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[192.55.52.43]) by mx.google.com with ESMTPS id 140si667913pga.460.2019.03.28.19.05.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Mar 2019 19:05:33 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.43 as permitted sender) client-ip=192.55.52.43; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Mar 2019 19:05:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,282,1549958400"; d="scan'208";a="138333451" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga007.fm.intel.com with ESMTP; 28 Mar 2019 19:05:32 -0700 Date: Thu, 28 Mar 2019 11:04:26 -0700 From: Ira Weiny To: jglisse@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Dan Williams , John Hubbard , Arnd Bergmann Subject: Re: [PATCH v2 09/11] mm/hmm: allow to mirror vma of a file on a DAX backed filesystem v2 Message-ID: <20190328180425.GI31324@iweiny-DESK2.sc.intel.com> References: <20190325144011.10560-1-jglisse@redhat.com> <20190325144011.10560-10-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190325144011.10560-10-jglisse@redhat.com> User-Agent: Mutt/1.11.1 (2018-12-01) 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 Mon, Mar 25, 2019 at 10:40:09AM -0400, Jerome Glisse wrote: > From: Jérôme Glisse > > HMM mirror is a device driver helpers to mirror range of virtual address. > It means that the process jobs running on the device can access the same > virtual address as the CPU threads of that process. This patch adds support > for mirroring mapping of file that are on a DAX block device (ie range of > virtual address that is an mmap of a file in a filesystem on a DAX block > device). There is no reason to not support such case when mirroring virtual > address on a device. > > Note that unlike GUP code we do not take page reference hence when we > back-off we have nothing to undo. > > Changes since v1: > - improved commit message > - squashed: Arnd Bergmann: fix unused variable warning in hmm_vma_walk_pud > > Signed-off-by: Jérôme Glisse > Reviewed-by: Ralph Campbell > Cc: Andrew Morton > Cc: Dan Williams > Cc: John Hubbard > Cc: Arnd Bergmann > --- > mm/hmm.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 111 insertions(+), 21 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 64a33770813b..ce33151c6832 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -325,6 +325,7 @@ EXPORT_SYMBOL(hmm_mirror_unregister); > > struct hmm_vma_walk { > struct hmm_range *range; > + struct dev_pagemap *pgmap; > unsigned long last; > bool fault; > bool block; > @@ -499,6 +500,15 @@ static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd) > range->flags[HMM_PFN_VALID]; > } > > +static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud) > +{ > + if (!pud_present(pud)) > + return 0; > + return pud_write(pud) ? range->flags[HMM_PFN_VALID] | > + range->flags[HMM_PFN_WRITE] : > + range->flags[HMM_PFN_VALID]; > +} > + > static int hmm_vma_handle_pmd(struct mm_walk *walk, > unsigned long addr, > unsigned long end, > @@ -520,8 +530,19 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, > return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); > > pfn = pmd_pfn(pmd) + pte_index(addr); > - for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) > + for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) { > + if (pmd_devmap(pmd)) { > + hmm_vma_walk->pgmap = get_dev_pagemap(pfn, > + hmm_vma_walk->pgmap); > + if (unlikely(!hmm_vma_walk->pgmap)) > + return -EBUSY; > + } > pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags; > + } > + if (hmm_vma_walk->pgmap) { > + put_dev_pagemap(hmm_vma_walk->pgmap); > + hmm_vma_walk->pgmap = NULL; > + } > hmm_vma_walk->last = end; > return 0; > } > @@ -608,10 +629,24 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, > if (fault || write_fault) > goto fault; > > + if (pte_devmap(pte)) { > + hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte), > + hmm_vma_walk->pgmap); > + if (unlikely(!hmm_vma_walk->pgmap)) > + return -EBUSY; > + } else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) { > + *pfn = range->values[HMM_PFN_SPECIAL]; > + return -EFAULT; > + } > + > *pfn = hmm_pfn_from_pfn(range, pte_pfn(pte)) | cpu_flags; > return 0; > > fault: > + if (hmm_vma_walk->pgmap) { > + put_dev_pagemap(hmm_vma_walk->pgmap); > + hmm_vma_walk->pgmap = NULL; > + } > pte_unmap(ptep); > /* Fault any virtual address we were asked to fault */ > return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); > @@ -699,12 +734,83 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, > return r; > } > } > + if (hmm_vma_walk->pgmap) { > + put_dev_pagemap(hmm_vma_walk->pgmap); > + hmm_vma_walk->pgmap = NULL; > + } Why is this here and not in hmm_vma_handle_pte()? Unless I'm just getting tired this is the corresponding put when hmm_vma_handle_pte() returns 0 above at above. Ira