Merge with 1f431b384d bcachefs: Refactor trans_(get|update)_key

1 files changed, 540 insertions, 396 deletions

diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index addd51f08c9a..5c3e146e3942 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * bcachefs journalling code, for btree insertions
  *
@@ -5,7 +6,7 @@
  */
 
 #include "bcachefs.h"
-#include "alloc.h"
+#include "alloc_foreground.h"
 #include "bkey_methods.h"
 #include "btree_gc.h"
 #include "buckets.h"
@@ -17,29 +18,14 @@
 
 #include <trace/events/bcachefs.h>
 
-static bool journal_entry_is_open(struct journal *j)
+static bool __journal_entry_is_open(union journal_res_state state)
 {
-	return j->reservations.cur_entry_offset < JOURNAL_ENTRY_CLOSED_VAL;
+	return state.cur_entry_offset < JOURNAL_ENTRY_CLOSED_VAL;
 }
 
-void bch2_journal_buf_put_slowpath(struct journal *j, bool need_write_just_set)
+static bool journal_entry_is_open(struct journal *j)
 {
-	struct journal_buf *w = journal_prev_buf(j);
-
-	atomic_dec_bug(&journal_seq_pin(j, le64_to_cpu(w->data->seq))->count);
-
-	if (!need_write_just_set &&
-	    test_bit(JOURNAL_NEED_WRITE, &j->flags))
-		bch2_time_stats_update(j->delay_time,
-				       j->need_write_time);
-#if 0
-	closure_call(&j->io, bch2_journal_write, NULL, NULL);
-#else
-	/* Shut sparse up: */
-	closure_init(&j->io, NULL);
-	set_closure_fn(&j->io, bch2_journal_write, NULL);
-	bch2_journal_write(&j->io);
-#endif
+	return __journal_entry_is_open(j->reservations);
 }
 
 static void journal_pin_new_entry(struct journal *j, int count)
@@ -70,41 +56,71 @@ static void bch2_journal_buf_init(struct journal *j)
 	buf->data->u64s	= 0;
 }
 
-static inline size_t journal_entry_u64s_reserve(struct journal_buf *buf)
+void bch2_journal_halt(struct journal *j)
 {
-	return BTREE_ID_NR * (JSET_KEYS_U64s + BKEY_EXTENT_U64s_MAX);
+	union journal_res_state old, new;
+	u64 v = atomic64_read(&j->reservations.counter);
+
+	do {
+		old.v = new.v = v;
+		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
+			return;
+
+		new.cur_entry_offset = JOURNAL_ENTRY_ERROR_VAL;
+	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
+				       old.v, new.v)) != old.v);
+
+	journal_wake(j);
+	closure_wake_up(&journal_cur_buf(j)->wait);
 }
 
-static enum {
-	JOURNAL_ENTRY_ERROR,
-	JOURNAL_ENTRY_INUSE,
-	JOURNAL_ENTRY_CLOSED,
-	JOURNAL_UNLOCKED,
-} journal_buf_switch(struct journal *j, bool need_write_just_set)
+/* journal entry close/open: */
+
+void __bch2_journal_buf_put(struct journal *j, bool need_write_just_set)
+{
+	if (!need_write_just_set &&
+	    test_bit(JOURNAL_NEED_WRITE, &j->flags))
+		bch2_time_stats_update(j->delay_time,
+				       j->need_write_time);
+
+	clear_bit(JOURNAL_NEED_WRITE, &j->flags);
+
+	closure_call(&j->io, bch2_journal_write, system_highpri_wq, NULL);
+}
+
+/*
+ * Returns true if journal entry is now closed:
+ */
+static bool __journal_entry_close(struct journal *j)
 {
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
-	struct journal_buf *buf;
+	struct journal_buf *buf = journal_cur_buf(j);
 	union journal_res_state old, new;
 	u64 v = atomic64_read(&j->reservations.counter);
+	bool set_need_write = false;
+	unsigned sectors;
 
 	lockdep_assert_held(&j->lock);
 
 	do {
 		old.v = new.v = v;
 		if (old.cur_entry_offset == JOURNAL_ENTRY_CLOSED_VAL)
-			return JOURNAL_ENTRY_CLOSED;
+			return true;
 
-		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
-			return JOURNAL_ENTRY_ERROR;
+		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL) {
+			/* this entry will never be written: */
+			closure_wake_up(&buf->wait);
+			return true;
+		}
 
-		if (new.prev_buf_unwritten)
-			return JOURNAL_ENTRY_INUSE;
+		if (!test_bit(JOURNAL_NEED_WRITE, &j->flags)) {
+			set_bit(JOURNAL_NEED_WRITE, &j->flags);
+			j->need_write_time = local_clock();
+			set_need_write = true;
+		}
 
-		/*
-		 * avoid race between setting buf->data->u64s and
-		 * journal_res_put starting write:
-		 */
-		journal_state_inc(&new);
+		if (new.prev_buf_unwritten)
+			return false;
 
 		new.cur_entry_offset = JOURNAL_ENTRY_CLOSED_VAL;
 		new.idx++;
@@ -114,59 +130,62 @@ static enum {
 	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
 				       old.v, new.v)) != old.v);
 
-	clear_bit(JOURNAL_NEED_WRITE, &j->flags);
-
-	buf = &j->buf[old.idx];
 	buf->data->u64s		= cpu_to_le32(old.cur_entry_offset);
 
-	j->prev_buf_sectors =
-		vstruct_blocks_plus(buf->data, c->block_bits,
-				    journal_entry_u64s_reserve(buf)) *
-		c->opts.block_size;
-	BUG_ON(j->prev_buf_sectors > j->cur_buf_sectors);
+	sectors = vstruct_blocks_plus(buf->data, c->block_bits,
+				      buf->u64s_reserved) << c->block_bits;
+	BUG_ON(sectors > buf->sectors);
+	buf->sectors = sectors;
+
+	bkey_extent_init(&buf->key);
 
