From fd123e372472179657da738e52e87897d0508812 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Wed, 27 Mar 2019 17:22:23 +0100
Subject: [PATCH 084/163] qemu-nbd: Fail earlier for -c/-d on non-linux

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20190327172308.31077-11-jsnow@redhat.com>
Patchwork-id: 85173
O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 10/55] qemu-nbd: Fail earlier for -c/-d on non-linux
Bugzilla: 1691009
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: Eric Blake <eblake@redhat.com>

Connecting to a /dev/nbdN device is a Linux-specific action.
We were already masking -c and -d from 'qemu-nbd --help' on
non-linux.  However, while -d fails with a sensible error
message, it took hunting through a couple of files to prove
that.  What's more, the code for -c doesn't fail until after
it has created a pthread and tried to open a device - possibly
even printing an error message with %m on a non-Linux platform
in spite of the comment that %m is glibc-specific.  Make the
failure happen sooner, then get rid of stubs that are no
longer needed because of the early exits.

While at it: tweak the blank newlines in --help output to be
consistent, whether or not built on Linux.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181215135324.152629-7-eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
(cherry picked from commit 3c1fa35d74aabe9c3ab642d2591b087e53d7a616)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 nbd/client.c | 18 +-----------------
 qemu-nbd.c   | 21 +++++++++++++++++++--
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/nbd/client.c b/nbd/client.c
index e774147..5a03a84 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -1031,23 +1031,7 @@ int nbd_disconnect(int fd)
     return 0;
 }
 
-#else
-int nbd_init(int fd, QIOChannelSocket *ioc, NBDExportInfo *info,
-	     Error **errp)
-{
-    error_setg(errp, "nbd_init is only supported on Linux");
-    return -ENOTSUP;
-}
-
-int nbd_client(int fd)
-{
-    return -ENOTSUP;
-}
-int nbd_disconnect(int fd)
-{
-    return -ENOTSUP;
-}
-#endif
+#endif /* __linux__ */
 
 int nbd_send_request(QIOChannel *ioc, NBDRequest *request)
 {
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 7f078b2..652199c 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -43,6 +43,12 @@
 #include "trace/control.h"
 #include "qemu-version.h"
 
+#ifdef __linux__
+#define HAVE_NBD_DEVICE 1
+#else
+#define HAVE_NBD_DEVICE 0
+#endif
+
 #define SOCKET_PATH                "/var/lock/qemu-nbd-%s"
 #define QEMU_NBD_OPT_CACHE         256
 #define QEMU_NBD_OPT_AIO           257
@@ -98,11 +104,11 @@ static void usage(const char *name)
 "                            specify tracing options\n"
 "  --fork                    fork off the server process and exit the parent\n"
 "                            once the server is running\n"
-#ifdef __linux__
+#if HAVE_NBD_DEVICE
+"\n"
 "Kernel NBD client support:\n"
 "  -c, --connect=DEV         connect FILE to the local NBD device DEV\n"
 "  -d, --disconnect          disconnect the specified device\n"
-"\n"
 #endif
 "\n"
 "Block device options:\n"
@@ -236,6 +242,7 @@ static void termsig_handler(int signum)
 }
 
 
+#if HAVE_NBD_DEVICE
 static void *show_parts(void *arg)
 {
     char *device = arg;
@@ -321,6 +328,7 @@ out:
     kill(getpid(), SIGTERM);
     return (void *) EXIT_FAILURE;
 }
+#endif /* HAVE_NBD_DEVICE */
 
 static int nbd_can_accept(void)
 {
@@ -816,6 +824,12 @@ int main(int argc, char **argv)
         }
     }
 
+#if !HAVE_NBD_DEVICE
+    if (disconnect || device) {
+        error_report("Kernel /dev/nbdN support not available");
+        exit(EXIT_FAILURE);
+    }
+#else /* HAVE_NBD_DEVICE */
     if (disconnect) {
         int nbdfd = open(argv[optind], O_RDWR);
         if (nbdfd < 0) {
@@ -831,6 +845,7 @@ int main(int argc, char **argv)
 
         return 0;
     }
+#endif
 
     if ((device && !verbose) || fork_process) {
         int stderr_fd[2];
@@ -1012,6 +1027,7 @@ int main(int argc, char **argv)
     nbd_export_set_description(exp, export_description);
 
     if (device) {
+#if HAVE_NBD_DEVICE
         int ret;
 
         ret = pthread_create(&client_thread, NULL, nbd_client_thread, device);
@@ -1019,6 +1035,7 @@ int main(int argc, char **argv)
             error_report("Failed to create client thread: %s", strerror(ret));
             exit(EXIT_FAILURE);
         }
+#endif
     } else {
         /* Shut up GCC warnings.  */
         memset(&client_thread, 0, sizeof(client_thread));
-- 
1.8.3.1