linux-kernel - Re: [PATCH 04/31] kasan, page_alloc: simplify kasan_poison

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Date:   Mon, 6 Dec 2021 22:07:50 +0100
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     andrey.konovalov@...ux.dev,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Evgenii Stepanov <eugenis@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 04/31] kasan, page_alloc: simplify kasan_poison_pages call site

On Wed, Dec 1, 2021 at 3:10 PM Marco Elver <elver@...gle.com> wrote:
>
> On Tue, Nov 30, 2021 at 10:39PM +0100, andrey.konovalov@...ux.dev wrote:
> > From: Andrey Konovalov <andreyknvl@...gle.com>
> >
> > Simplify the code around calling kasan_poison_pages() in
> > free_pages_prepare().
> >
> > Reording kasan_poison_pages() and kernel_init_free_pages() is OK,
> > since kernel_init_free_pages() can handle poisoned memory.
>
> Why did they have to be reordered?

It's for the next patch, I'll move the reordering there in v2.

> > This patch does no functional changes besides reordering the calls.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > ---
> >  mm/page_alloc.c | 18 +++++-------------
> >  1 file changed, 5 insertions(+), 13 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 3f3ea41f8c64..0673db27dd12 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1289,6 +1289,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
> >  {
> >       int bad = 0;
> >       bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);
>
> skip_kasan_poison is only used once now, so you could remove the
> variable -- unless later code will use it in more than once place again.

Will do in v2.

Thanks!