linux-kernel - Re: [PATCH v5 3/4] mm: support large folios swapin as a whole for zRAM-like swapfile

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Message-ID: <CANzGp4J3et+yo8v8iDngvAb3nrn-gSDh0_j0=65OEiw9jKJbPQ@mail.gmail.com>
Date: Mon, 29 Jul 2024 14:36:38 +0800
From: Chuanhua Han <chuanhuahan@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org, linux-mm@...ck.org, 
	ying.huang@...el.com, baolin.wang@...ux.alibaba.com, chrisl@...nel.org, 
	david@...hat.com, hannes@...xchg.org, hughd@...gle.com, 
	kaleshsingh@...gle.com, kasong@...cent.com, linux-kernel@...r.kernel.org, 
	mhocko@...e.com, minchan@...nel.org, nphamcs@...il.com, ryan.roberts@....com, 
	senozhatsky@...omium.org, shakeel.butt@...ux.dev, shy828301@...il.com, 
	surenb@...gle.com, v-songbaohua@...o.com, xiang@...nel.org, 
	yosryahmed@...gle.com, Chuanhua Han <hanchuanhua@...o.com>
Subject: Re: [PATCH v5 3/4] mm: support large folios swapin as a whole for
 zRAM-like swapfile

Matthew Wilcox <willy@...radead.org> 于2024年7月29日周一 11:51写道：
>
> On Fri, Jul 26, 2024 at 09:46:17PM +1200, Barry Song wrote:
> > -                     folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0,
> > -                                             vma, vmf->address, false);
> > +                     folio = alloc_swap_folio(vmf);
> >                       page = &folio->page;
>
> This is no longer correct.  You need to set 'page' to the precise page
> that is being faulted rather than the first page of the folio.  It was
> fine before because it always allocated a single-page folio, but now it
> must use folio_page() or folio_file_page() (whichever has the correct
> semantics for you).
>
> Also you need to fix your test suite to notice this bug.  I suggest
> doing that first so that you know whether you've got the calculation
> correct.

>
>
This is no problem now, we support large folios swapin as a whole, so
the head page is used here instead of the page that is being faulted.
You can also refer to the current code context, now support large
folios swapin as a whole, and previously only support small page
swapin is not the same.

-- 
Thanks,
Chuanhua