linux-kernel - Re: [PATCH 2/6] x86: hv: hv_init.c: Replace alloc_page() with kmem_cache

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Message-ID: <87bm0csoyo.fsf@vitty.brq.redhat.com>
Date:   Wed, 08 May 2019 15:53:03 -0400
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Stephen Hemminger <sthemmin@...rosoft.com>,
        "m.maya.nakamura" <m.maya.nakamura@...il.com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "sashal\@kernel.org" <sashal@...nel.org>,
        "x86\@kernel.org" <x86@...nel.org>,
        "linux-hyperv\@vger.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] x86: hv: hv_init.c: Replace alloc_page() with kmem_cache_alloc()

Stephen Hemminger <sthemmin@...rosoft.com> writes:

> I would worry that kmem_cache_alloc does not currently have same alignment constraints.
> See discussion here:
> https://lwn.net/SubscriberLink/787740/a886fe4ea6681322/

I think it even was me who reported this bug with XFS originally :-) 

Yes, plain kmalloc() doesn't give you alignment guarantees (it is very
easy to prove, e.g. with CONFIG_KASAN), however, kmem_cache_create() (and
dma_pool_create() to that matter) has explicit 'align' parameter and it
is a bug if it is not respected.

-- 
Vitaly