machined: "machinectl clean" can take a while, do it asynchronously from a background process

This is a follow-up to 5d2036b5f3506bd0ff07042aee8d69c26db32298, and also makes
the "machinectl clean" verb asynchronous, after all it's little more than a
series of image removals.

The changes required to make this happen are a bit more comprehensive as we
need to pass information about deleted images back to the client, as well as
information about the image we failed on if we failed on one. Hence, create a
temporary file in /tmp, serialize that data into, and read it from the parent
after the operation is complete.

1 files changed, 13 insertions, 6 deletions

diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index 5ca557abbf..d68c50b203 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -2375,7 +2375,7 @@ static int set_limit(int argc, char *argv[], void *userdata) {
 }
 
 static int clean_images(int argc, char *argv[], void *userdata) {
-        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         uint64_t usage, total = 0;
         char fb[FORMAT_BYTES_MAX];
@@ -2384,15 +2384,22 @@ static int clean_images(int argc, char *argv[], void *userdata) {
         unsigned c = 0;
         int r;
 
-        r = sd_bus_call_method(
+        r = sd_bus_message_new_method_call(
                         bus,
+                        &m,
                         "org.freedesktop.machine1",
                         "/org/freedesktop/machine1",
                         "org.freedesktop.machine1.Manager",
-                        "CleanPool",
-                        &error,
-                        &reply,
-                        "s", arg_all ? "all" : "hidden");
+                        "CleanPool");
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        r = sd_bus_message_append(m, "s", arg_all ? "all" : "hidden");
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        /* This is a slow operation, hence permit a longer time for completion. */
+        r = sd_bus_call(bus, m, USEC_INFINITY, &error, &reply);
         if (r < 0)
                 return log_error_errno(r, "Could not clean pool: %s", bus_error_message(&error, r));