[PATCH] io_uring: no read-retry on -EAGAIN error and O_NONBLOCK marked file

[Jens Axboe <axboe@kernel.dk>]

    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@vger.kernel.org
    Reported-by: Norman Maurer <norman.maurer@googlemail.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b1ccd7072d93..65656102bbeb 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2300,8 +2300,11 @@ static bool io_resubmit_prep(struct io_kiocb *req, int error)
 static bool io_rw_reissue(struct io_kiocb *req, long res)
 {
 #ifdef CONFIG_BLOCK
+	umode_t mode = file_inode(req->file)->i_mode;
 	int ret;
 
+	if (!S_ISBLK(mode) && !S_ISREG(mode))
+		return false;
 	if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
 		return false;
 
@@ -3146,6 +3149,9 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 		/* IOPOLL retry should happen for io-wq threads */
 		if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
 			goto done;
+		/* no retry on NONBLOCK marked file */
+		if (req->file->f_flags & O_NONBLOCK)
+			goto done;
 		/* some cases will consume bytes even on error returns */
 		iov_iter_revert(iter, iov_count - iov_iter_count(iter));
 		ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
@@ -3291,8 +3297,12 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
 		/* IOPOLL retry should happen for io-wq threads */
 		if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)
 			goto copy_iov;
+done:
 		kiocb_done(kiocb, ret2, cs);
 	} else {
+		/* no retry on NONBLOCK marked file */
+		if (req->file->f_flags & O_NONBLOCK)
+			goto done;
 copy_iov:
 		/* some cases will consume bytes even on error returns */
 		iov_iter_revert(iter, iov_count - iov_iter_count(iter));

-- 
Jens Axboe