netdev - [PATCH] net: make socket read/write_iter() honor IOCB

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Date:   Mon, 9 Dec 2019 21:06:30 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Networking <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH] net: make socket read/write_iter() honor IOCB_NOWAIT

The socket read/write helpers only look at the file O_NONBLOCK. not
the iocb IOCB_NOWAIT flag. This breaks users like preadv2/pwritev2
and io_uring that rely on not having the file itself marked nonblocking,
but rather the iocb itself.

Signed-off-by: Jens Axboe <axboe@...nel.dk>

---

This seems like a gross oversight? Verified that it's broken, and
verified that it works for me with this check added.

diff --git a/net/socket.c b/net/socket.c
index b343db1489bd..b116e58d6438 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -957,7 +957,7 @@ static ssize_t sock_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			     .msg_iocb = iocb};
 	ssize_t res;
 
-	if (file->f_flags & O_NONBLOCK)
+	if (file->f_flags & O_NONBLOCK || (iocb->ki_flags & IOCB_NOWAIT))
 		msg.msg_flags = MSG_DONTWAIT;
 
 	if (iocb->ki_pos != 0)
@@ -982,7 +982,7 @@ static ssize_t sock_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_pos != 0)
 		return -ESPIPE;
 
-	if (file->f_flags & O_NONBLOCK)
+	if (file->f_flags & O_NONBLOCK || (iocb->ki_flags & IOCB_NOWAIT))
 		msg.msg_flags = MSG_DONTWAIT;
 
 	if (sock->type == SOCK_SEQPACKET)

-- 
Jens Axboe