--fork is a bit boring if there is no way to get the child's PID. This
option helps.
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
qemu-nbd.c | 11 +++++++++++
qemu-nbd.texi | 2 ++
2 files changed, 13 insertions(+)
diff --git a/qemu-nbd.c b/qemu-nbd.c
index dca9e72cee..edb5195208 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -59,6 +59,7 @@
#define QEMU_NBD_OPT_IMAGE_OPTS 262
#define QEMU_NBD_OPT_FORK 263
#define QEMU_NBD_OPT_TLSAUTHZ 264
+#define QEMU_NBD_OPT_PID_FILE 265
#define MBR_SIZE 512
@@ -111,6 +112,7 @@ 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"
+" --pid-file=PATH store the server's process ID in the given file\n"
#if HAVE_NBD_DEVICE
"\n"
"Kernel NBD client support:\n"
@@ -651,6 +653,7 @@ int main(int argc, char **argv)
{ "image-opts", no_argument, NULL, QEMU_NBD_OPT_IMAGE_OPTS },
{ "trace", required_argument, NULL, 'T' },
{ "fork", no_argument, NULL, QEMU_NBD_OPT_FORK },
+ { "pid-file", required_argument, NULL, QEMU_NBD_OPT_PID_FILE },
{ NULL, 0, NULL, 0 }
};
int ch;
@@ -677,6 +680,7 @@ int main(int argc, char **argv)
bool list = false;
int old_stderr = -1;
unsigned socket_activation;
+ const char *pid_file_name = NULL;
/* The client thread uses SIGTERM to interrupt the server. A signal
* handler ensures that "qemu-nbd -v -c" exits with a nice status code.
@@ -876,6 +880,9 @@ int main(int argc, char **argv)
case 'L':
list = true;
break;
+ case QEMU_NBD_OPT_PID_FILE:
+ pid_file_name = optarg;
+ break;
}
}
@@ -1196,6 +1203,10 @@ int main(int argc, char **argv)
nbd_update_server_watch();
+ if (pid_file_name) {
+ qemu_write_pidfile(pid_file_name, &error_fatal);
+ }
+
/* now when the initialization is (almost) complete, chdir("/")
* to free any busy filesystems */
if (chdir("/") < 0) {
diff --git a/qemu-nbd.texi b/qemu-nbd.texi
index de342c76b8..7f55657722 100644
--- a/qemu-nbd.texi
+++ b/qemu-nbd.texi
@@ -117,6 +117,8 @@ option; or provide the credentials needed for connecting as a client
in list mode.
@item --fork
Fork off the server process and exit the parent once the server is running.
+@item --pid-file=PATH
+Store the server's process ID in the given file.
@item --tls-authz=ID
Specify the ID of a qauthz object previously created with the
--object option. This will be used to authorize connecting users
--
2.21.0
On 5/8/19 4:18 PM, Max Reitz wrote:
> --fork is a bit boring if there is no way to get the child's PID. This
> option helps.
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
> qemu-nbd.c | 11 +++++++++++
> qemu-nbd.texi | 2 ++
> 2 files changed, 13 insertions(+)
>
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index dca9e72cee..edb5195208 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -59,6 +59,7 @@
> #define QEMU_NBD_OPT_IMAGE_OPTS 262
> #define QEMU_NBD_OPT_FORK 263
> #define QEMU_NBD_OPT_TLSAUTHZ 264
> +#define QEMU_NBD_OPT_PID_FILE 265
>
> #define MBR_SIZE 512
>
> @@ -111,6 +112,7 @@ 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"
> +" --pid-file=PATH store the server's process ID in the given file\n"
Are we guaranteed that the pid file does not appear until after the
socket has been created?
/me rereads full file...
> @@ -876,6 +880,9 @@ int main(int argc, char **argv)
> case 'L':
> list = true;
> break;
> + case QEMU_NBD_OPT_PID_FILE:
> + pid_file_name = optarg;
> + break;
> }
> }
>
...
socket_activation = check_socket_activation();
if (socket_activation == 0) {
setup_address_and_port(&bindto, &port);
} else {
/* Using socket activation - check user didn't use -p etc. */
...