-	bch2_journal_reclaim_fast(j);
-	/* XXX: why set this here, and not in bch2_journal_write()? */
+	/*
+	 * We have to set last_seq here, _before_ opening a new journal entry:
+	 *
+	 * A threads may replace an old pin with a new pin on their current
+	 * journal reservation - the expectation being that the journal will
+	 * contain either what the old pin protected or what the new pin
+	 * protects.
+	 *
+	 * After the old pin is dropped journal_last_seq() won't include the old
+	 * pin, so we can only write the updated last_seq on the entry that
+	 * contains whatever the new pin protects.
+	 *
+	 * Restated, we can _not_ update last_seq for a given entry if there
+	 * could be a newer entry open with reservations/pins that have been
+	 * taken against it.
+	 *
+	 * Hence, we want update/set last_seq on the current journal entry right
+	 * before we open a new one:
+	 */
 	buf->data->last_seq	= cpu_to_le64(journal_last_seq(j));
 
+	if (journal_entry_empty(buf->data))
+		clear_bit(JOURNAL_NOT_EMPTY, &j->flags);
+	else
+		set_bit(JOURNAL_NOT_EMPTY, &j->flags);
+
 	journal_pin_new_entry(j, 1);
 
 	bch2_journal_buf_init(j);
 
 	cancel_delayed_work(&j->write_work);
-	spin_unlock(&j->lock);
-
-	if (c->bucket_journal_seq > 1 << 14) {
-		c->bucket_journal_seq = 0;
-		bch2_bucket_seq_cleanup(c);
-	}
 
-	c->bucket_journal_seq++;
+	bch2_journal_space_available(j);
 
-	/* ugh - might be called from __journal_res_get() under wait_event() */
-	__set_current_state(TASK_RUNNING);
-	bch2_journal_buf_put(j, old.idx, need_write_just_set);
-
-	return JOURNAL_UNLOCKED;
+	bch2_journal_buf_put(j, old.idx, set_need_write);
+	return true;
 }
 
-void bch2_journal_halt(struct journal *j)
+static bool journal_entry_close(struct journal *j)
 {
-	union journal_res_state old, new;
-	u64 v = atomic64_read(&j->reservations.counter);
-
-	do {
-		old.v = new.v = v;
-		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
-			return;
+	bool ret;
 
-		new.cur_entry_offset = JOURNAL_ENTRY_ERROR_VAL;
-	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
-				       old.v, new.v)) != old.v);
+	spin_lock(&j->lock);
+	ret = __journal_entry_close(j);
+	spin_unlock(&j->lock);
 
-	journal_wake(j);
-	closure_wake_up(&journal_cur_buf(j)->wait);
-	closure_wake_up(&journal_prev_buf(j)->wait);
+	return ret;
 }
 
 /*
@@ -174,49 +193,39 @@ void bch2_journal_halt(struct journal *j)
  * journal reservation - journal entry is open means journal is dirty:
  *
  * returns:
- * 1:		success
- * 0:		journal currently full (must wait)
- * -EROFS:	insufficient rw devices
- * -EIO:	journal error
+ * 0:		success
+ * -ENOSPC:	journal currently full, must invoke reclaim
+ * -EAGAIN:	journal blocked, must wait
+ * -EROFS:	insufficient rw devices or journal error
  */
 static int journal_entry_open(struct journal *j)
 {
 	struct journal_buf *buf = journal_cur_buf(j);
 	union journal_res_state old, new;
-	ssize_t u64s;
-	int sectors;
+	int u64s;
 	u64 v;
 
 	lockdep_assert_held(&j->lock);
 	BUG_ON(journal_entry_is_open(j));
 
-	if (!fifo_free(&j->pin))
-		return 0;
-
-	sectors = bch2_journal_entry_sectors(j);
-	if (sectors <= 0)
-		return sectors;
+	if (j->blocked)
+		return -EAGAIN;
 
-	buf->disk_sectors	= sectors;
+	if (j->cur_entry_error)
+		return j->cur_entry_error;
 
-	sectors = min_t(unsigned, sectors, buf->size >> 9);
-	j->cur_buf_sectors	= sectors;
+	BUG_ON(!j->cur_entry_sectors);
 
-	u64s = (sectors << 9) / sizeof(u64);
+	buf->u64s_reserved	= j->entry_u64s_reserved;
+	buf->disk_sectors	= j->cur_entry_sectors;
+	buf->sectors		= min(buf->disk_sectors, buf->buf_size >> 9);
 
-	/* Subtract the journal header */
-	u64s -= sizeof(struct jset) / sizeof(u64);
-	/*
-	 * Btree roots, prio pointers don't get added until right before we do
-	 * the write:
-	 */
-	u64s -= journal_entry_u64s_reserve(buf);
-	u64s  = max_t(ssize_t, 0L, u64s);
-
-	BUG_ON(u64s >= JOURNAL_ENTRY_CLOSED_VAL);
+	u64s = (int) (buf->sectors << 9) / sizeof(u64) -
+		journal_entry_overhead(j);
+	u64s  = clamp_t(int, u64s, 0, JOURNAL_ENTRY_CLOSED_VAL - 1);
 
 	if (u64s <= le32_to_cpu(buf->data->u64s))
-		return 0;
+		return -ENOSPC;
 
 	/*
 	 * Must be set before marking the journal entry as open:
@@ -228,10 +237,13 @@ static int journal_entry_open(struct journal *j)
 		old.v = new.v = v;
 
 		if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL)
-			return -EIO;
+			return -EROFS;
 
 		/* Handle any already added entries */
 		new.cur_entry_offset = le32_to_cpu(buf->data->u64s);
+
+		EBUG_ON(journal_state_count(new, new.idx));
+		journal_state_inc(&new);
 	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
 				       old.v, new.v)) != old.v);
 
@@ -244,37 +256,29 @@ static int journal_entry_open(struct journal *j)
 			 &j->write_work,
 			 msecs_to_jiffies(j->write_delay_ms));
 	journal_wake(j);
-	return 1;
+	return 0;
 }
 
-/*
- * returns true if there's nothing to flush and no journal write still in flight
- */
-static bool journal_flush_write(struct journal *j)
+static bool journal_quiesced(struct journal *j)
 {
-	bool ret;
-
-	spin_lock(&j->lock);
-	ret = !j->reservations.prev_buf_unwritten;
-
-	if (!journal_entry_is_open(j)) {
-		spin_unlock(&j->lock);
-		return ret;
-	}
+	union journal_res_state state = READ_ONCE(j->reservations);
+	bool ret = !state.prev_buf_unwritten && !__journal_entry_is_open(state);
 
