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Date:   Fri, 5 Oct 2018 15:19:34 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc:     linux-mm@kvack.org, Catalin Marinas <catalin.marinas@arm.com>,
        Chris Zankel <chris@zankel.net>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Guan Xuetao <gxt@pku.edu.cn>, Ingo Molnar <mingo@redhat.com>,
        Matt Turner <mattst88@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Michal Hocko <mhocko@suse.com>,
        Michal Simek <monstr@monstr.eu>,
        Paul Burton <paul.burton@mips.com>,
        Richard Weinberger <richard@nod.at>,
        Russell King <linux@armlinux.org.uk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tony Luck <tony.luck@intel.com>, linux-alpha@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-m68k@vger.kernel.org,
        linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org,
        linux-um@lists.infradead.org
Subject: Re: [PATCH] memblock: stop using implicit alignement to
 SMP_CACHE_BYTES
Message-Id: <20181005151934.87226fa92825c3002a475413@linux-foundation.org>
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On Fri,  5 Oct 2018 00:07:04 +0300 Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:

> When a memblock allocation APIs are called with align = 0, the alignment is
> implicitly set to SMP_CACHE_BYTES.
> 
> Replace all such uses of memblock APIs with the 'align' parameter explicitly
> set to SMP_CACHE_BYTES and stop implicit alignment assignment in the
> memblock internal allocation functions.
> 
> For the case when memblock APIs are used via helper functions, e.g. like
> iommu_arena_new_node() in Alpha, the helper functions were detected with
> Coccinelle's help and then manually examined and updated where appropriate.
> 
> ...
>
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1298,9 +1298,6 @@ static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
>  {
>  	phys_addr_t found;
>  
> -	if (!align)
> -		align = SMP_CACHE_BYTES;
> -

Can we add a WARN_ON_ONCE(!align) here?  To catch unconverted code
which sneaks in later on.