca->sb.njournal_buckets; i++) {
+			l = (i * 2654435769U) % ca->sb.njournal_buckets;
+
+			if (test_bit(l, bitmap))
+				break;
+
+			if (read_bucket(l))
+				goto bsearch;
+		}
+
+		/* If that fails, check all the buckets we haven't checked
+		 * already
+		 */
+		pr_debug("falling back to linear search");
+
+		for (l = 0; l < ca->sb.njournal_buckets; l++) {
+			if (test_bit(l, bitmap))
+				continue;
+
+			if (read_bucket(l))
+				goto bsearch;
+		}
+bsearch:
+		/* Binary search */
+		m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
+		pr_debug("starting binary search, l %u r %u", l, r);
+
+		while (l + 1 < r) {
+			m = (l + r) >> 1;
+
+			if (read_bucket(m))
+				l = m;
+			else
+				r = m;
+		}
+
+		/* Read buckets in reverse order until we stop finding more
+		 * journal entries
+		 */
+		pr_debug("finishing up");
+		l = m;
+
+		while (1) {
+			if (!l--)
+				l = ca->sb.njournal_buckets - 1;
+
+			if (l == m)
+				break;
+
+			if (test_bit(l, bitmap))
+				continue;
+
+			if (!read_bucket(l))
+				break;
+		}
+
+		seq = 0;
+
+		for (i = 0; i < ca->sb.njournal_buckets; i++)
+			if (ja->seq[i] > seq) {
+				seq = ja->seq[i];
+				ja->cur_idx = ja->discard_idx =
+					ja->last_idx = i;
+
+			}
+	}
+
+	c->journal.seq = list_entry(list->prev,
+				    struct journal_replay,
+				    list)->j.seq;
+
+	return 0;
+#undef read_bucket
+}
+
+void bch_journal_mark(struct cache_set *c, struct list_head *list)
+{
+	atomic_t p = { 0 };
+	struct bkey *k;
+	struct journal_replay *i;
+	struct journal *j = &c->journal;
+	uint64_t last = j->seq;
+
+	/*
+	 * journal.pin should never fill up - we never write a journal
+	 * entry when it would fill up. But if for some reason it does, we
+	 * iterate over the list in reverse order so that we can just skip that
+	 * refcount instead of bugging.
+	 */
+
+	list_for_each_entry_reverse(i, list, list) {
+		BUG_ON(last < i->j.seq);
+		i->pin = NULL;
+
+		while (last-- != i->j.seq)
+			if (fifo_free(&j->pin) > 1) {
+				fifo_push_front(&j->pin, p);
+				atomic_set(&fifo_front(&j->pin), 0);
+			}
+
+		if (fifo_free(&j->pin) > 1) {
+			fifo_push_front(&j->pin, p);
+			i->pin = &fifo_front(&j->pin);
+			atomic_set(i->pin, 1);
+		}
+
+		for (k = i->j.start;
+		     k < end(&i->j);
+		     k = bkey_next(k)) {
+			unsigned j;
+
+			for (j = 0; j < KEY_PTRS(k); j++) {
+				struct bucket *g = PTR_BUCKET(c, k, j);
+				atomic_inc(&g->pin);
+
+				if (g->prio == BTREE_PRIO &&
+				    !ptr_stale(c, k, j))
+					g->prio = INITIAL_PRIO;
+			}
+
+			__bch_btree_mark_key(c, 0, k);
+		}
+	}
+}
+
+int bch_journal_replay(struct cache_set *s, struct list_head *list,
+			  struct btree_op *op)
+{
+	int ret = 0, keys = 0, entries = 0;
+	struct bkey *k;
+	struct journal_replay *i =
+		list_entry(list->prev, struct journal_replay, list);
+
+	uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
+
+	list_for_each_entry(i, list, list) {
+		BUG_ON(i->pin && atomic_read(i->pin) != 1);
+
+		if (n != i->j.seq)
+			pr_err("journal entries %llu-%llu "
+			       "missing! (replaying %llu-%llu)\n",
+			       n, i->j.seq - 1, start, end);
+
+		for (k = i->j.start;
+		     k < end(&i->j);
+		     k = bkey_next(k)) {
+			pr_debug("%s", pkey(k));
+			bkey_copy(op->keys.top, k);
+			bch_keylist_push(&op->keys);
+
+			op->journal = i->pin;
+			atomic_inc(op->journal);
+
+			ret = bch_btree_insert(op, s);
+			if (ret)
+				goto err;
+
+			BUG_ON(!bch_keylist_empty(&op->keys));
+			keys++;
+
+			cond_resched();
+		}
+
+		if (i->pin)
+			atomic_dec(i->pin);
+		n = i->j.seq + 1;
+		entries++;
+	}
+
+	pr_info("journal replay done, %i keys in %i entries, seq %llu",
+		keys, entries, end);
+
+	while (!list_empty(list)) {
