hulk inclusion
category: bugfix
bugzilla: 185894, https://gitee.com/openeuler/kernel/issues/I4SJ8H?from=project-issue
CVE: NA

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This reverts commit b0d9aeb4.

This commit b0d9aeb4 ("dm space maps: don't reset space map allocation
cursor when committing") change the way to find free block.

But when use ramdisk(not support discard) for thin-pool,and storage
over-commitment. Then constantly create and delete file, can find block
in thin-pool, but can't find block in ramdisk.

So need revert this patch.
Signed-off-by: NLuo Meng <luomeng12@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>