linux-kernel - Re: [PATCH v2 5/6] mm: zswap: store incompressible page as-is

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Message-ID: <19ceab41-1537-4fbc-b75d-7a2f5c50c0f3@linux.dev>
Date: Tue, 16 Jul 2024 10:30:15 +0800
From: Chengming Zhou <chengming.zhou@...ux.dev>
To: Nhat Pham <nphamcs@...il.com>
Cc: Takero Funaki <flintglass@...il.com>, Johannes Weiner
 <hannes@...xchg.org>, Yosry Ahmed <yosryahmed@...gle.com>,
 Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
 Domenico Cerasuolo <cerasuolodomenico@...il.com>, linux-mm@...ck.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] mm: zswap: store incompressible page as-is

On 2024/7/13 06:47, Nhat Pham wrote:
> On Tue, Jul 9, 2024 at 6:26 AM Chengming Zhou <chengming.zhou@...ux.dev> wrote:
>>
>> On 2024/7/8 21:44, Takero Funaki wrote:
>>> 2024年7月8日(月) 12:56 Chengming Zhou <chengming.zhou@...ux.dev>:
>>>
>>>>>         comp_ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
>>>>>         dlen = acomp_ctx->req->dlen;
>>>>> -     if (comp_ret)
>>>>> +
>>>>> +     /* coa_compress returns -EINVAL for errors including insufficient dlen */
>>>>> +     if (comp_ret && comp_ret != -EINVAL)
>>>>>                 goto unlock;
>>>>
>>>> Seems we don't need to care about? "comp_ret" is useless anymore.
>>>>
>>>> Just:
>>>>
>>>> if (comp_ret || dlen > PAGE_SIZE - 64)
>>>>           dlen = PAGE_SIZE;
>>>>
>>>> And remove the checkings of comp_ret at the end.
>>>>
>>>
>>>>
>>>> We actually don't need to hold mutex if we are just copying folio.
>>>>
>>>> Thanks.
>>>>
>>>
>>> Thanks for reviewing.
>>>
>>> For comp_ret, can we consolidate all possible error codes as
>>> incompressible data?
>>
>> Maybe we still want these debug counters? I'm not sure.
> 
> I'm a bit torn, but ATM I have no strong opinions on these two error
> codes. If you do decide to consolidate these two, may I ask you to
> separate it into its own patch so that we can review + discuss it
> separately?

Yeah, I also have no strong opinions on these two error codes,
it's just ok to keep them.