[CRIU] [PATCH 1/3] [v4] crtools: close a signal descriptor after passing a preparation stage
Mike Rapoport
rppt at linux.vnet.ibm.com
Tue Jan 10 22:45:50 PST 2017
On Wed, Jan 11, 2017 at 12:21:43AM +0300, Andrei Vagin wrote:
> From: Andrei Vagin <avagin at virtuozzo.com>
>
> This patch adds the --siganl-fd FD option to specify a file descriptor.
> CRIU will write '\0' to this descriptor and close it after passing
> a preparation stage.
>
> It is alternative way to demonizing a criu process after a preparation
> stage. It's imposiable to get exit code, if a process has daemonized.
Just curious, what will happen if somebody tries both --daemon and
--status-fd?
> The introduced way allows to wait a preparation stage and to get an exit
> code. It can be easy used from shell and other script languages.
>
> v3: fix a help message
>
> v4: Here is a sequence of actions how it can be used:
> * open a pipe
> * run a service with the pipe[1] as status_fd
> * read(pipe[0]) to wait a moment when the service will be ready to
> accept connections
> * do a work which requires the service
> * wait the service process to gets its exit status to be sure that
> everything okey
>
> Cc: Mike Rapoport <mike.rapoport at gmail.com>
> Cc: Kir Kolyshkin <kir at openvz.org>
> Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
> ---
> Documentation/criu.txt | 6 ++++++
> criu/crtools.c | 10 ++++++++++
> criu/include/cr_options.h | 1 +
> criu/include/util.h | 1 +
> criu/uffd.c | 3 +++
> criu/util.c | 18 ++++++++++++++++++
> 6 files changed, 39 insertions(+)
>
> diff --git a/Documentation/criu.txt b/Documentation/criu.txt
> index b48572c..e8c7e73 100644
> --- a/Documentation/criu.txt
> +++ b/Documentation/criu.txt
> @@ -522,6 +522,12 @@ Launches *criu* in page server mode.
> *--daemon*::
> Runs page server as a daemon (background process).
>
> +*--status_fd*::
> + Write \\0 to the FD and close it once page-server is ready to handle
What about lazy-pages?
> + requests. The status-fd allows to not daemonize a process and get its
> + exit code at the end.
> + It isn't supposed to use --daemon and --status-fd together.
> +
> *--address* 'address'::
> Page server IP address.
>
> diff --git a/criu/crtools.c b/criu/crtools.c
> index 06b2fa7..445b3ba 100644
> --- a/criu/crtools.c
> +++ b/criu/crtools.c
> @@ -76,6 +76,7 @@ void init_opts(void)
> opts.ghost_limit = DEFAULT_GHOST_LIMIT;
> opts.timeout = DEFAULT_TIMEOUT;
> opts.empty_ns = 0;
> + opts.status_fd = -1;
> }
>
> static int parse_join_ns(const char *ptr)
> @@ -286,6 +287,7 @@ int main(int argc, char *argv[], char *envp[])
> { "check-only", no_argument, 0, 1085 },
> { "display-stats", no_argument, 0, 1086 },
> { "weak-sysctls", no_argument, 0, 1087 },
> + { "status-fd", required_argument, 0, 1088 },
> { },
> };
>
> @@ -613,6 +615,12 @@ int main(int argc, char *argv[], char *envp[])
> pr_msg("Will skip non-existant sysctls on restore\n");
> opts.weak_sysctls = true;
> break;
> + case 1088:
> + if (sscanf(optarg, "%d", &opts.status_fd) != 1) {
> + pr_err("Unable to parse a value of --status-fd\n");
> + return 1;
> + }
> + break;
> case 'V':
> pr_msg("Version: %s\n", CRIU_VERSION);
> if (strcmp(CRIU_GITID, "0"))
> @@ -951,6 +959,8 @@ usage:
> " --address ADDR address of server or service\n"
> " --port PORT port of page server\n"
> " -d|--daemon run in the background after creating socket\n"
> +" --status-fd FD write \\0 to the FD and close it once process is ready\n"
> +" to handle requests\n"
> "\n"
> "Other options:\n"
> " -h|--help show this text\n"
> diff --git a/criu/include/cr_options.h b/criu/include/cr_options.h
> index 4f70b41..aaefea3 100644
> --- a/criu/include/cr_options.h
> +++ b/criu/include/cr_options.h
> @@ -119,6 +119,7 @@ struct cr_options {
> bool display_stats;
> bool weak_sysctls;
> bool check_only;
> + int status_fd;
> };
>
> extern struct cr_options opts;
> diff --git a/criu/include/util.h b/criu/include/util.h
> index 1fa0742..775d11e 100644
> --- a/criu/include/util.h
> +++ b/criu/include/util.h
> @@ -171,6 +171,7 @@ extern int cr_system(int in, int out, int err, char *cmd, char *const argv[], un
> extern int cr_system_userns(int in, int out, int err, char *cmd,
> char *const argv[], unsigned flags, int userns_pid);
> extern int cr_daemon(int nochdir, int noclose, int *keep_fd, int close_fd);
> +extern int close_status_fd(void);
> extern int is_root_user(void);
>
> static inline bool dir_dots(const struct dirent *de)
> diff --git a/criu/uffd.c b/criu/uffd.c
> index ade5cbc..0f3b0f3 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -833,6 +833,9 @@ int cr_lazy_pages(bool daemon)
> }
> }
>
> + if (close_status_fd())
> + return -1;
> +
> nr_fds = task_entries->nr_tasks + (opts.use_page_server ? 1 : 0);
> epollfd = epoll_prepare(nr_fds, &events);
> if (epollfd < 0)
> diff --git a/criu/util.c b/criu/util.c
> index 2534a70..f917bc8 100644
> --- a/criu/util.c
> +++ b/criu/util.c
> @@ -690,6 +690,21 @@ out:
> return ret;
> }
>
> +int close_status_fd(void)
> +{
> + char c = 0;
> +
> + if (opts.status_fd < 0)
> + return 0;
> +
> + if (write(opts.status_fd, &c, 1) != 1) {
> + pr_perror("Unable to write into the status fd");
> + return -1;
> + }
> +
> + return close_safe(&opts.status_fd);
> +}
> +
> int cr_daemon(int nochdir, int noclose, int *keep_fd, int close_fd)
> {
> int pid;
> @@ -1155,6 +1170,9 @@ int run_tcp_server(bool daemon_mode, int *ask, int cfd, int sk)
> }
> }
>
> + if (close_status_fd())
> + return -1;
> +
> if (sk >= 0) {
> ret = *ask = accept(sk, (struct sockaddr *)&caddr, &clen);
> if (*ask < 0)
> --
> 2.7.4
>
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