mm/dynamic_hugetlb: alloc page from dhugetlb_pool

hulk inclusion
category: feature
bugzilla: 46904, https://gitee.com/openeuler/kernel/issues/I4QSHG


CVE: NA

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Add function to alloc page from dhugetlb_pool.
When process is bound to a mem_cgroup configured with dhugtlb_pool, alloc
page from dhugetlb_pool firstly. If there is no page in dhugetlb_pool,
fallback to alloc page from buddy system.

As the process will alloc pages from dhugetlb_pool in the mem_cgroup,
process is not allowed to migrate to other mem_cgroup.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>