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

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

On 07.10.2020 13:21, Vladimir Sementsov-Ogievskiy wrote:
> 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.

It has not been in use for a long. It's time.

> 
> 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?

The backing_file_str is always specified if the base is specified and is 
always equal to the base->filename. So, the user's backing file name is 
always NULL for the stream job. Furthermore, it is not checked for being 
the correct backing node and can lead to a wrong record in the QCOW2 header.

Andrey

> 
>> ---
>>   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' } }
>>
> 
>