RDMA/mlx5: Use a union inside mlx5_ib_mr
The struct mlx5_ib_mr can be used for three different things, but only one
at a time:
- In the user MR cache
- As a kernel MR
- As a user MR
Overlay the three things into a single union with the following rules:
- If the mr is found on the cache_ent->head list then it is a cache MR
and umem == NULL. The entire union is zero after the MR is removed from
the cache.
- If umem != NULL or type == IB_MR_TYPE_USER then it is a user MR.
- If umem == NULL then it is a kernel MR
This reduces the size of struct mlx5_ib_mr to 552 bytes from 702.
The only place the three flows overlap in the code is during dereg, so add
a few extra checks along there.
Link: https://lore.kernel.org/r/20210304120745.1090751-3-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>