Re: [Qemu-devel] [PATCH v5 03/11] block: add basic backup support to block driver

[Fam Zheng <famz@redhat.com>]

> +static void coroutine_fn backup_run(void *opaque)
> +{
> +    BackupBlockJob *job = opaque;
> +    BlockDriverState *bs = job->common.bs;
> +    BlockDriverState *target = job->target;
> +    BlockdevOnError on_target_error = job->on_target_error;
> +    NotifierWithReturn before_write = {
> +        .notify = backup_before_write_notify,
> +    };
> +    int64_t start, end;
> +    int ret = 0;
> +
> +    QLIST_INIT(&job->inflight_reqs);
> +    qemu_co_rwlock_init(&job->flush_rwlock);
> +
> +    start = 0;
> +    end = DIV_ROUND_UP(bdrv_getlength(bs) / BDRV_SECTOR_SIZE,
> +                       BACKUP_SECTORS_PER_CLUSTER);
> +
> +    job->bitmap = hbitmap_alloc(end, 0);
> +
> +    bdrv_set_on_error(target, on_target_error, on_target_error);
> +    bdrv_iostatus_enable(target);
> +
> +    bdrv_add_before_write_notifier(bs, &before_write);
> +
> +    DPRINTF("backup_run start %s %" PRId64 " %" PRId64 "\n",
> +            bdrv_get_device_name(bs), start, end);
> +
> +    for (; start < end; start++) {
> +        bool error_is_read;
> +
> +        if (block_job_is_cancelled(&job->common)) {
> +            break;
> +        }
> +
> +        /* we need to yield so that qemu_aio_flush() returns.
> +         * (without, VM does not reboot)
> +         */
> +        if (job->common.speed) {
> +            uint64_t delay_ns = ratelimit_calculate_delay(
> +                &job->limit, job->sectors_read);
> +            job->sectors_read = 0;
> +            block_job_sleep_ns(&job->common, rt_clock, delay_ns);
> +        } else {
> +            block_job_sleep_ns(&job->common, rt_clock, 0);
> +        }
> +
> +        if (block_job_is_cancelled(&job->common)) {
> +            break;
> +        }
> +
> +        DPRINTF("backup_run loop C%" PRId64 "\n", start);
> +
> +        ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER, 1,
> +                            &error_is_read);
> +        if (ret < 0) {
> +            /* Depending on error action, fail now or retry cluster */
> +            BlockErrorAction action =
> +                backup_error_action(job, error_is_read, -ret);
> +            if (action == BDRV_ACTION_REPORT) {
> +                break;
> +            } else {
> +                start--;
> +                continue;
> +            }
> +        }
> +    }
> +
> +    notifier_with_return_remove(&before_write);
> +
> +    /* wait until pending backup_do_cow() calls have completed */
> +    qemu_co_rwlock_wrlock(&job->flush_rwlock);
> +    qemu_co_rwlock_unlock(&job->flush_rwlock);
> +
> +    hbitmap_free(job->bitmap);
> +
> +    bdrv_iostatus_disable(target);
> +    bdrv_delete(job->target);

drive-mirror has bdrv_close before deleting target, why don't we need
one here?

> +
> +    DPRINTF("backup_run complete %d\n", ret);
> +    block_job_completed(&job->common, ret);
> +}
> +


Fam