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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 556e4a2..b89cc87 100644 (file)
--- 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);

diff --git a/mm/filemap.c b/mm/filemap.c
index 1aaea26..ea38347 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2267,7 +2267,11 @@ readpage:
                }
 
                if (!PageUptodate(page)) {
-                       error = lock_page_killable(page);
+                       if (iocb->ki_flags & IOCB_WAITQ)
+                               error = lock_page_async(page, iocb->ki_waitq);
+                       else
+                               error = lock_page_killable(page);
+
                        if (unlikely(error))
                                goto readpage_error;
                        if (!PageUptodate(page)) {