+/*
+ * Create workqueue for deferred direct IO completions. We allocate the
+ * workqueue when it's first needed. This avoids creating workqueue for
+ * filesystems that don't need it and also allows us to create the workqueue
+ * late enough so the we can include s_id in the name of the workqueue.
+ */
+static int sb_init_dio_done_wq(struct super_block *sb)
+{
+ struct workqueue_struct *wq = alloc_workqueue("dio/%s",
+ WQ_MEM_RECLAIM, 0,
+ sb->s_id);
+ if (!wq)
+ return -ENOMEM;
+ /*
+ * This has to be atomic as more DIOs can race to create the workqueue
+ */
+ cmpxchg(&sb->s_dio_done_wq, NULL, wq);
+ /* Someone created workqueue before us? Free ours... */
+ if (wq != sb->s_dio_done_wq)
+ destroy_workqueue(wq);
+ return 0;
+}
+
+static int dio_set_defer_completion(struct dio *dio)
+{
+ struct super_block *sb = dio->inode->i_sb;
+
+ if (dio->defer_completion)
+ return 0;
+ dio->defer_completion = true;
+ if (!sb->s_dio_done_wq)
+ return sb_init_dio_done_wq(sb);
+ return 0;
+}
+