error: non-binding let on a synchronization lock

[tjni]

Due to a new lint in rust 1.65 introduced by rust-lang/rust#97739, there is a new compilation error:

error: non-binding let on a synchronization lock
   --> src/catfs/file.rs:570:13
    |
570 |         let _ = self.page_in_res.0.lock().unwrap();
    |             ^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this binding will immediately drop the value assigned to it
    |             |
    |             this lock is not assigned to a binding and is immediately dropped
    |
    = note: `#[deny(let_underscore_lock)]` on by default
help: consider binding to an unused variable to avoid immediately dropping the value
    |
570 |         let _unused = self.page_in_res.0.lock().unwrap();
    |             ~~~~~~~
help: consider immediately dropping the value
    |
570 |         drop(self.page_in_res.0.lock().unwrap());
    |         ~~~~~                                  +

(Ignore the line numbers as they correspond to an older version, but I was able to verify it still occurs in v0.9.0 and the code triggering the error still exists.)

I was planning to fix this, but I can't figure out what the purpose of that line is. Is this mutex being used to gate access to more things than its internal data?

[gaul]

Resolved by 322b087.