Re: [Qemu-devel] [Qemu-block] [PATCH 5/6] block: Add QMP support for streaming to an intermediate layer

[Max Reitz <mreitz@redhat.com>]

On 08.04.2015 16:43, Alberto Garcia wrote:
> This patch makes the 'device' paramater of the 'block-stream' command
> allow a node name as well as a device name.

s/allow/accept/

> In addition to that, operation blockers will be checked in all
> intermediate nodes between the top and the base node.
>
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>   blockdev.c           | 20 ++++++++++----------
>   qapi/block-core.json | 10 +++++++---
>   2 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/blockdev.c b/blockdev.c
> index dc5d931..f24cf2d 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2104,8 +2104,7 @@ void qmp_block_stream(const char *device,
>                         bool has_on_error, BlockdevOnError on_error,
>                         Error **errp)
>   {
> -    BlockBackend *blk;
> -    BlockDriverState *bs;
> +    BlockDriverState *bs, *i;

Hmmmm... ;-)

Looks good otherwise.

Max

>       BlockDriverState *base_bs = NULL;
>       AioContext *aio_context;
>       Error *local_err = NULL;
> @@ -2115,20 +2114,14 @@ void qmp_block_stream(const char *device,
>           on_error = BLOCKDEV_ON_ERROR_REPORT;
>       }
>   
> -    blk = blk_by_name(device);
> -    if (!blk) {
> -        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> +    bs = bdrv_lookup_bs(device, device, errp);
> +    if (!bs) {
>           return;
>       }
> -    bs = blk_bs(blk);
>   
>       aio_context = bdrv_get_aio_context(bs);
>       aio_context_acquire(aio_context);
>   
> -    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_STREAM, errp)) {
> -        goto out;
> -    }
> -
>       if (has_base) {
>           base_bs = bdrv_find_backing_image(bs, base);
>           if (base_bs == NULL) {
> @@ -2139,6 +2132,13 @@ void qmp_block_stream(const char *device,
>           base_name = base;
>       }
>   
> +    /* Check for op blockers in the whole chain between bs and base */
> +    for (i = bs; i != NULL && i != base_bs; i = i->backing_hd) {
> +        if (bdrv_op_is_blocked(i, BLOCK_OP_TYPE_STREAM, errp)) {
> +            goto out;
> +        }
> +    }
> +
>       /* if we are streaming the entire chain, the result will have no backing
>        * file, and specifying one is therefore an error */
>       if (base_bs == NULL && has_backing_file) {
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 3639454..60b9664 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -1014,6 +1014,10 @@
>   # with query-block-jobs.  The operation can be stopped before it has completed
>   # using the block-job-cancel command.
>   #
> +# The node that receives the data is called the top image, can be located
> +# in any part of the whole chain and can be specified using its device
> +# or node name.
> +#
>   # If a base file is specified then sectors are not copied from that base file and
>   # its backing chain.  When streaming completes the image file will have the base
>   # file as its backing file.  This can be used to stream a subset of the backing
> @@ -1022,12 +1026,12 @@
>   # On successful completion the image file is updated to drop the backing file
>   # and the BLOCK_JOB_COMPLETED event is emitted.
>   #
> -# @device: the device name
> +# @device: the device or node name of the top image
>   #
>   # @base:   #optional the common backing file name
>   #
> -# @backing-file: #optional The backing file string to write into the active
> -#                          layer. This filename is not validated.
> +# @backing-file: #optional The backing file string to write into the top
> +#                          image. This filename is not validated.
>   #
>   #                          If a pathname string is such that it cannot be
>   #                          resolved by QEMU, that means that subsequent QMP or