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[195.135.220.15]) by mx.google.com with ESMTPS id 41si161333edr.20.2019.02.28.01.40.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 01:40:13 -0800 (PST) Received-SPF: pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1AC1DAD36; Thu, 28 Feb 2019 09:40:12 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 764DB1E4263; Thu, 28 Feb 2019 10:40:11 +0100 (CET) Date: Thu, 28 Feb 2019 10:40:11 +0100 From: Jan Kara To: "Aneesh Kumar K.V" Cc: akpm@linux-foundation.org, "Kirill A . Shutemov" , Jan Kara , mpe@ellerman.id.au, Ross Zwisler , Oliver O'Halloran , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Dan Williams Subject: Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default Message-ID: <20190228094011.GB22210@quack2.suse.cz> References: <20190228083522.8189-1-aneesh.kumar@linux.ibm.com> <20190228083522.8189-2-aneesh.kumar@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190228083522.8189-2-aneesh.kumar@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 28-02-19 14:05:22, Aneesh Kumar K.V wrote: > Add a flag to indicate the ability to do huge page dax mapping. On architecture > like ppc64, the hypervisor can disable huge page support in the guest. In > such a case, we should not enable huge page dax mapping. This patch adds > a flag which the architecture code will update to indicate huge page > dax mapping support. > > Architectures mostly do transparent_hugepage_flag = 0; if they can't > do hugepages. That also takes care of disabling dax hugepage mapping > with this change. > > Without this patch we get the below error with kvm on ppc64. > > [ 118.849975] lpar: Failed hash pte insert with error -4 > > NOTE: The patch also use > > echo never > /sys/kernel/mm/transparent_hugepage/enabled > to disable dax huge page mapping. > > Signed-off-by: Aneesh Kumar K.V Added Dan to CC for opinion. I kind of fail to see why you don't use TRANSPARENT_HUGEPAGE_FLAG for this. I know that technically DAX huge pages and normal THPs are different things but so far we've tried to avoid making that distinction visible to userspace. Honza > --- > TODO: > * Add Fixes: tag > > include/linux/huge_mm.h | 4 +++- > mm/huge_memory.c | 4 ++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 381e872bfde0..01ad5258545e 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -53,6 +53,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, > pud_t *pud, pfn_t pfn, bool write); > enum transparent_hugepage_flag { > TRANSPARENT_HUGEPAGE_FLAG, > + TRANSPARENT_HUGEPAGE_DAX_FLAG, > TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, > TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, > @@ -111,7 +112,8 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) > if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG)) > return true; > > - if (vma_is_dax(vma)) > + if (vma_is_dax(vma) && > + (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_DAX_FLAG))) > return true; > > if (transparent_hugepage_flags & > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index faf357eaf0ce..43d742fe0341 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -53,6 +53,7 @@ unsigned long transparent_hugepage_flags __read_mostly = > #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE > (1< #endif > + (1 << TRANSPARENT_HUGEPAGE_DAX_FLAG) | > (1< (1< (1< @@ -475,6 +476,8 @@ static int __init setup_transparent_hugepage(char *str) > &transparent_hugepage_flags); > clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > &transparent_hugepage_flags); > + clear_bit(TRANSPARENT_HUGEPAGE_DAX_FLAG, > + &transparent_hugepage_flags); > ret = 1; > } > out: > @@ -753,6 +756,7 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, > spinlock_t *ptl; > > ptl = pmd_lock(mm, pmd); > + /* should we check for none here again? */ > entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); > if (pfn_t_devmap(pfn)) > entry = pmd_mkdevmap(entry); > -- > 2.20.1 > -- Jan Kara SUSE Labs, CR