From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 15 Aug 2020 22:58:42 +0000 (-0700)
Subject: io_uring: short circuit -EAGAIN for blocking read attempt
X-Git-Tag: baikal/mips/sdk5.9~12872^2
X-Git-Url: https://git.baikalelectronics.ru/?a=commitdiff_plain;h=4cc4dc3a713bffc7bae5497b542d497793b666e6;p=kernel.git

io_uring: short circuit -EAGAIN for blocking read attempt

One case was missed in the short IO retry handling, and that's hitting
-EAGAIN on a blocking attempt read (eg from io-wq context). This is a
problem on sockets that are marked as non-blocking when created, they
don't carry any REQ_F_NOWAIT information to help us terminate them
instead of perpetually retrying.

Fixes: bae9fda2441a ("io_uring: internally retry short reads")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cb030912bf5e3..dc506b75659c5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3186,6 +3186,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 		ret = 0;
 		goto out_free;
 	} else if (ret == -EAGAIN) {
+		if (!force_nonblock)
+			goto done;
 		ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
 		if (ret)
 			goto out_free;
@@ -3195,7 +3197,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 	}
 
 	/* read it all, or we did blocking attempt. no retry. */
-	if (!iov_iter_count(iter) || !force_nonblock)
+	if (!iov_iter_count(iter) || !force_nonblock ||
+	    (req->file->f_flags & O_NONBLOCK))
 		goto done;
 
 	io_size -= ret;