There is no reason now not to use kvmalloc, so replace the internal
metadata allocation scheme.
Reviewed-by: NJavier González <javier@javigon.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NHans Holmberg <hans@owltronix.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>