bcachefs: move journal seq assertion

journal_cur_seq() can legitimately be used outside of the journal lock,
where this assert can race
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal.c

@@ -321,6 +321,8 @@ static int journal_entry_open(struct journal *j)
 	atomic64_inc(&j->seq);
 	journal_pin_list_init(fifo_push_ref(&j->pin), 1);
 
+	BUG_ON(j->pin.back - 1 != atomic64_read(&j->seq));
+
 	BUG_ON(j->buf + (journal_cur_seq(j) & JOURNAL_BUF_MASK) != buf);
 
 	bkey_extent_init(&buf->key);

fs/bcachefs/journal.h

@@ -136,9 +136,7 @@ static inline u64 journal_last_seq(struct journal *j)
 
 static inline u64 journal_cur_seq(struct journal *j)
 {
-	EBUG_ON(j->pin.back - 1 != atomic64_read(&j->seq));
-
-	return j->pin.back - 1;
+	return atomic64_read(&j->seq);
 }
 
 static inline u64 journal_last_unwritten_seq(struct journal *j)