1 files changed, 15 insertions, 11 deletions

diff --git a/fs/bcachefs/btree_node_scan.c b/fs/bcachefs/btree_node_scan.c
index cc7af8fe689e..a3fb07c60e25 100644
--- a/fs/bcachefs/btree_node_scan.c
+++ b/fs/bcachefs/btree_node_scan.c
@@ -168,14 +168,6 @@ static void try_read_btree_node(struct find_btree_nodes *f, struct bch_dev *ca,
 	if (BTREE_NODE_ID(bn) >= BTREE_ID_NR_MAX)
 		return;
 
-	bio_reset(bio, ca->disk_sb.bdev, REQ_OP_READ);
-	bio->bi_iter.bi_sector	= offset;
-	bch2_bio_map(bio, b->data, c->opts.btree_node_size);
-
-	submit_time = local_clock();
-	submit_bio_wait(bio);
-	bch2_account_io_completion(ca, BCH_MEMBER_ERROR_read, submit_time, !bio->bi_status);
-
 	rcu_read_lock();
 	struct found_btree_node n = {
 		.btree_id	= BTREE_NODE_ID(bn),
@@ -192,16 +184,26 @@ static void try_read_btree_node(struct find_btree_nodes *f, struct bch_dev *ca,
 	};
 	rcu_read_unlock();
 
+	bio_reset(bio, ca->disk_sb.bdev, REQ_OP_READ);
+	bio->bi_iter.bi_sector	= offset;
+	bch2_bio_map(bio, b->data, c->opts.btree_node_size);
+
+	submit_time = local_clock();
+	submit_bio_wait(bio);
+	bch2_account_io_completion(ca, BCH_MEMBER_ERROR_read, submit_time, !bio->bi_status);
+
 	found_btree_node_to_key(&b->key, &n);
 
 	CLASS(printbuf, buf)();
 	if (!bch2_btree_node_read_done(c, ca, b, NULL, &buf)) {
+		/* read_done will swap out b->data for another buffer */
+		bn = b->data;
 		/*
 		 * Grab journal_seq here because we want the max journal_seq of
 		 * any bset; read_done sorts down to a single set and picks the
 		 * max journal_seq
 		 */
-		n.journal_seq		= le64_to_cpu(b->data->keys.journal_seq),
+		n.journal_seq		= le64_to_cpu(bn->keys.journal_seq),
 		n.sectors_written	= b->written;
 
 		mutex_lock(&f->lock);
@@ -224,15 +226,17 @@ static int read_btree_nodes_worker(void *p)
 	struct bch_fs *c = container_of(w->f, struct bch_fs, found_btree_nodes);
 	struct bch_dev *ca = w->ca;
 	unsigned long last_print = jiffies;
+	struct btree *b = NULL;
+	struct bio *bio = NULL;
 
-	struct btree *b = __bch2_btree_node_mem_alloc(c);
+	b = __bch2_btree_node_mem_alloc(c);
 	if (!b) {
 		bch_err(c, "read_btree_nodes_worker: error allocating buf");
 		w->f->ret = -ENOMEM;
 		goto err;
 	}
 
-	struct bio *bio = bio_alloc(NULL, buf_pages(b->data, c->opts.btree_node_size), 0, GFP_KERNEL);
+	bio = bio_alloc(NULL, buf_pages(b->data, c->opts.btree_node_size), 0, GFP_KERNEL);
 	if (!bio) {
 		bch_err(c, "read_btree_nodes_worker: error allocating bio");
 		w->f->ret = -ENOMEM;