bcachefs: Assorted journal refactoring

Improved the way we track various state by adding j->err_seq, which
records the first journal sequence number that encountered an error
being written, and j->last_empty_seq, which records the most recent
journal entry that was completely empty.

Also, use the low bits of the journal sequence number to index the
corresponding journal_buf.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal.c

@@ -17,7 +17,19 @@
 #include "super-io.h"
 #include "trace.h"
 
-static inline struct journal_buf *journal_seq_to_buf(struct journal *, u64);
+static u64 last_unwritten_seq(struct journal *j)
+{
+	union journal_res_state s = READ_ONCE(j->reservations);
+
+	lockdep_assert_held(&j->lock);
+
+	return journal_cur_seq(j) - s.prev_buf_unwritten;
+}
+
+static inline bool journal_seq_unwritten(struct journal *j, u64 seq)
+{
+	return seq >= last_unwritten_seq(j);
+}
 
 static bool __journal_entry_is_open(union journal_res_state state)
 {
@@ -29,6 +41,22 @@ static bool journal_entry_is_open(struct journal *j)
 	return __journal_entry_is_open(j->reservations);
 }
 
+static inline struct journal_buf *
+journal_seq_to_buf(struct journal *j, u64 seq)
+{
+	struct journal_buf *buf = NULL;
+
+	EBUG_ON(seq > journal_cur_seq(j));
+	EBUG_ON(seq == journal_cur_seq(j) &&
+		j->reservations.cur_entry_offset == JOURNAL_ENTRY_CLOSED_VAL);
+
+	if (journal_seq_unwritten(j, seq)) {
+		buf = j->buf + (seq & 1);
+		EBUG_ON(le64_to_cpu(buf->data->seq) != seq);
+	}
+	return buf;
+}
+
 static void journal_pin_new_entry(struct journal *j, int count)
 {
 	struct journal_entry_pin_list *p;
@@ -50,6 +78,8 @@ static void bch2_journal_buf_init(struct journal *j)
 {
 	struct journal_buf *buf = journal_cur_buf(j);
 
+	bkey_extent_init(&buf->key);
+
 	memset(buf->has_inode, 0, sizeof(buf->has_inode));
 
 	memset(buf->data, 0, sizeof(*buf->data));
@@ -71,6 +101,7 @@ void bch2_journal_halt(struct journal *j)
 	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
 				       old.v, new.v)) != old.v);
 
+	j->err_seq = journal_cur_seq(j);
 	journal_wake(j);
 	closure_wake_up(&journal_cur_buf(j)->wait);
 }
@@ -138,8 +169,6 @@ static bool __journal_entry_close(struct journal *j)
 	BUG_ON(sectors > buf->sectors);
 	buf->sectors = sectors;
 
-	bkey_extent_init(&buf->key);
-
 	/*
 	 * We have to set last_seq here, _before_ opening a new journal entry:
 	 *
@@ -161,11 +190,6 @@ static bool __journal_entry_close(struct journal *j)
 	 */
 	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);
@@ -502,49 +526,28 @@ void bch2_journal_entry_res_resize(struct journal *j,
 
 /* journal flushing: */
 
-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_flush_seq_async - wait for a journal entry to be written
  *
  * 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,
+int bch2_journal_flush_seq_async(struct journal *j, u64 seq,
 				  struct closure *parent)
 {
 	struct journal_buf *buf;
+	int ret = 0;
 
 	spin_lock(&j->lock);
+	if (seq <= j->err_seq) {
+		ret = -EIO;
+		goto out;
+	}
+
+	if (seq <= j->seq_ondisk) {
+		ret = 1;
+		goto out;
+	}
 
 	if (parent &&
 	    (buf = journal_seq_to_buf(j, seq)))
@@ -553,20 +556,8 @@ void bch2_journal_flush_seq_async(struct journal *j, u64 seq,
 
 	if (seq == journal_cur_seq(j))
 		__journal_entry_close(j);
+out:
 	spin_unlock(&j->lock);
-}
-
-static int journal_seq_flushed(struct journal *j, u64 seq)
-{
-	int ret;
-
-	spin_lock(&j->lock);
-	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;
 }
 
@@ -575,7 +566,7 @@ int bch2_journal_flush_seq(struct journal *j, u64 seq)
 	u64 start_time = local_clock();
 	int ret, ret2;
 
-	ret = wait_event_killable(j->wait, (ret2 = journal_seq_flushed(j, seq)));
+	ret = wait_event_killable(j->wait, (ret2 = bch2_journal_flush_seq_async(j, seq, NULL)));
 
 	bch2_time_stats_update(j->flush_seq_time, start_time);
 
