[systemd-devel] [PATCH 1/2] nspawn: only mount the cgroup root if it's not already mounted

[Iago López Galeiras]

This allows the user to set the cgroups manually before calling nspawn.
---
 src/nspawn/nspawn.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 2f7dd53..c67cab2 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -1053,6 +1053,21 @@ static int mount_cgroup_hierarchy(const char *dest, const char *controller, cons
         return 1;
 }
 
+static int mount_cgroup_tmpfs(const char *cgroup_root) {
+        int r;
+
+        r = path_is_mount_point(cgroup_root, false);
+        if (r < 0 && r != -ENOENT)
+                return log_error_errno(r, "Failed to determine if %s is mounted already: %m", cgroup_root);
+        if (r > 0)
+                return 0;
+
+        if (mount("tmpfs", cgroup_root, "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, "mode=755") < 0)
+                return log_error_errno(errno, "Failed to mount tmpfs to /sys/fs/cgroup: %m");
+
+        return 1;
+}
+
 static int mount_cgroup(const char *dest) {
         _cleanup_set_free_free_ Set *controllers = NULL;
         _cleanup_free_ char *own_cgroup_path = NULL;
@@ -1072,8 +1087,9 @@ static int mount_cgroup(const char *dest) {
                 return log_error_errno(r, "Failed to determine our own cgroup path: %m");
 
         cgroup_root = strjoina(dest, "/sys/fs/cgroup");
-        if (mount("tmpfs", cgroup_root, "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, "mode=755") < 0)
-                return log_error_errno(errno, "Failed to mount tmpfs to /sys/fs/cgroup: %m");
+        r = mount_cgroup_tmpfs(cgroup_root);
+        if (r < 0)
+                return r;
 
         for (;;) {
                 _cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL;
-- 
2.4.0