Message-ID: <21580e04c66a20fc091c2cd426fb566802a1d943.1336619038.git.koverstreet@google.com>
Date:	Wed, 9 May 2012 23:11:13 -0400
From:	Kent Overstreet <koverstreet@...gle.com>
To:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com
Cc:	tejun@...gle.com, agk@...hat.com
Subject: [Bcache v13 13/16] bcache: Journalling

Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
---
 drivers/block/bcache/journal.c |  722 ++++++++++++++++++++++++++++++++++++++++
 drivers/block/bcache/journal.h |  113 +++++++
 2 files changed, 835 insertions(+), 0 deletions(-)
 create mode 100644 drivers/block/bcache/journal.c
 create mode 100644 drivers/block/bcache/journal.h

diff --git a/drivers/block/bcache/journal.c b/drivers/block/bcache/journal.c
new file mode 100644
index 0000000..2e43ab6
--- /dev/null
+++ b/drivers/block/bcache/journal.c
@@ -0,0 +1,722 @@
+
+#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;
+	bio_put(bio);
+	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->set->bio_split);
+		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 bcache_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;
+
+	for_each_cache(ca, c) {
+		struct journal_device *ja = &ca->journal;
+		unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
+		unsigned 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 (unsigned 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 (unsigned i = 0; i < ca->sb.njournal_buckets; i++)
+			if (ja->seq[i] > seq) {
+				seq = ja->seq[i];
+				ja->cur = ja->last = i;
+
+			}
+	}
+
+	c->journal.seq = list_entry(list->prev,
+				    struct journal_replay,
+				    list)->j.seq;
+
+	return 0;
+#undef read_bucket
+}
+
+void bcache_journal_mark(struct cache_set *c, struct list_head *list)
+{
+	atomic_t p = { 0 };
+	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 (struct bkey *k = i->j.start; k < end(&i->j); k = next(k)) {
+			for (unsigned 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;
+			}
+
+			__btree_mark_key(c, 0, k);
+		}
+	}
+}
+
+int bcache_journal_replay(struct cache_set *s, struct list_head *list,
+			  struct btree_op *op)
+{
+	int ret = 0, keys = 0, entries = 0;
+	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)
+			err_printk("journal entries %llu-%llu "
+				   "missing! (replaying %llu-%llu)\n",
+				   n, i->j.seq - 1, start, end);
+
+		for (struct bkey *k = i->j.start; k < end(&i->j); k = next(k)) {
+			pr_debug("%s", pkey(k));
+			bkey_copy(op->keys.top, k);
+			keylist_push(&op->keys);
+
+			op->journal = i->pin;
+			atomic_inc(op->journal);
+
+			ret = bcache_btree_insert(op, s);
+			if (ret)
+				goto err;
+
+			BUG_ON(!keylist_empty(&op->keys));
+			keys++;
+		}
+
+		if (i->pin)
+			atomic_dec(i->pin);
+		n = i->j.seq + 1;
+		entries++;
+	}
+
+	printk(KERN_INFO "bcache: journal replay done, %i keys in %i "
+	       "entries, seq %llu-%llu\n", keys, entries, start, 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;
+
+	/*
+	 * The root of the btree isn't on the lru list. Normally this is fine
+	 * because only leaf nodes can have references to journal entries -
+	 * unless the root _is_ a leaf node. So we have to special case that:
+	 */
+
+	while (!c->root->level) {
+		best = c->root;
+		rw_lock(true, best, 0);
+
+		if (best == c->root && !best->level)
+			goto found;
+		rw_unlock(true, best);
+	}
+
+	mutex_lock(&c->bucket_lock);
+
+	best = NULL;
+	list_for_each_entry(b, &c->btree_cache, list) {
+		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;
+			mutex_unlock(&c->bucket_lock);
+			rw_lock(true, best, best->level);
+			goto found;
+		}
+
+out:
+	mutex_unlock(&c->bucket_lock);
+
+	if (!best)
+		return;
+found:
+	if (btree_node_dirty(best))
+		btree_write(best, true, NULL);
+	rw_unlock(true, best);
+}
+
+#define last_seq(j)	((j)->seq - fifo_used(&(j)->pin) + 1)
+
+static void journal_reclaim(struct cache_set *c)
+{
+	struct bkey *k = &c->journal.key;
+	struct cache *ca;
+	uint64_t last_seq;
+	unsigned 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);
+
+	for_each_cache(ca, c) {
+		struct journal_device *ja = &ca->journal;
+
+		while (ja->last != ja->cur &&
+		       ja->seq[ja->last] < last_seq)
+			if (++ja->last == ca->sb.njournal_buckets)
+				ja->last = 0;
+	}
+
+	if (c->journal.blocks_free)
+		return;
+
+	/*
+	 * Now we allocate:
+	 * XXX: Sort by free journal space
+	 */
+
+	for_each_cache(ca, c) {
+		struct journal_device *ja = &ca->journal;
+		unsigned next = (ja->cur + 1) % ca->sb.njournal_buckets;
+
+		if (next == ja->last)
+			continue;
+
+		ja->cur = next;
