ovl: remove privs in ovl_copyfile()

stable inclusion
from stable-v5.10.169
commit f6f94837d92f0f5f94700589bab6d880009dfc22
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7V9QX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6f94837d92f0f5f94700589bab6d880009dfc22



----------------------------------------------------

commit b306e90f upstream.

Underlying fs doesn't remove privs because copy_range/remap_range are
called with privileged mounter credentials.

This fixes some failures in fstest generic/673.

Fixes: 8ede2055 ("ovl: add reflink/copyfile/dedup support")
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>