[libvirt] [PATCH v2 1/6] block/dirty-bitmap: add recording and busy properties

[Vladimir Sementsov-Ogievskiy]

14.02.2019 2:23, John Snow wrote:
> The current API allows us to report a single status, which we've defined as:
> 
> Frozen: has a successor, treated as qmp_locked, may or may not be enabled.
> Locked: no successor, qmp_locked. may or may not be enabled.
> Disabled: Not frozen or locked, disabled.
> Active: Not frozen, locked, or disabled.
> 
> The problem is that both "Frozen" and "Locked" mean nearly the same thing,
> and that both of them do not intuit whether they are recording guest writes
> or not.
> 
> This patch deprecates that status field and introduces two orthogonal
> properties instead to replace it.
> 
> Signed-off-by: John Snow <jsnow at redhat.com>
> ---
>   block/dirty-bitmap.c       |  9 +++++++++
>   qapi/block-core.json       | 10 +++++++++-
>   qemu-deprecated.texi       |  6 ++++++
>   tests/qemu-iotests/236.out | 28 ++++++++++++++++++++++++++++
>   4 files changed, 52 insertions(+), 1 deletion(-)
> 
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index c6d4acebfa..101383b3af 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -226,6 +226,13 @@ DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap)
>       }
>   }
>   
> +/* Called with BQL taken.  */
> +static bool bdrv_dirty_bitmap_recording(BdrvDirtyBitmap *bitmap)
> +{
> +    return !bitmap->disabled || (bitmap->successor &&
> +                                 !bitmap->successor->disabled);
> +}
> +
>   /**
>    * Create a successor bitmap destined to replace this bitmap after an operation.
>    * Requires that the bitmap is not frozen and has no successor.
> @@ -448,6 +455,8 @@ BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs)
>           info->has_name = !!bm->name;
>           info->name = g_strdup(bm->name);
>           info->status = bdrv_dirty_bitmap_status(bm);
> +        info->recording = bdrv_dirty_bitmap_recording(bm);
> +        info->busy = bdrv_dirty_bitmap_user_locked(bm);
>           info->persistent = bm->persistent;
>           entry->value = info;
>           *plist = entry;
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 8f23f2ebb8..5d1d182447 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -458,7 +458,14 @@
>   #
>   # @granularity: granularity of the dirty bitmap in bytes (since 1.4)
>   #
> -# @status: current status of the dirty bitmap (since 2.4)
> +# @status: Deprecated in favor of @recording and @locked. (since 2.4)
> +#
> +# @recording: true if the bitmap is recording new writes from the guest.
> +#             Replaces `active` and `disabled` statuses. (since 4.0)
> +#
> +# @busy: true if the bitmap is in-use by some operation (NBD or jobs)
> +#        and cannot be modified via QMP or used by another operation.
> +#        Replaces `locked` and `frozen` statuses. (since 4.0)
>   #
>   # @persistent: true if the bitmap will eventually be flushed to persistent
>   #              storage (since 4.0)
> @@ -467,6 +474,7 @@
>   ##
>   { 'struct': 'BlockDirtyInfo',
>     'data': {'*name': 'str', 'count': 'int', 'granularity': 'uint32',
> +           'recording': 'bool', 'busy': 'bool',
>              'status': 'DirtyBitmapStatus', 'persistent': 'bool' } }
>   
>   ##
> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> index 80b0702ad5..f7c9f4c101 100644
> --- a/qemu-deprecated.texi
> +++ b/qemu-deprecated.texi
> @@ -84,6 +84,12 @@ topologies described with -smp include all possible cpus, i.e.
>   "autoload" parameter is now ignored. All bitmaps are automatically loaded
>   from qcow2 images.
>   
> + at subsection query-block dirty-bitmaps.status parameter (since 4.0)

It is not a parameter. It's a field of result structure..

maybe
@subsection query-block result field 'dirty-bitmaps[i].status' (since 4.0)


with or without it:
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov at virtuozzo.com>

> +
> +The ``status'' field of the ``BlockDirtyInfo'' structure, returned by
> +the query-block command is deprecated. Two new boolean fields,
> +``recording'' and ``busy'' effectively replace it.

Hm, preexisting, but do we have some good alternative to `` '' pair? Maybe a kind
of @var{} or something?

> +
>   @subsection query-cpus (since 2.12.0)
>   
>   The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command.





-- 
Best regards,
Vladimir