-	set_bit(JOURNAL_NEED_WRITE, &j->flags);
-	if (journal_buf_switch(j, false) == JOURNAL_UNLOCKED)
-		ret = false;
-	else
-		spin_unlock(&j->lock);
+	if (!ret)
+		journal_entry_close(j);
 	return ret;
 }
 
+static void journal_quiesce(struct journal *j)
+{
+	wait_event(j->wait, journal_quiesced(j));
+}
+
 static void journal_write_work(struct work_struct *work)
 {
 	struct journal *j = container_of(work, struct journal, write_work.work);
 
-	journal_flush_write(j);
+	journal_entry_close(j);
 }
 
 /*
@@ -302,26 +306,39 @@ u64 bch2_inode_journal_seq(struct journal *j, u64 inode)
 }
 
 static int __journal_res_get(struct journal *j, struct journal_res *res,
-			      unsigned u64s_min, unsigned u64s_max)
+			     unsigned flags)
 {
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
 	struct journal_buf *buf;
+	bool can_discard;
 	int ret;
 retry:
-	ret = journal_res_get_fast(j, res, u64s_min, u64s_max);
-	if (ret)
-		return ret;
+	if (journal_res_get_fast(j, res, flags))
+		return 0;
+
+	if (bch2_journal_error(j))
+		return -EROFS;
 
 	spin_lock(&j->lock);
+
 	/*
 	 * Recheck after taking the lock, so we don't race with another thread
 	 * that just did journal_entry_open() and call journal_entry_close()
 	 * unnecessarily
 	 */
-	ret = journal_res_get_fast(j, res, u64s_min, u64s_max);
-	if (ret) {
+	if (journal_res_get_fast(j, res, flags)) {
 		spin_unlock(&j->lock);
-		return 1;
+		return 0;
+	}
+
+	if (!(flags & JOURNAL_RES_GET_RESERVED) &&
+	    !test_bit(JOURNAL_MAY_GET_UNRESERVED, &j->flags)) {
+		/*
+		 * Don't want to close current journal entry, just need to
+		 * invoke reclaim:
+		 */
+		ret = -ENOSPC;
+		goto unlock;
 	}
 
 	/*
@@ -331,51 +348,58 @@ retry:
 	 */
 	buf = journal_cur_buf(j);
 	if (journal_entry_is_open(j) &&
-	    buf->size >> 9 < buf->disk_sectors &&
-	    buf->size < JOURNAL_ENTRY_SIZE_MAX)
-		j->buf_size_want = max(j->buf_size_want, buf->size << 1);
+	    buf->buf_size >> 9 < buf->disk_sectors &&
+	    buf->buf_size < JOURNAL_ENTRY_SIZE_MAX)
+		j->buf_size_want = max(j->buf_size_want, buf->buf_size << 1);
 
-	/*
-	 * Close the current journal entry if necessary, then try to start a new
-	 * one:
-	 */
-	switch (journal_buf_switch(j, false)) {
-	case JOURNAL_ENTRY_ERROR:
-		spin_unlock(&j->lock);
-		return -EROFS;
-	case JOURNAL_ENTRY_INUSE:
-		/* haven't finished writing out the previous one: */
-		spin_unlock(&j->lock);
+	if (journal_entry_is_open(j) &&
+	    !__journal_entry_close(j)) {
+		/*
+		 * We failed to get a reservation on the current open journal
+		 * entry because it's full, and we can't close it because
+		 * there's still a previous one in flight:
+		 */
 		trace_journal_entry_full(c);
-		goto blocked;
-	case JOURNAL_ENTRY_CLOSED:
-		break;
-	case JOURNAL_UNLOCKED:
-		goto retry;
+		ret = -EAGAIN;
+	} else {
+		ret = journal_entry_open(j);
 	}
+unlock:
+	if ((ret == -EAGAIN || ret == -ENOSPC) &&
+	    !j->res_get_blocked_start)
+		j->res_get_blocked_start = local_clock() ?: 1;
 
-	/* We now have a new, closed journal buf - see if we can open it: */
-	ret = journal_entry_open(j);
+	can_discard = j->can_discard;
 	spin_unlock(&j->lock);
 
-	if (ret < 0)
-		return ret;
-	if (ret)
+	if (!ret)
 		goto retry;
 
-	/* Journal's full, we have to wait */
+	if (ret == -ENOSPC) {
+		BUG_ON(!can_discard && (flags & JOURNAL_RES_GET_RESERVED));
 
-	/*
-	 * Direct reclaim - can't rely on reclaim from work item
-	 * due to freezing..
-	 */
-	bch2_journal_reclaim_work(&j->reclaim_work.work);
+		/*
+		 * Journal is full - can't rely on reclaim from work item due to
+		 * freezing:
+		 */
+		trace_journal_full(c);
 
-	trace_journal_full(c);
-blocked:
-	if (!j->res_get_blocked_start)
-		j->res_get_blocked_start = local_clock() ?: 1;
-	return 0;
+		if (!(flags & JOURNAL_RES_GET_NONBLOCK)) {
+			if (can_discard) {
+				bch2_journal_do_discards(j);
+				goto retry;
+			}
+
+			if (mutex_trylock(&j->reclaim_lock)) {
+				bch2_journal_reclaim(j);
+				mutex_unlock(&j->reclaim_lock);
+			}
+		}
+
+		ret = -EAGAIN;
+	}
+
+	return ret;
 }
 
 /*
@@ -389,16 +413,78 @@ blocked:
  * btree node write locks.
  */
 int bch2_journal_res_get_slowpath(struct journal *j, struct journal_res *res,
-				 unsigned u64s_min, unsigned u64s_max)
+				  unsigned flags)
 {
 	int ret;
 
-	wait_event(j->wait,
-		   (ret = __journal_res_get(j, res, u64s_min,
-					    u64s_max)));
-	return ret < 0 ? ret : 0;
+	closure_wait_event(&j->async_wait,
+		   (ret = __journal_res_get(j, res, flags)) != -EAGAIN ||
+		   (flags & JOURNAL_RES_GET_NONBLOCK));
+	return ret;
 }
 
