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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Wed, 11 Nov 2020 10:33:29 +0100
Message-ID: <CAK8P3a2vKOb_R3_tqO_XVCCn5Si2jFA5DRe_spB2-+gsoDhO6g@mail.gmail.com>
Subject: Re: [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Stefan Agner <stefan@agner.ch>, Minchan Kim <minchan@kernel.org>,
        ngupta@vflare.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        sjenning@linux.vnet.ibm.com, gregkh <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>, Linux-MM <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Nov 10, 2020 at 5:21 PM Mike Rapoport <rppt@kernel.org> wrote:
> On Tue, Nov 10, 2020 at 12:21:11PM +0100, Arnd Bergmann wrote:
> >
> > To be on the safe side, we could provoke a compile-time error
> > when CONFIG_PHYS_ADDR_T_64BIT is set on a 32-bit
> > architecture, but MAX_POSSIBLE_PHYSMEM_BITS is not set.
>
> Maybe compile time warning and a runtime error in zs_init() if 32 bit
> machine has memory above 4G?

If the fix is as easy as adding a single line in a header, I think a
compile-time
error makes it easier, no need to wait for someone to boot a broken
system before fixing it.

       Arnd