lightnvm: pblk: line reference fix in GC

Fixes the GC error case when moving a line back to closed state
while releasing additional references.
Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
Reviewed-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-gc.c

@@ -290,8 +290,11 @@ static void pblk_gc_line_prepare_ws(struct work_struct *work)
 fail_free_ws:
 	kfree(line_ws);
 
+	/* Line goes back to closed state, so we cannot release additional
+	 * reference for line, since we do that only when we want to do
+	 * gc to free line state transition.
+	 */
 	pblk_put_line_back(pblk, line);
-	kref_put(&line->ref, pblk_line_put);
 	atomic_dec(&gc->read_inflight_gc);
 
 	pblk_err(pblk, "failed to GC line %d\n", line->id);