> @@ -1196,6 +1203,10 @@ int main(int argc, char **argv)
>
> nbd_update_server_watch();
>
> + if (pid_file_name) {
> + qemu_write_pidfile(pid_file_name, &error_fatal);
> + }
Yes, we are. So,
> +
> /* now when the initialization is (almost) complete, chdir("/")
> * to free any busy filesystems */
> if (chdir("/") < 0) {
> diff --git a/qemu-nbd.texi b/qemu-nbd.texi
> index de342c76b8..7f55657722 100644
> --- a/qemu-nbd.texi
> +++ b/qemu-nbd.texi
> @@ -117,6 +117,8 @@ option; or provide the credentials needed for connecting as a client
> in list mode.
> @item --fork
> Fork off the server process and exit the parent once the server is running.
> +@item --pid-file=PATH
> +Store the server's process ID in the given file.
since that is a useful trick to know (the pid file intentionally does
NOT appear until after the socket is ready to go), we should mention it
in the documentation.
I can make that tweak while queueing, if you'd like.
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
On 24.05.19 17:07, Eric Blake wrote:
> On 5/8/19 4:18 PM, Max Reitz wrote:
>> --fork is a bit boring if there is no way to get the child's PID. This
>> option helps.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>> qemu-nbd.c | 11 +++++++++++
>> qemu-nbd.texi | 2 ++
>> 2 files changed, 13 insertions(+)
>>
>> diff --git a/qemu-nbd.c b/qemu-nbd.c
>> index dca9e72cee..edb5195208 100644
>> --- a/qemu-nbd.c
>> +++ b/qemu-nbd.c
>> @@ -59,6 +59,7 @@
>> #define QEMU_NBD_OPT_IMAGE_OPTS 262
>> #define QEMU_NBD_OPT_FORK 263
>> #define QEMU_NBD_OPT_TLSAUTHZ 264
>> +#define QEMU_NBD_OPT_PID_FILE 265
>>
>> #define MBR_SIZE 512
>>
>> @@ -111,6 +112,7 @@ 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"
>> +" --pid-file=PATH store the server's process ID in the given file\n"
>
> Are we guaranteed that the pid file does not appear until after the
> socket has been created?
>
> /me rereads full file...
>
>> @@ -876,6 +880,9 @@ int main(int argc, char **argv)
>> case 'L':
>> list = true;
>> break;
>> + case QEMU_NBD_OPT_PID_FILE:
>> + pid_file_name = optarg;
>> + break;
>> }
>> }
>>
> ...
> socket_activation = check_socket_activation();
> if (socket_activation == 0) {
> setup_address_and_port(&bindto, &port);
> } else {
> /* Using socket activation - check user didn't use -p etc. */
> ...
>
>> @@ -1196,6 +1203,10 @@ int main(int argc, char **argv)
>>
>> nbd_update_server_watch();
>>
>> + if (pid_file_name) {
>> + qemu_write_pidfile(pid_file_name, &error_fatal);
>> + }
>
> Yes, we are. So,
>
>> +
>> /* now when the initialization is (almost) complete, chdir("/")
>> * to free any busy filesystems */
>> if (chdir("/") < 0) {
>> diff --git a/qemu-nbd.texi b/qemu-nbd.texi
>> index de342c76b8..7f55657722 100644
>> --- a/qemu-nbd.texi
>> +++ b/qemu-nbd.texi
>> @@ -117,6 +117,8 @@ option; or provide the credentials needed for connecting as a client
>> in list mode.
>> @item --fork
>> Fork off the server process and exit the parent once the server is running.
>> +@item --pid-file=PATH
>> +Store the server's process ID in the given file.
>
> since that is a useful trick to know (the pid file intentionally does
> NOT appear until after the socket is ready to go), we should mention it
> in the documentation.
>
> I can make that tweak while queueing, if you'd like.
I don’t mind, but I personally find it more useful to just use --fork
and wait for the main process to exit.
Max
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