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[209.85.221.46]) by smtp.gmail.com with ESMTPSA id g18sm3009273eje.12.2020.10.30.07.11.25 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Oct 2020 07:11:26 -0700 (PDT) Received: by mail-wr1-f46.google.com with SMTP id m13so6619931wrj.7 for ; Fri, 30 Oct 2020 07:11:25 -0700 (PDT) X-Received: by 2002:adf:e892:: with SMTP id d18mr3615109wrm.103.1604067085454; Fri, 30 Oct 2020 07:11:25 -0700 (PDT) MIME-Version: 1.0 References: <20201030100815.2269-1-daniel.vetter@ffwll.ch> <20201030100815.2269-6-daniel.vetter@ffwll.ch> In-Reply-To: <20201030100815.2269-6-daniel.vetter@ffwll.ch> From: Tomasz Figa Date: Fri, 30 Oct 2020 15:11:14 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM To: Daniel Vetter Cc: DRI Development , LKML , kvm , Linux MM , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , linux-samsung-soc , Linux Media Mailing List , Daniel Vetter , Jason Gunthorpe , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Mauro Carvalho Chehab , Andrew Morton , John Hubbard , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Dan Williams 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 Fri, Oct 30, 2020 at 11:08 AM Daniel Vetter wro= te: > > This is used by media/videbuf2 for persistent dma mappings, not just > for a single dma operation and then freed again, so needs > FOLL_LONGTERM. > > Unfortunately current pup_locked doesn't support FOLL_LONGTERM due to > locking issues. Rework the code to pull the pup path out from the > mmap_sem critical section as suggested by Jason. > > By relying entirely on the vma checks in pin_user_pages and follow_pfn > (for vm_flags and vma_is_fsdax) we can also streamline the code a lot. > > Signed-off-by: Daniel Vetter > Cc: Jason Gunthorpe > Cc: Pawel Osciak > Cc: Marek Szyprowski > Cc: Kyungmin Park > Cc: Tomasz Figa > Cc: Mauro Carvalho Chehab > Cc: Andrew Morton > Cc: John Hubbard > Cc: J=C3=A9r=C3=B4me Glisse > Cc: Jan Kara > Cc: Dan Williams > Cc: linux-mm@kvack.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-samsung-soc@vger.kernel.org > Cc: linux-media@vger.kernel.org > Signed-off-by: Daniel Vetter > -- > v2: Streamline the code and further simplify the loop checks (Jason) > > v5: Review from Tomasz: > - fix page counting for the follow_pfn case by resetting ret > - drop gup_flags paramater, now unused > --- > .../media/common/videobuf2/videobuf2-memops.c | 3 +- > include/linux/mm.h | 2 +- > mm/frame_vector.c | 53 ++++++------------- > 3 files changed, 19 insertions(+), 39 deletions(-) > Thanks, looks good to me now. Acked-by: Tomasz Figa >From reading the code, this is quite unlikely to introduce any behavior changes, but just to be safe, did you have a chance to test this with some V4L2 driver? Best regards, Tomasz > diff --git a/drivers/media/common/videobuf2/videobuf2-memops.c b/drivers/= media/common/videobuf2/videobuf2-memops.c > index 6e9e05153f4e..9dd6c27162f4 100644 > --- a/drivers/media/common/videobuf2/videobuf2-memops.c > +++ b/drivers/media/common/videobuf2/videobuf2-memops.c > @@ -40,7 +40,6 @@ struct frame_vector *vb2_create_framevec(unsigned long = start, > unsigned long first, last; > unsigned long nr; > struct frame_vector *vec; > - unsigned int flags =3D FOLL_FORCE | FOLL_WRITE; > > first =3D start >> PAGE_SHIFT; > last =3D (start + length - 1) >> PAGE_SHIFT; > @@ -48,7 +47,7 @@ struct frame_vector *vb2_create_framevec(unsigned long = start, > vec =3D frame_vector_create(nr); > if (!vec) > return ERR_PTR(-ENOMEM); > - ret =3D