Re: [PATCH v10 8/9] block: remove unused backing-file name parameter

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

29.09.2020 15:38, Andrey Shinkevich wrote:
> The block stream QMP parameter backing-file is in use no more. It
> designates a backing file name to set in QCOW2 image header after the
> block stream job finished. The base file name is used instead.
> 
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>

We can't just remove it without a deprecation period of three releases.

So actually, in a previous patch, we should implement new behavior for
automatic backing-file detection if this parameter is unspecified. Amd
keep old behavior for backing-file-name if it is given.

Hmm. Or, probably, we can use direct base for base-filename? And in cases
when we should skip filters (for example of parallel jobs) user should
specify backing-file explicitly?

> ---
>   block/monitor/block-hmp-cmds.c |  2 +-
>   block/stream.c                 |  6 +-----
>   blockdev.c                     | 17 +----------------
>   include/block/block_int.h      |  2 +-
>   qapi/block-core.json           | 17 +----------------
>   5 files changed, 5 insertions(+), 39 deletions(-)
> 
> diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
> index 4e66775..5f19499 100644
> --- a/block/monitor/block-hmp-cmds.c
> +++ b/block/monitor/block-hmp-cmds.c
> @@ -506,7 +506,7 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
>       int64_t speed = qdict_get_try_int(qdict, "speed", 0);
>   
>       qmp_block_stream(true, device, device, base != NULL, base, false, NULL,
> -                     false, NULL, qdict_haskey(qdict, "speed"), speed, true,
> +                     qdict_haskey(qdict, "speed"), speed, true,
>                        BLOCKDEV_ON_ERROR_REPORT, false, NULL, false, false, false,
>                        false, &error);
>   
> diff --git a/block/stream.c b/block/stream.c
> index b0719e9..fe2663f 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -34,7 +34,6 @@ typedef struct StreamBlockJob {
>       BlockDriverState *base_overlay; /* COW overlay (stream from this) */
>       BlockDriverState *above_base;   /* Node directly above the base */
>       BlockdevOnError on_error;
> -    char *backing_file_str;
>       bool bs_read_only;
>       bool chain_frozen;
>   } StreamBlockJob;
> @@ -103,8 +102,6 @@ static void stream_clean(Job *job)
>           blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
>           bdrv_reopen_set_read_only(bs, true, NULL);
>       }
> -
> -    g_free(s->backing_file_str);
>   }
>   
>   static int coroutine_fn stream_run(Job *job, Error **errp)
> @@ -220,7 +217,7 @@ static const BlockJobDriver stream_job_driver = {
>   };
>   
>   void stream_start(const char *job_id, BlockDriverState *bs,
> -                  BlockDriverState *base, const char *backing_file_str,
> +                  BlockDriverState *base,
>                     int creation_flags, int64_t speed,
>                     BlockdevOnError on_error,
>                     const char *filter_node_name,
> @@ -295,7 +292,6 @@ void stream_start(const char *job_id, BlockDriverState *bs,
>   
>       s->base_overlay = base_overlay;
>       s->above_base = above_base;
> -    s->backing_file_str = g_strdup(backing_file_str);
>       s->bs_read_only = bs_read_only;
>       s->chain_frozen = true;
>   
> diff --git a/blockdev.c b/blockdev.c
> index d719c47..b223601 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2486,7 +2486,6 @@ out:
>   void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>                         bool has_base, const char *base,
>                         bool has_base_node, const char *base_node,
> -                      bool has_backing_file, const char *backing_file,
>                         bool has_speed, int64_t speed,
>                         bool has_on_error, BlockdevOnError on_error,
>                         bool has_filter_node_name, const char *filter_node_name,
> @@ -2498,7 +2497,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>       BlockDriverState *base_bs = NULL;
>       AioContext *aio_context;
>       Error *local_err = NULL;
> -    const char *base_name = NULL;
>       int job_flags = JOB_DEFAULT;
>   
>       if (!has_on_error) {
> @@ -2526,7 +2524,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>               goto out;
>           }
>           assert(bdrv_get_aio_context(base_bs) == aio_context);
> -        base_name = base;
>       }
>   
>       if (has_base_node) {
> @@ -2541,7 +2538,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>           }
>           assert(bdrv_get_aio_context(base_bs) == aio_context);
>           bdrv_refresh_filename(base_bs);
> -        base_name = base_bs->filename;
>       }
>   
>       /* Check for op blockers in the whole chain between bs and base */
> @@ -2553,17 +2549,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>           }
>       }
>   
> -    /* 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) {
> -        error_setg(errp, "backing file specified, but streaming the "
> -                         "entire chain");
> -        goto out;
> -    }
> -
> -    /* backing_file string overrides base bs filename */
> -    base_name = has_backing_file ? backing_file : base_name;
> -
>       if (has_auto_finalize && !auto_finalize) {
>           job_flags |= JOB_MANUAL_FINALIZE;
>       }
> @@ -2571,7 +2556,7 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>           job_flags |= JOB_MANUAL_DISMISS;
>       }
>   
> -    stream_start(has_job_id ? job_id : NULL, bs, base_bs, base_name,
> +    stream_start(has_job_id ? job_id : NULL, bs, base_bs,
>                    job_flags, has_speed ? speed : 0, on_error,
>                    filter_node_name, &local_err);
>       if (local_err) {
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index f782737..bbe2ee6 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -1147,7 +1147,7 @@ int is_windows_drive(const char *filename);
>    * BlockDriverState.
>    */
>   void stream_start(const char *job_id, BlockDriverState *bs,
> -                  BlockDriverState *base, const char *backing_file_str,
> +                  BlockDriverState *base,
>                     int creation_flags, int64_t speed,
>                     BlockdevOnError on_error,
>                     const char *filter_node_name,
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 32fb097..6358606 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2512,21 +2512,6 @@
>   # @base-node: the node name of the backing file.
>   #             It cannot be set if @base is also set. (Since 2.8)
>   #
> -# @backing-file: 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
> -#                HMP commands must use node-names for the image in
> -#                question, as filename lookup methods will fail.
> -#
> -#                If not specified, QEMU will automatically determine
> -#                the backing file string to use, or error out if there
> -#                is no obvious choice.  Care should be taken when
> -#                specifying the string, to specify a valid filename or
> -#                protocol.
> -#                (Since 2.1)
> -#
>   # @speed: the maximum speed, in bytes per second
>   #
>   # @on-error: the action to take on an error (default report).
> @@ -2566,7 +2551,7 @@
>   ##
>   { 'command': 'block-stream',
>     'data': { '*job-id': 'str', 'device': 'str', '*base': 'str',
> -            '*base-node': 'str', '*backing-file': 'str', '*speed': 'int',
> +            '*base-node': 'str', '*speed': 'int',
>               '*on-error': 'BlockdevOnError',
>               '*filter-node-name': 'str',
>               '*auto-finalize': 'bool', '*auto-dismiss': 'bool' } }
> 


-- 
Best regards,
Vladimir