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

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Message-ID: <20220531081412.22db88cc@kernel.org>
Date:   Tue, 31 May 2022 08:14:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Chen Lin <chen45464546@....com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, alexander.duyck@...il.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2] mm: page_frag: Warn_on when frag_alloc size is
 bigger than PAGE_SIZE

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.