+		i = list_first_entry(list, struct journal_replay, list);
+		list_del(&i->list);
+		kfree(i);
+	}
+err:
+	closure_sync(&op->cl);
+	return ret;
+}
+
+/* Journalling */
+
+static void btree_flush_write(struct cache_set *c)
+{
+	/*
+	 * Try to find the btree node with that references the oldest journal
+	 * entry, best is our current candidate and is locked if non NULL:
+	 */
+	struct btree *b, *best = NULL;
+	unsigned iter;
+
+	for_each_cached_btree(b, c, iter) {
+		if (!down_write_trylock(&b->lock))
+			continue;
+
+		if (!btree_node_dirty(b) ||
+		    !btree_current_write(b)->journal) {
+			rw_unlock(true, b);
+			continue;
+		}
+
+		if (!best)
+			best = b;
+		else if (journal_pin_cmp(c,
+					 btree_current_write(best),
+					 btree_current_write(b))) {
+			rw_unlock(true, best);
+			best = b;
+		} else
+			rw_unlock(true, b);
+	}
+
+	if (best)
+		goto out;
+
+	/* We can't find the best btree node, just pick the first */
+	list_for_each_entry(b, &c->btree_cache, list)
+		if (!b->level && btree_node_dirty(b)) {
+			best = b;
+			rw_lock(true, best, best->level);
+			goto found;
+		}
+
+out:
+	if (!best)
+		return;
+found:
+	if (btree_node_dirty(best))
+		bch_btree_write(best, true, NULL);
+	rw_unlock(true, best);
+}
+
+#define last_seq(j)	((j)->seq - fifo_used(&(j)->pin) + 1)
+
+static void journal_discard_endio(struct bio *bio, int error)
+{
+	struct journal_device *ja =
+		container_of(bio, struct journal_device, discard_bio);
+	struct cache *ca = container_of(ja, struct cache, journal);
+
+	atomic_set(&ja->discard_in_flight, DISCARD_DONE);
+
+	closure_wake_up(&ca->set->journal.wait);
+	closure_put(&ca->set->cl);
+}
+
+static void journal_discard_work(struct work_struct *work)
+{
+	struct journal_device *ja =
+		container_of(work, struct journal_device, discard_work);
+
+	submit_bio(0, &ja->discard_bio);
+}
+
+static void do_journal_discard(struct cache *ca)
+{
+	struct journal_device *ja = &ca->journal;
+	struct bio *bio = &ja->discard_bio;
+
+	if (!ca->discard) {
+		ja->discard_idx = ja->last_idx;
+		return;
+	}
+
+	switch (atomic_read(&ja->discard_in_flight) == DISCARD_IN_FLIGHT) {
+	case DISCARD_IN_FLIGHT:
+		return;
+
+	case DISCARD_DONE:
+		ja->discard_idx = (ja->discard_idx + 1) %
+			ca->sb.njournal_buckets;
+
+		atomic_set(&ja->discard_in_flight, DISCARD_READY);
+		/* fallthrough */
+
+	case DISCARD_READY:
+		if (ja->discard_idx == ja->last_idx)
+			return;
+
+		atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);
+
+		bio_init(bio);
+		bio->bi_sector		= bucket_to_sector(ca->set,
+							   ca->sb.d[ja->discard_idx]);
+		bio->bi_bdev		= ca->bdev;
+		bio->bi_rw		= REQ_WRITE|REQ_DISCARD;
+		bio->bi_max_vecs	= 1;
+		bio->bi_io_vec		= bio->bi_inline_vecs;
+		bio->bi_size		= bucket_bytes(ca);
+		bio->bi_end_io		= journal_discard_endio;
+
+		closure_get(&ca->set->cl);
+		INIT_WORK(&ja->discard_work, journal_discard_work);
+		schedule_work(&ja->discard_work);
+	}
+}
+
+static void journal_reclaim(struct cache_set *c)
+{
+	struct bkey *k = &c->journal.key;
+	struct cache *ca;
+	uint64_t last_seq;
+	unsigned iter, n = 0;
+	atomic_t p;
+
+	while (!atomic_read(&fifo_front(&c->journal.pin)))
+		fifo_pop(&c->journal.pin, p);
+
+	last_seq = last_seq(&c->journal);
+
+	/* Update last_idx */
+
+	for_each_cache(ca, c, iter) {
+		struct journal_device *ja = &ca->journal;
+
+		while (ja->last_idx != ja->cur_idx &&
+		       ja->seq[ja->last_idx] < last_seq)
+			ja->last_idx = (ja->last_idx + 1) %
+				ca->sb.njournal_buckets;
+	}
+
+	for_each_cache(ca, c, iter)
+		do_journal_discard(ca);
+
+	if (c->journal.blocks_free)
+		return;
+
+	/*
+	 * Allocate:
+	 * XXX: Sort by free journal space
+	 */
+
+	for_each_cache(ca, c, iter) {
