linux-kernel - Re: [PATCH kernel v2] powerpc/iommu: Do not call PageTransHuge() on tail pages

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Date:   Tue, 11 Apr 2017 18:20:18 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>, linuxppc-dev@...ts.ozlabs.org
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Greg Kurz <groug@...d.org>, Paul Mackerras <paulus@...ba.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org, #@...abs.ru,
        v4.9+@...abs.ru
Subject: Re: [PATCH kernel v2] powerpc/iommu: Do not call PageTransHuge() on
 tail pages

On Tue, 2017-04-11 at 17:54 +1000, Alexey Kardashevskiy wrote:
> The CMA pages migration code does not support compound pages at
> the moment so it performs few tests before proceeding to actual page
> migration.
> 
> One of the tests - PageTransHuge() - has VM_BUG_ON_PAGE(PageTail()) as
> it is designed to be called on head pages only. Since we also test for
> PageCompound(), and it contains PageTail() and PageHead(), we can
> simplify the check by leaving just PageCompound() and therefore avoid
> possible VM_BUG_ON_PAGE.
> 
> Fixes: 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate pinned pages out of CMA")
> Cc: stable@...r.kernel.org # v4.9+
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> Acked-by: Balbir Singh <bsingharora@...il.com>
> ---
> 
> Changes:
> v2:
> * instead of moving PageCompound() to the beginning, this just drops
> PageHuge() and PageTransHuge()
>

Looks good! My Acked-by is already present

Balbir Singh.