+/* journal_preres: */
+
+static bool journal_preres_available(struct journal *j,
+				     struct journal_preres *res,
+				     unsigned new_u64s)
+{
+	bool ret = bch2_journal_preres_get_fast(j, res, new_u64s);
+
+	if (!ret)
+		bch2_journal_reclaim_work(&j->reclaim_work.work);
+
+	return ret;
+}
+
+int __bch2_journal_preres_get(struct journal *j,
+			      struct journal_preres *res,
+			      unsigned new_u64s)
+{
+	int ret;
+
+	closure_wait_event(&j->preres_wait,
+		   (ret = bch2_journal_error(j)) ||
+		   journal_preres_available(j, res, new_u64s));
+	return ret;
+}
+
+/* journal_entry_res: */
+
+void bch2_journal_entry_res_resize(struct journal *j,
+				   struct journal_entry_res *res,
+				   unsigned new_u64s)
+{
+	union journal_res_state state;
+	int d = new_u64s - res->u64s;
+
+	spin_lock(&j->lock);
+
+	j->entry_u64s_reserved += d;
+	if (d <= 0)
+		goto out;
+
+	j->cur_entry_u64s = max_t(int, 0, j->cur_entry_u64s - d);
+	smp_mb();
+	state = READ_ONCE(j->reservations);
+
+	if (state.cur_entry_offset < JOURNAL_ENTRY_CLOSED_VAL &&
+	    state.cur_entry_offset > j->cur_entry_u64s) {
+		j->cur_entry_u64s += d;
+		/*
+		 * Not enough room in current journal entry, have to flush it:
+		 */
+		__journal_entry_close(j);
+	} else {
+		journal_cur_buf(j)->u64s_reserved += d;
+	}
+out:
+	spin_unlock(&j->lock);
+	res->u64s += d;
+}
+
+/* journal flushing: */
+
 u64 bch2_journal_last_unwritten_seq(struct journal *j)
 {
 	u64 seq;
@@ -420,30 +506,84 @@ u64 bch2_journal_last_unwritten_seq(struct journal *j)
  * btree root - every journal entry contains the roots of all the btrees, so it
  * doesn't need to bother with getting a journal reservation
  */
-int bch2_journal_open_seq_async(struct journal *j, u64 seq, struct closure *parent)
+int bch2_journal_open_seq_async(struct journal *j, u64 seq, struct closure *cl)
 {
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
 	int ret;
 
 	spin_lock(&j->lock);
-	BUG_ON(seq > journal_cur_seq(j));
 
-	if (seq < journal_cur_seq(j) ||
+	/*
+	 * Can't try to open more than one sequence number ahead:
+	 */
+	BUG_ON(journal_cur_seq(j) < seq && !journal_entry_is_open(j));
+
+	if (journal_cur_seq(j) > seq ||
 	    journal_entry_is_open(j)) {
 		spin_unlock(&j->lock);
-		return 1;
+		return 0;
 	}
 
-	ret = journal_entry_open(j);
-	if (!ret)
-		closure_wait(&j->async_wait, parent);
+	if (journal_cur_seq(j) < seq &&
+	    !__journal_entry_close(j)) {
+		/* haven't finished writing out the previous one: */
+		trace_journal_entry_full(c);
+		ret = -EAGAIN;
+	} else {
+		BUG_ON(journal_cur_seq(j) != seq);
+
+		ret = journal_entry_open(j);
+	}
+
+	if ((ret == -EAGAIN || ret == -ENOSPC) &&
+	    !j->res_get_blocked_start)
+		j->res_get_blocked_start = local_clock() ?: 1;
+
+	if (ret == -EAGAIN || ret == -ENOSPC)
+		closure_wait(&j->async_wait, cl);
+
 	spin_unlock(&j->lock);
 
-	if (!ret)
+	if (ret == -ENOSPC) {
+		trace_journal_full(c);
 		bch2_journal_reclaim_work(&j->reclaim_work.work);
+		ret = -EAGAIN;
+	}
 
 	return ret;
 }
 
+static int journal_seq_error(struct journal *j, u64 seq)
+{
+	union journal_res_state state = READ_ONCE(j->reservations);
+
+	if (seq == journal_cur_seq(j))
+		return bch2_journal_error(j);
+
+	if (seq + 1 == journal_cur_seq(j) &&
+	    !state.prev_buf_unwritten &&
+	    seq > j->seq_ondisk)
+		return -EIO;
+
+	return 0;
+}
+
+static inline struct journal_buf *
+journal_seq_to_buf(struct journal *j, u64 seq)
+{
+	/* seq should be for a journal entry that has been opened: */
+	BUG_ON(seq > journal_cur_seq(j));
+	BUG_ON(seq == journal_cur_seq(j) &&
+	       j->reservations.cur_entry_offset == JOURNAL_ENTRY_CLOSED_VAL);
+
+	if (seq == journal_cur_seq(j))
+		return journal_cur_buf(j);
+	if (seq + 1 == journal_cur_seq(j) &&
+	    j->reservations.prev_buf_unwritten)
+		return journal_prev_buf(j);
+	return NULL;
+}
+
 /**
  * bch2_journal_wait_on_seq - wait for a journal entry to be written
  *
@@ -452,31 +592,22 @@ int bch2_journal_open_seq_async(struct journal *j, u64 seq, struct closure *pare
  * can wait for an arbitrary amount of time (up to @j->write_delay_ms, which is
  * configurable).
  */
-void bch2_journal_wait_on_seq(struct journal *j, u64 seq, struct closure *parent)
+void bch2_journal_wait_on_seq(struct journal *j, u64 seq,
+			      struct closure *parent)
 {
-	spin_lock(&j->lock);
-
-	BUG_ON(seq > journal_cur_seq(j));
+	struct journal_buf *buf;
 
-	if (bch2_journal_error(j)) {
-		spin_unlock(&j->lock);
-		return;
-	}
+	spin_lock(&j->lock);
 
