On Mon, 01/22 23:08, Max Reitz wrote:
> @@ -1151,7 +1285,48 @@ static int coroutine_fn
> bdrv_mirror_top_preadv(BlockDriverState *bs,
> static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
> uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
> {
> - return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
> + MirrorOp *op = NULL;
> + MirrorBDSOpaque *s = bs->opaque;
> + QEMUIOVector bounce_qiov;
> + void *bounce_buf;
> + int ret = 0;
> + bool copy_to_target;
> +
> + copy_to_target = s->job->ret >= 0 &&
> + s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
> +
> + if (copy_to_target) {
> + /* The guest might concurrently modify the data to write; but
> + * the data on source and destination must match, so we have
> + * to use a bounce buffer if we are going to write to the
> + * target now. */
> + bounce_buf = qemu_blockalign(bs, bytes);
> + iov_to_buf_full(qiov->iov, qiov->niov, 0, bounce_buf, bytes);
Quorum doesn't use a bounce buffer, so I think we can get away without it too: a
guest concurrently modifying the buffer isn't a concern in practice.
> +
> + qemu_iovec_init(&bounce_qiov, 1);
> + qemu_iovec_add(&bounce_qiov, bounce_buf, bytes);
> + qiov = &bounce_qiov;
> +
> + op = active_write_prepare(s->job, offset, bytes);
> + }
> +
> + ret = bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
> + if (ret < 0) {
> + goto out;
> + }
> +
> + if (copy_to_target) {
> + do_sync_target_write(s->job, offset, bytes, qiov, flags);
> + }
> +
> +out:
> + if (copy_to_target) {
> + active_write_settle(op);
> +
> + qemu_iovec_destroy(&bounce_qiov);
> + qemu_vfree(bounce_buf);
> + }
> + return ret;
> }
>
> static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
Don't you need to update bdrv_mirror_top_pdiscard and bdrv_mirror_top_pwritev
too?
Fam
