[crac] RFR: Handle open file descriptors with configurable policies [v3]

[Radim Vansa]

On Fri, 9 Jun 2023 15:22:34 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> This handling is meant for read-only access, too.
>> I don't think that the concept of 'appending' makes sense from CRaC POV - the append flag just says whether you've started at the beginning or at the end; but this aims at transparent continuation of what you were doing as if no checkpoint happened.
>
> I don't completely follow. Consider an example of a log file in append write mode (every write guaranteed to append to file, even with concurrent writes). As for me, it's perfectly fine to restore with that log, even with different offset, since offset does not make a lot of sense with append mode.

What I was trying to say that it's not about reading the 'append' flag when the file was opened, because that was just saying "let's open and then seek to the end of the file". We shouldn't conclude that we want to start at the 'new end' (provided that the file was modified) on restore.
Having a policy that will reopen at end, regardless of original offset, is certainly a valid option.

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PR Review Comment: https://git.openjdk.org/crac/pull/69#discussion_r1224466586