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Re: [Qemu-block] [PATCH 03/14] qemu-nbd: Fail earlier for -c/-d on non-l
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-block] [PATCH 03/14] qemu-nbd: Fail earlier for -c/-d on non-linux |
Date: |
Fri, 30 Nov 2018 22:23:12 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Nov 30, 2018 at 04:03:32PM -0600, Eric Blake wrote:
> 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 <address@hidden>
> ---
> nbd/client.c | 18 +-----------------
> qemu-nbd.c | 22 ++++++++++++++++++++--
> 2 files changed, 21 insertions(+), 19 deletions(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index b667a1b56fd..0be89f9e641 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -1029,23 +1029,7 @@ 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 e169b839ece..55e29bd9a7e 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)
> {
> @@ -815,6 +823,7 @@ int main(int argc, char **argv)
> }
>
> if (disconnect) {
> +#if HAVE_NBD_DEVICE
> int nbdfd = open(argv[optind], O_RDWR);
> if (nbdfd < 0) {
> error_report("Cannot open %s: %s", argv[optind],
> @@ -828,6 +837,10 @@ int main(int argc, char **argv)
> printf("%s disconnected\n", argv[optind]);
>
> return 0;
> +#else
> + error_report("Kernel /dev/nbdN support not available");
> + exit(EXIT_FAILURE);
> +#endif
> }
>
> if ((device && !verbose) || fork_process) {
> @@ -1006,6 +1019,7 @@ 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 +1027,10 @@ int main(int argc, char **argv)
> error_report("Failed to create client thread: %s",
> strerror(ret));
> exit(EXIT_FAILURE);
> }
> +#else
> + error_report("Kernel /dev/nbdN support not available");
> + exit(EXIT_FAILURE);
> +#endif
> } else {
> /* Shut up GCC warnings. */
> memset(&client_thread, 0, sizeof(client_thread));
Looks like a sensible code refactoring/simplification to me, so:
Reviewed-by: Richard W.M. Jones <address@hidden>
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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- [Qemu-block] [PATCH for-4.0 00/14] nbd: add qemu-nbd --list, Eric Blake, 2018/11/30
- [Qemu-block] [PATCH 03/14] qemu-nbd: Fail earlier for -c/-d on non-linux, Eric Blake, 2018/11/30
- Re: [Qemu-block] [PATCH 03/14] qemu-nbd: Fail earlier for -c/-d on non-linux,
Richard W.M. Jones <=
- [Qemu-block] [PATCH 02/14] nbd/client: More consistent error messages, Eric Blake, 2018/11/30
- [Qemu-block] [PATCH 01/14] qemu-nbd: Use program name in error messages, Eric Blake, 2018/11/30
- [Qemu-block] [PATCH 04/14] qemu-nbd: Simplify --partition handling, Eric Blake, 2018/11/30
- [Qemu-block] [PATCH 07/14] nbd/client: Refactor nbd_negotiate_simple_meta_context(), Eric Blake, 2018/11/30
- [Qemu-block] [PATCH 05/14] nbd/client: Drop pointless buf variable, Eric Blake, 2018/11/30