Re: [Qemu-devel] [PATCH alt 1/7] block: Add status callback to bdrv_amend_options()

[Max Reitz <mreitz@redhat.com>]

On 31.07.2014 09:51, Benoît Canet wrote:
> The Saturday 26 Jul 2014 à 21:22:05 (+0200), Max Reitz wrote :
>
>> Depending on the changed options and the image format,
>> bdrv_amend_options() may take a significant amount of time. In these
>> cases, a way to be informed about the operation's status is desirable.
>>
>> Since the operation is rather complex and may fundamentally change the
>> image, implementing it as AIO or a couroutine does not seem feasible. On
>> the other hand, implementing it as a block job would be significantly
>> more difficult than a simple callback and would not add benefits other
>> than progress report to the amending operation, because it should not
>> actually be run as a block job at all.
>>
>> A callback may not be very pretty, but it's very easy to implement and
>> perfectly fits its purpose here.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   block.c                   | 5 +++--
>>   block/qcow2.c             | 5 ++++-
>>   include/block/block.h     | 5 ++++-
>>   include/block/block_int.h | 3 ++-
>>   qemu-img.c                | 2 +-
>>   5 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/block.c b/block.c
>> index 3e252a2..4c8d4d8 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -5708,12 +5708,13 @@ void bdrv_add_before_write_notifier(BlockDriverState *bs,
>>       notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
>>   }
>>   
>> -int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts)
>> +int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
>> +                       BlockDriverAmendStatusCB *status_cb)
>>   {
>>       if (!bs->drv->bdrv_amend_options) {
>>           return -ENOTSUP;
>>       }
>> -    return bs->drv->bdrv_amend_options(bs, opts);
>> +    return bs->drv->bdrv_amend_options(bs, opts, status_cb);
>>   }
>>   
>>   /* This function will be called by the bdrv_recurse_is_first_non_filter method
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index b0faa69..757f890 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -2210,7 +2210,8 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version)
>>       return 0;
>>   }
>>   
>> -static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
>> +static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
>> +                               BlockDriverAmendStatusCB *status_cb)
>>   {
>>       BDRVQcowState *s = bs->opaque;
>>       int old_version = s->qcow_version, new_version = old_version;
>> @@ -2223,6 +2224,8 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
>>       int ret;
>>       QemuOptDesc *desc = opts->list->desc;
>>   
>> +    (void)status_cb;
> This look like a temporary hack to please the compiler.
> Am I right ? Should be comment this ?

It's removed in one of the next patches anyway; but I'll add a comment 
in v2.

Max

>> +
>>       while (desc && desc->name) {
>>           if (!qemu_opt_find(opts, desc->name)) {
>>               /* only change explicitly defined options */
>> diff --git a/include/block/block.h b/include/block/block.h
>> index 32d3676..f2b1799 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -309,7 +309,10 @@ typedef enum {
>>   
>>   int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix);
>>   
>> -int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts);
>> +typedef void BlockDriverAmendStatusCB(BlockDriverState *bs, int64_t offset,
>> +                                      int64_t total_work_size);
>> +int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts,
>> +                       BlockDriverAmendStatusCB *status_cb);
>>   
>>   /* external snapshots */
>>   bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>> index f6c3bef..5c5798d 100644
>> --- a/include/block/block_int.h
>> +++ b/include/block/block_int.h
>> @@ -228,7 +228,8 @@ struct BlockDriver {
>>       int (*bdrv_check)(BlockDriverState* bs, BdrvCheckResult *result,
>>           BdrvCheckMode fix);
>>   
>> -    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts);
>> +    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts,
>> +                              BlockDriverAmendStatusCB *status_cb);
>>   
>>       void (*bdrv_debug_event)(BlockDriverState *bs, BlkDebugEvent event);
>>   
>> diff --git a/qemu-img.c b/qemu-img.c
>> index ef74ae4..90d6b79 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -2827,7 +2827,7 @@ static int img_amend(int argc, char **argv)
>>           goto out;
>>       }
>>   
>> -    ret = bdrv_amend_options(bs, opts);
>> +    ret = bdrv_amend_options(bs, opts, NULL);
>>       if (ret < 0) {
>>           error_report("Error while amending options: %s", strerror(-ret));
>>           goto out;
>> -- 
>> 2.0.3
>>
>>