Re: [PATCH v3 28/49] dm zoned: dynamically allocate the dm-zoned-meta shrinker

[Damien Le Moal <dlemoal@xxxxxxxxxx>]

On 7/27/23 17:55, Qi Zheng wrote:
>>>           goto err;
>>>       }
>>>   +    zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count;
>>> +    zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan;
>>> +    zmd->mblk_shrinker->seeks = DEFAULT_SEEKS;
>>> +    zmd->mblk_shrinker->private_data = zmd;
>>> +
>>> +    shrinker_register(zmd->mblk_shrinker);
>>
>> I fail to see how this new shrinker API is better... Why isn't there a
>> shrinker_alloc_and_register() function ? That would avoid adding all this 
>> code
>> all over the place as the new API call would be very similar to the current
>> shrinker_register() call with static allocation.
> 
> In some registration scenarios, memory needs to be allocated in advance.
> So we continue to use the previous prealloc/register_prepared()
> algorithm. The shrinker_alloc_and_register() is just a helper function
> that combines the two, and this increases the number of APIs that
> shrinker exposes to the outside, so I choose not to add this helper.

And that results in more code in many places instead of less code + a simple
inline helper in the shrinker header file... So not adding that super simple
helper is not exactly the best choice in my opinion.

-- 
Damien Le Moal
Western Digital Research