Function write_and_verify 

pub fn write_and_verify<D: Device + ?Sized>(
    dev: &mut D,
    offset: u64,
    buf: &[u8],
) -> Result<()>

Write buf at offset, then re-read and verify byte-equal. Returns Error::VerifyMismatch on the first divergence.

This is the “verify-by-default” primitive. Callers that legitimately want to skip verification (e.g. mid-pipeline writes that will be re-checked holistically later) call write_at directly.