blk-mq: bitmap tag: fix races in bt_get() function

[linux-block.git] / block / blk-mq-tag.c

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 08fc6716d362ecbda142ffeb845f53822816a41d..c1b92426c95e28139134e51a68de2f724f8979f5 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -248,18 +248,12 @@ static int bt_get(struct blk_mq_alloc_data *data,
 
        bs = bt_wait_ptr(bt, hctx);
        do {
-               bool was_empty;
-
-               was_empty = list_empty(&wait.task_list);
                prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
 
                tag = __bt_get(hctx, bt, last_tag);
                if (tag != -1)
                        break;
 
-               if (was_empty)
-                       atomic_set(&bs->wait_cnt, bt->wake_cnt);
-
                blk_mq_put_ctx(data->ctx);
 
                io_schedule();
@@ -519,10 +513,13 @@ static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
                return -ENOMEM;
        }
 
-       for (i = 0; i < BT_WAIT_QUEUES; i++)
+       bt_update_count(bt, depth);
+
+       for (i = 0; i < BT_WAIT_QUEUES; i++) {
                init_waitqueue_head(&bt->bs[i].wait);
+               atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt);
+       }
 
-       bt_update_count(bt, depth);
        return 0;
 }