From 901341bb9718884f337a92e6c4541227597d1f48 Mon Sep 17 00:00:00 2001 From: Luke Hsiao Date: Fri, 21 Aug 2020 21:41:05 -0700 Subject: [PATCH] io_uring: ignore POLLIN for recvmsg on MSG_ERRQUEUE Currently, io_uring's recvmsg subscribes to both POLLERR and POLLIN. In the context of TCP tx zero-copy, this is inefficient since we are only reading the error queue and not using recvmsg to read POLLIN responses. This patch was tested by using a simple sending program to call recvmsg using io_uring with MSG_ERRQUEUE set and verifying with printks that the POLLIN is correctly unset when the msg flags are MSG_ERRQUEUE. Signed-off-by: Arjun Roy Signed-off-by: Soheil Hassas Yeganeh Acked-by: Eric Dumazet Reviewed-by: Jens Axboe Signed-off-by: Luke Hsiao Signed-off-by: David S. Miller --- fs/io_uring.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/io_uring.c b/fs/io_uring.c index 91e2cc8414f9..1fd03a38400c 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4898,6 +4898,12 @@ static bool io_arm_poll_handler(struct io_kiocb *req) mask |= POLLIN | POLLRDNORM; if (def->pollout) mask |= POLLOUT | POLLWRNORM; + + /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */ + if ((req->opcode == IORING_OP_RECVMSG) && + (req->sr_msg.msg_flags & MSG_ERRQUEUE)) + mask &= ~POLLIN; + mask |= POLLERR | POLLPRI; ipt.pt._qproc = io_async_queue_proc;