bcachefs: Fix stripe reuse path

It's possible that we reuse a stripe that doesn't have quite the same
configuration as the stripe_head we're allocating from. In that case, we
have to make sure that the new stripe uses the settings from the stripe
we resue, not the stripe head, and make sure the buffer is allocated
correctly.

This fixes the ec_mixed_tiers test.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/ec.c

@@ -213,6 +213,7 @@ static void ec_stripe_buf_exit(struct ec_stripe_buf *buf)
 	}
 }
 
+/* XXX: this is a non-mempoolified memory allocation: */
 static int ec_stripe_buf_init(struct ec_stripe_buf *buf,
 			      unsigned offset, unsigned size)
 {
@@ -241,7 +242,7 @@ static int ec_stripe_buf_init(struct ec_stripe_buf *buf,
 	return 0;
 err:
 	ec_stripe_buf_exit(buf);
-	return -ENOMEM;
+	return -BCH_ERR_ENOMEM_stripe_buf;
 }
 
 /* Checksumming: */
@@ -1099,6 +1100,7 @@ static void ec_stripe_create(struct ec_stripe_new *s)
 	}
 
 	BUG_ON(!s->allocated);
+	BUG_ON(!s->idx);
 
 	ec_generate_ec(&s->new_stripe);
 
@@ -1143,6 +1145,7 @@ static void ec_stripe_create(struct ec_stripe_new *s)
 			}
 		}
 
+	if (s->idx)
 		bch2_stripe_close(c, s);
 
 	ec_stripe_buf_exit(&s->existing_stripe);
@@ -1191,6 +1194,7 @@ void bch2_ec_do_stripe_creates(struct bch_fs *c)
 static void ec_stripe_new_put(struct bch_fs *c, struct ec_stripe_new *s)
 {
 	BUG_ON(atomic_read(&s->pin) <= 0);
+	BUG_ON(!s->err && !s->idx);
 
 	if (atomic_dec_and_test(&s->pin))
 		bch2_ec_do_stripe_creates(c);
@@ -1236,6 +1240,8 @@ void *bch2_writepoint_ec_buf(struct bch_fs *c, struct write_point *wp)
 	if (!ob)
 		return NULL;
 
+	BUG_ON(!ob->ec->new_stripe.data[ob->ec_idx]);
+
 	ca	= bch_dev_bkey_exists(c, ob->dev);
 	offset	= ca->mi.bucket_size - ob->sectors_free;
 
@@ -1436,6 +1442,9 @@ static int new_stripe_alloc_buckets(struct btree_trans *trans, struct ec_stripe_
 	bool have_cache = true;
 	int ret = 0;
 
+	BUG_ON(h->s->new_stripe.key.v.nr_blocks		!= h->s->nr_data + h->s->nr_parity);
+	BUG_ON(h->s->new_stripe.key.v.nr_redundant	!= h->s->nr_parity);
+
 	for_each_set_bit(i, h->s->blocks_gotten, h->s->new_stripe.key.v.nr_blocks) {
 		__clear_bit(h->s->new_stripe.key.v.ptrs[i].dev, devs.d);
 		if (i < h->s->nr_data)
@@ -1546,9 +1555,13 @@ static int __bch2_ec_stripe_head_reuse(struct btree_trans *trans, struct ec_stri
 	s64 idx;
 	int ret;
 
+	/*
+	 * If we can't allocate a new stripe, and there's no stripes with empty
+	 * blocks for us to reuse, that means we have to wait on copygc:
+	 */
 	idx = get_existing_stripe(c, h);
 	if (idx < 0)
-		return -BCH_ERR_ENOSPC_stripe_reuse;
+		return -BCH_ERR_stripe_alloc_blocked;
 
 	ret = get_stripe_key_trans(trans, idx, &h->s->existing_stripe);
 	if (ret) {
@@ -1558,12 +1571,14 @@ static int __bch2_ec_stripe_head_reuse(struct btree_trans *trans, struct ec_stri
 		return ret;
 	}
 
-	if (ec_stripe_buf_init(&h->s->existing_stripe, 0, h->blocksize)) {
-		/*
-		 * this is a problem: we have deleted from the
-		 * stripes heap already
-		 */
-		BUG();
+	BUG_ON(h->s->existing_stripe.key.v.nr_redundant != h->s->nr_parity);
+	h->s->nr_data = h->s->existing_stripe.key.v.nr_blocks -
+		h->s->existing_stripe.key.v.nr_redundant;
+
+	ret = ec_stripe_buf_init(&h->s->existing_stripe, 0, h->blocksize);
+	if (ret) {
+		bch2_stripe_close(c, h->s);
+		return ret;
 	}
 
 	BUG_ON(h->s->existing_stripe.size != h->blocksize);
@@ -1675,9 +1690,6 @@ struct ec_stripe_head *bch2_ec_stripe_head_get(struct btree_trans *trans,
 			bch_err(c, "failed to allocate new stripe");
 			goto err;
 		}
-
-		if (ec_stripe_buf_init(&h->s->new_stripe, 0, h->blocksize))
-			BUG();
 	}
 
 	if (h->s->allocated)
@@ -1690,7 +1702,7 @@ struct ec_stripe_head *bch2_ec_stripe_head_get(struct btree_trans *trans,
 	ret =   new_stripe_alloc_buckets(trans, h, RESERVE_stripe, NULL) ?:
 		__bch2_ec_stripe_head_reserve(trans, h);
 	if (!ret)
-		goto allocated;
+		goto allocate_buf;
 	if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
 	    bch2_err_matches(ret, ENOMEM))
 		goto err;
@@ -1703,8 +1715,6 @@ struct ec_stripe_head *bch2_ec_stripe_head_get(struct btree_trans *trans,
 		ret = __bch2_ec_stripe_head_reuse(trans, h);
 		if (!ret)
 			break;
-		if (ret == -BCH_ERR_ENOSPC_stripe_reuse && cl)
-			ret = -BCH_ERR_stripe_alloc_blocked;
 		if (waiting || !cl || ret != -BCH_ERR_stripe_alloc_blocked)
 			goto err;
 
@@ -1723,10 +1733,16 @@ struct ec_stripe_head *bch2_ec_stripe_head_get(struct btree_trans *trans,
 	ret = new_stripe_alloc_buckets(trans, h, reserve, cl);
 	if (ret)
 		goto err;
-allocated:
+
+allocate_buf:
+	ret = ec_stripe_buf_init(&h->s->new_stripe, 0, h->blocksize);
+	if (ret)
+		goto err;
+
 	h->s->allocated = true;
+allocated:
 	BUG_ON(!h->s->idx);
-
+	BUG_ON(!h->s->new_stripe.data[0]);
 	BUG_ON(trans->restarted);
 	return h;
 err:

fs/bcachefs/errcode.h

@@ -3,11 +3,11 @@
 #define _BCACHEFS_ERRCODE_H
 
 #define BCH_ERRCODES()								\
+	x(ENOMEM,			ENOMEM_stripe_buf)			\
 	x(ENOSPC,			ENOSPC_disk_reservation)		\
 	x(ENOSPC,			ENOSPC_bucket_alloc)			\
 	x(ENOSPC,			ENOSPC_disk_label_add)			\
 	x(ENOSPC,			ENOSPC_stripe_create)			\
-	x(ENOSPC,			ENOSPC_stripe_reuse)			\
 	x(ENOSPC,			ENOSPC_inode_create)			\
 	x(ENOSPC,			ENOSPC_str_hash_create)			\
 	x(ENOSPC,			ENOSPC_snapshot_create)			\