-	if (seq == journal_cur_seq(j)) {
-		if (!closure_wait(&journal_cur_buf(j)->wait, parent))
-			BUG();
-	} else if (seq + 1 == journal_cur_seq(j) &&
-		   j->reservations.prev_buf_unwritten) {
-		if (!closure_wait(&journal_prev_buf(j)->wait, parent))
+	if ((buf = journal_seq_to_buf(j, seq))) {
+		if (!closure_wait(&buf->wait, parent))
 			BUG();
 
-		smp_mb();
-
-		/* check if raced with write completion (or failure) */
-		if (!j->reservations.prev_buf_unwritten ||
-		    bch2_journal_error(j))
-			closure_wake_up(&journal_prev_buf(j)->wait);
+		if (seq == journal_cur_seq(j)) {
+			smp_mb();
+			if (bch2_journal_error(j))
+				closure_wake_up(&buf->wait);
+		}
 	}
 
 	spin_unlock(&j->lock);
@@ -488,107 +619,32 @@ void bch2_journal_wait_on_seq(struct journal *j, u64 seq, struct closure *parent
  * like bch2_journal_wait_on_seq, except that it triggers a write immediately if
  * necessary
  */
-void bch2_journal_flush_seq_async(struct journal *j, u64 seq, struct closure *parent)
+void bch2_journal_flush_seq_async(struct journal *j, u64 seq,
+				  struct closure *parent)
 {
 	struct journal_buf *buf;
 
 	spin_lock(&j->lock);
 
-	BUG_ON(seq > journal_cur_seq(j));
-
-	if (bch2_journal_error(j)) {
-		spin_unlock(&j->lock);
-		return;
-	}
-
-	if (seq == journal_cur_seq(j)) {
-		bool set_need_write = false;
-
-		buf = journal_cur_buf(j);
-
-		if (parent && !closure_wait(&buf->wait, parent))
-			BUG();
-
-		if (!test_and_set_bit(JOURNAL_NEED_WRITE, &j->flags)) {
-			j->need_write_time = local_clock();
-			set_need_write = true;
-		}
-
-		switch (journal_buf_switch(j, set_need_write)) {
-		case JOURNAL_ENTRY_ERROR:
-			if (parent)
-				closure_wake_up(&buf->wait);
-			break;
-		case JOURNAL_ENTRY_CLOSED:
-			/*
-			 * Journal entry hasn't been opened yet, but caller
-			 * claims it has something
-			 */
-			BUG();
-		case JOURNAL_ENTRY_INUSE:
-			break;
-		case JOURNAL_UNLOCKED:
-			return;
-		}
-	} else if (parent &&
-		   seq + 1 == journal_cur_seq(j) &&
-		   j->reservations.prev_buf_unwritten) {
-		buf = journal_prev_buf(j);
-
+	if (parent &&
+	    (buf = journal_seq_to_buf(j, seq)))
 		if (!closure_wait(&buf->wait, parent))
 			BUG();
 
-		smp_mb();
-
-		/* check if raced with write completion (or failure) */
-		if (!j->reservations.prev_buf_unwritten ||
-		    bch2_journal_error(j))
-			closure_wake_up(&buf->wait);
-	}
-
+	if (seq == journal_cur_seq(j))
+		__journal_entry_close(j);
 	spin_unlock(&j->lock);
 }
 
 static int journal_seq_flushed(struct journal *j, u64 seq)
 {
-	struct journal_buf *buf;
-	int ret = 1;
+	int ret;
 
 	spin_lock(&j->lock);
-	BUG_ON(seq > journal_cur_seq(j));
-
-	if (seq == journal_cur_seq(j)) {
-		bool set_need_write = false;
-
-		ret = 0;
-
-		buf = journal_cur_buf(j);
-
-		if (!test_and_set_bit(JOURNAL_NEED_WRITE, &j->flags)) {
-			j->need_write_time = local_clock();
-			set_need_write = true;
-		}
-
-		switch (journal_buf_switch(j, set_need_write)) {
-		case JOURNAL_ENTRY_ERROR:
-			ret = -EIO;
-			break;
-		case JOURNAL_ENTRY_CLOSED:
-			/*
-			 * Journal entry hasn't been opened yet, but caller
-			 * claims it has something
-			 */
-			BUG();
-		case JOURNAL_ENTRY_INUSE:
-			break;
-		case JOURNAL_UNLOCKED:
-			return 0;
-		}
-	} else if (seq + 1 == journal_cur_seq(j) &&
-		   j->reservations.prev_buf_unwritten) {
-		ret = bch2_journal_error(j);
-	}
+	ret = seq <= j->seq_ondisk ? 1 : journal_seq_error(j, seq);
 
+	if (seq == journal_cur_seq(j))
+		__journal_entry_close(j);
 	spin_unlock(&j->lock);
 
 	return ret;
@@ -612,11 +668,10 @@ int bch2_journal_flush_seq(struct journal *j, u64 seq)
 void bch2_journal_meta_async(struct journal *j, struct closure *parent)
 {
 	struct journal_res res;
-	unsigned u64s = jset_u64s(0);
 
 	memset(&res, 0, sizeof(res));
 
-	bch2_journal_res_get(j, &res, u64s, u64s);
+	bch2_journal_res_get(j, &res, jset_u64s(0), 0);
 	bch2_journal_res_put(j, &res);
 
 	bch2_journal_flush_seq_async(j, res.seq, parent);
@@ -625,12 +680,11 @@ void bch2_journal_meta_async(struct journal *j, struct closure *parent)
 int bch2_journal_meta(struct journal *j)
 {
 	struct journal_res res;
-	unsigned u64s = jset_u64s(0);
 	int ret;
 
 	memset(&res, 0, sizeof(res));
 
-	ret = bch2_journal_res_get(j, &res, u64s, u64s);
+	ret = bch2_journal_res_get(j, &res, jset_u64s(0), 0);
 	if (ret)
 		return ret;
 
@@ -683,6 +737,26 @@ int bch2_journal_flush(struct journal *j)
 	return bch2_journal_flush_seq(j, seq);
 }
 
