[PATCH 5.7 056/163] io_uring: allow O_NONBLOCK async retry

[Greg Kroah-Hartman]

From: Jens Axboe <axboe@xxxxxxxxx>

commit c5b856255cbc3b664d686a83fa9397a835e063de upstream.

We can assume that O_NONBLOCK is always honored, even if we don't
have a ->read/write_iter() for the file type. Also unify the read/write
checking for allowing async punt, having the write side factoring in the
REQ_F_NOWAIT flag as well.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 490e89676a52 ("io_uring: only force async punt if poll based retry can't handle it")
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/io_uring.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2038,6 +2038,10 @@ static bool io_file_supports_async(struc
 	if (S_ISREG(mode) && file->f_op != &io_uring_fops)
 		return true;
 
+	/* any ->read/write should understand O_NONBLOCK */
+	if (file->f_flags & O_NONBLOCK)
+		return true;
+
 	if (!(file->f_mode & FMODE_NOWAIT))
 		return false;
 
@@ -2080,8 +2084,7 @@ static int io_prep_rw(struct io_kiocb *r
 		kiocb->ki_ioprio = get_current_ioprio();
 
 	/* don't allow async punt if RWF_NOWAIT was requested */
-	if ((kiocb->ki_flags & IOCB_NOWAIT) ||
-	    (req->file->f_flags & O_NONBLOCK))
+	if (kiocb->ki_flags & IOCB_NOWAIT)
 		req->flags |= REQ_F_NOWAIT;
 
 	if (force_nonblock)
@@ -2722,7 +2725,8 @@ copy_iov:
 			if (ret)
 				goto out_free;
 			/* any defer here is final, must blocking retry */
-			if (!file_can_poll(req->file))
+			if (!(req->flags & REQ_F_NOWAIT) &&
+			    !file_can_poll(req->file))
 				req->flags |= REQ_F_MUST_PUNT;
 			return -EAGAIN;
 		}