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, 31 insertions, 10 deletions

diff --git a/src/machine/operation.c b/src/machine/operation.c
index e6ddc41a55..8f8321a8b3 100644
--- a/src/machine/operation.c
+++ b/src/machine/operation.c
@@ -41,18 +41,33 @@ static int operation_done(sd_event_source *s, const siginfo_t *si, void *userdat
                 goto fail;
         }
 
-        if (si->si_status != EXIT_SUCCESS) {
-                if (read(o->errno_fd, &r, sizeof(r)) == sizeof(r))
-                        r = sd_bus_error_set_errnof(&error, r, "%m");
-                else
-                        r = sd_bus_error_setf(&error, SD_BUS_ERROR_FAILED, "Child failed.");
-
+        if (si->si_status == EXIT_SUCCESS)
+                r = 0;
+        else if (read(o->errno_fd, &r, sizeof(r)) != sizeof(r)) { /* Try to acquire error code for failed operation */
+                r = sd_bus_error_setf(&error, SD_BUS_ERROR_FAILED, "Child failed.");
                 goto fail;
         }
 
-        r = sd_bus_reply_method_return(o->message, NULL);
-        if (r < 0)
-                log_error_errno(r, "Failed to reply to message: %m");
+        if (o->done) {
+                /* A completion routine is set for this operation, call it. */
+                r = o->done(o, r, &error);
+                if (r < 0) {
+                        if (!sd_bus_error_is_set(&error))
+                                sd_bus_error_set_errno(&error, r);
+
+                        goto fail;
+                }
+
+        } else {
+                /* The default default operaton when done is to simply return an error on failure or an empty success
+                 * message on success. */
+                if (r < 0)
+                        goto fail;
+
+                r = sd_bus_reply_method_return(o->message, NULL);
+                if (r < 0)
+                        log_error_errno(r, "Failed to reply to message: %m");
+        }
 
         operation_free(o);
         return 0;
@@ -66,7 +81,7 @@ fail:
         return 0;
 }
 
-int operation_new(Manager *manager, Machine *machine, pid_t child, sd_bus_message *message, int errno_fd) {
+int operation_new(Manager *manager, Machine *machine, pid_t child, sd_bus_message *message, int errno_fd, Operation **ret) {
         Operation *o;
         int r;
 
@@ -79,6 +94,8 @@ int operation_new(Manager *manager, Machine *machine, pid_t child, sd_bus_messag
         if (!o)
                 return -ENOMEM;
 
+        o->extra_fd = -1;
+
         r = sd_event_add_child(manager->event, &o->event_source, child, WEXITED, operation_done, o);
         if (r < 0) {
                 free(o);
@@ -102,6 +119,9 @@ int operation_new(Manager *manager, Machine *machine, pid_t child, sd_bus_messag
 
         /* At this point we took ownership of both the child and the errno file descriptor! */
 
+        if (ret)
+                *ret = o;
+
         return 0;
 }
 
@@ -112,6 +132,7 @@ Operation *operation_free(Operation *o) {
         sd_event_source_unref(o->event_source);
 
         safe_close(o->errno_fd);
+        safe_close(o->extra_fd);
 
         if (o->pid > 1)
                 (void) sigkill_wait(o->pid);