+/* block/unlock the journal: */
+
+void bch2_journal_unblock(struct journal *j)
+{
+	spin_lock(&j->lock);
+	j->blocked--;
+	spin_unlock(&j->lock);
+
+	journal_wake(j);
+}
+
+void bch2_journal_block(struct journal *j)
+{
+	spin_lock(&j->lock);
+	j->blocked++;
+	spin_unlock(&j->lock);
+
+	journal_quiesce(j);
+}
+
 /* allocate journal on a device: */
 
 static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
@@ -705,10 +779,14 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 		goto err;
 
 	journal_buckets = bch2_sb_resize_journal(&ca->disk_sb,
-				nr + sizeof(*journal_buckets) / sizeof(u64));
+						 nr + sizeof(*journal_buckets) / sizeof(u64));
 	if (!journal_buckets)
 		goto err;
 
+	/*
+	 * We may be called from the device add path, before the new device has
+	 * actually been added to the running filesystem:
+	 */
 	if (c)
 		spin_lock(&c->journal.lock);
 
@@ -722,58 +800,58 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 
 	while (ja->nr < nr) {
 		struct open_bucket *ob = NULL;
+		unsigned pos;
 		long bucket;
 
 		if (new_fs) {
-			percpu_down_read_preempt_disable(&c->usage_lock);
 			bucket = bch2_bucket_alloc_new_fs(ca);
-			percpu_up_read_preempt_enable(&c->usage_lock);
-
 			if (bucket < 0) {
 				ret = -ENOSPC;
 				goto err;
 			}
 		} else {
-			int ob_idx = bch2_bucket_alloc(c, ca, RESERVE_ALLOC, false, cl);
-			if (ob_idx < 0) {
+			ob = bch2_bucket_alloc(c, ca, RESERVE_ALLOC,
+					       false, cl);
+			if (IS_ERR(ob)) {
 				ret = cl ? -EAGAIN : -ENOSPC;
 				goto err;
 			}
 
-			ob = c->open_buckets + ob_idx;
 			bucket = sector_to_bucket(ca, ob->ptr.offset);
 		}
 
 		if (c) {
-			percpu_down_read_preempt_disable(&c->usage_lock);
+			percpu_down_read(&c->mark_lock);
 			spin_lock(&c->journal.lock);
 		}
 
-		__array_insert_item(ja->buckets,		ja->nr, ja->last_idx);
-		__array_insert_item(ja->bucket_seq,		ja->nr, ja->last_idx);
-		__array_insert_item(journal_buckets->buckets,	ja->nr, ja->last_idx);
+		pos = ja->nr ? (ja->cur_idx + 1) % ja->nr : 0;
+		__array_insert_item(ja->buckets,		ja->nr, pos);
+		__array_insert_item(ja->bucket_seq,		ja->nr, pos);
+		__array_insert_item(journal_buckets->buckets,	ja->nr, pos);
+		ja->nr++;
 
-		ja->buckets[ja->last_idx] = bucket;
-		ja->bucket_seq[ja->last_idx] = 0;
-		journal_buckets->buckets[ja->last_idx] = cpu_to_le64(bucket);
+		ja->buckets[pos] = bucket;
+		ja->bucket_seq[pos] = 0;
+		journal_buckets->buckets[pos] = cpu_to_le64(bucket);
 
-		if (ja->last_idx < ja->nr) {
-			if (ja->cur_idx >= ja->last_idx)
-				ja->cur_idx++;
-			ja->last_idx++;
-		}
-		ja->nr++;
+		if (pos <= ja->discard_idx)
+			ja->discard_idx = (ja->discard_idx + 1) % ja->nr;
+		if (pos <= ja->dirty_idx_ondisk)
+			ja->dirty_idx_ondisk = (ja->dirty_idx_ondisk + 1) % ja->nr;
+		if (pos <= ja->dirty_idx)
+			ja->dirty_idx = (ja->dirty_idx + 1) % ja->nr;
+		if (pos <= ja->cur_idx)
+			ja->cur_idx = (ja->cur_idx + 1) % ja->nr;
 
 		bch2_mark_metadata_bucket(c, ca, bucket, BCH_DATA_JOURNAL,
-				ca->mi.bucket_size,
-				gc_phase(GC_PHASE_SB),
-				new_fs
-				? BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE
-				: 0);
+					  ca->mi.bucket_size,
+					  gc_phase(GC_PHASE_SB),
+					  0);
 
 		if (c) {
 			spin_unlock(&c->journal.lock);
-			percpu_up_read_preempt_enable(&c->usage_lock);
+			percpu_up_read(&c->mark_lock);
 		}
 
 		if (!new_fs)
@@ -818,7 +896,7 @@ int bch2_set_nr_journal_buckets(struct bch_fs *c, struct bch_dev *ca,
 		 */
 
 		if (bch2_disk_reservation_get(c, &disk_res,
-				bucket_to_sector(ca, nr - ja->nr), 1, 0)) {
+					      bucket_to_sector(ca, nr - ja->nr), 1, 0)) {
 			mutex_unlock(&c->sb_lock);
 			return -ENOSPC;
 		}
@@ -875,54 +953,90 @@ static bool bch2_journal_writing_to_device(struct journal *j, unsigned dev_idx)
 
 void bch2_dev_journal_stop(struct journal *j, struct bch_dev *ca)
 {
-	spin_lock(&j->lock);
-	bch2_extent_drop_device(bkey_i_to_s_extent(&j->key), ca->dev_idx);
-	spin_unlock(&j->lock);
-
 	wait_event(j->wait, !bch2_journal_writing_to_device(j, ca->dev_idx));
 }
 
 void bch2_fs_journal_stop(struct journal *j)
 {
-	wait_event(j->wait, journal_flush_write(j));
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+
+	bch2_journal_flush_all_pins(j);
+
+	wait_event(j->wait, journal_entry_close(j));
+
+	/* do we need to write another journal entry? */
+	if (test_bit(JOURNAL_NOT_EMPTY, &j->flags) ||
+	    c->btree_roots_dirty)
+		bch2_journal_meta(j);
+
+	journal_quiesce(j);
+
+	BUG_ON(!bch2_journal_error(j) &&
+	       test_bit(JOURNAL_NOT_EMPTY, &j->flags));
 
 	cancel_delayed_work_sync(&j->write_work);
 	cancel_delayed_work_sync(&j->reclaim_work);
 }
 
