netdev - Re:Re: [PATCH v2] mm: page_frag: Warn_on when frag_alloc size is bigger than PAGE

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Date:   Tue, 31 May 2022 23:36:22 +0800
From:   Chen Lin <chen45464546@....com>
To:     kuba@...nel.org
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, alexander.duyck@...il.com,
        netdev@...r.kernel.org, Chen Lin <chen45464546@....com>
Subject: Re:Re: [PATCH v2] mm: page_frag: Warn_on when frag_alloc size is bigger than PAGE_SIZE

At 2022-05-31 22:14:12, "Jakub Kicinski" <kuba@...nel.org> wrote:
>On Tue, 31 May 2022 22:41:12 +0800 Chen Lin wrote:
>> At 2022-05-31 02:29:18, "Jakub Kicinski" <kuba@...nel.org> wrote:
>> >Oh, well, the reuse also needs an update. We can slap a similar
>> >condition next to the pfmemalloc check.  
>> 
>> The sample code above cannot completely solve the current problem.
>> For example, when fragsz is greater than PAGE_FRAG_CACHE_MAX_SIZE(32768),
>> __page_frag_cache_refill will return a memory of only 32768 bytes, so 
>> should we continue to expand the PAGE_FRAG_CACHE_MAX_SIZE? Maybe more 
>> work needs to be done
>
>Right, but I can think of two drivers off the top of my head which will
>allocate <=32k frags but none which will allocate more.

In fact, it is rare to apply for more than one page, so is it necessary to 
change it to support? 
we can just warning and return, also it is easy to synchronize this simple 
protective measures to lower Linux versions.