Re: [Qemu-devel] [Qemu-block] [PATCH v5 1/4] Add new block driver interface to add/delete a BDS's child

[Wen Congyang]

On 10/08/2015 02:33 AM, Max Reitz wrote:
> On 22.09.2015 09:44, Wen Congyang wrote:
>> In some cases, we want to take a quorum child offline, and take
>> another child online.
>>
>> Signed-off-by: Wen Congyang <address@hidden>
>> Signed-off-by: zhanghailiang <address@hidden>
>> Signed-off-by: Gonglei <address@hidden>
>> Reviewed-by: Eric Blake <address@hidden>
>> ---
>>  block.c                   | 50 
>> +++++++++++++++++++++++++++++++++++++++++++++++
>>  include/block/block.h     |  5 +++++
>>  include/block/block_int.h |  5 +++++
>>  3 files changed, 60 insertions(+)
>>
>> diff --git a/block.c b/block.c
>> index e815d73..1b25e43 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -4265,3 +4265,53 @@ BlockAcctStats *bdrv_get_stats(BlockDriverState *bs)
>>  {
>>      return &bs->stats;
>>  }
>> +
>> +/*
>> + * Hot add/remove a BDS's child. So the user can take a child offline when
>> + * it is broken and take a new child online
>> + */
>> +void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
>> +                    Error **errp)
>> +{
>> +
>> +    if (!parent_bs->drv || !parent_bs->drv->bdrv_add_child) {
>> +        error_setg(errp, "The BDS %s doesn't support adding a child",
>> +                   bdrv_get_device_or_node_name(parent_bs));
>> +        return;
>> +    }
>> +
>> +    if (!QLIST_EMPTY(&child_bs->parents)) {
>> +        error_setg(errp, "The BDS %s already has parent",
>> +                   child_bs->node_name);
>> +        return;
>> +    }
>> +
>> +    parent_bs->drv->bdrv_add_child(parent_bs, child_bs, errp);
>> +}
>> +
>> +void bdrv_del_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
>> +                    Error **errp)
>> +{
>> +    BdrvChild *child;
>> +
>> +    if (!parent_bs->drv || !parent_bs->drv->bdrv_del_child) {
>> +        error_setg(errp, "The BDS %s doesn't support removing a child",
>> +                   bdrv_get_device_or_node_name(parent_bs));
>> +        return;
>> +    }
>> +
>> +    QLIST_FOREACH(child, &parent_bs->children, next) {
>> +        if (child->bs == child_bs) {
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (!child) {
>> +        error_setg(errp, "BDS %s is not a child of %s",
>> +                   bdrv_get_device_or_node_name(child_bs),
>> +                   bdrv_get_device_or_node_name(parent_bs));
>> +        return;
>> +    }
>> +
>> +    parent_bs->drv->bdrv_del_child(parent_bs, child_bs, errp);
> 
> How about we make this (BlockDriver.bdrv_del_child()) take a BdrvChild
> instead of a BDS? We could even make bdrv_del_child() as a whole take a
> BdrvChild parameter, but I don't suppose that would help much.

bdrv_add_child() takes a BDS, so I use BDS here.

Thanks
Wen Congyang

> 
> Max
> 
>> +}
>> diff --git a/include/block/block.h b/include/block/block.h
>> index ef67353..665c56f 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -616,4 +616,9 @@ void bdrv_flush_io_queue(BlockDriverState *bs);
>>  
>>  BlockAcctStats *bdrv_get_stats(BlockDriverState *bs);
>>  
>> +void bdrv_add_child(BlockDriverState *parent, BlockDriverState *child,
>> +                    Error **errp);
>> +void bdrv_del_child(BlockDriverState *parent, BlockDriverState *child,
>> +                    Error **errp);
>> +
>>  #endif
>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>> index 2f2c47b..64cbc55 100644
>> --- a/include/block/block_int.h
>> +++ b/include/block/block_int.h
>> @@ -288,6 +288,11 @@ struct BlockDriver {
>>       */
>>      int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo);
>>  
>> +    void (*bdrv_add_child)(BlockDriverState *parent, BlockDriverState 
>> *child,
>> +                           Error **errp);
>> +    void (*bdrv_del_child)(BlockDriverState *parent, BlockDriverState 
>> *child,
>> +                           Error **errp);
>> +
>>      QLIST_ENTRY(BlockDriver) list;
>>  };
>>  
>>
> 
>