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Date: Thu, 21 Dec 2023 04:08:51 +0100
From: 
	Ahelenia =?utf-8?Q?Ziemia=C5=84ska?= <nabijaczleweli@nabijaczleweli.xyz>
Cc: Jens Axboe <axboe@kernel.dk>, Christian Brauner <brauner@kernel.org>, 
	Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, 
	"David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, 
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, 
	Kuniyuki Iwashima <kuniyu@amazon.com>, David Howells <dhowells@redhat.com>, 
	Alexander Mikhalitsyn <alexander@mihalicyn.com>, John Fastabend <john.fastabend@gmail.com>, 
	Daan De Meyer <daan.j.demeyer@gmail.com>, netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 02/11] af_unix: unix_stream_splice_read: always request
 MSG_DONTWAIT
Message-ID: <8309aff7e55f0c7fe973bb2d1e6b6b3a80ac5a99.1703126594.git.nabijaczleweli@nabijaczleweli.xyz>
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Otherwise we risk sleeping with the pipe locked for indeterminate
lengths of time =E2=80=92 given:
	cat > unix.c <<^D
	#define _GNU_SOURCE
	#include <fcntl.h>
	#include <sys/socket.h>
	#include <sys/un.h>
	int main()
	{
		int sp[2];
		socketpair(AF_UNIX, SOCK_STREAM, 0, sp);
		for (;;)
			splice(sp[0], 0, 1, 0, 128 * 1024 * 1024, 0);
	}
	^D
	cc unix.c -o unix
	mkfifo fifo
	./unix > fifo &
	read -r _ < fifo &
	sleep 0.1
	echo zupa > fifo
unix used to sleep in splice and the shell used to enter an
uninterruptible sleep in open("fifo");
now the splice returns -EAGAIN and the whole program completes.

Signed-off-by: Ahelenia Ziemia=C5=84ska <nabijaczleweli@nabijaczleweli.xyz>
---
 net/unix/af_unix.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ac1f2bc18fc9..bae84552bf58 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2921,15 +2921,12 @@ static ssize_t unix_stream_splice_read(struct socke=
t *sock,  loff_t *ppos,
 		.pipe =3D pipe,
 		.size =3D size,
 		.splice_flags =3D flags,
+		.flags =3D MSG_DONTWAIT,
 	};
=20
 	if (unlikely(*ppos))
 		return -ESPIPE;
=20
-	if (sock->file->f_flags & O_NONBLOCK ||
-	    flags & SPLICE_F_NONBLOCK)
-		state.flags =3D MSG_DONTWAIT;
-
 	return unix_stream_read_generic(&state, false);
 }
=20
--=20
2.39.2

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