+		k->ptr[n++] = PTR(0,
+				  bucket_to_sector(c, ca->sb.d[ja->cur]),
+				  ca->sb.nr_this_dev);
+	}
+
+	k->header = KEY_HEADER(0, 0);
+	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 bcache_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");
+
+	bio_put(bio);
+	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_sleep(&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 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 bcache_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)
+		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 (unsigned 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] = w->data->seq;
+	}
+
+	atomic_dec_bug(&fifo_back(&c->journal.pin));
+	bcache_journal_next(&c->journal);
+	journal_reclaim(c);
+
+	spin_unlock(&c->journal.lock);
+
+	while ((bio = bio_list_pop(&list)))
+		closure_bio_submit(bio, cl, c->bio_split);
+
+	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 bcache_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 bcache_journal() a list of keys to be journalled, and then
+ * bcache_journal() hands those same keys off to btree_insert_async()
+ */
+
+void bcache_journal(struct closure *cl)
+{
+	struct btree_op *op = container_of(cl, struct btree_op, cl);
+	struct cache_set *c = op->d->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, bcache_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 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, bcache_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:
+	bcache_btree_insert_async(cl);
+}
+
+void bcache_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 bcache_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;
+}
diff --git a/drivers/block/bcache/journal.h b/drivers/block/bcache/journal.h
new file mode 100644
index 0000000..eb829e9
--- /dev/null
+++ b/drivers/block/bcache/journal.h
@@ -0,0 +1,113 @@
+#ifndef _BCACHE_JOURNAL_H
+#define _BCACHE_JOURNAL_H
+
+#define BCACHE_JSET_VERSION_UUIDv1	1
+/* Always latest UUID format */
+#define BCACHE_JSET_VERSION_UUID	1
+#define BCACHE_JSET_VERSION		1
+
+/*
+ * On disk format for a journal entry:
+ * seq is monotonically increasing; every journal entry has its own unique
+ * sequence number.
+ *
+ * last_seq is the oldest journal entry that still has keys the btree hasn't
+ * flushed to disk yet.
+ *
+ * version is for on disk format changes.
+ */
+struct jset {
+	uint64_t		csum;
+	uint64_t		magic;
+	uint64_t		seq;
+	uint32_t		version;
+	uint32_t		keys;
+
+	uint64_t		last_seq;
+
+	BKEY_PADDED(uuid_bucket);
+	BKEY_PADDED(btree_root);
+	uint16_t		btree_level;
+	uint16_t		pad[3];
+
+	uint64_t		prio_bucket[MAX_CACHES_PER_SET];
+
+	union {
+		struct bkey	start[0];
+		uint64_t	d[0];
+	};
+};
+
+/*
+ * Only used for holding the journal entries we read in btree_journal_read()
+ * during cache_registration
+ */
+struct journal_replay {
+	struct list_head	list;
+	atomic_t		*pin;
+	struct jset		j;
+};
+
+/*
+ * We put two of these in struct journal; we used them for writes to the
+ * journal that are being staged or in flight.
+ */
+struct journal_write {
+	struct jset		*data;
+#define JSET_BITS		3
+
+	struct cache_set	*c;
+	closure_list_t		wait;
+	bool			need_write;
+};
+
+struct journal {
+	spinlock_t		lock;
+	/* used when waiting because the journal was full */
+	closure_list_t		wait;
+	struct closure_with_timer io;
+
+	unsigned		blocks_free;
+	uint64_t		seq;
+	DECLARE_FIFO(atomic_t, pin);
+
+	BKEY_PADDED(key);
+
+	struct journal_write	w[2], *cur;
+};
+
+struct journal_device {
+	unsigned		cur;
+	unsigned		last;
+	uint64_t		seq[SB_JOURNAL_BUCKETS];
+
+	struct bio		bio;
+	struct bio_vec		bv[8];
+};
+
+#define journal_pin_cmp(c, l, r)				\
+	(fifo_idx(&(c)->journal.pin, (l)->journal) >		\
+	 fifo_idx(&(c)->journal.pin, (r)->journal))
+
+#define JOURNAL_PIN	20000
+
+#define journal_full(j)						\
+	(!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)
+
+struct closure;
+struct cache_set;
+struct btree_op;
+
+void bcache_journal(struct closure *);
+void bcache_journal_next(struct journal *);
+void bcache_journal_mark(struct cache_set *, struct list_head *);
+void bcache_journal_meta(struct cache_set *, struct closure *);
+int bcache_journal_read(struct cache_set *, struct list_head *,
+			struct btree_op *);
+int bcache_journal_replay(struct cache_set *, struct list_head *,
+			  struct btree_op *);
+
+void bcache_journal_free(struct cache_set *);
+int bcache_journal_alloc(struct cache_set *);
+
+#endif /* _BCACHE_JOURNAL_H */
-- 
1.7.9.rc2

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