[v7,09/11] Dump: add qmp command "query-dump"

When dump-guest-memory is requested with detach flag, after its
return, user could query its status using "query-dump" command (with
no argument). The result contains:

- status: current dump status
- completed: bytes written in the latest dump
- total: bytes to write in the latest dump

From completed and total, we could know how much work
finished by calculating:

  100.0 * completed / total (%)

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 dump.c           | 23 +++++++++++++++++++----
 qapi-schema.json | 32 +++++++++++++++++++++++++++++++-
 qmp-commands.hx  | 27 ++++++++++++++++++++++++++-
 3 files changed, 76 insertions(+), 6 deletions(-)

On Tue, 02/16 15:50, Peter Xu wrote:
> When dump-guest-memory is requested with detach flag, after its
> return, user could query its status using "query-dump" command (with
> no argument). The result contains:
> 
> - status: current dump status
> - completed: bytes written in the latest dump
> - total: bytes to write in the latest dump
> 
> From completed and total, we could know how much work
> finished by calculating:
> 
>   100.0 * completed / total (%)
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  dump.c           | 23 +++++++++++++++++++----
>  qapi-schema.json | 32 +++++++++++++++++++++++++++++++-
>  qmp-commands.hx  | 27 ++++++++++++++++++++++++++-
>  3 files changed, 76 insertions(+), 6 deletions(-)
> 
> diff --git a/dump.c b/dump.c
> index ca2400d..c697259 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -1456,7 +1456,7 @@ static void dump_state_prepare(DumpState *s)
>  bool dump_in_progress(void)
>  {
>      DumpState *state = &dump_state_global;
> -    return (state->status == DUMP_STATUS_ACTIVE);
> +    return (atomic_read(&state->status) == DUMP_STATUS_ACTIVE);
>  }
>  
>  /* calculate total size of memory to be dumped (taking filter into
> @@ -1669,9 +1669,12 @@ static void dump_process(DumpState *s, Error **errp)
>          create_vmcore(s, &local_err);
>      }
>  
> -    s->status = (local_err ? DUMP_STATUS_FAILED : DUMP_STATUS_COMPLETED);
> -    error_propagate(errp, local_err);
> +    /* make sure status is written after written_size updates */
> +    smp_wmb();
> +    atomic_set(&s->status,
> +               (local_err ? DUMP_STATUS_FAILED : DUMP_STATUS_COMPLETED));
>  
> +    error_propagate(errp, local_err);
>      dump_cleanup(s);
>  }
>  
> @@ -1689,6 +1692,18 @@ static void *dump_thread(void *data)
>      return NULL;
>  }
>  
> +DumpQueryResult *qmp_query_dump(Error **errp)
> +{
> +    DumpQueryResult *result = g_new(DumpQueryResult, 1);
> +    DumpState *state = &dump_state_global;
> +    result->status = atomic_read(&state->status);
> +    /* make sure we are reading status and written_size in order */
> +    smp_rmb();
> +    result->completed = state->written_size;
> +    result->total = state->total_size;
> +    return result;
> +}
> +
>  void qmp_dump_guest_memory(bool paging, const char *file,
>                             bool has_detach, bool detach,
>                             bool has_begin, int64_t begin, bool has_length,
> @@ -1779,7 +1794,7 @@ void qmp_dump_guest_memory(bool paging, const char *file,
>                begin, length, &local_err);
>      if (local_err) {
>          error_propagate(errp, local_err);
> -        s->status = DUMP_STATUS_FAILED;
> +        atomic_set(&s->status, DUMP_STATUS_FAILED);
>          return;
>      }
>  
> diff --git a/qapi-schema.json b/qapi-schema.json
> index ccd30c8..7b8f2a1 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2196,7 +2196,8 @@
>  #               is the fd's name.
>  #
>  # @detach: #optional if true, QMP will return immediately rather than
> -#          waiting for the dump to finish. (since 2.6).
> +#          waiting for the dump to finish. The user can track progress
> +#          using "query-dump". (since 2.6).
>  #
>  # @begin: #optional if specified, the starting physical address.
>  #
> @@ -2237,6 +2238,35 @@
>    'data': [ 'none', 'active', 'completed', 'failed' ] }
>  
>  ##
> +# @DumpQueryResult
> +#
> +# The result format for 'query-dump'.
> +#
> +# @status: enum of @DumpStatus, which shows current dump status
> +#
> +# @completed: bytes written in latest dump (uncompressed)
> +#
> +# @total: total bytes to be written in latest dump (uncompressed)
> +#
> +# Since 2.6
> +##
> +{ 'struct': 'DumpQueryResult',
> +  'data': { 'status': 'DumpStatus',
> +            'completed': 'int',
> +            'total': 'int' } }
> +
> +##
> +# @query-dump
> +#
> +# Query latest dump status.
> +#
> +# Returns: A @DumpStatus object showing the dump status.
> +#
> +# Since: 2.6
> +##
> +{ 'command': 'query-dump', 'returns': 'DumpQueryResult' }
> +
> +##
>  # @DumpGuestMemoryCapability:
>  #
>  # A list of the available formats for dump-guest-memory
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 5dc7738..47351f3 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -856,7 +856,8 @@ Arguments:
>  - "protocol": destination file(started with "file:") or destination file
>                descriptor (started with "fd:") (json-string)
>  - "detach": if specified, command will return immediately, without waiting
> -            for the dump to finish (json-bool)
> +            for the dump to finish. The user can track progress using
> +            "query-dump". (json-bool)
>  - "begin": the starting physical address. It's optional, and should be specified
>             with length together (json-int)
>  - "length": the memory size, in bytes. It's optional, and should be specified
> @@ -896,6 +897,30 @@ Example:
>  
>  EQMP
>  
> +    {
> +        .name       = "query-dump",
> +        .args_type  = "",
> +        .params     = "",
> +        .help       = "query background dump status",
> +        .mhandler.cmd_new = qmp_marshal_query_dump,
> +    },
> +
> +SQMP
> +query-dump
> +----------
> +
> +Query background dump status.
> +
> +Arguments: None.
> +
> +Example:
> +
> +-> { "execute": "query-dump" }
> +<- { "return": { "status": "active", "completed": 1024000,
> +                 "total": 2048000 } }
> +
> +EQMP
> +
>  #if defined TARGET_S390X
>      {
>          .name       = "dump-skeys",
> -- 
> 2.4.3
> 

Reviewed-by: Fam Zheng <famz@redhat.com>