bcachefs: Fix allocator + journal interaction

The allocator needs to wait until the last update touching a bucket has
been commited before writing to it again. However, the code was checking
against the last dirty journal sequence number, not the last flushed
journal sequence number.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/alloc_background.c

@@ -594,7 +594,7 @@ static void find_reclaimable_buckets_lru(struct bch_fs *c, struct bch_dev *ca)
 	buckets = bucket_array(ca);
 	ca->alloc_heap.used = 0;
 	now = atomic64_read(&c->io_clock[READ].now);
-	last_seq_ondisk = c->journal.last_seq_ondisk;
+	last_seq_ondisk = c->journal.flushed_seq_ondisk;
 
 	/*
 	 * Find buckets with lowest read priority, by building a maxheap sorted

fs/bcachefs/buckets.c

@@ -50,7 +50,7 @@ static inline void fs_usage_data_type_to_base(struct bch_fs_usage *fs_usage,
 void bch2_bucket_seq_cleanup(struct bch_fs *c)
 {
 	u64 journal_seq = atomic64_read(&c->journal.seq);
-	u16 last_seq_ondisk = c->journal.last_seq_ondisk;
+	u16 last_seq_ondisk = c->journal.flushed_seq_ondisk;
 	struct bch_dev *ca;
 	struct bucket_array *buckets;
 	struct bucket *g;