bcachefs: Kill bch2_bucket_gens_read()

This folds bch2_bucket_gens_read() into bch2_alloc_read(), doing the
version check there.

This is prep work for enumarating all recovery passes: we need some
cleanup first to make calling all the recovery passes consistent.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_background.c

@@ -551,40 +551,6 @@ bch2_trans_start_alloc_update(struct btree_trans *trans, struct btree_iter *iter
 	return ERR_PTR(ret);
 }
 
-int bch2_alloc_read(struct bch_fs *c)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	struct bch_alloc_v4 a;
-	struct bch_dev *ca;
-	int ret;
-
-	bch2_trans_init(&trans, c, 0, 0);
-
-	for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
-			   BTREE_ITER_PREFETCH, k, ret) {
-		/*
-		 * Not a fsck error because this is checked/repaired by
-		 * bch2_check_alloc_key() which runs later:
-		 */
-		if (!bch2_dev_bucket_exists(c, k.k->p))
-			continue;
-
-		ca = bch_dev_bkey_exists(c, k.k->p.inode);
-
-		*bucket_gen(ca, k.k->p.offset) = bch2_alloc_to_v4(k, &a)->gen;
-	}
-	bch2_trans_iter_exit(&trans, &iter);
-
-	bch2_trans_exit(&trans);
-
-	if (ret)
-		bch_err_fn(c, ret);
-
-	return ret;
-}
-
 static struct bpos alloc_gens_pos(struct bpos pos, unsigned *offset)
 {
 	*offset = pos.offset & KEY_TYPE_BUCKET_GENS_MASK;
@@ -692,18 +658,21 @@ int bch2_bucket_gens_init(struct bch_fs *c)
 	return ret;
 }
 
-int bch2_bucket_gens_read(struct bch_fs *c)
+int bch2_alloc_read(struct bch_fs *c)
 {
 	struct btree_trans trans;
 	struct btree_iter iter;
 	struct bkey_s_c k;
-	const struct bch_bucket_gens *g;
 	struct bch_dev *ca;
-	u64 b;
 	int ret;
 
+	down_read(&c->gc_lock);
 	bch2_trans_init(&trans, c, 0, 0);
 
+	if (c->sb.version_upgrade_complete >= bcachefs_metadata_version_bucket_gens) {
+		const struct bch_bucket_gens *g;
+		u64 b;
+
 		for_each_btree_key(&trans, iter, BTREE_ID_bucket_gens, POS_MIN,
 				   BTREE_ITER_PREFETCH, k, ret) {
 			u64 start = bucket_gens_pos_to_alloc(k.k->p, 0).offset;
@@ -729,8 +698,27 @@ int bch2_bucket_gens_read(struct bch_fs *c)
 				*bucket_gen(ca, b) = g->gens[b & KEY_TYPE_BUCKET_GENS_MASK];
 		}
 		bch2_trans_iter_exit(&trans, &iter);
+	} else {
+		struct bch_alloc_v4 a;
+
+		for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
+				   BTREE_ITER_PREFETCH, k, ret) {
+			/*
+			 * Not a fsck error because this is checked/repaired by
+			 * bch2_check_alloc_key() which runs later:
+			 */
+			if (!bch2_dev_bucket_exists(c, k.k->p))
+				continue;
+
+			ca = bch_dev_bkey_exists(c, k.k->p.inode);
+
+			*bucket_gen(ca, k.k->p.offset) = bch2_alloc_to_v4(k, &a)->gen;
+		}
+		bch2_trans_iter_exit(&trans, &iter);
+	}
 
 	bch2_trans_exit(&trans);
+	up_read(&c->gc_lock);
 
 	if (ret)
 		bch_err_fn(c, ret);

fs/bcachefs/alloc_background.h

@@ -212,7 +212,6 @@ static inline bool bkey_is_alloc(const struct bkey *k)
 }
 
 int bch2_alloc_read(struct bch_fs *);
-int bch2_bucket_gens_read(struct bch_fs *);
 
 int bch2_trans_mark_alloc(struct btree_trans *, enum btree_id, unsigned,
 			  struct bkey_s_c, struct bkey_i *, unsigned);

fs/bcachefs/recovery.c

@@ -1309,11 +1309,7 @@ int bch2_fs_recovery(struct bch_fs *c)
 		goto err;
 
 	bch_verbose(c, "starting alloc read");
-	down_read(&c->gc_lock);
-	ret = c->sb.version < bcachefs_metadata_version_bucket_gens
-		? bch2_alloc_read(c)
-		: bch2_bucket_gens_read(c);
-	up_read(&c->gc_lock);
+	ret = bch2_alloc_read(c);
 	if (ret)
 		goto err;
 	bch_verbose(c, "alloc read done");