Refactor mountinfo parsing

Signed-off-by: Ben Kochie <superq@gmail.com>

Author: SuperQ

collector/filesystem_linux.go

@@ -31,6 +31,8 @@ import (
 
 	"github.com/alecthomas/kingpin/v2"
 	"golang.org/x/sys/unix"
+
+	"github.com/prometheus/procfs"
 )
 
 const (
@@ -179,25 +181,27 @@ func stuckMountWatcher(mountPoint string, success chan struct{}, logger *slog.Lo
 }
 
 func mountPointDetails(logger *slog.Logger) ([]filesystemLabels, error) {
-	file, err := os.Open(procFilePath("1/mountinfo"))
+	fs, err := procfs.NewFS(*procPath)
+  if err != nil {
+    return nil, fmt.Errorf("failed to open procfs: %w", err)
+  }
+	mountInfo, err := fs.GetProcMounts(1)
 	if errors.Is(err, os.ErrNotExist) {
 		// Fallback to `/proc/self/mountinfo` if `/proc/1/mountinfo` is missing due hidepid.
 		logger.Debug("Reading root mounts failed, falling back to self mounts", "err", err)
-		file, err = os.Open(procFilePath("self/mountinfo"))
+		mountInfo, err = fs.GetMounts()
 	}
 	if err != nil {
 		return nil, err
 	}
-	defer file.Close()
 
 	return parseFilesystemLabels(file)
 }
 
-func parseFilesystemLabels(r io.Reader) ([]filesystemLabels, error) {
+func parseFilesystemLabels(mountInfo []*procfs.MountInfo) ([]filesystemLabels, error) {
 	var filesystems []filesystemLabels
 
-	scanner := bufio.NewScanner(r)
-	for scanner.Scan() {
+	for mount in range mountInfo {
 		parts := strings.Fields(scanner.Text())
 
 		if len(parts) < 11 {