-void bch2_fs_journal_start(struct journal *j)
+int bch2_fs_journal_start(struct journal *j, u64 cur_seq,
+			  struct list_head *journal_entries)
 {
-	struct journal_seq_blacklist *bl;
-	u64 blacklist = 0;
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct journal_entry_pin_list *p;
+	struct journal_replay *i;
+	u64 last_seq = cur_seq, nr, seq;
+
+	if (!list_empty(journal_entries))
+		last_seq = le64_to_cpu(list_first_entry(journal_entries,
+							struct journal_replay,
+							list)->j.seq);
+
+	nr = cur_seq - last_seq;
+
+	if (nr + 1 > j->pin.size) {
+		free_fifo(&j->pin);
+		init_fifo(&j->pin, roundup_pow_of_two(nr + 1), GFP_KERNEL);
+		if (!j->pin.data) {
+			bch_err(c, "error reallocating journal fifo (%llu open entries)", nr);
+			return -ENOMEM;
+		}
+	}
+
+	j->replay_journal_seq	= last_seq;
+	j->replay_journal_seq_end = cur_seq;
+	j->last_seq_ondisk	= last_seq;
+	j->pin.front		= last_seq;
+	j->pin.back		= cur_seq;
+	atomic64_set(&j->seq, cur_seq - 1);
+
+	fifo_for_each_entry_ptr(p, &j->pin, seq) {
+		INIT_LIST_HEAD(&p->list);
+		INIT_LIST_HEAD(&p->flushed);
+		atomic_set(&p->count, 1);
+		p->devs.nr = 0;
+	}
+
+	list_for_each_entry(i, journal_entries, list) {
+		seq = le64_to_cpu(i->j.seq);
 
-	list_for_each_entry(bl, &j->seq_blacklist, list)
-		blacklist = max(blacklist, bl->end);
+		BUG_ON(seq < last_seq || seq >= cur_seq);
+
+		journal_seq_pin(j, seq)->devs = i->devs;
+	}
 
 	spin_lock(&j->lock);
 
 	set_bit(JOURNAL_STARTED, &j->flags);
 
-	while (journal_cur_seq(j) < blacklist)
-		journal_pin_new_entry(j, 0);
-
-	/*
-	 * journal_buf_switch() only inits the next journal entry when it
-	 * closes an open journal entry - the very first journal entry gets
-	 * initialized here:
-	 */
 	journal_pin_new_entry(j, 1);
 	bch2_journal_buf_init(j);
 
-	spin_unlock(&j->lock);
+	c->last_bucket_seq_cleanup = journal_cur_seq(j);
 
-	/*
-	 * Adding entries to the next journal entry before allocating space on
-	 * disk for the next journal entry - this is ok, because these entries
-	 * only have to go down with the next journal entry we write:
-	 */
-	bch2_journal_seq_blacklist_write(j);
+	bch2_journal_space_available(j);
+	spin_unlock(&j->lock);
 
-	queue_delayed_work(system_freezable_wq, &j->reclaim_work, 0);
+	return 0;
 }
 
 /* init/exit: */
@@ -968,8 +1082,8 @@ int bch2_dev_journal_init(struct bch_dev *ca, struct bch_sb *sb)
 
 void bch2_fs_journal_exit(struct journal *j)
 {
-	kvpfree(j->buf[1].data, j->buf[1].size);
-	kvpfree(j->buf[0].data, j->buf[0].size);
+	kvpfree(j->buf[1].data, j->buf[1].buf_size);
+	kvpfree(j->buf[0].data, j->buf[0].buf_size);
 	free_fifo(&j->pin);
 }
 
@@ -986,26 +1100,28 @@ int bch2_fs_journal_init(struct journal *j)
 	init_waitqueue_head(&j->wait);
 	INIT_DELAYED_WORK(&j->write_work, journal_write_work);
 	INIT_DELAYED_WORK(&j->reclaim_work, bch2_journal_reclaim_work);
-	mutex_init(&j->blacklist_lock);
-	INIT_LIST_HEAD(&j->seq_blacklist);
+	init_waitqueue_head(&j->pin_flush_wait);
 	mutex_init(&j->reclaim_lock);
+	mutex_init(&j->discard_lock);
 
 	lockdep_init_map(&j->res_map, "journal res", &res_key, 0);
 
-	j->buf[0].size		= JOURNAL_ENTRY_SIZE_MIN;
-	j->buf[1].size		= JOURNAL_ENTRY_SIZE_MIN;
+	j->buf[0].buf_size	= JOURNAL_ENTRY_SIZE_MIN;
+	j->buf[1].buf_size	= JOURNAL_ENTRY_SIZE_MIN;
 	j->write_delay_ms	= 1000;
 	j->reclaim_delay_ms	= 100;
 
-	bkey_extent_init(&j->key);
+	/* Btree roots: */
+	j->entry_u64s_reserved +=
+		BTREE_ID_NR * (JSET_KEYS_U64s + BKEY_EXTENT_U64s_MAX);
 
 	atomic64_set(&j->reservations.counter,
 		((union journal_res_state)
 		 { .cur_entry_offset = JOURNAL_ENTRY_CLOSED_VAL }).v);
 
 	if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
-	    !(j->buf[0].data = kvpmalloc(j->buf[0].size, GFP_KERNEL)) ||
-	    !(j->buf[1].data = kvpmalloc(j->buf[1].size, GFP_KERNEL))) {
+	    !(j->buf[0].data = kvpmalloc(j->buf[0].buf_size, GFP_KERNEL)) ||
+	    !(j->buf[1].data = kvpmalloc(j->buf[1].buf_size, GFP_KERNEL))) {
 		ret = -ENOMEM;
 		goto out;
 	}
@@ -1020,38 +1136,63 @@ out:
 
 ssize_t bch2_journal_print_debug(struct journal *j, char *buf)
 {
+	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
-	union journal_res_state *s = &j->reservations;
+	union journal_res_state s;
 	struct bch_dev *ca;
 	unsigned iter;
-	ssize_t ret = 0;
 
