fix(client): fix the inconsistency of mtime returned by list and get_…

[bigbigxu]

fix the inconsistency of mtime returned by list and get_status under cache-mode, which causes page cache invalidation.

[Copilot]

Pull request overview

This PR aims to eliminate mtime inconsistencies in cache-mode by aligning the mtime exposed by cached reads with the underlying UFS mtime, preventing downstream page-cache invalidation caused by mismatched timestamps.

Changes:

• Make blocks mutable in get_cv_reader() so its returned FileStatus can be adjusted.
• In cache-mode (when cache is considered valid), overwrite blocks.status.mtime with blocks.status.storage_policy.ufs_mtime before constructing the FsReader.

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[Copilot]

In cache-mode, check_cache_validity() returns Valid immediately when mount.info.read_verify_ufs is false, without ensuring storage_policy.ufs_mtime is populated. Since StoragePolicy::ufs_mtime defaults to 0, this assignment can cause the reader’s status().mtime to become 0 for cached entries that don't have ufs_mtime set, which is a behavior change and can break mtime-based cache/page-cache logic. Consider guarding the assignment (only overwrite when ufs_mtime > 0), or obtaining the UFS mtime (e.g., via mount.ufs.get_status) when ufs_mtime is missing so the reader mtime stays consistent with get_status/list_status.

Suggested change

	blocks.status.mtime = blocks.status.storage_policy.ufs_mtime;
	if blocks.status.storage_policy.ufs_mtime > 0 {
	blocks.status.mtime = blocks.status.storage_policy.ufs_mtime;
	}