linux-kernel - Re: [PATCH] mm: page_alloc: ignore init_on

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Message-ID: <CA+fCnZcZvBT97y3zEatnTvi+RBW5bCrQRim9uK6wobYQOdgNhg@mail.gmail.com>
Date:   Tue, 30 Mar 2021 00:00:49 +0200
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     David Hildenbrand <david@...hat.com>,
        Sergei Trofimovich <slyfox@...too.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: ignore init_on_free=1 for page alloc

On Mon, Mar 29, 2021 at 2:10 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> > commit 855a9c4018f3219db8be7e4b9a65ab22aebfde82
> > Author: Andrey Konovalov <andreyknvl@...il.com>
> > Date:   Thu Mar 18 17:01:40 2021 +1100
> >
> >     kasan, mm: integrate page_alloc init with HW_TAGS
>
> But the mmotm patch/-next commit also changes post_alloc_hook()
>
> Before the patch it was:
> kernel_unpoison_pages(page, 1 << order);
> ...
> kernel_init_free_pages(page, 1 << order);
>
> Now it is (for !kasan_has_integrated_init()):
>
> kernel_init_free_pages(page, 1 << order);
>
> kernel_unpoison_pages(page, 1 << order);
>
> That has to be wrong, because we init the page with zeroes and then call
> kernel_unpoison_pages() which checks for the 0xaa pattern. Andrey?

It's similar to free_pages_prepare(): kernel_unpoison_pages() and
want_init_on_alloc() are exclusive, so the order shouldn't matter. Am
I missing something?