svcrdma: fix miss destroy percpu_counter in svc_rdma_proc_init()

[ Upstream commit ce89e742 ]

There's issue as follows:
RPC: Registered rdma transport module.
RPC: Registered rdma backchannel transport module.
RPC: Unregistered rdma transport module.
RPC: Unregistered rdma backchannel transport module.
BUG: unable to handle page fault for address: fffffbfff80c609a
PGD 123fee067 P4D 123fee067 PUD 123fea067 PMD 10c624067 PTE 0
Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
RIP: 0010:percpu_counter_destroy_many+0xf7/0x2a0
Call Trace:
 <TASK>
 __die+0x1f/0x70
 page_fault_oops+0x2cd/0x860
 spurious_kernel_fault+0x36/0x450
 do_kern_addr_fault+0xca/0x100
 exc_page_fault+0x128/0x150
 asm_exc_page_fault+0x26/0x30
 percpu_counter_destroy_many+0xf7/0x2a0
 mmdrop+0x209/0x350
 finish_task_switch.isra.0+0x481/0x840
 schedule_tail+0xe/0xd0
 ret_from_fork+0x23/0x80
 ret_from_fork_asm+0x1a/0x30
 </TASK>

If register_sysctl() return NULL, then svc_rdma_proc_cleanup() will not
destroy the percpu counters which init in svc_rdma_proc_init().
If CONFIG_HOTPLUG_CPU is enabled, residual nodes may be in the
'percpu_counters' list. The above issue may occur once the module is
removed. If the CONFIG_HOTPLUG_CPU configuration is not enabled, memory
leakage occurs.
To solve above issue just destroy all percpu counters when
register_sysctl() return NULL.

Fixes: 1e7e5573 ("svcrdma: Restore read and write stats")
Fixes: 22df5a22 ("svcrdma: Convert rdma_stat_sq_starve to a per-CPU counter")
Fixes: df971cd8 ("svcrdma: Convert rdma_stat_recv to a per-CPU counter")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>