On Fri, Mar 01, 2024 at 07:28:57PM +0200, Andrey Drobyshev wrote:
> We replace the direct call to open() with a "sh -c 'echo ...'" call, so
> that it becomes an executable command.
Introduced an indirection via the shell is a significant step
backwards IMHO.
>
> Signed-off-by: Andrey Drobyshev <andrey.drobys...@virtuozzo.com>
> ---
> qga/commands-posix.c | 36 ++++--------------------------------
> 1 file changed, 4 insertions(+), 32 deletions(-)
>
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index dd2a7ad2e6..f3f4a05e2d 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -1921,49 +1921,21 @@ static void linux_sys_state_suspend(SuspendMode mode,
> Error **errp)
> Error *local_err = 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);
This pre-existing code is strange to me. Why do we need to fork a
new process in order to write to /sys/power/state ?
Looking at the original commit
commit 11d0f1255bd5651f628280dc96c4ce9d63ae9236
Author: Luiz Capitulino <lcapitul...@redhat.com>
Date: Tue Feb 28 11:03:03 2012 -0300
qemu-ga: add guest-suspend-disk
The code made a little more sense, as after fork() it first
tried to execve 'pm-utils', and then had the sysfs codepath
as a fallback. IOW having the sysfs code after fork() was a
much easier code structure.
This was all changed in
commit 246d76eba1944d7e59affb288ec27d7fcfb5d256
Author: Daniel Henrique Barboza <danielhb...@gmail.com>
Date: Thu Jun 21 07:21:50 2018 -0300
qga: guest_suspend: decoupling pm-utils and sys logic
so the pm-utils logic runs in a separate forked child
from the sysfs logic.
AFAICT, that should have made it completely redundant to
fork a process to access /sys/power/state.
Does anyone know of a reason to keep the fork() here ? Of
not we should just be calling 'g_file_set_contents' without
fork
> - } else if (pid < 0) {
> - error_setg_errno(errp, errno, "failed to create child process");
> - return;
> - }
> + g_autofree char *echo_cmd = g_strdup_printf(
> + "echo %s > " LINUX_SYS_STATE_FILE, sysfile_str);
> + const char *argv[] = {"sh", "-c", echo_cmd, NULL};
>
> - ga_wait_child(pid, &status, &local_err);
> + ga_run_command(argv, NULL, "suspend", &local_err);
> if (local_err) {
> error_propagate(errp, local_err);
> 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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