Re: [Qemu-devel] [Qemu-block] [PATCH 04/14] block/create: Make x-blockdev-create a job

[Jeff Cody <jcody@redhat.com>]

On Fri, May 25, 2018 at 06:33:17PM +0200, Kevin Wolf wrote:
> This changes the x-blockdev-create QMP command so that it doesn't block
> the monitor and the main loop any more, but starts a background job that
> performs the image creation.
> 

This comes down to "user error", but now that the monitor and main loop are
not blocked (which is good), should we try at all to catch/prevent a
blockdev-add that is issued before a blockdev-create completion?

> The basic job as implemented here is all that is necessary to make image
> creation asynchronous and to provide a QMP interface that can be marked
> stable, but it still lacks a few features that jobs usually provide: The
> job will ignore pause commands and it doesn't publish progress yet (so
> both current-progress and total-progress stay at 0). These features can
> be added later without breaking compatibility.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  qapi/block-core.json     | 14 +++++++----
>  qapi/job.json            |  4 +++-
>  block/create.c           | 61 ++++++++++++++++++++++++++++++++----------------
>  tests/qemu-iotests/group | 14 ++++++-----
>  4 files changed, 61 insertions(+), 32 deletions(-)
> 
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 7dfa77a05c..1ed3a82373 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -4013,14 +4013,18 @@
>  ##
>  # @x-blockdev-create:
>  #
> -# Create an image format on a given node.
> -# TODO Replace with something asynchronous (block job?)
> +# Starts a job to create an image format on a given node. The job is
> +# automatically finalized, but a manual job-dismiss is required.
>  #
> -# Since: 2.12
> +# @job-id:          Identifier for the newly created job.
> +#
> +# @options:         Options for the image creation.
> +#
> +# Since: 3.0
>  ##
>  { 'command': 'x-blockdev-create',
> -  'data': 'BlockdevCreateOptions',
> -  'boxed': true }
> +  'data': { 'job-id': 'str',
> +            'options': 'BlockdevCreateOptions' } }
>  
>  ##
>  # @blockdev-open-tray:
> diff --git a/qapi/job.json b/qapi/job.json
> index 970124de76..69c1970a58 100644
> --- a/qapi/job.json
> +++ b/qapi/job.json
> @@ -17,10 +17,12 @@
>  #
>  # @backup: drive backup job type, see "drive-backup"
>  #
> +# @create: image creation job type, see "x-blockdev-create" (since 3.0)
> +#
>  # Since: 1.7
>  ##
>  { 'enum': 'JobType',
> -  'data': ['commit', 'stream', 'mirror', 'backup'] }
> +  'data': ['commit', 'stream', 'mirror', 'backup', 'create'] }
>  
>  ##
>  # @JobStatus:
> diff --git a/block/create.c b/block/create.c
> index 8bd8a03719..87fdab3b72 100644
> --- a/block/create.c
> +++ b/block/create.c
> @@ -24,28 +24,49 @@
>  
>  #include "qemu/osdep.h"
>  #include "block/block_int.h"
> +#include "qemu/job.h"
>  #include "qapi/qapi-commands-block-core.h"
> +#include "qapi/qapi-visit-block-core.h"
> +#include "qapi/clone-visitor.h"
>  #include "qapi/error.h"
>  
> -typedef struct BlockdevCreateCo {
> +typedef struct BlockdevCreateJob {
> +    Job common;
>      BlockDriver *drv;
>      BlockdevCreateOptions *opts;
>      int ret;
> -    Error **errp;
> -} BlockdevCreateCo;
> +    Error *err;
> +} BlockdevCreateJob;
>  
> -static void coroutine_fn bdrv_co_create_co_entry(void *opaque)
> +static void blockdev_create_complete(Job *job, void *opaque)
>  {
> -    BlockdevCreateCo *cco = opaque;
> -    cco->ret = cco->drv->bdrv_co_create(cco->opts, cco->errp);
> +    BlockdevCreateJob *s = container_of(job, BlockdevCreateJob, common);
> +
> +    job_completed(job, s->ret, s->err);
>  }
>  
> -void qmp_x_blockdev_create(BlockdevCreateOptions *options, Error **errp)
> +static void coroutine_fn blockdev_create_run(void *opaque)
>  {
> +    BlockdevCreateJob *s = opaque;
> +
> +    s->ret = s->drv->bdrv_co_create(s->opts, &s->err);
> +
> +    qapi_free_BlockdevCreateOptions(s->opts);
> +    job_defer_to_main_loop(&s->common, blockdev_create_complete, NULL);
> +}
> +
> +static const JobDriver blockdev_create_job_driver = {
> +    .instance_size = sizeof(BlockdevCreateJob),
> +    .job_type      = JOB_TYPE_CREATE,
> +    .start         = blockdev_create_run,
> +};
> +
> +void qmp_x_blockdev_create(const char *job_id, BlockdevCreateOptions *options,
> +                           Error **errp)
> +{
> +    BlockdevCreateJob *s;
>      const char *fmt = BlockdevDriver_str(options->driver);
>      BlockDriver *drv = bdrv_find_format(fmt);
> -    Coroutine *co;
> -    BlockdevCreateCo cco;
>  
>      /* If the driver is in the schema, we know that it exists. But it may not
>       * be whitelisted. */
> @@ -61,16 +82,16 @@ void qmp_x_blockdev_create(BlockdevCreateOptions *options, Error **errp)
>          return;
>      }
>  
> -    cco = (BlockdevCreateCo) {
> -        .drv = drv,
> -        .opts = options,
> -        .ret = -EINPROGRESS,
> -        .errp = errp,
> -    };
> -
> -    co = qemu_coroutine_create(bdrv_co_create_co_entry, &cco);
> -    qemu_coroutine_enter(co);
> -    while (cco.ret == -EINPROGRESS) {
> -        aio_poll(qemu_get_aio_context(), true);
> +    /* Create the block job */
> +    s = job_create(job_id, &blockdev_create_job_driver, NULL,
> +                   qemu_get_aio_context(), JOB_DEFAULT | JOB_MANUAL_DISMISS,
> +                   NULL, NULL, errp);
> +    if (!s) {
> +        return;
>      }
> +
> +    s->drv = drv,
> +    s->opts = QAPI_CLONE(BlockdevCreateOptions, options),
> +
> +    job_start(&s->common);
>  }
> diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
> index 93f93d71ba..22b0082db3 100644
> --- a/tests/qemu-iotests/group
> +++ b/tests/qemu-iotests/group
> @@ -204,14 +204,16 @@
>  203 rw auto migration
>  204 rw auto quick
>  205 rw auto quick
> -206 rw auto
> -207 rw auto
> +# TODO The following commented out tests need to be reworked to work
> +# with the x-blockdev-create job
> +#206 rw auto
> +#207 rw auto
>  208 rw auto quick
>  209 rw auto quick
> -210 rw auto
> -211 rw auto quick
> -212 rw auto quick
> -213 rw auto quick
> +#210 rw auto
> +#211 rw auto quick
> +#212 rw auto quick
> +#213 rw auto quick
>  214 rw auto
>  215 rw auto quick
>  216 rw auto quick
> -- 
> 2.13.6
> 
>