linux-kernel - [PATCH 5.8 176/186] io_uring: no read/write-retry on -EAGAIN error and O

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Message-Id: <20200908152250.202142288@linuxfoundation.org>
Date:   Tue,  8 Sep 2020 17:25:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Norman Maurer <norman.maurer@...glemail.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 176/186] io_uring: no read/write-retry on -EAGAIN error and O_NONBLOCK marked file

From: Jens Axboe <axboe@...nel.dk>

commit 355afaeb578abac907217c256a844cfafb0337b2 upstream.

Actually two things that need fixing up here:

- The io_rw_reissue() -EAGAIN retry is explicit to block devices and
  regular files, so don't ever attempt to do that on other types of
  files.

- If we hit -EAGAIN on a nonblock marked file, don't arm poll handler for
  it. It should just complete with -EAGAIN.

Cc: stable@...r.kernel.org
Reported-by: Norman Maurer <norman.maurer@...glemail.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io_uring.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2697,8 +2697,15 @@ static int io_read(struct io_kiocb *req,
 		else
 			ret2 = -EINVAL;
 
+		/* no retry on NONBLOCK marked file */
+		if (ret2 == -EAGAIN && (req->file->f_flags & O_NONBLOCK)) {
+			ret = 0;
+			goto done;
+		}
+
 		/* Catch -EAGAIN return for forced non-blocking submission */
 		if (!force_nonblock || ret2 != -EAGAIN) {
+	done:
 			kiocb_done(kiocb, ret2);
 		} else {
 copy_iov:
@@ -2823,7 +2830,13 @@ static int io_write(struct io_kiocb *req
 		 */
 		if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
 			ret2 = -EAGAIN;
+		/* no retry on NONBLOCK marked file */
+		if (ret2 == -EAGAIN && (req->file->f_flags & O_NONBLOCK)) {
+			ret = 0;
+			goto done;
+		}
 		if (!force_nonblock || ret2 != -EAGAIN) {
+done:
 			kiocb_done(kiocb, ret2);
 		} else {
 copy_iov: