RDMA/restrack: Improve readability in task name management

Use rdma_restrack_set_name() and rdma_restrack_parent_name() instead of
tricky uses of rdma_restrack_attach_task()/rdma_restrack_uadd().

This uniformly makes all restracks add'd using rdma_restrack_add().

Link: https://lore.kernel.org/r/20200922091106.2152715-6-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

RDMA/restrack: Simplify restrack tracking in kernel flows

Have a single rdma_restrack_add() that adds an entry, there is no reason
to split the user/kernel here, the rdma_restrack_set_task() is responsible
for this difference.

This patch prepares the code to the future requirement of making restrack
is mandatory for managing ib objects.

Link: https://lore.kernel.org/r/20200922091106.2152715-5-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

RDMA/restrack: Count references to the verbs objects

Refactor the restrack code to make sure the kref inside the restrack entry
properly kref's the object in which it is embedded. This slight change is
needed for future conversions of MR and QP which are refcounted before the
release and kfree.

The ideal flow from ib_core perspective as follows:
* Allocate ib_* structure with rdma_zalloc_*.
* Set everything that is known to ib_core to that newly created object.
* Initialize kref with restrack help
* Call to driver specific allocation functions.
* Insert into restrack DB
....
* Return and release restrack with restrack_put.

Largely this means a rdma_restrack_new() should be called near allocating
the containing structure.

Link: https://lore.kernel.org/r/20200922091106.2152715-4-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

RDMA/restrack: Remove PID namespace support

IB resources are bounded to IB device and file descriptors, both entities
are unaware to PID namespaces and to task lifetime.

The difference in model caused to unpredictable behavior for the following
scenario:
1. Create FD and context
2. Share it with ephemeral child
3. Create any object and exit that child

The end result of this flow, that those newly created objects will be
tracked by restrack, but won't be visible for users because task_struct
associated with them already exited.

The right thing is to rely on net namespace only for any filtering
purposes and drop PID namespace.

Link: https://lore.kernel.org/r/20191010071105.25538-2-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

RDMA/restrack: Make is_visible_in_pid_ns() as an API

Remove is_visible_in_pid_ns() from nldev.c and make it as a restrack API,
so that it can be taken advantage by other parts like counter.

Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

RDMA/restrack: Add an API to attach a task to a resource

Add rdma_restrack_attach_task() which is able to attach a task other then
"current" to a resource.

Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

RDMA/restrack: Prepare restrack_root to addition of extra fields per-type

As a preparation to extension of rdma_restrack_root to provide software
IDs, which will be per-type too. We convert the rdma_restrack_root from
struct with arrays to array of structs.

Such conversion allows us to drop rwsem lock in favour of internal XArray
lock.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

RDMA/restrack: Hide restrack DB from IB/core

There is no need to expose internals of restrack DB to IB/core.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>