Store the file struct used as the holder in file->private_data as an
indicator that this file descriptor was opened exclusively to  remove
the last use of FMODE_EXCL.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20230608110258.189493-30-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>