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Message-ID: <cc819e13-cb25-ddaa-e0e3-7328f5ea3a4f@bytedance.com>
Date:   Thu, 27 Jul 2023 18:32:10 +0800
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Subject: Re: [PATCH v3 28/49] dm zoned: dynamically allocate the dm-zoned-meta
 shrinker
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To:     Damien Le Moal <dlemoal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
        kvm@vger.kernel.org, xen-devel@lists.xenproject.org,
        linux-erofs@lists.ozlabs.org,
        linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
        linux-nfs@vger.kernel.org, linux-mtd@lists.infradead.org,
        rcu@vger.kernel.org, netdev@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
        dm-devel@redhat.com, linux-raid@vger.kernel.org,
        linux-bcache@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org,
        Muchun Song <songmuchun@bytedance.com>,
        akpm@linux-foundation.org, david@fromorbit.com, tkhai@ya.ru,
        vbabka@suse.cz, roman.gushchin@linux.dev, djwong@kernel.org,
        brauner@kernel.org, paulmck@kernel.org, tytso@mit.edu,
        steven.price@arm.com, cel@kernel.org, senozhatsky@chromium.org,
        yujie.liu@intel.com, gregkh@linuxfoundation.org,
        muchun.song@linux.dev
References: <20230727080502.77895-1-zhengqi.arch@bytedance.com>
 <20230727080502.77895-29-zhengqi.arch@bytedance.com>
 <baaf7de4-9a0e-b953-2b6a-46e60c415614@kernel.org>
 <56ee1d92-28ee-81cb-9c41-6ca7ea6556b0@bytedance.com>
 <ba0868b2-9f90-3d81-1c91-8810057fb3ce@kernel.org>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
In-Reply-To: <ba0868b2-9f90-3d81-1c91-8810057fb3ce@kernel.org>
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On 2023/7/27 18:20, Damien Le Moal wrote:
> 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

It also needs to be exported to the driver for use.

> helper is not exactly the best choice in my opinion.

Hm, either one is fine for me. If no one else objects, I can add this
helper. ;)

>