Re: [RFC PATCH 01/18] qemu-storage-daemon: Add barebone tool

[Eric Blake]

On 10/17/19 8:01 AM, Kevin Wolf wrote:
> This adds a new binary qemu-storage-daemon that doesn't yet do more than
> some typical initialisation for tools and parsing the basic command
> options --version, --help and --trace.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>   configure             |   2 +-
>   qemu-storage-daemon.c | 141 ++++++++++++++++++++++++++++++++++++++++++
>   Makefile              |   1 +
>   3 files changed, 143 insertions(+), 1 deletion(-)
>   create mode 100644 qemu-storage-daemon.c
>
> diff --git a/configure b/configure

> +++ b/qemu-storage-daemon.c
> @@ -0,0 +1,141 @@
> +/*
> + * QEMU storage daemon
> + *
> + * Copyright (c) 2019 Kevin Wolf <address@hidden>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to 
> deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
> FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.

Is there an intent to license this binary as BSD (by restricting sources 
that can be linked in), or is it going to end up as GPLv2+ for other 
reasons? If the latter, would it be better to license this file GPLv2+?


> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "block/block.h"
> +#include "crypto/init.h"
> +
> +#include "qapi/error.h"
> +#include "qemu-common.h"
> +#include "qemu-version.h"
> +#include "qemu/config-file.h"
> +#include "qemu/error-report.h"
> +#include "qemu/log.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/module.h"
> +
> +#include "trace/control.h"
> +
> +#include <getopt.h>

Shouldn't system headers appear right after qemu/osdep.h?

> +
> +static void help(void)
> +{
> +    printf(
> +"Usage: %s [options]\n"
> +"QEMU storage daemon\n"
> +"\n"
> +"  -h, --help             display this help and exit\n"
> +"  -T, --trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n"
> +"                         specify tracing options\n"
> +"  -V, --version          output version information and exit\n"
> +"\n"
> +QEMU_HELP_BOTTOM "\n",
> +    error_get_progname());
> +}
> +
> +static int process_options(int argc, char *argv[], Error **errp)
> +{
> +    int c;
> +    char *trace_file = NULL;
> +    int ret = -EINVAL;
> +
> +    static const struct option long_options[] = {
> +        {"help", no_argument, 0, 'h'},
> +        {"version", no_argument, 0, 'V'},
> +        {"trace", required_argument, NULL, 'T'},

I find it harder to maintain lists of options (which will get longer 
over time) when the order of the struct...

> +        {0, 0, 0, 0}
> +    };
> +
> +    while ((c = getopt_long(argc, argv, ":hT:V", long_options, NULL)) != -1) {

...the order of the short options...

> +        switch (c) {
> +        case '?':
> +            error_setg(errp, "Unknown option '%s'", argv[optind - 1]);
> +            goto out;
> +        case ':':
> +            error_setg(errp, "Missing option argument for '%s'",
> +                       argv[optind - 1]);
> +            goto out;
> +        case 'h':
> +            help();
> +            exit(EXIT_SUCCESS);
> +        case 'V':
> +            printf("qemu-storage-daemon version "
> +                   QEMU_FULL_VERSION "\n" QEMU_COPYRIGHT "\n");
> +            exit(EXIT_SUCCESS);
> +        case 'T':
> +            g_free(trace_file);
> +            trace_file = trace_opt_parse(optarg);
> +            break;

...and the order of the case statements are not identical. 
Case-insensitive alphabetical may be easiest (matching your shortopt 
ordering of ":hT:V").

> +        }
> +    }
> +    if (optind != argc) {
> +        error_setg(errp, "Unexpected argument: %s", argv[optind]);
> +        goto out;
> +    }
> +
> +    if (!trace_init_backends()) {
> +        error_setg(errp, "Could not initialize trace backends");
> +        goto out;
> +    }
> +    trace_init_file(trace_file);
> +    qemu_set_log(LOG_TRACE);
> +
> +    ret = 0;
> +out:
> +    g_free(trace_file);

Mark trace_file as g_auto, and you can avoid the out: label altogether.

> +    return ret;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +    Error *local_err = NULL;
> +    int ret;
> +
> +#ifdef CONFIG_POSIX
> +    signal(SIGPIPE, SIG_IGN);
> +#endif
> +
> +    error_init(argv[0]);
> +    qemu_init_exec_dir(argv[0]);
> +
> +    module_call_init(MODULE_INIT_QOM);
> +    module_call_init(MODULE_INIT_TRACE);
> +    qemu_add_opts(&qemu_trace_opts);
> +    qcrypto_init(&error_fatal);
> +    bdrv_init();
> +
> +    if (qemu_init_main_loop(&local_err)) {
> +        error_report_err(local_err);
> +        return EXIT_FAILURE;
> +    }
> +
> +    ret = process_options(argc, argv, &local_err);
> +    if (ret < 0) {
> +        error_report_err(local_err);
> +        return EXIT_FAILURE;
> +    }
> +
> +    return EXIT_SUCCESS;
> +}

Quite a trivial shell for now, but looks interesting.  Sadly, I don't 
have much time to review the rest of the series until after KVM Forum, 
which means getting this in (even as experimental) for 4.2 is at risk.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org