bcache: inflight prefetch requests block overlapped normal requests

euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4LOJ6


CVE: NA

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Add a list to save all prefetch requests. When an IO request comes,
check if the request has overlap with some of prefetch requests. If
it das have, block the request until the prefetch request is end.

Add a switch to control whether to enable this. If not enabled, count
the overlapped IO request as a fake hit for performance analysis.

Signed-off-by: Li Ruilin <liruilin4@huawei.com>
Reviewed-by: Luan Jianhai <luanjianhai@huawei.com>
Reviewed-by: Peng Junyi <pengjunyi1@huawei.com>
Acked-by: Xie Xiuqi <xiexiuqi@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-by: Guangxing Deng <dengguangxing@huawei.com>
Reviewed-by: chao song <chao.song@huawei.com>
Reviewed-by: chao song <chao.song@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>