From: Stefan Metzmacher <metze@samba.org>
Date: Mon, 27 Aug 2018 11:02:50 +0000 (+0200)
Subject: smb2_server: use sendmsg/recvmsg instead of writev/readv
X-Git-Tag: ldb-2.1.1~157
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=76e1206717e76dadc212f3363d3faeb66b18c7e7;p=thirdparty%2Fsamba.git

smb2_server: use sendmsg/recvmsg instead of writev/readv

This avoids a few function calls inside the kernel
in order to reach sock_sendmsg() quicker:

    entry_SYSCALL_64_after_hwframe
       do_syscall_64
          __x64_sys_writev
             do_writev
                vfs_writev
                   do_iter_write
                      do_iter_readv_writev
                         sock_write_iter
                            sock_sendmsg

    entry_SYSCALL_64_after_hwframe
       do_syscall_64
          __x64_sys_sendmsg
             __sys_sendmsg
                ___sys_sendmsg
                   sock_sendmsg

As a side effect it will be useful for SMB-Direct invalidation
messages via msg->msg_control and CMSG_*.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
---

diff --git a/source3/smbd/smb2_server.c b/source3/smbd/smb2_server.c
index 8c66d74c8de..a4372bf1145 100644
--- a/source3/smbd/smb2_server.c
+++ b/source3/smbd/smb2_server.c
@@ -3758,6 +3758,7 @@ static NTSTATUS smbd_smb2_flush_send_queue(struct smbXsrv_connection *xconn)
 	while (xconn->smb2.send_queue != NULL) {
 		struct smbd_smb2_send_queue *e = xconn->smb2.send_queue;
 		bool ok;
+		struct msghdr msg;
 
 		if (e->sendfile_header != NULL) {
 			size_t size = 0;
@@ -3806,7 +3807,12 @@ static NTSTATUS smbd_smb2_flush_send_queue(struct smbXsrv_connection *xconn)
 			continue;
 		}
 
-		ret = writev(xconn->transport.sock, e->vector, e->count);
+		msg = (struct msghdr) {
+			.msg_iov = e->vector,
+			.msg_iovlen = e->count,
+		};
+
+		ret = sendmsg(xconn->transport.sock, &msg, 0);
 		if (ret == 0) {
 			/* propagate end of file */
 			return NT_STATUS_INTERNAL_ERROR;
@@ -3862,6 +3868,7 @@ static NTSTATUS smbd_smb2_io_handler(struct smbXsrv_connection *xconn,
 	bool retry;
 	NTSTATUS status;
 	NTTIME now;
+	struct msghdr msg;
 
 	if (!NT_STATUS_IS_OK(xconn->transport.status)) {
 		/*
@@ -3896,7 +3903,12 @@ again:
 		state->vector.iov_len = NBT_HDR_SIZE;
 	}
 
-	ret = readv(xconn->transport.sock, &state->vector, 1);
+	msg = (struct msghdr) {
+		.msg_iov = &state->vector,
+		.msg_iovlen = 1,
+	};
+
+	ret = recvmsg(xconn->transport.sock, &msg, 0);
 	if (ret == 0) {
 		/* propagate end of file */
 		return NT_STATUS_END_OF_FILE;