On 24/04/2015 13:00, Paolo Bonzini wrote:
>> - qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
>> - qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
>> - use_local_qiov = true;
>> + if (qiov) {
>> + qemu_iovec_init(&local_qiov, qiov ? qiov->niov + 2 : 1);
>> + qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
>> + qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
>> + use_local_qiov = true;
>> + bytes += offset & (align - 1);
>> + offset = offset & ~(align - 1);
>> + } else {
>> + memset(head_buf + (offset & (align - 1)), 0,
>> + align - (offset & (align - 1)));
Actually, is the byte count correct if bytes < align? In the case of
your testcase, you'd destroy bytes 1536..4095.
Same for the computation of bytes, below. It could underflow.
Perhaps a qemu-iotests testcase, using qemu-io, is also necessary.
Paolo
>> + ret = bdrv_aligned_pwritev(bs, &req, offset & ~(align - 1),
>> align,
>> + &head_qiov, 0);
>> + if (ret < 0) {
>> + goto fail;
>> + }
>> + bytes -= align - (offset & (align - 1));
>> + offset = ROUND_UP(offset, align);
>> + }
>> + }
