smb: smbdirect: introduce smbdirect_connection_{create,destroy}_mem_pools()

smb: smbdirect: introduce smbdirect_connection_{create,destroy}_mem_pools()

This is based on smb_direct_{create,destroy}_pools() in the server.

But it doesn't use smbdirect_connection_get_recv_io() on cleanup,
instead it uses list_for_each_entry_safe()...

It also keep some logic to allow userspace access to
smbdirect_recv_io payload, which is needed for the client
code. But it exposes the whole payload including the
smbdirect_data_transfer header as documentation says
data_offset = 0 and data_length != 0 would be valid,
while the existing client code requires data_offset >= 24.

This should replace the related server functions and also
be used on the client.

It also abstracts recv_io.mem.gfp_mask in order to
allow server to keep using __GFP_RETRY_MAYFAIL.

It also uses struct kmem_cache_args consistently
as that's the currently preferred version of
kmem_cache_create(). And it makes use of the
mempool_create_slab_pool() helper.

And it uses list_add_tail() just to let me feel
better when looking at the code...

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>