linux-kernel - Re: [PATCH 1/2] mm: fix logic error of page_expected

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Date:   Wed, 14 Sep 2022 16:14:29 +0800
From:   Zhaoyang Huang <huangzhaoyang@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, Ke Wang <ke.wang@...soc.com>
Subject: Re: [PATCH 1/2] mm: fix logic error of page_expected_state

On Wed, Sep 14, 2022 at 3:35 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Wed, Sep 14, 2022 at 11:37:00AM +0800, zhaoyang.huang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> >
> > The page with special page type will be deemed as bad page wrongly since
> > type share the same address with mapcount.
>
> That's not wrongly.  You didn't clear the bit.  I told you you would
> need to do that in the first version of the patch you sent.
Yes, I have cleared the PG_trackleak since v2 as you suggested.
However, IMHO, the page which has page type should be skipped for
mapcount check. The present problem is there is no invoking of
free_pages_prepare within the chain of
drain_pages_zone->free_pcppages_bulk, special pages with
page->type(PG_guard and PG_trackleak etc) will be leaked as
bulkfree_pcp_prepare will deem it as bad by checking the mapcount.