[LU-10999] Use readdir cache for lookup when available

Related — Tue, 5 Dec 2023 21:25:15 +0000

It looks like when we have a fully (and even not so fully?) populated readdir cache under update lock on the client, we could be using that for lookup.

Obvious benefit is ability to have negative lookups without any RPCs. Benefits for positive lookups are a bit less certain since even for things like unlinks the permission check would need more data (if we don't yet have the inode cached), though potentially we can still use that with better performance.

Whamcloud Community JIRA

[LU-10999] Use readdir cache for lookup when available