io_uring: fix async buffered reads when readahead is disabled

The async buffered reads feature is not working when readahead is
turned off. There are two things to concern:

- when doing retry in io_read, not only the IOCB_WAITQ flag but also
  the IOCB_NOWAIT flag is still set, which makes it goes to would_block
  phase in generic_file_buffered_read() and then return -EAGAIN. After
  that, the io-wq thread work is queued, and later doing the async
  reads in the old way.

- even if we remove IOCB_NOWAIT when doing retry, the feature is still
  not running properly, since in generic_file_buffered_read() it goes to
  lock_page_killable() after calling mapping->a_ops->readpage() to do
  IO, and thus causing process to sleep.

Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Fixes: 3b2a4439e0ae ("io_uring: get rid of kiocb_wait_page_queue_init()")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 556e4a2ead07..b89cc87830b1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3049,6 +3049,7 @@ static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
 	if (!wake_page_match(wpq, key))
 		return 0;
 
+	req->rw.kiocb.ki_flags &= ~IOCB_WAITQ;
 	list_del_init(&wait->entry);
 
 	init_task_work(&req->task_work, io_req_task_submit);
@@ -3106,6 +3107,7 @@ static bool io_rw_should_retry(struct io_kiocb *req)
 	wait->wait.flags = 0;
 	INIT_LIST_HEAD(&wait->wait.entry);
 	kiocb->ki_flags |= IOCB_WAITQ;
+	kiocb->ki_flags &= ~IOCB_NOWAIT;
 	kiocb->ki_waitq = wait;
 
 	io_get_req_task(req);