bcachefs: Don't start allocator threads too early

If the allocator threads start before journal replay has finished
replaying alloc keys, journal replay might overwrite the allocator's
btree updates.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/alloc_background.c

@@ -900,7 +900,8 @@ static void discard_one_bucket(struct bch_fs *c, struct bch_dev *ca, u64 b)
 static bool allocator_thread_running(struct bch_dev *ca)
 {
 	unsigned state = ca->mi.state == BCH_MEMBER_STATE_rw &&
-		test_bit(BCH_FS_ALLOCATOR_RUNNING, &ca->fs->flags)
+		test_bit(BCH_FS_ALLOCATOR_RUNNING, &ca->fs->flags) &&
+		test_bit(BCH_FS_ALLOC_REPLAY_DONE, &ca->fs->flags)
 		? ALLOCATOR_running
 		: ALLOCATOR_stopped;
 	alloc_thread_set_state(ca, state);

fs/bcachefs/bcachefs.h

@@ -509,6 +509,7 @@ enum {
 	BCH_FS_INITIAL_GC_DONE,
 	BCH_FS_INITIAL_GC_UNFIXED,
 	BCH_FS_TOPOLOGY_REPAIR_DONE,
+	BCH_FS_ALLOC_REPLAY_DONE,
 	BCH_FS_BTREE_INTERIOR_REPLAY_DONE,
 	BCH_FS_FSCK_DONE,
 	BCH_FS_STARTED,

fs/bcachefs/recovery.c

@@ -567,9 +567,10 @@ static int bch2_journal_replay(struct bch_fs *c,
 			       struct journal_keys keys)
 {
 	struct journal *j = &c->journal;
+	struct bch_dev *ca;
 	struct journal_key *i;
 	u64 seq;
-	int ret;
+	int ret, idx;
 
 	sort(keys.d, keys.nr, sizeof(keys.d[0]), journal_sort_seq_cmp, NULL);
 
@@ -593,6 +594,11 @@ static int bch2_journal_replay(struct bch_fs *c,
 		}
 	}
 
+	/* Now we can start the allocator threads: */
+	set_bit(BCH_FS_ALLOC_REPLAY_DONE, &c->flags);
+	for_each_member_device(ca, c, idx)
+		bch2_wake_allocator(ca);
+
 	/*
 	 * Next replay updates to interior btree nodes:
 	 */
@@ -1391,6 +1397,7 @@ int bch2_fs_initialize(struct bch_fs *c)
 	for (i = 0; i < BTREE_ID_NR; i++)
 		bch2_btree_root_alloc(c, i);
 
+	set_bit(BCH_FS_ALLOC_REPLAY_DONE, &c->flags);
 	set_bit(BCH_FS_BTREE_INTERIOR_REPLAY_DONE, &c->flags);
 	set_bit(JOURNAL_RECLAIM_STARTED, &c->journal.flags);