I would recommend splitting up this PR further so that each commit represents a single logical change. From looking over this, I see the following distinct changes:

• Moving move_and_async_delete_path() (and friends) to snapshot_utils
• Changing behavior of cleanup_accounts_paths()
• Adding more to the debug log in try_recycle_store()
• Adding more to the error message in AppendVec::new_from_file()
• Adding more to the warning in add_builtin_account()
• Using checked-math to make reconstruct_accountsdb_from_fields() safer
• Fixing the doc-comment on packager_thread_niceness_adj in SnapshotConfig
• Refactor out snapshot_write_version_file()
• Update log in bank_fields_from_snapshots()
• Update log in rebuild_bank_from_snapshots()
• Refactor regular expressions in get_snapshot_file_kind()
• Making get_snapshot_file_kind() public and thus making SnapshotFileKind public
• Adding debug log in validator::main()

This is quite a list! And it's a testament to how much work you've already put into this feature, @xiangzhu70. I do think it'll be beneficial to have smaller PRs. Ideally the PR's title is a single tangible thing that the PR implements/changes vs a collection of non-essential "helper" changes.

Hopefully many of the debugging/logging changes probably would go in with another PR that uses those new logs. Each distinct code refactoring would benefit from its own PR; this makes it easier to review and really know what is and isn't getting updated.

I imagine this may feel like a lot of extra work; that's how I felt when I started on this codebase as well. What I've found is that over time these smaller PRs are much faster. Reviews get done much faster, far fewer bugs get introduced, and writing out PR descriptions helps me think through the intent of the PR as well (and then the reviewers get that context too!).

I imagine this may feel like a lot of extra work; that's how I felt when I started on this codebase as well. What I've found is that over time these smaller PRs are much faster. Reviews get done much faster, far fewer bugs get introduced, and writing out PR descriptions helps me think through the intent of the PR as well (and then the reviewers get that context too!).

I second the thought that several smaller PRs is easier to review and generally will go faster overall 😄
It additionally has the benefit of making introduced bugs easier to track down the exact breaking change using git bisect
I was split on pushing this here, but with @brooksprumo also expressing this I think it makes sense to split it out.

For the essential major changes, splitting helps isolate the impact of potential problems for bisecting. This PR only has misc logging/helper logic which have no impact to the existing behaviors, is meant to reduce the size of the essential PRs. I thought it should be safe. OK, I will split it further. It indeed will take quite much work. I will separate them by functionality and generate different PRs. Closing this PR now.