[PATCH v4 6/7] qga/commands-posix: don't do fork()/exec() when suspending via sysfs

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

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>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qga/commands-posix.c | 41 +++++------------------------------------
 1 file changed, 5 insertions(+), 36 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 9b993772f5..9910957ff5 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;
+    g_autoptr(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);
         return;
     }
-
-    if (WEXITSTATUS(status)) {
-        error_setg(errp, "child process has failed to suspend");
-    }
-
 }
 
 static void guest_suspend(SuspendMode mode, Error **errp)
-- 
2.39.3