bcachefs: Fix overlapping extent repair

overlapping extent repair was colliding with extent past end of inode
checks - don't update "extent ends at" until we know we have an extent.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fsck.c

@@ -1372,10 +1372,6 @@ static int check_overlapping_extents(struct btree_trans *trans,
 			goto err;
 	}
 
-	ret = extent_ends_at(c, extent_ends, seen, k);
-	if (ret)
-		goto err;
-
 	extent_ends->last_pos = k.k->p;
 err:
 	return ret;
@@ -1505,6 +1501,12 @@ static int check_extent(struct btree_trans *trans, struct btree_iter *iter,
 
 		i->seen_this_pos = true;
 	}
+
+	if (k.k->type != KEY_TYPE_whiteout) {
+		ret = extent_ends_at(c, extent_ends, s, k);
+		if (ret)
+			goto err;
+	}
 out:
 err:
 fsck_err: