Method execute_async

block/src/request.rs:237–503

(
        &mut self,
        mem: &vm_memory::GuestMemoryMmap<B>,
        disk_nsectors: u64,
        disk_image: &mut dyn AsyncIo,
        serial: &[u8],
        disable_sector0_writes: bool,
       

    }

    pub fn execute_async<B: Bitmap + 'static>(
        &mut self,
        mem: &vm_memory::GuestMemoryMmap<B>,
        disk_nsectors: u64,
        disk_image: &mut dyn AsyncIo,
        serial: &[u8],
        disable_sector0_writes: bool,
        user_data: u64,
    ) -> Result<ExecuteAsync, ExecuteError> {
        let sector = self.sector;
        let request_type = self.request_type;
        let offset = (sector << SECTOR_SHIFT) as libc::off_t;
        let alignment = disk_image.alignment();

        self.check_data_bounds(disk_nsectors)?;

        let mut iovecs: SmallVec<[libc::iovec; DEFAULT_DESCRIPTOR_VEC_SIZE]> =
            SmallVec::with_capacity(self.data_descriptors.len());
        for &(data_addr, data_len) in &self.data_descriptors {
            let _: u32 = data_len; // compiler-checked documentation
            const _: () = assert!(
                core::mem::size_of::<u32>() <= core::mem::size_of::<usize>(),
                "unsupported platform"
            );
            if data_len == 0 {
                continue;
            }
            let data_len = data_len as usize;

            let origin_ptr = mem
                .get_slice(data_addr, data_len)
                .map_err(ExecuteError::GetHostAddress)?;
            assert!(origin_ptr.len() >= data_len);
            let origin_ptr = origin_ptr.ptr_guard_mut();

            // O_DIRECT requires buffer addresses to be aligned to the
            // backend device's logical block size. In case it's not properly
            // aligned, an intermediate buffer is created with the correct
            // alignment, and a copy from/to the origin buffer is performed,
            // depending on the type of operation.
            let iov_base = if (origin_ptr.as_ptr() as u64).is_multiple_of(alignment) {
                origin_ptr.as_ptr().cast()
            } else {
                let mut aligned_op = AlignedOperation::new(data_addr, data_len, alignment as usize)
                    .map_err(ExecuteError::TemporaryBufferAllocation)?;

                // We need to perform the copy beforehand in case we're writing
                // data out.
                if request_type == RequestType::Out {
                    mem.read_slice(aligned_op.as_bytes_mut(), data_addr)
                        .map_err(ExecuteError::Read)?;
                }

                let aligned_ptr = aligned_op.as_mut_ptr();
                self.aligned_operations.push(aligned_op);

                aligned_ptr.cast()
            };