RDMA/mlx5: Fix MR cache temp entries cleanup

RDMA/mlx5: Fix MR cache temp entries cleanup

[ Upstream commit 7ebb00cea49db641b458edef0ede389f7004821d ]

Fix the cleanup of the temp cache entries that are dynamically created
in the MR cache.

The cleanup of the temp cache entries is currently scheduled only when a
new entry is created. Since in the cleanup of the entries only the mkeys
are destroyed and the cache entry stays in the cache, subsequent
registrations might reuse the entry and it will eventually be filled with
new mkeys without cleanup ever getting scheduled again.

On workloads that register and deregister MRs with a wide range of
properties we see the cache ends up holding many cache entries, each
holding the max number of mkeys that were ever used through it.

Additionally, as the cleanup work is scheduled to run over the whole
cache, any mkey that is returned to the cache after the cleanup was
scheduled will be held for less than the intended 30 seconds timeout.

Solve both issues by dropping the existing remove_ent_work and reusing
the existing per-entry work to also handle the temp entries cleanup.

Schedule the work to run with a 30 seconds delay every time we push an
mkey to a clean temp entry.
This ensures the cleanup runs on each entry only 30 seconds after the
first mkey was pushed to an empty entry.

As we have already been distinguishing between persistent and temp entries
when scheduling the cache_work_func, it is not being scheduled in any
other flows for the temp entries.

Another benefit from moving to a per-entry cleanup is we now not
required to hold the rb_tree mutex, thus enabling other flow to run
concurrently.

Fixes: dd1b913fb0d0 ("RDMA/mlx5: Cache all user cacheable mkeys on dereg MR flow")
Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Link: https://patch.msgid.link/e4fa4bb03bebf20dceae320f26816cd2dde23a26.1725362530.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>