pkg/spec.InitFSMounts: optimize

Instead of getting mount options from /proc/self/mountinfo, which is
very costly to read/parse (and can even be unreliable), let's use
statfs(2) to figure out the flags we need.

[v2: move getting default options to pkg/util, make it linux-specific]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/pkg/util/mountOpts_linux.go b/pkg/util/mountOpts_linux.go
new file mode 100644
index 000000000..3eac4dd25
--- /dev/null
+++ b/pkg/util/mountOpts_linux.go
@@ -0,0 +1,23 @@
+package util
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func getDefaultMountOptions(path string) (defaultMountOptions, error) {
+	opts := defaultMountOptions{true, true, true}
+	if path == "" {
+		return opts, nil
+	}
+	var statfs unix.Statfs_t
+	if e := unix.Statfs(path, &statfs); e != nil {
+		return opts, &os.PathError{Op: "statfs", Path: path, Err: e}
+	}
+	opts.nodev = (statfs.Flags&unix.MS_NODEV == unix.MS_NODEV)
+	opts.noexec = (statfs.Flags&unix.MS_NOEXEC == unix.MS_NOEXEC)
+	opts.nosuid = (statfs.Flags&unix.MS_NOSUID == unix.MS_NOSUID)
+
+	return opts, nil
+}