linux-kernel - Re: [PATCH] mm: extend max struct page size for kmsan

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Date:   Mon, 30 Jan 2023 12:19:58 -0500
From:   Pasha Tatashin <pasha.tatashin@...een.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        Alexander Potapenko <glider@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Hugh Dickins <hughd@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alex Sierra <alex.sierra@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: extend max struct page size for kmsan

On Mon, Jan 30, 2023 at 8:07 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> After x86 has enabled support for KMSAN, it has become possible
> to have larger 'struct page' than was expected when commit
> 5470dea49f53 ("mm: use mm_zero_struct_page from SPARC on all 64b
> architectures") was merged:
>
> include/linux/mm.h:156:10: warning: no case matching constant switch condition '96'
>         switch (sizeof(struct page)) {
>
> Extend the maximum accordingly.
>
> Fixes: 5470dea49f53 ("mm: use mm_zero_struct_page from SPARC on all 64b architectures")

No need to add the above "Fixes:". The above patch works as expected
everywhere where the struct page is 80 bytes or smaller (as specified
by the comment).

I also agree with others that the KMSAN should be part of page_ext
instead of increasing the complexity of "struct page".

Otherwise,
Reviewed-by: Pasha Tatashin <pasha.tatashin@...een.com>

Thanks,
Pasha