bcachefs: Don't mark superblocks past end of usable space

bcachefs-tools recently started putting a backup superblock at the end
of the device. This causes a problem if the bucket size doesn't divide
the device size - but we can fix it by just skipping marking that part.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/buckets.c

@@ -635,6 +635,12 @@ void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 	BUG_ON(type != BCH_DATA_sb &&
 	       type != BCH_DATA_journal);
 
+	/*
+	 * Backup superblock might be past the end of our normal usable space:
+	 */
+	if (b >= ca->mi.nbuckets)
+		return;
+
 	preempt_disable();
 
 	if (likely(c)) {
@@ -2088,6 +2094,12 @@ static int __bch2_trans_mark_metadata_bucket(struct btree_trans *trans,
 	};
 	int ret = 0;
 
+	/*
+	 * Backup superblock might be past the end of our normal usable space:
+	 */
+	if (b >= ca->mi.nbuckets)
+		return 0;
+
 	a = bch2_trans_start_alloc_update(trans, &iter, &ptr, &u);
 	if (IS_ERR(a))
 		return PTR_ERR(a);

fs/bcachefs/super.c

@@ -1826,6 +1826,11 @@ int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 		goto err;
 	}
 
+	ret = bch2_trans_mark_dev_sb(c, ca);
+	if (ret) {
+		goto err;
+	}
+
 	mutex_lock(&c->sb_lock);
 	mi = &bch2_sb_get_members(c->disk_sb.sb)->members[ca->dev_idx];
 	mi->nbuckets = cpu_to_le64(nbuckets);