bcachefs: Fix a null ptr deref

rbio->c wasn't being initialized in the move path
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/io.c

@@ -1218,10 +1218,15 @@ static inline struct bch_read_bio *bch2_rbio_free(struct bch_read_bio *rbio)
 	return rbio;
 }
 
+/*
+ * Only called on a top level bch_read_bio to complete an entire read request,
+ * not a split:
+ */
 static void bch2_rbio_done(struct bch_read_bio *rbio)
 {
-	bch2_time_stats_update(&rbio->c->times[BCH_TIME_data_read],
-			       rbio->start_time);
+	if (rbio->start_time)
+		bch2_time_stats_update(&rbio->c->times[BCH_TIME_data_read],
+				       rbio->start_time);
 	bio_endio(&rbio->bio);
 }
 

fs/bcachefs/move.c

@@ -436,7 +436,8 @@ static int bch2_move_extent(struct bch_fs *c,
 				 GFP_KERNEL))
 		goto err_free;
 
-	io->rbio.opts = io_opts;
+	io->rbio.c		= c;
+	io->rbio.opts		= io_opts;
 	bio_init(&io->rbio.bio, NULL, io->bi_inline_vecs, pages, 0);
 	io->rbio.bio.bi_vcnt = pages;
 	bio_set_prio(&io->rbio.bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));