 	rcu_read_lock();
 	spin_lock(&j->lock);
+	s = READ_ONCE(j->reservations);
+
+	pr_buf(&out,
+	       "active journal entries:\t%llu\n"
+	       "seq:\t\t\t%llu\n"
+	       "last_seq:\t\t%llu\n"
+	       "last_seq_ondisk:\t%llu\n"
+	       "prereserved:\t\t%u/%u\n"
+	       "current entry sectors:\t%u\n"
+	       "current entry:\t\t",
+	       fifo_used(&j->pin),
+	       journal_cur_seq(j),
+	       journal_last_seq(j),
+	       j->last_seq_ondisk,
+	       j->prereserved.reserved,
+	       j->prereserved.remaining,
+	       j->cur_entry_sectors);
+
+	switch (s.cur_entry_offset) {
+	case JOURNAL_ENTRY_ERROR_VAL:
+		pr_buf(&out, "error\n");
+		break;
+	case JOURNAL_ENTRY_CLOSED_VAL:
+		pr_buf(&out, "closed\n");
+		break;
+	default:
+		pr_buf(&out, "%u/%u\n",
+		       s.cur_entry_offset,
+		       j->cur_entry_u64s);
+		break;
+	}
 
-	ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-			 "active journal entries:\t%llu\n"
-			 "seq:\t\t\t%llu\n"
-			 "last_seq:\t\t%llu\n"
-			 "last_seq_ondisk:\t%llu\n"
-			 "reservation count:\t%u\n"
-			 "reservation offset:\t%u\n"
-			 "current entry u64s:\t%u\n"
-			 "io in flight:\t\t%i\n"
-			 "need write:\t\t%i\n"
-			 "dirty:\t\t\t%i\n"
-			 "replay done:\t\t%i\n",
-			 fifo_used(&j->pin),
-			 journal_cur_seq(j),
-			 journal_last_seq(j),
-			 j->last_seq_ondisk,
-			 journal_state_count(*s, s->idx),
-			 s->cur_entry_offset,
-			 j->cur_entry_u64s,
-			 s->prev_buf_unwritten,
-			 test_bit(JOURNAL_NEED_WRITE,	&j->flags),
-			 journal_entry_is_open(j),
-			 test_bit(JOURNAL_REPLAY_DONE,	&j->flags));
+	pr_buf(&out,
+	       "current entry refs:\t%u\n"
+	       "prev entry unwritten:\t",
+	       journal_state_count(s, s.idx));
+
+	if (s.prev_buf_unwritten)
+		pr_buf(&out, "yes, ref %u sectors %u\n",
+		       journal_state_count(s, !s.idx),
+		       journal_prev_buf(j)->sectors);
+	else
+		pr_buf(&out, "no\n");
+
+	pr_buf(&out,
+	       "need write:\t\t%i\n"
+	       "replay done:\t\t%i\n",
+	       test_bit(JOURNAL_NEED_WRITE,	&j->flags),
+	       test_bit(JOURNAL_REPLAY_DONE,	&j->flags));
 
 	for_each_member_device_rcu(ca, c, iter,
 				   &c->rw_devs[BCH_DATA_JOURNAL]) {
@@ -1060,50 +1201,53 @@ ssize_t bch2_journal_print_debug(struct journal *j, char *buf)
 		if (!ja->nr)
 			continue;
 
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-				 "dev %u:\n"
-				 "\tnr\t\t%u\n"
-				 "\tcur_idx\t\t%u (seq %llu)\n"
-				 "\tlast_idx\t%u (seq %llu)\n",
-				 iter, ja->nr,
-				 ja->cur_idx,	ja->bucket_seq[ja->cur_idx],
-				 ja->last_idx,	ja->bucket_seq[ja->last_idx]);
+		pr_buf(&out,
+		       "dev %u:\n"
+		       "\tnr\t\t%u\n"
+		       "\tavailable\t%u:%u\n"
+		       "\tdiscard_idx\t\t%u\n"
+		       "\tdirty_idx_ondisk\t%u (seq %llu)\n"
+		       "\tdirty_idx\t\t%u (seq %llu)\n"
+		       "\tcur_idx\t\t%u (seq %llu)\n",
+		       iter, ja->nr,
+		       bch2_journal_dev_buckets_available(j, ja, journal_space_discarded),
+		       ja->sectors_free,
+		       ja->discard_idx,
+		       ja->dirty_idx_ondisk,	ja->bucket_seq[ja->dirty_idx_ondisk],
+		       ja->dirty_idx,		ja->bucket_seq[ja->dirty_idx],
+		       ja->cur_idx,		ja->bucket_seq[ja->cur_idx]);
 	}
 
 	spin_unlock(&j->lock);
 	rcu_read_unlock();
 
-	return ret;
+	return out.pos - buf;
 }
 
 ssize_t bch2_journal_print_pins(struct journal *j, char *buf)
 {
+	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 	struct journal_entry_pin_list *pin_list;
 	struct journal_entry_pin *pin;
-	ssize_t ret = 0;
 	u64 i;
 
 	spin_lock(&j->lock);
 	fifo_for_each_entry_ptr(pin_list, &j->pin, i) {
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-				 "%llu: count %u\n",
-				 i, atomic_read(&pin_list->count));
+		pr_buf(&out, "%llu: count %u\n",
+		       i, atomic_read(&pin_list->count));
 
 		list_for_each_entry(pin, &pin_list->list, list)
-			ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-					 "\t%p %pf\n",
-					 pin, pin->flush);
+			pr_buf(&out, "\t%p %pf\n",
+			       pin, pin->flush);
 
 		if (!list_empty(&pin_list->flushed))
-			ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-					 "flushed:\n");
+			pr_buf(&out, "flushed:\n");
 
 		list_for_each_entry(pin, &pin_list->flushed, list)
-			ret += scnprintf(buf + ret, PAGE_SIZE - ret,
-					 "\t%p %pf\n",
-					 pin, pin->flush);
+			pr_buf(&out, "\t%p %pf\n",
+			       pin, pin->flush);
 	}
 	spin_unlock(&j->lock);
 
-	return ret;
+	return out.pos - buf;
 }