mm/sharepool: Clear the initialization of sp-associated structure for a process

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EORS


CVE: NA

--------------------------------

A few structures must have been created when a process want to get into
sharepool subsystem, including allocating sharepool memory, being added
into a spg or doing k2u and so on.

Currently we create those structures just before we actually need them.
For example, we find or create a sp_spa_stat after a successful memory
allocation and before updating the statistical structure. The creation of
a new structure may fail due to oom and we should then reclaim the
memory allocated and revert all the process before. Or we just forget to
do that and a potential memory-leak occurs. This design makes it
confused when we indeed create a structure and we always worry about
potential memory-leak when we changes the code around it.

A better solution is to initialize all that structures at the same time
when a process join in sharepool subsystem. And in future, we will clear
the unnecessary statistical structures.

Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>