Re: [PATCH v3 6/7] qga/commands-posix: don't do fork()/exec() when suspending via sysfs

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Mar 15, 2024 at 02:29:45PM +0200, Andrey Drobyshev wrote:
> Since commit 246d76eba ("qga: guest_suspend: decoupling pm-utils and sys
> logic") pm-utils logic is running in a separate child from the sysfs
> logic.  Now when suspending via sysfs we don't really need to do that in
> a separate process as we only need to perform one write to /sys/power/state.
> 
> Let's just use g_file_set_contents() to simplify things here.
> 
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> ---
>  qga/commands-posix.c | 41 +++++------------------------------------
>  1 file changed, 5 insertions(+), 36 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 610d225d30..e0ea377f65 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -1928,52 +1928,21 @@ static bool linux_sys_state_supports_mode(SuspendMode mode, Error **errp)
>  
>  static void linux_sys_state_suspend(SuspendMode mode, Error **errp)
>  {
> -    Error *local_err = NULL;
> +    GError *local_gerr = NULL;
>      const char *sysfile_strs[3] = {"disk", "mem", NULL};
>      const char *sysfile_str = sysfile_strs[mode];
> -    pid_t pid;
> -    int status;
>  
>      if (!sysfile_str) {
>          error_setg(errp, "unknown guest suspend mode");
>          return;
>      }
>  
> -    pid = fork();
> -    if (!pid) {
> -        /* child */
> -        int fd;
> -
> -        setsid();
> -        reopen_fd_to_null(0);
> -        reopen_fd_to_null(1);
> -        reopen_fd_to_null(2);
> -
> -        fd = open(LINUX_SYS_STATE_FILE, O_WRONLY);
> -        if (fd < 0) {
> -            _exit(EXIT_FAILURE);
> -        }
> -
> -        if (write(fd, sysfile_str, strlen(sysfile_str)) < 0) {
> -            _exit(EXIT_FAILURE);
> -        }
> -
> -        _exit(EXIT_SUCCESS);
> -    } else if (pid < 0) {
> -        error_setg_errno(errp, errno, "failed to create child process");
> -        return;
> -    }
> -
> -    ga_wait_child(pid, &status, &local_err);
> -    if (local_err) {
> -        error_propagate(errp, local_err);
> +    if (!g_file_set_contents(LINUX_SYS_STATE_FILE, sysfile_str,
> +                             -1, &local_gerr)) {
> +        error_setg(errp, "suspend: cannot write to '%s': %s",
> +                   LINUX_SYS_STATE_FILE, local_gerr->message);

You need to declare with "g_autoptr(GError) local_gerr = NULL" to
avoid a leak here.

>          return;
>      }
> -
> -    if (WEXITSTATUS(status)) {
> -        error_setg(errp, "child process has failed to suspend");
> -    }
> -
>  }
>  
>  static void guest_suspend(SuspendMode mode, Error **errp)
> -- 
> 2.39.3
> 

With regards,
Daniel
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