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[209.85.220.65]) by mx.google.com with SMTPS id i130sor8239272oif.95.2019.01.29.10.41.35 for (Google Transport Security); Tue, 29 Jan 2019 10:41:35 -0800 (PST) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=C9iTEo72; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=HL83ygIqpSTTKGQg55ygGuyvC6iG0KJllUYn+t+L7fo=; b=C9iTEo72hAQPj1VLygRAYbRemfwQw/wdjdXDB3e/eclhA3asML1sVcibMctJEo6uvM UzOOCIoV4igwfhs+BOKVOb0NxKQHX2mLoe8zTN3ipepSsA7CJPAms4TelPvV+lEjs7NS pusDqWXYQz/xLw4ddjbankm+UWcc6n3w2WKfNtD2q98fMZLd/SmA2TGcs+1zSKGaGNbB Jw5Wu0qyfVYCB6sDA9JS9NCp+tKRnBCdViSIy6ksZVgWPNi+MGPcLByDcG16oUtSJCp6 GG09SsSyEVlXkjPiF7ZobCb6Pwh05ezDJtreAqFoLVpnb+I50qvxDtXBG+iI7KAoqZmr IxGg== X-Google-Smtp-Source: AHgI3IYljlwfixZbEW9k35QADvn426C06Y3dCzjYEAwUUk9JxY2Lr5SqZvdOmBetvdgd9kgxSjPcJbFa3Dw6Aldoo9c= X-Received: by 2002:aca:d905:: with SMTP id q5mr10434566oig.0.1548787294934; Tue, 29 Jan 2019 10:41:34 -0800 (PST) MIME-Version: 1.0 References: <20190129165428.3931-1-jglisse@redhat.com> <20190129165428.3931-10-jglisse@redhat.com> In-Reply-To: <20190129165428.3931-10-jglisse@redhat.com> From: Dan Williams Date: Tue, 29 Jan 2019 10:41:23 -0800 Message-ID: Subject: Re: [PATCH 09/10] mm/hmm: allow to mirror vma of a file on a DAX backed filesystem To: =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= Cc: Linux MM , Linux Kernel Mailing List , Andrew Morton , Ralph Campbell , John Hubbard , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Tue, Jan 29, 2019 at 8:54 AM wrote: > > From: J=C3=A9r=C3=B4me Glisse > > This add support to mirror vma which is an mmap of a file which is on > a filesystem that using a DAX block device. There is no reason not to > support that case. > The reason not to support it would be if it gets in the way of future DAX development. How does this interact with MAP_SYNC? I'm also concerned if this complicates DAX reflink support. In general I'd rather prioritize fixing the places where DAX is broken today before adding more cross-subsystem entanglements. The unit tests for filesystems (xfstests) are readily accessible. How would I go about regression testing DAX + HMM interactions? > Note that unlike GUP code we do not take page reference hence when we > back-off we have nothing to undo. > > Signed-off-by: J=C3=A9r=C3=B4me Glisse > Cc: Andrew Morton > Cc: Dan Williams > Cc: Ralph Campbell > Cc: John Hubbard > --- > mm/hmm.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 112 insertions(+), 21 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 8b87e1813313..1a444885404e 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -334,6 +334,7 @@ EXPORT_SYMBOL(hmm_mirror_unregister); > > struct hmm_vma_walk { > struct hmm_range *range; > + struct dev_pagemap *pgmap; > unsigned long last; > bool fault; > bool block; > @@ -508,6 +509,15 @@ static inline uint64_t pmd_to_hmm_pfn_flags(struct h= mm_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, > @@ -529,8 +539,19 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, > return hmm_vma_walk_hole_(addr, end, fault, write_fault, = walk); > > pfn =3D pmd_pfn(pmd) + pte_index(addr); > - for (i =3D 0; addr < end; addr +=3D PAGE_SIZE, i++, pfn++) > + for (i =3D 0; addr < end; addr +=3D PAGE_SIZE, i++, pfn++) { > + if (pmd_devmap(pmd)) { > + hmm_vma_walk->pgmap =3D get_dev_pagemap(pfn, > + hmm_vma_walk->pgmap); > + if (unlikely(!hmm_vma_walk->pgmap)) > + return -EBUSY; > + } > pfns[i] =3D hmm_pfn_from_pfn(range, pfn) | cpu_flags; > + } > + if (hmm_vma_walk->pgmap) { > + put_dev_pagemap(hmm_vma_walk->pgmap); > + hmm_vma_walk->pgmap =3D NULL; > + } > hmm_vma_walk->last =3D end; > return 0; > } > @@ -617,10 +638,24 @@ 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 =3D 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 =3D range->values[HMM_PFN_SPECIAL]; > + return -EFAULT; > + } > + > *pfn =3D 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 =3D NULL; > + } > pte_unmap(ptep); > /* Fault any virtual address we were asked to fault */ > return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); > @@ -708,12 +743,84 @@ 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 =3D NULL; > + } > pte_unmap(ptep - 1); > > hmm_vma_walk->last =3D addr; > return 0; > } > > +static int hmm_vma_walk_pud(pud_t *pudp, > + unsigned