linux-kernel - RE: [PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

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Date:   Fri, 6 Oct 2017 11:10:14 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Pavel Tatashin' <pasha.tatashin@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        "borntraeger@...ibm.com" <borntraeger@...ibm.com>,
        "heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "willy@...radead.org" <willy@...radead.org>,
        "mhocko@...nel.org" <mhocko@...nel.org>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "sam@...nborg.org" <sam@...nborg.org>,
        "mgorman@...hsingularity.net" <mgorman@...hsingularity.net>,
        "steven.sistare@...cle.com" <steven.sistare@...cle.com>,
        "daniel.m.jordan@...cle.com" <daniel.m.jordan@...cle.com>,
        "bob.picco@...cle.com" <bob.picco@...cle.com>
Subject: RE: [PATCH v10 09/10] mm: stop zeroing memory during allocation in
 vmemmap

From: Pavel Tatashin
> Sent: 05 October 2017 22:11
> vmemmap_alloc_block() will no longer zero the block, so zero memory
> at its call sites for everything except struct pages.  Struct page memory
> is zero'd by struct page initialization.

It seems dangerous to change an allocator to stop zeroing memory.
It is probably saver to add a new function that doesn't zero
the memory and use that is the places where you don't want it
to be zeroed.

	David