+		struct journal_device *ja = &ca->journal;
+		unsigned next = (ja->cur_idx + 1) % ca->sb.njournal_buckets;
+
+		/* No space available on this device */
+		if (next == ja->discard_idx)
+			continue;
+
+		ja->cur_idx = next;
+		k->ptr[n++] = PTR(0,
+				  bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
+				  ca->sb.nr_this_dev);
+	}
+
+	bkey_init(k);
+	SET_KEY_PTRS(k, n);
+
+	if (n)
+		c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
+
+	if (!journal_full(&c->journal))
+		__closure_wake_up(&c->journal.wait);
+}
+
+void bch_journal_next(struct journal *j)
+{
+	atomic_t p = { 1 };
+
+	j->cur = (j->cur == j->w)
+		? &j->w[1]
+		: &j->w[0];
+
+	/*
+	 * The fifo_push() needs to happen at the same time as j->seq is
+	 * incremented for last_seq() to be calculated correctly
+	 */
+	BUG_ON(!fifo_push(&j->pin, p));
+	atomic_set(&fifo_back(&j->pin), 1);
+
+	j->cur->data->seq	= ++j->seq;
+	j->cur->need_write	= false;
+	j->cur->data->keys	= 0;
+
+	if (fifo_full(&j->pin))
+		pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
+}
+
+static void journal_write_endio(struct bio *bio, int error)
+{
+	struct journal_write *w = bio->bi_private;
+
+	cache_set_err_on(error, w->c, "journal io error");
+	closure_put(&w->c->journal.io.cl);
+}
+
+static void journal_write(struct closure *);
+
+static void journal_write_done(struct closure *cl)
+{
+	struct journal *j = container_of(cl, struct journal, io.cl);
+	struct cache_set *c = container_of(j, struct cache_set, journal);
+
+	struct journal_write *w = (j->cur == j->w)
+		? &j->w[1]
+		: &j->w[0];
+
+	__closure_wake_up(&w->wait);
+
+	if (c->journal_delay_ms)
+		closure_delay(&j->io, msecs_to_jiffies(c->journal_delay_ms));
+
+	continue_at(cl, journal_write, system_wq);
+}
+
+static void journal_write_unlocked(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+	struct cache *ca;
+	struct journal_write *w = c->journal.cur;
+	struct bkey *k = &c->journal.key;
+	unsigned i, sectors = set_blocks(w->data, c) * c->sb.block_size;
+
+	struct bio *bio;
+	struct bio_list list;
+	bio_list_init(&list);
+
+	if (!w->need_write) {
+		/*
+		 * XXX: have to unlock closure before we unlock journal lock,
+		 * else we race with bch_journal(). But this way we race
+		 * against cache set unregister. Doh.
+		 */
+		set_closure_fn(cl, NULL, NULL);
+		closure_sub(cl, CLOSURE_RUNNING + 1);
+		spin_unlock(&c->journal.lock);
+		return;
+	} else if (journal_full(&c->journal)) {
+		journal_reclaim(c);
+		spin_unlock(&c->journal.lock);
+
+		btree_flush_write(c);
+		continue_at(cl, journal_write, system_wq);
+	}
+
+	c->journal.blocks_free -= set_blocks(w->data, c);
+
+	w->data->btree_level = c->root->level;
+
+	bkey_copy(&w->data->btree_root, &c->root->key);
+	bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
+
+	for_each_cache(ca, c, i)
+		w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
+
+	w->data->magic		= jset_magic(c);
+	w->data->version	= BCACHE_JSET_VERSION;
+	w->data->last_seq	= last_seq(&c->journal);
+	w->data->csum		= csum_set(w->data);
+
+	for (i = 0; i < KEY_PTRS(k); i++) {
+		ca = PTR_CACHE(c, k, i);
+		bio = &ca->journal.bio;
+
+		atomic_long_add(sectors, &ca->meta_sectors_written);
+
+		bio_reset(bio);
+		bio->bi_sector	= PTR_OFFSET(k, i);
+		bio->bi_bdev	= ca->bdev;
+		bio->bi_rw	= REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
+		bio->bi_size	= sectors << 9;
+
+		bio->bi_end_io	= journal_write_endio;
+		bio->bi_private = w;
+		bio_map(bio, w->data);
+
+		trace_bcache_journal_write(bio);
+		bio_list_add(&list, bio);
+
+		SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
+
+		ca->journal.seq[ca->journal.cur_idx] = w->data->seq;
+	}
+
+	atomic_dec_bug(&fifo_back(&c->journal.pin));