long start, > + unsigned long end, > + struct mm_walk *walk) > +{ > + struct hmm_vma_walk *hmm_vma_walk =3D walk->private; > + struct hmm_range *range =3D hmm_vma_walk->range; > + struct vm_area_struct *vma =3D walk->vma; > + unsigned long addr =3D start, next; > + pmd_t *pmdp; > + pud_t pud; > + int ret; > + > +again: > + pud =3D READ_ONCE(*pudp); > + if (pud_none(pud)) > + return hmm_vma_walk_hole(start, end, walk); > + > + if (pud_huge(pud) && pud_devmap(pud)) { > + unsigned long i, npages, pfn; > + uint64_t *pfns, cpu_flags; > + bool fault, write_fault; > + > + if (!pud_present(pud)) > + return hmm_vma_walk_hole(start, end, walk); > + > + i =3D (addr - range->start) >> PAGE_SHIFT; > + npages =3D (end - addr) >> PAGE_SHIFT; > + pfns =3D &range->pfns[i]; > + > + cpu_flags =3D pud_to_hmm_pfn_flags(range, pud); > + hmm_range_need_fault(hmm_vma_walk, pfns, npages, > + cpu_flags, &fault, &write_fault); > + if (fault || write_fault) > + return hmm_vma_walk_hole_(addr, end, fault, > + write_fault, walk); > + > + pfn =3D pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT)= ; > + for (i =3D 0; i < npages; ++i, ++pfn) { > + hmm_vma_walk->pgmap =3D get_dev_pagemap(pfn, > + hmm_vma_walk->pgmap); > + if (unlikely(!hmm_vma_walk->pgmap)) > + return -EBUSY; > + pfns[i] =3D hmm_pfn_from_pfn(range, pfn) | cpu_fl= ags; > + } > + if (hmm_vma_walk->pgmap) { > + put_dev_pagemap(hmm_vma_walk->pgmap); > + hmm_vma_walk->pgmap =3D NULL; > + } > + hmm_vma_walk->last =3D end; > + return 0; > + } > + > + split_huge_pud(vma, pudp, addr); > + if (pud_none(*pudp)) > + goto again; > + > + pmdp =3D pmd_offset(pudp, addr); > + do { > + next =3D pmd_addr_end(addr, end); > + ret =3D hmm_vma_walk_pmd(pmdp, addr, next, walk); > + if (ret) > + return ret; > + } while (pmdp++, addr =3D next, addr !=3D end); > + > + return 0; > +} > + > static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask, > unsigned long start, unsigned long = end, > struct mm_walk *walk) > @@ -786,14 +893,6 @@ static void hmm_pfns_clear(struct hmm_range *range, > *pfns =3D range->values[HMM_PFN_NONE]; > } > > -static void hmm_pfns_special(struct hmm_range *range) > -{ > - unsigned long addr =3D range->start, i =3D 0; > - > - for (; addr < range->end; addr +=3D PAGE_SIZE, i++) > - range->pfns[i] =3D range->values[HMM_PFN_SPECIAL]; > -} > - > /* > * hmm_range_register() - start tracking change to CPU page table over a= range > * @range: range > @@ -911,12 +1010,6 @@ long hmm_range_snapshot(struct hmm_range *range) > if (vma =3D=3D NULL || (vma->vm_flags & device_vma)) > return -EFAULT; > > - /* FIXME support dax */ > - if (vma_is_dax(vma)) { > - hmm_pfns_special(range); > - return -EINVAL; > - } > - > if (is_vm_hugetlb_page(vma)) { > struct hstate *h =3D hstate_vma(vma); > > @@ -940,6 +1033,7 @@ long hmm_range_snapshot(struct hmm_range *range) > } > > range->vma =3D vma; > + hmm_vma_walk.pgmap =3D NULL; > hmm_vma_walk.last =3D start; > hmm_vma_walk.fault =3D false; > hmm_vma_walk.range =3D range; > @@ -951,6 +1045,7 @@ long hmm_range_snapshot(struct hmm_range *range) > mm_walk.pte_entry =3D NULL; > mm_walk.test_walk =3D NULL; > mm_walk.hugetlb_entry =3D NULL; > + mm_walk.pud_entry =3D hmm_vma_walk_pud; > mm_walk.pmd_entry =3D hmm_vma_walk_pmd; > mm_walk.pte_hole =3D hmm_vma_walk_hole; > mm_walk.hugetlb_entry =3D hmm_vma_walk_hugetlb_entry; > @@ -1018,12 +1113,6 @@ long hmm_range_fault(struct hmm_range *range, bool= block) > if (vma =3D=3D NULL || (vma->vm_flags & device_vma)) > return -EFAULT; > > - /* FIXME support dax */ > - if (vma_is_dax(vma)) { > - hmm_pfns_special(range); > - return -EINVAL; > - } > - > if (is_vm_hugetlb_page(vma)) { > struct hstate *h =3D hstate_vma(vma); > > @@ -1047,6 +1136,7 @@ long hmm_range_fault(struct hmm_range *range, bool = block) > } > > range->vma =3D vma; > + hmm_vma_walk.pgmap =3D NULL; > hmm_vma_walk.last =3D start; > hmm_vma_walk.fault =3D true; > hmm_vma_walk.block =3D block; > @@ -1059,6 +1149,7 @@ long hmm_range_fault(struct hmm_range *range, bool = block) > mm_walk.pte_entry =3D NULL; > mm_walk.test_walk =3D NULL; > mm_walk.hugetlb_entry =3D NULL; > + mm_walk.pud_entry =3D hmm_vma_walk_pud; > mm_walk.pmd_entry =3D hmm_vma_walk_pmd; > mm_walk.pte_hole =3D hmm_vma_walk_hole; > mm_walk.hugetlb_entry =3D hmm_vma_walk_hugetlb_entry; > -- > 2.17.2 >