ceph: fix deadlock or deadcode of misusing dget()

mainline inclusion
from mainline-v6.8-rc1
commit b493ad718b1f0357394d2cdecbf00a44a36fa085
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I96G92
CVE: CVE-2023-52583

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b493ad718b1f0357394d2cdecbf00a44a36fa085

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

The lock order is incorrect between denty and its parent, we should
always make sure that the parent get the lock first.

But since this deadcode is never used and the parent dir will always
be set from the callers, let's just remove it.

Link: https://lore.kernel.org/r/20231116081919.GZ1957730@ZenIV


Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yifan Qiao <qiaoyifan4@huawei.com>