get_vaddr_frames(start & PAGE_MASK, nr, flags, vec); > + ret =3D get_vaddr_frames(start & PAGE_MASK, nr, vec); > if (ret < 0) > goto out_destroy; > /* We accept only complete set of PFNs */ > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ef360fe70aaf..d6b8e30dce2e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1765,7 +1765,7 @@ struct frame_vector { > struct frame_vector *frame_vector_create(unsigned int nr_frames); > void frame_vector_destroy(struct frame_vector *vec); > int get_vaddr_frames(unsigned long start, unsigned int nr_pfns, > - unsigned int gup_flags, struct frame_vector *vec); > + struct frame_vector *vec); > void put_vaddr_frames(struct frame_vector *vec); > int frame_vector_to_pages(struct frame_vector *vec); > void frame_vector_to_pfns(struct frame_vector *vec); > diff --git a/mm/frame_vector.c b/mm/frame_vector.c > index 10f82d5643b6..f8c34b895c76 100644 > --- a/mm/frame_vector.c > +++ b/mm/frame_vector.c > @@ -32,13 +32,12 @@ > * This function takes care of grabbing mmap_lock as necessary. > */ > int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > - unsigned int gup_flags, struct frame_vector *vec) > + struct frame_vector *vec) > { > struct mm_struct *mm =3D current->mm; > struct vm_area_struct *vma; > int ret =3D 0; > int err; > - int locked; > > if (nr_frames =3D=3D 0) > return 0; > @@ -48,40 +47,26 @@ int get_vaddr_frames(unsigned long start, unsigned in= t nr_frames, > > start =3D untagged_addr(start); > > - mmap_read_lock(mm); > - locked =3D 1; > - vma =3D find_vma_intersection(mm, start, start + 1); > - if (!vma) { > - ret =3D -EFAULT; > - goto out; > - } > - > - /* > - * While get_vaddr_frames() could be used for transient (kernel > - * controlled lifetime) pinning of memory pages all current > - * users establish long term (userspace controlled lifetime) > - * page pinning. Treat get_vaddr_frames() like > - * get_user_pages_longterm() and disallow it for filesystem-dax > - * mappings. > - */ > - if (vma_is_fsdax(vma)) { > - ret =3D -EOPNOTSUPP; > - goto out; > - } > - > - if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { > + ret =3D pin_user_pages_fast(start, nr_frames, > + FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM= , > + (struct page **)(vec->ptrs)); > + if (ret > 0) { > vec->got_ref =3D true; > vec->is_pfns =3D false; > - ret =3D pin_user_pages_locked(start, nr_frames, > - gup_flags, (struct page **)(vec->ptrs), &locked); > - goto out; > + goto out_unlocked; > } > > + mmap_read_lock(mm); > vec->got_ref =3D false; > vec->is_pfns =3D true; > + ret =3D 0; > do { > unsigned long *nums =3D frame_vector_pfns(vec); > > + vma =3D find_vma_intersection(mm, start, start + 1); > + if (!vma) > + break; > + > while (ret < nr_frames && start + PAGE_SIZE <=3D vma->vm_= end) { > err =3D follow_pfn(vma, start, &nums[ret]); > if (err) { > @@ -92,17 +77,13 @@ int get_vaddr_frames(unsigned long start, unsigned in= t nr_frames, > start +=3D PAGE_SIZE; > ret++; > } > - /* > - * We stop if we have enough pages or if VMA doesn't comp= letely > - * cover the tail page. > - */ > - if (ret >=3D nr_frames || start < vma->vm_end) > + /* Bail out if VMA doesn't completely cover the tail page= . */ > + if (start < vma->vm_end) > break; > - vma =3D find_vma_intersection(mm, start, start + 1); > - } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP)); > + } while (ret < nr_frames); > out: > - if (locked) > - mmap_read_unlock(mm); > + mmap_read_unlock(mm); > +out_unlocked: > if (!ret) > ret =3D -EFAULT; > if (ret > 0) > -- > 2.28.0 >