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[PULL 12/50] qsd: Add --daemonize
From: |
Kevin Wolf |
Subject: |
[PULL 12/50] qsd: Add --daemonize |
Date: |
Fri, 4 Mar 2022 17:46:33 +0100 |
From: Hanna Reitz <hreitz@redhat.com>
To implement this, we reuse the existing daemonizing functions from the
system emulator, which mainly do the following:
- Fork off a child process, and set up a pipe between parent and child
- The parent process waits until the child sends a status byte over the
pipe (0 means that the child was set up successfully; anything else
(including errors or EOF) means that the child was not set up
successfully), and then exits with an appropriate exit status
- The child process enters a new session (forking off again), changes
the umask, and will ignore terminal signals from then on
- Once set-up is complete, the child will chdir to /, redirect all
standard I/O streams to /dev/null, and tell the parent that set-up has
been completed successfully
In contrast to qemu-nbd's --fork implementation, during the set up
phase, error messages are not piped through the parent process.
qemu-nbd mainly does this to detect errors, though (while os_daemonize()
has the child explicitly signal success after set up); because we do not
redirect stderr after forking, error messages continue to appear on
whatever the parent's stderr was (until set up is complete).
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220303164814.284974-4-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
docs/tools/qemu-storage-daemon.rst | 7 +++++++
storage-daemon/qemu-storage-daemon.c | 15 +++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/docs/tools/qemu-storage-daemon.rst
b/docs/tools/qemu-storage-daemon.rst
index 878e6a5c5c..8b97592663 100644
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -154,6 +154,13 @@ Standard options:
created but before accepting connections. The daemon has started successfully
when the pid file is written and clients may begin connecting.
+.. option:: --daemonize
+
+ Daemonize the process. The parent process will exit once startup is complete
+ (i.e., after the pid file has been or would have been written) or failure
+ occurs. Its exit code reflects whether the child has started up successfully
+ or failed to do so.
+
Examples
--------
Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute
diff --git a/storage-daemon/qemu-storage-daemon.c
b/storage-daemon/qemu-storage-daemon.c
index b798954edb..dd18b2cde8 100644
--- a/storage-daemon/qemu-storage-daemon.c
+++ b/storage-daemon/qemu-storage-daemon.c
@@ -93,6 +93,9 @@ static void help(void)
" --chardev <options> configure a character device backend\n"
" (see the qemu(1) man page for possible options)\n"
"\n"
+" --daemonize daemonize the process, and have the parent exit\n"
+" once startup is complete\n"
+"\n"
" --export [type=]nbd,id=<id>,node-name=<node-name>[,name=<export-name>]\n"
" [,writable=on|off][,bitmap=<name>]\n"
" export the specified block node over NBD\n"
@@ -144,6 +147,7 @@ QEMU_HELP_BOTTOM "\n",
enum {
OPTION_BLOCKDEV = 256,
OPTION_CHARDEV,
+ OPTION_DAEMONIZE,
OPTION_EXPORT,
OPTION_MONITOR,
OPTION_NBD_SERVER,
@@ -200,6 +204,7 @@ static void process_options(int argc, char *argv[], bool
pre_init_pass)
static const struct option long_options[] = {
{"blockdev", required_argument, NULL, OPTION_BLOCKDEV},
{"chardev", required_argument, NULL, OPTION_CHARDEV},
+ {"daemonize", no_argument, NULL, OPTION_DAEMONIZE},
{"export", required_argument, NULL, OPTION_EXPORT},
{"help", no_argument, NULL, 'h'},
{"monitor", required_argument, NULL, OPTION_MONITOR},
@@ -225,6 +230,7 @@ static void process_options(int argc, char *argv[], bool
pre_init_pass)
c == '?' ||
c == 'h' ||
c == 'V' ||
+ c == OPTION_DAEMONIZE ||
c == OPTION_PIDFILE;
/* Process every option only in its respective pass */
@@ -277,6 +283,12 @@ static void process_options(int argc, char *argv[], bool
pre_init_pass)
qemu_opts_del(opts);
break;
}
+ case OPTION_DAEMONIZE:
+ if (os_set_daemonize(true) < 0) {
+ error_report("--daemonize not supported in this build");
+ exit(EXIT_FAILURE);
+ }
+ break;
case OPTION_EXPORT:
{
Visitor *v;
@@ -367,6 +379,8 @@ int main(int argc, char *argv[])
process_options(argc, argv, true);
+ os_daemonize();
+
module_call_init(MODULE_INIT_QOM);
module_call_init(MODULE_INIT_TRACE);
qemu_add_opts(&qemu_trace_opts);
@@ -389,6 +403,7 @@ int main(int argc, char *argv[])
* it.
*/
pid_file_init();
+ os_setup_post();
while (!exit_requested) {
main_loop_wait(false);
--
2.35.1
- [PULL 01/50] crypto: perform permission checks under BQL, (continued)
- [PULL 01/50] crypto: perform permission checks under BQL, Kevin Wolf, 2022/03/04
- [PULL 05/50] block: move BQL logic of bdrv_co_invalidate_cache in bdrv_activate, Kevin Wolf, 2022/03/04
- [PULL 04/50] block: rename bdrv_invalidate_cache_all, blk_invalidate_cache and test_sync_op_invalidate_cache, Kevin Wolf, 2022/03/04
- [PULL 06/50] tls: add macros for coroutine-safe TLS variables, Kevin Wolf, 2022/03/04
- [PULL 08/50] rcu: use coroutine TLS macros, Kevin Wolf, 2022/03/04
- [PULL 09/50] cpus: use coroutine TLS macros for iothread_locked, Kevin Wolf, 2022/03/04
- [PULL 11/50] qsd: Add pre-init argument parsing pass, Kevin Wolf, 2022/03/04
- [PULL 14/50] main-loop.h: introduce qemu_in_main_thread(), Kevin Wolf, 2022/03/04
- [PULL 15/50] main loop: macros to mark GS and I/O functions, Kevin Wolf, 2022/03/04
- [PULL 10/50] os-posix: Add os_set_daemonize(), Kevin Wolf, 2022/03/04
- [PULL 12/50] qsd: Add --daemonize,
Kevin Wolf <=
- [PULL 07/50] util/async: replace __thread with QEMU TLS macros, Kevin Wolf, 2022/03/04
- [PULL 13/50] iotests/185: Add post-READY quit tests, Kevin Wolf, 2022/03/04
- [PULL 21/50] block/block-backend.c: assertions for block-backend, Kevin Wolf, 2022/03/04
- Re: [PULL 21/50] block/block-backend.c: assertions for block-backend, Emanuele Giuseppe Esposito, 2022/03/16
[PULL 18/50] IO_CODE and IO_OR_GS_CODE for block I/O API, Kevin Wolf, 2022/03/04