fs: use backing_file container for internal files with "fake" f_path
Overlayfs uses open_with_fake_path() to allocate internal kernel files,
with a "fake" path - whose f_path is not on the same fs as f_inode.
Allocate a container struct backing_file for those internal files, that
is used to hold the "fake" ovl path along with the real path.
backing_file_real_path() can be used to access the stored real path.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <
20230615112229.
2143178-5-amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>