Fix remounting /system on Android.

This adds the missing "relatime" option, fixes error handling logic (mount
returns 0/-1, not an errno value, and I at least get EACCES rather than
EROFS in the case where the underlying block device is read-only; we should
also probably only try again if the ioctl actually succeeded), and adds the
missing newline in case where we go around and try again read-only.

The test case was "mount -o rw,remount /system" on Android.

toys/lsb/mount.c

@@ -91,6 +91,7 @@ static long flag_opts(char *new, long flags, char **more)
  {"noexec", MS_NOEXEC}, {"exec", ~MS_NOEXEC},
  {"sync", MS_SYNCHRONOUS}, {"async", ~MS_SYNCHRONOUS},
  {"noatime", MS_NOATIME}, {"atime", ~MS_NOATIME},
+ {"norelatime", ~MS_RELATIME}, {"relatime", MS_RELATIME},
  {"nodiratime", MS_NODIRATIME}, {"diratime", ~MS_NODIRATIME},
  {"loud", ~MS_SILENT},
  {"shared", MS_SHARED}, {"rshared", MS_SHARED|MS_REC},
@@ -195,16 +196,21 @@ static void mount_filesystem(char *dev, char *dir, char *type,
  printf("try '%s' type '%s' on '%s'\n", dev, type, dir);
  for (;;) {
  rc = mount(dev, dir, type, flags, opts);
- if ((rc != EACCES && rc != EROFS) || (flags & MS_RDONLY)) break;
- if (rc == EROFS && fd == -1) {
+ // Did we succeed, fail unrecoverably, or already try read-only?
+ if (rc == 0 || (errno != EACCES && errno != EROFS) || (flags&MS_RDONLY))
+ break;
+ // If we haven't already tried it, use the BLKROSET ioctl to ensure
+ // that the underlying device isn't read-only.
+ if (fd == -1) {
+ if (toys.optflags & FLAG_v)
+ printf("trying BLKROSET ioctl on '%s'\n", dev);
  if (-1 != (fd = open(dev, O_RDONLY))) {
- ioctl(fd, BLKROSET, &ro);
+ rc = ioctl(fd, BLKROSET, &ro);
  close(fd);
-
- continue;
+ if (rc == 0) continue;
  }
  }
- fprintf(stderr, "'%s' is read-only", dev);
+ fprintf(stderr, "'%s' is read-only\n", dev);
  flags |= MS_RDONLY;
  }