QStorageInfo不支持只读根文件系统

Question

我在我的debian strech系统上使用qt版本5.7.1。我已经使用overlayfs将我的根文件系统挂载为只读，我已经使用QStorageInfo检查我的SD卡大小。

将rootfs挂载为只读后，我在QStorageInfo挂载的卷中只能获得根目录。

以下是获取存储列表的源码：

foreach (const QStorageInfo &storage, QStorageInfo::mountedVolumes()) {
    if (storage.isValid() && storage.isReady())
        {
            qDebug() << "storage path" << storage.rootPath();
            qDebug()  << "storage name" << storage.name();
            qDebug()  << "storage readonly" << storage.isReadOnly();
            qDebug()  << "storage filesystem type " << storage.fileSystemType();
            qDebug()  << "storage device " << storage.device();
    }
}

上述信号源的输出：

storage path "/"
        storage name ""
        storage readonly true
        storage filesystem type  ""
        storage device  ""

我的/etc/fstab文件包含：

/dev/mmcblk0p1  /               ext4    ro,noatime  0 1
mount_overlay   /var            fuse    nofail,defaults 0 0
mount_overlay   /home           fuse    nofail,defaults 0 0
mount_overlay   /etc            fuse    nofail,defaults 0 0
none            /tmp            tmpfs   defaults    0 0

如果我将rootfs挂载为"rw“，QStorageInfo就能正常工作。以下是"rw“选项中rootfs的输出：

storage path "/"
storage name ""
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/root"
storage path "/run"
storage name ""
storage readonly false
storage filesystem type  "tmpfs"
storage device  "tmpfs"
storage path "/run/lock"
storage name ""
storage readonly false
storage filesystem type  "tmpfs"
storage device  "tmpfs"
storage path "/tmp"
storage name ""
storage readonly false
storage filesystem type  "tmpfs"
storage device  "none"
storage path "/home"
storage name ""
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/root"
storage path "/var"
storage name ""
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/root"
storage path "/media/data"
storage name "Data"
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/mmcblk0p3"
storage path "/run/user/0"
storage name ""
storage readonly false
storage filesystem type  "tmpfs"
storage device  "tmpfs"
storage path "/home/user/SdCard"
storage name "SDCard"
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/mmcblk1p1"
storage path "/home_org/user/SdCard"
storage name "SDCard"
storage readonly false
storage filesystem type  "ext4"
storage device  "/dev/mmcblk1p1"

当将rootfs设置为读/写权限时，工作正常。当设置为只读时，它不能正常工作

请帮助我理解只读根文件系统的QStorageInfo问题。

Answer 1

QStorageInfo正在尝试读取/etc/mtab以获取已装载的卷。/etc/mtab无法生成，因为存在只读的rootfs。

/etc/mtab是“../proc/self/mount”的符号链接。

因此在创建只读系统之前，需要生成从“../proc/self/mount”到/etc/mtab的smbolink链接。