mm: slince possible data races about pgdat->kswapd

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6PKGM

Reference: https://lore.kernel.org/linux-mm/20220824071909.192535-1-wangkefeng.wang@huawei.com/



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The pgdat->kswapd could be accessed concurrently by kswapd_run() and
kcompactd(), it don't be protected by any lock, which could leads to
data races, adding READ/WRITE_ONCE() to slince it.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Conflicts:
	mm/compaction.c
	mm/vmscan.c

Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>