selinux: fix xattr and remove anyhow

[Gekko0114]

Fixed several points based on the feedback I received.
#2718

1. This PR updates the logic of xattr.
   If a file already has an xattr label, the REPLACE method is used.
   If a file doesn't have an xattr label, the CREATE method is used.

2. This PR removes anyhow from selinux.

[Gekko0114]

Hi @YJDoc2 @utam0k
I've fixed selinux lib based on feedback from @YJDoc2 #2718 (comment)
Could you review it?

[YJDoc2]

Hey overall good, a couple of suggestions in the code, with two questions here -

1. Please run clippy on local and check that all lints are passing, currently that is not getting verified in CI.
2. I saw that for EINTR, we are returning it as-is to caller. If my understanding is correct EINTR indicates that syscall was interrupted and there might not be any actual error. In which case should we retry? in a loop? I think we had this discussion before somewhere, what was decided from that?

Apart from this, lgtm 👍

[Gekko0114]

Thanks @YJDoc2,

Please run clippy on local and check that all lints are passing, currently that is not getting verified in CI.

Sure, I ran clippy. BTW, why not introduing clippy in CI ?

I saw that for EINTR, we are returning it as-is to caller. If my understanding is correct EINTR indicates that syscall was interrupted and there might not be any actual error. In which case should we retry? in a loop? I think we had this discussion before somewhere, what was decided from that?

Though we didn't discuss it in great depth, we talked about this topic.
#2850 (comment)
In the xattr function, a loop is not used, but a loop is used in the label function that calls xattr.
https://github.com/Gekko0114/youki/blob/main/experiment/selinux/src/selinux_label.rs#L75
Does this answer your question?

[YJDoc2]

why not introduing clippy in CI ?

Clippy is in CI, but we have intentionally excluded experimental crates from cargo workspace because of which clippy does not run on those crates.

Does this answer your question?

Yep, that's exactly what I was looking for. In this case, ok we are handling it correctly.

[YJDoc2]

Thanks!

[YJDoc2]

I re-labeled this to experimental, as we have still kept the crate in experimental. Once we move this and start using it in youki, that PR should be marked as feature.