c/r: write status only after trying to parse the pid

Previously, we write a "success" status but tried to parse the pid. This
meant that we wouldn't notice a successful restore but failure to parse the
pid, which was a little strange.

We still don't know the child pid, so we will end up with a restored
process tree and a running container, but at least in this case the API
will return false indicating that something failed.

We could kill(-1, 9) in this case, but since liblxc runs as root sometimes
(e.g. LXD), that would be a Very Bad Thing.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index 5a48c7203ea6f2b5f1e86290f43bfd09e7313693..71c9b9c32d81bd84b71eaf50307760971e86034d 100644 (file)
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -723,15 +723,6 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
                        goto out_fini_handler;
                }
 
-               ret = write(status_pipe, &status, sizeof(status));
-               close(status_pipe);
-               status_pipe = -1;
-
-               if (sizeof(status) != ret) {
-                       SYSERROR("failed to write all of status");
-                       goto out_fini_handler;
-               }
-
                if (WIFEXITED(status)) {
                        char buf[4096];
 
@@ -780,6 +771,15 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
 
                close(pipes[0]);
 
+               ret = write(status_pipe, &status, sizeof(status));
+               close(status_pipe);
+               status_pipe = -1;
+
+               if (sizeof(status) != ret) {
+                       SYSERROR("failed to write all of status");
+                       goto out_fini_handler;
+               }
+
                /*
                 * See comment in lxcapi_start; we don't care if these
                 * fail because it's just a beauty thing. We just
@@ -805,7 +805,12 @@ out_fini_handler:
 
 out:
        if (status_pipe >= 0) {
-               status = 1;
+               /* ensure getting here was a failure, e.g. if we failed to
+                * parse the child pid or something, even after a successful
+                * restore
+                */
+               if (!status)
+                       status = 1;
                if (write(status_pipe, &status, sizeof(status)) != sizeof(status)) {
                        SYSERROR("writing status failed");
                }