fn wal_fsync_io_uring(ring: &mut IoUring, file: &File) -> Result<(), String>Expand description
Submit IORING_OP_FSYNC with DATASYNC flag via io_uring.
Only the fsync uses io_uring — writes go through regular BufWriter to page cache. io_uring FSYNC flushes page cache to storage without blocking the thread on a syscall (the kernel does the work asynchronously and we wait on the CQE).