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Re: [lvm-devel] [PATCH] lvm2app: Add thin and thin pool lv creation V2



On 05/06/2013 08:26 AM, M. Mohan Kumar wrote:
> Tony Asleson <tasleson redhat com> writes:
> 
>> + *
>> + */
>> +lv_create_params_t lvm_lv_params_create_thin_pool(vg_t vg,
>> +		const char *pool_name, uint64_t size, uint32_t chunk_size,
>> +		uint64_t meta_size, lvm_thin_discards_t discard);
>> +
>> +#define lvm_lv_params_create_thin_pool_default(vg, pool_name, size) \
>> +			lvm_lv_params_create_thin_pool((vg), (pool_name), (size), 0, 0, \
>> +			LVM_THIN_DISCARDS_PASSDOWN)
>> +
>> +
>> +/**
>> + * Set the value of zero skip for the lv_create_params
>> + *
>> + * \param params
>> + * lv_create_prams to change
>> + *
>> + * \param skip
>> + * Value of skip zero to be set (0 == zero, 1 == skip zero)
>> + *
>> + * \return
>> + * 0 on success, else -1
>> + */
>> +int lvm_lv_params_skip_zero_set(lv_create_params_t params, int skip);
> 
> Are we going to provide as many helper functions to get/set parameters
> in lv_create_params structure? For example if an user does wants a new
> LV to be created in deactivation state, should we provide a helper
> something like this?
> 
> int lvm_lv_params_activation_set(lv_create_params_t params, int
> activate);
> 
> In this case lvm-api wont be flooded with lots of helper functions?
> Instead of individual helper function how about a common helper function
> to take care of this?
> 
> int lvm_lv_params_set(lv_create_params_t params, enum lv_create_param_type,
>                       type, void *data);
> 
> lvm_lv_params_set function will validate 'data' based on the
> lv_create_param_type and will return error if 'data' does not match
> given enum (resource)?
> 
> enum lv_create_param_type {
>      LV_CR_INVALID,
>      LV_CR_ZERO,
>      LV_CR_ACTIVATION,
> 
>      LV_CR_MAX_PARAM,
> };
> 
> In above zero case, this function will be invoked like this:
> 
> lvm_lv_params_set(params, LV_CR_ZERO, &zero);
> 
> lvm_lv_params_set will do:
>                   switch (type) {
>                   case LV_CR_ZERO:
>                      memcpy (&zero_skip, data, sizeof(int));
>                      break;
>                   case LV_CR_ACTIVATION:
>                        memcpy (&activation, data, sizeof(int));
>                        if (activation < CHANGE_AY && activation >
>                           CHANGE_AAY) {
>                           log_error();
>                           return -1;
>                        }
>                   }
> 
> 

Yeah, this is probably a better approach to minimize API explosion.  The
only thing I would like to add is a size_t data_len field.  This way we
can accommodate variable size data for same operation.

Does that sound reasonable?  I guess if we only support simple fixed
type sizes it would be redundant.

Thanks,
Tony


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