+	bch_journal_next(&c->journal);
+	journal_reclaim(c);
+
+	spin_unlock(&c->journal.lock);
+
+	while ((bio = bio_list_pop(&list)))
+		closure_bio_submit(bio, cl, c->cache[0]);
+
+	continue_at(cl, journal_write_done, NULL);
+}
+
+static void journal_write(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+
+	spin_lock(&c->journal.lock);
+	journal_write_unlocked(cl);
+}
+
+static void __journal_try_write(struct cache_set *c, bool noflush)
+{
+	struct closure *cl = &c->journal.io.cl;
+
+	if (!closure_trylock(cl, &c->cl))
+		spin_unlock(&c->journal.lock);
+	else if (noflush && journal_full(&c->journal)) {
+		spin_unlock(&c->journal.lock);
+		continue_at(cl, journal_write, system_wq);
+	} else
+		journal_write_unlocked(cl);
+}
+
+#define journal_try_write(c)	__journal_try_write(c, false)
+
+void bch_journal_meta(struct cache_set *c, struct closure *cl)
+{
+	struct journal_write *w;
+
+	if (CACHE_SYNC(&c->sb)) {
+		spin_lock(&c->journal.lock);
+
+		w = c->journal.cur;
+		w->need_write = true;
+
+		if (cl)
+			BUG_ON(!closure_wait(&w->wait, cl));
+
+		__journal_try_write(c, true);
+	}
+}
+
+/*
+ * Entry point to the journalling code - bio_insert() and btree_invalidate()
+ * pass bch_journal() a list of keys to be journalled, and then
+ * bch_journal() hands those same keys off to btree_insert_async()
+ */
+
+void bch_journal(struct closure *cl)
+{
+	struct btree_op *op = container_of(cl, struct btree_op, cl);
+	struct cache_set *c = op->c;
+	struct journal_write *w;
+	size_t b, n = ((uint64_t *) op->keys.top) - op->keys.list;
+
+	if (op->type != BTREE_INSERT ||
+	    !CACHE_SYNC(&c->sb))
+		goto out;
+
+	/*
+	 * If we're looping because we errored, might already be waiting on
+	 * another journal write:
+	 */
+	while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
+		closure_sync(cl->parent);
+
+	spin_lock(&c->journal.lock);
+
+	if (journal_full(&c->journal)) {
+		/* XXX: tracepoint */
+		closure_wait(&c->journal.wait, cl);
+
+		journal_reclaim(c);
+		spin_unlock(&c->journal.lock);
+
+		btree_flush_write(c);
+		continue_at(cl, bch_journal, bcache_wq);
+	}
+
+	w = c->journal.cur;
+	w->need_write = true;
+	b = __set_blocks(w->data, w->data->keys + n, c);
+
+	if (b * c->sb.block_size > PAGE_SECTORS << JSET_BITS ||
+	    b > c->journal.blocks_free) {
+		/* XXX: If we were inserting so many keys that they won't fit in
+		 * an _empty_ journal write, we'll deadlock. For now, handle
+		 * this in bch_keylist_realloc() - but something to think about.
+		 */
+		BUG_ON(!w->data->keys);
+
+		/* XXX: tracepoint */
+		BUG_ON(!closure_wait(&w->wait, cl));
+
+		closure_flush(&c->journal.io);
+
+		journal_try_write(c);
+		continue_at(cl, bch_journal, bcache_wq);
+	}
+
+	memcpy(end(w->data), op->keys.list, n * sizeof(uint64_t));
+	w->data->keys += n;
+
+	op->journal = &fifo_back(&c->journal.pin);
+	atomic_inc(op->journal);
+
+	if (op->flush_journal) {
+		closure_flush(&c->journal.io);
+		closure_wait(&w->wait, cl->parent);
+	}
+
+	journal_try_write(c);
+out:
+	bch_btree_insert_async(cl);
+}
+
+void bch_journal_free(struct cache_set *c)
+{
+	free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
+	free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
+	free_fifo(&c->journal.pin);
+}
+
+int bch_journal_alloc(struct cache_set *c)
+{
+	struct journal *j = &c->journal;
+
+	closure_init_unlocked(&j->io);
+	spin_lock_init(&j->lock);
+
+	c->journal_delay_ms = 100;
+
+	j->w[0].c = c;
+	j->w[1].c = c;
+
+	if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
+	    !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
+	    !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
+		return -ENOMEM;
+
+	return 0;
+}