On 10/20/21 6:20 PM, Jason Gunthorpe wrote: > On Sun, Oct 10, 2021 at 06:59:28PM -0500, Bob Pearson wrote: >> In rxe_pool.c currently there are many cases where it is necessary to >> compute the offset from a pool element struct to the object containing >> the pool element in a type independent way. By saving a pointer to the >> object when they are created extra work can be saved. >> >> Signed-off-by: Bob Pearson <rpearsonhpe@xxxxxxxxx> >> --- >> drivers/infiniband/sw/rxe/rxe_pool.c | 16 +++++++++------- >> drivers/infiniband/sw/rxe/rxe_pool.h | 1 + >> 2 files changed, 10 insertions(+), 7 deletions(-) > > This would be better to just add a static_assert or build_bug_on that > the offsetof() the rxe_pool_entry == 0. There is no reason for these > to be sprinkled at every offset > > Then you don't need to do anything at all > > Jason > I think you missed something. Once upon a time all the rxe objects had the local pool entry struct followed by the ib_xx struct and then anything else needed locally. As Leon has been moving the allocations to rdma-core he had to make the ib_xx struct first followed by the pool element. So there is a mish mash of offsets. Some are/were 0, and the rest are all different depending on the size of the struct from rdma-core. E.g. sizeof(struct ib_mr) != sizeof(struct ib_qp), etc. In order to make the API simple and consistent I use a macro to convert from object to pool elem. e.g. #define some_function(void *obj) __some_function(&obj->elem) but to convert back from elem to obj we need to subtract some random offset e.g. obj = elem->obj; without knowing the type of obj which is simpler than what we had before, roughly struct rxe_pool_info *info = &pool_info[elem->pool->type]; obj = (u8 *)(elem - info->elem_offset);
