linux-kernel - Re: [PATCH] memblock: stop using implicit alignement to SMP_CACHE

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Date:   Fri, 05 Oct 2018 13:25:38 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Mike Rapoport <rppt@...ux.vnet.ibm.com>, linux-mm@...ck.org
Cc:     linux-mips@...ux-mips.org, Michal Hocko <mhocko@...e.com>,
        linux-ia64@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Richard Weinberger <richard@....at>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Matt Turner <mattst88@...il.com>, linux-um@...ts.infradead.org,
        linux-m68k@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Guan Xuetao <gxt@....edu.cn>,
        linux-arm-kernel@...ts.infradead.org,
        Chris Zankel <chris@...kel.net>,
        Michal Simek <monstr@...str.eu>,
        Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        Paul Burton <paul.burton@...s.com>,
        linux-alpha@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] memblock: stop using implicit alignement to
 SMP_CACHE_BYTES

On Fri, 2018-10-05 at 00:07 +0300, Mike Rapoport 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.
> 
> The direct memblock APIs users were updated using the semantic patch below:

What is the purpose of this ? It sounds rather counter-intuitive...

Ben.