ascend inclusion
category: feature
bugzilla: NA
CVE: NA

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We have two independent memory regions: normal 8T region and 16G DVPP
region. When an spa is freed, new cache node found by rb_prev() may be
located in the other region.

When this happens, cached_vstart should be changed, otherwise the next
new allocated spa may be in the wrong region.
Signed-off-by: NTang Yizhou <tangyizhou@huawei.com>
Reviewed-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>