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qemu-nbd: Fail earlier for -c/-d on non-linux 

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>
This commit is contained in:
Eric Blake 2018-12-15 07:53:08 -06:00
parent 6c5c035138
commit 3c1fa35d74
2 changed files with 20 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
nbd/client.c
View File

@ -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)
{

21
qemu-nbd.c
View File

@ -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)
{
@ -814,6 +822,12 @@ 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) {
@ -829,6 +843,7 @@ int main(int argc, char **argv)
return 0;
}
#endif
if ((device && !verbose) || fork_process) {
int stderr_fd[2];
@ -1006,6 +1021,7 @@ 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);
@ -1013,6 +1029,7 @@ 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));