[PATCH 5/5] io_uring: don't use retry based buffered reads for non-async bdev

[Jens Axboe <axboe@kernel.dk>]

Some block devices, like dm, bubble back -EAGAIN through the completion
handler. We cannot easily support the retry based buffered aio for those,
so catch it early and use the old style io-wq based fallback.

Fixes: bcf5a06304d6 ("io_uring: support true async buffered reads, if file provides it")
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 05670a615663..c9be9a607401 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3100,6 +3100,13 @@ static bool io_rw_should_retry(struct io_kiocb *req)
 	if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
 		return false;
 
+	/*
+	 * If we can't do nonblock submit without -EAGAIN direct return,
+	 * then don't use the retry based approach.
+	 */
+	if (!io_file_supports_async(req->file, READ))
+		return false;
+
 	wait->wait.func = io_async_buf_func;
 	wait->wait.private = req;
 	wait->wait.flags = 0;
-- 
2.28.0