diff options
| -rw-r--r-- | src/nspawn/nspawn-mount.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c index 2dabe2ae5b..1814ea6ca5 100644 --- a/src/nspawn/nspawn-mount.c +++ b/src/nspawn/nspawn-mount.c @@ -288,10 +288,17 @@ int mount_sysfs(const char *dest) { x = prefix_roota(top, "/fs/kdbus"); (void) mkdir_p(x, 0755); - /* Create mountpoint for cgroups. Otherwise we are not allowed since we - * remount /sys read-only. - */ - if (cg_ns_supported()) { + /* We need to ensure that /sys/fs/cgroup exists before we remount /sys read-only. + * + * If !use_cgns, then this was already done by the outer child; so we only need to do it here it if use_cgns. + * This function doesn't know whether use_cgns, but !cg_ns_supported()⇒!use_cgns, so we can "optimize" the case + * where we _know_ !use_cgns, and deal with a no-op mkdir_p() in the false-positive where cgns_supported() but + * !use_cgns. + * + * But is it really much of an optimization? We're potentially spending an access(2) (cg_ns_supported() could + * be cached from a previous call) to potentially save an lstat(2) and mkdir(2); and all of them are on virtual + * fileystems, so they should all be pretty cheap. */ + if (cg_ns_supported()) { /* if (use_cgns) { */ x = prefix_roota(top, "/fs/cgroup"); (void) mkdir_p(x, 0755); } |