@@ -876,7 +867,8 @@ void bch2_fs_journal_stop(struct journal *j)
 	journal_quiesce(j);
 
 	BUG_ON(!bch2_journal_error(j) &&
-	       test_bit(JOURNAL_NOT_EMPTY, &j->flags));
+	       (journal_entry_is_open(j) ||
+		j->last_empty_seq + 1 != journal_cur_seq(j)));
 
 	cancel_delayed_work_sync(&j->write_work);
 	cancel_delayed_work_sync(&j->reclaim_work);
@@ -934,6 +926,9 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq,
 	set_bit(JOURNAL_STARTED, &j->flags);
 
 	journal_pin_new_entry(j, 1);
+
+	j->reservations.idx = journal_cur_seq(j);
+
 	bch2_journal_buf_init(j);
 
 	c->last_bucket_seq_cleanup = journal_cur_seq(j);

fs/bcachefs/journal.h

@@ -466,7 +466,7 @@ void bch2_journal_entry_res_resize(struct journal *,
 				   struct journal_entry_res *,
 				   unsigned);
 
-void bch2_journal_flush_seq_async(struct journal *, u64, struct closure *);
+int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *);
 void bch2_journal_flush_async(struct journal *, struct closure *);
 
 int bch2_journal_flush_seq(struct journal *, u64);

fs/bcachefs/journal_io.c

@@ -944,24 +944,29 @@ static void journal_write_done(struct closure *cl)
 	struct bch_replicas_padded replicas;
 	u64 seq = le64_to_cpu(w->data->seq);
 	u64 last_seq = le64_to_cpu(w->data->last_seq);
+	int err = 0;
 
 	bch2_time_stats_update(j->write_time, j->write_start_time);
 
 	if (!devs.nr) {
 		bch_err(c, "unable to write journal to sufficient devices");
-		goto err;
+		err = -EIO;
+	} else {
+		bch2_devlist_to_replicas(&replicas.e, BCH_DATA_journal, devs);
+		if (bch2_mark_replicas(c, &replicas.e))
+			err = -EIO;
 	}
 
-	bch2_devlist_to_replicas(&replicas.e, BCH_DATA_journal, devs);
-
-	if (bch2_mark_replicas(c, &replicas.e))
-		goto err;
+	if (err)
+		bch2_fatal_error(c);
 
 	spin_lock(&j->lock);
 	if (seq >= j->pin.front)
 		journal_seq_pin(j, seq)->devs = devs;
 
 	j->seq_ondisk		= seq;
+	if (err && (!j->err_seq || seq < j->err_seq))
+		j->err_seq	= seq;
 	j->last_seq_ondisk	= last_seq;
 	bch2_journal_space_available(j);
 
@@ -973,7 +978,7 @@ static void journal_write_done(struct closure *cl)
 	 * bch2_fs_journal_stop():
 	 */
 	mod_delayed_work(c->journal_reclaim_wq, &j->reclaim_work, 0);
-out:
+
 	/* also must come before signalling write completion: */
 	closure_debug_destroy(cl);
 
@@ -987,11 +992,6 @@ static void journal_write_done(struct closure *cl)
 	if (test_bit(JOURNAL_NEED_WRITE, &j->flags))
 		mod_delayed_work(system_freezable_wq, &j->write_work, 0);
 	spin_unlock(&j->lock);
-	return;
-err:
-	bch2_fatal_error(c);
-	spin_lock(&j->lock);
-	goto out;
 }
 
 static void journal_write_endio(struct bio *bio)
@@ -1072,6 +1072,9 @@ void bch2_journal_write(struct closure *cl)
 	SET_JSET_BIG_ENDIAN(jset, CPU_BIG_ENDIAN);
 	SET_JSET_CSUM_TYPE(jset, bch2_meta_checksum_type(c));
 
+	if (journal_entry_empty(jset))
+		j->last_empty_seq = le64_to_cpu(jset->seq);
+
 	if (bch2_csum_type_is_encryption(JSET_CSUM_TYPE(jset)))
 		validate_before_checksum = true;
 

fs/bcachefs/journal_types.h

@@ -127,7 +127,6 @@ enum {
 	JOURNAL_STARTED,
 	JOURNAL_RECLAIM_STARTED,
 	JOURNAL_NEED_WRITE,
-	JOURNAL_NOT_EMPTY,
 	JOURNAL_MAY_GET_UNRESERVED,
 };
 
@@ -181,6 +180,8 @@ struct journal {
 	/* seq, last_seq from the most recent journal entry successfully written */
 	u64			seq_ondisk;
 	u64			last_seq_ondisk;
+	u64			err_seq;
+	u64			last_empty_seq;
 
 	/*
 	 * FIFO of journal entries whose btree updates have not yet been