Open cache (--open-cache option) invalidation

[solracsf]

I have a mount where files properties (metadata and ctime, essentially) are read frequently.
To speed up things, i'm evaluating --open-cache option.

Since this is a single mount/client, can i enable --open-cache with a high number (like 7200s) safely?
Is there any cache invalidation if cached file by the --open-cache option changes somehow (metadata, ctime)?

[SandyXSD]

Yes, it will invalidate the open-cache if a file is modified.

[solracsf]

Completed by #3335